Photodynamic inactivation of bacterial spores on the surface of a photoactive polymer

Novel photoactive polymers were prepared by covalently binding an anthraquinone (AQ) derivative through its 2-position to acid groups of a commercially available ethylene–acrylic acid copolymer, and the photodynamic action of films prepared using these polymers was evaluated. Inoculation of Bacillus cereus spores onto the surface of photoactive polymer films having an AQ content of 35% w/w, followed by exposure to low-power UV-A light, was found to significantly enhance the inactivation of the spores compared with their survival on the surface of inert polymer substrates. It was shown that this effect most likely originates from the photo-induced production of singlet oxygen by the photoactive polymer. These results provide compelling evidence that singlet oxygen produced exogenously by a polymeric substrate can successfully inactivate microbes located on the substrate’s surface.