高分子Langmuir-Blodgett膜的研究进展

利用Langmuir-Blodgett(LB)膜技术能够使薄膜中聚合物分子链获得高度有序的排列与组装,并使沉积后的膜具备可控的特殊结构以及不同寻常的物理化学性质.高分子LB膜可用于制造非线性光学材料、光电子器件、传感器单元、电极修饰膜,也可作为研究催化反应、电子转移、仿生模拟的理想模型.本文评述了芳杂环类合成高分子(聚酰亚胺、聚噻吩、聚乙烯基咔唑和聚苯胺)与几种天然高分子(木质素、纤维素、壳聚糖和蛋白质)的LB膜最近的研究进展,并详细讨论了高分子LB膜的制备、结构与表征,指出了这两类高分子LB膜的研究重点,并对该两类高分子LB膜潜在的应用进行了展望.     

天然高分子用于油田堵水调剖的研究进展

从改性天然高分子材料出发,对各类天然高分子材料,如淀粉、纤维素、壳聚糖、硬葡聚糖、瓜胶、黄胞胶等作为油田堵水调剖剂的研究进展作了综述,并对天然高分子材料作为堵剂存在的问题及发展趋势进行了阐述。     

玉米醇溶蛋白高分子材料的制备与应用进展

作为一种天然高分子,玉米醇溶蛋白(Zein)具有疏水性、可降解性、抗菌性等特点。本文在介绍Zein结构、组成及性质的基础上,首先介绍了Zein的提取与脱色方法;然后,总结了通过小分子与高分子改性制备Zein基高分子材料的方法;最后,综述了基于Zein的高分子材料在食品、生物医药、纤维、粘合剂以及其他行业的应用研究进展。作为一类生物相容与生物可降解的天然高分子材料,Zein基材料在药物载体、食品包装、粘合剂等领域将具有更广泛的发展前景。     

无机材料/天然高分子复合微球的制备研究进展

微球是一种新型药物载体,具有很大的开发与应用潜力.天然高分子具有良好的生物相容性、可降解性,易在生物体内分散,可制备成微球.无机材料(主要为无机矿物)力学性能优良,且价廉易得.通过天然高分子与无机材料两者耦合杂化作用,可优势互补、协同增效,进而产生许多优异的理化性能.使用无机材料改性天然高分子,通过乳化交联法、溶液混合法、原位合成法、挤出法等多种方法可制备得到无机材料/天然高分子复合微球.将无机材料/天然高分子复合微球应用于药物传递系统中,缓释效果明显,安全无毒害,且载体材料价格相对低廉,对于开发新型药物载体具有一定的意义.本文综述了近年无机材料/天然高分子复合微球的制备、载药与释药性能的相关研究,分析了常用制备方法的利弊,展望了复合微球的发展方向.     

废弃天然高分子基功能材料

从废弃高分子角度对废弃生物质的高附加值再利用进行综述,阐述了废弃生物质中天然高分子的类型以及废弃生物质中包含的大量天然高分子具有官能团丰富、可降解、生物相容、无毒无害等优异的性能,归纳了废弃生物质的传统处理方法及作为材料使用的再利用途径,介绍了废弃天然高分子用作复合材料、吸附材料、载体材料、能源材料、医用高分子材料、智能高分子材料等的研究进展,并对废弃天然高分子的资源化利用进行了展望。     

高分子时代的天然高分子

本文从资源利用的战略角度讨论了发展及加强天然高分子研究的重要性。以几个天然高分子为例讨论了它们的研究动向及进展。与合成高分子相比，指出了天然高分子研究中存在的问题。文中对我国学者在这一领域中所作的卓越贡献做了简要介绍。     

天然高分子细胞培养基质的研究进展

天然高分子材料如壳聚糖、丝素蛋白和胶原蛋白等具有异体抗原性弱、生物相容性好、可生物降解且能促进细胞粘附、生长和增殖等优点。同人工合成高分子材料相比,天然高分子几乎不含有机溶剂和引发剂等物质,生物安全性高,是细胞培养基质的首选原材料。近年来,随着生物科技的发展,其新功能也不断被发现并受到学术界的广泛重视。本文综述了天然多糖类和天然蛋白质类高分子材料的理化性质及在细胞培养基质领域中的应用,对目前所存在的一些问题进行了描述并预测其发展动向。     

