亚硝酰自由基及其选择性氧化多糖类物质研究进展

亚硝酰自由基能选择性氧化天然多糖类高分子，如纤维素，淀粉，甲壳质，壳聚糖等，从而为制备这些天然高分子的氧化产物或进一步制备氧化产物的衍生物，对环境友好高分子，可生物降解高分子，医用高分子的开发具有较大的应用前景。本文在简介亚硝酰自由的基础上，对其选择性氧化多糖类物质的研究进展作了综述。     

甲壳素及其衍生物——甲壳胺的生产和应用

明胶在加工与应用中常常使用某些天然高分子材料以改进其性能,使明胶制品适应应用的要求,这些天然高分子材料大多数属于多糖类。本刊首先介绍甲壳素及其衍生物甲壳胺的生产和应用,今后还将陆续介绍其他多糖类天然高分子化合物,以支持读者们开发更多新型的明胶制品。     

天然高分子材料的开发及应用

天然高分子材料经过改性可加工成为人类急需的可生物降解的人工高分子材料，南京化工大学利用农作物秸杆经蒸爆处理制备无胶复合板技术已经开发成功，应用前景良好。     

天然高分子絮凝剂处理重金属废水研究的进展

重金属污染物不能自然降解，给人类健康和生态环境造成了严重威胁，化学絮凝法已被广泛应用于重金属废水的处理。天然高分子絮凝剂具有无毒、可生物降解等优点，其在处理重金属废水方面有着极大的优势。综述了淀粉、壳聚糖、植物胶、海藻酸钠、纤维素等多糖类天然高分子絮凝剂在重金属废水处理中的应用进展。     

生物降解高分子材料研究进展

介绍了生物降解高分子材料的概念和分类,并结合具体实例详细论述了目前国内外在天然、微生物合成、化学合成和掺混型等四类生物降解高分子材料方面的研究方向及最新研究进展。     

基于天然高分子的可再生光刻材料及其光刻机理的研究进展

基于天然高分子的新型光刻材料与石油原料的传统光刻材料相比,不仅保留了高分辨率的光刻性能,还具有绿色可再生和无毒显影等优点。本文综述了天然高分子光刻材料中的蛋白类光刻材料和多糖类光刻材料,系统的总结了各种天然高分子光刻材料的优缺点。通过对不同材料光刻机理的深入研究,得出蛋白质光刻材料的光刻机理主要依靠辐射改变蛋白结构,使其溶解度在显影液中发生改变实现光刻;而天然多糖类光刻材料则主要依赖引入光响应基团实现光刻。最后本文对基于天然高分子的可再生光刻材料的现存问题进行了分析并对发展前景做出了展望。     

基于天然高分子的可再生光刻材料的研究进展

与传统基于石油原料的光刻材料相比,基于天然高分子的可再生光刻材料不仅保留了高分辨率的光刻性能,还具有绿色可再生和无毒显影等优点.重点综述了天然高分子光刻材料中的蛋白类光刻材料和多糖类光刻材料,总结了各种天然高分子光刻材料的优缺点.通过对不同材料光刻机理的深入研究,总结出蛋白质光刻材料的光刻机理主要依靠辐射改变蛋白结构,使其溶解度在显影液中发生改变实现光刻;而天然多糖类光刻材料则主要依赖引入光响应基团实现光刻.最后对基于天然高分子的可再生光刻材料的现存问题进行了分析并对发展前景作出了展望.     

