Clinical Chemistry
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Clinical Chemistry 44: 2008-2014, 1998;
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Web of Science (86)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kricka, L. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kricka, L. J.
Related Collections
Right arrow Oak Ridge Conference
Right arrow Proteomics and Protein Markers
Right arrow Drug Monitoring and Toxicology
Right arrow Endocrinology and Metabolism
Right arrow Automation and Analytical Techniques
(Clinical Chemistry. 1998;44:2008-2014.)
© 1998 American Association for Clinical Chemistry, Inc.

Oak Ridge Conference

Miniaturization of analytical systems

Larry J. Kricka

Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104. Fax 215-662-7529; e-mail larry_kricka{at}path1a.med.upenn.edu.


Abstract

Miniaturization has been a long-term trend in clinical diagnostics instrumentation. Now a range of new technologies, including micromachining and molecular self-assembly, are providing the means for further size reduction of analyzers to devices with micro- to nanometer dimensions and submicroliter volumes. Many analytical techniques (e.g., mass spectrometry and electrophoresis) have been successfully implemented on microchips made from silicon, glass, or plastic. The new impetus for miniaturization stems from the perceived benefits of faster, easier, less costly, and more convenient analyses and by the needs of the pharmaceutical industry for microscale, massively parallel drug discovery assays. Perfecting a user-friendly interface between a human and a microchip and determining the realistic lower limit for sample volume are key issues in the future implementation of these devices. Resolution of these issues will be important for the long-term success of microminiature analyzers; in the meantime, the scope, diversity, and rate of progress in the development of these devices promises products in the near future.

Miniaturization of analytical and bioanalytical processes has become an important area of research and development during the past 10 years (1)(2)(3) , as a continuation of the general trend in size reduction of clinical laboratory analyzers. The original type of floor-standing analyzer (e.g., AGA Autochemist, Technicon SMAC) (4)(5) has been successively reduced in size, first to bench top and then to portable and hand-held devices. Micrometer-sized microchip devices, and ultimately nanometer-sized nanochip devices, represent the endpoint of this progression. A number of benefits are identifiable with miniaturization, notably reduction in manufacturing costs, ease of transport and shipping, and minimal space requirements in a laboratory. In addition, a microminiature device is easier to hold and manipulate, reduces requirements for power and consumable reagents, and offers the possibility of high-density testing and integration of individual steps in a multistep analytical process.

Several factors are fueling current interests in miniaturization. These include point-of-care testing (6) , high throughput drug discovery (7) , detection of biological warfare agents (8) , and astrobiology ((9)). Analyzers for point-of-care testing need to be small, lightweight, and portable with low power requirements; all of these design goals can be achieved via miniaturization. In high throughput drug discovery, the sheer scale of testing (thousands of candidate drugs to be tested against thousands of biological targets) and the need to conserve the limited quantities of archival compounds or substances produced by combinatorial synthesis procedures (10) require high-density arrays of microvolume reaction vessels. The emerging demands to monitor and detect the release of biological warfare agents (e.g., Clostridium botulinum toxin and anthrax) by aggressors in a battlefield or by terrorists in a domestic situation may best be met by microminiature detection devices. Likewise, the limitations on space and weight for rocket payloads strongly supports miniaturization of analyzers designed for astrobiological tasks.

The new generation of microminiature analyzers and the proposed nano-sized devices will be built on a scale that would have been difficult to comprehend when the first automatic analyzers were introduced into the clinical laboratory >30 years ago (11) . Dimensions of the smallest structures in microchips are typically 10–100 µm (the diameter of a human red cell is 7 µm), and the proposed nanochips will be several orders of magnitude smaller.

In the current miniaturization trend, four main types of microminiature analytical devices are emerging: (a) high-density arrays of microreaction wells, (b) surface microarrays of reagents, (c) microchips, and (d) nanochips.


High-density Arrays of Microreaction Wells

The new emphasis on high throughput drug discovery methods in which vast numbers of candidate drugs are screened against equally large numbers of biological targets has generated new demands for microminiature analysis. Essential characteristics for an analytical drug discovery method include rapid, automated, and simultaneous testing of microvolumes of candidate drug compounds. Many of the compounds included in drug screening assays are archival and only available in a very limited quantity or are the products of combinatorial synthesis procedures and thus are only produced in microgram to milligram quantities. Conservation of valuable compounds is imperative, and miniaturization of assays is an immediate and viable route to this objective. The microplate has become the most popular format for drug discovery assays because it is readily integrated into an automated process and provides multiple simultaneous testing on a simple disposable device. The traditional 96-well format has proved inadequate and is being replaced by microplates with larger numbers of smaller wells (12)(13)(14)(15)(16)(17)(18) . These include plates with 192, 384, 864, 1536, 2025, 2288, 2304, 2400, 3456, 6144, 6500, 9600, and 20 000 wells with volumes that range from 125 µL to 50 nL. Microplates with 384 and 1536 wells (Fig. 1 ) are vying for acceptance as the new standard in high throughput screening; however, to date there has been no consensus on optimal well density or volume. These microminiaturized reaction devices have placed new demands on ancillary equipment. In response, a range of new micropipetting systems based on ink-jet principles (thermal-, solenoid-, or piezoelectric-actuated) have been developed for delivery of microliter to nanoliter volumes of sample or reagents (19)(20) . Injection molding is used for manufacture of most of the high-density microvolume microplate devices; however, other techniques such as polymer casting (16) and drilling (13) are also effective manufacturing techniques.



