Classifications

• • G01N15/1433—
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
  • G01N33/54366—Apparatus specially adapted for solid-phase testing
  • G01N33/54373—Apparatus specially adapted for solid-phase testing involving physiochemical end-point determination, e.g. wave-guides, FETS, gratings
  • G01N33/5438—Electrodes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
  • G01N15/10—Investigating individual particles
  • G01N15/14—Electro-optical investigation, e.g. flow cytometers
  • G01N15/1484—Electro-optical investigation, e.g. flow cytometers microstructural devices

Definitions

• This invention relates to -devices and methods for performing active, multi-step sample preparation and molecular diagnostic analysis of biological materials. More particularly, it relates to integrated, compact, portable devices for self-contained sample to answer systems. Specifically, this invention relates to a device and method for performing multi-step sample preparation -and assay on either two or even a single microchip.
• Examples of applications for > ⁇ this integrated system include food and/or quality monitoring, diagnosis of infectious ⁇ diseases and cancers, bone marrow plastesis (e.g., stem cell separation and analysis), identification of individuals for forensic purposes.
• charged and uncharged microparticles in solution may be separated by dielectrophoresis.
• dielectrophoresis can be performed using a glass slide- based device having exposed, i.e., naked, interdigitated electrodes plated on the surface of the slide and having a flow chamber with a volume of several hundred microliters.
• cells, proteins, and nucleic acids can be separated based on their respective dielectric properties by using separation buffers having appropriate conductivity and an AC signal with a suitable amplitude and frequency.
• separation buffers having appropriate conductivity and an AC signal with a suitable amplitude and frequency.
• Such devices are also problematic in that the flow chamber volume (several hundred microliters) is so large that thermal convection can disturb and push materials such as cells and large molecules initially attracted to and retained by the electrodes off of the electrodes. Additionally, undesired cells and molecules are not easily washed off the surface without disturbing and loosing the desired cells as such cells and molecules can interfere with fluidic flow and, hence, block the flow during wash steps.
• Processing of the crude lysate often requires chemical reactions to remove undesired cellular components from the specifically desired ones. These reactions typically include subjecting the lysate to enzymatic reactions such as proteinase K and restriction enzymes or nucleases. Processing can also include enhancing the presence of desired molecules, particularly nucleic acids, by performing amplification reactions such as by strand displacement amplification (SDA) or polymerase chain reaction (PCR) methodologies. These reactions are also carried out in stand-alone processes. Only after these sample preparation and processing steps can assaying for data retrieval begin. Because of the numerous steps between sample collection and assay, many a technique is limited in its application by a lack of sensitivity, specificity, or reproducibility .
• SDA strand displacement amplification
• PCR polymerase chain reaction
• U.S. Patent No. 4,326,934 to Pohl discloses a method and apparatus for cell classification by continuous dielectrophoresis. With such method cells are separated by making use of both the positive and negative dielectrophoretic movement of cell particles. Separated cells are allowed to be characterized and/or classified by viewing the characteristic deflection distance of cells moving through the positive and negative electrodes.
• U.S. Patent No. 5,344,535 to Belts et al. discloses a method and apparatus for the characterization of micro-organisms and other particles by dielectrophoresis.
• U.S. Patent No. 5,569,367 to Belts et al. discloses a method and apparatus for separating a mixture of cells using a pair of energized interdigitated electrodes comprised of interweaved grid-like structures arranged to obstruct flow of cells through the appratus and cause differentiation of cell types into fractions by applying a non- uniform alternating field.
• other attempts have been made to combine certain processing steps or substeps together.
• various microrobotic systems have been proposed for preparing arrays of DNA probes on a support material. Beattie et al., disclose in "The 1992 San Diego Conference: Genetic Recognition", November, 1992, use of a microrobotic system to deposit micro-droplets containing specific DNA sequences into individual microfabricated sample wells on a glass substrate.
• Patent 5,126,022 entitled “Method and Device for Moving Molecules by the Application of a Plurality of Electrical Fields" describes a system by which materials are moved through trenches by application of electric potentials to electrodes in which selected components may be guided to various trenches filled with antigen-antibodies reactive with given charged particles being moved in the medium or moved into contact with complementary components, dyes, fluorescent tags, radiolabels, enzyme-specific tags or other types of chemicals for any number of purposes such as various transformations which are either physical or chemical in nature. Further, Clark, et al. in U.S.
• Patent 5,194,133 entitled “Sensor Devices” discloses a sensor device for the analysis of a sample fluid which includes a substrate having a surface in which is formed an elongate micro-machined channel containing a material, such as starch, agarose, alginate, carrageenan or polyacrylamide polymer gel, for causing separation of the sample fluid as the fluid passes along the channel.
