1. Field of the Invention
The present invention relates generally to high throughput biological assay devices, and particularly to capillary tubes in high throughput biological particle-based assay devices.
2. Technical Background
Particle-based assays are known. With particle-based assays, biomolecular reactions take place either on the surface of microscopic beads called microspheres or microscopic bars called microrods (typical sizes are in the submicron and micron ranges). In order to use the particle-based assays to study the biomolecular reactions, for each reaction, a number of molecules are first immobilized or attached to the surface of the particles. These attached molecules are typically called probes. A sample solution containing target molecule(s) is applied to each well or tube and mixed with the “treated” particles. A target or analyte presented in the sample reacts with the probe molecules. In general, the target molecules or a reference molecule co-exited with the targets in the sample are tagged with an optically active compound, of which the fluorescence or luminescence is increased during the reaction between the target molecules (or the reference molecules) and the probe molecules, for example. A qualitative and/or quantitative analysis of the composition of the sample fluid can thus be carried out by illuminating and optically scanning the contents of the wells. In a multiplex assay format, the particles are either internally color-coded or are coded with different predefined color or reflective pattern, as in a color stripe of a bar-coded rod or are synthesized with built-in infrared (IR) and Raman spectroscopic barcodes such that multiple reactions can be performed in a single tube or well. In this case, there are two sources of information, the predefined pattern inside the particles to identify the type of reaction and the reporter color on the surface of the particles to signal the magnitude of the biomolecular reaction.
Particle-based assays typically consist of multiple wash cycles, different phases of incubations, and data analysis. Among other complex methods, the assays are typically performed either in filter-bottomed microplates, such as available from Millipore Corporation, Bedford, Mass., as part Cat. #MABVN-1210 or in centrifuge tubes. When using the filter-bottomed microplate, wash cycles and incubations are carried out in each well of the microplate. Reagent or sample (target molecules) is added to each well containing the particles and after each step, the solution is removed from wells via vacuum using a filtration manifold (e.g., Millipore Corporation, Bedford, Mass., Cat. # MAVM09601). The wash and incubation are repeated until the assay is completed. If centrifuge tubes are used, washing is performed manually by first centrifuging the particles in tubes followed by completely aspirating the solution from the tubes which is done by gently lowering an aspiration tip (aspiration device) into the bottom of each tube. Care has to be taken not to aspirate the particle pellet. After aspiration, the wash and incubation are repeated until the assay is completed. In a multiplex assay format, different particles from different wells or tubes are removed and mixed into a single tube or well after the first phase of washing and incubation. Then, additional wash cycles and incubations are performed to complete the assay. In both approaches, the multiple wash cycles and incubations are labor intensive and particle loss is a concerned when performing particle-based assays.
At the completion of the assay, to analyze the test result, the particle mixture is removed from the wells or tubes and is injected into a flow cytometer that aligns the particles in a single file where lasers illuminate the colors on the surface of each particle. In the case where there are predefined pattern inside the particles, a custom-made instrument (such as a modified flow cytometer) is required with an extra laser illuminates the pattern inside the particles to identify the type of reaction. Next, advanced optics capture the color signals. Finally, digital signal processing translated the signals into real-time, quantitative data for each reaction. Alternatively, particles are isolated and dried from the particle mixture. They are then scanned with a scanner and/or imaged with an optical microscope for data analysis. Clearly, both techniques require additional handling and transferring of the particle mixture. It may lead to particle loss and hence a large number of particles may be required. In the drying technique, it is very difficult to prevent particles from stacking to form a monolayer which will affect data analysis. Also, complicated fluid handling is required in such conventional techniques which do not provide an efficient method of preparing the particles for imaging or scanning for data analysis.
Low-pressure filter assemblies are available in the market. However, the main disadvantage of the existing products is that they are not transparent which will prevent the data analysis of the particles through scanning and imaging. Also, low-pressure filter assemblies are made from polymer which may not be biocompatible and may not be able to resist heat or solvents. Therefore, a tool for conveniently performing particle-based assays with minimal sample, minimal particle loss or human handling is desired.
