Selection of an Optimal Cytotoxicity Assay for Undergraduate Research

Undergraduate research is a valuable tool to demonstrate both the dedication and time required to be a successful biologist. One area of research that has intrigued students over the last several years is cytotoxicity. However, at smaller undergraduate institutions, the time, training, and funding available for these research studies may be limited. Direct counting of cells is tedious and leads to mistakes, and although there are now several colorimetric toxicity assays, some have several steps and require near-perfect pipetting skills. To identify the most reproducible and affordable method(s) for undergraduate students to perform cell-based toxicity studies, we compared three colorimetric assays to counting viable cells directly. Using a breast cancer model system, students applied cantharidin to two different breast cancer cell lines, MCF-7 and MDA-MB231, and performed MTT, resazurin, and crystal violet colorimetric assays or counted viable cells directly. We hypothesized that the MTT assay would be the most reproducible assay. Our results indicate that the crystal violet assay was not as reproducible as direct counting of cells, and therefore, not the best assay to use for toxicity tests. In contrast, the MTT and resazurin assays were highly reproducible and relatively low cost, and thus ideal assays for student research.