Designing surfaces that kill bacteria on contact

Abstract

Poly(4-vinyl-N-alkylpyridinium bromide) was covalently attached to glass slides to create a surface that kills airborne bacteria on contact. The antibacterial properties were assessed by spraying aqueous suspensions of bacterial cells on the surface, followed by air drying and counting the number of cells remaining viable (i.e., capable of growing colonies). Amino glass slides were acylated with acryloyl chloride, copolymerized with 4-vinylpyridine, and N-alkylated with different alkyl bromides (from propyl to hexadecyl). The resultant surfaces, depending on the alkyl group, were able to kill up to 94 +/- 4% of Staphylococcus aureus cells sprayed on them. A surface alternatively created by attaching poly(4-vinylpyridine) to a glass slide and alkylating it with hexyl bromide killed 94 +/- 3% of the deposited S. aureus cells. On surfaces modified with N-hexylated poly(4-vinylpyridine), the numbers of viable cells of another Gram-positive bacterium, Staphylococcus epidermidis, as well as of the Gram-negative bacteria Pseudomonas aeruginosa and Escherichia coli, dropped more than 100-fold compared with the original amino glass. In contrast, the number of viable bacterial cells did not decline significantly after spraying on such common materials as ceramics, plastics, metals, and wood.

Figure 1

Photographs of a commercial NH₂ glass slide (Left) and a hexyl-PVP-modified slide (Right) onto which aqueous suspensions (≈10⁶ cells per ml of distilled water) of S. aureus cells were sprayed, air dried for 2 min, and incubated under 0.7% agar in a bacterial growth medium at 37°C overnight.

Figure 2

The percentage of S. aureus colonies grown on the infected surfaces of glass slides modified with PVP that was N-alkylated with different linear alkyl bromides relative to the number of colonies grown on a commercial NH₂-glass slide (used as a standard). The bacterial cells were sprayed from an aqueous suspension (10⁶ cells per ml) onto the surfaces. All experiments were performed at least in quadruplicate, and the error bars indicate the standard deviations from the mean values obtained.