天然高分子药物微球载体材料的研究进展

综述了国内外在天然高分子药物微球载体材料研究及应用中的进展状况,主要从天然高分子药物微球载体材料的分类、微球的制备方法及特点、载药微球的给药途径和应用等进行概括,并对目前所存在的问题进行了描述。     

天然植物抗氧化活性成分的提取及检测方法

天然抗氧化剂能有效地清除自由基从而保护机体健康,从自然界中寻求高效、廉价、低毒的天然抗氧化剂成为目前抗氧化剂发展的一个必然趋势。总结了几种天然植物抗氧化活性成分的提取和测定方法的研究进展,为天然植物抗氧化活性成分的开发利用提供参考。     

聚甲基乙撑碳酸酯/天然高分子复合材料研究进展

聚甲基乙撑碳酸酯(PPC)是一种新型热塑性脂肪族聚碳酸酯,具有良好的生物降解性、高阻隔性和生物相容性等优点,但其热性能和力学性能较差,通过物理和化学方法改性是提高其性能的重要研究方向之一。本文综述了近年来采用淀粉、纤维素和甲壳素等天然高分子对PPC的改性研究,尤其是天然高分子含量和预处理方法等对复合材料性能的影响,并对PPC/天然高分子复合材料的发展作了总结和展望。     

Gamma radiation effects on an amine antioxidant added in an ethylene-propylene copolymer

The aim of this work was to compare the gamma radiation induced effects on samples of an ethylene-propylene copolymer antioxidant free with samples loaded with an antioxidant characterised by the presence of an -NH functional group. The employed techniques were Electron Spin Resonance spectroscopy (ESR) and High Performance Liquid Chromatography (HPLC). Stable radicals R---NO° due to the interaction of free radicals produced in the irradiated polymer with the antioxidant have been observed by ESR at room temperature. The time evolution of the ESR signals following the irradiation was examined at different doses. The amount of antioxidant not involved in the oxidation reactions has been determined using HPLC.     

A Concise Review of Current In Vitro Chemical and Cell-Based Antioxidant Assay Methods

Antioxidants remain interesting molecules of choice for suppression of the toxic effects of free radicals in foods and human systems. The current practice involves the use of mainly synthetic molecules as potent antioxidant agents. However, due to the potential negative impact on human health, there is an intensive effort within the research community to develop natural alternatives with similar antioxidant efficacy but without the negative side effects of synthetic molecules. Still, the successful development of new molecules depends on the use of reliable chemical or cell culture assays to screen antioxidant properties. Chemical antioxidant assays include the determination of scavenging ability against free radicals such as DPPH, superoxide anion radicals, hydroxyl radicals, hydrogen peroxide, and nitric oxide. Other antioxidant tests include the ability of compounds to bind and sequester prooxidant metal cations, reduce ferric iron, and attenuate the rate of lipid oxidation. Ex vivo tests utilize cell cultures to confirm entry of the molecules into cells and the ability to quench synthetic intracellular free radicals or to stimulate the increased biosynthesis of endogenous antioxidants. In order to assist researchers in their choice of antioxidant evaluation methods, this review presents background scientific information on some of the most commonly used antioxidant assays with a comparative discussion of the relevance of published literature data to food science and human nutrition applications.     

Free Radicals as a Double-Edged Sword: The Cancer Preventive and Therapeutic Roles of Curcumin

Free radicals, generally composed of reactive oxygen species (ROS) and reactive nitrogen species (RNS), are generated in the body by various endogenous and exogenous systems. The overproduction of free radicals is known to cause several chronic diseases including cancer. However, increased production of free radicals by chemotherapeutic drugs is also associated with apoptosis in cancer cells, indicating the dual nature of free radicals. Among various natural compounds, curcumin manifests as an antioxidant in normal cells that helps in the prevention of carcinogenesis. It also acts as a prooxidant in cancer cells and is associated with inducing apoptosis. Curcumin quenches free radicals, induces antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), and upregulates antioxidative protein markers–Nrf2 and HO-1 that lead to the suppression of cellular oxidative stress. In cancer cells, curcumin aggressively increases ROS that results in DNA damage and subsequently cancer cell death. It also sensitizes drug-resistant cancer cells and increases the anticancer effects of chemotherapeutic drugs. Thus, curcumin shows beneficial effects in prevention, treatment and chemosensitization of cancer cells. In this review, we will discuss the dual role of free radicals as well as the chemopreventive and chemotherapeutic effects of curcumin and its analogues against cancer.     