View larger version (93K):
[in this window]
[in a new window]
  		Figure 1. High-density microwell plates.

(A) 384-split well microplate (Robbins Scientific); (B) 384-well microplate (Nalge Nunc International Corp); (C) 1536-well microplate (Greiner Labortechnik).

A diverse range of analytical methods have been adapted to the new high-density, low-volume microwell format. Most are simple mix-and-measure type homogeneous assays, such as scintillation proximity assays, fluorescence polarization assays, time-resolved fluorescence assays, reporter genes, and enzyme assays. To date, there has been relatively less progress in formatting multistep separation assays, such as ELISA, to a high-density microwell format.


Surface Microarrays of Reagents

Fabrication of surface microarrays of nucleic acids (21)(22)(23)(24)(25)(26) and proteins ((27)(28)(29)(30)) at discrete locations on small chips is another important direction in miniaturization methods. Chips are typically in the size range of 1–2 cm2; the elements in the arrays vary from 1 to 200 µm but are usually 10–100 µm (diameter or length on side). Chips containing all 65 536 possible oligonucleotides in 8-nucleotide chains (8-mers) (22) and chips with 48 300 possible oligonucleotides in 20-nucleotide chains (20-mers) (25) are representative of the scale of array possible with this type of microminiature technology.

Microarrays of polynucleic acids or proteins are produced by a number of methods. In situ combinatorial synthesis uses photolithographic masks to define discrete array locations for photodeprotection-type synthetic reactions (22)(24)(25) . In this way, an oligonucleotide or a polypeptide molecule is synthesized one base or one residue at a time on the surface of a glass chip. Synthesizing an n-mer requires 4 x n steps; thus 32 steps are required to synthesize the 65 536 possible 8-mers and 80 steps to produce the ~1012 possible 20-mers. Alternatively, rubber spacers can be used to define orthogonal reaction channels on a glass surface (31) , or a 64-channel fluidic chemistry delivery system can be used to perform synthetic reactions at defined locations on a polypropylene chip (21) . Other options include direct attachment of preformed oligonucleotides to an activated chip surface (e.g., aminated polypropylene or polyacrylamide gel pads) (23) or attachment of pyrrole-substituted oligonucleotides to arrays of 50 µm x 50 µm polypyrrole-coated gold electrodes via electrosynthetic reactions (32) .

Direct arraying of the reagent onto the chip can be by a deposition process using a syringe microdispenser (33) , an array of ink-jet print nozzles (25) , micropins (e.g., 100 µm thick, 1-nL transfer volume) (23) , or open-capillary tips (34) that are simply dipped into the substances to be arrayed. Table 1 (35)(36)(37)(38)(39)(40)(41)(42)(43)(44) lists examples of the applications of the array devices in immunological and genetic testing assays. Most devices are oligonucleotide, cDNA, or polypeptide arrays; however, arrays of unnatural polymers based on aminocarbamate monomers linked via a carbamate backbone have also been prepared (45) .


View this table:
[in this window]
[in a new window]
  		Table 1. Applications of microarray devices.


Microchips

A typical microchip is 1.5 cm x 1.5 cm in size and a few millimeters thick. Materials for microchip fabrication include silicon, glass, quartz, and plastics such as Teflon, polymethylmethacrylate, and polycarbonate (1)(2)(3) . In the case of silicon microchips, a range of fabrication techniques have been adopted from the microelectronics industry, including wet etching using KOH and reactive ion etching processes (46) . Other techniques include laser ablation/drilling, electrodischarge, injection molding, polymer casting, printing, and Lithographie Galvanoformung Abformung (LIGA) (46)(47)(48) . Ablation or drilling with a Nd:YAG laser offers a simple one-step process for fabrication of features <30 µm on a variety of materials. It is particularly useful for cutting curved and irregular shapes that are more problematic for conventional etching methods (47) .

Hot embossing is emerging as a highly promising method of making plastic microchips; this is important because it would lead to high-volume low-cost continuous production methods that may be easier to implement than batch etching of silicon wafers for silicon-based microchips (Fig. 2 ). The range and scope of microchip assays and analyzers continue to grow; some recent examples of devices for different types of assays or analytical procedures are listed in Table 2 (49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74) .



View larger version (126K):
[in this window]
[in a new window]
  		Figure 2. Polymethylmethacrylate microstructure produced by hot embossing.

Channel width is 100 µm, depth is 25 µm. (JENOPTIK Mikrotechnik Gmbh).


View this table:
[in this window]
[in a new window]
  		Table 2. Microchip assays and analyzers.


Nanochips

One vision of the future direction of miniaturization is nanochip devices that are built at the nanometer scale from individual atoms and molecules (75)(76)(77) . The nanotechnologist's view is that the counterparts of machine components can be found among natural molecules and biological assemblies of molecules: for example, collagen is a cable, an antibody is a clamp, DNA is a memory device, and membrane proteins are pumps. Currently there are no examples of nanochips; however, progress in self-assembling molecular structures, e.g., 0.5-µm diameter, 30-µm long lipid tubules (78) , 0.7- to 0.8-nm diameter cyclic peptide nanotubes (79) , and the design and synthesis of molecules that mimic mechanical devices provide the grounds for some optimism for this avenue of development (e.g., recently, a metallocene molecular gear was successfully synthesized) (80) .