• the biological material may comprise, for example, a binding protein, an antibody, a lectin, an enzyme, a sequence of enzymes, or a lipid.
• Various devices for eluting DNA from various surfaces are known. For example,
• Patent 5,434,049 entitled “Separation of Polynucleotides Using Supports Having a Plurality of Electrode-Containing Cells” discloses a method for detecting a plurality of target polynucleotides in a sample, the method including the step of applying a potential to individual chambers so as to serve as electrodes to elute captured target polynucleotides, the eluted material is then available for collection.
• an integrated, portable system and device for performing active, integrated multi-step sample preparation and molecular diagnostic analysis of biological samples using a minimal number of electronically addressable microchips.
• the system and device has a single flow cell element for carrying out the separation, preparation, and analysis of preselected eukaryotic and/or prokaryotic cells from a mixed population of cells.
• This single flow cell element includes therein an electronically addressable microchip having a grid of individual electrodes.
• the grid can contain any number of individual electrodes and be fabricated on a silicon wafer as is well understood in the electronic arts. Generally, such a grid can comprise anywhere from 4 to 25 to 100 or even 10,000 or more individual electrodes.
• This single flow cell embodiment contemplates that the flow cell encompassing the electronic grid is able to achieve simple fluidic manipulation of the cells for their respective separation, lysis, clean-up of cell-derived materials of interest, and analysis of .such materials.
• Preselected eukaryotic and prokaryotic cells may be any type (e.g., blood cells, cancer cells, stem cells, bacteria, etc.) and obtained from any source (e.g., animal, biopsy, blood, organs, forensic samples, stool, water, etc.).
• Specific examples of cells that can be separated from, for example, whole blood include Escherichia coli, Salmonella iyphimurium, Staphylococuus epidermus, Micrococcus lysodeikticus, and cultured cervical carcinoma cells.
• the device of the invention may include at least one additional flow chamber for carrying out either a variety of sample preparation steps or for analysis of prepared sample.
• the system comprises a first and second flow cell chambers each having an electronically addressable microchip.
• the first chamber may be used to separate and lyse cells as well as perform sample preparation steps, while the second chamber is used to analyze the sample materials directly on the second flow cell microchip.
• the first flow cell has no electronically addressable grid but does have .at least a heating element attached thereto that can be used to adjust the temperature of materials within said cell.
• the second flow cell is contemplated to have an electronically addressable microarray for use in performing analysis of the sample materials.
• the system of the invention provides the ability to (1) separate eukaryotic cell types from one another as well as eukaryotic cell types from prokarotic cell types, (2) directly process the sample materials from a crude state to a more refined state, and (3) directly analyze the sample materials on the microchip grid.
• the system contemplates the ability to directly lyse the cells in the sample and analyze materials of interest without a need for separating the cell types.
• the flow cell has a heating element that can be used to raise the temperature for direct lysis of the cells in the sample.
• sample preparation steps such as protease treatment or nucleic acid amplification may be performed followed by transporting the amplified species to the second flow cell containing the electronically addressable microchip.
• the integrated system contemplates the direct processing of cells selectively separated or lysed in the first chamber to obtain any materials of interest from such cells.
• processing is generally directed to the isolation and purification of proteins and nucleic acids from cellular contaminants.
• Numerous techniques can be performed in the preparation of molecules of interest including, but not limited to, enzymatic treatment using protease K to remove proteinaceous materials from nucleic acids of interest, enzymatic treatment using nucleases to remove nucleic acids from proteins, digestive residue adsorption, nucleic acid amplification (e.g., by PCR and SDA), in situ buffer exchange and binding of antibodies or other protein-protein binding reactions such as receptor-ligand or enzyme-substrate for binding to proteins of interest.
• analysis of prepared sample materials can comprise any number of preselected hybridization formats.
• nucleic acids of interest are hybridized selectively through an electronically directed process as is known to those skilled in the art of electronically addressable microchips.
• Such hybridization formats comprise binding of nucleic acids (RNA, DNA, pNA) to probes anchored to the microarray.
• Other formats contemplated for use with the system include selective capture of proteins of interest such as by antibody or other protein binding probes attached to the electronic grid. These can include other protein-protein interactions such as receptor- ligand and enzyme-substrate binding.
• the device contemplates elements (e.g. buffer vials, tubing, miniature solenoid valves, and at least one pump) for carrying and transporting samples, buffers, enzymes and reagents to and from said flow cell(s).
• elements e.g. buffer vials, tubing, miniature solenoid valves, and at least one pump
• detecting the analytes and molecules of interest being assayed include a battery operated diode laser (preferably having a wavelength of 635 nm), and a CCD camera coupled with filters and zoom lens for astronomy of the individual electrodes of the microchip grid(s) of the first and/or second flow cell chamber(s).