Elution–extrusion counter-current chromatographic separation and theoretical mechanism of antioxidant from Robinia pseudoacacia flower

Robinia pseudoacacia flowers have attracted much attention because of numerous bioactivities. In this study, its extract showed the potential scavenging ability for 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) and 1,1-diphenyl-2-picrylhydrazyl free radicals. Under the guidance of antioxidant activity, the antioxidant extract was enriched by liquid-liquid extraction. The partition coefficients of the two main components in antioxidant extracts differed greatly, so in this study, elution-extrusion counter-current chromatography with the solvent system of n-hexane-ethyl acetate-methanol-water (2.5:5:2.5:5, v/v) was used to enhance the separation efficiency, and the two main components were successfully obtained. Among them, kaempferol showed strong antioxidant activity, which can be responsible for the activity of the extract. In order to deeply understand the antioxidant mechanism of kaempferol, the thermodynamics, frontier molecular orbital, and kinetics of scavenging free radicals were investigated by density functional theory. The results showed that 4′-OH in kaempferol was the most active group, which can scavenge free radicals by hydrogen atom transfer in non-polar solvents and activate 3-OH to generate double hydrogen atom transfer in the gas phase. But in polar solvents, it was more inclined to clear radicals through single electron transfer and proton transfer. The kinetic result showed that kaempferol needed 9.17 kcal/mol of activation energy to scavenge free radicals.     

光电化学技术应用于抗氧化分析的研究进展

在新陈代谢过程中, 机体会产生大量以自由基为主要形式的氧化活性物质, 而抗氧化剂可以通过电子转移的方式捕获并中和自由基, 从而有效抵御自由基引起的细胞损害, 以保障和维护人体健康. 食品作为人体外源性抗氧化剂的重要来源可以有效补充因体内代谢及体液排出而损失的抗氧化物质, 因此对食品中抗氧化物质消除自由基的能力即抗氧化能力的测定和评价具有重要意义. 光电化学技术作为一种简单快捷、 低成本、 低背景且高灵敏度的测定方法, 能够有效克服光学法、 色谱法和电化学法等传统测试手段在抗氧化容量分析中的不足. 本文综述了基于半导体及其复合材料的光电化学传感平台的构建及食品体系抗氧化容量分析的研究进展, 评论了多种检测体系的特点并对其研究前景进行了展望.     

Antioxidant and Protective Effects of <Emphasis Type="Italic">Schinus terebinthifolius</Emphasis> Raddi Against Doxorubicin-Induced Toxicity

Doxorubicin is an anticancer drug whose toxic effects on non-cancer cells are associated with increased oxidative stress. This study investigated the chemical composition, antioxidant activity of the methanolic extract of Schinus terebinthifolius Raddi leaves (MESL) as well as effects against doxorubicin-induced toxicity in human erythrocytes, K562 human erythroleukemia cells, and mouse hearts. The chemical composition indicated the presence of phenolic compounds, flavonoids, tannins, and ascorbic acid. MESL showed antioxidant activity by scavenging free radicals and inhibiting hemolysis and lipid peroxidation in human erythrocytes incubated with an oxidizing agent, and was able to increase the enzymatic activity of superoxide dismutase and glutathione peroxidase in human erythrocytes, without influencing the activity of enzyme catalase. The increase of oxidative hemolysis and malondialdehyde levels in erythrocytes incubated with doxorubicin was reduced by treatment with MESL. The cytotoxic activity of doxorubicin in erythroleukemia cells treated with MESL was unmodified. Additionally, the extract protected mice against the doxorubicin-induced cardiotoxicity. In conclusion, the MESL exhibits antioxidant activity, reducing doxorubicin-induced oxidative stress without changing the anticancer action of the drug, and protects against doxorubicin-induced cardiotoxicity. Hence, these findings suggest that these effects are via anti-oxidative by inhibiting free radicals, decreased oxidative stress, and increased antioxidant enzyme activity.     

