Cell-based assays are an important part of the drug discovery process and clinical research.
One of the main hurdles is to design sufficiently robust assays with adequate signal to noise parameters
while maintaining the inherent physiology of the cells and not interfering with the pharmacology of
target being investigated.
A plethora of assays that assess cell viability (or cell heath in general) are commercially available and
can be classified under different categories according to their concepts and principle of reactions. The
assays are valuable tools, however, suffer from a large number of limitations. Some of these limitations
can be procedural or operational, but others can be critical as those related to a poor concept or the lack
of proof of concept of an assay, e.g. those relying on differential permeability of dyes in-and-out of viable
versus compromised cell membranes. While the assays can differentiate between dead and live
cells, most, if not all, of them can just assess the relative performance of cells rather than providing a
clear distinction between healthy and dying cells. The possible impact of relatively high molecular
weight dyes, used in most of the assay, on cell viability has not been addressed. More innovative assays
are needed, and until better alternatives are developed, setup of current cell-based studies and data
interpretation should be made with the limitations in mind. Negative and positive control should be
considered whenever feasible. Also, researchers should use more than one orthogonal method for better
assessment of cell health.