Patent Application
20140170667
The invention generally relates to methods for amplifying nucleic acid from a target.
Blood-borne pathogens are a significant healthcare problem. A delayed or improper diagnosis of a bacterial infection can result in sepsis, a serious, and often deadly, inflammatory response to the infection. Sepsis is the 10th leading cause of death in the United States. Early detection of bacterial infections in blood is the key to preventing the onset of sepsis. Traditional methods of detection and identification of blood-borne infection include blood culture and antibiotic susceptibility assays. Those methods typically require culturing cells, which can be expensive and can take as long as 72 hours. Often, septic shock will occur before cell culture results can be obtained.
Alternative methods for detection of pathogens, particularly bacteria, have been described by others. Those methods include molecular detection methods, such as hybrid capture or polymerase chain reaction (PCR), which identify the pathogen from a sample by analyzing the nucleic acid from the pathogen. For PCR, a high starting concentration of purified nucleic acid is required. A general workflow to obtain the purified pathogen nucleic acid for the PCR reaction involves isolating pathogens from a biological sample, such as blood or urine, and lysing the isolated pathogen to release the pathogen nucleic acid. The lysis results in a mixture that includes free pathogen nucleic acid and debris from the lysed cells. That mixture is purified, e.g., by running the mixture through a column that retains the nucleic acid while allowing the lysis debris to flow through the column. The retained nucleic acid is then eluted from the column and the purified pathogen nucleic acid is subjected to PCR amplification.
A problem with nucleic acid purification processes is that pathogen nucleic acid is lost during the process. For example, a certain amount of pathogen nucleic acid becomes degraded immediately after lysis due to its exposure to nucleases present in the lysis mixture. Such degraded nucleic acid cannot be PCR amplified. Additionally, a certain amount of pathogen nucleic acid fails to bind to the column, instead flowing through the column and being discarded with the debris from the lysis procedure. Further, a certain amount of pathogen nucleic acid is lost by being retained in the column after the elusion step. If enough pathogen nucleic acid is lost during the purification process, there is an insufficient amount of purified pathogen nucleic acid for conducting the PCR reaction.
The invention provides methods that amplify nucleic acid from a target without the need for first purifying the isolated nucleic acid. Methods of the invention are accomplished by introducing amplification reagents (e.g., primers, nucleotide triphosphates, polymerases, metal ions, buffers, etc.) into a sample vessel including an isolated intact target. A lysis procedure is conducted in the presence of the amplification reagents, such that nucleic acid released from the lysed target is immediately exposed to the amplification reagents and an amplification reaction is conducted on the lysed target nucleic acid in the presence of the debris from the lysis procedure. Accordingly, all of the lysed nucleic acid is available to participate in the amplification reaction, and methods of the invention avoid nucleic acid loss that occurs using standard purification techniques. Additionally, nucleic acid degradation is avoided because the heat from the amplification reaction denatures/inactivates nucleases that cause nucleic acid degradation.
A sample may be obtained by any method known in the art, and any type of sample may be used with methods of the invention. The sample may be a biological sample, such as a mammalian tissue or body fluid and is preferably a human tissue or body fluid. Methods of the invention may be used with any body fluid. Exemplary body fluids include blood, sputum, serum, plasma, urine, saliva, sweat, and cerebral spinal fluid. In particularly embodiments, the sample is a human blood or urine sample. The sample may also be a food sample or an environmental sample. The target analyte refers to the target that will be captured and isolated by methods of the invention. The target may be bacteria, fungi, a cell, a virus, or any molecule that contains nucleic acid. In certain embodiments, the target is a pathogenic bacteria. In other embodiments, the target is a gram positive or gram negative bacteria. Exemplary bacterial species that may be captured and isolated by methods of the invention include E. coli, Listeria, Clostridium, Mycobacterium, Shigella, Borrelia, Campylobacter, Bacillus, Salmonella, Staphylococcus, Enterococcus, Pneumococcus, Streptococcus, and a combination thereof.
Any assay known in the art may be used to capture/isolate the target from the sample. In certain embodiments, the assay uses magnetic particles and the assay involves introducing magnetic particles including a target-specific binding moiety to the sample in order to create a mixture, incubating the mixture to allow the particles to bind to the target in the sample, and applying a magnetic field to isolate target/magnetic particle complexes from the sample. The target-specific binding moiety will depend on the target to be captured. The moiety may be any capture moiety known in the art, such as an antibody, an aptamer, a nucleic acid, a protein, a receptor, a lectin, a phage or a ligand. In particular embodiments, the target-specific binding moiety is a lectin or an antibody. In certain embodiments, the antibody is specific for bacteria. In other embodiments, the antibody is specific for fungi.
In some embodiments of the invention, a target capture system may be employed. The target capture system allows for rapid isolation of a target analyte from a sample without the need for sample preparation or extensive manual operation. The target capture system concentrates essentially all of a clinically relevant portion of a sample (less than 1 mL) from an initial sample volume of about 10 mL. The ability to isolate small, clinically relevant, volumes of sample improves the efficiency in which nucleic acids can be extracted from a target for subsequent analysis.
The target capture systems generally include a cartridge and an instrument. The cartridge includes components such as channels, mixing chambers, and traps to process the sample for target isolation. The cartridge may interface with an instrument having one or more assemblies, such as mechanical, magnetic, pneumatic, and fluidic assemblies, that interact with the cartridge to assist/drive the processes performed on the cartridge. The target capture systems are integrated to perform several processes on a sample inputted into the cartridge to achieve a final result without user manipulation. The final result can be capture of live/whole target cells or isolation of nucleic acids from target cells within the sample.
In certain aspects, the processes performed by the target capture system include introducing a plurality of magnetic particles, in which a plurality of the particles include at least one captured moiety specific to a target, into a sample to form a mixture that includes sample and particles. The mixture is incubated to form at least one target/particle complex and a magnetic field is applied to isolate the magnetic particle/target complexes from the sample. The process starts at inputting a sample and ends at delivering a capture target (or nucleic acids of the target) into a container for further analysis.
Cartridges can include a chamber for holding and releasing the magnetic particles into a sample to form a mixture and at least one magnetic trap for receiving the sample/magnetic particle mixture. The magnetic trap engages with a magnetic assembly to isolate the magnetic particles from the sample. In certain embodiments, the cartridge includes a first magnetic trap in communication with a second magnetic trap, in which both magnetic traps engage with a magnetic assembly to isolate magnetic particles from a sample. In one embodiment, the first magnetic trap isolates magnetic particles from the sample and the isolated magnetic particles are then transferred through the second magnetic trap. The second magnetic trap engages with a second magnetic assembly to isolate the plurality of magnetic particles from the first magnetic trap. A lysing mechanism operably associated with the second magnetic trap can be used to lyse at least one target cell bound to at least one of the magnetic particles within the second magnetic trap. The cartridge may further include a matrix for receiving lysate from the first magnetic trap and retaining nucleic acid from the lysate. In one embodiment, the matrix is an affinity column. The cartridge can further include a reaction chamber, such as a bubble mixer, in communication with the matrix for pre-treating the lysate.
The isolation assay of the present invention may be performed with any type of magnetic particle. Magnetic particles generally fall into two broad categories. The first category includes particles that are permanently magnetizable, or ferromagnetic; and the second category includes particles that demonstrate bulk magnetic behavior only when subjected to a magnetic field. The latter are referred to as magnetically responsive particles. Materials displaying magnetically responsive behavior are sometimes described as superparamagnetic. However, materials exhibiting bulk ferromagnetic properties, e.g., magnetic iron oxide, may be characterized as superparamagnetic when provided in crystals of about 30 nm or less in diameter. Larger crystals of ferromagnetic materials, by contrast, retain permanent magnet characteristics after exposure to a magnetic field and tend to aggregate thereafter due to strong particle-particle interaction. In certain embodiments, the particles are superparamagnetic beads. In other embodiments, the magnetic particles include at least 70% superparamagnetic beads by weight. In certain embodiments, the superparamagnetic beads are from about 100 nm to about 250 nm in diameter. In certain embodiments, the magnetic particle is an iron-containing magnetic particle. In other embodiments, the magnetic particle includes iron oxide or iron platinum. In certain embodiments, the incubating step includes incubating the mixture in a buffer that inhibits cell lysis. In certain embodiments, the buffer includes Tris(hydroximethyl)-aminomethane hydrochloride at a concentration of between about 50 mM and about 100 mM, preferably about 75 mM. In other embodiments, methods of the invention further include retaining the magnetic particles in a magnetic field during the washing step.
Once the target is isolated, reagents from an amplification reaction are added to the isolated target, the target is lysed to release nucleic acid from within the target, and the released nucleic acid is amplified in the presence of the debris (e.g., cellular components such as proteins and lipids) from the lysis. Any method known in the art may be used to lyse the target. Exemplary methods include mechanical methods, thermal methods, enzymatic methods, chemical methods, or a combination thereof. The lysis and the amplification reaction can occur simultaneously or sequentially and will depend on the lysis method employed. In particular embodiments, the target is lysed using thermal methods. Application of heat not only lyses the target, it also denatures the released double stranded nucleic acid into single stranded nucleic acid and initiates the amplification reaction. Another advantage of thermal lysis is that the heat facilitates denaturation/inactivation of nucleases that can cause degradation of nucleic acid.
Any amplification reaction known in the art may be conducted on the released nucleic acid. Exemplary amplification techniques include polymerase chain reaction (PCR), reverse transcription-PCR, real-time PCR, quantitative real-time PCR, digital PCR (dPCR), digital emulsion PCR (dePCR), clonal PCR, amplified fragment length polymorphism PCR (AFLP PCR), allele specific PCR, assembly PCR, asymmetric PCR (in which a great excess of primers for a chosen strand is used), colony PCR, helicase-dependent amplification (HDA), Hot Start PCR, inverse PCR (IPCR), in situ PCR, long PCR (extension of DNA greater than about 5 kilobases), multiplex PCR, nested PCR (uses more than one pair of primers), single-cell PCR, touchdown PCR, loop-mediated isothermal PCR (LAMP), and nucleic acid sequence based amplification (NASBA). Other amplification schemes include: Ligase Chain Reaction, Branch DNA Amplification, Rolling Circle Amplification, Circle to Circle Amplification, SPIA amplification, Target Amplification by Capture and Ligation (TACL) amplification, and RACE amplification.
Another aspect of the invention provides methods for amplifying nucleic acid from a target that involve obtaining a sample including a target, conducting an assay that isolates the target from the sample, lysing the target to release the nucleic acid, and amplifying the released nucleic acid such that the lysing and the amplifying occur in the same reaction vessel.
Another aspect of the invention provides methods for amplifying nucleic acid from a target that involve obtaining a sample including a target, conducting an assay that isolates the target from the sample, and applying heat to the isolated target to thereby lyse the target within a reaction vessel and initiate within the reaction vessel an amplification reaction of nucleic acid released from the target.
