Bioassay

A bioassay is an analytical method to determine the potency or effect of a substance by its effect on living animals or plants (in vivo), or on living cells or tissues (in vitro). A bioassay can be either quantal or quantitative, direct or indirect. If the measured response is binary, the assay is quantal; if not, it is quantitative.

A bioassay may be used to detect biological hazards or to give an assessment of the quality of a mixture. A bioassay is often used to monitor water quality as well as wastewater discharges and its impact on the surroundings. It is also used to assess the environmental impact and safety of new technologies and facilities.^{[citation needed]}

Bioassays are essential in pharmaceutical, medical and agricultural sciences for development and launching of new drugs, vitamins, etc.

A bioassay is a biochemical test to estimate the potency of a sample compound. Usually this potency can only be measured relative to a standard compound. A typical bioassay involves a stimulus (ex. drugs) applied to a subject (ex. animals, tissues, plants). The corresponding response (ex. death) of the subject is thereby triggered and measured.

The first use of a bioassay dates back to the late 19th century, when the foundation of bioassays was laid down by German physician Paul Ehrlich. He introduced the concept of standardization by the reactions of living matter. His bioassay on diphtheria antitoxin (of von Behring and Kitasato Shibasaburō) was the first bioassay to receive recognition. Originally, the antitoxin was studied on guinea pigs, but they were found to have too much individual variation. To control for this, Ehrlich used in vitro experiments with suspended animal tissues, which proved to be sufficiently uniform to allow quantitative assays. With this he established that antitoxin activity was similar to other chemicals, in that warmth and increased concentration increased the speed at which it inactivates diphtheria toxin.

One well known example of a bioassay is the "canary in the coal mine" experiment. To provide advance warning of dangerous levels of methane in the air, miners would take methane-sensitive canaries into coal mines. If the canary died due to a build-up of methane, the miners would leave the area as quickly as possible.

Many early examples of bioassays used animals to test the carcinogenicity of chemicals. In 1915, Yamaigiwa Katsusaburo and Koichi Ichikawa tested the carcinogenicity of coal tar using the inner surface of rabbit's ears.

From the 1940s to the 1960s, animal bioassays were primarily used to test the toxicity and safety of drugs, food additives, and pesticides.