Synthetic amphiphilic cationic polymers exhibit potent antimicrobial activity against a broad spectrum of bacteria by disrupting bacterial cell membranes, which mimic naturally occurring antimicrobial peptides. In this study, we designed a new self-assembly system, in which the antimicrobial activity of polymers can be controlled by capture and on-demand release of polymer chains (Figure 1). We prepared a nano-sized particle (~50 nm in diameter) in which polysaccharide pullulan chains modified with cholesterols (~1 per 100 glucose unit) (CHPs) are physically cross-linked by association of cholesterol groups in water. The nano-particles have swollen pullulan polymer networks, providing a nano-sized polymer gel (nanogel) structure which is capable of capturing proteins and small drugs [Chem. Rec. 2010, 10, 366]. When the CHP nanogels were incubated with amphiphilic antimicrobial methacrylate copolymers (AMPs), the nanogels captured the AMPs by the hydrophobic interaction, and ~6-7 of AMP chains were bound to one nanogel. The CHP-AMP complex did not show any significant reduction in the number of viable E. coli. However, once methyl-�-cyclodextrins (CDs) were added, the CHP nanogels were dissociated due to the capping of cholesterols by CDs and released the AMPs into solution. The released AMPs showed potent bactericidal activity against E. coli (>99% killing in 120 minutes). This result demonstrates that the antimicrobial activity of AMPs can be controlled by modulating the non-covalent interactions and binding affinities between amphiphilic polymers and nano-particles in water.

On-demand control of antimicrobial activity of methacrylate random copolymers using amphiphilic polysaccharide nanogel

248th National Meeting (2014)

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