The present invention relates to a nucleic acid amplification system using magnetic or non-magnetic nanoparticles that converts external energy into localized thermal energy by integrating photothermal heating, thereby performing nucleic acid amplification via polymerase chain reaction or isothermal amplification on the surface of the nanoparticles. In addition, the nanoparticles can be concentrated by single-molecule concentration procedures, such as centrifugation, magnetic capture, and lateral flow chromatography. The amplified target nucleic acids are detected by nucleic acid tags or antibodies, coupled with enzyme reactions, and followed by a colorimetric method to achieve rapid detection.
For molecular biological detection of the trace nucleic acids from crude clinical samples, rapid nucleic acid amplification, and subsequent detection is the challenging bottleneck. In the past decade, owing to the manipulation of ultrafast thermal cycling and the second-generation DNA polymerase, rapid polymerase chain reaction (PCR) was demonstrated to be achieved within a few minutes. However, rapid PCR is also accompanied by many problems (i.e., low yield of the amplicons, scalability of the platform, and thermal management of the platform on thermal cycling). Rapid nucleic acid amplification and detection is the core technology of nucleic acid-based point-of-care testings (POCTs). As compared to conventional PCR instruments, the microfluidic-based nucleic acid platform is demonstrated that it is more technically superior, and is also widely used in the detection of trace nucleic acid samples. Although a portable Micro Electromechanical Systems (MEMS)-based microfluidic analysis device is implemented, such platforms need to be requires precise temperature control and microfluidic system operation. Therefore, it has relatively increases difficulty in design, process and operation in the microfluidic chips, and restricts for the development and the POCTs application. The subsequent nucleic acid detection technologies mostly depend on physical or chemical properties of labeled tags in target amplicons of nanoparticles, e.g., absorbance, fluorescence, concentration, electrical impedance, and even fluid viscosity, etc.
In the identification of cells, bacteria, or viruses, and even the screening of cancer cells such as the trace circulating tumor cells in the blood circulation system. Identification of specific antigens on the cell surface also plays an important role in the identification of cell markers. However, for circulating tumor cells, cell markers such as EpCAM or CKs would not be expressed on all circulating tumor cells. In addition, in the identification of some RNA viruses with high mutation rates on the structural protein. In conventional immunological-based POCTs application is restricted by the availability of corresponding antibodies detectable with high specificity and sensitivity, screening suitable monoclonal antibodies that are specific against unique antigens is time-consuming. Therefore, nucleic acid-based POCT detection is superior to immunological-based POCT detection. Moreover, nucleic acid based detection can increase the concentration of the target amplicons through nucleic acid amplifications to improve the analytical sensitivity for subsequent detection.
For instance, if screening for specific cancer cells, bacteria, or viruses is necessary, most existing technologies need an extra and complicated procedure to release antigens or nucleic acids from target cells. Even if nucleic acids or antigens are released, it is more likely that low target cell concentration is too low in samples, resulting in analytical devices (e.g., biochips) need to accumulate sufficient target analytes to perform their functions.
Therefore, relevant biological detection often requires multiple steps, such as screening, cultivating, controlling the concentration of samples, selecting appropriate detection instruments, and finally performing data analysis, resulting in many difficulties in instrument integration. Currently, a set of systems and methods that can solve the problems mentioned above without losing detection accuracy is needed.
In order to solve the problems mentioned in the prior art, the present disclosure provides a nucleic acid amplification system and a method thereof, wherein the thermal cycling of the nucleic acid amplification is performed in a thermal conduction method instead of using a metal heating carrier or a cooling fan.
The nucleic acid amplification system mainly comprises a reaction space, a sample, a plurality of particles, at least one enzyme, at least one energy supply module, at least one temperature equilibrium substance, and an operating module.
The sample includes at least one analyte, placed in the reaction space. The plurality of particles mixed with the sample, each including a body, at least one first ligand, and at least one second ligand. The at least one first ligand is functionalized on the body, matching the at least one analyte. The at least one second ligand is functionalized on the body, and each second ligand contains a specific tag.
