Antibacterial and physical properties of a novel sonochemical-assisted Zn-CuO contact lens nanocoating

Purpose: This work examined the antibacterial and physical effects of a novel Zn-CuO nanocoating applied on a silicone hydrogel contact lens. Methods: Zn-CuO coating of PureVision balafilcon-A soft contact lenses (Bausch&Lomb, Rochester, NY) was performed by sonochemical deposition using a high-intensity ultrasonic horn. Non-coated PureVision lenses served as a control in all experiments. Adhesion assays for P. aerueginosa and S. epidermidis to the coated lenses were performed to identify the minimal coating concentration which still possessed antibacterial activity. Lens water content, oxygen transfer light transfer, leaching, and electron microscopy studies were performed using this concentration. Results: Coated lenses showed 3–5 log reductions in adhesion of both species. The lowest tested coating concentration of 0.02 wt% led to a log reduction of 3.25 ± 1.25 of P. aeruginosa CFU/lens (P = 0.007) and a log reduction of 4.37 ± 0.75 of S. epidermidis (p = 0.0007). Using this coating concentration, water content (36%, 33.6%), oxygen transfer (87.22 ± 10.96, 92.18 ± 2.38, × 10 ⁻¹¹ (cm ² /s)(mlO ₂ )/(ml × mmHg)), p = 0.12), and light transfer properties did not differ significantly between the coated and the control contact lenses. In the range of 380–780 nm wavelength, the coated lenses transmitted 96.47 ± 1.52% while the control lenses transmitted 97.36 ± 1.35%. The corresponding values for the range of 300–380 nm wavelength were 79.343 ± 8.754 and 80.169 ± 1.35. Leaching studies for 0.5 mM coated lenses have demonstrated the excellent stability of the coating with the release of only 0.005% of the coating after 1 week of exposure to the test solution. Conclusion: Sonochemical-assisted nanocoating of contact lenses showed significant and consistent antibacterial activity while preserving the basic properties of a silicone hydrogel contact lens.