Antibacterial Properties Of Two-Dimensional Carbon Nanomaterials

Bacterial resistance to antibiotics poses a global threat to public health. It is thus imperative to develop novel antibacterial agents, especially those non-metabolic targeting ones. Graphene is a 2-dimensional carbon nanomaterial that exhibits outstanding physical properties, can be modified via diverse chemical routes, and has potentials for biomedical applications. Focusing on the antibacterial property of graphene-derived materials, this dissertation has systematically carried out the following three works.1. The origin of graphene oxide’s (GO’s) controversial antibacterial property. GO was reported to be antibacterial in saline while its antibacterial activity in medium is controversial. To unveil this controversy, we performed plate-killing assays under comparable conditions. Results showed that GO was intrinsically antibacterial in saline, while deactivated by supplementing saline with 10% LB medium and the ratio of deactivation depends on the ratio of LB and GO. Details revealed certain components in LB medium were adsorbed on the surface of GO basal plane. With BSA and tryptophan as model adsorbates, we proved that non-covalent adsorption played the critical role in GO’s inactivation. Moreover, this deactivation can be expended into GO’s cytotoxicity against mammalian cells. This work suggests the availability of GO’s basal plane determines its antibacterial property.2. Reduced graphene oxide based antibacterial surface. Photo-activated antibacterial surfaces are attractive due to its controllability and targetability, but most photo-activated antibacterial surfaces are based on the photodynamic activity of semiconductor materials, which produce reactive oxygen species to kill bacteria under ultraviolet light-or visible light irradiation. Here, for the first time, we reported a solar near-infrared (NIR) activated antibacterial surface via photothermal effects. The surface was prepared by coating quartz with reduced graphene oxide (rGO) via layer-by-layer process. The obtained surface with burst temperature rise under one solar irradiation can kill wide-spectrum bacteria including drug-tolerant bacteria, while not act on bacteria in dark. Further experiments proved that NIR light played the dominant role in these properties. This work highlights the potential of solar NIR-activated antibacterial surface in biomedical area.3. Antibacterial property of graphene oxide quantum dots (GQD). Based on previous work in antibacterial property of GO, small size GO including GQD can be deduced as inactivation against bacteria. Fullrene sourced GQD (C60-GQD) is another kind of GQD which have pentagons and hexagons, different from graphene sourced GQD (GO-GQD) having only hexagons. Antibacterial assays showed that C60-GQD had specific activity against S. aureus, less activity against E.coli cells and no activity against B.subtilis and P.aeruginosa, wharease, GO-GQD was inactive against all four kinds of bacteria. Details revealed that C60-GQD was adsorbed on the surface of S.aureus and impacted the integrity of cell envelope, and surface Guassian curvature match existed between C60-GQD and S. aureus. This work proves that surface Guassian curvature match determines the antibacterial property of GQD and suggests a route to design narrow-spectrum antibacterial agent.