A novel curcumin gallium complex as photosensitizer in photodynamic therapy: Synthesis, structural and physicochemical characterization, photophysical properties and in vitro studies against breast cancer cells

The synthesis, detailed structural and physicochemical characterization of a novel Ga(III)-curcumin complex with the ancillary aromatic chelator 1,10-phenanthroline is presented herein. The complex constitutes the only crystallographically characterized structure with Ga(III) as the metal core and a curcuminoid as the ligand. The photophysical properties of the complex revealed a significant red-shift in absorption, increased photostability and comparable free radical generation compared to plain curcumin. They all are highly desirable properties for a photosensitizer. Photodynamic therapy is a non-invasive method for the treatment of various cancers which requires a photosensitizing molecule able to generate reactive oxygen species upon light irradiation. Curcumin has been studied as a promising photosensitizer against cancer cells and metal complexation has been shown to increase its photodynamic effect. The novel curcumin-Ga complex exhibited no dark toxicity at low concentrations against MCF-7 breast cancer cells and upon irradiation a light-dose dependent decrease in cell survival was observed. This photodynamic effect was superior to the one caused by curcumin alone making the Ga(III)-curcumin complex a more promising photosensitizer than the parent ligand.