全生物降解高分子材料的发展现状

生物降解高分子材料因医药、医学、环境等方面的需求而迅速发展起来,在近几十年,世界先进国家非常重视该领域的研究和开发工作,并取得一些重要进展。在简要介绍生物降解高分子材料的降解过程后,着重对全生物降解高分子材料的发展现状作了综述,其中包括化学合成高分子和天然高分子的研究和开发,同时对生物降解高分子材料存在的问题及其将来发展趋势等方面进行了讨论。     

卡拉胶的制备及应用

明胶在加工与应用中常常使用某些天然高分子材料以改进其性能,使明胶制品更适应应用的要求,有时也可以用这些材料来完全替代明胶,这些天然高分子材料大多数属于多糖类。本刊第21卷第1期第34～37页首先介绍了“甲壳素及其衍生物——甲壳胺的生产和应用”,这里接着介绍一种海产胶——卡拉胶,供读者们在开发明胶制品及各类新型产品时参考。     

天然多糖类物质在组织工程中的应用

天然多糖类物质作为一类资源丰富性能优异的天然高分子生物材料,具有无毒、无味、无免疫原等特点,且具有良好的生物相容性和生物可降解性,其分解产物对人体安全无害,从而被广泛的应用于生物材料领域。近年来,天然多糖类物质及其衍生物作为天然高分子组织工程支架,越来越受到重视,并取得一定研究进展。文章综述了天然多糖类物质及其衍生物作为新型生物材料在不同器官(皮肤、肝脏、骨、神经、牙周、软骨等)组织工程中的研究现状。     

Role of polyacrylate starch copolymer in water sorption

Water sorbence by saponified polyacrylonitrile-grafted polysaccharides was studied in relation to practical end uses. Graft copolymers prepared from wheat flour, corn flour, cotton wool, and rayon fibers swelled to a gel, exhibiting a 10- to 20-fold increase in sorbency over the starting materials. A further enhanced water capacity was obtained when homopolymer was not removed. Soaking the wheat flour copolymer in salts or dilute mineral acid nullified the enhanced water sorbence, which could be reversible restored by neutralization of acrylic acid functions with alkali. Swelling the copolymer in aqueous D-glucose did not impair its water capacity. The mechanism of swelling to a gel appears to involve electrolyte osmotic pressure generated by a Donnan equilibrium. Grafting starch elevated its heat of water vaporization above that of pure water, and increased its capacity to absorb water from ethanol-water vapor at 40° above that of native starch. At higher temperatures, however, the dehydrating capacity decreased to that of native flour.     

Main properties and current applications of some polysaccharides as biomaterials

This review concerns the applications of some polysaccharides in the domain of biomaterials and bioactive polymers. Natural polysaccharides from different sources have been studied for a long time, and their main properties are summarized in this paper; some of their derivatives obtained by chemical modification are also described. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan, hyaluronan and alginates. Alginates are well known for their property of forming a physical gel in the presence of divalent counterions (Ca, Ba, Sr) whereas carrageenans form a thermoreversible gel; these seaweed polysaccharides are mainly used to encapsulate different materials (cells, bacteria, fungi). Other promising systems are the electrostatic complexes formed when an anionic polysaccharide is mixed with a cationic polysaccharide (e.g. alginate/chitosan or hyaluronan/chitosan). An important development of the applications of polysaccharides can be predicted for the next few years in relation to their intrinsic properties such as biocompatibility and biodegradability in the human body for some of them; they are also renewable and have interesting physical properties (film‐forming, gelling and thickening properties). In addition, they are easily processed in different forms such as beads, films, capsules and fibres. Copyright © 2007 Society of Chemical Industry     

Recent Advances in Artificially Sulfated Polysaccharides for Applications in Cell Growth and Differentiation,Drug Delivery,and Tissue Engineering

Artificially sulfated polysaccharides, as the mimetics of native heparin and heparan sulfate, are important bioactive compounds, since they show great potential for tuning crucial biological activities within living organisms. Herein, we summarize progress in the development of artificially sulfated polysaccharides, such as cellulose sulfate, chitosan sulfate, and other sulfated polysaccharides, with a particular focus on the fields of biomedical and bioengineering applications in the past ten years. Their effects on cell growth and differentiation, but also as building blocks for drug carriers and medical implants, are emphasized.     

