Investigation of the Antibacterial Effects, Skin Sensitivity, and Irritant Properties of a Lubricating Gel Containing Silver/Zinc Oxide Nanostructure and Lidocaine in an Animal Model

Background: Urinary tract infections (UTIs), predominantly catheter-associated (CAUTIs), cause significant morbidity (~380,000 cases), mortality (~9,000-13,000 deaths), and healthcare costs annually. CAUTIs initiate via bacterial biofilm formation on catheters. Current antimicrobial catheters (e.g., silver ions, antibiotics) face limitations like poor efficacy, resistance, and non-adjustability. Nanostructure coatings offer promise; notably, combining Ag/ZnO nanostructures leverages enhanced biocompatibility and potent antibacterial effects for novel CAUTI prevention strategies. Methods: AgNPs were chemically synthesized via silver nitrate reduction (sodium citrate/sodium borohydride); ZnO-NPs were prepared from zinc acetate/sodium hydroxide. A lubricant gel containing 2% lidocaine and Ag/ZnO nanostructures (2:8 v/v ratio) was formulated. Nanostructure characterization included DLS, TEM, and ICP-OES. Antibacterial efficacy was assessed via disk diffusion and microdilution (MIC/MBC) against S. aureus and P. aeruginosa. Biocompatibility was evaluated via rabbit ocular irritability and Guinea Pig Maximization Test (ISO 10993-10). Results: DLS/TEM characterization showed AgNPs (24.4 nm, spherical) and ZnO-NPs (52.48 nm, clustered) were mono-disperse (PDI ~1 and 0.667). Zeta potential confirmed stability (Ag: -20.7 mV; ZnO: -0.709 mV). ICP-OES quantified concentrations (Ag: 25 ppm; ZnO: 970 ppm). Antibacterial assays revealed weak AgNP activity (MIC/MBC >12.5 μg/mL for both pathogens) but potent ZnO-NP effects (e.g., S. aureus MIC: 0.406 μg/mL). Ag/ZnO hybrids exhibited enhanced efficacy, especially against S. aureus (MIC: 0.02/3.12 μg/mL). The gel was non-irritating (rabbit ocular test) and non-sensitizing (Guinea Pig Maximization Test). Conclusion: The active formulation consisting of mixed silver and zinc oxide nanostructures combined with a medical lubricant containing 4% lidocaine demonstrates effective antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus, while exhibiting no irritant or sensitizing properties in laboratory animals.