Biological Assay Detection Technologies
Authored by: Paul Taylor, Boehringer Ingelheim Inc.
Detection technologies comprise a broad range of techniques designed to quantitate analytes resulting from chemical or biological processes, including biological assays. Typically, the aim of a biological assay is to measure the effect of a substance on a biological system which has been configured in vitro in either a cell-based or biochemical format. While cell-based assays are sometimes erroneously referred to as in vivo, in reality the more accurate term is ex vivo, due to the fact that the cells have been cultured outside of a living organism. Biological assays are configured as such to gain insights into physiological events that are typically associated with disease states and are commonly employed at all stages of preclinical drug discovery. The substances modulating biological processes can be either stimulatory or inhibitory and the detection technology chosen is intended to provide an accurate read out of the respective effect.
Most commonly, biological assays are run in microtiter assay plates with densities of 96, 384, 1536 or 3456 wells/plate. The plates are used in high-throughput screening (HTS) which is a process that utilizes a combination of robotics, liquid handlers, plate readers, incubators, washers, shakers, barcode readers and other devices for assembling assay components and compounds in high throughput and collecting the resulting data. 
Many widely utilized detection technologies are a form of optical information gathering. These can be divided into four main classes: fluorescence, luminescence, radiometric and absorbance. The links at the end of this article provide more detail on specific technologies. In all cases, examples of assay formats utilizing particular detection technologies are provided and are described in more detail in the literature. Other lesser-used detection formats that have seen more specialized application are automated patch clamping, label free and rubidium flux.
Monitoring of assays is usually accomplished with the use of reagents whose optical properties change following a chemical or biological event. Care needs to be taken to ensure that interferences from compounds (either autofluorescent or quenching) and inner filter effects are minimized whenever possible.
- Fluorescence Detection Technologies
- Fluorescence Intensity (FLINT)
- Fluorescence Polarization (FP)
- Fluorescence Correlation Spectroscopy (FCS)
- Fluorescence Resonance Energy Transfer (FRET)
- Dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA)
- Homogenous Time Resolved Fluorescence (HTRF)
- LANCE Ultra™
- Fluorescence Lifetime Analysis (FLA)
- Luminescence Detection Technologies
- Radiometric Detection Technologies
- Absorbance Detection Technologies
- Other Technologies
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