LAUSR

Abstract A biodegradable polymer–titanium dioxide (TiO 2 ) nanocomposite with antimicrobial activity by photooxidation of the composited TiO 2 under fluorescent light irradiation was investigated. Polyamide 4 (PA4)–visible-light-sensitive TiO 2 nanocomposite films were prepared. The nanocomposite films exhibited antibacterial activity slightly in the dark, whereas antibacterial activity against Escherichia coli was enhanced according to the increase of TiO 2 concentration under fluorescent light irradiation for 1 h at 4000 lx. As the increase of the illumination intensity and irradiation time, nanocomposite films exhibited high antibacterial activity. The cell count on nanocomposite films with 1 wt% TiO 2 decreased three orders of magnitude comparing to that of films without TiO 2 under irradiation for 6 h at 3000 lx. Staphylococcus aureus was resistant to PA4-TiO 2 nanocomposites in contrast to E. coli . In contrast, a PA4-degrading bacteria (ND-11) was sensitive to PA4-TiO 2 nanocomposites comparing E. coli . In addition, the PA4-degrading bacteria was sensitive to the copper containing in TiO 2 . Therefore, the biodegradability was reduced according to the increase the TiO 2 (copper) concentration in PA4-TiO 2 nanocomposites in the dark. It was suggested that the effects of TiO 2 against microbial differ from every biodegradable polymer. In this study, we were able to impart a biodegradation control function, in which biodegradation is suppressed by fluorescent light irradiation and progressed in the dark, to PA4 by compositing visible-light-sensitive TiO 2 .