Antibacterial photodynamic activity of photosensitizer-embedded alginate-pectin-carboxymethyl cellulose composite biopolymer films.

Antimicrobial photodynamic therapy (APDT) is a promising approach for treatment of wounds infected with antibiotic-resistant bacteria. In this approach, delivery of appropriate concentration of photosensitizer (PS) at the infected site is a critical step; it is therefore essential that PS need to be administered at the infected site in a suitable formulation. Here, we report preparation of PS-embedded composite biopolymer films and their photobactericidal properties against methicillin-resistant Staphylococcus aureus (MRSA) and biocompatibility. Sodium alginate (SA), pectin (PC), and carboxymethyl cellulose (CMC) were used for preparing films containing chlorin p6 (Cp6, anionic PS) or methylene blue (MB, cationic PS). Films containing 1% CMC (15 mm diameter; 110 ± 09 μm thickness) showed ~ 55% light transmission in 500 to 750 nm region and high swelling rate as indicated by ~ 38% increase in diameter within 1 h. Absorption spectroscopic studies of PS-embedded films revealed that while Cp6 existed mainly in monomeric state, MB existed in both dimeric and monomeric forms. MRSA incubated with the film for 1 h displayed substantial uptake of Cp6 and MB as indicated by the presence of Cp6 fluorescence and MB staining in cells under the microscope. Furthermore, photodynamic treatment (660 nm, 10 J/cm2) of MRSA with Cp6 embedded in film or free Cp6 resulted in ~ 3 log reduction in colony-forming units (cfu), whereas decrease in cfu was less (~ 1 log) for MB-embedded film than for free MB (~ 6 logs). Studies on human keratinocyte (HaCaT) cells showed that there was no significant change in the viability of cells when they were incubated with solubilized films (plain) for 24 h or subjected to treatment with PS-containing films followed by PDT. These results suggest that films are biocompatible and have potential application in photodynamic treatment of MRSA-infected wounds.