Abstract:
The world is under the threat of the COVID-19 pandemic caused by the SARS-CoV-2 virus since December 2019. In addition to the transmission through respiratory droplets and close contact, it can also spread through indirect contact with contaminated surfaces. Incorrect disposal of used masks, gloves, goggles, gowns, face shields and other items creates a surge in plastic waste, spreading pathogens and serious environmental hazards. Being a developing country, Bangladesh could hardly provide basic personal protective equipment (PPE) for all frontline health workers. Photocatalytic nanoparticles usually show stronger disinfection behavior by producing reactive oxidative species (ROS). In the present study, an inexpensive photocatalytic method is developed using novel BN and TiO2 that can further be used to sterilize PPE before reuse. A prototype decontamination chamber was constructed for photocatalysis using UVC light. E. coli was chosen as a model gram-negative bacterium to investigate the antimicrobial performance and the photocatalysts demonstrated negligible toxicity effects on the bacteria. The optimum intensity, irradiation time and distance from the lights were determined by comparing intensity values in the range of 6.92-116.16 W/m2. When the antibacterial activity was tested in the solid medium for 2h with 116.16 W/m2 intensity, the minimum inhibitory concentration (MIC) was found to be 90 mg/mL for TiO2 and more than 100 mg/mL for bulk BN. To evaluate the antibacterial activity of nanoparticles in liquid media, 29.04 W/m2 light intensity was applied for 60 minutes. The samples were kept 17 cm away from the lights during the experiments. Three different concentrations of photocatalysts (0.1, 0.25 and 0.5 mg/mL) were selected to test for inactivating mixed and pure culture. Exfoliated BN was produced using a probe sonicator to increase the antibacterial effectivity of BN. It was observed that 0.25 mg/mL TiO2 decreased 76% of mixed bacterial colonies whereas 0.1 mg/mL exfoliated BN could effectively reduce 99.84% of the initial bacterial density of the pure culture. TiO2 and exfoliated BN were also mixed in the ratio of 1:1 and 2:1 without any physical or chemical modification that gave similar bactericidal activity against E. coli as exfoliated BN alone. Therefore, exfoliated hexagonal BN exhibited the best disinfection performance for pure culture. It can be anticipated that the simply constructed UV chamber along with the novel hexagonal BN solution might provide an easy and feasible method for surface disinfection of PPE.