Furthermore, genetic testing is another area that the present invention is intended for. Two key steps in genetic testing procedures, cell isolation and nucleic acid amplification reactions, have been demonstrated in a computer numerical control-machined Plexiglas-based microchip module comprising of a custom-made heater-cooler for thermal cycling, a series of microchannels for transporting human whole blood and reagents in and out of a dual-purpose glass-silicon microchip (Yuen et al., Genomic Research, 2001, 11, 405-412). The cell isolation and polymerase chain reaction (PCR) were preformed inside the dual-purpose glass-silicon microchip containing a series of 3.5 m feature-sized weir-type filters, formed by an etched silicon dam spanning the flow chamber. Although the microchip module was demonstrated to be an effective tool for integrating the cell isolation and PCR, it requires laborious steps of fabricating the glass-silicon microchips which have to be fabricated in a clean room environment. Also, each component of the microchip module has to be fabricated separately and then assembled together before use. Thus, an alternative method to the microchip module that can overcome the shortcomings of the microchip module would be valuable and attractive.
One aspect of the invention is a microfluidic reactor for trapping one or more particles of predetermined nominal size or range of sizes that have entered a flow inlet which includes a transparent reaction zone for also serves as an in-situ detection zone wherein the detection zone is arranged so as substantially to correspond in shape to an optical detector. A porous filter having a plurality of holes being smaller than the nominal size or range of sizes of the particles are arranged so as to trap the particles in the reaction zone while a fluid flows from the flow inlet through the reaction zone and the filter.
In another aspect, the present invention includes the integration of a plurality of smaller capillaries to a larger capillary to form a filtered capillary tube as the microfluidic reactor.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operations of the invention.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. One embodiment of the microfluidic reactor of the present invention is shown in
Both the inside and outside surfaces of the capillary tube can be of any suitable shapes to provide an imageable surface for a detector. For example, a circular, square or rectangular inner channel can be provided by a capillary tube to form the reaction zone 14 that is integrated with the porous filter 16. Preferably, the cross-sectional shape of the capillary tube is either square or rectangular, both inside and outside to correspond with the shape of the detector 456 used in
Within the filtered capillary tube for providing the microfluidic reactor 10, particle-based assays involving multiple wash cycles, different phases of incubations, and data analysis can be conveniently performed with minimal particle loss and human handling. Examples of possible particle-based assays include DNA hybridization, immunoassay, enzyme\substrate activity, etc.
A single rectangular capillary filtered tube is shown for simplicity in
Instead of microbeads, the particles 200 could also be cells, such as blood cells or other biological molecules to be analyzed. In this case, the capillary filtered tube can be used to isolate white blood cells from the human whole blood where the red blood cells will pass through the filter during the isolation (Yuen et al., Genomic Research, 2001, 11, 405-412). Then, polymerase chain reaction (PCR) can be performed with the white blood cells inside the capillary filtered tube. Thus, another embodiment of the present invention is in the field of genetic testing for performing cell isolation and nucleic acid amplification reactions, as one type of possible analysis.
Referring to
The particles 100 or 200 are homogeneously doped or spatially patterned with various combinations of rare earth (RE) elements A, B, C, or D, for example, in a glass or ceramic host to provide the codes 0, 1, 2, 4, or 8 for example to form the final particles 200′, 201, and 202 in
The porous filter can be made of glass, polymers, metal or any other material as long as the material is porous to allow fluids to flow through but captures particles. The plurality of holes can be of any shape, such as rectangular, hexagonal, circular, square, etc, patterned or randomized. Normally, the size of the filter is designed small enough to block the flow of the larger microsized particle 200. But in other applications, the filter can be made even smaller to capture the smaller nanosized particle 100.
Instead of being rectangular as shown in
Referring to
Referring to
Another method of production is to insert a longer piece of microstructured fiber that would extend from one or both ends of the capillary tube. The fiber could be scribed at one or more locations, allowing it to be easily and cleanly broken after the collapse process, leaving only a short piece fused inside the tube. The pressure inside the microstructured fiber could be placed under the same vacuum as that inside of the tube, or its pressure could be varied.
Prototypes were fabricated using Corning's Photonic Crystal Fiber with an outer diameter of 525 μm, 20 μm holes and 21.4 μm pitch as the filter 16 fused inside a glass capillary tube with an outer diameter of 2.65 mm and an inner diameter of 540 μm. The capillary tube was collapsed using a Methane/Oxygen flame from a 12-port, 5/16″ ring burner and a 15″ Hg vacuum, producing a 3-4 mm collapse region where the tube is fused to the fiber. The periphery of the integrated filtered capillary tube can be left circular or sliced or otherwise shaped to form a rectangle or square for easier stacking and/or easier imaging.
