Background: Graphene holds great promise for potential use in next-generation electronic and photonic devices due to its unique high carrier mobility, good optical transparency, large surface area, and biocompatibility. The aim of this study was to investigate the antibacterial effects of graphene oxide (GO) and reduced graphene oxide (rGO) in Pseudomonas aeruginosa. In this work, we used a novel reducing agent, betamercaptoethanol (BME), for synthesis of graphene to avoid the use of toxic materials. To uncover the impacts of GO and rGO on human health, the antibacterial activity of two types of graphene-based material toward a bacterial model P. aeruginosa was studied and compared. Methods: The synthesized GO and rGO was characterized by ultraviolet-visible absorption spectroscopy, particle-size analyzer, X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Further, to explain the antimicrobial activity of graphene oxide and reduced graphene oxide, we employed various assays, such as cell growth, cell viability, reactive oxygen species generation, and DNA fragmentation. Results: Ultraviolet-visible spectra of the samples confirmed the transition of GO into graphene. Dynamic light-scattering analyses showed the average size among the two types of graphene materials. X-ray diffraction data validated the structure of graphene sheets, and high-resolution scanning electron microscopy was employed to investigate the morphologies of prepared graphene. Raman spectroscopy data indicated the removal of oxygen-containing functional groups from the surface of GO and the formation of graphene. The exposure of cells to GO and rGO induced the production of superoxide radical anion and loss of cell viability. Results suggest that the antibacterial activities are contributed to by loss of cell viability, induced oxidative stress, and DNA fragmentation. Conclusion:The antibacterial activities of GO and rGO against P. aeruginosa were compared. The loss of P. aeruginosa viability increased in a dose-and time-dependent manner. Exposure to GO and rGO induced significant production of superoxide radical anion compared to control. GO and rGO showed dose-dependent antibacterial activity against P. aeruginosa cells through the generation of reactive oxygen species, leading to cell death, which was further confirmed through resulting nuclear fragmentation. The data presented here are novel in that they prove that GO and rGO are effective bactericidal agents against P. aeruginosa, which would be used as a future antibacterial agent.

Silver nanoparticles (AgNPs) have been used as an antimicrobial and disinfectant agents. However, there is limited information about antitumor potential. Therefore, this study focused on determining cytotoxic effects of AgNPs on MDA-MB-231 breast cancer cells and its mechanism of cell death. Herein, we developed a green method for synthesis of AgNPs using culture supernatant of Bacillus funiculus, and synthesized AgNPs were characterized by various analytical techniques such as UV-visible spectrophotometer, particle size analyzer, and transmission electron microscopy (TEM). The toxicity was evaluated using cell viability, metabolic activity, and oxidative stress. MDA-MB-231 breast cancer cells were treated with various concentrations of AgNPs (5 to 25 μg/mL) for 24 h. We found that AgNPs inhibited the growth in a dose-dependent manner using MTT assay. AgNPs showed dose-dependent cytotoxicity against MDA-MB-231 cells through activation of the lactate dehydrogenase (LDH), caspase-3, reactive oxygen species (ROS) generation, eventually leading to induction of apoptosis which was further confirmed through resulting nuclear fragmentation. The present results showed that AgNPs might be a potential alternative agent for human breast cancer therapy.

Background: This paper describes an environmentally friendly ("green") approach for the synthesis of soluble graphene using Bacillus marisflavi biomass as a reducing and stabilizing agent under mild conditions in aqueous solution. In addition, the study reported here investigated the cytotoxicity effects of graphene oxide (GO) and bacterially reduced graphene oxide (B-rGO) on the inhibition of cell viability, reactive oxygen species (ROS) generation, and membrane integrity in human breast cancer cells. Methods: The reduction of GO was characterized by ultraviolet-visible spectroscopy. Size distribution was analyzed by dynamic light scattering. Further, X-ray diffraction and highresolution scanning electron microscopy were used to investigate the crystallinity of graphene and the morphologies of prepared graphene, respectively. The formation of defects further supports the bio-functionalization of graphene, as indicated in the Raman spectrum of B-rGO. Surface morphology and the thickness of the GO and B-rGO were analyzed using atomic force microscopy, while the biocompatibility of GO and B-rGO were investigated using WST-8 assays on MCF-7 cells. Finally, cellular toxicity was evaluated by ROS generation and membrane integrity assays. Results:In this study, we demonstrated an environmentally friendly, cost-effective, and simple method for the preparation of water-soluble graphene using bacterial biomass. This reduction method avoids the use of toxic reagents such as hydrazine and hydrazine hydrate. The synthesized soluble graphene was confirmed using various analytical techniques. Our results suggest that both GO and B-rGO exhibit toxicity to MCF-7 cells in a dose-dependent manner, with a dose . 60 µg/mL exhibiting obvious cytotoxicity effects, such as decreasing cell viability, increasing ROS generation, and releasing of lactate dehydrogenase. Conclusion: We developed a green and a simple approach to produce graphene using bacterial biomass as a reducing and stabilizing agent. The proposed approach confers B-rGO with great potential for various biological and biomedical applications.

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Due to unique properties and unlimited possible applications, graphene has attracted abundant interest in the areas of nanobiotechnology. Recently, much work has focused on the synthesis and properties of graphene. Here we show that a successful reduction of graphene oxide (GO) using spinach leaf extract (SLE) as a simultaneous reducing and stabilizing agent. The as-prepared SLE-reduced graphene oxide (S-rGO) was characterized by ultraviolet–visible spectroscopy and Fourier transform infrared spectroscopy. Dynamic light scattering technique was used to determine the average size of GO and S-rGO. Scanning electron microscopy and atomic force microscopy images provide clear surface morphological evidence for the formation of graphene. The resulting S-rGO has a mostly single-layer structure, is stable, and has significant water solubility. In addition, the biocompatibility of graphene was investigated using cell viability, leakage of lactate dehydrogenase and alkaline phosphatase activity in primary mouse embryonic fibroblast (PMEFs) cells. The results suggest that the biologically synthesized graphene has significant biocompatibility with PMEF cells, even at a higher concentration of 100 μg/mL. This method uses a ‘green’, natural reductant and is free of additional stabilizing reagents; therefore, it is an environmentally friendly, simple, and cost-effective method for the fabrication of soluble graphene. This study could open up a promising view for substitution of hydrazine by a safe, biocompatible, and powerful reduction for the efficient deoxygenation of GO, especially in large-scale production and potential biomedical applications.