Bioassays miniaturization

Unlike fluorescence detection, MS-based detection methods maintain their sensitivity when moving from normal-bore chromatography columns to capillary and nano LC systems. MS-based bioassays are therefore particularly suited for miniaturization. Conventional assays are operated at reagent flow rates of 20-50 pL min. By using electrospray MS as readout, flow rates of 1 pL min and lower could be envisaged, which is particularly useful for assays comprising expensive reagents. 

Recent advances in circuit miniaturization and column technology, the development of microprocessors and new concepts in instrument design have allowed sensitive measurement at the parts per billion and parts per trillion levels for many toxicants. This increased sensitivity has focused public attention on the extent of environmental pollution, because many toxic materials present in minute quantities could not be detected until technological advances reached the present state of the art. At present, most pollutants are identified and quantified by chromatography, spectroscopy, and bioassays. 

The need to perform environmental studies on an increasing scale in order to obtain the most comprehensive information on the state of the environment and its processes has led to an increase in the importance and range of rapid miniaturized bioassays, variously known as microbioassays, alternative tests, or second-generation assays.33 The bioassays utilize unicellular or small multicellular organisms that exhibit a specific response on contact with a liquid sample. 

Nelson, E. B. and Craft, C. M. 1992. A miniaturized and rapid bioassay for the selection of soil bacteria suppressive to Pythium blight of turf grasses. Phytopathology 82, 206-210... 

Electrochemical devices have proven very useful for sequence-specific biosensing of DNA. Electrochemical detection of DNA hybridization usually involves monitoring a current response under controlled potential conditions. The hybridization event is commonly detected via the increased current signal of a redox indicator (that recognizes the DNA duplex) or from other hybridization-induced changes in electrochemical parameters (e.g., conductivity or capacitance). Modern electrical DNA hybridization biosensors and bioassays offer remarkable sensitivity, compatibility with modern microfabrication technologies, inherent miniaturization, low cost (disposability), minimal power requirements, and independence of sample turbidity or optical pathway. Such devices are thus extremely attractive for obtaining the sequence-specific information in a simpler, faster, and cheaper manner, compared to traditional hybridization assays. 

MicroChannel Assay A New Generation of Miniaturized Multiplexed Bioassays... 

Over the last decade, there has been a significant increase in laboratory automation and miniaturization, primarily driven by the needs of HTS laboratories. However, the real challenge for lead evaluation is somewhat different from HTS. In HTS, one bioassay tests many hundreds of thousands of compounds in a short span of time. In lead evaluation, smaller numbers of compounds - typically 10-100 - are put through an array of assays that remain relatively constant over a longer time... 

Driven by major advances in microfluidic biosystems, such as the development of micro total analysis systems, microfabricated cell sorters, microseparators for DNA and proteins, and cell-based assays, the microfabrication of biologically meaningful microenvironments is within the scope of recent activities. Bioassays that exploit miniaturized formats are intrinsically advantageous (in part because of their small sample volumes and massively parallel processing), but they heavily rely on defined sur-... 

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