• Still other methods of detection are also contemplated not requiring illumination with a light emitting device such as direct electrochemical detection as is well known by those in the art of such detection as described in P. Ropp and H.Holden Thorp, Chemistry & Biology, 1999, Vol. 6, No.9, pp. 599-605.
• a light emitting device such as direct electrochemical detection as is well known by those in the art of such detection as described in P. Ropp and H.Holden Thorp, Chemistry & Biology, 1999, Vol. 6, No.9, pp. 599-605.
• Each of these electronic components are further contemplated to be coordinated through a computer and appropriate programming software as is well understood by those skilled in the electronic arts.
• Figure 1 is a simplified flow chart of the system showing three basic stages of the system including sample preparation, chemical reaction and analyte detection.
• FIG. 2 is a schematic showing the simple overall hardware design of the system wherein there is included a flow chamber 11 with heating element 12, a miniature desalting column 13, a laser 14 with optical path 15, and a detector such as a CCD camera 17.
• FIG. 3 is a perspective view showing one example of an external design for the portable system of this invention.
• the portable system comprises a housing 18 integrated with a computer and monitor 20 via a cable 19.
• Figure 4 is a an internal view of the integrated system showing various components thereof such as sample and reagent vials 21a-e, heating elements 12, CCD camera 17, laser 14, a series of pumps 46 for each reagent vial, and other features such as a focus adjustment knob 4 and area for electronic components 5.
• Figure 5 is a cross-section diagram for a flow cell having a microchip grid. The flow cell in total comprises a microchip grid 23 on the inner bottom surface of the flow cell chamber 29. The flow cell is covered by a quartz window 28. The underside of the microchip substrate has attached thereto a heating element 12. The flow cell has at least two inlet ports 30.
• Figure 6 is a schematic showing an alternative embodiment having two flow cells.
• a first flow cell can comprise either a cell having an electronically addressable microchip 31a, or not having such a microchip 31b. In either case, flow cell 31a,b has attached thereto a heating element 12.
• the second flow cell 32 has an electronically addressable microchip attached to a heating element 12.
• the integrated system further includes a desalting column 13, laser 14 with light path 15, and a detector 17 positioned on a movable track 33 for positioning the detector for astronomy of either flow cell.
• Figure 7 is a schematic showing a two flow chamber embodiment wherein first 31a and second 32 flow cells are arranged adjacent to one another. Also depicted are flow systems for channeling buffers, reagents, and analytes through the flow cells and desalting column of the system.
• Figure 8 shows bias pattern formats that can be used to create a pattern of dielectric force for separation of eukaryotic or prokaryotic cells.
• (A) is depicted a square-wall dielectric force pattern.
• (B) is depicted a checkerboard force pattern.
• Figures 9 and 10 show two computer representations of dielectric field distributions corresponding to either a square-wall or a checkerboard force pattern respectively.
• Figure 11 shows a photograph of an electronically addressable microarray in a flow cell during cell separation. The photo specifically depicts a bacterial species being separated from whole blood using a checkerboard dielectric force pattern applied to the electrode of the flow chamber. The bacteria are the light colored concentrations at the field charge maximums directly above the electrodes of the array while the blood cells are in between the electrodes at the field charge minimum areas.
• Figures 12, 13A and 13B show a eukaryotic cells (cultured HeLa cells) being separated from blood cells (Fig. 12) and after washing (Fig. 13A) and staining with propidium iodide (Fig. 13B).
• the mixture of the normal human white and red blood cells was pushed to the space between the electrodes where the field was minimum as reflected by the pinkish diamond-shaped spot (Fig. 12).
• Figures 14-17 show a series of photographs where bacteria cells are separated from blood cells using either a square-wall or checkerboard dielectric field pattern. Figs. 14 and 15 show such separation for square-wall and checkerboard patterns respectively. Figs. 16 and 17 show separated bacteria after washing square-wall and checkerboard patterns respectively.
• Figure 18 is a photo of a PAGE showing analysis of nucleic acids released from bacteria by electronic lysis.
• Lanes 1 and 6 are markers
• lanes 4 and 5 are whole bacteria DNA with and without Rnase treatment respectively
• lanes 2 and 3 are supercoiled and linear plasmid pCR2J DNA released from the bacteria.
• Figures 19 and 20 are PAGE photos showing amplification of two S. ent erica genes spa Q and inv A, by SDA in the flow cell of the invention.
• lanes 1 and 6 are size markers
• lanes 2 and 3 are negative and positive controls respectively
• lane 5 is the result of an amplification of inv A gene specific DNA sequence amplified using the device of the invention.