At least one enzyme is mixed with the sample. At least one energy supply module provides external energy to the plurality of particles. At least one temperature equilibrium substance is placed in the reaction space for balancing the temperature of the plurality of particles. The operating module is used to control the plurality of particles in the reaction space.
Further, the method for operating the acid amplification system described in the present disclosure mainly includes seven steps, comprising the steps of: step (a) mixing the sample and the plurality of particles, so that the plurality of particles captures the at least one analyte; step (b) using the operating module to concentrate the sample in the reaction space, wherein the sample includes the at least one analyte, and wherein step (e) immediately follows the step (b) if the at least one analyte is a cell-free nucleic acid, otherwise, proceed to step (c); step (c) in which the at least one energy supply module provides an external energy to the plurality of particles, so that a temperature of the plurality of particles rises to a thermolysis temperature; then proceed to step (d) at least one analyte will be lyzed, thereby releasing at least one biological substance; and followed by step (e) the at least one energy supply module provides the external energy to the plurality of particles up to a hybridization capture temperature, so that the particles is bound to the at least one biological substance or the cell-free nucleic acid; and step (f) providing the external energy to the plurality of particles up to an amplification temperature with the at least one energy supply module, and then using the enzyme to amplify the at least one biological substance or the cell-free nucleic acid on the particles, so that the amplicons generated from at least one biological substance or the cell-free nucleic acid that is tethered with the plurality of particles. In this reaction, at least one temperature equilibrium substance is used to cool down the plurality of particles, thereby maintaining the temperature range for isothermal amplification or achieving rapid temperature cycling.
In one embodiment of the method for performing the nucleic acid amplification system as described in the present disclosure, after step (f), further comprising step (g); wherein step (g), wherein a detection module is used to detect a colorimetric change, a luminescence or a combination thereof caused by the specific tags on the at least one biological substance or the cell-free nucleic acid that is amplified, so as to detect the at least one biological substance or the cell-free nucleic acid, which is amplified, on the plurality of particles that is concentrated. Using the detection module to analyze the difference of the fluorescence intensity, wherein the detection module is a fluorescence detection device (e.g., fluorometer or a fluorescent scanner) or a spectrophotometric detection device; or by using the specific binding DNA fragments or antibody-coupled enzyme reactions to detect the specific tags on the biological substance amplified by the polymerase.
The purpose of the brief description of the present disclosure mentioned above is to provide a basic description of several aspects and technical features of the present disclosure. The brief description is not a detailed description of the present disclosure. Therefore, the purpose of the description is not to specifically list the key components or important components of the present disclosure, nor to define the scope of the present disclosure, but to demonstrate several concepts of the present disclosure in a concise manner.
In order to illustrate the technical features and practical effects of the present disclosure, and to enable those having ordinary knowledge of the art of the present disclosure to carry out the implementation according to the content of the specification of the present disclosure, the preferred embodiment shown in the drawings is further described in detail.
First of all, referring to
In this embodiment, the sample 200, the plurality of particles, and the polymerase 400 are all placed in the reaction space 100, and the sample 200 in the reaction space 100 further comprises a temperature equilibrium substance. The temperature equilibrium substance comprises a large volume (greater than or equal to 100 μL) of nucleic acid amplification solution or an ice pack externally in contact with the reaction space. The ice pack comprises ice or high molecular polymer water-absorbent resin (i.e., carboxymethyl cellulose) with high specific heat capacity. The plurality of particles is the plurality of magnetic nanoparticles. The temperature of the microenvironment around the of particles is heated by magnetic nanoparticles 300 through photothermal reaction and is rapidly cooled down by the temperature equilibrium substance, therefore, it can maintain a constant temperature range for performing isothermal NAATs or achieve the ultrafast thermal cycling for PCR by controlling NIR laser irradiations and assistance of temperature equilibrium substance.
