The chemical and structural analysis of graphene oxide with different degrees of oxidation

Understanding how nanomaterials interact with cell membranes is related to how they cause cytotoxicity and is therefore critical for designing safer biomedical applications. Recently, graphene (a two-dimensional nanomaterial) was shown to have antibacterial activity on Escherichia coli, but its underlying molecular mechanisms remain unknown. Here we show experimentally and theoretically that pristine graphene and graphene oxide nanosheets can induce the degradation of the inner and outer cell membranes of Escherichia coli, and reduce their viability. Transmission electron microscopy shows three rough stages, and molecular dynamics simulations reveal the atomic details of the process. Graphene nanosheets can penetrate into and extract large amounts of phospholipids from the cell membranes because of the strong dispersion interactions between graphene and lipid molecules. This destructive extraction offers a novel mechanism for the molecular basis of graphene's cytotoxicity and antibacterial activity.

Destructive extraction of phospholipids from Escherichia coli membranes by graphene nanosheets

One of the greatest challenges to the sustainability of modern society is an inadequate supply of clean water. Due to its energy-saving and cost-effective features, membrane technology has become an indispensable platform technology for water purification, including seawater and brackish water desalination as well as municipal or industrial wastewater treatment. However, membrane fouling, which arises from the nonspecific interaction between membrane surface and foulants, significantly impedes the efficient application of membrane technology. Preparing antifouling membranes is a fundamental strategy to deal with pervasive fouling problems from a variety of foulants. In recent years, major advancements have been made in membrane preparation techniques and in elucidating the antifouling mechanisms of membrane processes, including ultrafiltration, nanofiltration, reverse osmosis and forward osmosis. This review will first introduce the major foulants and the principal mechanisms of membrane fouling, and then highlight the development, current status and future prospects of antifouling membranes, including antifouling strategies, preparation techniques and practical applications. In particular, the strategies and mechanisms for antifouling membranes, including passive fouling resistance and fouling release, active off-surface and on-surface strategies, will be proposed and discussed extensively.

Antifouling membranes for sustainable water purification: strategies and mechanisms

Graphene oxide (GO) is a promising material for the development of antimicrobial surfaces due to its contact-based antimicrobial activity. However, the relationship between GO physicochemical properties and its antimicrobial activity has yet to be elucidated. In this study, we investigated the size-dependency of GO antimicrobial activity using the Gram-negative bacteria Escherichia coli. GO suspensions of average sheet area ranging from 0.01 to 0.65 μm2 were produced and their antimicrobial activity evaluated in cell suspensions or as a model GO surface coating. The antimicrobial activity of GO surface coatings increased 4-fold when GO sheet area decreased from 0.65 to 0.01 μm2. The higher antimicrobial effect of smaller GO sheets is attributed to oxidative mechanisms associated with the higher defect density of smaller sheets. In contrast, in suspension assays, GO interacted with bacteria in a cell entrapment mechanism; in this case, the antimicrobial effect of GO increased with increasing sheet area, wi...

Antimicrobial Properties of Graphene Oxide Nanosheets: Why Size Matters.

A thorough understanding of the antimicrobial mechanisms of graphene materials (GMs) is critical to the manipulation of highly efficient antimicrobial nanomaterials for future biomedical applications. Here we review the most recent studies of GM-mediated antimicrobial properties. This review covers the physicochemical properties of GMs, experimental surroundings, and selected microorganisms as well as the interaction between GMs and selected microorganisms to explore controversial antimicrobial activities. Finally, we rationally analyze the strengths and weaknesses of the proposed mechanisms and provide new insights into the remaining challenges and perspectives for future studies.

Mechanisms of the Antimicrobial Activities of Graphene Materials

Graphene nanosheets are highly recognized for their utility toward the development of biomedical device applications. The present study investigated the antibacterial efficiency of graphene nanosheets against four types of pathogenic bacteria. Graphene nanosheets are synthesized by a hydrothermal approach (under alkaline conditions using hydrazine hydrate). UV–vis and X-ray diffraction show a maximum absorbance at 267 nm and appearance of new broad diffraction peak at 26°, which ensures the reduction of graphene oxide into graphene nanosheets. Stretching and bending vibrations of C–C bonds, chemical states, disorder, and defects associated with the graphene nanosheets are evaluated in comparison with graphene oxide. The minimum inhibitory concentration (MIC) of graphene nanosheets against pathogenic bacteria was evaluated by a microdilution method. MICs such as 1 μg/mL (against Escherichia coli and Salmonella typhimurium), 8 μg/mL (against Enterococcus faecalis), and 4 μg/mL (against Bacillus subtilis) su...

