High-content cell death imaging using quantum dot-based TIRF microscopy for the determination of anticancer activity against breast cancer stem cell

We report a two color monitoring of drug-induced cell deaths using total internal reflection fluorescence (TIRF) as a novel method to determine anticancer activity. Instead of cancer cells, breast cancer stem cells (CSCs) were directly tested in the present assay to determine the effective concentration (EC₅₀) values of camptothecin and cisplatin. Phosphatidylserine and HMGB1 protein were concurrently detected to observe apoptotic and necrotic cell death induced by anticancer drugs using quantum dot (Qdot)-antibody conjugates. Only 50-to-100 breast CSCs were consumed at each cell chamber due to the high sensitivity of Qdot-based TIRF. The high sensitivity of Qdot-based TIRF, that enables the consumption of a small number of cells, is advantageous for cost-effective large-scale drug screening. In addition, unlike MTT assay, this approach can provide a more uniform range of EC₅₀ values because the average values of single breast CSCs fluorescence intensities are observed to acquire EC₅₀ values as a function of dose. This research successfully demonstrated the possibility that Qdot-based TIRF can be widely used as an improved alternative to MTT assay for the determination of anticancer drug efficacies.