Photocatalytic antimicrobial activity of thin surface films of TiO2, CuO and TiO2/CuO dual layers on Escherichia coli and bacteriophage T4

Abstract

TiO 2 coated surfaces are increasingly studied for their ability to inactivate microorganisms.The activity of glass coated with thin films of TiO 2 , CuO and hybrid CuO/TiO 2 prepared by atmospheric Chemical Vapour Deposition (Ap-CVD) and TiO 2 prepared by a sol-gel process was investigated using the inactivation of bacteriophage T4 as a model for inactivation of viruses. The chemical oxidising activity was also determined by measuring stearic acid oxidation. The results showed that the rate of inactivation of bacteriophage T4 increased with increasing chemical oxidising activity with the maximum rate obtained on highly active sol-gel preparations. However these were delicate and easily damaged unlike the Ap-CVD coatings. Inactivation rates were highest on CuO and CuO/TiO 2 which had the lowest chemical oxidising activities. The inactivation of T4 was higher than that of Escherichia coli on low activity surfaces. The combination of photocatalysis and toxicity of copper acted synergistically to inactivate bacteriophage T4 and retained some selfcleaning activity. The presence of phosphate ions slowed inactivation but NaCl had no effect. The results show that TiO 2 /CuO coated surfaces are highly antiviral and may have applications in the food and healthcare industries.

Insight on the photocatalytic bacterial inactivation by co-sputtered TiO 2 –Cu in aerobic and anaerobic conditions

“…Photocatalysis using TiO 2 combined with Cu have shown to have a stronger performance compared to TiO 2 when eliminating toxic pollutants and when inducing bacterial due to the electron acceptor properties of the Cu-ions. Antibacterial studies reporting some the activity by TiO 2 /Cu photocatalysts have recently been reported by Hashimoto/Fujishima [1][2][3][4], suggesting that UV-light induces highly oxygenated radicals on TiO 2 damaging the outer cell wall followed by Cu-ion(s) infiltration across the cell membrane in agreement with observations reported by Li and Dennehy [5] and Ditta et al [6]. More recently the TiO 2 /Cu has been revisited to improve bacterial reduction under light and in the dark addressing the synthesis of uniform, robust adhesive films sputtered on textiles and polymers by our laboratory [7][8][9][10].…”

Indoor Light Enhanced Photocatalytic Ultra-Thin Films on Flexible Non-Heat Resistant Substrates Reducing Bacterial Infection Risks

“…This bacterial inactivation by Cu-species in the dark and/or under anaerobic conditions has been attributed to the translocation/permeation of Cu-ions across the bacterial cell wall. Bacterial reduction mediated by Cu-NPs has been recently reported in suspensions or on sputtered surfaces [37][38][39][40][41][42]. We suggest that the bacterial inactivation in the dark on Cu sputtered PES proceeds in air by CuO/Cu(OH) 2 (NPs) and the production of O 2 − radicals [34,35].…”

Titanium Oxide Antibacterial Surfaces in Biomedical Devices

“…Since the demonstration of its antimicrobial activity, UV-activated TiO 2 has been used in suspension, in liquids, or immobilized on surfaces for the destruction of Gram-negative and Gram-positive bacteria, including endospores, fungi, algae, protozoa, viruses as well as for the inactivation of microbial toxins and prions (45,72,(118)(119)(120)(121)(122)(123)(124)(125)(126)(127). Ions such as Cu 2+ and Ag + in combination with TiO 2 were reported to enhance its antimicrobial activity (72).…”