Functionalized graphene quantum dots loaded with free radicals combined with liquid chromatography and tandem mass spectrometry to screen radical scavenging natural antioxidants from Licorice and Scutellariae

A novel screening method was developed for the detection and identification of radical scavenging natural antioxidants based on a free radical reaction combined with liquid chromatography with tandem mass spectrometry. Functionalized graphene quantum dots were prepared for loading free radicals in the complex screening system. The detection was performed with and without a preliminary exposure of the samples to specific free radicals on the functionalized graphene quantum dots, which can facilitate charge transfer between free radicals and antioxidants. The difference in chromatographic peak areas was used to identify potential antioxidants. This is a novel approach to simultaneously evaluate the antioxidant power of a component versus a free radical, and to identify it in a vegetal matrix. The structures of the antioxidants in the samples were identified using tandem mass spectrometry and comparison with standards. Fourteen compounds were found to possess potential antioxidant activity, and their free radical scavenging capacities were investigated. The order of scavenging capacity of 14 compounds was compared according to their free radical scavenging rate. 4′,5,6,7‐Tetrahydroxyflavone (radical scavenging rate: 0.05253 mL mg^?1 s^?1) showed the strongest capability for scavenging free radicals.     

Purification and Identification of Novel Antioxidant Peptides from Enzymatically Hydrolysed Samia ricini Pupae

The emergence of excessive free radicals leads to the destruction of various systems within the body. These free radicals also affect nutritional values, color, taste, and emit an odor akin to rancid food. Most food industries use synthetic antioxidants, such as BHT (butylated hydroxytoluene) or BHA (butylated hydroxy anisole). However, high doses of these can be harmful to our health. Therefore, an antioxidant compounds, such as bioactive peptides from edible animals or plants, have emerged to be a very promising alternative as they reduce potential side effects. This study focused on the purification and identification of antioxidant peptides from protein hydrolysates of wild silkworm pupae (Samia ricini). Antioxidant peptides were purified from the hydrolysate by ultrafiltration and RP-HPLC. The results showed that protein hydrolysate from S. ricini pupae by trypsin with a molecular weight lower than 3 kDa and highly hydrophobic property, exhibited strong DPPH radical scavenging activity and chelating activity. Further identification of peptides from the fraction with the highest antioxidant activity was carried out using LC-MS/MS. Three novel peptides, i.e., Met-Ley-Ile-Ile-Ile-Met-Arg, Leu-Asn-Lys-Asp-Leu-Met-Arg, and Glu-Asn-Ile-Ile-Leu-Phe-Arg, were identified. The results of this study indicated that the protein hydrolysate from S. ricini pupae possessed potent biological activity, and the novel antioxidant peptides could be utilized to develop health-related antioxidants in food industry.     

Analysis of botanicals and dietary supplements for antioxidant capacity: a review

Free radicals and other reactive species are considered to be important causative factors in the development of diseases of aging such as cancer and cardiovascular diseases. This relationship has led to considerable interest in assessing the antioxidant capacity of foods and botanicals and other nutritional antioxidant supplements. The use of the oxygen radical absorbance capacity (ORAC) assay as a tool for antioxidant assessment is described and proposed as a method for comparing botanical sources and for standardizing nutritional supplements. The free radical or oxidant source is important and direct comparisons cannot be made between procedures that use different sources. The ORAC procedure uses 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical source, which is relevant to biological systems because the peroxyl radical is the most abundant free radical. Other oxidant sources (hydroxyl radical and Cu++) can also be used to characterize antioxidants in botanicals. Phenolics or polyphenolics are responsible for most of the antioxidant capacity in fruits, vegetables, and most botanical antioxidant supplements. Although little is known about the absorption and metabolism of these components, improvement in the in vivo antioxidant status has been observed in human subjects following consumption of antioxidant botanicals. The ORAC method provides a basis from which to establish appropriate dietary intakes that might impact health outcomes.