Access to safe drinking water is defined as a basic human right by the World Health Organization (WHO). Waterborne pathogens, however, have raised significant health concerns and economic losses worldwide. Compared with conventional water disinfection strategies, e.g. chemical disinfectant, photocatalysis holds promise for the inactivation of waterborne pathogens because of broad spectrum effectiveness under ambient conditions, low cost, easy operation and maintenance. Herein, we develop graphitic carbon nitride (g-C3N4), an emerging visible-light-responsive photocatalyst and interrogate its anti-biofilm potential in water. g-C3N4 powder was synthesized through thermal polycondensation of melamine, cyanuric acid, and barbituric acid and g-C3N4 coupons were fabricated via hydraulic press of the powder. Staphylococcus epidermidis (S. epidermidis), a Gram-positive bacterium, was selected as a model pathogen to grow biofilms on the coupons. Biofilms were grown in the dark and under visible light irradiation to understand biofilm inhibition by photocatalysis, and mature biofilms were also explored for eradiation under visible light exposure. Optical coherent topography (OCT), confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) were used to characterize the thickness, coverage, morphology, and viability of the biofilms. Atomic force microscopy (AFM) was used to characterize the mechanical properties of the biofilms. In addition, a florescent lectin, polysaccharide intercellular adhesin (PIA), was utilized to evaluate the presence and content of extracellular polymeric substances (EPSs) of the biofilms. OCT and CLSM suggested that g-C3N4 coupons inhibited biofilm development and eradicated mature biofilms under the irradiation of white LED light. Compared to mature biofilms developed in the dark, photocatalysis reduced the EPS content based on SEM and PIA staining. In addition, biofilms after photocatalysis became stiffer, which could also be explained with the loss of EPS. H2O2 and 1O2 were identified as the main ROS that control biofilm development and eradication, not only inactivated bacterial cells but also weakened chemical bonds within the EPS matrix. Our research has demonstrated g-C3N4 could inhibit and eradicate biofilms under visible light irradiation. Next step we will investigate the antimicrobial potential of g-C3N4 against other waterborne pathogens, such as viruses and protozoans.

Visible-light-responsive photocatalyst of graphitic carbon nitride for biofilm control

2019 Spring National Meeting

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