Light-Powered Nanoconverters Cytotoxic to Breast Cancer Cells

Abstract

We designed and fabricated a light-powered nanoconverter for cytotoxicity toward human breast cancer cells. The nanoconverter was made from highly-fluorescent N-doped carbon nanodots (C-dots), which were covalently conjugated to semiconductive hematite quantum dots (Q-dots). The function of the nanoconverter was to transform the absorbed near-infrared (NIR) irradiation into reactive oxygen species (ROS) which would induce cell death. The principle of operation was based on the photosensitizing properties of C-dots, which have a two-photon absorption cross section. They absorbed NIR irradiation with wavelength in the range of 700–800 nm. The adsorbed energy was upconverted to photoluminescence that is emitted as higher-energy visible light with a maximum wavelength of ∼470 nm and transferred to the Q-dot moiety. The process was accompanied by ejection of electrons from the conduction band of Q-dots and by this mechanism, the nanoconverter produced aqueous superoxide anions, which oxidized organics and generated additional ROS. Our nanoconverter exposed in vitro to cultured human breast cancer HCC1954 cells induced light-dependent cell death as measured using the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The cell death was minimal when the cells were exposed with C-dots alone or if the nanoconverter was exposed with the cells in dark.