The invention generally relates to methods for amplifying nucleic acids from a target. In certain embodiments, methods of the invention involve obtaining a sample including a target, conducting an assay that isolates the target from the sample, lysing the target to release the nucleic acid, and amplifying the released nucleic acid such that the amplifying occurs in the presence of debris from the lysing step. Accordingly, methods of the invention provide for amplification of a nucleic acid from a target without any intervening nucleic acid purification steps, i.e., direct amplification of a nucleic acid release from within a target.
Methods of the invention involve obtaining a sample, e.g., a tissue or body fluid that is suspected to include a target. The sample may be collected in any clinically acceptable manner. A tissue is a mass of connected cells and/or extracellular matrix material, e.g. skin tissue, nasal passage tissue, CNS tissue, neural tissue, eye tissue, liver tissue, kidney tissue, placental tissue, mammary gland tissue, placental tissue, gastrointestinal tissue, musculoskeletal tissue, genitourinary tissue, bone marrow, and the like, derived from, for example, a human or other mammal and includes the connecting material and the liquid material in association with the cells and/or tissues. In addition, fluidic samples formed from swabs or lavages representative of mucosal secretions and epithelia are acceptable, for example mucosal swabs of the throat, tonsils, gingival, nasal passages, vagina, urethra, rectum, lower colon, and eyes, as are homogenates, lysates and digests of tissue specimens of all sorts. A body fluid is a liquid material derived from, for example, a human or other mammal. Such body fluids include, but are not limited to, mucous, blood, plasma, serum, serum derivatives, bile, blood, phlegm, saliva, sweat, amniotic fluid, mammary fluid, urine, and cerebrospinal fluid (CSF), such as lumbar or ventricular CSF. A sample may also be a fine needle aspirate or biopsied tissue. A sample also may be media containing cells or biological material. In addition to biological samples, samples of water, industrial discharges, food products, milk, air filtrates, and so forth are suitable for use with the target capture system. These include food, environmental and industrial samples. In certain embodiments, fluidization of a generally solid sample may be required and is a process that can readily be accomplished off-cartridge.
The target refers to the substance in the sample that will be captured and isolated by methods of the invention. The target may be a pathogen (such as bacteria or fungi), a cell (such as a cancer cell, a white blood cell, a virally infected cell, or a fetal cell circulating in maternal circulation), or a virus. In certain embodiments, the target is a pathogenic bacteria. In other embodiments, the target is a gram positive or gram negative bacteria. Exemplary bacterial species that may be captured and isolated by methods of the invention include E. coli, Listeria, Clostridium, Mycobacterium, Shigella, Borrelia, Campylobacter, Bacillus, Salmonella, Staphylococcus, Enterococcus, Pneumococcus, Streptococcus, and a combination thereof.
An assay is conducted on the sample to isolate the target from other components of the sample. Any assay known in the art that is able to isolate a target from a sample may be used with methods of the invention. Centrifugation and filtration methods of isolating pathogen from a sample are shown in Bernhardt et al. (J. Clin. Microbiol., 29(3):422-425, 1991), the content of which is incorporated by reference herein in its entirety. Microfluidic based methods of isolating pathogen from a sample are shown in Zhigang et al. (Lab Chip, 9:1193, 2009), Qiu (Talanta, 79:787-795, 2009), and Zelenin (“Bacteria Isolation From Whole Blood For Sepsis Diagnostics,” 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences Oct. 2-6, 2011, Seattle, Wash.), the content of each of which is incorporated by reference herein in its entirety.
In certain embodiments, magnetic beads including a capture moiety are used in an assay to isolate the target from the sample. Certain fundamental technologies and principles are associated with binding magnetic materials to targets and subsequently separating by use of magnet fields and gradients. Such fundamental technologies and principles are known in the art and have been previously described, such as those described in Janeway (Immunobiology, 6th edition, Garland Science Publishing), the content of which is incorporated by reference herein in its entirety.
For magnetic bead based isolation assays, the sample including the target of interest is mixed with magnetic particles having a particular magnetic moment and also including a target-specific binding moiety to generate a mixture that is allowed to incubate such that the particles bind to a target in the sample, such as a bacterium in a blood sample. The mixture is allowed to incubate for a sufficient time to allow for the particles to bind to the target analyte. The process of binding the magnetic particles to the target analytes associates a magnetic moment with the target analytes, and thus allows the target analytes to be manipulated through forces generated by magnetic fields upon the attached magnetic moment.
In general, incubation time will depend on the desired degree of binding between the target analyte and the magnetic beads (e.g., the amount of moment that would be desirably attached to the target), the amount of moment per target, the amount of time of mixing, the type of mixing, the reagents present to promote the binding and the binding chemistry system that is being employed. Incubation time can be anywhere from about 5 seconds to a few days. Exemplary incubation times range from about 10 seconds to about 2 hours. Binding occurs over a wide range of temperatures, generally between 15° C. and 40° C.
Methods of the invention may use any magnetic particulars. In certain embodiments, methods of the invention are performed with magnetic particle having a magnetic moment that allows for isolation of as low as 1 CFU/ml of bacteria in the sample. Production of magnetic particles is shown for example in Giaever (U.S. Pat. No. 3,970,518), Senyi et al. (U.S. Pat. No. 4,230,685), Dodin et al. (U.S. Pat. No. 4,677,055), Whitehead et al. (U.S. Pat. No. 4,695,393), Benjamin et al. (U.S. Pat. No. 5,695,946), Giaever (U.S. Pat. No. 4,018,886), Rembaum (U.S. Pat. No. 4,267,234), Molday (U.S. Pat. No. 4,452,773), Whitehead et al. (U.S. Pat. No. 4,554,088), Forrest (U.S. Pat. No. 4,659,678), Liberti et al. (U.S. Pat. No. 5,186,827), Own et al. (U.S. Pat. No. 4,795,698), and Liberti et al. (WO 91/02811), the content of each of which is incorporated by reference herein in its entirety.
In certain aspects, the methods of the invention may use magnetic particles to isolate a target from the sample. Any type of magnetic particles can be used in conjunction with the target capture system. Production of magnetic particles and particles for use with the invention are known in the art. See for example Giaever (U.S. Pat. No. 3,970,518), Senyi et al. (U.S. Pat. No. 4,230,685), Dodin et al. (U.S. Pat. No. 4,677,055), Whitehead et al. (U.S. Pat. No. 4,695,393), Benjamin et al. (U.S. Pat. No. 5,695,946), Giaever (U.S. Pat. No. 4,018,886), Rembaum (U.S. Pat. No. 4,267,234), Molday (U.S. Pat. No. 4,452,773), Whitehead et al. (U.S. Pat. No. 4,554,088), Forrest (U.S. Pat. No. 4,659,678), Liberti et al. (U.S. Pat. No. 5,186,827), Own et al. (U.S. Pat. No. 4,795,698), and Liberti et al. (WO 91/02811), the content of each of which is incorporated by reference herein in its entirety.
Magnetic particles generally fall into two broad categories. The first category includes particles that are permanently magnetizable, or ferromagnetic; and the second category includes particles that demonstrate bulk magnetic behavior only when subjected to a magnetic field. The latter are referred to as magnetically responsive particles. Materials displaying magnetically responsive behavior are sometimes described as superparamagnetic. However, materials exhibiting bulk ferromagnetic properties, e.g., magnetic iron oxide, may be characterized as superparamagnetic when provided in crystals of about 30 nm or less in diameter. Larger crystals of ferromagnetic materials, by contrast, retain permanent magnet characteristics after exposure to a magnetic field and tend to aggregate thereafter due to strong particle-particle interaction. In certain embodiments, the particles are superparamagnetic beads. In certain embodiments, the magnetic particle is an iron containing magnetic particle. In other embodiments, the magnetic particle includes iron oxide or iron platinum.
In certain embodiments, the magnetic particles include at least about 10% superparamagnetic beads by weight, at least about 20% superparamagnetic beads by weight, at least about 30% superparamagnetic beads by weight, at least about 40% superparamagnetic beads by weight, at least about 50% superparamagnetic beads by weight, at least about 60% superparamagnetic beads by weight, at least about 70% superparamagnetic beads by weight, at least about 80% superparamagnetic beads by weight, at least about 90% superparamagnetic beads by weight, at least about 95% superparamagnetic beads by weight, or at least about 99% superparamagnetic beads by weight. In a particular embodiment, the magnetic particles include at least about 70% superparamagnetic beads by weight.
In certain embodiments, the superparamagnetic beads are less than 100 nm in diameter. In other embodiments, the superparamagnetic beads are about 150 nm in diameter, are about 200 nm in diameter, are about 250 nm in diameter, are about 300 nm in diameter, are about 350 nm in diameter, are about 400 nm in diameter, are about 500 nm in diameter, or are about 1000 nm in diameter. In a particular embodiment, the superparamagnetic beads are from about 100 nm to about 250 nm in diameter.
In certain embodiments, the particles are beads (e.g., nanoparticles) that incorporate magnetic materials, or magnetic materials that have been functionalized, or other configurations as are known in the art. In certain embodiments, nanoparticles may be used that include a polymer material that incorporates magnetic material(s), such as nanometal material(s). When those nanometal material(s) or crystal(s), such as Fe3O4, are superparamagnetic, they may provide advantageous properties, such as being capable of being magnetized by an external magnetic field, and demagnetized when the external magnetic field has been removed. This may be advantageous for facilitating sample transport into and away from an area where the sample is being processed without undue bead aggregation.
One or more or many different nanometal(s) may be employed, such as Fe3O4, FePt, or Fe, in a core-shell configuration to provide stability, and/or various others as may be known in the art. In many applications, it may be advantageous to have a nanometal having as high a saturated moment per volume as possible, as this may maximize gradient related forces, and/or may enhance a signal associated with the presence of the beads. It may also be advantageous to have the volumetric loading in a bead be as high as possible, for the same or similar reason(s). In order to maximize the moment provided by a magnetizable nanometal, a certain saturation field may be provided. For example, for Fe3O4 superparamagnetic particles, this field may be on the order of about 0.3T.
The size of the nanometal containing bead may be optimized for a particular application, for example, maximizing moment loaded upon a target, maximizing the number of beads on a target with an acceptable detectability, maximizing desired force-induced motion, and/or maximizing the difference in attached moment between the labeled target and non-specifically bound targets or bead aggregates or individual beads. While maximizing is referenced by example above, other optimizations or alterations are contemplated, such as minimizing or otherwise desirably affecting conditions.
In an exemplary embodiment, a polymer bead containing 80 wt % Fe3O4 superparamagnetic particles, or for example, 90 wt % or higher superparamagnetic particles, is produced by encapsulating superparamagnetic particles with a polymer coating to produce a bead having a diameter of about 250 nm.
