Showing papers by "Lifeng Yan published in 2012"

Association of the maternal MTHFR C677T polymorphism with susceptibility to neural tube defects in offsprings: evidence from 25 case-control studies.

Abstract: Background Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in folate metabolism and is involved in DNA methylation, DNA synthesis, and DNA repair. In addition, it is a possible risk factor in neural tube defects (NTDs). The association of the C677T polymorphism in the MTHFR gene and NTD susceptibility has been widely demonstrated, but the results remain inconclusive. In this study, we performed a meta-analysis with 2429 cases and 3570 controls to investigate the effect of the MTHFR C677T polymorphism on NTDs. Methods An electronic search of PubMed and Embase database for papers on the MTHFR C677T polymorphism and NTD risk was performed. All data were analysed with STATA (version 11). Odds ratios (ORs) with 95% confidence intervals (CIs) were estimated to assess the association. Sensitivity analysis, test of heterogeneity, cumulative meta-analysis, and assessment of bias were performed in our meta-analysis. Results A significant association between the MTHFR C677T polymorphism and NTD susceptibility was revealed in our meta-analysis ( TT versus CC: OR = 2.022, 95% CI: 1.508, 2.712; CT+TT versus CC: OR = 1.303, 95% CI: 1.089, 1.558; TT versus CC+CT: OR = 1.716, 95% CI: 1.448, 2.033; 2TT+CT versus 2CC+CT: OR = 1.330, 95% CI: 1.160, 1.525). Moreover, an increased NTD risk was found after stratification of the MTHFR C677T variant data by ethnicity and source of controls. Conclusion The results suggested the maternal MTHFR C677T polymorphism is a genetic risk factor for NTDs. Further functional studies to investigate folate-related gene polymorphisms, periconceptional multivitamin supplements, complex interactions, and the development of NTDs are warranted.

Synthesis of Disulfide-Cross-Linked Polypeptide Nanogel Conjugated with a Near-Infrared Fluorescence Probe for Direct Imaging of Reduction-Induced Drug Release

Abstract: Reduction-sensitive polymeric nanocarrier with near-infrared fluorescence probe has been prepared. Disulfide-cross-linked polypeptide nanogel with near-infrared fluorescence property (NIRF nanogel) was first synthesized, then the anticancer drug doxorubicin was encapsulated into polypeptide core of the NIRF nanogel to prepare a drug carrier with near-infrared fluorescence (NIRF prodrug). In vitro drug release study of the NIRF prodrug revealed an accelerated release behavior in the presence of 10 mM glutathione (GSH). Cellular uptake studies of both the NIRF nanogel and NIRF prodrug showed that they could enter cell via endocytosis. With the aid of NIRF labeling, direct imaging of the drug release from NIRF nanogel was accomplished, and drug molecules released subsequently migrated into nucleus while the NIRF nanogel still remained in cytoplasm. In vivo distribution of the NIRF nanogel and NIRF prodrug on tumor-bearing nude mice shows that both of them accumulated at tumor place at 24 h after tail veil in...

Amino-grafted graphene as a stable and metal-free solid basic catalyst

Abstract: Metal-free catalysts are essential for various chemical reactions in industrial chemistry. Amino-functionalized carbon is a cheap and environmentally friendly solid basic catalyst. Here, NEt3-graphene solid basic catalyst has been synthesized through a consecutive deprotonation/carbometalation and electrophilic substituent. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), elemental analyses, thermal analyses, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) studies confirmed the formation of the target structure. Catalytic hydrolysis of ethyl acetate reveals that the amino-grafted graphene has a high catalytic activity.

Efficient preparation of highly hydrogenated graphene and its application as a high-performance anode material for lithium ion batteries

Abstract: A novel method has been developed to prepare hydrogenated graphene (HG) via a direct synchronized reduction and hydrogenation of graphene oxide (GO) in an aqueous suspension under 60Co gamma ray irradiation at room temperature GO can be reduced by the aqueous electrons (eaq−) while the hydrogenation takes place due to the hydrogen radicals formed in situ under irradiation The maximum hydrogen content of the as-prepared highly hydrogenated graphene (HHG) is found to be 527 wt% with H/C = 076 The yield of the target product is on the gram scale The as-prepared HHG also shows high performance as an anode material for lithium ion batteries

Centimeter‐Sized Dried Foam Films of Graphene: Preparation, Mechanical and Electronic Properties

Abstract: A simple method to fabricate centimeter-sized thin films of graphene oxide (GO) is developed via drying the relative liquid film supported by a rigid frame. After reduction, centimeter-sized thin reduced GO films are obtained, and the maximum transparency is 75.8% while the minimum sheet resistance is 920 Ω □(-1) .

Synthesis of polypeptide conjugated with near infrared fluorescence probe and doxorubicin for pH-responsive and image-guided drug delivery

Abstract: A near infrared fluorescent polymeric drug delivery system (NIRF DDS) with pH-responsive drug release properties has been designed and developed. This material was prepared by chemical conjugation of the anticancer drug doxorubicin and hydrophobic aminocyanine dye to triblock copolypeptide via hydrazone and amide bonds, respectively. Conjugation with aminocyanine shows almost no toxicity of the material, while conjugation with doxorubicin induces pronounced toxicity on the original biocompatible material. The pH sensitive drug release nature of the near infrared fluorescent polymeric drug (NIRF prodrug) was confirmed by accelerated drug release at pH of 5.0 via an in vitro drug release experiment and gradual drug cleavage from the NIRF prodrug during a confocal laser scanning microscopic (CLSM) experiment. The CLSM experiment also reveals that the released drug subsequently migrated to the nucleus, while the polymeric residue still remained in cytoplasm, indicating that the as-prepared polymer can be a promising candidate for theranosis of cancer.

Hydrogenated Graphene as Metal-free Catalyst for Fenton-like Reaction

Abstract: Carbonaceous catalysts are potential alternatives to metal catalysts. Graphene has been paid much attention for its high surface area and light weight. Here, hydrogenated graphene has been prepared by a simple gamma ray irradiation of graphene oxide aqueous suspension at room temperature. Transmission electron microscopic, element analysis, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometer studies verified the hydrogenation of graphene. The as-prepared hydrogenated graphene can be used as a metal-free carbonaceous catalyst for the Fenton-like degradation of organic dye in water.

Isolation of highly purity cellulose from wheat straw using a modified aqueous biphasic system

Abstract: Cellulose samples with molecular weights ranging from 8.39 × 104 to 11.00 × 104 g/mol were obtained from wheat straw. The dewaxed wheat straw was pretreated with aqueous hydrochloric acid followed by delignification using an environmentally benign poly (ethyleneglycol)/salt aqueous biphasic system. The yield of cellulose was in the range of 48.9%–55.5% and the cellulose contained 1.2%–3.2% hemicelluloses, and 0.97%–3.47% lignin. All the isolated cellulose samples could be directly dissolved in a 6 wt-% NaOH/4 wt-% urea aqueous solution through a precooling-thawing process to form a homogenous solution. The separation process was investigated and the obtained cellulose and its solution were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray apparatus, and X-ray diffraction. The results revealed that aqueous soluble cellulose can be directly prepared from wheat straw by this method and this study opens a novel pathway to prepare cellulosic materials from agricultural waste.