Nanotech Trojan Horse: Chitosan–ZnO Sustainable Coatings Against Multidrug-Resistant (MDR) Uropathogens and UreC-Positive Proteus mirabilis

Introduction: Catheter-associated urinary tract infections (CAUTIs) caused by multidrug-resistant (MDR) uropathogens pose a management challenge due to bacterial biofilm formation and crystalline encrustation, especially those associated with Proteus mirabilis, which result in persistent infections and catheter obstructions. Current catheter surface coatings against CAUTIs target either the initial stages or later phases of such pathologies separately. Aim: We report the design and characterization of a novel polyfunctional coating comprised of polydopamine (PDA), genipin-crosslinked chitosan (GCS), and ZnO nanoparticles capable of blocking bacterial attachment, biofilm formation, and mineral encrustation. Methods: PDA-coated silicon surfaces were functionalized with genipin-crosslinked GCS/ZnO nanocomposites and studied by means of TEM, XRD, FTIR, SEM, AFM, water contact angle measurements, and zinc ion release tests. Antibacterial, antibiofilm, anti-encrustation, and hemocompatibility activities were then assessed. Results: ZnO nanoparticles were spherical, with an average particle size of 34.6 ± 8.2 nm and a highly crystalline hexagonal wurtzite structure. Coatings containing ZnO nanoparticles retained hydrophilic surface properties and released Zn2+ ions steadily. The G5 coating (containing 0.2% ZnO) demonstrated an ability to decrease bacterial adherence by >4 log10 CFU, lower biofilm biomass by 80–90% (p < 0.001), prevent mineral deposition by 67–70% caused by Proteus mirabilis, and keep catheter patency for 14 days. Hemolysis was within the ISO 10993-4 acceptance criteria. Conclusions: A rationally designed combination of PDA, genipin-crosslinked GCS, and ZnO nanoparticles provided a multifunctional coating with potent antibacterial, antibiofilm, anti-encrustation, and initial hemocompatibility activity, serving as a proof-of-concept platform for further cytotoxicity assessment, mechanical durability studies, and preclinical evaluations prior to clinical implementation.