ICMCTF 2024 Session MD1-1-WeA: Surface Coatings and Surface Modifications in Biological Environments I

This study investigates how different compositions of Ag-Cu alloy thin film coatings can improve the limitations of pure metals to achieve a steady and long-term antibacterial efficacy. The Ag-Cu (Ag₇₅Cu₂₅-Ag₅₀Cu₅₀-Ag₂₅Cu₇₅) alloys were deposited on PET textiles using magnetron sputtering technique. The growth process and microstructures of the thin films were characterised by XRD and TEM/EDS. Additionally, the galvanic relationship and antibacterial synergy between the Ag and Cu components in different alloys were investigated through the ion release studies and antibacterial tests. Finally, the effects of a more electrochemically active metal on the properties of Ag-Cu alloys were studied by co-sputtering Mg into Ag-Cu thin films.

The results showed that both Ag₇₅Cu₂₅ and Ag₅₀Cu₅₀ coatings improved the plateauing of Ag ion release and provided a steady Cu ion release. Antibacterial efficacy of Ag-Cu thin films followed the order: Ag₅₀Cu₅₀ > Ag₂₅Cu₇₅ > Ag₇₅Cu₂₅ > Ag ≈ Cu. Due to the sufficient release of both Ag and Cu ions in the Ag₅₀Cu₅₀ coating, this sample demonstrated superior antibacterial performance compared to both other alloys and pure metal coatings. Moreover, this coating maintained a >90% bacterial reduction rate after two antibacterial test cycles, outperforming the other coatings. The ion release studies of Ag-Cu-Mg ternary alloys showed a further reduction in both Cu and Ag ion release, with the effect of less noble Mg on the Cu ion release being more significant compared to that on the Ag ion release. Overall, our results suggest that Ag-Cu and Ag-Cu-Mg thin films are promising candidates for hospital textiles that require a steady and prolonged antibacterial activity.

Bio-interface sensing has attracted a lot of attention in recent years. For example, hydrogen peroxide (H₂O₂) and pH variation are essential detection targets in various fields, including clinical control and environmental protection. This present work reports a design of a non-enzymatic H₂O₂ electrochemical sensor and an electrochromic pH sensor with IrOx nanofibrous film. Additionally, the electrochemical performance of the IrOx nanofibrous film can be manipulated by the annealing parameters. The resultant materials are characterized through field emission scanning electron microscopy, X-ray diffraction analysis, and X-ray absorption spectroscopy. Furthermore, the electrochemical sensing performance of the IrOx nanofibrous film is evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometric (i-t) techniques. The sensitivity of the IrOx nanofibrous film is checked to investigate the effect of annealing parameters on the H₂O₂ sensing. The performance of the nanofibers in the electro-reduction of H₂O₂ is programmable by controlling the metallic Ir contents. The IrOx nanofibrous film annealed at 550°C with a ramping rate of 2.5 ^oC exhibits better electrocatalytic activity towards the electro-reduction of H₂O₂. Further, the broad linear range (0.1 to 1000 µM), low detection limit (LOD) of 0.16 µM with an excellent sensitivity is successfully achieved. The IrOx nanofibrous film can electrochromically detect the pH variation with a super-Nernst sensitivity of 80 mV/pH. Additionally, the IrOx nanofibrous film has appreciable selectivity in the presence of potentially interfering biological molecules, and its practical applicability is demonstrated in MCF-7 human breast cancer cells.