Contact-killing antibacterial
materials are attracting
attention
owing to their ability for sustained antibacterial activity. However,
contact-killing antibacterial polystyrene (PS) has not been extensively
studied because its chemically stable structure impedes chemical modification.
In this study, we developed an antibacterial PS sheet with a contact-killing
surface using PS synthesized from 2,2′-azobis-[2-(1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium-2-yl)]propane triflate (ADIP) as a radical
initiator with cationic moieties. The PS sheet synthesized with ADIP
(ADIP-PS) exhibited antibacterial activity in contrast to PS synthesized
with other azo radical initiators. Surface ζ-potential measurements
revealed that only ADIP-PS had a cationic surface, which contributed
to its contact-killing antibacterial activity. The ADIP-PS sheets
also exhibited antibacterial activity after washing. In contrast,
PS sheets containing silver, a typical leachable antibacterial agent,
lost all antibacterial activity after the same washing treatment.
The antibacterial ADIP-PS sheet demonstrated strong broad-spectrum
activity against both Gram-positive and Gram-negative bacteria, including
drug-resistant bacteria. Cytotoxicity tests using L929 cells showed
that the ADIP-PS sheets were noncytotoxic. This contact-killing antibacterial
PS synthesized with ADIP thus demonstrated good prospects as an easily
producible antimicrobial material.