A photodynamic antibacterial spray-coating based on the host-guest immobilization of the photosensitizer methylene blue.

In the "post-antibiotic era", healthcare-associated infection has become a global problem that threatens public health and causes huge economic losses. The development of antibacterial coatings based on non-antibiotic strategies is particularly important as drug-resistant bacteria continue to evolve. Photodynamic coatings are a high potential method to treat bacteria, however, the aggregation of photosensitizers on the coating affects the photodynamic capacity seriously. Herein, a photodynamic coating is developed based on the host-guest interaction between β-cyclodextrin and the photosensitizer methylene blue (MB). The host-guest interaction avoids aggregation of MB and results in a high singlet oxygen quantum yield. Consequently, efficient photoantibacterial activity towards methicillin-resistant Staphylococcus aureus is achieved by the photodynamic coating with very low MB density (0.53 ± 0.06 μg cm-2).