C60 fullerene accumulation in human leukemic cells and perspectives of LED-mediated photodynamic therapy

Recent progress in nanobiotechnology has attracted interest to a biomedical application of the carbon nanostructure C-60 fullerene since it possesses a unique structure and versatile biological activity. C-60 fullerene potential application in the frame of cancer photodynamic therapy (PDT) relies on rapid development of new light sources as well as on better understanding of the fullerene interaction with cells. The aim of this study was to analyze C-60 fullerene effects on human leukemic cells (CCRF-CEM) in combination with high power single chip light-emitting diodes (LEDs) light irradiation of different wavelengths: ultraviolet (UV, 365 nm), violet (405 nm), green (515 nm) and red (632 nm). The time-dependent accumulation of fullerene C-60 in CCRF-CEM cells up to 250 ng/10(6) cells at 24 h with predominant localization within mitochondria was demonstrated with immunocytochemical staining and liquid chromatography mass spectrometry. In a cell viability assay we studied photoexcitation of the accumulated C-60 nanostructures with ultraviolet or violet LEDs and could prove that significant phototoxic effects did arise. A less pronounced C-60 fullerene phototoxic effect was observed after irradiation with green, and no effect was detected with red light. A C-60 fullerene photoactivation with violet light induced substantial ROS generation and apoptotic cell death, confirmed by caspase3/7 activation and plasma membrane phosphatidylserine externalization. Our work proved C-60 fullerene ability to induce apoptosis of leukemic cells after photoexcitation with high power single chip 405 nm LED as a light source. This underlined the potential for application of C-60 nanostructure as a photosensitizer for anticancer therapy.