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ABSTRACT: The electronic taste chip (ETC) assay system is a lab-on-a-chip technology that offers a microchip platform on which bead-based immunoassays are performed. Each bead within the array serves as its own independent self-contained "microreactor" system, with its selectivity determined by the specificity of the antibody that it hosts. The bead-loaded chip is sandwiched between two optically transparent polymethylmethacrylate inserts, packaged within a metal casing described here as the "flow cell." This flow cell allows for delivery of sample and detecting reagents to the microchip and the associated beads. Images of fluorescent beads are captured with a digital video chip and analyzed to facilitate detection and, ultimately, quantitation of analytes in complex fluids. This chapter describes the application of the ETC system for the detection and measurement of interleukin (IL)-6.
Methods in molecular biology (Clifton, N.J.) 02/2007; 385:131-44.
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Shifeng Li,
Pierre N Floriano,
Nicolaos Christodoulides,
David Y Fozdar,
Dongbing Shao,
Mehnaaz F Ali,
Priya Dharshan,
Sanghamitra Mohanty, Dean Neikirk,
John T McDevitt,
Shaochen Chen
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ABSTRACT: This paper presents disposable protein analysis chips with single- or four-chamber-constructed from poly(dimethylsiloxane) (PDMS) and silicon. The chips are composed of a multilayer stack of PDMS layers that sandwich a silicon microchip. This inner silicon chip features an etched array of micro-cavities hosting polymeric beads. The sample is introduced into the fluid network through the top PDMS layer, where it is directed to the bead chamber. After reaction of the analyte with the probe beads, the signal generated on the beads is captured with a CCD camera, digitally processed, and analyzed. An established bead-based fluorescent assay for C-reactive protein (CRP) was used here to characterize these hybrid chips. The detection limit of the single-chamber protein chip was found to be 1 ng/ml. Additionally, using a back pressure compensation method, the signals from each chamber of the four-chamber chip were found to fall within 10% of each other.
Biosensors and Bioelectronics 11/2005; 21(4):574-80. · 5.60 Impact Factor
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ABSTRACT: The development of a novel chip-based multianalyte detection system with a cardiac theme is reported. This work follows the initial reports of "electronic taste chips" whereby multiple solution-phase analytes such as acids, bases, metal cations, and biological cofactors were detected and quantitated. The newly fashioned "cardiac chip" exploits a geometry that allows for isolation and entrapment of single polymeric spheres in micromachined pits while providing to each bead the rapid introduction of a series of reagents/washes through microfluidic structures. The combination of these miniaturized components fosters the completion of complex assays with short analysis times using small sample volumes. Optical signals derived from single beads are used to complete immunological tests that yield outstanding assay characteristics. The power and utility of this new methodology is demonstrated here for the simultaneous detection of the cardiac risk factors, C-reactive protein and interleukin-6, in human serum samples. This demonstration represents the first important step toward the development of a useful cardiac chip that targets numerous risk factors concurrently and one that can be customized readily for specific clinical settings.
Analytical Chemistry 08/2002; 74(13):3030-6. · 5.86 Impact Factor
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ABSTRACT: We report the development of a sensor for rapidly and simultaneously measuring multiple sugars in aqueous samples. In this strategy, enzyme-based assays are localized within an array of individually addressable sites on a micromachined silicon chip. Microspheres derivatized with monosaccharide-specific dehydrogenases are distributed to pyramidal cavities anisotropically etched in a wafer of silicon (100) and are exposed to sample solution that is forced through the cavities by a liquid chromatography pumping system. Production of fluorescent reporter molecules is monitored under stopped-flow conditions when localized dehydrogenase enzyme systems are exposed to their target sugars. We demonstrate the capability of this analysis strategy to quantify β--glucose and β--galactose at low micromolar to millimolar levels, with no detectable cross-talk between assay sites. Analysis is achieved either through fluorescence detection of an initial dehydrogenase product (NADH, NADPH) or by production of a secondary fluorescent product created by hydride transfer from the reduced nicotinamide cofactor to a fluorogenic reagent. The array format of this sensor provides capabilities for redundant analysis of sugars and for monitoring levels of other solution components known to affect the activity of enzymes. The use of this strategy to normalize raw fluorescence signals is demonstrated by the determination of glucose and pH on a single chip. Alternatively, uncertainties in the activity of an immobilized enzyme can be accounted for using standard additions, an approach used here in the determination of serum glucose.
Analytical Biochemistry 07/2001; · 3.00 Impact Factor
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