BioTek July 2019 - 12

An Absorbance-based
Cytotoxicity Assay Using
Water-Soluble Tetrazolium Salts
A better way to quantitate cell numbers from proliferation or
cytotoxicity studies.
Paul Held, Ph.D.
such as trypsin prior to quantitation. Dispersed cells
can be directly quantitated both manually with the
use of a microscope and a hemocytometer or in an
automated cell counter. These methods are slow and
labor intensive, requiring individual samples to be
quantitated individually.

Abstract
Cellular proliferation and cytotoxicity studies are
the mainstay for cell biology and cancer research.
Cell proliferation research involves the assessment
of different molecules ability to elicit cell growth
and multiplication, while antitumor chemotherapy
studies usually involves the investigation of the ability of agents to specifically kill tumor cells. In either
case, an assessment of the change in cell number
over time is a critical component in the research.
Here we describe the use of the Synergy Multi-Mode
Microplate Reader to quantitate cells using WST-8
cell counting kit from Dojindo.

There are a number of different indirect methodologies to quantitate cell number with large numbers
of samples using microplates. Simple total protein
and nucleic acid assays that indirectly provide information regarding cell number or more specifically
changes in cell number are based on the concept
that cells on average have a constant amount of these
polymers. Increases or decreases of these polymers
would be indicative of cellular proliferation or cytotoxicity respectively. However, these assays do not
necessarily provide information regarding the viability of the cells in question and several "live cell" assays
have been developed. One of the first methods developed is the incorporation of 3H-thymidine. Only
live cells will incorporate this traceable radioactive

Introduction
Quantitation of tissue culture cells has been the
hallmark for the determination of efficacy of agents
that either promote or inhibit cell growth. While
cells grown in suspension can be counted directly,
most tissue cultures are grown in monolayer culture,
which requires dispersal using proteolytic agents

BioTek July 2019

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