Scaling Issues for Microanalytical Devices

Implementation of microanalytical devices presents a series of issues related to the physical size of the device and the scale of the reaction volumes.

If a human interface is anticipated, then a microanalytical device must be mounted or packaged into some type of holder or cartridge that provides a convenient means of introducing a sample. This approach has been adopted for the Affymetrix microarray chips (22) , microParts microspectrometers (microParts), and the i-STAT chip (i-STAT Corp.) (81) .

Successive reduction in the volume of the sample analyzed in a microanalytical device may compromise analysis either because the measurement limit of the analytical method is exceeded or because the sample is no longer representative of the bulk specimen. For example, a 1-µL sample of a specimen containing an analyte at a concentration of 1 fmol/L contains 6020 molecules. Further reduction in sample size to 1 nL leads to a sample containing only 6 molecules of analyte, which may be substantially less than the detection limit of the analytical method formatted into the microchip.

Analysis of rare cells poses yet another challenge for microminiaturized analysis. Fetal nucleated red cells are present in very low abundance in the maternal circulation. For example, 18 mL of maternal blood may only contain 20 fetal cells among a total cell population of nearly 108 nucleated cells (82)(83) . Sampling a microliter volume is unlikely to provide a sample containing even a single fetal cell; thus, other strategies are required, such as on-chip flow-through capture/concentration techniques.

Another complication for microchip devices is evaporation of microvolumes of sample or reagent from the microchip, thus compromising the volumes metered into the device. This problem has been addressed by designing pipetting systems that automatically replace fluid lost by evaporation or by enclosing the chip in a controlled environment (84)(85) .


Integration

A key benefit of miniaturization is the prospect of integration of all of the steps in an analytical process into a single device. For bench-top analyzers, entire fluidic modules have been machined into transparent plastic blocks to provide both integration and some degree of miniaturization (e.g., UnifluidicsTM Technology, Bayer Corp.). For microchips, the range of components that have been miniaturized and that would be available as building blocks for fully-integrated analyzers is impressive and includes pumps, valves, lamps, filters, heaters, refrigeration, ion-selective electrodes, capillary electrophoresis, and electronic control circuitry (1)(86)(87) . Some of the analytical functions integrated into single-chip devices are listed in Table 3 (88)(89)(90)(91)(92)(93)(94)(95) . Most devices integrate the different analytical structures by interconnection on the surface of the chip. Three-dimensional integration can be achieved by stacking or by fabricating chips into interconnected layers (96)(97) . Integrating the sample preparation step required in an analytical procedure is an important goal, and white cell isolation from whole blood followed by PCR analysis has been successfully combined on a single 15 mm x 17 mm silicon-glass PCR filter chip (54) . Integration of an analytical procedure and detection is possible for a number of assays. For example, restriction fragment length polymorphism analysis can be performed on a glass microchip (~20 mm x 30 mm) that mixes a DNA sample with a restriction enzyme, incubates the mixture, and then delivers the 0.7-nL reaction mixture to an on-chip capillary electrophoresis system for analysis (74) .


View this table:
[in this window]
[in a new window]
  		Table 3. Combinations of components integrated into microanalytical systems.

Capillary electrophoresis in combination with laser-induced fluorescence is a popular on-chip detection option for integrated analysis because it is sensitive, versatile, and the sample volume required is low. It proved effective in the quantitation of bound and free fluorophore-labeled fractions in a competitive immunoassay for theophylline performed on a glass microchip. Steps involving mixing and incubating the sample and reagents and detecting the product (100-pL sample of reaction mixture) were performed on the chip. Quantitation of the bound and free fluorescein-labeled fractions took <1 min in a 58-µm wide, 7.5-cm-long, on-chip separation channel (88) .

Another integrated microchip device utilizes a series of electrodes coated with DNA capture probes. The 200-µm diameter electrodes facilitate electronic hybridization, washing, and dehybridization within the chip. Positively biased electrodes facilitate capture of negatively charged DNA, and by changing the bias to negative, captured target can be dehybridized and transported to a reaction site. This "complexity reduction" device has been used to capture DNA sequences from complex mixtures and to quantitate captured target by means of a charge coupled device and a fluorophore label (e.g., Bodipy Texas Red) (92)(93) .


Conclusions

Miniaturization continues to be an important consideration in the design and development of many assays and analyzers. The escalating interest in high-throughput screening for drug discovery and the large-scale analysis required for genetic studies will continue to be major factors influencing miniaturization. There are already numerous examples of assays and analytical processes that have been successfully adapted to a microchip format, and the goal of a "lab-on-a-chip" is realistic. The emergence of microchips fabricated from plastics (98) will help eliminate some of the materials issues encountered with silicon devices (69) . One of the next major challenges in miniaturization is the development of nanotechnology and fabrication of nanochips.