Encapsulation and delivery of bioactive compounds using spray and freeze-drying techniques: A review

Abstract

There are various bioactive components exist in plants, fruits, and vegetable origins that have many beneficial health effects (mainly antioxidant). However, they suffer from low-stability against the environmental condition. Thus, the encapsulation approach emerged to decrease their sensitivity and present a target delivery system. Generally, native carrier agents (polysaccharides and proteins) are being applied to embed the core materials. Accordingly, many encapsulation methods have been developed to protect vulnerable components by these carriers. Spray and freeze-drying are common encapsulation methods with the ability of powder production. Both feed emulsion production and drying process factors substantially influence the core embedded within the carrier agents. Spray-drying is well-known to higher applicable and scalable encapsulation procedure in the food and pharmaceutical industries. It is predominantly related to its lower process costs. Nevertheless, its application is limited for more sensitive bioactive compounds due to hot-air drying exertion. In contrast, freeze-drying has been mostly used for thermo-sensitive ingredients. Its application is restricted by economic drawbacks for which long process time (24–48?h) is required. However, freeze-drying is adequately taken into an advantage in the encapsulation of therapeutic compounds since high-added value products will be produced so that bioactive compounds with higher biological activity are needed.     

Physically crosslinked hydrogels from polysaccharides prepared by freeze–thaw technique

Natural polysaccharides are abundant, inexpensive, renewable, modifiable and have biodegradable and biocompatible characteristics. Polysaccharides offer a very promising source for materials of tomorrow. This review addresses recent progress in polysaccharide-based cryogels, one kind of novel physical hydrogels prepared by freeze–thaw technique under mild conditions and in the absence of organic solvents and toxically crosslinking agents. Polysaccharides used to fabricate physical cryogels here are, hyaluronan, carboxymethylated curdlan, carboxymethylated cellulose, xanthan, β-glucan, locust bean gum, starch (amylose, amylopectin and their mixtures), maltodextrins and agarose. Composite cryogels of based on polysaccharides and polyvinyl alcohol are also introduced. Various physically crosslinked cryogels from polysaccharides with tunable structural, mechanical, biological properties as well as multiple applications are considered and the investigations of the formation mechanism for these cryogels are also addressed.     

Reproducible,biocompatible medical materials from biologically derived polysaccharides: Processing and Characterization

Natural polysaccharides like chitosan and dextran have garnered considerable interest in biomedical applications due to their biocompatibility, biodegradability, and nontoxicity. Nonetheless, the development of a reproducible class of medical devices from these materials is challenging and has had limited success. Chitosan and dextran are inherently variable and synthesis using these materials is prone to inconsistencies. In this study, we put forward a robust product development regimen that allows these natural materials to be developed into a reproducible class of biomaterials. First, an array of validated characterization methods (Proton Nuclear Magnetic Resonance, titrations, Ultraviolet spectroscopy, Size Exclusion Chromatography—Multi-Angle Light Scattering, Size Exclusion Chromatography—Refractive Index, and proprietary methods) were developed that allowed rigorous specifications to be set for unprocessed chitosan and dextran, chitosan and dextran intermediates, and chemically modified materials—acrylated chitosan (aCHN) and oxidized dextran (oDEX). Second, a robust and reproducible synthesis scheme involving various in-process controls was developed to chemically modify the unprocessed polysaccharides. Third, purification methods to remove byproducts and low-molecular-weight impurities for both aCHN and oDEX were developed. The study presents a viable strategy for converting variable, natural materials into a reproducible class of biomaterials that can be applied in various biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48454.     

Self-Limitation of Native Oxides Explained

Silicon is one of many materials whose surface will oxidize in ambient conditions. However it is one of few materials whose native oxide will self-limit its growth in a matter of hours at a thickness of ～2 nm. In this work, we show through the theory of repulsive van der Waals forces that this self-limitation is due, at least in part, to the interaction between the inherent material properties of a native silicon oxide film on silicon and oxidizing molecules. These molecules are not just hindered from even entering the system at all, but those that do enter the native oxide film are repelled away from the silicon – silicon oxide interface, preventing additional growth by oxidation. We also show how this repulsion is overcome by increasing ambient temperatures to subsequently increase the kinetic energy of the oxidizing molecules, calculated by the Boltzmann-Maxwell distribution, and allow oxidation to continue.     

