Shape matters: Effect of amphiphilic polymer topology on antibacterial activity and hemocompatibility

Understanding the intricate relationship between polymer architecture and biological activity is critical for advancing the development of antibacterial polymers. In this study, we systematically investigated the antibacterial properties and hemocompatibility of 27 different synthetic polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The antibacterial activities of these polymers were probed against two gram-negative bacteria, namely Pseudomonas aeruginosa PAO1 and Escherichia coli K12. Furthermore, the antibacterial efficacy and hemocompatibility of synthetic polymers were correlated with their polymer topology, encompassing linear (LPs), hyperbranched (HPs), and star polymers (SPs), characterized by varying hydrophobic compositions (20 %, 25 %, and 30 %). HPs were prepared using two types of crosslinking monomer (acrylate vs. acrylamide). The crosslinker:RAFT agent ratio in the synthesis of HPs greatly affect their hemocompatibility, while the type of crosslinker had a negligible impact. HPs showed a remarkable 2- to 4-fold enhancement in hemocompatibility compared to LPs at the same hydrophobic ratio. Interestingly, SPs with a low hydrophobic ratio, did not display toxicity towards red blood cells, while maintaining similar potent antibacterial activities as LPs and HPs. Overall, SPs exhibited superior bioactivity compared to HPs and LPs (SPs > HPs > LPs), demonstrating that the manipulation of polymer topology offers a promising avenue for enhancing the performance of synthetic antibacterial polymers.