Preparation of blue- and green-emissive nitrogen-doped graphene quantum dots from graphite and their application in bioimaging.

Owing to the superior photoluminescence property, low toxicity and good biocompatibility, nitrogen-doped graphene quantum dots (NGQDs) have been regarded as promising nanomaterials for biological applications such as bioimaging. However, many of the preparation methods are complicated, high cost, eco-unfriendly, and with a low product yield. Here, we demonstrate a novel top-down approach for NGQDs preparation, in which the low cost graphite was used as a precursor, ammonium persulfate as an oxidative molecule and nitrogen source, and H2O2 as an oxidative agent, N-methyl-2-pyrrolidone as a solvent and potential functionalizer. Meanwhile, the solvent extraction was applied for the first time to purify NGQDs. The separated NGQDs display green and blue fluorescence, deriving from the difference sizes and nitrogen doped types. The total product yield of NGQDs is calculated to be about 52%, containing 88% of green-emissive NGQDs and 12% of blue-emissive NGQDs. Meanwhile, our NGQDs own low cytotoxicity, and display a good bioimaging performance in the in vitro and in vivo investigation. The synthesis idea in our work might be also applicable to obtain other kinds of quantum dots from the readily obtainable bulk materials.

Antibacterial Carbon-Based Nanomaterials.

The emergence and global spread of bacterial resistance to currently available antibiotics underscore the urgent need for new alternative antibacterial agents. Recent studies on the application of nanomaterials as antibacterial agents have demonstrated their great potential for management of infectious diseases. Among these antibacterial nanomaterials, carbon-based nanomaterials (CNMs) have attracted much attention due to their unique physicochemical properties and relatively higher biosafety. Here, a comprehensive review of the recent research progress on antibacterial CNMs is provided, starting with a brief description of the different kinds of CNMs with respect to their physicochemical characteristics. Then, a detailed introduction to the various mechanisms underlying antibacterial activity in these materials is given, including physical/mechanical damage, oxidative stress, photothermal/photocatalytic effect, lipid extraction, inhibition of bacterial metabolism, isolation by wrapping, and the synergistic effect when CNMs are used in combination with other antibacterial materials, followed by a summary of the influence of the physicochemical properties of CNMs on their antibacterial activity. Finally, the current challenges and an outlook for the development of more effective and safer antibacterial CNMs are discussed.

Nitrogen-doped graphene quantum dots coupled with photosensitizers for one-/two-photon activated photodynamic therapy based on a FRET mechanism.

A novel material with a large two-photon absorption cross-section was conjugated with a typical photosensitizer for inducing a FRET process. The photosensitizer can be excited by a one-/two-photon laser and then induced photo-toxicity in vitro and in vivo. The system presents great potential for improving treatment depth and the precision of traditional photodynamic therapy.

Phytochemical characterisation of an important medicinal plant, Chenopodium ambrosioides Linn.

The project was intended to the phytochemical characterisation from the rudimentary methanolic extract of Chenopodium ambrosioides Linn., which escorts to the isolation of stigmasterol (1), ß-sitosterol (2), octadecanoic acid (3), scopoletin (4) and 1-piperoylpiperidine (5). Literature validates the medicinal authentication of these compounds extorted from other sources, while our previous findings regarding microbial activities of different solvent systems fractions are favouring the presence of medicinally important compounds in this species. Herein, however, we report these natural products for the first time from this species.

Electron spin resonance and fluorescence imaging assisted electrochemical approach for accurate and comprehensive monitoring of cellular hydrogen peroxide dynamics.

Dynamic alteration in the levels of cellular hydrogen peroxide (H2O2) is closely related to a variety of human diseases, as well as signal transduction pathways that regulate cell survival and death. Although qualitative or quantitative methods are available for measuring either intra- or extra-cellular H2O2 levels, accurate and comprehensive in situ detection of the real-time H2O2 dynamics of living cells remains a significant challenge. To solve this problem, a novel multi-dimensional in situ cell assay platform combining electrochemistry, electron spin resonance (ESR) and optical imaging is designed. In this platform, the real-time concentration of extracellular H2O2 released from stimulated cells can be accurately detected by ESR assisted chronoamperometry, while the level of intracellular H2O2 is simultaneously monitored via the incorporated fluorescence imaging. Accurately and simultaneously analyzing the level variations of extra- and intra-cellular reactive oxygen species based on our assay platform can complement each other for further precise and in-depth investigation of their membrane transport and related cellular signaling, which will benefit disease diagnosis and treatment.

In vitro enzyme inhibition activities of crude ethanolic extracts derived from medicinal plants of Pakistan.

Twenty two crude ethanolic extracts from 14 indigenous medicinal plants were subjected to enzyme inhibition screening against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and lipoxygenase enzymes (LO). Three extracts showed activity against AChE, nine extracts were found to be active against BChE and four extracts inhibited the enzyme LO. The most significant inhibition activities (> or =50%) were found in extracts derived from Aloe vera (leaves), Alpinia galanga (rhizome), Curcuma longa (rhizome), Cymbopogon citratus (leaves), Ocimum americanum (leaves), Ocimum americanum (stem) and Withania somnifera (roots).