Recently, graphene oxide (GO) based nanocomposites have raised significant interests in many different areas, one of which being antibacterial agents where sliver nanoparticle (AgNPs) anchored GO (GO-Ag) has shown promising potential. However, to our best knowledge, factors affecting its antibacterial activity as well as the underlying mechanism remain unclear. In this study, we fabricate GO-Ag nanocomposites with different AgNPs to GO ratios and carefully investigate their antibacterial activities against both the Gram-negative (G-) bacteria Escherichia coli ( E. coli ) and the Gram-positive (G+) bacteria Staphylococcus aureus ( S. aureus ). We discover that, compared to AgNPs, GO-Ag nanocomposite with an optimal ratio of AgNPs to GO is much more effective and shows synergistically enhanced, strong antibacterial activities at rather low dose (2.5 μg/mL). The GO-Ag nanocomposite is more toxic to E. coli than that to S. aureus . The antibacterial effects of GO-Ag nanocomposite are further investigated, revealing distinct, species-specific mechanisms. The results demonstrate that GO-Ag nanocomposite functions as a bactericide against the G- E. coli through disrupting bacterial cell wall integrity, whereas it exhibits bacteriostatic effect on the G+ S. aureus by dramatically inhibiting cell division. Our work not only highlights the great promise of using GO-Ag as a highly effective antibacterial agent but also provides more in-depth understandings of the interactions between microorganisms and GO-based nanocomposites.

Photothermal therapy (PTT), as a minimally invasive and highly effective cancer treatment approach, has received widespread attention in recent years. Tremendous effort has been devoted to explore various types of photothermal agents with high near-infrared (NIR) absorbance for PTT cancer treatment. Despite many exciting progresses in the area, effective yet safe photothermal agents with good biocompatibility and biodegradability are still highly desired. In this work, a new organic PTT agent based on polyethylene glycol (PEG) coated micelle nanoparticles encapsulating a heptamethine indocyanine dye IR825 is developed, showing a strong NIR absorption band and a rather low quantum yield, for in vivo photothermal treatment of cancer. It is found that the IR825-PEG nanoparticles show ultra-high in vivo tumor uptake after intravenous injection, and appear to be an excellent PTT agent for tumor ablation under a low-power laser irradiation, without rendering any appreciable toxicity to the treated animals. Compared with inorganic nanomaterials and conjugated polymers being explored in PTT, the NIR-absorbing micelle nanoparticles presented here may have the least safety concern while showing excellent treatment effi cacy, and thus may be a new photothermal agent potentially useful in clinical applications.

Background and Purpose-Activation of NMDA subtypes of glutamate receptors is implicated in cell damage induced by ischemia as well as for the establishment of ischemic tolerance after ischemic preconditioning in animal models. We investigated the contributions of NR2A-and NR2B-containing NMDA receptors to ischemic cell death and ischemic tolerance in a rat model of transient global ischemia. Methods-Transient global ischemia was produced in rats by 4-vessel occlusion. Neuronal injury was analyzed by Fluoro-Jade B and Nissl staining. Phosphorylation of CREB was detected by Western blotting and immunohistochemistry. In situ hybridization and reverse transcriptase-polymerase chain reaction were used to evaluate the mRNA level of cpg15 and bdnf. Results-NR2A subtype-specific antagonist NVP-AAM077 enhanced neuronal death after transient global ischemia and abolished the induction of ischemic tolerance. In contrast, NR2B subtype-specific antagonist ifenprodil attenuated ischemic cell death and enhanced preconditioning-induced neuroprotection. Furthermore, selectively blocking NR2A-, but not NR2B-, containing NMDA receptors inhibited ischemia-induced phosphorylation of CREB and the subsequent upregulation of CREB target genes such as cpg15 and bdnf. Conclusions-We found that NR2A-and NR2B-containing NMDA receptor subtypes play differential roles in ischemic neuronal death and ischemic tolerance, suggesting attractive new strategies for the development of drugs for patients with stroke. (Stroke. 2008;39:3042-3048.)

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Model cellulose surfaces have attracted increasing attention for studying interactions with cell wall matrix polymers and as substrates for enzymatic degradation studies. Quartz crystal microbalance with dissipation monitoring (QCM-D) solvent exchange studies showed that the water content of regenerated cellulose (RC) films was proportional to the film thickness (d) and was consistent with about five water molecules per anhydroglucose unit. Sulfated nanocrystalline cellulose (SNC) and desulfated nanocrystalline cellulose (DNC) films had comparable water contents and contained about five times more water than RC films. A cellulase mixture served as a probe for studies of substrate accessibility and degradation. Cellulase adsorption onto RC films was independent of d, whereas degradation times increased with d. However, adsorption onto SNC and DNC films increased with d, whereas cellulase degradation times for DNC films were independent of studied d. Enhanced access to guest molecules for SNC and DNC films revealed they are more porous than RC films.

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Despite considerable efforts to prevent lithium (Li) dendrite growth, stable cycling of Li metal anodes with various structures remains extremely difficult due to the direct contact of the liquid electrolyte with Li. Rational design of solid‐electrolyte interphase (SEI) for 3D electrodes is a promising but still challenging strategy for preventing Li dendrite growth and avoiding lithium–electrolyte side reactions in Li‐metal batteries. Here, a 3D architecture is constructed with g‐C3N4/graphene/g‐C3N4 insulator–metal–insulator sandwiched nanosheets to guide uniform Li plating/stripping in the van der Waals gap between the graphene and the g‐C3N4, and the function of which can be regarded as a 3D artificial SEI. Li deposition on the surface of g‐C3N4 is suppressed due to its insulating nature. However, its uniform lithiophilic sites and nanopore channels enable homogeneous lithium plating between the graphene and the g‐C3N4, prohibiting the direct contact of the electrolyte with the Li metal. The use of the g‐C3N4‐layer‐modified 3D anode enables long‐term Li deposition with a high Coulombic efficiency and stable cycling of full cells under high cathode loading, limited Li excess, and lean electrolyte conditions. The concept of a 3D artificial SEI will shed light on developing safe and stable Li‐metal anodes.

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