Design and Evaluation of Passive Disinfection Air Filters Coated with Metal-Based Nanoparticles to Combat...

Nosocomial infections continue to be a serious problem in hospital settings, particularly in intensive care units (ICUs), where resistant germs can spread through the air. Air filters are often designed to capture particulate matter but not necessarily to kill live germs that remain on their surfaces.

To address these issues, polypropylene filter media were imbued with silver (AgNPs), zinc oxide (ZnO), and copper oxide (CuO) nanoparticles to impart antibacterial activity. Chemical reduction was used to create AgNPs, while sol-gel and precipitation methods were used to prepare ZnO and CuO nanoparticles.

DLS and zeta potential measurements were utilized to calculate particle size distribution, polydispersity index, and surface charge. The filters were coated with nanoparticle suspensions by an alcohol-based dip-coating process, followed by heat treatment to solidify the deposited layers. Antibacterial activity was measured against Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) using agar diffusion and direct-contact assays, and reusability was assessed over three cycles. Different variations were observed among the tested materials. Silver nanoparticles demonstrated the largest inhibition zones (18.2 mm for S. aureus and 16.7 mm for P. aeruginosa), followed by copper oxide nanoparticles, which showed moderate inhibition. Under identical conditions, zinc oxide exhibited the lowest inhibition. Over three reuse cycles, AgNP-coated filters retained the majority of the antibacterial activity with minimal decreases in inhibitory zone diameters. ZnO and CuO coatings, on the other hand, showed significantly higher decreases after many cleanings. Treatment of filters with nanoparticles significantly increased antibacterial efficacy compared to untreated controls (p < 0.05).

In general, the addition of metal nanoparticles to polypropylene filter media appears to improve efficacy in lowering viable airborne bacterial loads. Silver-based coatings exhibited the highest resistance and effective antibacterial response among the studied materials, indicating their potential applicability in ventilation systems for the control of airborne infection within the limitations of the present three-cycle experimental framework.