Automated Handheld Instrument Improves Counting Precision Across Multiple Cell Lines

Abstract

Counting cells is often a necessary but tedious step for in vitro cell culture. Cell counts are important for monitoring cell health and proliferation rate, assessing immortalization or transformation, seeding cells for subsequent experiments, transfection or infection, and preparing for cell-based assays. It is important that cell counts be accurate, consistent, and fast, particularly for quantitative measurements of cellular responses. Despite this need for speed and accuracy in cell counting, a survey (1) of 400 researchers who count cells revealed that 71% use a hemocytometer. While hemocytometry is inexpensive, it is laborious and subject to user bias and misuse that results in inaccurate counts. Hemocytometers are made of special optical glass on which cell suspensions are loaded in specified volumes and counted under a microscope. Sources of error in hemocytometry include uneven cell distribution in the sample; too many or too few cells in the sample; subjective decisions as to whether a given cell falls within the defined counting area; contamination of the hemocytometer; user-to-user variation; and variation of hemocytometer filling rate (2). To alleviate the tedium associated with manual counting, 29% of the researchers in the survey count cells using automated cell counting devices; these include vision-based counters—systems that detect cells using the Coulter principle—and flow cytometers (1). For most researchers, the main barrier to using an automated system is the price associated with these large benchtop instruments (1). The ScepterTM cell counter (Millipore) combines the ease of automated instrumentation and the accuracy of Coulter impedance-based particle detection (3) in an affordable, handheld format (Figure 1). The instrument, which is the size of a pipet, uses a combination of analog and digital hardware for sensing, signal processing, data storage, and graphical display. The disposable tip (Figure 1, inset) has a microfabricated, cell-sensing zone that can discriminate cell size and cell volume at sub-micron and sub-picoliter resolution. Enhanced with precision liquid-handling channels and electronics, the Scepter cell counter graphically displays cell population statistics as histograms. Counting is typically completed in less than 20 seconds.