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A method for the quantitation of the effects on a biological system by its exposure to a substance, as well as the quantitation of the concentration of a substance by some observable effect on a biological system. The biological material in which the effect is measured can range from subcellular components and microorganisms to groups of animals. The substance can be stimulatory, such as an ion increasing taxis behavior in certain protozoans, or inhibitory, such as an antibiotic for bacterial growth. Bioassays are most frequently used when there is a number of steps, usually poorly understood, between the substance and the behavior observed, or when the substance is a complex mixture of materials and it is not clear what the active components are. Bioassays can be replaced, in time, by either a more direct measure of concentration of the active principle, such as an analytical method (for example, mass spectrometry, high-pressure liquid chromatography, radioimmunoassay), or a more direct measurement of the effect, such as binding to a surface receptor in the case of many drugs, as the substance or its mechanism of action is better characterized.

Assays to quantitate the effects of an exposure model the effect of a substance in the real world. Complex biological responses can be estimated by laboratory culture tests, which use, for example, bacteria or cells cultured in a petri dish (usually to model an effect either on the organism of interest, such as bacteria, or on some basic cellular function); by tissue or organ culture, which isolates pieces of tissue or whole organs in a petri dish (usually to model organ function); or in whole animals (usually to model complex organismic relationships).


(analytical chemistry)
A method for quantitatively determining the concentration of a substance by its effect on the growth of a suitable animal, plant, or microorganism under controlled conditions.
References in periodicals archive ?
Table 1: Incorporating New Technologies into Bioassay Development
Interaction of nucleopolyhedrovirus (SfMNPV) and the insecticide spinosad in feeding bioassays with Spodoptera frugiperda 3rd instars.
White-rotting fungi usually cause lower mass losses in softwoods than brown-rotting fungi in bioassays, and this occurred with P.
An inexpensive and rapid bioassay would be a useful screening tool with which to assess potential decontaminating agents for subsequent, more definitive testing by chemical analysis.
and a network of distributors worldwide, Cisbio Bioassays is a member of the Belgium-based IBA group.
CEKCL was tested using the brine shrimp lethality bioassay, followed by evaluation of antihypertensive activity on anaesthetized rats.
The bioassay procedure was as follows: a 2-mL overnight culture was used to inoculate 18 mL of fresh selective sc medium.
Screening bioassays must be inexpensive, rapid, and easy to operate, have broad application to numerous target species, be reproducible and statistically valid, and require a limited amount of time and space.
Chronic effects are estimated by dose-response studies on animals, carcinogenic effects are estimated by a carcino-genesis bioassay, and acute toxic effects are estimated by LD5O studies of observation of accidents.
Culture of toxic organisms simplifies bulk toxin production for analytical calibration standards, bioassay development, toxicity testing, and investigation of toxin biosynthetic pathways by stable isotope labelling, NMR, and molecular biological/genomic methods.
In vitro cellular bioassays are useful for screening because they are relatively fast and inexpensive to conduct.
In the October Environmental Health Perspectives, the NIEHS researchers report that p53 knockout mice exposed to such mutagenic carcinogens develop the same tumors within 6 months that normal rodents develop during the standard, 2-year bioassays.