• lane 2 is a marker
• lanes 1 and 4 are positive and negative controls respectively
• lane 3 is the amplification result for the spa Q gene.
• Figure 21 is a photo showing hybridization results for spa Q gene wherein two electrode pads equipped with specific probe for spa Q gene were tested for hybridization in duplicate, a third pad specific for the gene was hybridized with amplified material from a positive tube reaction, and a fourth pad which was equipped with a nonspecific probe was tested for hybridization to amplification product produced in the flow cell.
• Figure 22 is a photo showing amplified spa Q gene products addressed to capture sites of electrodes of the microarray using two different biasing conditions. In the top row is duplicate addressing to pads having capture probes specific for spa Q sequence (lanes 3 and 4) while lanes 1 and 5 have nonspecific probes. In the top row, a sinusoidal wave AC format was used while in the bottom row a direct current (DC) format was used. The results indicate that using a DC format is slightly superior to an AC format in transporting nucleic acids to the electrodes as the DC protocol bound a higher degree of amplicon.
• a portable lab-on-a-chip system wherein a sample may be processed and analyzed in at least a single flow cell comprising an electronically addressable microchip.
• the elements of the device are housed in a portable casing or housing which contains the sample preparation and analysis flow chamber, fluid handling systems, and illumination source (such as a battery operated 635 nm diode laser) and detection electronics (such as a CCD camera coupled with a set of filters and a zoom lens for astronomy of the microchip).
• illumination source such as a battery operated 635 nm diode laser
• detection electronics such as a CCD camera coupled with a set of filters and a zoom lens for astronomy of the microchip.
• a computer such as a personal computer connected to the portable housing by a cable.
• a flow chart is shown depicting three distinct sample handling stages for carrying out bioassays as contemplated using the lab-on-a-chip system of the invention. These are: (1) sample processing, (2) chemical reaction, and (3) analyte detection.
• Sample handling in stage (1) processing generally comprises processing of crude biological samples (e.g., cells from blood, urine, stool, mixed cell populations, etc.) for the purpose of isolating molecules of interest such as nucleic acids and proteins.
• Sample handling at the chemical reaction stage (2) involves potentially many types of molecular biological reactions for clean-up and further isolation, purification, or amplification of molecules of interest including, but not limited to, enzymatic-based reactions such a treatment with proteases, nucleases and restriction enzyme digestion, PCR and SDA-based nucleic acid amplification, in situ buffer exchanges, chemical labeling such as by radioisotope and fluorescence markers, and immuno-based and protein-protein reactions such as antibody-antigen, ligand-receptor, and enzyme-substrate reactions.
• Sample handling at the analyte detection stage (3) may be accomplished through numerous formats including optical detection of fluorescent emissions, electrochemical detection, and radioisotope detection.
• this detection comprises hybridization of nucleic acids or captured proteins to the electronic grid and detection using fluorescent imaging.
• FIG 2 the system is depicted in schematic form showing a top-down or edgewise view of the basic components.
• a support 10 is used to mount the flow cell 11.
• a heating element 12 On the backside of the flow cell 11 mounted to the support is a heating element 12.
• the flow cell may be connected via a hollow fiber to ports and to a desalting column 13 in order to purify, desalt and introduce different buffers into the flow stream.
• the heating element may be used to heat the flow cell for either direct heat- induced lysis of cells in the chamber or for use in stage 2 process reactions such as inhibiting enzymes and temperature cycling for nucleic acid amplification.
• the flow cell as well as the other electrically operated components, such as solenoid operated valves and pumps, laser and detection camera, are interconnected electronically with the computer 20 by cabling 19 to the housing 18 for all programming and control purposes.
• the power source and computer are connected to the electrodes of the flow cell 11 for programming and manipulation.
• the electronic signals that may be generated by the computer software used with the system include an AC component, such as where the AC component is sinusoidal and used in dielectrophoresis, and such as where a DC component is square and used in hybridization.
• a time varying electronic signal also used in the system includes an offset signal, such as where the offset signal is a DC signal.
• Figure 2 further shows illumination source 14 that emits a laser beam 15.
• the illumination source 14 is a diode laser.
• the beam 15 is preferably incident on a beam splitter 16 that directs at least a portion of the beam 15 towards the flow cell 11 microchip for sample analysis. Radiation emitted from the microchip grid electrodes retraces the incident path, and at least a portion of that radiation is passed through the beam splitter 16 to detector 17.
• the detector 17 comprises a charged coupled device (CCD) detector. Alternatively, other detectors may be utilized. However, for compactness, it is preferred to have a detector hich generally has relatively larger area coverage compared to its depth (in the direction of the emitted radiation).
