Bio-Based Copolymers with Tunable Cationic Charge Densities for Antimicrobial Applications ^†

The development of polymers derived from renewable resources is a critical research priority, motivated by the urgent need to reduce dependence on petroleum-based plastics. In this study, we present a sustainable copolymer system based on two bio-sourced monomers: MTA, a vitamin B1 derivative (sulfurol) [1], and PrI, a naturally derived modified itaconic acid [2]. Capitalizing on the chemical versatility of itaconic acid, we incorporated click chemistry-compatible functional groups to enable the covalent conjugation of natural bioactive compounds (sulfurol and menthol), imparting antimicrobial and antioxidant properties. Furthermore, the sulfurol moiety permits post-functionalization of the copolymer, introducing tunable cationic charge densities to modulate bioactivity. The copolymers were comprehensively characterized to assess their functional properties. Antimicrobial activity was evaluated against both Gram-positive and Gram-negative bacterial strains using minimum inhibitory concentration (MIC) assays [2]. The MIC values varied between 8 and 500 µg/mL, depending on the copolymer composition and the specific microorganism tested. Antioxidant performance was analyzed via DPPH radical scavenging assays [3], which demonstrated significant activity at a polymer concentration of 0.25 mg/mL. The Trolox equivalent antioxidant capacity (TEAC) was determined to be in the range of 0.4–0.6 µmol/mg, confirming the copolymers’ free radical quenching ability. Biocompatibility was assessed using Normal Human Dermal Fibroblasts (NHDFs) and the Alamar Blue viability assay. The results indicated excellent cell viability, suggesting that these copolymers are highly compatible with biological tissues and suitable for biomedical applications.