The water-soluble fullerene derivative ‘Radical Sponge®’ exerts cytoprotective action against UVA irradiation but not visible-light-catalyzed cytotoxicity in human skin keratinocytes

Fullerene was entrapped in polyvinylpyrrolidone of 60-80 kDa at a molar ratio range of 0.42–0.67:1, resulting in a water-soluble derivative with a mean particle diameter of about 688 nm, named ‘Radical Sponge®’ because of its ROS-scavenging ability as previously demonstrated, and examined in the present study for its photo-biological actions toward human skin keratinocytes HaCaT. The keratinocytes were repeatedly irradiated with a visible light of wavelengths of 400–2000 nm (approximately 19,800 lux) in the presence or absence of Radical Sponge® of 25–75 μM and did not exhibit any photo-cytotoxicity due to coexistent Radical Sponge® as compared with the sham-irradiation control. Radical Sponge® exerted a more marked cytoprotection at doses of 10–40 μM against UVA irradiation of 30 J/cm2 when it was pre-irradiationally administered and rinsed out immediately before the irradiation, than when administered only during or after the irradiation, indicating the preventive rather than therapeutic or ray-sheltering effect of Radical Sponge® on UVA injuries. Cytoprotection by Radical Sponge® against UVA was achieved at the advisable range doses of 10–40 μM in contrast to no effect of polyvinylpyrrolidone alone; its dose-dependency was advantageous over that of VC-IP, a tetra-alkyl-esterized provitamin C, which became less cytoprotective above 20 μM. Thus, Radical Sponge® is expected as an anti-UVA-preventive agent without visible-light-catalyzed cytotoxicity toward human skin keratinocytes.

Radical Sponge®, a water-soluble derivative of fullerene is composed of the purified fullerene BioFullerene® and PVP (polyvinylpyrrolidone), which exhibited a particle diameter of 120–230 nm in the dry state (shown in another photograph) in contrast to mean 688 nm in the aqueous dispersion (the MicroTrak histogram shown in the text), could protect human skin keratinocytes HaCaT from UVA injures via the preventive effect without any cytotoxicity or phototoxicity at 10–40 μM.Figure optionsDownload as PowerPoint slide