In this embodiment, the sample 200 includes at least one analyte 201 to be tested, and the sample 200 is placed in the reaction space 100. Specifically, the sample 200 referred to in this embodiment can be any biological fluids or its corresponding supernatants used for biological detection (e.g., serum, plasma, urine, lymph, throat swab, nasopharyngeal swab, bronchoalveolar lavage fluid, sputum, feces, cerebrospinal fluid, skin blister fluid, and scabs, or a combination thereof). Moreover, the sample 200 is pre-extracted samples of food or processed agricultural products, or a combination thereof. Furthermore, the sample 200 used in the present disclosure can be a purified sample or a sample without preliminary purification and pretreatment. Regardless of the conditions of the sample 200, the nucleic acid amplification system 10 shown in this embodiment can perform photothermal heating to lyze the analyte 201 to be tested. The analyte 201 is any individual microbes, tissues or cells. The analyte comprises at least one cell, at least one organelle, at least one bacterium, at least one algae, at least one protozoa, at least one fungus-like protist, at least one fungus, at least one virus, at least one phage, at least one cell-free nucleic acid, or a combination thereof, wherein the at least one cell-free nucleic acid further comprises at least one cell-free nucleic acid derived from body fluids, tumors or a combination thereof. The foregoing descriptions are examples only, and the present disclosure is not limited thereto.
In this embodiment, the plurality of magnetic nanoparticles 300 is mixed with the sample 200. Referring to
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In this embodiment, the first ligand 302 and the second ligand 303 are specifically designed to analyze a trace analyte 201 in the sample 200. In this embodiment, each first ligand 302 and each second ligand 303 are connected to the body 301 through a stabilizing bond 304. The stabilizing bond 304 comprises a thermostable bond, a contact inhibition coating or a combination thereof. Moreover, the thermostable bond further comprises biotin-streptavidin interaction, the connection of a chemical cross-linker, or other covalent bonds with thermostable properties. Because the combination of streptavidin and biotin has extremely high thermal stability (>105° C.) at its saturated state, and its preparation method is simple. Therefore, the biotin-streptavidin interaction provides high-specificity and high-affinity characteristics on ligand modification, and a stable bonding can endure the high-temperature ranges during PCR cycle. In contrast, the prior art generally uses thiol-modified ligands to form a stable disulfide bond (—S—S) on gold nanoparticles, however, the appearance of dithiothreitol (DTT) or other reducing agents in the PCR reaction solution can lead to loss of thiol-modified ligand functionalization. In the presence of dithiothreitol (DTT) or other reducing agents, the stable disulfide bridge is easy to reduce to a sulfhydryl group (—SH status), causing the ligands to be detached from the surface of nanoparticles during the PCR procedure. In addition, the streptavidin forms a protein coating layer on the surface of the nanoparticles to reduce the non-specific adsorption of nanoparticles.
In this embodiment, the polymerase 400 is also mixed with sample 200. The polymerase 400 is deoxyribonucleic acid polymerase (DNA polymerase), ribonucleic acid polymerase (RNA polymerase), or a combination thereof. According to the type of nucleic acid to be detected or the type of the second ligand 303, the polymerase 400 can be replaced, which is not limited by the present disclosure. Moreover, the enzyme further includes reverse transcriptase (RT), ribonuclease (RNase), helicase, DNA ligase or a combination thereof, which can be used according to types of sample 200 or nucleic acid amplification reactions. The type of enzyme can be changed depending on the situation.
In addition, in this embodiment, in order to reduce the contact inhibition between the surface of the body 301 and DNA polymerase or RNA polymerase, the surface of the body 301 is modified with the contact inhibition coatings. The contact inhibition coating comprises silica coating, polyethylene glycol (PEG) or a combination thereof. The contact inhibition coating is used as a filling molecule on the surface of the body 301 to reduce aggregation between magnetic nanoparticles 300 and improve the stability of the surface of the magnetic nanoparticles 300.
In this embodiment, the at least one energy supply module 500 comprises a laser transmitter, a light-emitting diode or a magnetic field generator, thereby providing an external energy B to the plurality of magnetic nanoparticles 300. The types of external energy B comprise light energy or alternating magnetic fields (AMFs). In this embodiment, the external energy source B (refer to
In the present disclosure, the nucleic acid amplification system 10 can further comprise a detection module that detects the specific tags in each of the at least one second ligand of the plurality of particles concentrated by the operating module. In one embodiment, the detection module is used to detect the fluorescence F generated from the fluorescent group 3061 on the at least one second ligand 303 of the plurality of magnetic nanoparticles 300 concentrated by the operating module. The biological substance 202 from the analyte 201 that is amplified on the surface of the plurality of magnetic nanoparticles 300 is quantified. In this embodiment, the biological substance 202 is DNA or RNA, but not limited thereto.
