Abstract
The fabrication, characterization, and antibacterial activity of novel nanocomposites based on graphene oxide (GO) nanosheets decorated with silver, titanium dioxide nanoparticles, and zinc oxide nanoflowers were examined. The fabricated nanocomposites were characterized by various techniques including X-ray diffraction, ultraviolet-visible light absorption and fluorescence spectroscopy, Brunauer–Emmett–Teller theory analysis, Fourier transform infrared, and scanning electron microscopy. The antibacterial activity of the GO–metal oxide nanocomposites against two Gram-positive and two Gram-negative bacteria was examined by using the standard counting plate methodology. The results showed that the fabricated nanocomposites on the surface of GO could inhibit the growth of microbial adhered cells, and consequently prevent the process of biofilm formation in food packaging and medical devices. To confirm the antibacterial activity of the examined GO-nanocomposites, we examined their interactions with bovine serum albumin (BSA) and circulating tumor DNA (ctDNA) by steady-state fluorescence spectroscopy. Upon addition of different amounts of fabricated GO-nanocomposites, the fluorescence intensities of the singlet states of BSA and ctDNA were considerably quenched. The higher quenching was observed in the case of GO–Ag–TiO2@ZnO nanocomposite compared with other control composites.
Highlights
Microorganisms, such as bacteria communities, are found in many different environments, and can anchor on various surfaces to produce bio lms that o en show high resistance to antimicrobial drugs.[1,2] In the food industry, the presence of bio lms leads to severe hygiene problems, economic losses, food spoilage, and even serious infectious diseases.[2,3,4,5] Escherichia coli (E. coli) is a bacterial commensal micro ora in the intestinal tract of a number of animals, including humans
The presence of Ag nanoparticles over the graphene oxide (GO) surface in the nanocomposite (GO–Ag) was con rmed by recording peaks at 2q 1⁄4 37.7, 44.3, 64.0, and 77.0.57,58 GO–TiO2@zinc oxide (ZnO) nanocomposite showed the characteristic peaks of ZnP nanoparticles at 31.67, 34.31, 36.1, 56.5, 62.7, and 67.9,59 while the TiO2 pattern showed values for the diffraction peak at 25 and 47.59.60 The slight shi to the lower region side might be due to the loading of TiO2 and ZnO NPs on the GO surface
GO–Ag–TiO2@ZnO nanocomposite showed a sharp highly intensive peak at 37.8, 44, 64.2, and 77.2, 47.3, and 31.67, 34.31, 36.1, 56.39, 62.7, and 67.9. These features suggest that the metal oxides (ZnO, TiO2) and Ag NPs are loaded on the GO surface
Summary
The resistance of bacteria and fungi to traditional antibiotics is an increasing problem, and the identi cation and treatment of antibiotic-resistant microorganisms is difficult and costly.[9,10] complications associated with antibiotic-resistant bacterial infections are a cause of high morbidity and mortality, with antibiotic resistance leading to challenges such as inhibition of drug uptake, enzymatic modi cation of antibiotics, and alteration of target molecules. Several considerations led us to design the GO–Ag–TiO2@ZnO nanocomposite: (1) GO has the advantages of ease of fabrication, ease of processing, and economic production, with large scale and low cost; (2) GO has mild cytotoxicity to mammalian cells in low dose; (3) GO exhibits high antibacterial efficiency in its ability to damage the cell membranes via the generation of reactive oxygen species (ROS) and has exceptionally sharp edges; (4) Ag nanoparticles can consistently cause bacterial cell membrane damage, disturbing DNA replication, and leading to increased permeability and cell death;[42,43,44,45,46] (5) TiO2 could be used for the killing or growth inhibition of bacteria due to its strong oxidation activity and super hydrophilicity; (6) ZnO exhibits antibacterial activity through generation of ROS and/or accumulation of NPs in the cytoplasm that lead to the interruption and inhibition of membrane and cellular tasks. The results showed the excellent ability of the fabricated nanocomposite (GO–Ag–TiO2@ZnO) against growth of bacteria by destroying the DNA bacteria; this was con rmed with both Gram-positive and Gram-negative bacteria
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