Impairing the radioresistance of cancer cells by hydrogenated nanodiamonds

Hydrogenated nanodiamonds (H-NDs) exhibit a negative electron affinity that confers a high reactivity with oxygen species and a positive charge in aqueous solutions. It allows electron emission from H-NDs following irradiation by photons and in consequence may enhance the effects of radiation on cancer cells. By using three human radioresistant cancer cell lines, we showed a potentialization of cytotoxicity after a co-exposure to H-NDs and irradiation; an event occurring through the induction of DNA damage and reactive oxygen species. This occurred together with a decrease in cell impedance, the activation of G(1)/S, an unlocking of G(2) cell cycle check-points and early low cell death rate. At later stage of exposure, persistent increases in heterochromatinization, large gamma-H2AX foci and p-galactosidase activity were detected providing evidence of cells' entrance into senescence. Similar potentialization was observed with neocarzinostatin (NCS), a radiomimetic drug. This original finding underlines a wide clinical potential of H-NDs to intensify radiation effects on radio-resistant cancer cells. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).