References

  1. Kricka LJ, Wilding P. Micromechanics and nanotechnology. Kost GJ eds. Handbook of clinical automation robotics and optimization 1996:45-77 John Wiley & Sons New York. .
  2. Kricka LJ, Nozaki O, Wilding P. Micro-mechanics and nanotechnology–implications and applications in the clinical laboratory. J Int Fed Clin Chem 1994;6:54-59.
  3. van den Berg A, Bergveld P, eds. Micro total analysis systems. Dordrecht: Kluwer Academic Publishers, 1995:311pp..
  4. Bokelund H. A review of the autochemist system in a hospital environment. Scand J Clin Lab Investig Suppl 1974;140:9-26. [Medline] [Order article via Infotrieve]
  5. Westgard JO, Carey RN, Feldbruegge DH, Jenkins LM. Performance studies on the Technicon "SMAC" analyzer: precision and comparison of values with methods in routine laboratory service. Clin Chem 1976;22:489-496. [Abstract/Free Full Text]
  6. Dirks JL. Diagnostic blood analysis using point-of-care technology. AACN Clin Issues 1996;7:249-259. [Medline] [Order article via Infotrieve]
  7. Devlin JP, ed. High throughput screening. New York: Marcel Dekker, 1997:673pp..
  8. Barnaby W. Biological weapons: an increasing threat. Med Confl Surviv 1997;13:301-313. [Medline] [Order article via Infotrieve]
  9. Smith JM, Szathmary E. On the likelihood of habitable worlds. Nature 1996;384:107.[Medline] [Order article via Infotrieve]
  10. Gallop MA, Barrett RW, Dower WJ, Fodor SPA, Gordon EM. Applications of combinatorial technologies to drug discovery. 1. Background and peptide combinatorial libraries. J Med Chem 1994;37:1233-1251. [Web of Science][Medline] [Order article via Infotrieve]
  11. Alpert NL. Automated instruments for clinical chemistry: review and preview. Clin Chem 1969;15:1198-1209. [Abstract]
  12. Sasaki N. Development of high-throughput polymerase chain reaction system and its performance. Hokkaido J Med Sci 1997;72:249-259.
  13. Sterrer S, Henco K. Fluorescence correlation spectroscopy (FCS)–as highly sensitive method to analyze drug/target interactions. J Receptors Signal Transduct Res 1997;17:511-520.
  14. Schullek JR, Butler JH, Ni ZJ, Chen D, Yuan Z. A high-density screening format for encoded combinatorial libraries: assay miniaturization and its application to enzymatic reactions. Anal Biochem 1997;246:20-29. [Web of Science][Medline] [Order article via Infotrieve]
  15. Houston JG, Banks M. The chemical-biological interface: developments in automated and miniaturised screening technology. Curr Opin Biotechnol 1997;8:734-740. [Web of Science][Medline] [Order article via Infotrieve]
  16. You AJ, Jackman RJ, Whitesides GM, Schreiber SL. Miniaturized arrayed assay format for detecting small molecule-protein interactions in cells. Chem Biol 1997;4:969-975. [Web of Science][Medline] [Order article via Infotrieve]
  17. Maier E, Meier-Ewert S, Ahmadi AR, Curtis J, Lehrach H. Application of robotic technology to automated sequence fingerprint analysis by oligonucleotide hybridisation. J Biotechnol 1994;35:191-203. [Web of Science][Medline] [Order article via Infotrieve]
  18. Kolb AJ. Introduction. Devlin JP eds. High throughput screening 1997:275-278 Marcel Dekker New York. .
  19. Rose D, Lemmo AV. Challenges in implementing high-density formats for high throughput screening. Lab Automat News 1997;2:12-19.
  20. Fischer-Fruholz S. The handling of nanoliter samples on a chip. Am Lab 1998;Feb:46-51.
  21. Matson RS, Rampal J, Pentoney SL, Anderson PD, Coassin P. Biopolymer synthesis on polypropylene supports: oligonucleotide arrays. Anal Chem 1995;224:110-116.
  22. Lipschutz RJ, Fodor SPA. Advanced DNA sequencing technologies. Curr Opin Struct Biol 1994;4:376-380.
  23. Drobyshev A, Mologina N, Shick V, Pobedimskaya D, Yershov G, Mirzabekov A. Sequence analysis by hybridization with oligonucleotide microchip: identification of beta-thalassemia mutations. Gene 1997;188:45-52. [Web of Science][Medline] [Order article via Infotrieve]
  24. Kozal MJ, Shah N, Shen N, Yang R, Fucini R, Merigan TC, et al. Extensive polymorphisms observed in HIV-1 clade B protease gene using high-density oligonucleotide arrays. Nat Med 1996;2:753-759. [Web of Science][Medline] [Order article via Infotrieve]
  25. de Saizieu A, Certa U, Warrington J, Gray C, Keck W, Mous J. Bacterial transcript imaging by hybridization of total RNA to oligonucleotide arrays. Nat Biotechnol 1998;16:45-48. [Web of Science][Medline] [Order article via Infotrieve]
  26. Eggers M, Ehrlich D. A review of microfabricated devices for gene-based diagnostics. Hematol Pathol 1995;9:1-15. [Web of Science][Medline] [Order article via Infotrieve]
