Assays are essentially tests. Bioassays are tests that are used to measure the potency of an active ingredient in the drug by measuring its effects on cells, tissues, or living animals. Cell-Based Assays, as the name suggests, are tests that are performed within a cell. Cell-Based Assays are conducted for several reasons. Sometimes the cytotoxicity of a substance (that is, whether the substance is toxic to the cells) is measured. Other times, as mentioned before, they are used to test at what concentration a substance produces the optimal effects in the test subject. A variety of parameters can be measured through a cell-based assay: radioactivity, luminescence, absorbance, fluorescence, etc. The key feature of a cell-based assay is that it must produce a detectable signal so that the parameter being measured can be determined. Cell-based assays employ a series of reagents for this purpose. What matters the most is the robustness of the signal. It is also important that the signal does not go off with the control experiment when the standard procedure is being tested. However, the same detectable signal must be produced when the same concentration of the substance is tested again. What this means is that the reproducibility of the assays is a necessary factor.
