BioTek July 2019 - 4

Microplate Reader Assays for
Cell Proliferation
Microplate readers provide a powerful tool for accomplishing many
cell proliferation assays in a short amount of time.
Caitlin Smith
Measurement of cell proliferation is essential for labs
that routinely use cell cultures as an experimental
system-and not only for routine maintenance of
cell health. Accurately assessing the effect of various drugs or drug candidates on cell proliferation,
for example, is an important way to unlock secrets of
anticancer weapons, and to learn about the origins
of cancer itself.

and widely used assay for cell proliferation measures
the metabolic activity of cells using tetrazolium
salts (for example, MTT, MTS, XTT, and WST-1; and
similar resazurin redox dyes such as Alamar Blue).
Tetrazolium salts become reduced to formazan in
the presence of cells that are metabolically active.
In MTT assays, for example, the chemical reduction
produces a purple formazan crystal when dehydrogenase enzymes cleave the tetrazolium ring.
After solubilizing the crystals, colorimetric signals
-proportional to cell number and to metabolic
activity-are easily read by microplate spectrophotometers and are effective tools for measuring the
effects of proliferation inhibitors.

Generally, cell proliferation assays measure the number of cells (or the change in the proportion of cells)
that are dividing. The four main types of cell proliferation assays differ in the nature of their endpoint
measurements, whether it be metabolic activity,
DNA synthesis, ATP concentration, or the presence
of markers for cell proliferation. All of these assay
types are adaptable to microplate readers and multiwell plates and are available as convenient assay
kits from multiple vendors, allowing researchers to
take advantage of automation and higher-throughput technology.

Assaying metabolic activity
Cells that are actively proliferating have higher metabolic rates than those that are not. A convenient

Figure 1. MTT reduction in live cells by mitochondrial reductase results in the
formation of insoluble formazan, characterized by high absorptivity at 570 nm.

BioTek July 2019

Table of Contents for the Digital Edition of BioTek July 2019