Study on Biological Safety of Polyvinyl Alcohol/Collagen Hydrogel as a Tissue Substitute (II)

Physically crosslinked polyvinyl alcohol/collagen composite hydrogels were prepared by a cyclic freezing-drying technique. The biological properties of the hydrogels, including hemolysis, anaphylaxis, pyrogen and acute systemic toxicity tests and implantation in-vivo, were investigated. The hemolysis test suggested that the polyvinyl alcohol/collagen, with a hemolysis index of 1.19%, did not have an obvious hemolysis reaction. There was no toxicosis or death cases observed in the acute systemic toxicity test, and the hydrogel showed no anaphylaxis or pyrogen response. The composite hydrogel showed a good histological compatibility in the in-vivo study. The results indicated that the polyvinyl alcohol/collagen composite hydrogels have promising applications for pharmaceutical and biomedical fields.     

Temperature/Light Dual‐Responsive Inclusion Complexes of α‐Cyclodextrins and Azobenzene‐Containing Polymers

Three kinds of photoresponsive copolymers with azobenzene side chains were synthesized by radical polymerization of N‐4‐phenylazophenylacrylamide (PAPA) with N‐isopropylacrylamide (NIPAM), N,N‐diethylacrylamide (DEAM) or N,N‐dimethylacrylamide (DMAM) respectively. Their structures were characterized by FT‐IR, ¹H‐NMR and UV/Vis spectroscopy. Their reversible photoresponses were studied with or without α‐cyclodextrin (α‐CD), which showed that both the copolymers and their inclusion complexes with α‐CD underwent rapid photoisomerization. The lower critical solution temperature (LCST) of the copolymers and their inclusion complexes with α‐CD were investigated by cloud point measurement, which showed that the LCST of three kinds of copolymers increased largely after adding α‐CD. After UV irradiation on the solutions of copolymers and their inclusion complexes, the LCST of the copolymers increased slightly with the absence of α‐CD, while decreased largely with the presence of α‐CD. Furthermore, the LCST reverted to its originality after visible light irradiation. This change of LCST could be reversibly controlled by UV and visible light irradiation alternately. In particular, in the copolymer of PAPA and DMAM, the reversible water solubility of the inclusion complexes could be triggered by alternating UV and visible light irradiation.     

Improved electrochemical performance of nano-crystalline Li2FeSiO4/C cathode material prepared by the optimization of sintering temperature

Li₂FeSiO₄/C cathode materials have been prepared using the conventional solid-state method by varying the sintering temperature (650 °C, 700 °C and 750 °C), and the structure and electrochemical performance of Li₂FeSiO₄/C materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge tests, respectively. The results show that Li₂FeSiO₄ nano-crystals with a diameter of about 6–8 nm are inbedded in the amorphous carbon, and the Li₂FeSiO₄/C material obtained at 700 °C exhibits an initial discharge capacity of 195 mA?h g^?1 at 1/16 C in the potential range of 1.5–4.8 V. The excellent electrochemical performance of Li₂FeSiO₄/C attributes to the improvement of conductivity and reduction of impurity by the optimization of the sintering temperature.     

Improved Photovoltaic Performance of MEH-PPV/PCBM Solar Cells via Incorporation of Si Nanocrystals

We have studied the effect of silicon nanocrystals （SiNCs） as a third component on performance of organic bulk heterojunction solar cells composed of poly[2-methoxy,5-（2＇-ethylhexyloxy）-l,4-phenylene vinylene] （MEH- PPV）：[6,6]-phenyI-C61-butyric acid methyl ester （PCBM） blend film. By adding suitable amounts of SiNCs into MEH-PPV：PCBM blend, the device performance such as external quantum efficiency, short circuit current density （Js（）, and power conversion efficiency （PCE） improved. Incorporation of 2.5% SiNCs in the blend led to 13.6% improvement of Jsc, which in turn resulted in 18% improvement of PCE up to 2.28%. The improved performance was mainly due to the improvements both in the charge generation from the interface of MEH-PPV/SiNCs and the charge collection at the cathode.     