藏药红景天多糖基抗菌可食膜的制备

以藏药红景天(RP)作为研究对象,以乙醇/硫酸铵双水相体系(EAS)作为活性提取试剂,以提取的红景天多糖作为天然绿色抑菌活性因子,以甘油(Gly)为增塑剂、明胶(Gel)为成膜剂、氯化钙为交联剂,采用斜面自然倾倒流延法,制备了一种新型的抗菌膜材料。以抗菌膜的抗拉强度、抑菌活性、水蒸气透过率,包肉降解特性作为膜材料的评价指标,考察了成膜材质的最佳添加量。抑菌实验结果表明,当红景天多糖加入量为6m L(WRP=14.6%)时,抗菌膜材料对金黄色葡萄球菌和大肠杆菌的最大抑制率分别为97.3%和88.6%。抗拉强度、水蒸气透过率以及包肉降解特性实验结果表明:当添加多糖6 mL、甘油1.5 g、明胶1.0 g、氯化钙0.8 g时制备的抗菌膜性能最好。     

Chemical synthesis of polysaccharides and polysaccharide mimetics

Polysaccharides are ubiquitous in nature, and play many critical roles in biology. As such, the synthesis of polysaccharides and of polymers mimicking the structure or function of polysaccharides is of keen interest in order to reveal structure-function relationships and to prepare biocompatible and biodegradable materials for research and commercial applications. Recent developments in polymerization methodologies are enabling the synthesis of polysaccharides and polysaccharide mimetics with a variety of structures and architectures. While there have been significant advances in overcoming the difficulties in controlling the regioselectivity and stereospecificity of glycosidic bond formation during polymerization, the development of efficient synthetic routes with general applicability to stereoregular and structurally complex polysaccharides remains a challenge. This review comprehensively describes the chemical polymerization methods to synthesize polysaccharides with different compositions and architectures (linear, branched, and hyperbranched) and the synthetic procedures to polysaccharide mimetics possessing, for example, amine linkages, amide linkages, and carbonate linkages. It begins with a discussion of the challenges and strategies for the synthesis of polysaccharides. We highlight the complexity observed in theses macromolecules due to the number and variety of stereo- and regio-types of glycosidic linkages present between monosaccharide residues. With regards to polysaccharide mimetics, we focus on polymers displaying important structural features present in natural polysaccharides, such as a rigid polymer backbone containing heterocyclic ring structures, short linkages with less than three atoms, as well as multiple hydroxyl groups. Both condensation polymerization and ring-opening polymerization are used to prepare linear polysaccharides, branched polysaccharides, hyperbranched polysaccharides, non-O-glycosidic linked polysaccharide mimetics, and pseudopolysaccharides. The review concludes with reflections and suggestions for future directions of investigation.     

冬凌草硒多糖的制备、表征及抗氧化活性分析

本研究以济源冬凌草多糖为原料，选用化学合成方法对多糖进行结构修饰。采用UV、FT-IR、SEM、TGA、HPLC等方法对冬凌草多糖以及硒多糖结构特征进行了表征；通过DPPH（1,1-二苯基-2-三硝基苯肼）自由基法、羟自由基法等4种方法对其抗氧化活性进行了探究。结果：制备的硒多糖中硒质量分数为1.35 mg/g。硒化修饰后，冬凌草多糖的基本骨架得到保留，单糖种类未发生改变，但其分解温度降低、稳定性下降，多糖形貌也发生明显变化，球状与条状形貌增多，片状形貌减少。此外，在体外抗氧化性实验中，当硒多糖质量浓度为1.6mg/mL时，对DPPH自由基、ABTS自由基、羟自由基清除率分别为68.68%、86.69%、45.12%，均强于冬凌草多糖。