  27. Ekins R, Chu FW. Multianalyte microspot immunoassay–microanalytical "compact disk" of the future. Clin Chem 1991;37:1955-1967. [Abstract/Free Full Text]
  28. Ekins R, Chu FW. Microspot®, array-based, multianalyte binding assays: the ultimate microanalytical technology?. Price CP Newman DJ eds. Principles and practice of immunoassay 2nd ed. 1997:625-646 Stockton New York. .
  29. Gushin D, Yershov G, Zaslavsky A, Gemmell A, Shick V, Proudnikov D, et al. Manual manufacturing of oligonucleotide, DNA, and protein microchips. Anal Biochem 1997;250:203-211. [Web of Science][Medline] [Order article via Infotrieve]
  30. Fodor SPA, Read JL, Pirrung MC, Stryer L, Lu AT, Solas D. Light-directed spatially addressable parallel chemical synthesis. Science 1991;251:767-773. [Abstract/Free Full Text]
  31. Southern EM, Maskos U, Elder JK. Analyzing and comparing nucleic acid sequences by hybridization to arrays of oligonucleotides: evaluation using experimental models. Genomics 1992;13:1008-1017. [Web of Science][Medline] [Order article via Infotrieve]
  32. Livache T, Fouque B, Roget A, Marchand J, Bidan G, Teole R, et al. Polypyrrole DNA chip on a silicon device: example of hepatitis C virus genotyping. Anal Biochem 1998;255:188-194. [Web of Science][Medline] [Order article via Infotrieve]
  33. Beattie KL, Beattie WG, Meng L, Turner SL, Coral-Vasquez R, Smith DD, et al. Advances in genosensor research. Clin Chem 1995;41:700-706. [Abstract/Free Full Text]
  34. Shalon D, Smith SJ, Brown PO. A DNA microarray system for analyzing complex DNA samples using two-color fluorescent probe hybridization. Genome Res 1996;6:639-645. [Abstract/Free Full Text]
  35. Heller RA, Schena M, Chai A, Shalon D, Bedilion T, Gilmore J, et al. Discovery and analysis of inflammatory disease-related genes using cDNA microarrays. Proc Natl Acad Sci U S A 1997;94:2150-2155. [Abstract/Free Full Text]
  36. DeRisi J, Penland L, Brown PO, Bittner ML, Meltzer PS, Ray M, et al. Use of a cDNA microarray to analyse gene expression patterns in human cancer. Nat Genet 1996;14:457-460. [Web of Science][Medline] [Order article via Infotrieve]
  37. Schena M, Shalon D, Heller R, Chai A, Brown PO, Davis RW. Parallel human genome analysis: microarray-based expression monitoring of 1000 genes. Proc Natl Acad Sci U S A 1996;93:10614-10619. [Abstract/Free Full Text]
  38. Schena M, Shalon D, Davis RW, Brown PO. Quantitative monitoring of gene expression patterns with a complementary DNA microarray. Science 1995;270:467-470. [Abstract/Free Full Text]
  39. Maskos U, Southern EM. A novel method for the parallel analysis of multiple mutations in multiple samples. Nucleic Acids Res 1993;21:2269-2270. [Free Full Text]
  40. Chee M, Yang R, Hubbell E, Berno A, Huang XC, Stern D, et al. Accessing genetic information with high-density DNA arrays. Science 1906;274:610-614. [Abstract/Free Full Text]
  41. Lockart DJ, Dong H, Byrne MC, Follettie MT, Gallo MV, Chee MS, et al. Expression monitoring by hybridization to high-density oligonucleotide arrays. Nat Biotechnol 1996;14:1675-1680. [Web of Science][Medline] [Order article via Infotrieve]
  42. Hacia JG, Brody LC, Chee MS, Fodor SPA, Collins FC. Detection of heterozygous mutations in BRCA1 using high density oligonucleotide arrays and two-color fluorescence analysis. Nat Genet 1996;14:441-447. [Web of Science][Medline] [Order article via Infotrieve]
  43. Yershov G, Barsky V, Belgovskiy V, Kirillov E, Kreindlin E, Ivanov I, et al. DNA analysis and diagnostics on oligonucleotide microchips. Proc Natl Acad Sci U S A 1996;93:4913-4918. [Abstract/Free Full Text]
  44. Sheldon EL, Briggs J, Bryan R, Cronin M, Oval M, McGall G, et al. Matrix DNA hybridization. Clin Chem 1993;39:718-719. [Free Full Text]
  45. Cho CY, Moran EJ, Cherry SR, Stephans JC, Fodor SPA, Adams CL, et al. An unnatural biopolymer. Science 1993;261:1303-1305. [Abstract/Free Full Text]
  46. Petersen KE. Silicon as a mechanical material. Proc IEEE 1982;70:420-456.
  47. Hennink SC. Machining lasers. Photonics Spectra 1997;November:116-118.
  48. Jackman RJ, Wilbur JL, Whitesides GM. Fabrication of submicrometer features on curved substrates by microcontact printing. Science 1995;269:664-666. [Abstract/Free Full Text]
  49. Shoji S, Esashi M, Matsuo T. Prototype miniature blood gas analyser fabricated on a silicon wafer. Sensors Actuators 1988;14:101-107.
  50. Harrison DJ, Glavina PG, Manz A. Towards miniaturized electrophoresis and chemical analysis systems on silicon: an alternative to chemical sensors. Sensors Actuators 1993;B10:107-116.