Magnetic particles for use with methods of the invention have a target-specific binding moiety that allows for the particles to specifically bind the target of interest in the sample. The target-specific moiety may be any molecule known in the art and will depend on the target to be captured and isolated. Exemplary target-specific binding moieties include nucleic acids (including nucleic acid probes), proteins, ligands, lectins, antibodies, aptamers, bactertiophages, host innate immunity biomarkers (e.g., CD14), host defense peptides (e.g., defensins), bacteriocins (e.g., pyocins), and receptors.
In particular embodiments, the target-specific binding moiety is an antibody, such as an antibody that binds a particular bacterium. General methodologies for antibody production, including criteria to be considered when choosing an animal for the production of antisera, are described in Harlow et al. (Antibodies, Cold Spring Harbor Laboratory, pp. 93-117, 1988). For example, an animal of suitable size such as goats, dogs, sheep, mice, or camels are immunized by administration of an amount of immunogen, such the target bacteria, effective to produce an immune response. An exemplary protocol is as follows. The animal is injected with 100 milligrams of antigen resuspended in adjuvant, for example Freund's complete adjuvant, dependent on the size of the animal, followed three weeks later with a subcutaneous injection of 100 micrograms to 100 milligrams of immunogen with adjuvant dependent on the size of the animal, for example Freund's incomplete adjuvant. Additional subcutaneous or intraperitoneal injections every two weeks with adjuvant, for example Freund's incomplete adjuvant, are administered until a suitable titer of antibody in the animal's blood is achieved. Exemplary titers include a titer of at least about 1:5000 or a titer of 1:100,000 or more, i.e., the dilution having a detectable activity. The antibodies are purified, for example, by affinity purification on columns containing protein G resin or target-specific affinity resin.
The technique of in vitro immunization of human lymphocytes is used to generate monoclonal antibodies. Techniques for in vitro immunization of human lymphocytes are well known to those skilled in the art. See, e.g., Inai, et al., Histochemistry, 99(5):335 362, May 1993; Mulder, et al., Hum. Immunol., 36(3):186 192, 1993; Harada, et al., J. Oral Pathol. Med., 22(4):145 152, 1993; Stauber, et al., J. Immunol. Methods, 161(2):157 168, 1993; and Venkateswaran, et al., Hybridoma, 11(6) 729 739, 1992. These techniques can be used to produce antigen-reactive monoclonal antibodies, including antigen-specific IgG, and IgM monoclonal antibodies.
Any antibody or fragment thereof having affinity and specific for the bacteria of interest is within the scope of the invention provided herein. Immunomagnetic beads against Salmonella are provided in Vermunt et al. (J. Appl. Bact. 72:112, 1992). Immunomagnetic beads against Staphylococcus aureus are provided in Johne et al. (J. Clin. Microbiol. 27:1631, 1989). Immunomagnetic beads against Listeria are provided in Skjerve et al. (Appl. Env. Microbiol. 56:3478, 1990). Immunomagnetic beads against Escherichia coli are provided in Lund et al. (J. Clin. Microbiol. 29:2259, 1991).
Methods for attaching the target-specific binding moiety to the magnetic particle are known in the art. Coating magnetic particles with antibodies is well known in the art, see for example Harlow et al. (Antibodies, Cold Spring Harbor Laboratory, 1988), Hunter et al. (Immunoassays for Clinical Chemistry, pp. 147-162, eds., Churchill Livingston, Edinborough, 1983), and Stanley (Essentials in Immunology and Serology, Delmar, pp. 152-153, 2002). Such methodology can easily be modified by one of skill in the art to bind other types of target-specific binding moieties to the magnetic particles. Certain types of magnetic particles coated with a functional moiety are commercially available from Sigma-Aldrich (St. Louis, Mo.).
In certain embodiments, the target-specific binding moiety is a lectin. Lectins are sugar-binding proteins that are highly specific for their sugar moieties. Exemplary lectins that may be used as target-specific binding moieties include Concanavalin (ConA), Wheat Germ Extract WGA). Others lectins that have bacteria-binding properties are shown in Table 1 below.
Arum maculatum
Allium sativum
Canavalia ensiformis
Griffonia simplicoflia
Hippeastrum hybrid
Iris hybric
Lycopersicon esculentum
Limulus polyphemus
Mangidera indica
Perseau americana
Triticum vulgaris
In certain embodiments, a buffer solution is added to the sample along with the magnetic beads. An exemplary buffer includes Tris(hydroximethyl)-aminomethane hydrochloride at a concentration of about 75 mM. It has been found that the buffer composition, mixing parameters (speed, type of mixing, such as rotation, shaking etc., and temperature) influence binding. It is important to maintain osmolality of the final solution (e.g., blood+buffer) to maintain high label efficiency. In certain embodiments, buffers used in methods of the invention are designed to prevent lysis of blood cells, facilitate efficient binding of targets with magnetic beads and to reduce formation of bead aggregates. It has been found that the buffer solution containing 300 mM NaCl, 75 mM Tris-HCl pH 8.0 and 0.1% Tween 20 meets these design goals.
Without being limited by any particular theory or mechanism of action, it is believed that sodium chloride is mainly responsible for maintaining osmolality of the solution and for the reduction of non-specific binding of magnetic bead through ionic interaction. Tris(hydroximethyl)-aminomethane hydrochloride is a well established buffer compound frequently used in biology to maintain pH of a solution. It has been found that 75 mM concentration is beneficial and sufficient for high binding efficiency. Likewise, Tween 20 is widely used as a mild detergent to decrease nonspecific attachment due to hydrophobic interactions. Various assays use Tween 20 at concentrations ranging from 0.01% to 1%. The 0.1% concentration appears to be optimal for the efficient labeling of bacteria, while maintaining blood cells intact.
An alternative approach to achieve high binding efficiency while reducing time required for the binding step is to use static mixer, or other mixing devices that provide efficient mixing of viscous samples at high flow rates, such as at or around 5 mL/min. In one embodiment, the sample is mixed with binding buffer in ratio of, or about, 1:1, using a mixing interface connector. The diluted sample then flows through a mixing interface connector where it is mixed with target-specific nanoparticles. Additional mixing interface connectors providing mixing of sample and antigen-specific nanoparticles can be attached downstream to improve binding efficiency. The combined flow rate of the labeled sample is selected such that it is compatible with downstream processing.
After binding of the magnetic particles to the target in the mixture to form target/magnetic particle complexes, a magnetic field is applied to the mixture to capture the complexes on a surface. Components of the mixture that are not bound to magnetic particles will not be affected by the magnetic field and will remain free in the mixture. Methods and apparatuses for separating target/magnetic particle complexes from other components of a mixture are known in the art. For example, a steel mesh may be coupled to a magnet, a linear channel or channels may be configured with adjacent magnets, or quadrapole magnets with annular flow may be used. Other methods and apparatuses for separating target/magnetic particle complexes from other components of a mixture are shown in Rao et al. (U.S. Pat. No. 6,551,843), Liberti et al. (U.S. Pat. No. 5,622,831), Hatch et al. (U.S. Pat. No. 6,514,415), Benjamin et al. (U.S. Pat. No. 5,695,946), Liberti et al. (U.S. Pat. No. 5,186,827), Wang et al. (U.S. Pat. No. 5,541,072), Liberti et al. (U.S. Pat. No. 5,466,574), and Terstappen et al. (U.S. Pat. No. 6,623,983), the content of each of which is incorporated by reference herein in its entirety.
In certain embodiments, the magnetic capture is achieved at high efficiency by utilizing a flow-through capture cell with a number of strong rare earth bar magnets placed perpendicular to the flow of the sample. When using a flow chamber with flow path cross-section 0.5 mm×20 mm (h×w) and 7 bar NdFeB magnets, the flow rate could be as high as 5 mL/min or more, while achieving capture efficiency close to 100%.
The above described type of magnetic separation produces efficient capture of a target analyte and the removal of a majority of the remaining components of a sample mixture. However, such a process may produce a sample that contains a percent of magnetic particles that are not bound to target analytes, as well as non-specific target entities. Non-specific target entities may for example be bound at a much lower efficiency, for example 1% of the surface area, while a target of interest might be loaded at 50% or nearly 100% of the available surface area or available antigenic cites. However, even 1% loading may be sufficient to impart force necessary for trapping in a magnetic gradient flow cell or sample chamber.
The presence of magnetic particles that are not bound to target analytes and non-specific target entities on the surface that includes the target/magnetic particle complexes may interfere with the ability to successfully detect the target of interest. The magnetic capture of the resulting mix, and close contact of magnetic particles with each other and bound targets, result in the formation of aggregate that is hard to dispense and which might be resistant or inadequate for subsequent processing or analysis steps. In order to remove magnetic particles that are not bound to target analytes and non-specific target entities, methods of the invention may further involve washing the surface with a wash solution that reduces particle aggregation, thereby isolating target/magnetic particle complexes from the magnetic particles that are not bound to target analytes and non-specific target entities. The wash solution minimizes the formation of the aggregates.
Methods of the invention may use any wash solution that imparts a net negative charge to the magnetic particle that is not sufficient to disrupt interaction between the target-specific moiety of the magnetic particle and the target. Without being limited by any particular theory or mechanism of action, it is believed that attachment of the negatively charged molecules in the wash solution to magnetic particles provides net negative charge to the particles and facilitates dispersal of non-specifically aggregated particles. At the same time, the net negative charge is not sufficient to disrupt strong interaction between the target-specific moiety of the magnetic particle and the target analyte (e.g., an antibody-antigen interaction). Exemplary solutions include heparin, Tris-HCl, Tris-borate-EDTA (TBE), Tris-acetate-EDTA (TAE), Tris-cacodylate, HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid), PBS (phosphate buffered saline), PIPES (piperazine-N,N′-bis(2-ethanesulfonic acid), MES (2-N-morpholino)ethanesulfonic acid), Tricine (N-(Tri(hydroximethyl)methyl)glycine), and similar buffering agents. In certain embodiments, only a single wash cycle is performed. In other embodiments, more than one wash cycle is performed.
In particular embodiments, the wash solution includes heparin. For embodiments in which the body fluid sample is blood, the heparin also reduces probability of clotting of blood components after magnetic capture. The bound targets are washed with heparin-containing buffer 1-3 times to remove blood components and to reduce formation of aggregates.
Generally, amplification reagents (e.g., primers, nucleotide triphosphates, polymerases, metal ions, buffers, etc.) are then introduced into a vessel including the isolated intact target, and a lysis procedure is then conducted in the presence of the amplification reagents, such that nucleic acid is released from within the lysed target. However, the amplification reagents do not need to be added prior to the lysis procedure and in certain embodiments, the amplification reagents are added after the lysis procedure is conducted.
