Nanoscale Characteristics and Antimicrobial Properties of (SI-ATRP)-Seeded Polymer Brush Surfaces

Microbial resistant coatings have raised considerable interest in the biotechnological industry and clinical scenarios to combat the spreading of infections, in particular in implanted medical devices. Polymer brushes covalently attached to surfaces represent a useful platform to identify ideal compositions for preventing bacterial settlement by quantifying bacteria-surface interactions. In this work, a series of polymer brushes with different charges, positively charged poly[2-(methacryloyloxy)ethyl trimethylammonium chloride] (PMETAC), negatively charged poly(3-sulfopropyl methacrylate potassium salt) (PSPMA), and neutral poly(2-hydroxyethyl methacrylate) (PHEMA) were grafted onto glass surfaces by surface-initiated atom transfer radical polymerization in aqueous conditions. The antimicrobial activity of the polymer brushes against Gram-negative Escherichia coli was tested at the nano- and microscopic level on different time scales, that is, from nm to 100 microm, and ms to 24 h, respectively. The interaction between the polymer brushes and E. coli was studied by single-cell force spectroscopy (SCFS) and by quantification of the bacterial density on surfaces incubated with bacterial suspensions. E. coli firmly attached to positive PMETAC brushes with high work required for de-adhesion of 28 ± 9 nN·nm, but did not significantly bind to negatively charged PSPMA and neutral PHEMA brushes. Our studies of bacterial adhesion using polymer brushes with controllable chemistry provide essential insights into bacterial surface interactions and the origins of bacterial adhesion.