When the biological substance 202 is a nucleic acid, in-situ polymerase chain reaction (in-situ PCR), reverse transcription or isothermal amplification will be used for nucleic acid amplification. Isothermal amplification refers to nucleic acid amplification technology with an operating temperature greater than 37° C. Isothermal amplification technology comprises loop-mediated isothermal amplification (LAMP), strand displacement amplification (SDA), Helicase-dependent amplification (HDA), nucleic acid sequence-based amplification (NASBA), and transcription-mediated amplification (TMA), nicking enzyme amplification reaction (NEAR), recombinase polymerase amplification (RPA).
Amplification of nucleic acid, that is, after the analyte 201 is lyzed and releases the biological substance 202, and then the biological substance 202 is amplified through the nucleic acid amplification, which is called the amplicon.
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Step (c) in which at least one energy supply module 500 provides the external energy to the plurality of magnetic nanoparticles 300, so that a temperature of the plurality of magnetic nanoparticles 300 rises to a thermolysis temperature; step (d) the at least one analyte 201 is lyzed, thereby releasing at least one biological substance 202; step (e) in which the at least one energy supply module 500 provides the external energy B to the plurality of magnetic nanoparticles 300 up to a hybridization capture temperature, so that the second ligands 306 of the plurality of magnetic nanoparticles 300 are bound to the at least one biological substance 202 or the cell-free nucleic acid through the operating module; and step (f) providing the external energy B to the plurality of magnetic nanoparticles 300 up to an amplification temperature with the at least one energy supply module 500, and then using the polymerase 400 to amplify the at least one biological substance 202 or the cell-free nucleic acid on the plurality of magnetic nanoparticles 300; step (g) after concentration with the operating module, the signal readouts of amplicons on the plurality of particles are measured with a detection module to through a colorimetric change, a luminescence or a combination thereof generated by the specific tags in the at least one biological substance 202 or the cell-free nucleic acid.
In order to more clearly illustrate the method of the nucleic acid amplification system 10 described in this embodiment, please refer to
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The energy supply module 500 of the above-mentioned embodiment is a laser transmitter, and the type of external energy B is laser light. However, depending on the chemical material properties and physical size and shape of the body 301, different types of energy supply module 500 must be chosen. The function of energy supply module 500 mainly provides an energy transfer capable of heating the body 301.
The laser wavelength ranges mainly from the visible light spectrum to the near-infrared light spectrum (380 nm-1.4 μm), preferably, the laser wavelength is in the near-infrared spectrum region (750 nm-1.4 μm). The magnetic nanoparticles 300 convert the external energy B into thermal energy. The external energy B can be light energy, alternating magnetic field and other energy sources, which are not limited in the present disclosure. In this embodiment, the energy supply module 500 mainly heats the magnetic nanoparticles 300 itself and the microenvironment. The distance of the microenvironment is in micrometers (μm) around the magnetic nanoparticles 300, so it is more suitable for in-situ polymerase chain reaction (in-situ PCR).
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In this embodiment, the biological substance 202 is DNA or RNA. Referring to
In this embodiment, since the biological substance 202 is DNA or RNA, the second ligand 303 is correspondingly selected as a short strand of DNA or RNA or its modified derivatives complementary to the biological substance 202, so that to bind with at least one biological substance 202.
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In step (F), the energy supply module 500 provides external energy B to the plurality of magnetic nanoparticles 300 in the reaction space 100 until the plurality of magnetic nanoparticles 300 reaches an amplification temperature for nucleic acid amplification. And then, the captured biological substance 202 on magnetic nanoparticles 300 will be used as a template for performing nucleic acid amplification with the polymerase 400. During the DNA amplification, the specific nucleic acid tags (e.g., fluorescent group 3061 or nucleic acid tag 3062) incorporate into amplicons, resulting in the signal readout changes of fluorescence intensity and colorimetric changes caused by fluorescent group 3061 and the nucleic acid tag 3062 coupling antibodies or enzymes. In this embodiment, the temperature equilibrium substance is a large volume (greater than or equal to 100 μL) of the PCR reaction solution. Since the temperature equilibrium substance has large heat capacity, it can quickly cool down the plurality of magnetic nanoparticles 300, so that the ultrafast thermal cycling is achieved to perform nucleic acid amplification.
