Photosensitizer conjugate-functionalized poly(hexamethylene guanidine) for potentiated broad-spectrum bacterial inhibition and enhanced biocompatibility

Pathogen infection is the main cause of human morbidity and death. Traditional antibiotics usually sterilize bacteria in chemical ways, which tends to develop serious antibiotic resistance. Cationic polymers exhibit good bacterial inhibition with less resistance, but often face severe cytotoxicity toward normal cells. The optimization of polymeric antimicrobials for enhanced bactericidal capacity and improved biocompatibility is quite meaningful. In addition, photodynamic therapy (PDT) is a therapeutic modality with less susceptibility to develop resistance. Herein, a typical commercial polymeric antimicrobial, polyhexamethylene guanidine (PHMG) was selected for current proof-of-concept optimization due to its excellent bactericidal capacity but moderate biocompatibility. Eosin-Y (EoS) was copolymerized to afford EoS-labeled polymer conjugates, poly(2-(dimethylamino) ethyl methacrylate-co-eosin), P(DMAEMA-co-EoS), which was conjugated with PHMG to afford a novel polymeric antimicrobial, P(DMAEMA-co-EoS)-b-PHMG-b-P(DMAEMA-co-EoS), noted as PEoS-PHMG. It could efficiently kill broad-spectrum bacteria by physical damage and photodynamic therapy. Compared with PHMG, the bacterial inhibition of PEoS-PHMG was potentiated after the functionalization. Furthermore, PEoS-PHMG exhibited low cytotoxicity and minimal hemolysis, which was demonstrated by cell viability assays toward LO2 cells and RAW 264.7 cells as well as hemolytic assays against red blood cells. These results confirmed that the resultant PEoS-PHMG could act as promising alternative antibacterial materials with excellent broad-spectrum bacterial inhibition and favorable biocompatibility.