Cationic porphyrin-based star-shaped polymers with photo-enhanced antibacterial activity by BIT-RDRP

Antimicrobial resistance is still a major clinical challenge worldwide today and the development of novel antimicrobial agents with high antimicrobial activity and low bacterial resistance is of great importance. In this work, quaternized 2-(dimethylamino) ethylmethacrylates iodonium salt-type monomers with different lengths of pendent alkyl (qDMAEMA(Cx), x = 3, 6 and 8) are synthesized for preparation of a series of cationic porphyrin-based star-shaped (co)polymers by photo-controlled bromine-iodine transformation reversible-deactivation radical polymerization (BIT-RDRP). Especially, qDMAEMA(Cx) not only acts as a monomer but also can be used as an intrinsic catalyst for the BIT-RDRP. In addition, effects of alkyl chain length (x), degree of polymerization and hydrophilic-hydrophobic balance (H.L.B.) on the antibacterial activity of the prepared (co)polymers are investigated. The resulting zinc ion coordinated copolymers Zn@THPP-4P(qDMAEMA(C8)20-co-PEGMA35) (denoted as Zn@P6) exhibits good water solubility and is able to be absorbed effectively on the surfaces of bacteria, exhibiting excellent photodynamic inhibition activity against both S. aureus and E. coli under irradiation with 570 nm light source according to the coated plate experiments. The minimum bactericidal concentration (MBC) of Zn@P6 against S. aureus and E. coli are 1.5 and 2.0 μM, respectively, in the presence of light. Meanwhile, Zn@P6 shows quite low cytotoxicity and satisfying photolysis ability at working concentrations, displaying promising biological application prospects.