Precise Engineering Poly(Glucose Acrylate)- b -Poly(Guanidine Thioctic Acid) Diblock Copolymers for Selective Killing of Drug-Resistant Gram-negative Bacteria

Abstract

Drug-resistant Gram-negative bacteria remain difficult to eradicate owing to their complex and lipopolysaccharide-rich outer membranes. Guanidinium-containing polymers offer a promising membrane-active strategy, combining potent bactericidal activity, preferential interactions with anionic Gram-negative membranes and a low propensity to induce resistance. However, their therapeutic translation is hampered by nonspecific cytotoxicity and limited aqueous solubility. The incorporation of glycosyl pendants may mitigate this through their biocompatibility. However, the inherent polydispersity of natural polysaccharides poses challenges to investigating how glycosyl pendants modulate copolymer performance and how the block ratio can be precisely tuned. Herein, we report a controllable strategy to construct poly(glucose acrylate)-b-poly(guanidine thioctic acid) diblock copolymers termed p(Glum-b-GTAn), by combining reversible addition-fragmentation chain-transfer (RAFT) polymerization with thiol-initiated disulfide exchange polymerization. Precise tuning of the glycosyl-to-guanidinium block ratio (m = 20, n = 10) enabled a systematic balance of antibacterial potency, hemocompatibility, and cytocompatibility. Meanwhile, p(Glu20-b-GTA10) exhibited selective killing of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-E. coli) over methicillin-resistant Staphylococcus aureus (MRSA), negligible resistance development during serial passaging, and effective in vivo antibacterial efficacy in an ESBL-E. coli-induced murine peritonitis model. This work establishes precise engineering of p(Glum-b-GTAn) as a promising strategy for structural optimization of guanidinium-containing diblock copolymers with reduced toxicity and retained antibacterial activity, effectively addressing Gram-negative infections.