Any lysis procedure known in the art may be used to lyse the target. Exemplary methods include enzymatic methods (such as lysozyme, mutanolysin and proteinase K), mechanical methods, thermal methods, chemical methods, or a combination thereof. Exemplary mechanical methods include sonication (i.e., sonic oscillation), bead beating (Vandeventer, J Clin Microbiol. 2011 July; 49(7):2533-9), and liquid homogenization (shearing by forcing the target them through a narrow space). Chemical methods, buffers and combinations of detergents, such as nonionic detergent, can also be employed. Generally, lysis buffers contain alkali (such as NaOH), guanidine salts (such as guanidine thiocyanate), tris-HCl, EDTA, EGTA, SDS, deoxycholate, tritonX and/or NP-40. In some cases the buffer may also contain NaCl (150 mM). An exemplary chemical lysis buffer is (7 M urea, 2 M thiourea, 4% (w/v) 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), 65 mM dithiothreitol (DTT), and 1% (v/v) protease inhibitor at −80° C.). Other such buffers are known in the art and are commercially available.
In particular embodiments, the target is lysed using thermal methods. In thermal lysis, the target is heated to about 90° C., about 95° C., about 100° C., etc., causing the target to lyse. Thermal lysis procedures are described for example in Privorotskaya et al. (Lab Chip. 2010 May 7; 10(9):1135-41) and Kim et al. (Journal of Nanoscience and Nanotechnology, Vol. 9, 2841-2845, 2009), the content of each of which is incorporated by reference herein in its entirety. Application of heat not only lyses the target, it also denatures the released double stranded nucleic acid into single stranded nucleic acid and initiates the amplification reaction. Another advantage of thermal lysis is that the heat facilitates denaturation/inactivation of nucleases that can cause degradation of nucleic acid.
After lysis, an amplification reaction is conducted on the nucleic acid released form the target. The amplification reaction is conducted in the presence of the debris from the lysis procedure and is generally conducted in the same reaction vessel as used for the lysis procedure. In this manner, nucleic acid from the target is amplified without the need for first purifying the isolated nucleic acid.
Amplification refers to production of additional copies of a nucleic acid sequence and is generally carried out using polymerase chain reaction or other technologies well known in the art (e.g., Dieffenbach and Dveksler, PCR Primer, a Laboratory Manual, Cold Spring Harbor Press, Plainview, N.Y. [1995]). The amplification reaction may be any amplification reaction known in the art that amplifies nucleic acid molecules. Exemplary amplification techniques include polymerase chain reaction (PCR), reverse transcription-PCR, real-time PCR, quantitative real-time PCR, digital PCR (dPCR), digital emulsion PCR (dePCR), clonal PCR, amplified fragment length polymorphism PCR (AFLP PCR), allele specific PCR, assembly PCR, asymmetric PCR (in which a great excess of primers for a chosen strand is used), colony PCR, helicase-dependent amplification (HDA), Hot Start PCR, inverse PCR (IPCR), in situ PCR, long PCR (extension of DNA greater than about 5 kilobases), multiplex PCR, nested PCR (uses more than one pair of primers), single-cell PCR, touchdown PCR, loop-mediated isothermal PCR (LAMP), and nucleic acid sequence based amplification (NASBA). Other amplification schemes include: Ligase Chain Reaction (Barany F. (1991) PNAS 88:189-193; Barany F. (1991) PCR Methods and Applications 1:5-16), ligase detection reaction (Barany F. (1991) PNAS 88:189-193), Branch DNA Amplification, Rolling Circle Amplification, Circle to Circle Amplification, SPIA amplification, Target Amplification by Capture and Ligation (TACL) amplification, and RACE amplification.
In certain embodiments, PCR is used. PCR refers to methods by K. B. Mullis (U.S. Pat. Nos. 4,683,195 and 4,683,202, hereby incorporated by reference) for increasing concentration of a segment of a target sequence in a mixture of genomic DNA without cloning or purification. The process for amplifying the target sequence includes introducing an excess of oligonucleotide primers to a DNA mixture containing a desired target sequence, followed by a precise sequence of thermal cycling in the presence of a DNA polymerase. The primers are complementary to their respective strands of the double stranded target sequence.
Primers can be prepared by a variety of methods including but not limited to cloning of appropriate sequences and direct chemical synthesis using methods well known in the art (Narang et al., Methods Enzymol., 68:90 (1979); Brown et al., Methods Enzymol., 68:109 (1979)). Primers can also be obtained from commercial sources such as Operon Technologies, Amersham Pharmacia Biotech, Sigma, and Life Technologies. The primers can have an identical melting temperature. The lengths of the primers can be extended or shortened at the 5′ end or the 3′ end to produce primers with desired melting temperatures. Also, the annealing position of each primer pair can be designed such that the sequence and, length of the primer pairs yield the desired melting temperature. The simplest equation for determining the melting temperature of primers smaller than 25 base pairs is the Wallace Rule (Td=2(A+T)+4(G+C)). Computer programs can also be used to design primers, including but not limited to Array Designer Software (Arrayit Inc.), Oligonucleotide Probe Sequence Design Software for Genetic Analysis (Olympus Optical Co.), NetPrimer, and DNAsis from Hitachi Software Engineering. The TM (melting or annealing temperature) of each primer is calculated using software programs such as Oligo Design, available from Invitrogen Corp.
To effect amplification, the mixture is denatured and the primers are then annealed to their complementary sequences within the target molecule. Following annealing, the primers are extended with a polymerase so as to form a new pair of complementary strands. The steps of denaturation, primer annealing and polymerase extension can be repeated many times (i.e., denaturation, annealing and extension constitute one cycle; there can be numerous cycles) to obtain a high concentration of an amplified segment of a desired target sequence. The length of the amplified segment of the desired target sequence is determined by relative positions of the primers with respect to each other, and therefore, this length is a controllable parameter.
With PCR, it is possible to amplify a single copy of a specific target sequence in genomic DNA to a level that can be detected by several different methodologies (e.g., staining, hybridization with a labeled probe; incorporation of biotinylated primers followed by avidin-enzyme conjugate detection; incorporation of 32P-labeled deoxynucleotide triphosphates, such as dCTP or dATP, into the amplified segment). In addition to genomic DNA, any oligonucleotide sequence can be amplified with the appropriate set of primer molecules. In particular, the amplified segments created by the PCR process itself are, themselves, efficient templates for subsequent PCR amplifications. Amplified target sequences can be used to obtain segments of DNA (e.g., genes) for insertion into recombinant vectors.
Temperatures for conducting a PCR reaction are well known in the art and typically include a temperature sufficient for denaturing a nucleic acid template (e.g., 94°-100° C.), a temperature sufficient for causing one or more PCR reagents, such as the primers, to anneal to a strand of the denatured nucleic acid template (e.g., 50°-65° C.), and a temperature sufficient to allow extension of each primer in the 5′ to 3′ direction, duplicating the DNA fragment between the primers (e.g., 68°-72° C.).
In certain embodiments, heat is used to lysis the target and initiate the amplification reaction. In this embodiment, heat is applied by any method known in the art at a temperature of about 95° C., which results in target lysis and denaturation of the released nucleic acid. The temperature is then decreased to a range of about 50° C. to 65° C. to allow annealing of primers to single stranded nucleic acids. The temperature is then raised to a range of about 68° C. to 72° C. to allow extension of each primer in the 5′ to 3′ direction. PCR cycles are then conducted as described above and as known in the art.
In certain embodiments, isothermal amplification is used. In these embodiments, the target is lysed by any method known in the art, but particularly useful is thermal lysing, and the target sequence is amplified at a constant temperature of 60° C. to 65° C. using either two or three sets of primers and a polymerase with high strand displacement activity in addition to a replication activity. In certain embodiments, heat is used to lysis the target and initiate the isothermal amplification reaction.
Any polymerase known in the art that is routinely used with the above amplification reactions may be used with methods of the invention. Nucleic acid polymerases generally useful in the invention include DNA polymerases, RNA polymerases, reverse transcriptases, and mutant or altered forms of any of the foregoing. DNA polymerases and their properties are described in detail in, among other places, DNA Replication 2nd edition, Kornberg and Baker, W.H. Freeman, New York, N.Y. (1991). Known conventional DNA polymerases useful in the invention include, but are not limited to, Pyrococcus furiosus (Pfu) DNA polymerase (Lundberg et al., 1991, Gene, 108: 1, Stratagene), Pyrococcus woesei (Pwo) DNA polymerase (Hinnisdaels et al., 1996, Biotechniques, 20:186-8, Boehringer Mannheim), Thermus thermophilus (Tth) DNA polymerase (Myers and Gelfand 1991, Biochemistry 30:7661), Bacillus stearothermophilus DNA polymerase (Stenesh and McGowan, 1977, Biochim Biophys Acta 475:32), Thermococcus litoralis (Tli) DNA polymerase (also referred to as Vent™ DNA polymerase, Cariello et al., 1991, Polynucleotides Res, 19: 4193, New England Biolabs), 9.degree.Nm. (DNA polymerase, New England Biolabs), Stoffel fragment, ThermoSequenase (polymerase, Amersham Pharmacia Biotech UK), Therminator. (polymerase, commercially available by New England Biolabs), Thermotoga maritima (Tma) DNA polymerase (Diaz and Sabino, 1998 Braz J. Med. Res, 31:1239), Thermus aquaticus (Taq) DNA polymerase (Chien et al., 1976, J. Bacteoriol, 127: 1550), DNA polymerase, Pyrococcus kodakaraensis KOD DNA polymerase (Takagi et al., 1997, Appl. Environ. Microbiol. 63:4504), JDF-3 DNA polymerase (from thermococcus sp. JDF-3, Patent application WO 0132887), Pyrococcus GB-D (PGB-D) DNA polymerase (also referred as Deep Vent™ DNA polymerase, Juncosa-Ginesta et al., 1994, Biotechniques, 16:820, New England Biolabs), UlTma DNA polymerase (from thermophile Thermotoga maritima; Diaz and Sabino, 1998 Braz J. Med. Res, 31:1239; PE Applied Biosystems), Tgo DNA polymerase (from thermococcus gorgonarius, Roche Molecular Biochemicals), E. coli DNA polymerase I (Lecomte and Doubleday, 1983, Polynucleotides Res. 11:7505), T7 DNA polymerase (Nordstrom et al., 1981, J. Biol. Chem. 256:3112), and archaeal DP1I/DP2 DNA polymerase II (Cann et al, 1998, Proc. Natl. Acad. Sci. USA 95:14250).
Both mesophilic polymerases and thermophilic polymerases are contemplated. Thermophilic DNA polymerases include, but are not limited to, ThermoSequenase (polymerase, commercially available by Amersham Pharmacia Biotech UK), 9.degree.Nm. (polymerase, commercially available by New England Biolabs), Therminator. (polymerase, commercially available by New England Biolabs), Taq, Tne, Tma, Pfu, Tfl, Tth, Tli, Stoffel fragment, Vent. (polymerase, commercially available by New England Biolabs) and Deep Vent. (polymerase, commercially available by New England Biolabs), KOD DNA polymerase, Tgo, JDF-3, and mutants, variants and derivatives thereof. A highly-preferred form of any polymerase is a 3′ exonuclease-deficient mutant.
