Poly(oxanorbornene)s bearing triphenylphosphonium and PEGylated zinc(ii) phthalocyanine with boosted photobiological activity and singlet oxygen generation

Abstract

Polymers containing suitable photosensitizers are a promising choice for light-guided management of perceived problems associated with microbial infections linked to resistant bacteria and biofilms. Ring-opening metathesis polymerization (ROMP) is an important molecular platform for the development of such materials. Herein, we present the preparation of antibacterial poly(oxanorbornene)s, which contain biocompatible poly(ethyleneglycol) (PEG) functionalized zinc(II) phthalocyanine (ZnPc) as a photosensitizer and membrane-targeting cationic triphenylphosphonium (TPP) units. Copolymers with varying compositions of ZnPc and TPP units as well as a homopolymer containing only ZnPc are synthesized. The relevant photophysical properties are measured in a complementary manner, revealing the differences between the various polymer architectures. We identify that by varying the ratio of TPP to ZnPc units, the monomeric state of the photosensitizer in water media can be precisely controlled, leading to a dramatic increase in singlet oxygen quantum yield (from 0.04 to 0.93) and high photoinduced inactivation efficacy against bacteria in the planktonic and biofilm states upon irradiation with low-intensity light (18 J cm⁻²). This study unravels a structure–property relationship for photoactive polymers, highlighting the role of PEG functionalization and the use of cationic TPP units to achieve high efficiency, offering a promising strategy for the synthesis of polymers with near-infrared light-triggered activity.