  51. Effenhauser CS, Manz A, Widmer HM. Glass chips for high-speed capillary electrophoresis separations with submicrometer plate heights. Anal Chem 1993;65:2637-2642.
  52. Harrison DJ, Fluri K, Seiler K, Fan Z, Effenhauser CS, Manz A. Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip. Science 1993;261:895-897.
  53. Li PC, Harrison DJ. Transport, manipulation, and reaction of biological cells on-chip using electrokinetic effects. Anal Chem 1997;69:1564-1568. [Medline] [Order article via Infotrieve]
  54. Wilding P, Kricka LJ, Cheng J, Hvichia GE, Shoffner MA, Fortina P. Integrated cell isolation and PCR analysis using microfilter-chambers. Anal Biochem 1998;257:95-100. [Web of Science][Medline] [Order article via Infotrieve]
  55. Tracey MC, Greenaway RS, Das A, Kaye PH, Barnes AJ. A silicon micromachined device for use in blood cell deformability studies. IEEE Trans Biomed Eng 1995;42:751-761. [Web of Science][Medline] [Order article via Infotrieve]
  56. Kricka LJ, Ji X, Nozaki O, Heyner S, Garside WT, Wilding P. Sperm testing with microfabricated glass-capped silicon microchannels. Clin Chem 1994;40:1823-1824. [Free Full Text]
  57. Sobek D, Senturia SD, Gray ML. Microfabricated fused silica flow chambers for flow cytometry. Technical Digest Solid-State Sensor and Actuator Workshop, Hilton Head, SC 1994;:260-263. [Medline] [Order article via Infotrieve]
  58. Hadd AG, Raymond DE, Halliwell JW, Jacobson SC, Ramsey JM. Microchip device for performing enzyme assays. Anal Chem 1997;69:3407-3412. [Medline] [Order article via Infotrieve]
  59. Bruns MW. High-speed portable gas-chromatograph–silicon micromachining. Erdol Kohle Erdgas 1994;47:80-84.
  60. Forssen L, Elderstig H, Eng L, Nordling M. Integration of an amperometric glucose sensor in a uTAS. van den Berg A Bergveld P eds. Micro total analytical systems 1995:203-207 Kluwer Academic Publishers Dordrecht. .
  61. Owicki JC, Bousse LJ, Hafeman DG, Kirk GL, Olson JD, Wada HG, et al. The light-addressable potentiometric sensor. Annu Rev Biophys Biomol Struct 1994;23:87-113. [Web of Science][Medline] [Order article via Infotrieve]
  62. Chiem N, Harrison DJ. Microchip-based capillary electrophoresis for immunoassays: analysis of monoclonal antibodies and theophylline. Anal Chem 1997;69:373-378.
  63. Koutny LB, Schmalzing D, Taylor TA, Fuchs M. Microchip electrophoretic immunoassay for serum cortisol. Anal Chem 1996;68:18-22. [Medline] [Order article via Infotrieve]
  64. Song MI, Iwata K, Yamada M, Yokoyama K, Takeuchi T, Tamiya E, Karube I. Multisample analysis using an array of microreactors for an alternating-current field-enhanced latex immunoassay. Anal Chem 1994;66:778-781. [Medline] [Order article via Infotrieve]
  65. Xue Q, Dunayevskiy YM, Foret F, Karger BL. Integrated multichannel microchip electrospray ionization mass spectrometry: analysis of peptides from on-chip tryptic digestion of melittin. Rapid Commun Mass Spectrom 1997;11:1253-1256. [Web of Science][Medline] [Order article via Infotrieve]
  66. Xue Q, Foret F, Dunayevskiy YM, Zavracky PM, McGruer NE, Karger BL. Multichannel microchip electrospray mass spectrometry. Anal Chem 1997;69:426-430. [Medline] [Order article via Infotrieve]
  67. Feustel A, Muller J, Relling V. A microsystem mass spectrometer. van den Berg A Bergveld P eds. Micro total analytical systems 1995:299-304 Kluwer Academic Publishers Dordrecht. .
  68. Cheng J, Shoffner MA, Hvichia GE, Kricka LJ, Wilding P. Chip PCR. II. Investigation of different PCR amplification systems in microfabricated silicon-glass chips. Nucleic Acids Res 1996;24:380-385. [Abstract/Free Full Text]
  69. Shoffner MA, Cheng J, Hvichia GE, Kricka LJ, Wilding P. Chip PCR. I. Surface passivation of microfabricated silicon-glass chips for PCR. Nucleic Acids Res 1996;24:375-379. [Abstract/Free Full Text]
  70. Northrup MA, Gonzalez C, Lehew S, Hills R. Development of a PCR-microreactor. van den Berg A Bergveld P eds. Micro total analysis systems 1995:139 Kluwer Academic Publishers Dordrecht. .
  71. Taylor TB, Winn-Deen ES, Picozza E, Woudenberg TM, Albin M. Optimization of the performance of the polymerase chain reaction in silicon-based microstructures. Nucleic Acids Res 1997;25:3164-3168. [Abstract/Free Full Text]
  72. Cheng J, Waters LC, Fortina P, Hvichia GE, Ramsey JM, Kricka LJ, et al. Degenerate oligonucleotide primed-polymerase chain reaction and capillary electrophoretic analysis of human DNA on microchip-based devices. Anal Biochem 1998;256:101-106.
