Issue 44, 2018

Self-immolative polymers with potent and selective antibacterial activity by hydrophilic side chain grafting

Abstract

We report the first example of a self-immolative polymer that exerts potent antibacterial activity combined with relatively low hemolytic toxicity. In particular, self-immolative poly(benzyl ether)s bearing pendant cationic ammonium groups and grafted poly(ethylene glycol) chains in their side chains were prepared via post-polymerization thiol–ene chemistry. These functional polymers undergo sensitive and specific triggered depolymerization into small molecules upon exposure to a designed stimulus (in this example, fluoride ions cleave a silyl ether end cap). The molar composition of the resulting statistical copolymers varied from 0 to 100% PEG side chains. The average molar mass of the pendant PEG chains was either 800 or 2000 g mol−1. The antibacterial and hemolytic activities were evaluated as a function of copolymer composition. Strong bactericidal activity (low μg mL−1 MBC) was retained in the copolymers containing 25–50% PEG-800, whereas hemolytic toxicity monotonically decreased (up to HC50 >1000 μg mL−1) with increasing PEG content. PEG-2000 was far less effective; both the MBC and HC50 decreased to a comparable extent with increasing PEGylation. Overall, the best cell type selectivity index (HC50/MBC ∼ 28) was obtained for the copolymer containing ∼50% cysteamine and ∼50% PEG-800 side chains, as compared to the cationic homopolymer (HC50/MBC < 1). Thus, the systematic tuning of the PEG graft density and chain length effectively enhances the cell-type selectivity of these self-immolative polymers by orders of magnitude.

Graphical abstract: Self-immolative polymers with potent and selective antibacterial activity by hydrophilic side chain grafting

Supplementary files

Article information

Article type
Paper
Submitted
20 Jūn. 2018
Accepted
12 Jūl. 2018
First published
12 Jūl. 2018

J. Mater. Chem. B, 2018,6, 7217-7229

Author version available

Self-immolative polymers with potent and selective antibacterial activity by hydrophilic side chain grafting

C. Ergene and E. F. Palermo, J. Mater. Chem. B, 2018, 6, 7217 DOI: 10.1039/C8TB01632A

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