Abstract
Graphene oxide (GO) composites with various metal nanoparticles (NPs) are attracting increasing interest owing to their broad scope in biomedical applications. Here, microwave-assisted chemical reduction was used to deposit nano-silver and zinc oxide NPs (Ag and ZnO NPs) on the surface of reduced GO (rGO) at the following weight percentages: 5.34% Ag/rGO, 7.49% Ag/rGO, 6.85% ZnO/rGO, 16.45% ZnO/rGO, 3.47/34.91% Ag/ZnO/rGO, and 7.08/15.28% Ag/ZnO/rGO. These materials were tested for antibacterial activity, and 3.47/34.91% Ag/ZnO/rGO and 7.08/15.28% Ag/ZnO/rGO exhibited better antibacterial activity than the other tested materials against the gram-negative bacterium Escherichia coli K12. At 1000 ppm, both these Ag/ZnO/rGO composites had better killing properties against both E. coli K12 and the gram-positive bacterium Staphylococcus aureus SA113 than Ag/rGO and ZnO/rGO did. RedoxSensor flow cytometry showed that 3.47/34.91% Ag/ZnO/rGO and 7.08/15.28% Ag/ZnO/rGO decreased reductase activity and affected membrane integrity in the bacteria. At 100 ppm, these two composites affected membrane integrity more in E. coli, while 7.08/15.28% Ag/ZnO/rGO considerably decreased reductase activity in S. aureus. Thus, the 3.47/34.91% and 7.08%/15.28% Ag/ZnO/rGO nanocomposites can be applied not only as antibacterial agents but also in a variety of biomedical materials such as sensors, photothermal therapy, drug delivery, and catalysis, in the future.
Highlights
Graphene oxide (GO) has six carbon atoms of graphene with several oxygen functional groups such as the hydroxyl (-OH), epoxy (-CH-O-CH), and carboxyl (-C-OH) groups
We examined whether 3.47/34.91% and 7.08/15.28% Ag/ZnO/reduced GO (rGO) affected reductase activity in S. aureus and E. coli by RedoxSensor staining
We found that 7.49% Ag/rGO, 3.47/34.91% Ag/ZnO/rGO, and 7.08/15.28% Ag/ZnO/rGO composites had at least 10-fold higher killing effect than E. coli-killing effect reported by Ko et al [29]
Summary
Graphene oxide (GO) has six carbon atoms of graphene with several oxygen functional groups such as the hydroxyl (-OH), epoxy (-CH-O-CH), and carboxyl (-C-OH) groups. GO is dispersed in water and decomposed into macroscopic sheets These sheets undergo chemical reduction to produce graphene. The recent synthesis of GO composites with various metal nanoparticles (NPs) has attracted wide interest owing to their potential applications in a range of biomedical materials [14,15,16,17,18]. Due to their high surface area, GO composites support the growth and stability of metal NPs and prevent them from agglomerating. Research on the antibacterial activity of graphene and metal nanocomposites has been rather limited
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