Functionalized graphene oxide nanosheets with unique three-in-one properties for efficient and tunable antibacterial app
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RACT Developing antibiotics-independent antibacterial agents is of great importance since antibiotic therapy faces great challenges from drug resistance. Graphene oxide (GO) is a promising agent due to its natural antibacterial mechanisms, such as sharp edgemediated cutting effect. However, the antibacterial activity of GO is limited by its negative charge and low photothermal effect. Herein, the amino-functionalized GO nanosheets (AGO) with unique three-in-one properties were synthesized. Three essential properties (positive charge, strong photothermal effect, and natural cutting effect) were integrated into AGO. The positive charge (30 mV) rendered AGO a strong interaction force with model pathogen Streptococcus mutans (330 nN). The natural cutting effect of 100 μg·mL–1 AGO caused 27% loss of bacterial viability after incubation for 30 min. Most importantly, upon the near-infrared irradiation for just 5 min, the three-in-one properties of AGO caused 98% viability loss. In conclusion, the short irradiation period and the tunable antibacterial activity confer the three-in-one AGO a great potential for clinical use.
KEYWORDS nanoparticles, nanomaterials, carbon, nano–bio interaction, dental caries, antimicrobial
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Introduction
Infection by pathogenic bacteria has substantially threatened the health of human beings. The emergence of drug resistance and the failure of antibiotic therapy aggravate this threat. In this regard, developing novel antibiotics-independent antibacterial agents is of great importance and significance. Graphene-based nanomaterials have shown great potentials in drug delivery [1, 2], tissue engineering [3, 4], immunoassay [5, 6], and cancer theranostics [7, 8]. Recently, the antibacterial activity of graphene oxide (GO) has also been reported and is partially attributed to its intrinsic physical mechanisms, such as sharp edge-mediated cutting effect [9–12]. This natural antibacterial activity confers GO a certain degree of potential for the antibiotics-independent therapy. However, the negative charge and low photothermal effect of GO largely limit its antibacterial activity and practical use. As we know, the surface of bacterial cells is negatively charged [13–15]. It is assumed that the negative charge of GO may lead to a significant electrostatic repulsive force and ultimately a weak interaction with bacterial cells. Undoubtedly, the weak interaction will reduce the strength of the cutting effect of GO and lead to the limited antibacterial activity. In the aspect of photothermal effect, GO which loses the structure and properties of pristine graphene to a large extent has a significantly weaker photothermal effect than its reduced form [16, 17]. Hence, GO alone is almost not used for photothermal therapy. Address correspondence to [email protected]
In order to enhance the antibacterial activity of GO, forming nanocomposites with other antibacterial and/or photothermal agents, such as noble metal nanomaterials AgNP and AuNP, has been exploited [18, 19]. However, some essential concerns
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