Reverse transcriptases useful in the invention include, but are not limited to, reverse transcriptases from HIV, HTLV-1, HTLV-II, FeLV, FIV, SIV, AMV, MMTV, MoMuLV and other retroviruses (see Levin, Cell 88:5-8 (1997); Verma, Biochim Biophys Acta. 473:1-38 (1977); Wu et al., CRC Crit. Rev Biochem. 3:289-347 (1975)).
In certain embodiments, the polymerase is a genetic variant of Taq polymerase that is efficient at nucleic acid amplification in the presence of matrix components (e.g., residual blood components such as heme), that otherwise hinder nucleic acid amplification.
Any method known in the art may be used to detect the amplification products, and thus identify the target in the sample, for example identify a pathogen from a human tissue or body fluid sample, such as blood or urine. Exemplary methods for detecting amplification products involve running the amplification products through a gel using, for example polyacrylamide gel electrophoresis or capillary electrophoresis.
In other embodiments, probe hybridization is carried out on the amplification products. Suitable procedures for detection of bacteria using nucleic acid probes are described, for example, in Stackebrandt et al. (U.S. Pat. No. 5,089,386), King et al. (WO 90/08841), Foster et al. (WO 92/15883), and Cossart et al. (WO 89/06699), each of which is hereby incorporated by reference. Hybridization includes addition of the specific nucleic acid probes. In general, hybridization is the procedure by which two partially or completely complementary nucleic acids are combined, under defined reaction conditions, in an anti-parallel fashion to form specific and stable hydrogen bonds. The selection or stringency of the hybridization/reaction conditions is defined by the length and base composition of the probe/target duplex, as well as by the level and geometry of mis-pairing between the two nucleic acid strands. Stringency is also governed by such reaction parameters as temperature, types and concentrations of denaturing agents present and the type and concentration of ionic species present in the hybridization solution.
The hybridization phase of the nucleic acid probe assay is performed with a single selected probe or with a combination of two, three or more probes. Probes are selected having sequences which are homologous to unique nucleic acid sequences of the target organism. In general, a first capture probe is utilized to capture formed hybrid molecules. The hybrid molecule is then detected by use of antibody reaction or by use of a second detector probe which may be labelled with a radioisotope (such as phosphorus-32) or a fluorescent label (such as fluorescein) or chemiluminescent label.
In other embodiments, the QPCR reaction uses fluorescent Taqman methodology and an instrument capable of measuring fluorescence in real time (e.g., ABI Prism 7700 Sequence Detector). During amplification, fluorescent signal is generated in a TaqMan assay by the enzymatic degradation of the fluorescently labeled probe. The probe contains a dye and quencher that are maintained in close proximity to one another by being attached to the same probe. When in close proximity, the dye is quenched by fluorescence resonance energy transfer to the quencher. Certain probes are designed that hybridize to the wild-type of the target, and other probes are designed that hybridize to a variant of the wild-type of the target. Probes that hybridize to the wild-type of the target have a different fluorophore attached than probes that hybridize to a variant of the wild-type of the target. The probes that hybridize to a variant of the wild-type of the target are designed to specifically hybridize to a region in a PCR product that contains or is suspected to contain a single nucleotide polymorphism or small insertion or deletion.
During the PCR amplification, the amplicon is denatured allowing the probe and PCR primers to hybridize. The PCR primer is extended by Taq polymerase replicating the alternative strand. During the replication process the Taq polymerase encounters the probe which is also hybridized to the same strand and degrades it. This releases the dye and quencher from the probe which are then allowed to move away from each other. This eliminates the FRET between the two, allowing the dye to release its fluorescence. Through each cycle of cycling more fluorescence is released. The amount of fluorescence released depends on the efficiency of the PCR reaction and also the kinetics of the probe hybridization. If there is a single mismatch between the probe and the target sequence the probe will not hybridize as efficiently and thus a fewer number of probes are degraded during each round of PCR and thus less fluorescent signal is generated. This difference in fluorescence per droplet can be detected and counted. The efficiency of hybridization can be affected by such things as probe concentration, probe ratios between competing probes, and the number of mismatches present in the probe.
In other embodiments, sequencing is used to analyze the target, such as identifying a pathogen from a body fluid. Sequencing may be by any method known in the art. DNA sequencing techniques include classic dideoxy sequencing reactions (Sanger method) using labeled terminators or primers and gel separation in slab or capillary, sequencing by synthesis using reversibly terminated labeled nucleotides, pyrosequencing, 454 sequencing, allele specific hybridization to a library of labeled oligonucleotide probes, sequencing by synthesis using allele specific hybridization to a library of labeled clones that is followed by ligation, real time monitoring of the incorporation of labeled nucleotides during a polymerization step, polony sequencing, and SOLiD sequencing. Sequencing of separated molecules has more recently been demonstrated by sequential or single extension reactions using polymerases or ligases as well as by single or sequential differential hybridizations with libraries of probes.
A sequencing technique that can be used in the methods of the provided invention includes, for example, Helicos True Single Molecule Sequencing (tSMS) (Harris T. D. et al. (2008) Science 320:106-109). In the tSMS technique, a DNA sample is cleaved into strands of approximately 100 to 200 nucleotides, and a polyA sequence is added to the 3′ end of each DNA strand. Each strand is labeled by the addition of a fluorescently labeled adenosine nucleotide. The DNA strands are then hybridized to a flow cell, which contains millions of oligo-T capture sites that are immobilized to the flow cell surface. The templates can be at a density of about 100 million templates/cm2. The flow cell is then loaded into an instrument, e.g., HeliScope (sequencer, commercially available by Helicos Biosciences) sequencer, and a laser illuminates the surface of the flow cell, revealing the position of each template. A CCD camera can map the position of the templates on the flow cell surface. The template fluorescent label is then cleaved and washed away. The sequencing reaction begins by introducing a DNA polymerase and a fluorescently labeled nucleotide. The oligo-T nucleic acid serves as a primer. The polymerase incorporates the labeled nucleotides to the primer in a template directed manner. The polymerase and unincorporated nucleotides are removed. The templates that have directed incorporation of the fluorescently labeled nucleotide are detected by imaging the flow cell surface. After imaging, a cleavage step removes the fluorescent label, and the process is repeated with other fluorescently labeled nucleotides until the desired read length is achieved. Sequence information is collected with each nucleotide addition step. Further description of tSMS is shown for example in Lapidus et al. (U.S. Pat. No. 7,169,560), Lapidus et al. (U.S. patent application number 2009/0191565), Quake et al. (U.S. Pat. No. 6,818,395), Harris (U.S. Pat. No. 7,282,337), Quake et al. (U.S. patent application number 2002/0164629), and Braslaysky, et al., PNAS (USA), 100: 3960-3964 (2003), the contents of each of these references is incorporated by reference herein in its entirety.
Another example of a DNA sequencing technique that can be used in the methods of the provided invention is 454 sequencing (Roche) (Margulies, M et al. 2005, Nature, 437, 376-380). 454 sequencing involves two steps. In the first step, DNA is sheared into fragments of approximately 300-800 base pairs, and the fragments are blunt ended. Oligonucleotide adaptors are then ligated to the ends of the fragments. The adaptors serve as primers for amplification and sequencing of the fragments. The fragments can be attached to DNA capture beads, e.g., streptavidin-coated beads using, e.g., Adaptor B, which contains 5′-biotin tag. The fragments attached to the beads are PCR amplified within droplets of an oil-water emulsion. The result is multiple copies of clonally amplified DNA fragments on each bead. In the second step, the beads are captured in wells (pico-liter sized). Pyrosequencing is performed on each DNA fragment in parallel. Addition of one or more nucleotides generates a light signal that is recorded by a CCD camera in a sequencing instrument. The signal strength is proportional to the number of nucleotides incorporated. Pyrosequencing makes use of pyrophosphate (PPi) which is released upon nucleotide addition. PPi is converted to ATP by ATP sulfurylase in the presence of adenosine 5′ phosphosulfate. Luciferase uses ATP to convert luciferin to oxyluciferin, and this reaction generates light that is detected and analyzed.
Another example of a DNA sequencing technique that can be used in the methods of the provided invention is SOLiD technology (Applied Biosystems). In SOLiD sequencing, genomic DNA is sheared into fragments, and adaptors are attached to the 5′ and 3′ ends of the fragments to generate a fragment library. Alternatively, internal adaptors can be introduced by ligating adaptors to the 5′ and 3′ ends of the fragments, circularizing the fragments, digesting the circularized fragment to generate an internal adaptor, and attaching adaptors to the 5′ and 3′ ends of the resulting fragments to generate a mate-paired library. Next, clonal bead populations are prepared in microreactors containing beads, primers, template, and PCR components. Following PCR, the templates are denatured and beads are enriched to separate the beads with extended templates. Templates on the selected beads are subjected to a 3′ modification that permits bonding to a glass slide. The sequence can be determined by sequential hybridization and ligation of partially random oligonucleotides with a central determined base (or pair of bases) that is identified by a specific fluorophore. After a color is recorded, the ligated oligonucleotide is cleaved and removed and the process is then repeated.
Another example of a DNA sequencing technique that can be used in the methods of the provided invention is Ion Torrent sequencing (U.S. patent application numbers 2009/0026082, 2009/0127589, 2010/0035252, 2010/0137143, 2010/0188073, 2010/0197507, 2010/0282617, 2010/0300559), 2010/0300895, 2010/0301398, and 2010/0304982), the content of each of which is incorporated by reference herein in its entirety. In Ion Torrent sequencing, DNA is sheared into fragments of approximately 300-800 base pairs, and the fragments are blunt ended. Oligonucleotide adaptors are then ligated to the ends of the fragments. The adaptors serve as primers for amplification and sequencing of the fragments. The fragments can be attached to a surface and is attached at a resolution such that the fragments are individually resolvable. Addition of one or more nucleotides releases a proton (H+), which signal detected and recorded in a sequencing instrument. The signal strength is proportional to the number of nucleotides incorporated.
Another example of a sequencing technology that can be used in the methods of the provided invention is Illumina sequencing. Illumina sequencing is based on the amplification of DNA on a solid surface using fold-back PCR and anchored primers. Genomic DNA is fragmented, and adapters are added to the 5′ and 3′ ends of the fragments. DNA fragments that are attached to the surface of flow cell channels are extended and bridge amplified. The fragments become double stranded, and the double stranded molecules are denatured. Multiple cycles of the solid-phase amplification followed by denaturation can create several million clusters of approximately 1,000 copies of single-stranded DNA molecules of the same template in each channel of the flow cell. Primers, DNA polymerase and four fluorophore-labeled, reversibly terminating nucleotides are used to perform sequential sequencing. After nucleotide incorporation, a laser is used to excite the fluorophores, and an image is captured and the identity of the first base is recorded. The 3′ terminators and fluorophores from each incorporated base are removed and the incorporation, detection and identification steps are repeated.
