Biomimetic helical fiber cellulose acetate/thermoplastic polyurethanes photodynamic antibacterial membrane: Synthesis, characterization, and antibacterial application

This study designed a novel co-electrospun cellulose acetate (CA)/thermoplastic polyurethane (TPU) photodynamic helical fiber antibacterial membrane as a potential environmentally friendly medical protective material. A central combined design method (CCD) based on response surface methodology (RSM) was used to analyze essential variables' influence. The optimized parameters for CCD were TPU (wt%) 11.68 %, CA (wt%) 13.89 %, DMAc/ACE volume ratio 0.147, LiCl (wt%) 1.39 %, and voltage (kV) 14.43 V. Pitch and pitch diameter were the response process as the critical output variable. The membranes were characterized by SEM, TG, FT-IR, and molecular structure analysis. The results showed that the photodynamic helical fiber antimicrobial membrane exhibited synergistic effects of the antibacterial photodynamic therapy (APDT) and antimicrobial agent under average daylight irradiation. The release rate of -OH was 98.22 %, and H2O2 was 88.36 % under the action of 20 min of light. The bactericidal rates of S. aureus and E. coli reached 99.9 % and 99.7 %, respectively. The fiber helical structure can increase the light absorption rate, thus increasing the release rate and amount of reactive oxygen species (ROS) species, increasing the antibacterial rate. After washing five times, the antibacterial membrane has excellent antibacterial performance and a dark antibacterial effect.

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.