• Figure 3 shows a perspective view of one design or style for the overall portable, integrated lab-on-a-chip system.
• a computer 20, preferably a portable notebook personal computer includes conventional elements such as a keyboard, function keys, a monitor, and input devices, e.g., trackball, and mouse.
• Housing 18 serves to contain not only the preparation, reaction, and analysis platforms comprising the flow cell, but also additional equipment utilized in conjunction with computer 20 for operation of the system.
• housing 18 may contain (Fig. 4) a power supply, waveform generator, laser, flow cell(s), CCD camera, and other electronics, fluidic systems, and reagents required for operation and control of the system.
• FIG. 5 shows a cross-section of such a cell.
• An electronically addressable microarray 23 is mounted onto substrate 10 containing a 1.0 inch square pin grid array (PGA) (068 PPGA, 400 Square Cavity, Spectrum Semiconductor Materials, San Jose, CA).
• PGA 1.0 inch square pin grid array
• Attached to the back side of the substrate 10 is a ceramic chip heater element 12 (Dawn 505, Dawn Electronics, Carson City, Nevada).
• the heating element 12 may be attached by any number of methods.
• the attachment may be achieved by placing a thermally conductive flexible adhesive 22 between the backside of the electronic microchip and the ceramic heater and then incubating at an appropriate temperature and time to fix the adhesive.
• these microchips are coated with a thin permeation layer 25 such as a hydrogel, agarose, a polymer of acrylamide, or a sol-gel matrix or the like.
• This permeation layer 25 protects the cells and molecules of interest (i.e., biomaterials) from the electrochemistry occurring at the electrode surface that would otherwise damage the biomaterials (or the ability to assay them) if they were exposed directly to the electrodes.
• the microchip can be then attached to a molded or machined medical grade plastic flow cell 27 so that the electronic microarray 23 makes up the inner bottom surface of a well within the flow chamber.
• the flow cell 27 provides a compartment 29 for containing biological sample materials and buffers to be layered on top of the microchip.
• the flow cell may be further designed to have at least 2 to 4 ports 30 for sample delivery and extraction.
• the flow cell 27 may further be constructed so as to accept tubing for interfacing with exterior fluidic delivery and removal systems as well as desalting.
• the flow cell compartment is covered and sealed by a fused quartz window or lid 28 for visual access to the microarray analysis sites or capture pads. This window 28 can comprise any thickness of quartz but generally is about 0.015 inches thick.
• the window 28 may be attached to the flow cell and the flow cell to the chip by any number of methods of which a preferred method uses.
• an ultraviolet (UV) curing adhesive 26 developed for optics assembly. Attachment of the flow cell to the chip may be either directly to a bare surface of the chip or to the permeation layer overlaying the microarray also using adhesive 26.
• Tubing is attached to the inlet and outlet ports using a variety of methods depending on the tubing size, fittings, and the tubing base material.
• the integrated system may use two flow cells, one for sample preparation and the second for analysis.
• Figure 6 shows in schematic form such an embodiment.
• the first flow chamber 31 is attached to a heating element 12 and may optionally have an electronically addressable microchip 31a or no such microchip 31b.
• the flow cell 31 is used to perform in a stepwise fashion cell separation and/or cell lysis, and clean-up and further preparation of molecules of interest recovered from the lysed cells.
• molecules of interest is contemplated to include any number of chemical reactions and steps as stated above such as isolating specific proteins of interest, isolating nucleic acids of interest such as by treatment with proteases to remove proteinaceous material from the nucleic acids, and amplification of nucleic acids of interest su ⁇ h as by PCR and SDA.
• the second flow cell 32 is used for sample analysis.
• both flow cells 31 and 32 are disposed on the same side of the support 10.
• these flow cells may be disposed in alternative arrangements, including a back-to-back or a stacked configuration.
• these two flow cells may be connected via a hollow fiber in order to purify, desalt and introduce different buffers into the flow stream.
• each flow cell may be designed to have independent temperature control elements as desired.
• each of the electronically addressable microchips within the flow cells, as well as the other electrically operated components, such as solenoid operated valves and pumps, are interconnected electronically with the computer 20 by cabling for all programming and control purposes as in the single flow cell arrangement.
• Figure 6 further shows illumination source 14 that emits a laser beam 15 and operates in the same fashion as described above.
• a camera with zoom lens 17 for astronomy of the electronic grids of the flow cells is also incorporated on a movable track 33 so that both the first and second flow cell electronic microarray grids can be viewed.
• Figure 7 is a schematic of the alternate system showing support 10 including the flow cells for sample preparation 31a (shown as an electrode comprising flow cell) and analysis 32 (shown as a 25 electrode grid).
