In this study, we describe a photocatalytic system based on spherical fluorescent carbon-core nanoparticles (nanodots) that can be activated with ultraviolet radiation. The carbon nanodots with a poly(propionylethylenimine-co-ethylenimine) coating were investigated in human prostate adenocarcinoma (Du145 and PC3) cell cultures in vitro. The cells become more sensitive to ultraviolet radiation when preincubated with the nanodots. The inverse slope of the cell survival curves is about 20-30% lower for the carbon nanodots and radiation compared to that for the radiation alone. Such photoactivatable carbon nanodots can be suggested for use in photocatalytic and photodynamic applications. (C) 2013 AIP Publishing LLC.