Reduced graphene oxide and ZnO decorated graphene for biomedical applications

Chelating ZnO-dopamine on the surface of graphene oxide and its application as pH-responsive and antibacterial nanohybrid delivery agent for doxorubicin

This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties.

Recent Advances in Zinc Oxide Nanostructures with Antimicrobial Activities.

Microbial infections are considered one of the most dangerous infections in humans due to their resistance to most antimicrobial agents. In this study, nanocomposites based on reduced graphene oxide (RGO) and metal oxides (NiO, AgO, and ZnO) were fabricated. The graphite precursor and RGO were characterized by XRD, Raman spectroscopy, SEM, and HRTEM, while SEM, XRD, and EDX mapping analysis validated the synthesized nanocomposites. In addition, ZOI and MIC were employed to test the antimicrobial potential, while their antibiofilm activity and the effect of UV illumination were also investigated. Finally, reaction mechanism determination was performed using SEM analysis. The results revealed that all the synthesized nanocomposites (RGO-NiO, RGO-AgO, and RGO-ZnO) had outstanding antimicrobial activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), unicellular fungi (Candida albicans and Cryptococcus neoformans) and multicellular fungi (Aspergillus niger, A. terreus, A. flavus and A. fumigatus). Moreover, the synthesized RGO-NiO nanocomposite exhibited antibiofilm activity (following 10.0 µg mL−1 RGO-NiO), with an inhibition percentage of 94.60% for B. subtilis, 91.74% for P. aeruginosa, and 98.03% for C. neoformans. The maximum percentage inhibition under UV illumination toward P. aeruginosa, B. subtilis and C. neoformans at the end of the experiment using RGO-NiO were 83.21%, 88.54%, and 91.15%, respectively, while the values of RGO-AgO were 64.85%, 68.0%, and 80.15%, respectively, and those of RGO-ZnO were 72.95%, 82.15%, and 79.25%, respectively. The SEM analysis of C. neoformans in the absence of the RGO-NiO nanocomposite showed the development of unicellular fungal cells by regular budding. In contrast, after RGO-NiO treatment, noticeable morphological differences were identified in C. neoformans, including the lysis of the outer surface with deformations of the fungal cells. In conclusion, the prepared nanocomposites are promising antimicrobial and antibiofilm agents and can be used to treat the pathogenic microbes at low concentrations and represent a new strategy for managing infectious diseases caused by pathogenic microorganisms.

/pdf/promising-antimicrobial-and-antibiofilm-activities-of-2gaj26or62.pdf

Promising antimicrobial and antibiofilm activities of reduced graphene oxide-metal oxide (RGO-NiO, RGO-AgO, and RGO-ZnO) nanocomposites

Antibacterial effects of graphene- and carbon-nanotube-based nanohybrids on Escherichia coli: Implications for treating multidrug-resistant bacteria.

In this work, we report a simple and facile one-pot chemical approach of the decoration of uniform zinc oxide nanoparticles (ZnO NPs) on reduced graphene oxide (GO) and a study of its antimicrobial activity. The nanocomposite was fully characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). TEM and SEM images clearly indicated the presence of Graphene sheets decorated with uniformly sized zinc oxide nanoparticles. Further, as an application of rGO-ZnO nanocomposites, their superior antibacterial activity was demonstrated on the Escherichia coli MTCC40 bacterial strain, using the standard disk diffusion method. This clearly showed that rGO-ZnO nanocomposites exhibited more pronounced antibacterial activity than rGO alone. This feature was revealed to be due to increased biocompatibility of PEGylated rGO-ZnO nanocomposites. In conclusion, the as-synthesized nanocomposite showed excellent antibacterial activity and has great potential for biomedical application.

https://iopscience.iop.org/article/10.1088/2053-1591/aa5bff/pdf

Rishabh Shrivastava Ronin

Papers

Synthesis, characterization and enhanced antimicrobial activity of reduced graphene oxide–zinc oxide nanocomposite