Bioassay techniques • 1. BIOASSAY TECHNIQUES Submitted to Dr. OfVPT, Pookode. Submitted by Dr. MVSc scholar, Dept. OfVPT, Pookode. The Secret Holocaust Diaries here. • Biological assessment.

• Estimation or determination of concentration or potency of a physical, chemical or biological substance (agent) by means of measuring and comparing the magnitude of the response of the test with that of standard over a suitable biological system under standard set of conditions. • The estimation of the concentration or potency of a substance by measurement of the biological response that it produces. Sound Replacer Download Pc. • The structure of bioassay: STIMULUS-applied to subject. RESPONSE-of the subject to the stimulus. • The purpose of bioassay. • To ascertain the potency of a drug and hence it serves as the quantitative part of any screening procedure (Research). • To standardize drugs, vaccines, toxins or poisons, disinfectants, antiseptics etc., so that each contains the uniform specified pharmacological activity.

(standardization required as these are all used over biological system in some or other form.) • Helps to determine the specificity of a compound to be used e.g. Penicillin's are effective against Gram +ve. But not on Gram –ve. • From the clinical point of view, bioassay may help in the diagnosis of various conditions. Gonadotrophins for pregnancy. • Sometimes the chemical composition of samples are different but have same biological activity. • Certain complex compounds likeVitamin B-12 which can't be analysed by simple assay techniques can be effectively estimated by Bioassays.

• For samples where no other methods of assays are available. • Principle of Bioassay. To compare the test substance with the International Standard preparation of the same and to find out how much test substance is required to produce the same biological effect, as produced by the standard. • The standards are internationally accepted samples of drugs maintained and recommended by the Expert Committee of the Biological Standardization of W.H.O. They represent the fixed units of activity (definite weight of preparation) for drugs. • In India • standard drugs are maintained in Government institutions like 1. Central Drug Research Institute, Lucknow 2.

Central Drug Laboratory, Calcutta. • Classification of bioassay. • In vitro techniques: • These techniques employ a cell culture of recommended biological system to study the effect of compound under standard condition not similar to that of living environment. Here the cell culture survives by utilization of the nutrition in the media. • Ex: use of stem cells, cell culture, microbes (bacteria) etc. • In vivo techniques: • These techniques employ a living animal recommended for the purpose of assay. The techniques aims to study the biological effect or response of the compound under screening in a living system directly.

Principles Involved in Bioassay by different Methods. View PDF Download PDF. Four Point Bioassay. From the clinical point of view, bioassay may help in the. Three to four doses of the standard antagonist are used and. Principles and Methods of Bioassay.

• Ex: By use of rodents, rabbits etc. • Ex vivo techniques: • These techniques employ a tissue or cells of recommended living system to study the effect of compound under test in suitable conditions within the stipulated time of organ survival outside the body. • Ex: Use of any isolated organ from animals in a glass ware to study the effect of compound within the period of its survival outside the living body with provision of only oxygen, glucose and isotonic salts to maintain cell & cell organelles integrity. • Types of bioassay. • Qualitative bioassay is used for assessing the physical effects of a substance that may not be quantified, such as abnormal development or deformity. Eg: 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 concentration/potency of a substance by measurement of the biological response it produces.These bioassays are typically analyzed using the methods of biostatistics. • Bioassay Methods. Graded Response Assay:: In these assays, as the dose increases there is an equivalent rise in response.The potency is estimated by comparing theTest sample responses with the standard response curve. Of unknown=Threshold dose of standard/threshold dose of test x Conc.

Acetyl-choline producing contraction in the muscle of frog Rectus abdominis. End Point or Quantal Assay: As the name indicates, the threshold dose of the sample required to elicit a complete or a particular pharmacological effect is determined and compared with standard. • E.g., Digitalis producing cardiac arrest.