Antibacterial Efficiency of Graphene Nanosheets against Pathogenic Bacteria via Lipid Peroxidation

A comprehensive investigation of anti-bacterial properties of graphene oxide (GO) and ultraviolet (UV) irradiated GO nanosheets was carried out. Microscopic characterization revealed that the GO nanosheet-like structures had wavy features and wrinkles or thin grooves. Fundamental surface chemical states of GO nanosheets (before and after UV irradiation) were investigated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Minimum inhibitory concentration (MIC) results revealed that UV irradiated GO nanosheets have more pronounced anti-bacterial behavior than GO nanosheets and standard antibiotic, kanamycin. The MIC of UV irradiated GO nanosheets was 0.125 μg ml−1 for Escherichia coli and Salmonella typhimurium, 0.25 μg ml−1 for Bacillus subtilis and 0.5 μg ml−1 for Enterococcus faecalis, ensuring its potential as an anti-infective agent for controlling the growth of pathogenic bacteria. The minimum bactericidal concentration of normal GO nanosheets was determined to be two-fold higher than its corresponding MIC value, indicating promising bactericidal activity. The mechanism of anti-bacterial action was evaluated by measuring the enzymatic activity of β-d-galactosidase for the hydrolysis of o-nitrophenol-β-d-galactopyranoside.

https://iopscience.iop.org/article/10.1088/0957-4484/24/39/395706/pdf

Surface activation of graphene oxide nanosheets by ultraviolet irradiation for highly efficient anti-bacterials

Surface chemistry of cerium oxide nanocubes: Toxicity against pathogenic bacteria and their mechanistic study

We report the fabrication and fluorescent properties of hybrid material composed of fluorescent silica nanoparticles (FSNs) functionalized multi-walled carbon nanotubes(MWCNTs). Stober method derived FSNs were successfully conjugated with MWCNTS chemically activated concentrated acids, poly(acrylic acid) (PAA) and 3-aminopropyl-trimethoxysilane (APTES) to obtain the nanocomposite FSNs/MWCNTs. Electron microscopic investigations revealed the spherical shape and smooth surface of FSNs with the diameter ~150±50 nm. Activated functional groups of MWCNTs provided the necessary support for functionalization of FSNs. FT-IR spectral analysis shows the structural integrity of FSNs, MWCNTs, and the hybrid FSNs/MWCNTs. Fluorescent emission property of FSNs/MWCNTs are observed to be significant than pristine dye fluorescein isothiocyanate and FSNs. Enhanced fluorescent emission and photostability of FSNs/MWCNTs provides promising feasibility for further exploration in biomedical applications.

Fluorescent silica nanoparticles functionalized on multi-walled carbon nanotubes: Fabrication and fluorescent properties

The present invention relates to an antibiotic composition comprising light-irradiated graphene oxide (GO) as an active ingredient, and provides graphene oxide (GO), light-irradiated circular shaped graphene oxide, or a light-irradiated graphene composite, as an active ingredient Further, the present invention provides a method for improving antibiotic activity of a graphene-based material, wherein the method comprises the steps of: (a) preparing a graphene-based material selected from the group consisting of graphene oxide (GO), circular shaped graphene oxide, and a graphene composite; and (b) photo-irradiating the graphene-based material The present invention exhibits excellent antibiotic activity against gram negative and gram positive bacteria, that is, exhibits a bacteriostatic effect/a sterilizing effect As such, the present invention has strong antibiotic activity, and thus, can be safely used as an antibiotic material applied to several fields which are directly associated with the human body

Ling-He Zhang

Papers

Antibacterial Efficiency of Graphene Nanosheets against Pathogenic Bacteria via Lipid Peroxidation

Surface activation of graphene oxide nanosheets by ultraviolet irradiation for highly efficient anti-bacterials

Surface chemistry of cerium oxide nanocubes: Toxicity against pathogenic bacteria and their mechanistic study

Fluorescent silica nanoparticles functionalized on multi-walled carbon nanotubes: Fabrication and fluorescent properties

Antibiotic composition comprising uv irradiated-graphene oxide as an active ingredient