Photocatalytic graphitic carbon nitride-chitosan composites for pathogenic biofilm control under visible light irradiation.

Photocatalysis holds promise for inactivating environmental pathogens. Visible-light-responsive composites of carbon-doped graphitic carbon nitride and chitosan with high reactivity and processability were fabricated, and they can control pathogenic biofilms for environmental, food, biomedical, and building applications. The broad-spectrum biofilm inhibition and eradication of the photocatalytic composites against Staphylococcus epidermidis, Pseudomonas aeruginosa PAO1, and Escherichia coli O157: H7 under visible light irradiation were demonstrated. Extracellular polymeric substances in Escherichia coli O157: H7 biofilms were most resistant to photocatalytic oxidation, which led to reduced performance for biofilm removal. O produced by the composites was believed to dominate biofilm inactivation. Moreover, the composites exhibited excellent performance for inhibiting biofilm development in urine, highlighting the promise for inactivating environmental biofilms developed from multiple bacterial species. Our study provides fundamental insights into the development of new photocatalytic composites, and elucidates the mechanism of how the photocatalyst reacts with a microbiological system.