In this embodiment, if the polymerase 400 has been added during the step (b), the polymerase 400 is selected as DNA polymerase, RNA polymerase, or reverse transcriptase according to the type of at least one biological substance 202, so that the nucleic acid amplification in the step (f) can be performed. It is also possible to add polymerase 400 during steps (e) to step (f). The addition time of polymerase 400 is not limited in the present disclosure.
Compared with the prior art, since the photonic in-situ PCR is performed on the surface of magnetic nanoparticles 300. Therefore, the amplicons are mostly present on the magnetic nanoparticles 300 through second ligand 303. Since the carrying capacity of the surface of the plurality of magnetic nanoparticle 300 is far less than the carrying capacity of the reaction space 100, the single strand amplicons and amplicons are present in a very small amount in the reaction space 100. Moreover, the limited carrying capacity of amplicons on magnetic nanoparticles 300 means that those can reach amplicon saturation at a relatively small nucleic acid amplification cycle.
Finally, step (g) is carried out through a detection device, in this embodiment, it can be a fluorometer or a fluorescent scanner to analyze the differences in the fluorescent intensity. In addition, the detection device can also be a spectrophotometric detection device, which is used to detect the colorimetric changes caused by the combination of nucleic acid tag 3062 or antibody-coupled enzyme reactions. The nucleic acid tag 3062 can be recognized by a specific antibody, and then the enzyme coupling on the antibody will convert colorless substrates into products with a specific color. Therefore, the colorimetric changes are analyzed by using the colorimetric method to detect the biological substance 202 that is amplified by the polymerase 400.
The intensity changes of fluorescence F or colorimetric changes caused by nucleic acid tag 3062 incorporation in amplicons can be referred to
As mentioned above, there are several embodiments for signal detection of amplicons with fluorescence F incorporation on the magnetic nanoparticles 300 and are not limited thereto. The fluorescence detection method and the primer labeled with the fluorescent group 3061 are utilized In one of the preferred embodiments. In this embodiment, the fluorescent group 3061 can be selected from fluorescein isothiocyanate (FITC). In this embodiment, a pair of free nucleic acid primer 306 (F3 primer and B3 primer) are provided to specifically bind to the malB gene of E. coli. Among them, the F3 primer has extra modifications (e.g., biotin or amine and T20-PEG6 spacer at the 5′ end and internal sequence) for binding to the magnetic particles 300 through streptavidin-biotin interaction or covalent bond formation (e.g., cross-linking between a carboxylic group and an amine group), respectively. The biotin or amine-modified F3 primer at the 5′ end can form a stable bridge with the bodys 301 through streptavidin-biotin interaction or covalent bond formation. The 5′-terminal of the B3 primer is labeled with FITC to form a FITC-B3 primer. The fluorescent group 3061 and the free nucleic acid primer 306 can be selected according to different detection requirements. The present disclosure is not limited thereto.
In summary, based on the aforementioned description, in this embodiment, the photonic in-situ PCR is performed, and the amplicons labeled with fluorescent groups 3061 are generated on the surface of magnetic nanoparticle 300, as for the free FITC-labeled B3 primer can be removed through the procedures of magnetic separation and washing. The amplicons labeled with FITC on the magnetic nanoparticle 300 can be further concentrated by magnetic force (or combined with centrifugal means), and the signal of fluorescent F on the surface of the magnetic nanoparticle 300 will also be enhanced for further fluorescence intensity detection. Owing to the size of the amplicon (e.g., about 100 bp/30 nm) on the magnetic nanoparticle 300, The amplicon forms an appropriate spacer between fluorescent group 3061 and the surface of the magnetic nanoparticle 300, allowing fluorescence intensity of the fluorescent group 3061 enhanced through metal-enhanced fluorescence (MEF) effect. The fluorescent F intensity of amplicons can be analyzed by the fluorescence scanner or fluorescence spectrometry.