Another example of a sequencing technology that can be used in the methods of the provided invention includes the single molecule, real-time (SMRT) technology of Pacific Biosciences. In SMRT, each of the four DNA bases is attached to one of four different fluorescent dyes. These dyes are phospholinked. A single DNA polymerase is immobilized with a single molecule of template single stranded DNA at the bottom of a zero-mode waveguide (ZMW). A ZMW is a confinement structure which enables observation of incorporation of a single nucleotide by DNA polymerase against the background of fluorescent nucleotides that rapidly diffuse in an out of the ZMW (in microseconds). It takes several milliseconds to incorporate a nucleotide into a growing strand. During this time, the fluorescent label is excited and produces a fluorescent signal, and the fluorescent tag is cleaved off. Detection of the corresponding fluorescence of the dye indicates which base was incorporated. The process is repeated.
Another example of a sequencing technique that can be used in the methods of the provided invention is nanopore sequencing (Soni G V and Meller A. (2007) Clin Chem 53: 1996-2001). A nanopore is a small hole, of the order of 1 nanometer in diameter. Immersion of a nanopore in a conducting fluid and application of a potential across it results in a slight electrical current due to conduction of ions through the nanopore. The amount of current which flows is sensitive to the size of the nanopore. As a DNA molecule passes through a nanopore, each nucleotide on the DNA molecule obstructs the nanopore to a different degree. Thus, the change in the current passing through the nanopore as the DNA molecule passes through the nanopore represents a reading of the DNA sequence.
Another example of a sequencing technique that can be used in the methods of the provided invention involves using a chemical-sensitive field effect transistor (chemFET) array to sequence DNA (for example, as described in US Patent Application Publication No. 20090026082). In one example of the technique, DNA molecules can be placed into reaction chambers, and the template molecules can be hybridized to a sequencing primer bound to a polymerase. Incorporation of one or more triphosphates into a new nucleic acid strand at the 3′ end of the sequencing primer can be detected by a change in current by a chemFET. An array can have multiple chemFET sensors. In another example, single nucleic acids can be attached to beads, and the nucleic acids can be amplified on the bead, and the individual beads can be transferred to individual reaction chambers on a chemFET array, with each chamber having a chemFET sensor, and the nucleic acids can be sequenced.
Another example of a sequencing technique that can be used in the methods of the provided invention involves using an electron microscope (Moudrianakis E. N. and Beer M. Proc Natl Acad Sci USA. 1965 March; 53:564-71). In one example of the technique, individual DNA molecules are labeled using metallic labels that are distinguishable using an electron microscope. These molecules are then stretched on a flat surface and imaged using an electron microscope to measure sequences.
Cartridges and Target Capture Systems
In certain embodiments, target capture systems configured to carry out the processes necessary to isolate a target analyte from a sample without the need for sample preparation or manual operation may be employed. The target capture systems generally include a cartridge and an instrument. The cartridge includes components such as channels, reaction chamber, and reservoirs, etc. configured to perform processes for isolating a target from a sample. The cartridge interfaces with an instrument having one or more assemblies or subsystems, such as mechanical, magnetic, pneumatic, and fluidic assemblies, that interact with the cartridge to assist/drive the processes performed on the cartridge. The systems of the invention are fully integrated to perform several processes on a sample inputted into the cartridge to achieve a final result, such as live cell capture or isolated nucleic acids from a target cell, without user manipulation.
Various embodiments of the target capture system including the cartridge and the instrument and processes performed by the target capture system are described in detail below.
In certain aspects, the processes performed by the target capture systems generally include introducing a plurality of magnetic particles, in which each particle includes at least one binding moiety specific to a target, into a sample to form at least one target/particle complex and applying a magnetic field to isolate the magnetic particle/target complexes from the sample. The process starts at inputting a sample and ends at delivering a capture target (or nucleic acids of the target) into a container for further analysis.
In addition to the methods of target capture described herein, the target capture system may be utilized to isolate pathogens using other methods, including the methods described in co-owned U.S. publication nos. 2011/0263833, 2011/0262925, 2011/0262932, 2011/0262933, 2011/0262926, and 2011/0262927, the entireties of which are incorporated by reference.
In certain embodiments, the processes performed by the target capture systems generally include introducing a plurality of magnetic particles, in which each particle includes at least one binding moiety specific to a target, into a sample to form at least one target/particle complex and applying a magnetic field to isolate the magnetic particle/target complexes from the sample. The process starts at inputting a sample and ends at delivering a capture target (or nucleic acids of the target) into a container for further analysis.
In addition to the methods of target capture described herein, the target capture system may be utilized to isolate pathogens using other methods, including the methods described in co-owned U.S. publication nos. 2011/0263833, 2011/0262925, 2011/0262932, 2011/0262933, 2011/0262926, and 2011/0262927, the entireties of which are incorporated by reference.
In some embodiments, a target capture system may be employed which includes a cartridge that is a single structure having one or more components (such as reagent reservoirs, magnetic traps, storage reservoirs, flow chambers, etc.) that are formed within the cartridge. These components can be connected via channels formed within the system. As such, there is no need for external tubing or other external attachments to connect the components of the cartridge.
A significant advantage of certain embodiments is that the cartridge includes both macrofluidic and microfluidic components and can process macrofluidic and microfluidic volumes of fluids to isolate a target. This accounts for the fact that a minute amount of targets (such as pathogens) may be present in a sample having a macrofluidic volume which necessitates processing the entire macrofluidic volume in order to increase the likelihood that the target will be isolated. To isolate targets in a microfluidic device, the entire macrofluidic volume of sample would have to be transferred slowly or in a piecemeal fashion (e.g. via pipetting) into a microfluidic device at microfluidic rate, which undesirably takes a long amount of time and risks losing the target analyte of interest during the transfer. In certain aspects, the cartridge is designed to consolidate a sample of macrofluidic volume into a concentrated microfluidic volume of fluid that contains target cells of interest. The concentrated microfluidic volume is then processed at the microfluidic level.
Generally, microfluidics relates to small sample volumes and small channel pathways. For example, microfluidic volumes are normally below 1 mL, or on the microliter (μL) scale or smaller, for example, nL (nanoliters) and pL(picoliters). As used herein, microfluidic volumes relate to volumes less than 1 mL. In addition, microfluidics relates to small channel pathways on the micrometer scale. As used herein, microfluidic channels within systems of the invention refer to channels that have channel heights and/or widths equal to or less than 500 μm. See “Microfluidics and Nanofluidics: Theory and Selected Applications,” Kleinstruer, C., John Wiley & Sons, 2013, which is incorporated by reference. The channel height or width is defined as the height or width of the path that the sample volume must pass through within the cartridge. Comparatively, macrofluidics volumes relate to volumes greater than the microliter (μL) scale, for example, sample volumes on the milliliter (mL) scale. As used herein, macrofluidic volumes are volumes of 1 mL or greater. Macrofluidic channels within systems of the invention are channels having channel heights and/or widths of greater than 500 μm.
Other macrofluidic components are chambers, reservoirs, traps, mixers, etc. Such macrofluidic components are dimensioned to hold 1 mL or more of fluid. For example, the individual volume can range without limitation from about 10 to about 50 mL. Other microfluidic components are chambers, reservoirs, traps, mixers, etc. Such microfluidic components are dimensioned to hold less than 1 mL of fluid. For example, the individual volumes can range without limitation from about 1 μL to about 500 μL.
The cartridge includes channels to facilitate transportation of substances and fluids through into, within, and out of the cartridge. The channel generally will include characteristics that facilitate control over fluid transport, e.g., structural characteristics (an elongated indentation) and/or physical or chemical characteristics (e.g. lined with a solution or substance that prevents or reduces adherence aggregation of sample/particulates) and/or other characteristics that can exert a force (e.g., a containing force) on a sample or fluid. The channels can be independent, connected, and/or networked between components of the cartridge. Some (or all) of the channels may be of a particular size or less, for example, having a dimension perpendicular to the flow of fluid to achieve a desired fluid flow rate out of one component and into another. The channels can be designed to transfer macro and micro scales of fluid.
The channels of the cartridge can connect to and interconnect the components of the cartridge. The cartridge can include one or more of the following components: through holes, slides, foil caps, alignment features, liquid and lyophilized reagent storage chambers, reagent release chambers, pumps, metering chambers, lyophilized cake reconstitution chambers, ultrasonic chambers, joining and mixing chambers, mixing elements such as a mixing paddle and other mixing gear, membrane regions, filtration regions, venting elements, heating elements, magnetic traps/chambers, reaction chambers, waste chambers, membrane regions, thermal transfer regions, anodes, cathodes, and detection regions, drives, plugs, piercing blades, valve lines, valve structures, assembly features such as o-rings, instrument interface regions, cartridge/vessel interfaces, one or more needles associated with the sample interface, optical windows, thermal windows, and detection regions. These components can have macro- or micro-volumes.
The cartridge includes at least one inlet for introducing sample into the cartridge and at least one inlet for allowing the instrument to introduce air pressure, e.g., to drive fluid flow, or to introduce fluids into the cartridge. The cartridge further includes at least one outlet to deliver a final product to the operator, e.g. a captured target or nucleic acids of a captured target into a removable vial for further analysis. In preferred embodiments, the inlet and outlet are associated with the cartridge/vessel interface of the invention described in detail hereinafter.
In one embodiment, the cartridge further includes sensing elements to determine the stage of the processes performed within the cartridge. The sensing elements can be used to gauge the flow within the cartridge and the timing for when certain subsystems of the instrument interact with the cartridge. The sensing elements include, but are not limited to, optical sensors (e.g. for monitoring the stage of processing within the chamber), timers (e.g., for determining how long a sample is in a mixing chamber or in a reaction chamber); air displacement sensors (e.g. for determining the volume of fluid within one or more chambers); temperature sensors (e.g. for determining the temperature of a reaction), bubble sensor (e.g. for detecting air and/or volume of fluid within chambers and fluid flow; pressure sensors for determining, e.g., rate of fluid flow. In certain aspects, fluids and substances are driven into, within, and out the cartridge via one or more drive mechanisms. The drive mechanisms can be located on the cartridge itself or located on an instrument in combination with the cartridge. The drive mechanisms provide a means for fluid control within the cartridge and allows for transport of fluid and substances within the cartridge. In addition, the drive mechanisms provide a means for transferring fluids and substances between the cartridge and the vessel at the cartridge/vessel interface. In one embodiment, the drive mechanism is a part of the instrument and is operably associated with the cartridge at one or more cartridge/instrument interface. The cartridge can include a filter at the cartridge/instrument interface to prevent unwanted particles from entering the cartridge from the drive mechanism or instrument. The filter also prevents sample and other fluids from exiting the cartridge at the cartridge/instrument interface. The drive mechanisms of the instrument are discussed in more detail hereinafter.
