Photoactivated cyclization of aryl-containing enediynes coated gold nanoparticles: enhancement of the DNA cleavage ability of enediynes.

Two novel enediynes containing an aromatic ring and substituted by two thiol functions as end-groups were designed and studied as functionalizing agent of gold nanoparticles. Phototriggered cyclization of the capping agent under UV-visible irradiation was investigated. Interestingly, the length of the thiol-substituted chain was shown to influence significantly the cyclization rate. Depending on the length of the spacer, either polymerization or simple cyclization of the coating agent was evidenced. The present study underscores the possibility of finely controlling the fate of the coating agent (polymerization/cyclization). Nanocomposites were characterized by UV-visible absorption spectroscopy, dynamic light scattering (DLS) technique and transmission electron microscopy (TEM) measurements. Finally, the ability of the colloidal solutions to induce photoinitiated damages to PcDNA3 supercoiled DNA was evaluated. Interestingly, an increase as high as 50% of the DNA cleavage could be registered when adding enediynes-capped gold nanoparticles to solutions of enediynes. In particular, the enhancement of DNA scission was observed in both thermal and photochemical activation modes.