• Each of the flow cells preferably include a plurality of ports 42 connected to tubing or hollow fiber 44 leading to electrically operated 3-way valves 45.
• the cell is contemplated to possess at least two ports 42, optionally at least three ports, and in the preferred embodiment four ports.
• this cell preferably has two ports.
• These ports 42 and their respective tubing 44 may be utilized for various functions at different times.
• a port may be considered an input port, whereas at another time, it may comprise an output port, based on the directionality of the flow into or out of the flow cells 31 and 32 as directed by the setting of the 3-way valves 45 and directionality of pump 46.
• Fluids in the chambers may be mixed by "pushing" and “pulling" of the liquids in various sequences through the ports. Such mixing may be advantageous, for example, during an amplification procedure.
• Figure 7 further depicts other components of the self-contained system.
• receptacles 21a-e provide for carrying samples and reagents such as for washing, amplification, hybridization, and waste.
• the support 10 has attached thereto a miniature desalting column or a hollow fiber ion-exchange unit 13 for desalting small sample volumes.
• a desalting step to lower the ionic strength of the sample prior to attempting to electronically address amplified nucleic acids to specific capture pads of the microarray. This is because reagents used in amplification steps have an ionic strength that interferes with the migration of molecules of interest under the electronic addressing protocols.
• cell separation is achieved by a dielectrophoresis technique.
• polarizeable particles e.g., eukaryotic and prokaryotic cells
• polarizeable particles including those with no net charge are subject to a "dielectrophoretic" force of a non-uniform electrical field.
• the direction of migration of different cell types is determined by: (1) surface charges of the cell walls or membranes of the cell bilipid membranes, (2) the conductivity and permitivity of such cell membranes and walls, and (3) the morphologies and structural architectures of the cells.
• Dielectrophoresis as practiced in the current invention has been used to selectively separate from mixed cell populations (e.g., blood cells) several types of bacteria including Escherichia coli, Salmonella typhimurium, Micrococcus lysodeikticus and Staphylococcus epidermidis as well as cancer cells such as cultured cervical carcinoma cells.
• mixed cell populations e.g., blood cells
• bacteria including Escherichia coli, Salmonella typhimurium, Micrococcus lysodeikticus and Staphylococcus epidermidis
• cancer cells such as cultured cervical carcinoma cells.
• a flow cell useful for separating cells as practiced in this invention may be designed to include an electronically addressable microchip having at least 100 individually addressable microelectrodes capable of being biased individually so that a dielectric force pattern may be generated across the microchip electronic grid.
• Fig. 8 shows two such force patterns. In Fig. 8A is a square-wall pattern while 8B shows a checkerboard pattern. Each of these patterns provide a unique strong and weak ionic field strength pattern that provides dielectric force sufficient to separate different cell types.
• the force pattern is further depicted in computer generated field patterns shown in Figs. 9 and 10 for square-wall and checkerboard respectively.
• the electrodes of the microarray in the flow cell(s) may be biased either all together as a single array for carrying out cell separation, lysis, and analysis, or may be programmed to form subarrays in any number of patterns for carrying out the separation, lysis, and analysis steps.
• one subset may be biased to separate cells, another set may be biased to cause cell lysis, and yet another set may be used for analysis.
• Figure 11 shows the separation of Micrococcus lysodeikticus from whole blood.
• the bacteria are concentrated above the electrodes while the undesired blood cells, both red and white cells, are dark areas in between the electrodes.
• the cells were made to separate using a protocol of biasing comprising a sinusoidal signal of 10 V peak-to-peak at 10 kHz. Although this signal value was used in this instance, generally cell separation can be carried out using sinusoidal signals wherein the Volts are between 2 and 20 peak-to-peak while frequencies are between 5 and 50 kHz.
• Undesired cells are washed from the flow chamber while retaining the cells of interest. This is accomplished by maintaining an attractive bias for the cells of interest and creating a flow of wash buffer through the flow chamber.
• the cells of interest are isolated in the flow chamber they may be treated in any number of ways for further processing.
• the cells are lysed by applying high voltage pulses of up to 450 volts with a pulse width between 10 ⁇ s and 50 ⁇ s as described in J. Cheng, et al., "Preparation and hybridization analysis of DNA/RNA from E coli on microfabricated bioelectronic chips," Nature Biotechnol, 16, pp. 541-546, 19,98.
• E. coli cells were separated from blood cells as shown in Figures 14-17. In Figure 14 a square-wall dielectric force pattern was used while in Fig. 15, a checkerboard pattern was used.
• the separation for the checkerboard pattern used a bias format of a sinusoidal signal of 10 V peak-to-peak at 10 kHz.
