Visible light-induced plasmid DNA damage catalyzed by a CdSe/ZnS-photosensitized nano-TiO2 film.

Visible light-induced photocatalytic degradation of environmental pollutants with improved TiO2 has attracted much attention in pollution control and management. The degradation of nucleic acids is of great significance for biological contaminants such as viruses. In the presentwork, visible light-induced plasmid DNA damage catalyzed by a CdSe/ZnS-photosensitized nano-TiO2 film (QDs-TiO2 film) was investigated by atomic force microscopy (AFM) and agarose gel electrophoresis. Illuminated by visible light, the supercoiled pUC18 DNA could be damaged into nicked-circle and linear conformations by the QDs-TiO2 film. The percentage of different conformations of damaged DNA changed with illumination time. A statistical rule for calculating the quantity of supercoiled DNA has been established to evaluate the photocatalytic activity of the QDs-TiO2 film based on AFM results. Visible light-induced plasmid DNA damage catalyzed by the QDs-TiO2 film is characteristic of zero-order kinetics and the rate constant (k) is 3.5 x 10(-11) M x s(-1). Given an illumination time, the quantity of damaged supercoiled DNA catalyzed by the QDs-TiO2 film is constant.