Dual Propionibacterium acnes therapy using skin penetration-enhanced liposomes loaded with a photosensitizer and an antibiotic

Various antibiotics and photosensitizers are used for Propionibacterium acnes therapy. However, the success rate of therapy is limited because of antibiotic resistance, side-effects of photodynamic therapy using photosensitizer and the low skin-penetration efficiency of antibiotics and photosensitizers. In this study, to enhance the skin penetration efficiency, maintain their photodynamic activity and induce dual antibacterial therapeutic effects, we prepare erythromycin and branched polyethyleneimin-hematoporphyrin (bPEI-HPP) conjugates were loaded into liposomes (cationic photosensitizer-erythromycin loaded liposomes, CP-L (bPEI-HPP 10 mg; CP-L 1 and 20 mg; CP-L 2)). The tissue penetration efficiency of CP-Ls was determined by the Franz cell diffusion system and fluorescence microscopy. The penetration efficiency of CP-Ls is greater than that of bPEI-HPP, unloaded cationic photosensitizer and free HPP because CP-Ls comprised phospholipids that are similar to the cell membrane lipid composition. For in vitro antibacterial effects, Propionibacterium acnes (P. acnes) were used. The loss of viability rate of P. acnes by CP-L 2 (95%) from the colony forming unit (CFU) assay, was 2.4-fold higher than erythromycin-loaded liposomes (39%) and 1.9-fold higher than bPEI-HPPloaded liposomes (50%). Therefore, we suggest that polycationic photosensitizer and antibiotic-loaded liposomes have potential applications in clinical photodynamic anti-bacterial therapy.