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.
