Toxicity of C60 fullerene-cisplatin nanocomplex against Lewis lung carcinoma cells

Cisplatin (Cis-Pt) is the cytotoxic agent widely used against tumors of various origin, but its therapeutic efficiency is substantially limited by a non-selective effect and high toxicity. Conjugation of Cis-Pt with nanocarriers is thought to be one option to enable drug targeting. The aim of this study was to estimate toxic effects of the nanocomplex formed by noncovalent interaction of C₆₀ fullerene with Cis-Pt against Lewis lung carcinoma (LLC) cells in comparison with free drug. Scanning tunneling microscopy showed that the minimum size of C₆₀-Cis-Pt nanoparticles in aqueous colloid solution was 1.1 nm whereas that of C₆₀ fullerene was 0.72 nm, thus confirming formation of the nanocomplex. The cytotoxic effect of C₆₀-Cis-Pt nanocomplex against LLC cells was shown to be higher with IC₅₀ values 3.3 and 4.5 times lower at 48 h and 72 h, respectively, as compared to the free drug. 12.5 µM Cis-Pt had no effect on LLC cell viability and morphology while C₆₀-Cis-Pt nanocomplex in Cis-Pt-equivalent concentration substantially decreased the cell viability, impaired their shape and adhesion, inhibited migration and induced accumulation in proapoptotic subG1 phase. Apoptosis induced by the C₆₀-Cis-Pt nanocomplex was confirmed by caspase 3/7 activation and externalization of phosphatidylserine on the outer surface of LLC cells with the double Annexin V-FITC/PI staining. We assume that C₆₀ fullerene as a component of the C₆₀-Cis-Pt nanocomplex promoted Cis-Pt entry and intracellular accumulation thus contributing to intensification of the drug's toxic effect against lung cancer cells.