A rapid and convenient method for preparative separation of three indissolvable polyphenols from Euphorbia pekinensis by the flexible application of solvent extraction combined with counter‐current chromatography

A rapid and convenient method was established to preparatively isolate the three ellagic acid types of compounds, which were the main polyphenols in Euphorbia pekinensis, by flexibly applying solvent extraction combined with counter‐current chromatography (CCC). The total extract (extracted using 95% ethanol) of E. pekinensis was pretreated by two simple steps before CCC isolation, following the procedure: the total extract was extracted by classical solvent extraction using petroleum ether and ethyl acetate, respectively, and then the ethyl acetate extract was suspended using 95% ethanol, after being allowed to stand overnight, the sediment was obtained. Partial sediment (100 mg) was then directly separated by CCC with a two‐phase solvent system composed of chloroform‐95% ethanol‐water‐85% formic acid (50:50:50:5, v/v/v/v). About 22 mg of 3,3′‐dimethoxy ellagic acid (1), 12 mg of 3,3′‐di‐O‐methyl‐4‐O‐(β‐d ‐xylopyranosyl)ellagic acid (2), and 35 mg of ellagic acid (3) with purities of 96.0, 95.2, and 95.4% were obtained respectively in one step within 4 h. After being purified by washing with methanol, the purities of the three compounds obtained were all above 98%. The purities were determined by HPLC and their chemical structures were further identified by ¹H and ¹³C NMR spectroscopy. The recoveries were calculated as 84.6, 85.7, and 89.5%, respectively. The result demonstrated that the present isolation method was rapid, economical and efficient for the preparative separation of polyphenols from E. pekinensis.     

Amperometric nonenzymatic determination of glucose based on a glassy carbon electrode modified with nickel(II) oxides and graphene

We have developed a stable and sensitive nonenzymatic glucose sensor by modifying a glassy carbon electrode (GCE) with a composite incorporating nickel(II) oxides and reduced graphene. The oxides were generated by directly electrodepositing nickel on the GCE with a graphene modifier using a multi-potential pulse process, and then oxidizing nickel to nickel(II) oxides by potential cycling. In comparison to the conventional nickel(II) oxides-modified GCE, this new nickel(II) oxides-graphene modified GCE (NiO-GR/GCE) has an about 1.5 times larger current response toward the nonenzymatic oxidation of glucose in alkaline media. The response to glucose is linear in the 20 μM to 4.5 mM concentration range. The limit of detection is 5 μM (at a S/N of 3), and the response time is very short (<3 s). Other beneficial features include selectivity, reproducibility and stability. A comparison was performed on the determination of glucose in commercial red wines by high-performance liquid chromatography (HPLC) and revealed the promising aspects of this sensor with respect to the determination of glucose in real samples.

Synthesis of oxazole and furan derivatives via Rh2(OAc)4-catalyzed C≡X bond insertion of cyclic 2-diazo-1,3-diketones with nitriles and arylacetylenes

Abstract

A convenient and efficient procedure for the synthesis of 2-substituted-6,7-dihydrobenzo[d]oxazol-4(5H)-ones and 2-aryl-6,7-dihydrobenzofuran-4(5H)-ones through a Rh₂(OAc)₄-catalyzed C≡X (X?=?N, C) insertion of cyclic 2-diazo-1,3-diketones with nitriles and aromatic alkynes has been developed. This reaction uses readily available starting materials and stable cyclic 2-diazo-1,3-diketone compounds, with desired products formed in good to high yields. A tentative mechanism involving a C≡X bond insertion and 1,5-dipolar electrocyclization/ring opening and cyclization sequence for this reaction is proposed.     

Influence of clay on the morphology and phase separation behavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends

The effect of clay on the morphology and phase-separation behavior of poly(methyl methacrylate)/poly(styreneco-acrylonitrile)(PMMA/SAN) blends and the variation of clay dispersion have been investigated. With the evolution of phase separation in PMMA/SAN, most of the clays are first located at the boundaries between PMMA and SAN, and then gradually move to the PMMA-rich domain, owing to the affinity of clay to PMMA. The introduction of clay causes the increase of binodal and spinodal temperatures of PMMA/SAN and enlarges their metastable region, indicating the phase stabilizing effect of clay on the matrix. But the influence of clay on the cloud points obviously depends on the composition of PMMA/SAN. The selective adsorption of PMMA on the clay results in the difference between the composition of surface layer and that of polymer matrix. Hence, the clay plays the role of an agent changing the conditions of phase structure formation.