The cartridge (whether including macrofluidic components, microfluidic components, or both) can be fabricated using a variety of methods, including without limitation, computer numerical control (CNC) techniques, traditional lithographic techniques, soft lithography, laminate technologies, hot embossing patterns, die cutting, polymer molding, combinations thereof, etc. The cartridge can be fabricated from any etchable, machinable or moldable substrate. The term machining as used herein includes, without limitation printing, stamping cutting and laser ablating.
Suitable materials for the cartridge include but are not limited to non-elastomeric polymers, elastomeric polymers, fiberglass, Teflon, polystyrene and co-polymers of styrene and other materials, polypropylene, polyethylene, polybutylene, polycarbonate, polyurethanes, TEFLON (polytetrafluoroethylene, commercially available by the DuPont company), and derivatives thereof. Preferably, the cartridge and the cartridge components are formed primarily from plastic. Plastics are cost-efficient and allow for the cartridge to be economically manufactured at a large scale. As such, the cartridge can be designed as a single use, disposable cartridge.
There are some components of the cartridge that are not plastic, and these components can be formed from, for example, metals, silicon, quartz, and glass. These components include but are not limited to surfaces, glass ampoules, filters, assembly materials (such as screws and other fasteners), electrode pins, membrane, affinity columns, and collection vials.
The cartridge can also include thin film layers that form structures/interfaces (such as walls and valves) on the cartridge, interfaces between components within the cartridge, and interfaces between the cartridge and the instrument. In one aspect, the thin film layers are for bonding fabricated components together (such as CNC components and lithographic components), sealing components together, providing conduits between components, transferring stimulation between components (e.g. capable of transferring physical or mechanical stimulation from an assembly/system on the instrument to a chamber in the cartridge), supporting elements, covering the channel, functioning as a cap and/or frangible seal for reservoirs or chambers, and performing as a valve. The thin film can be elastomeric or non-elastomeric material. In certain aspects, the thin film is a polymer or thermoplastic polymer. Exemplary polymers or thermoplastic polymers can include, but are not limited to, polymers selected from the group consisting of polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinylacetate (PVAc), polystyrene (PS), polypropylene, polyethylene, polymethyl methacrylate, poly(amides), poly(butylene), poly(pentadiene), polyvinyl chloride, polycarbonate, polybutylene terephthalate, polysulfone, polyimide, cellulose, cellulose acetate, ethylene-propylene copolymer, ethylene-butene-propylene terpolymer, polyoxazoline, polyethylene oxide, polypropylene oxide, polyvinylpyrrolidone, and combinations thereof. In addition, thin film can be an elastomer, polymer blend and copolymer selected from the group consisting of poly-dimethylsiloxane (PDMS), poly(isoprene), poly(butadiene), and combinations thereof. In some embodiments, the thin film includes rubber (including silicone) alone or in combination with a polymer.
In a preferred embodiment, the cartridge is pre-assembled prior to shipment to distributors/customers. The pre-assembled cartridge may also include one or more of reagents, capture particles (including magnetic particles), lysing beads, water, and other substances/fluids pre-loaded into one or more chambers or reservoirs formed within the cartridge. The pre-assembled cartridge may be partially pre-loaded, e.g. loaded with only a portion of the components necessary to isolate a target. If pre-assembled, the cartridge can include reagents and magnetic particles specific certain isolation assays and/or specific to certain target analytes. In addition, the cartridge can include magnetic particles with binding moieties specific to a plurality of different targets to provide for isolation of a target when the suspected target is not known. See co-pending and co-assigned U.S. application Ser. No. 13/091,506 that describes compositions for isolating a target sample from a heterogeneous sample. It is also contemplated that the cartridge is partially-assembled prior to shipment to distributors/customers to allow the individual customer to load the cartridge with reagents, beads, etc. that are tailored to the analysis/identification needs of the customer.
As shown in
Along the top of the cartridge 100 are several drive ports 190 at the instrument interface 45. The drive ports 190 connect various features on the cartridge 100 to the instrument's 200 drive mechanism. As shown in
The mixing chamber 170 is in communication with a first magnetic trap 60 and a magnetic trap overflow 50. The first magnetic trap 60, as shown in
As further shown in
Optionally, a pre-magnetic trap chamber 82 is between the first magnetic trap 60 and the second magnetic trap 80 as shown in
The second magnetic trap 80 is configured to engage with a magnet of the instrument to further separate any remaining sample/buffer from the magnetic particles. The second magnetic trap 80 is a flow through chamber in communication with a second magnetic trap overflow chamber 105. The second magnetic trap overflow chamber 105 is used to store unwanted buffer/sample (waste) from the second magnetic trap 80. The second magnetic trap 80 is in communication with a lysis buffer reservoir 90 and optionally, a lysis buffer drip chamber 107 to control flow of lysis buffer into the second magnetic trap 80. The second magnetic trap 80 is also configured to engage with a sonication device of the instrument. In one embodiment, a wall of the second magnetic trap 80 that interfaces with the instrument has a certain thickness, such as 125 μM, that allows vibrations of the sonication device to invoke cell lysis on targets within the second magnetic trap. The wall interfacing the sonication device can be a Mylar film. The second magnetic trap 80 can optionally include binding moieties specific to the magnetic particles to assist in isolating the magnetic particles.
The second magnetic trap 80 is also in communication with a pre-column mixer 85, which receives the lysate from the second magnetic trap 80. The pre-column mixer 85 is in communication with to a nucleic acid binding buffer reservoir and in communication with a nucleic acid extraction column 110. An output chamber 95 can be included between the pre-column mixer 85 and the nucleic acid extraction member 110. Any nucleic acid extraction member 110 that retains extracted nucleic acid while allowing the other fluids such as lysis debris to flow through the member is suitable for use in the invention. The nucleic acid extraction member 110 can be a filter or a column, such as an affinity column. Examples of nucleic acid extraction members are described in, for example, United States Patent Publication No. 2011/0300609.
One or more column wash reservoirs 65 are connected to the nucleic acid extraction member 110 to direct unwanted sample/buffer/ect. from the column 110 to a waste reservoir. An elution reservoir 55 contains a buffer or fluid that is capable of eluting nucleic acids disposed within the nucleic acid extraction member. The fluid, such as water, is flushed from the elution reservoir 55 through extraction member 110 to elute purified nucleic acids into a collection vial (not shown).
In one embodiment, the particle chamber 40, the wash buffer 35, the mixing chamber 70, the first magnetic trap 60 and the magnetic trap overflow 50 of the cartridge 100 are all macrofluidic components designed to process a macrofluidic volume of fluid. Because these components are macrofluidic, the entire sample can be subject to the incubation, agitation, and the first magnetic separation step. After the magnetic particles are isolated in the first magnetic trap 60, a wash buffer flows through the first magnetic trap 60 to transport the separated particles to the second magnetic trap 80. The cartridge 100 components after the first magnetic trap 60 are microfluidic, including the second magnetic trap 60, magnetic trap overflow 105, pre-column mixer 80. The second magnetic trap 80 isolates substantially the entire quantity of magnetic particles within a microfluidic volume of fluid from the macrofluidic volume of fluid. The rate of fluid flow between the first and second magnetic traps can be adjusted to allow for the second magnetic trap 80 to isolate all of the magnetic particles. Thus, the macrofluidic volume of sample is concentrated into a microfluidic volume of concentrated clinically relevant sample. The concentrated microfluidic volume of fluid allows for more efficient nucleic acid extraction.
Cartridge and Vessel Interface
For isolation and detection assays conducted on cartridges or chips (whether microfluidic or macrofluidic), it is important to transfer the entire obtained sample from a collection device into the cartridge to increase the efficiency of isolation or detection. Especially in situations where there is little sample, which is often the case in forensic analysis, or when there is a small concentration of targets per mL of sample (e.g. 1 CFU/mL), which is often the case for pathogenic detection. Cartridges include a cartridge/vessel interface designed to maximize the amount of sample transferred into the vessel and the amount of sample subject to the cartridge processes to avoid loss of clinically relevant within a sample collection device during sample transfer. It is understood that the cartridge/vessel interface can be included on the cartridge of the target capture system and any other cartridge for processing a sample.
The cartridge/vessel interface may include one or more input and/or output members that enter a vessel containing sample to maximize the amount of sample that is transferred from the vessel containing sample into the cartridge for processing. In one embodiment, the cartridge/sample interface includes an inlet member and an outlet member to facilitate communication of fluids and substances out of the cartridge and into the sample vessel and to facilitate communication of fluids and substances (including the sample) out of the vessel and into the cartridge. The outlet member also provides for 1) introducing air to force the sample into the cartridge via the inlet port and/or the inlet member to maximize drainage; 2) introducing a fluid into the vessel to rinse the vessel container to transfer any remaining sample in the vessel into the cartridge; and 3) introducing fluids/substances necessary for cartridge processes directly to the entire sample to ensure the entirety of the sample engages with those fluids/substances. The input member provides for transferring the vessel contents into the cartridge for processing.
In certain embodiments, the fluid is introduced into the vessel at the same time the vessel contents (including sample and/or fluid) is transferred into the cartridge. Alternatively, the sample is at least partially transferred from the vessel into the cartridge prior to introducing the fluid from the cartridge into the vessel.
In one embodiment, both the inlet member and outlet member define a lumen and include a penetrating tip. For example, the inlet member and the outlet member can be hollow pins or needles. The inlet member and outlet member correspond with inlet and outlet ports on the cartridge. The input member and output member are designed to penetrate the vessel containing the sample to place the vessel (and thus the sample) in communication with the cartridge. The communication between the vessel and the cartridge through the input members and output members may be fluidic, pneumatic, or both. The input and output members can also act to couple the vessel to the cartridge and maintain the position of the vessel on the interface. In certain embodiments, the input and output members are in communication with a drive mechanism. The drive mechanism can be a part of the cartridge itself or located on an instrument for use with the cartridge. The drive mechanism can apply air pressure or a vacuum force to facilitate transportation between the vessel and cartridge. For example, the drive mechanism can apply air pressure through a channel of the cartridge, out of the output member, and into the vessel to force the vessel contents to drain through the input member. In addition, the drive mechanism can apply a vacuum force to the input member to force the sample to drain into member.
The input member is in communication with one or more components of the cartridge (e.g. a mixing chamber, magnetic trap, storage reservoir, reagent reservoirs, etc.) that process fluids delivered from the vessel into the cartridge. The input member allows for fluids to transfer out of the vessel and into the cartridge for processing.
The output member is in communication with one or more components of the cartridge (e.g. storage reservoir, reagent reservoir, magnetic trap, etc.) to allow delivery of fluids, substances, and/or gases from the cartridge into the vessel container. In one embodiment, fluid from a reagent reservoir is driven through the output member and into the vessel to rinse sides of the vessel. The fluid may contain one or more substances. In one aspect, the fluid includes capture particles having binding moieties specific to one or more suspected targets within the sample. The fluid can be any fluid that does not interfere with the processes of the cartridge. In another embodiment, the fluid is an essential element of the cartridge processes. For example, the fluid can be a buffer that promotes a reaction within the sample, such as promoting target capture. In addition, fluids, substances, and/or gases may be subject to a reaction/process within the cartridge prior to being delivered into the vessel. For example, a buffer may be heated in the cartridge prior to introducing the buffer into the vessel.
