Bioassay

Bioassay (commonly used shorthand for biological assay), or biological standardisation is a type of scientific experiment. Bioassays are typically conducted to measure the effects of some substance on a living organism and are essential in the development of new drugs, and in monitoring environmental pollutants. Both are procedures by which the potency or the nature of a substance is estimated by studying its effects on living matter.

Use

Bioassays are procedures that can determine the concentration of purity or biological activity of a substance such as vitamin, hormone, and plant growth factor. While measuring the effect on an organism, tissue cells, enzymes or the receptor is preparing to be compared to a standard precipitation. Bioassays may be qualitative or quantitative. Qualitative bioassays are used for assessing the physical effects of a substance that may not be quantified, such as abnormal development or deformity. An example of a qualitative bioassay includes Arnold Adolph Berthold's famous experiment on castrated chickens. This analysis found that by removing the testes of a chicken, it would not develop into a rooster because the endocrine signals necessary for this process were not available. Quantitative bioassays involve estimation of the concentration or potency of a substance by measurement of the biological response that it produces. Quantitative bioassays are typically analyzed using the methods of biostatistics.

Definition

"It is the comparable estimation of the nature, constitution or potency of the active principles with that of the standard drug, by means of the reaction on a living matter such as whole animal, isolated tissue or organism."

Purpose

1. measurement of the pharmacological activity of new or chemically undefined substances
2. investigation of the function of endogenous mediators
3. determination of the side-effect profile, including the degree of drug toxicity
4. measurement of the concentration of known substances (alternatives to the use of whole animals have made this use obsolete)
5. assessing the amount of pollutants being released by a particular source, such as wastewater or urban runoff.

Types

Bioassays are of two types:

Quantal

A quantal assay involves an "all or none response". For example: Insulin induced hypoglycemic convulsive reaction or the cardiac arrest caused by digitalis. In both the cases, the end point is an all or none response e.g.—either convuslion occurs or doesn't occur; similarly is with cardiac arrest.

Graded

Graded assays are based on the observation that there is a proportionate increase in the observed response following an increase in the concentration or dose. The parameters employed in such bioassays are based on the nature of the effect the substance is expected to produce. For example: contraction of smooth muscle preparation for assaying histamine or the study of blood pressure response in case of adrenaline.

A graded bioassay can be performed by employing any of the below-mentioned techniques. The choice of procedure depends on:

1. the precision of the assay required
2. the quantity of the sample substance available
3. the availability of the experimental animals.

Techniques

1. Matching Bioassay
2. Interpolation Method
3. Bracketing Method
4. Multiple Point Bioassay
5. Six Point Assay

Environmental bioassays

Environmental bioassays are generally a broad-range survey of toxicity. A toxicity identification evaluation is conducted to determine what the relevant toxicants are. Although bioassays are beneficial in determining the biological activity within an organism, they can often be time-consuming and laborious. Organism-specific factors may result in data that is not applicable to others in that species. For these reasons, other biological techniques are often employed, including radioimmunoassays. See bioindicator.

Water pollution control requirements in the United States require some industrial dischargers and municipal sewage treatment plants to conduct bioassays. These procedures, called whole effluent toxicity tests, include acute toxicity tests as well as chronic test methods. The methods involve exposing living aquatic organisms to samples of wastewater.

See also

• Dilution assay
• Drug discovery
• Pharmacodynamics
• Pharmacokinetics
• Water quality

External links

• Whole Effluent Toxicity Basics (PowerPoint file) - New Jersey Department of Environmental Protectionet:Biotest

zh:生物檢定法