Development of Functional Nanomaterials for Controlling Environmental Pathogens
Open AccessEnvironmental pathogens, residing in the external environment during most of their lifetime, cause diseases with measurable frequency after being introduced into human body. Notorious examples include airborne SARS-CoV-2, the pathogen responsible for the current global COVID-19 pandemic. The ability to survive and thrive in diverse niches makes environmental pathogens outside human hosts to be less effectively inactivated by conventional environmental disinfection methods, such as chlorine, ultraviolet (UV) light, and ozone. Moreover, due to the wide spread antibiotic resistance and formation of biofilms, conventional clinical antimicrobial treatments have limited performance against environmental pathogens propagated in the human host. Compared with conventional treatments, functional nanomaterials with desirable characteristics, e.g., high specific surface area and enhanced photo- or thermal reactivity, are promising candidates for controlling environmental pathogens. This dissertation focuses on the application of functional nanomaterials, i.e., graphitic carbon nitride (g-C3N4) and electrospun nanofibrous membranes, for stopping the spread of environmental pathogens. In the first part of this dissertation, the anti-biofilm efficacy of g-C3N4 under visible light irradiation was investigated. The visible light responsive photocatalyst could not only inhibit biofilm development but also eradicate established biofilms from surfaces. Moreover, it was demonstrated that the potent photocatalysis removed the extracellular polymeric substances within biofilms and thus destroyed the integrated and cohesive structure of biofilms. In the second part, to overcome the poor processability of g-C3N4 powder, a composite biomaterial was developed by incorporating g-C3N4 into a polymeric matrix of chitosan. Under visible light irradiation, the composite with enhanced processability showed high efficacy for inhibiting and removing a broad spectrum of biofilms. In the third part, electrospinning was employed to fabricate non-woven mats with ultrafine nanofibers (~ 300 nm). Compared with face masks available on the market, the product membranes exhibited a great filtration efficiency for removing coronavirus aerosols (generated from murine hepatitis virus A59 (MHV-A59)) with a desirable pressure drop amid filtrations. In addition, NaCl aerosols were verified as a conservative surrogate for real coronavirus aerosols in the filtration tests. In the last part, photosensitized electrospun nanofibrous membranes were synthesized by incorporating photoreactive dyes into the electrospun matrix. In the aerosol filtration tests, the optimized membranes caught 99.2% of NHV-A59 aerosols. Furthermore, the photosensitized membranes rapidly inactivated 98.9% of MHV-A59 in virus-laden droplets only after 15 min irradiation of visible light. The influence of photo-oxidative stress on the viral lifecycle, i.e., binding, internalization, and infectivity, was also thoroughly investigated. The research provides insights into developing advanced nanomaterials and explores the interactions between nanomaterials and environmental pathogens. This dissertation has demonstrated that functional nanomaterials could find broad applications for controlling environmental pathogens. The results will have a lasting impact on public health and material science.
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