  73. Cheng J, Shoffner MA, Mitchelson KR, Kricka LJ, Wilding P. Analysis of ligase chain reaction (LCR) products amplified in a silicon chip using entangled solution capillary electrophoresis (ESCE). J Chromatogr A 1996;732:151-158. [Web of Science][Medline] [Order article via Infotrieve]
  74. Jacobson SC, Ramsey JM. Integrated microdevice for DNA restriction fragment analysis. Anal Chem 1996;68:720-723.
  75. Drexler KE. Molecular directions in nanotechnology. Nanotechnology 1991;2:113-118.
  76. Drexler E, Peterson C, Pergamit G. Unbounding the future. The nanotechnology revolution. New York: William Morrow and Co Inc., 1991:304pp..
  77. Fahy GM. Molecular nanotechnology. Clin Chem 1993;39:2011-2016. [Abstract]
  78. Schnur JM. Lipid tubules: a paradigm for molecularly engineered structures. Science 1993;262:1669-1676. [Abstract/Free Full Text]
  79. Ghadiri MR, Granja JR, Milligan RA, McRee DE, Khazanovich N. Self-assembling organic nanotubes based on a cyclic peptide architecture. Science 1993;366:324-327.
  80. Stevens AM, Richards CJ. A metallocene molecular gear. Tetrahedron Lett 1997;38:7805-7808.
  81. Erickson KA, Wilding P. Evaluation of a novel point-of-care system, the i-STAT portable clinical analyzer. Clin Chem 1993;39:283-287. [Abstract]
  82. Cheung M-C, Goldberg JD, Kan YW. Prenatal diagnosis of sickle cell anaemia and thalassemia by analysis of fetal cells in maternal blood. Nat Genet 1996;14:264-268. [Web of Science][Medline] [Order article via Infotrieve]
  83. Williamson B. Towards prenatal diagnosis. Nat Genet 1996;14:239-240. [Web of Science][Medline] [Order article via Infotrieve]
  84. Kricka LJ, Faro I, Heyner S, Garside WT, Fitzpatrick G, McKinnon G, et al. Micromachining and nanotechnology–a change in practice for the clinical laboratory: glass microchips for sperm selection and in vitro fertilization. Galteau M-M Delwaide P Siest G Henny J eds. Biologie Prospective: 9e Colloque de Pont-a-Mousson 1997:42-46 J Libbey Montrouge. .
  85. Kricka LJ, Faro I, Heyner S, Garside WT, Fitzpatrick G, Wilding P. Micromachined glass-glass microchips for in vitro fertilization. Clin Chem 1995;41:1358-1359. [Free Full Text]
  86. Shoji S, Esashi M. Microfabrication and microsensors. Appl Biochem Biotechnol 1993;41:21-34. [Web of Science][Medline] [Order article via Infotrieve]
  87. Shoji S, Esashi M. Microflow devices and systems. J Micromech Microeng 1994;4:157-171.
  88. Chiem N, Harrison DJ. Microchip systems for immunoassay: an integrated immunoreactor with electrophoretic separation for serum theophylline determination. Clin Chem 1998;44:591-598. [Abstract/Free Full Text]
  89. Eggers M, Hogan M, Reich RK, Lamture J, Ehrlich D, Hollis M, et al. A microchip for quantitative detection of molecules utilizing luminescent and radioisotope reporter groups. Biotechniques 1994;17:516-525. [Web of Science][Medline] [Order article via Infotrieve]
  90. Nakagawa S, Shoji S, Esashi M. A microchemical analyzing system integrated on a silicon chip. Proc IEEE-MEMS Workshop 1990;:89-94.
  91. Walther I, van der Schoot BH, Jeanneret S, Arquint P, de Rooij NF, Gass V, et al. Development of a miniature bioreactor for continuous culture in a space laboratory. J Biotechnol 1994;38:21-32. [Web of Science][Medline] [Order article via Infotrieve]
  92. Cheng J, Kricka LJ, Wilding P. Sample preparation in microstructured devices. Topics Curr Chem 1998;194:215-231.
  93. Sosnowski RG, Tu E, Butler WF, O'Connell JP, Heller MJ. Rapid determination of single base mismatch mutations in DNA hybrids by direct electric field control. Proc Natl Acad Sci U S A 1997;94:1119-1123. [Abstract/Free Full Text]
  94. Waters LC, Jacobson SC, Kroutchinina N, Khandurina J, Foote RS, Ramsey JM. Microchip device for cell lysis, multiplex PCR amplification, and electrophoretic sizing. Anal Chem 1998;70:158-162. [Medline] [Order article via Infotrieve]
  95. Freaney R, McShane A, Keaveny TV, McKenna M, Rabenstein K, Scheller FW, et al. Novel instrumentation for real-time monitoring using miniaturized flow systems with integrated biosensors. Ann Clin Biochem 1997;34:291-302.
  96. van der Schoot BH, Verpoorte E, Jeanneret S, Manz A, de Rooij NF. Microsystems for analysis in flowing solutions. van den Berg A Bergveld P eds. Micro total analytical systems 1995:181-190 Kluwer Academic Publishers Dordrecht. .
  97. Leach M. Discovery on a credit card. Drug Discov Today 1997;2:253-254.
  98. McCormick RM, Nelson RJ, Alonos-Amigo MG, Benvegnu DJ, Hooper HH. Microchannel electrophoretic separations of DNA in injection-molded plastic substrates. Anal Chem 1997;69:2626-2630. [Medline] [Order article via Infotrieve]



