Effect of light and oxygen on repetitive bacterial inactivation on uniform, adhesive, robust and stable Cu-polyester surfaces

This study reports new findings on the sputtered Cu-polyester (Cu-PES) bacterial inactivation under low intensity visible light (lambda > 400 nm). Cu-PES samples sputtered for 160 s led to the complete inactivation of E. coli in anaerobic and aerobic media within 45 min. The (Cu-PES) oxidative radicals generated in aerobic media were not the only intermediates leading to bacterial inactivation. Bacterial inactivation also proceeds in the dark under anaerobic conditions. For this reason, the oxidative radicals were leading to bacterial reduction were unambiguously identified by appropriate scavengers. X-ray photoelectron spectroscopy (XPS) provided evidence for redox catalysis going within the time required by Cu-PES to induce bacterial reduction. Furthermore, the Cu-ions in the ppb range leached from the Cu-PES during bacterial reduction were monitored by inductively coupled plasma mass spectrometry (ICP-MS) and the Cu found were below the limit allowed for mammalian cells. By infrared spectroscopy (ATR-FTIR) the bacteria stretching shifts of the predominant lipopolysaccharide (LPS) associated-(CH2) groups were monitored. The overstretching of these groups determined the time necessary for bond scission/ bacterial inactivation.