In certain embodiments, one or more input members and one or more output members are inserted into the vessel to place the vessel in communication with the cartridge. This allows, for example, the vessel contents to be directed through one or more input member into one or more different channels in the cartridge for processing. In addition, one or more output members may be for delivering different fluids or reagents into the vessel.
The vessel for coupling to the cartridge interface can be an open or closed container. In one embodiment, the vessel is a collection tube, such as a VACUTAINER (test tube specifically designed for venipuncture, commercially available from Becton, Dickinson and company). Ideally, the vessel is enclosed, such as a collection tube enclosed by a stopper or a plug. The stopper or plug can be rubber, silicone, or polymeric material. For coupling the vessel to the sample, the vessel or the vessel plug is pressed against the input and output member until the input and output member are inserted into the vessel. The cartridge interface can also include a vessel holder to properly position the vessel onto the needles and a locking mechanism to lock the vessel in place while coupled to the cartridge. These features provide a snug fit of the cartridge and the vessel.
Vessels suitable for use with the cartridge can be of any volume size. For example, the vessels can range in volumes from 0.1 to 1 mL to 100 mL. In one embodiment, the vessel has a volume of 10 mL. The volume of the vessel may depend on the sample and the suspected target to be detected. That is, the vessel should be of a sufficient volume to contain an amount of sample fluid in which it is more likely than not that a suspected target is present.
In an embodiment, the output member is positioned within the vessel so that the output member delivers a fluid to the top of the vessel. This causes the fluid to run down at least one side of the vessel and rinse any sample that may have collected along the side of the vessel. The drive mechanism can be set to apply a pressure sufficient to deliver the fluid out of the output member so that it hits the top surface of the vessel. In addition, the input member is positioned within the vessel to promote drainage of the vessel contents. For example, the input member is level with or below the bottom of the vessel. In one embodiment, the vessel or the vessel plug is shaped to drain into the input member. For example, the vessel plug is conically-shaped. In addition, the drive mechanism may provide sufficient pressure to release capture particles out of the output member and into the vessel. For example, pressure from the drive mechanism releases a buffer into a chamber having a plurality of capture particles disposed therein. The buffer/capture particles are then driven from the cartridge through the output member and directly into the vessel. The drive mechanism continues to force the buffer through the particle chamber and into the vessel until all of the capture particles are transferred into the vessel. At the same time, the input member may transfer the sample, buffer, and capture particles out of the vessel and into the cartridge. After substantially all the sample and capture particles are transferred into the cartridge, fluid or the buffer can continue to be introduced into the sample for an additional rinse. In another embodiment, the input member transfers at least a portion of the sample into the cartridge prior to introduction of the capture particles/buffer to provide space within the vessel.
Instrument
In certain aspects, the cartridge interfaces with and is used in conjunction with an instrument. The instrument provides, for example, the pneumatic, fluidic, magnetic, mechanical, chemical functions, as necessary to process the sample within the cartridge. In one aspect, the cartridge is inserted into the instrument for processing and the instrument is turned on by an operator to activate sample processing. Once the cartridge is loaded into the instrument, the system does not require further manual technical operations on behalf of the operator.
In one embodiment, the instrument contains drive mechanisms that connect to the cartridge when inserted into the instrument. Any drive mechanism known in the art may be used with target capture system, including pneumatic drive mechanisms, hydraulic drive mechanisms, magnetic drive systems, and fluidic drive systems. The drive mechanism provides a means for fluid control within the cartridge and allows for transport of fluid and substances between chambers. The drive mechanism can be used to initiate and control fluid flow, open valves, form bubbles (e.g. for mixing) and to initiate mechanical/chemical processes within the cartridge.
The drive mechanism can also be operably associated with a controller so that the controller engages the drive mechanism at certain stages in the pathogen capture process. The controller may engage with one or more sensors to determine when and how to activate the drive mechanism during sample processing. In certain aspects, the controller is a computing system. In certain embodiments, drive mechanism is a pneumatic. The pneumatic drive mechanism can include pumps, electromechanical valves, pressure regulators, tubing, pneumatic manifolds, flow and pressure sensors. Pneumatic drive mechanisms use air pressure and air displacement to control the flow of fluids within the cartridge. In certain aspects, the pneumatic drive mechanism is coupled to electronic regulators. When coupled to an electronic regulator, the pneumatic mechanism may be an external compressor with a reservoir for pumping compressed nitrogen, argon or air.
The instrument also includes one or more magnetic assemblies. The magnetic assemblies engage with one or more magnetic traps (typically, flow-through chambers) of the cartridge. The magnetic assemblies can include permanent magnets, removable magnets, electromagnets, or the like, or combinations thereof. The magnet assemblies may have magnets of various shapes, and of varying strengths, depending on the application thereof. If the instrument includes electromagnets, i.e. magnets that produce a magnetic field upon introduction of an electric current, the instrument may also include a current generator to activate the electromagnets.
Depending on the stage of processing, the magnetic assembly includes one or magnet that are positioned against the cartridge to facilitate capture of one or more magnetic particles on a surface of a magnetic trap. Alternatively, the electromagnets can be prepositioned next to the cartridge and activated by an electric current to facilitate capture of one or more magnetic particles against the surface of the trap.
The size and strength of the magnet(s) of the magnetic assembly should produce a magnetic field suffice to force the magnetic particles within the sample against a surface of the magnetic trap of the cartridge, either macrofluidic or mircofluidic. For example, the magnetic assembly can include 7 bar NdFeB magnets that can be positioned against a magnetic trap of the cartridge. In another example, the magnet assembly includes a magnet with a magnetic flux of about 0.6 T and a magnetic gradient of about 150 T/m. This magnet's high magnetic gradient of about 150 T/m is capable of isolating a plurality of magnetic particles (for example, 1000 magnetic particles) in on a surface with a micro-scale surface area.
The instrument can also include mechanical, electrical, and thermo-electrical systems. For instance, instrument can include mechanical mechanism for engaging with a paddle mixer disposed within in a mixing chamber of the cartridge. The instrument can also include pistons and plungers to activate one or more push valves located on the cartridge. In addition, the instrument can include a heating system designed to control the temperatures of one or more components of the cartridge. For example, the instrument can include a heating apparatus operably associated with the mixing chamber to heat the chamber and encourage binding of one or more magnetic particles with targets contained within the sample. The instrument may include a control processor or a computing system to activate other subsystems, such as the drive mechanism. The control processor can be keyed into sensors designed to track the process through the cartridge. This allows the control processor to activate certain substances based on the location of the fluid within the cartridge or based upon the stage of processing.
The instrument can also include a lysing mechanism for invoking lysis of cells within the sample. The lysing mechanism can include any sonication device that is well-known in the art. In certain embodiments, the sonication device is the VCX 750 Sonicator sold under the trademark VIBRA-CELL (sonicator, commercially available from Sonics and Materials, Inc.). Generally, the probe of the sonicator is placed into the liquid containing the targets to be lysed. Electrical energy from a power source is transmitted to a piezoelectric transducer within the sonicator converter, where it is changed to mechanical vibrations. The longitudinal vibrations from the converter are intensified by the probe, creating pressure waves in the liquid. These in turn produce microscopic bubbles, which expand during the negative pressure excursion and implode violently during the positive excursion. This phenomenon, referred to as cavitation, creates millions of shock waves and releases high levels of energy into the liquid, thereby lysing the target. In another embodiment, the sonication transducer may be brought in contact with a chamber holding captured complexes by way of a structural interface. The sonication transducer vibrates structural interface, such as a thin film between the magnetic trap and the transducer, until lysis is achieved. In either method, the appropriate intensity and period of sonication can be determined empirically by those skilled in the art.
As shown in
As shown in
In
Once the sample/particle/buffer mixture is transferred from the vessel 10 to the mixing chamber 70 as shown in
After incubation/agitation, the sample/particle/buffer mixture is cycled through the first magnetic trap 60, as shown in
After the final cycle of fluid through the first magnetic trap 60, the remaining fluid (sample/buffer) separated from the captured magnetic particles is moved into the mixing chamber 70 and stored as waste. Alternatively, the remaining fluid can be transferred to a designated waste chamber.
The captured particles within the first magnetic trap 60 are then subject to a wash process as shown in
As shown in
The second magnetic trap 80, as engaged with the magnetic assembly, captures magnetic particles as the fluid flows from the first magnetic trap 60 through the second magnetic trap 80 and into a waste chamber 105. Pressure from the drive mechanism is applied to ensure all the fluid/magnetic particles are transferred into the magnetic trap and to prevent any fluid back flow. The rate of the fluid flow can be controlled to ensure all magnetic particles are capture while the fluid flows through the second magnetic trap 80. In one embodiment, the rate of fluid flow is 1 mL/min. In one aspect, the second magnetic trap 80 has a significantly smaller volume than the first magnetic trap 60 which allows the second magnetic trap 80 to concentrate the substantially the entire quantity of particles initially introduced into the sample into a small volume of fluid. The high concentration of particles in a small volume of fluid provides for easier downstream analysis of or processes performed on targets bound to those particles. That is, the target capture system is able to isolate the clinically relevant portion of a macrofluidic fluid volume in a microfluidic fluid volume. In one embodiment, the first magnetic trap 80 is macrofluidic (volume capacity above 1 mL) and the second magnetic trap is microfluidic (volume capacity below 1000 μL). For example, the first magnetic trap 60 has a macrofluidic volume for processing 30 mL of fluid to initially capture magnetic particles disposed within the 30 mL of fluid and the second magnetic trap 80 has a microfluidic volume of 500 L of less.
After the magnetic particles are concentrated in the second magnetic trap 80, the captured particles can be directed to a capture vial or subject to further processing.
After lysis by sonication is complete, the lysate can be forced into a pre-column mixer 85 as shown in
The nucleic acid extraction matrix 110 can then be subject to one or more washes. As shown in
After the washes, the nucleic acid extraction matrix 110 can be eluted with a fluid from the elution reservoir 55. In one embodiment, the fluid is water. The drive mechanism uses high air pressure to force the fluid through the nucleic acid extraction matrix 110 into a nucleic acid capture vial 180 (SEE
References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.
Various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of this document, including references to the scientific and patent literature cited herein. The subject matter herein contains important information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and equivalents thereof.
The present application claims the benefit of and priority to each of U.S. provisional patent application Ser. Nos. 61/739,612 filed Dec. 19, 2012, and 61/739,644, filed Dec. 19, 2012, the content of each of which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61739644 | Dec 2012 | US | |
| 61739612 | Dec 2012 | US |
