Antimicrobial Surfaces Using Covalently Bound Polyallylamine

We investigated the antimicrobial properties of the cationic polymer polyallylamine (PA) when covalently bonded to glass. The objective was to obtain a robust attachment, yet still allow extension of the polymer chain into solution to enable interaction with the bacteria. The PA film displayed strong antimicrobial activity against Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa, which includes both Gram-positive and Gram-negative bacteria. Glass surfaces were prepared by a straightforward two-step procedure of first functionalizing with epoxide groups using 3-glycidoxypropyltrimethoxy silane (GOPTS) and then exposing to PA so that the PA could bind via reaction of a fraction of its amine groups. The surfaces were characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy to verify the presence of the polymer on the surface, zeta potential measurements to estimate the surface charge of the films, and atomic force microscopy to determine the extension of the polymer chains into solution. Antimicrobial properties of these coatings were evaluated by spraying aqueous suspensions of bacteria on the functionalized glass slides, incubating them under agar, and counting the number of surviving cell colonies.