(351h) Engineering the Molecular Architectures of Antimicrobial Peptide-Polymer Conjugates

While antimicrobial peptides (AMPs) are promising treatments for infectious diseases caused by multi-drug resistant bacteria, they are limited by toxicity to mammalian cells and instability in biological environments. Linear AMP-polymer conjugates having a single AMP attached to a linear hydrophilic polymer overcome the above challenges but markedly reduce antimicrobial activity. Hypothesizing that multivalent AMP-polymer conjugates will circumvent this tradeoff by improving antimicrobial activity relative to linear analogues, we prepared conjugates of stapled P9, a CXCL10-derived AMP, with neutral hydrophilic polyethylene glycol (PEG) in linear, star-shaped, and comb-like architectures. We synthesized linear and star-shaped conjugates with varying arm numbers and lengths via a thiol-maleimide mediated conjugation reaction. Increasing arm number or decreasing arm length increased antimicrobial activity and zeta potential, consistent with the higher local concentration of peptides expected upon increasing arm number or decreasing arm length. Conjugation to polymers also hindered enzymatic degradation of peptides. Moreover, even the conjugates with the highest local peptide concentrations did not introduce appreciable hemolysis. Comb-like conjugates were prepared by photo-initiated reversible addition−fragmentation chain-transfer (RAFT) polymerization of polyethylene glycol methacrylate (PEGMA) and methacrylamide-functionalized stapled P9. By slowing the addition of the faster polymerizing PEGMA, we incorporated the 22-amino acid peptide monomer into the comb polymer chain. With the polymerization method now established, we are now varying polymer backbone length and peptide density to understand the effects of molecular architecture on conjugate properties and antimicrobial function. Taken together, these studies inform the design and accelerate the clinical implementation of AMP-polymer conjugates. Beyond antimicrobial applications, we envision that these synthetic strategies and findings will contribute to the development of peptide-polymer conjugate design for a variety of drug delivery pursuits.