• Figures 16 and 17 show how cleanly the bacterial cells were isolated following washing of the square-wall and checkerboard patterned separation.
• mammalian cells are separated on the electronic grid of the flow chamber.
• Figures 12, 13A and 13B show separation of cervical carcinoma cells.
• Fig. 12 shows initial separation wherein the cells move onto the electrodes of the grid where the field is at a maximum by subjecting the cells to a positive dielectrophoretic force.
• the mixture of the normal human white and red blood cells mixed with the carcinoma cells are pushed to the space between the electrodes where the field was minimum as reflected by the pinkish diamond-shaped spots.
• the carcinoma cells were retained by the electrodes (Fig. 13A) whereas all of the normal blood cells were washed out.
• Figure 13B shows the cells after staining with propidium iodide.
• the mammalian cells could be separated using the checkerboard format and applying a sinusoidal signal of 6 V peak-to-peak at 30 kHz for 3 minutes.
• J. Cheng, et al "Isolation of Cultured Cervical Carcinoma Cells Mixed With Peripheral Blood Cells on a Bioelectronic Chip," Anal. Chem. v.70, pp2321 -26, 1998.
• both cellular proteins and nucleic acids may be retained for analysis.
• An example showing that nucleic acid may be retained from lysed cells is provided in Figure 18.
• E. coli DNA is run on a PAGE gel showing both chromosomal and plasmid DNA is retained.
• further clean-up and purification may include treatment with proteases such as with Proteinase K.
• proteases such as with Proteinase K.
• the lysate may either be analysed immediately, or amplified then analysed.
• the sample may be further treated in the flow chamber or may be exported to the second chamber for such protease treatment, amplification and analysis.
• a protease treatment may be carried out in an appropriate buffer at 60°C for 15 min. Temperature control may be achieved by use of the ceramic heater element attached to the back of the microchip.
• Inactivation of proteinase K may be achieved by heating the sample at 95°C for 2 min. Overall, the cell separation, lysis, and protease treatment process can take between 15-25 minutes.
• nucleic acids may be removed by treating the sample with restriction enzymes and nucleases.
• the proteins may further be treated with various enzymes and partial protease treatments to release specific proteins of interest from cell membranes and other cellular components.
• additional processing may be carried out including amplification (e.g., by PCR and SDA) and labeling with radioisotopic or fluorescent markers.
• nucleic acid sequences i.e., the invA and spa Q genes of Salmonella enterica
• SDA is preferred in this portable system as the amplification may be performed under isothermal conditions at between 50°C and 60°C thereby eliminating high temperature denaturation cycles associated with PCR.
• the portable system is capable of performing PCR amplification as the flow chamber is equipped with the aforementioned heating element that has the capability of achieving repetitive high temperature cycling.
• SDA can be effectively performed in the device with a product yield comparable to the positive control performed in a conventional reaction tube.
• Salmonella enterica and blood cells were mixed and injected into the flow cell containing a 10,000 site electrode array.
• the bacterial cells were separated from the blood cells by dielectrophoresis using a biasing protocol of a 10V peak-to-peak signal having a sinusoidal wave form with frequency of between 10 and 15 kHz using the checkerboard pattern.
• the cell mixture was pumped into the flow cell at a rate of 31 ⁇ l per minute until the flow chamber was filled, then the flow rate was adjusted to 12.4 ⁇ l/min until the total 50 ⁇ l volume was passed through the chamber.
• the cells were retained above the electrodes by influence of the positive dielectrophoretic force established by the protocol.
• the flow cell was then washed with water to remove cells not retained by the positive bias by pumping buffer in a reverse direction at a rate of 1 14 ⁇ l/min for 10 minutes.
• the fluid content of the flow cell was then exchanged with a solution of SDA reagents for amplifying either the spa Q or inv A gene sequences.
• the total nucleic acid from the bacteria cells was isolated by first lysing the cells by energizing the electrodes with pulsed direct current at 200 V having a square wave form af 10 ms duration and a total of 40 separate pulses. (Alternatively, the cells can be lysed by heating the chamber to 95°C for five minutes).
• a concentrated SDA reagent and buffer stock mix was introduced into the flow cell and mixed with the denatured target nucleic acid to give the following final concentrations of SDA reaction components: 500 nM amplification primers, 50 nM 'bumper' primers, 9.5 mM magnesium acetate, 35 mM potassium phosphate buffer pH 7.6, 80 ⁇ g/ml bovine serum albumin, and 1 A mM each of dATP, dGTP, TTP, and alpha-thiolated dCTP.
• the amplification primers were designed to amplify 81 base pairs of the inv A or spa Q gene and comprised the following nucleic acid sequences: spa Q Seq. Id. No.