The prototype capillary integrated filter was tested with 10-30 μm glass beads available from Polysciences, Inc., Warrington, Pa., as part Catalogue #07668 as the particles. The result indicated that it is feasible to perform numerous wash cycles and incubations with minimal loss of the glass beads. Also, by injecting a solution on the opposite end, the filtered end, of the capillary filter tube, it is possible to recover the glass beads with minimal loss. This is important when one performs a multiplex assay where different beads have to be treated separately first and then they are recovered and combined into a single tube for further incubations and washes, as seen in
Referring to
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Using more than one integrated capillary filtered tube can provide a high throughput particle-based assay device, according to the teachings of the present invention. Preferably, the inner height 40 of the square or rectangular capillary filter tubes should be less than twice the height of the particles such that only a monolayer of particles can be formed inside the capillary tubes when the tubes are bundled together. In this case, an inlet interface shaped as a funnel can be used to inject the particles into the tube, as seen in
Referring to
As in
The interface 700 can be made of a glass, polymer or metal. Preferably, the wider mouth of the funnel-shaped interface 700 widens from, for example, about 0.05 mm to about 5 mm to form a funnel shaped inlet. The interface 700 also includes a sleeve 710 made of polymer, metal, or any other suitable support. The sleeve 710 has a polymer inside a coating or other similar material such that a water tight seal is formed between the interface 700 and the filtered capillary 10 when the filtered capillary 10 is plugged into the interface 700. Automated fluid dispensing system, such as the system seen in
Referring to
Without any complicated fluidic manipulation systems, the present invention can be adapted to the current microplate format. Rectangular capillary filter tubes are held in a reusable holder 502, which has the same footprint as standard microplates 504, for performing the assay. A conventional robotic fluidic handling system 506, having robotic arms for moving in the X, Y and Z directions can be used to carry out the multiple wash cycles 509 and incubations. The reusable holder 502 having the same footprint as standard microplates 504, e.g., 96, 384 and 1536 well plate format, holds the plurality of capillary filter tubes 10 together such that the existing robotic fluidic handling system 506 injects reagent 508 and sample from the well 504 into the flow inlet of individual capillary filter tubes 10. The holder 502 will allow an easy and convenient exchange or replacement of individual capillary filter tubes, if one is broken or needs to be modified for another surface chemistry.
Each of the filtered capillary tubes 10 is filled with one carrier support bead 200 as the particle that preferably is encoded with at least one rare-earth florescent dopant in a glass host. Numerous wash cycles 509 and incubations with minimal loss of the glass beads can next be performed. A sample is formed by disposing different types of probes contained in the well with a reagent 508. The sample containing the different types of probes for attaching to the bead are poured in each tube to form a particle mixture. Any unattached probes in a solution in each tube are filtered-out into a waste reservoir 510. Different labeled targets for binding with the attached probe in each tube are poured into each tube. All unbinded labeled targets in each tube are filtered-out. As seen in
Instead of arraying the filtered capillary tubes in a vertical (Y) position for detection, a monolayer of the filtered capillary tubes can be laid horizontally to also fit the image optical head of the detector pointing either on the top or bottom of the horizontal monolayer of filtered capillary tubes.
Referring to
Optionally, reagents can be injected into the capillary filter tubes from a horizontal position while the capillary filters are on the conveyor belt, if the reagents would not flow backwards. Otherwise, back pressure was applied, or the capillary filtered tubes were slanted slightly downward. Hence, an interface for each capillary filter tube can be adapted for easy and convenient loading or unloading of reagents and samples.
In an alternate configuration of the automated high throughput particle-based assay system, the whole system would be rotated 900 (i.e.,
In summary, the present invention is a high throughput biological particle-based assay device for allowing particle-based assays to be performed with minimal sample, minimal particle loss or human handling and enables the particles to be imaged or scanned at the completion of the assay without any additional fluid handling or transferring. Also, data analysis can be performed within the device without additional fluid handling and transferring. Unlike current technologies that require complicated fluidic handling system to manipulate the particles, the present invention isolates the particles within the same device to form a monolayer for easy scanning and/or imaging, and can be adapted to a high throughput format.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.