ANTIBIOFILM POTENTIAL OF SILVER, ZINC OXIDE AND TITANIUM DIOXIDE NANOPARTICLES AND THEIR APPLICATION IN WATER PIPELINES

Abstract

Biofilms are complex microbial structures that adhere to surfaces and are enclosed within self-produced extracellular polymeric substances (EPS), enabling them to resist disinfectants and antibiotics. Biofilm formation in water plumbing systems presents a serious risk to water hygiene and public health. The biofilm structures significantly reduce the efficacy of conventional disinfection methods and contribute to chronic contamination of water distribution and drainage lines. This study investigates the synthesis and evaluation of silver (Ag), zinc oxide (ZnO), and titanium dioxide (TiO₂) nanoparticles (NPs) with respect to their antibiofilm properties and potential applications in water pipeline systems. Biofilm-producing bacteria isolated from both water and scraping samples collected from kitchen and washroom pipelines were used to evaluate the antibiofilm efficacy of the nanoparticles. Ag, ZnO, and TiO₂ nanoparticles were synthesized by chemical reduction, microwave-assisted and sol-gel/hydrothermal methods respectively. The antibiofilm efficacy of the nanoparticles was assessed individually and in combination using the Tissue Culture Plate (TCP) method. To assess practical applicability, PVC pipe segments were coated with combination of ZnO–TiO₂ nanoparticles and compared with painted and uncoated controls. Biofilm formation was monitored over a three-month period using optical density (OD) measurements. The percentage of biofilm inhibition was calculated by the differences of the OD values of untreated and treated bacteria. All nanoparticles showed concentration-dependent inhibition. Especially, ZnO–TiO₂ combination showed the highest level of inhibition across different biofilm bacteria, suggesting a synergistic effect. During the first month, the nanocoated pipes showed biofilm formation (OD ≈ 0.57) that was almost similar to the uncoated controls (OD ≈ 0.58). However, a notable decrease in OD values (to approximately 0.51–0.53) was observed during the second and third months, indicating the effectiveness of the nanoparticles in inhibiting biofilm formation. These values were comparable to those of painted pipes and significantly lower than those of the uncoated controls (~0.58–0.68). Overall, the findings confirm that ZnO–TiO₂ nanocoatings effectively reduce biofilm accumulation over time and could serve as a promising alternative to chemical paints.