Wenbing Hu

Graphene-Based Antibacterial Paper

Graphene is a monolayer of tightly packed carbon atoms that possesses many interesting properties and has numerous exciting applications. In this work, we report the antibacterial activity of two water-dispersible graphene derivatives, graphene oxide (GO) and reduced graphene oxide (rGO) nanosheets. Such graphene-based nanomaterials can effectively inhibit the growth of E. coli bacteria while showing minimal cytotoxicity. We have also demonstrated that macroscopic freestanding GO and rGO paper can be conveniently fabricated from their suspension via simple vacuum filtration. Given the superior antibacterial effect of GO and the fact that GO can be mass-produced and easily processed to make freestanding and flexible paper with low cost, we expect this new carbon nanomaterial may find important environmental and clinical applications.

Protein Corona-Mediated Mitigation of Cytotoxicity of Graphene Oxide

Graphene is a single layer of sp(2)-bonded carbons that has unique and highly attractive electronic, mechanical, and thermal properties. Consequently, the potential impact of graphene and its derivatives (e.g., graphene oxide, GO) on human and environmental health has raised considerable concerns. In this study, we have carried out a systematic investigation on cellular effects of GO nanosheets and identified the effect of fetal bovine serum (FBS), an often-employed component in cell culture medium, on the cytotoxicity of GO. At low concentrations of FBS (1%), human cells were sensitive to the presence of GO and showed concentration-dependent cytotoxicity. Interestingly, the cytotoxicity of GO was greatly mitigated at 10% FBS, the concentration usually employed in cell medium. Our studies have demonstrated that the cytotoxicity of GO nanosheets arises from direct interactions between the cell membrane and GO nanosheets that result in physical damage to the cell membrane. This effect is largely attenuated when GO is incubated with FBS due to the extremely high protein adsorption ability of GO. The observation of this FBS-mitigated GO cytotoxicity effect may provide an alternative and convenient route to engineer nanomaterials for safe biomedical and environmental applications.

Intracellular Imaging with a Graphene-Based Fluorescent Probe

Graphene is an increasingly important nanomaterial that has shown great promise in the area of nanotechnology. In this study, fluorescein-functionalized graphene oxide (GO) is synthesized via a polyethylene glycol (PEG) bridge and its application in intracellular imaging is explored. GO is an oxide form of graphene that provides an ideal platform to prepare graphene-based functional nanomaterials via chemical modification. The PEG bridge was introduced to prevent GO-induced quenching of conjugated fluorescein. The fluorescein-PEG-GO conjugate thus prepared exhibits excellent pH-tunable fluorescent properties and, more significantly, can be efficiently taken up by cells and serve as a fluorescent nanoprobe for intracellular imaging.

Long-Term Antimicrobial Effect of Silicon Nanowires Decorated with Silver Nanoparticles

Silicon nanowires (SiNWs), as a novel one-dimensional semiconducting nanomaterial, are attracting increasing interest in recent years. The synthesis of SiNWs with in situ grown silver nanoparticles (AgNPs) (SiNWs@AgNPs) is reported and the highly effective and long-term antibacterial activity of this novel nanostructure is demonstrated.

Synthesis of polymer-protected graphene by solvent-assisted thermal reduction process.

Polyvinylpyrrolidone-protected (PVP-protected) graphene was synthesized by refluxing graphene oxide (GO) in dimethylformamide (DMF), using PVP as the dispersant. The structure and stability of this composite (DMF-rGO) were characterized using UV-vis spectroscopy, atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results confirm the presence of a single sheet of DMF-rGO with PVP of 42%. This kind of chemically reduced GO has a greater solubility in water and also is more biocompatible than rGO reduced by hydrazine hydrate. This method is simple, environmentally friendly and the composite has potential applications in biology and polymer nanocomposites.

Nanomaterial-Based Antibacterial Paper

Antibacterial materials are widely used in everyday life and plays important roles in the public health system. There are a wide range of materials that have been known to prevent attachment and proliferation of microbes on material surfaces. These include antibiotics, metal ions and quaternary ammonium compounds. Given the availability of these various antibacterial materials, concerns about antibiotics-resistance, environmental pollution, relatively complex processing and high cost have been of much recent interest. Antimicrobial properties of nanomaterials have been explored to meet these challenges. Various nanomaterials including silver nanoparticles (AgNPs), titanium oxide nanoparticles and carbon nanotubes (CNTs) have been found to be highly effective bacterial-killing materials. The most well-known examples are silver and silver-based compounds, which were well known to be antiseptic to a spectrum of bacterium even in ancient times. AgNPs have proven to possess high antibacterial activity with minimal perturbation to human cells. Consequently, widespread applications of AgNPs have been found in medical and environmental areas [1]. More recently, carbon nanomaterials have emerged as a type of novel antibacterial nanomaterials, including CNTs and graphene. In this chapter, we aim to provide a review on the fabrication of nanomaterials-based paper-like films and their antibacterial applications.