Photobactericidal films from porphyrins grafted to alkylated cellulose – synthesis and bactericidal properties

Two series of porphyrinic cellulose laurate esters plastic films, where the photosensitizers are covalently linked to the cellulosic polymer have been synthesised by using a “one-pot, two-step” esterification reaction. The photosensitizers were first covalently bounded to the cellulosic polymer using either 4- or 11-carbon spacer arms. The porphyrinic plastic films were then obtained by a second esterification with lauric acid. The reaction was studied according to reaction time, temperature, lauric acid amount, pyridine playing the role proton trapping base. Para-toluenesulfonylchloride has been proved to be a powerful activating agent for this reaction. The drawback of the steric hindrance of the porphyrinic macrocycle towards cellulosic hydroxyl groups has been overcome by increasing the number of carbon of spacer arms from 4- to 11-carbons. The photobactericidal activity of these materials was evaluated against Gram positive and Gram negative strains bacteria. First results show that these new plastic films display photobactericidal activity for porphyrin grafting percentage higher than 0.16, whereas the non-porphyrinic control allowed full growth of bacteria. These materials could be an alternative in order to overcome the growing bacterial multiresistance to classical antibiotics.