• Bumper primers comprised the following sequences: -- 7-3 Q Seq. Id. No. 5 5'-gcaacgattatcggc-3' spa Q Seq. Id. No. 6 5'-ccagacagtaaaac-3' inv A Seq. Id. No. 7 5'-ttgacagaatcctca-3' inv A Seq. Id. No. 8 5'-taagacggctggta-3' The released nucleic acid was then denatured by heating the chamber to 90°C for five minutes.
• the chamber was then brought to 60°C and 10 ⁇ l of SDA reagent buffer containing enzymes was introduced into the chamber to initiate amplification (i.e., 40 units of BsoBl restriction endonuclease and 16 units of exo'Bst DNA polymerase).
• amplification using SDA may be carried out for between 25 and 35 minutes.
• a 5 ⁇ l aliquot of the reaction volume was removed for PAGE analysis (Figs. 19 and 20).
• the third stage of sample handling comprising detection of the molecules of interest is preferably carried out for proteins and nucleic acids of interest.
• detection can use various forms of hybridization to probes previously ' attached to the microarray.
• nucleic acids e.g., RNA, DNA, and pNA
• sample- derived nucleic acid analyte e.g., amplified or unamplified target nucleic acids
• Proteins may also be made to bind to capture molecules (i.e., protien-ligand binding interactions) attached to the array.
• capture molecules may comprise proteins or other molecules and the binding interaction can comprise such interactions as antigen- antibody, enzyme-substrate, and receptor-ligand binding.
• target species are electronically addressed to specified capture pads of the microarray of either the single (or the secondary) flow chamber for capture by oligonucleotide probes that are anchored thereto.
• the electrode array of the flow cell i.e., flow cell 11, 31a or 32 depending upon the embodiment and protocol used
• the electrode array of the flow cell has at least 25 individually- addressable electrodes coated with a permeation layer (e.g. for example, an acrylamide- based hydro-gel).
• the target nucleic acid is biased using a positive sinusoidal signal generated using a function generator/arbitrary wave form generator (33120A, Hewlett Packard, Santa Clara, CA).
• the capture probe-target hybrids are then detected using fluorophore-labeled reporter probes and the CCD-based optical imaging system employed for the portable instrument shown in Figure 2. Detection with this arrangement takes approximately 5 min to accomplish.
• the amplification products of the spa Q and inv A genes were available for capture and analysis. Prior to capture, the SDA reaction solution and amplification products were passed through a desalting column in a volume of about 75 ul followed by exchanging the buffer with a 50 mM Histidine buffer. The amplification products were then addressed to specific pads of the electrodes which contained gene specific probes attached to the permeation layer overlaying the electrodes.
• Figure 21 shows results of binding of the spa Q gene amplification product to individual pads of the electrode in the flow chamber.
• the binding shows that the amplification product produced in the flow cell annealed to the capture pads (fraction 1 and 2) satisfactorily in comparison to annealing of amplification product produced as a control in a reaction tube and then introduced into the flow cell chamber after the fractions 1 and 2 had been addressed.
• the level of binding for the control amplified product is higher due to the higher level of amplification obtained in the control reaction.
• the amplified SDA products for the spa Q gene were also addressed to specific pads on the microarray using two alternate biasing formats.
• the amplicons were addressed using a sinusoidally based AC format of 3.5 V peak-to-peak at 1 kHz. This protocol also used a DC offset voltage of +2.3 V for 5 minutes. In the other protocol, a direct current (DC) format was used comprising +2.5 V for 2 minutes. As can be seen, the DC protocol is able to transport the molecules of interest to the capture sites with greater efficiency as the DC biased pads exhibit a greater binding signal. This result further shows the versatility of the system in that processing of sample materials (cells and molecules) may be manipulated in a wide range of adjustments that is possible using this electronic-based lab-on-a-chip system.
• DC direct current
• the use of an AC format though shown in the above example as providing less transport mobility to the specific sequence can be performed where the voltage range is between 2.0 and 5.0 peak-to-peak, the frequency range is between 1 and 10 kHz, and the DC offset is in a range of 1-5 volts).
• This versatility of ranges provides for transport, of molecules under variable buffer conditions.
• Visual detection of amplification reaction products by probe hybridization may be performed by directing a battery operated diode laser having at least the capability of generating approximately 2 m Watts of laser power with an emission wavelength of 635 nm.
• the laser is used to excite fluorescent dye-label reporter probe (such as BODIPY- 630).
• the wavelength of the emission filter is 670 nm.
• the dichromatic mirror has a wavelength cutoff at 645nm.
• a direct electrochemical voltammetric detection system may also be used instead of light based detection as is understood by those skilled in the art.

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