Enzymatic poly(gallic acid)-grafted α-l-lysine inhibits Staphylococcus aureus and Escherichia coli strains with no cytotoxicity for human cells.

Abstract

The α-l-Lysine (LL) grafting onto the enzymatic poly(gallic acid) (PGAL) produces a helicoidal brush-like antimicrobial polymer containing outer positive-charged moieties. Best results are found with ca. 16mol% α-LL-grafting for the inhibition of gram-positive Staphylococcus aureus and gram-negative Escherichia coli strains. Membrane permeability, confocal and scanning electron microscopy studies suggest a pore-formation and translocation mechanisms by initial electrostatic interaction of positive charged polymer at the negatively charged bacterial membranes. The attained polymer displays high concentration of hemolysis (Hc) in erythrocytes, and no lymphocyte mitochondrial activity. Interestingly, PGAL-LL is not cytotoxic on human dermal fibroblast. The antioxidant activity after the LL hybridization is also demonstrated by DPPH, ORAC, FRAP and hydroxyl radical scavenging, which enhances the preservation of human cells in addition to antimicrobial for this polymer.