The following articles in journals at HighWire Press have cited this article:


Home page
 Proc. Natl. Acad. Sci. USAHome page
A. E. Herr, A. V. Hatch, D. J. Throckmorton, H. M. Tran, J. S. Brennan, W. V. Giannobile, and A. K. Singh
Microfluidic immunoassays as rapid saliva-based clinical diagnostics
PNAS, March 27, 2007; 104(13): 5268 - 5273.
[Abstract] [Full Text] [PDF]

Home page
 Clin. Chem.Home page
H. M.E. Azzazy, M. M.H. Mansour, and S. C. Kazmierczak
Nanodiagnostics: A New Frontier for Clinical Laboratory Medicine
Clin. Chem., July 1, 2006; 52(7): 1238 - 1246.
[Abstract] [Full Text] [PDF]

Home page
 Hum ReprodHome page
R. S. Suh, X. Zhu, N. Phadke, D. A. Ohl, S. Takayama, and G. D. Smith
IVF within microfluidic channels requires lower total numbers and lower concentrations of sperm
Hum. Reprod., February 1, 2006; 21(2): 477 - 483.
[Abstract] [Full Text] [PDF]

Home page
 Clin. Chem.Home page
S. F.Y. Li and L. J. Kricka
Clinical Analysis by Microchip Capillary Electrophoresis
Clin. Chem., January 1, 2006; 52(1): 37 - 45.
[Abstract] [Full Text] [PDF]

Home page
 J AndrolHome page
R. Suh, S. Takayama, and G. D. Smith
Microfluidic Applications for Andrology
J Androl, November 1, 2005; 26(6): 664 - 670.
[Full Text] [PDF]

Home page
 Clin. Chem.Home page
M. J. Pugia, G. Blankenstein, R.-P. Peters, J. A. Profitt, K. Kadel, T. Willms, R. Sommer, H. H. Kuo, and L. S. Schulman
Microfluidic Tool Box as Technology Platform for Hand-Held Diagnostics
Clin. Chem., October 1, 2005; 51(10): 1923 - 1932.
[Abstract] [Full Text] [PDF]

Home page
 Clin. Chem.Home page
T. R. Gingeras, R. Higuchi, L. J. Kricka, Y.M. D. Lo, and C. T. Wittwer
Fifty Years of Molecular (DNA/RNA) Diagnostics
Clin. Chem., March 1, 2005; 51(3): 661 - 671.
[Full Text] [PDF]

Home page
 Clin. Chem.Home page
L. J. Kricka and P. Fortina
Microchips: An All-Language Literature Survey Including Books and Patents
Clin. Chem., September 1, 2002; 48(9): 1620 - 1622.
[Full Text] [PDF]

Home page
 cellbioedHome page
J. R. Lewis, M. S. Kotur, O. Butt, S. Kulcarni, A. A. Riley, N. Ferrell, K. D. Sullivan, and M. Ferrari
Biotechnology Apprenticeship for Secondary-Level Students: Teaching Advanced Cell Culture Techniques for Research
CBE Life Sci Educ, March 1, 2002; 1(1): 26 - 42.
[Abstract] [Full Text] [PDF]

Home page
 Clin. Chem.Home page
A. Dafforn, H. Kirakossian, and K. Lao
Miniaturization of the Luminescent Oxygen Channeling Immunoassay (LOCITM) for Use in Multiplex Array Formats and Other Biochips
Clin. Chem., September 1, 2000; 46(9): 1495 - 1497.
[Full Text] [PDF]

Home page
 J. Clin. Pathol.Home page
R Swaminathan and M Wheeler
Robotics into the millennium
J. Clin. Pathol., January 1, 2000; 53(1): 22 - 26.
[Full Text] [PDF]

Home page
 Clin. Chem.Home page
L. J. Kricka
Nucleic Acid Detection Technologies — Labels, Strategies, and Formats
Clin. Chem., April 1, 1999; 45(4): 453 - 458.
[Abstract] [Full Text] [PDF]

Home page
 Clin. Chem.Home page
C. P. Price
The Evolution of Immunoassay as Seen Through the Journal Clinical Chemistry
Clin. Chem., October 1, 1998; 44(10): 2071 - 2074.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Web of Science (86)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kricka, L. J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kricka, L. J.
Related Collections
Right arrow Oak Ridge Conference
Right arrow Proteomics and Protein Markers
Right arrow Drug Monitoring and Toxicology
Right arrow Endocrinology and Metabolism
Right arrow Automation and Analytical Techniques

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS