The photosensitisation of Escherichia coli using disulphonated aluminium phthalocyanine

Abstract

The lethal photosensitisation of the Gram-negative bacterium Escherichia coli using the anionic photosensitiser disulphonated aluminium phthalocyanine (AlPcS 2) and red laser or LED light is investigated. Disulphonated aluminium phthalocyanine can reduce the cell viability of E. coli but cannot achieve complete inactivation under the experimental conditions used. The greatest reduction in the viable count of E. coli is achieved by exposure to fractionated LED light (energy dose, 2.4 J; energy density, 4.0 mW cm −2; fractionated, illumination time, 2 min; dark period, 2 min) in the presence of 35 μg ml −1 AlPcS 2 (86% reduction). High bactericidal activity is also observed when E. coli is exposed to red laser light (energy dose, 4.5 J; energy density, 30.0 mW cm −2) in the presence of 27.5 μg ml −1 AlPcS 2 (72% reduction). No significant reductions in viability are obtained when bacterial suspensions are exposed to the same light doses in the absence of sensitiser.