Cyanocobalamin (vitamin B12) as insensitive porphyrinoid to solar LED irradiation

Abstract

Cobalamins are cobalt corrin complexes (vitamin B12) with typical porphyrinoid structure and absorption which partly overlaps with the solar spectrum of irradiation. This highly conjugated structure is assumed to have not only the well-known curative action as co-factor and vitamin, but also phototoxicity on dysfunctional, and, in a low extent, on normal cells. Moreover, the cobalamin can have properties as a photosensitizer at appropriate light conditions. The present study aims at characterization of the cyanocobalamin (CNCbl) as a synthetic cobalamin under solar-spectrum irradiation. The photo- and dark cytotoxicity studies were carried out on a normal cell line (BALB/c 3T3, A31) showing no effect due to light application. The photodynamic action of CNCbl due to its porphyrinoid-like structure was not observed. The results on two breast cancer cell lines (MDA-MB-231 and MCF-7) versus a non-tumorigenic cell line (MCF-10) showed similar values for cytotoxicity. A complete loss of viability was observed at approx. 10-4 M CNCbl after 24-hs incubation and soft irradiation (10 J/cm2) for the spectral range 360-960 nm of a LED Helios-iO solar simulator. The cobalt corrin complex showed non-photodynamic ability to reduce the viability of both breast tumor cells depending on the nature of the cell line but not on the light application.