In one embodiment, we use a lateral flow dipstick to detect the amplicons labeled with the fluorescent group 3061 or a nucleic acid tag 3062 on the magnetic nanoparticles 300. The detection method is slightly different from the conventional gold nanoparticle-based lateral flow immunoassay. The conventional lateral flow test used specific antibody-functionalized gold nanoparticles as detection particles with unique optical properties. However, in this embodiment, specific antibody-functionalized gold are not used in the lateral flow dipstick, instead, magnetic nanoparticles 300 are used as optical makers in the lateral flow dipstick, and the capture antibodies specific against fluorescent group 3061 or nucleic acid tag 3062 are used, those are dispersed and immobilized on the region of detection line of test membrane. When the liquid samples containing the target amplicons labeled with fluorescent group 3061 or nucleic acid tag 3062 on the surface of magnetic nanoparticles 300, with liquid samples migrate along the strip into the detection zone, the target amplicons will be immobilized on the test line to generate an optical signal; while the control line will only immobilize the first ligand 302 which recognizes the magnetic nanoparticle 300 itself.
In addition to the above-mentioned embodiment of detecting fluorescence F signal, there are further other detection methods, comprising bead-based ELISA, litmus test, and other methods, which are not limited thereto. The bead-based ELISA is to improve the sensitivity of the detection method or to convert the fluorescence F signal into the detection signal for detection by colorimetric method. The antibody coupled with enzyme is used in bead-based ELISA, and the antibodies include that those can specifically recognize the fluorescent group 3061 (e.g., FITC) or nucleic acid tags (e.g., digoxigenin, biotin) labeled in amplicons, and the coupled enzymes include horseradish peroxidase (HRP) and alkaline phosphatase (AP). The substrates for HRP are included 3,3′,5,5′-tetramethylbenzidine (TMB), (2,2′-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium salt (ABTS), and o-phenylenediamine dihydrochloride (OPD). The substrates for AP are included p-Nitrophenyl Phosphate (PNPP), those colorless substrates are converted into products with specific colors by HRP or AP. In this embodiment, the bead-based ELISA uses anti-FITC-coupled with HRP and TMB substrates for performing colorimetric detection at A450nm.
The Litmus test has a similar working principle to the aforementioned bead-based ELISA. However, the litmus test does not use antibodies for specific amplicon detection. In the Litmus test, the modified primers are used to perform the photonic in-situ PCR, the reverse primer contains a target binding sequence and an extra sequence (i.e., UrD binding tag) that is designed to hybridize with the DNA strand coupled onto urease (i.e., UrD). The amplicons labeled with UrD binding tag on the magnetic nanoparticles can be recognized with the UrD. The urease of UrD catalyzes the hydrolysis of urea into ammonia, resulting in the increase of the pH value in the reaction solution. The pH value change of the reaction solution can be further detected by an acid-base indicator (e.g., phenol red, cresol red, or cresol purple), especially the acid-base indocator within pH7 to pH9, the readout of the amounts of amplicons on the magnetic nanoparticles 300 can be converted to colorimetric change for detection.
Based on the above-mentioned descriptions, the embodiments of the present disclosure not only overcome multiple limitations (e.g., removal of inhibitors originating from biological samples, concentration procedure for trace target analytes, sample 200 pretreatment in a single reaction space 100), but also enable the magnetic nanoparticles 300 to have capabilities, (e.g, specific capture ability of the analyte 201 and biological substance 202, photothermal conversion ability, and magnetic properties). Therefore, the magnetic nanoparticle 300 simultaneously functions as a heater and a carrier, so that it can rapidly and visually identify whether the analyte 201 exists in the sample 200. In addition, by controlling the NIR laser modulations and the temperature equilibrium substance in the sample 200, the constant temperature for photonic in-situ LAMP or ultrafast thermal cycling for photonic in-situ PCR can be achieved within a short turnaround time, which solves the time-consuming issue of molecular diagnostics.
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Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except by the appended claims.
The present application is based on, and claims priority from, international application number PCT/CN2020/131461 filed Nov. 25, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/CN2020/131461 | 11/25/2020 | WO |