甲壳素／壳聚糖的化学修饰

详述了甲壳素／壳聚糖的主要化学反应所得衍生物的一些性质和应用。     

天然高分子甲壳素／壳聚糖在生物和医药方面的应用

天然高分子甲壳素／壳聚糖在生物和医药方面的应用徐健，金鑫荣（上海华东理工大学化学系上海２００２３７）甲壳素又称甲壳质、几丁质、壳蛋白、蟹壳素、壳聚糖等，广泛存在于低等动物，特别是节肢动物（如昆虫、蜘蛛、甲壳类）的外壳，以及低等动物（如真菌、藻类、酵母...     

甲壳素和壳聚糖作为天然生物高分子材料的研究进展

甲壳素是自然界中含量仅次于纤维素的天然高分子,壳聚糖是甲壳素脱乙酰化后带有阳离子的多糖.壳聚糖中的自由氨基以及它的高结晶性,使得它能溶于酸,而不溶于碱和绝大数的有机溶剂.同时壳聚糖具有无毒性、无刺激性、良好的生物相容性、生物可溶解性, 以及高的电荷密度,因而被作为一种新型的天然生物材料得到广泛应用.文章介绍了甲壳素和壳聚糖的结构和性质,综述分析了甲壳素和壳聚糖在制备微球和作为支架材料中的应用, 并总结了甲壳素和壳聚糖在这两个方面存在的问题和发展前景.     

甲壳素和壳聚糖在离子液体中的溶解与改性

甲壳素及壳聚糖作为生物大分子材料难溶于诸多溶剂,从而限制了其应用和修饰改性。因此,研究与开发良好的溶剂体系具有重要意义。本文首先对甲壳素及壳聚糖在各种离子液体中的溶解性能和溶解机理进行了详细综述,其次概述了甲壳素与壳聚糖在离子液体介质中进行修饰的化学反应研究(如:水解作用、酰基化反应和接枝共聚反应等),最后提出离子液体作为一类可回收循环使用的良好溶解介质将会对甲壳素及壳聚糖的实际应用和修饰改性提供更好的媒介,并拓宽甲壳素及壳聚糖的研究与应用领域。     

甲壳素和壳聚糖在离子液体中的溶解、材料化以及衍生化

甲壳素和壳聚糖是可再生的大分子生物质资源.由于分子内和分子间的强烈氢键作用,甲壳素和壳聚糖不能溶解在水或常规有机溶剂中,这极大地限制了其在诸多领域中的应用.离子液体作为一种新型绿色溶剂,对甲壳素和壳聚糖具有优良的溶解作用.本文综述了离子液体对甲壳素和壳聚糖的溶解性能和溶解机理,概述了均相溶液体系中纤维、膜、凝胶等材料的制备以及酰化、接枝共聚、交联、降解、希夫碱化等多种衍生化反应,总结了离子液体在甲壳素和壳聚糖化学研究中面临的挑战并对其进行了展望.     

热塑性甲壳素衍生物N,O-苄基壳聚糖的合成及表征

天然高分子的热塑化一直引起人们的极大关注．由于存在大量的分子内和分子间氢键,一般天然高分子都不能加热塑化,从而限制了其应用．纤维素和淀粉的热塑化改性已有了许多研究．典型的热塑性纤维素衍生物有乙基纤维素、醋酸纤维素和经丙基纤维素等[1,2],有些纤维素衍生物还具有热致液晶性．淀粉的某些衍生物也已有热塑性[3]．在分子结构上,甲壳素／壳聚糖比纤维素或淀粉多了乙酰氨基和氨基,更易形成氢键,分子间作用力更强．迄今,国内外已报道了大量甲壳素／壳聚糖衍生物,但均无热塑性．我们曾合成具有热塑性的氰乙基经丙基壳聚糖,但熔点与分解温度之间只有27℃E4J．热塑性甲壳素的研究不仅为甲壳素的加工利用开辟了新途径,而且也将为热致性甲壳素液晶的研究奠定基础,从而进一步丰富和深化目前以纤维素衍生物为主的热致胆舀液晶研究[5,6]．为此,本文研究了一种新的热塑性甲壳素衍生物,并从结构上讨论了其具有热塑性的原因．     

蘑菇中甲壳素的提取及结构研究

以蘑菇为原料提取甲壳素,并制备壳聚糖。通过滴定法测定由蘑菇制备的壳聚糖的脱乙酰度,用乌氏黏度计测定了比浓黏度,并研究了制备工艺中加热温度和碱处理时间对它们的影响,计算了其产率;对以蘑菇为原料制取的甲壳素、壳聚糖的结构通过红外光谱进行表征。结果表明,在碱处理时间为24h、加热温度为100℃的条件下有较高的脱乙酰度;比浓黏度随着碱处理时间的延长、加热温度的增加都呈下降的趋势;壳聚糖产率为1．69％。制取的甲壳素、壳聚糖的红外光谱图表明,甲壳素在蘑菇中主要是以α-构型存在,α-构型甲壳素在浓碱中经过脱乙酰后生成β-构型的壳聚糖。     

甲壳素与壳聚糖的化学改性及应用

生物高分子甲壳素是自然界最丰富的氨基多糖,其最重要的衍生物壳聚糖是近年来国内外学术界和工业界广泛研究的对象。甲壳素和壳聚糖具有广阔的应用前景,通过适当、有效的结构修饰,可以充分挖掘它们的潜力。本文重点介绍甲壳素和壳聚糖的化学改性及其在相关医药学领域的应用。     

羧甲基甲壳素水溶液等电点的测定

羧甲基甲壳素水溶液等电点的测定陈炳稔汤又文陈文森（华南师范大学化学系广州５１０６３１）自然界每年生物合成的甲壳素估计数十亿吨，是仅次于纤维素的天然高分子化合物，壳聚糖是由甲壳素经过脱乙酰化反应而得到的一种生物高分子［１，２］。与甲壳素相比，壳聚糖的溶...     

壳聚糖的结构特性及其衍生物的应用

壳聚糖由甲壳素经脱乙酰基而得,又称为可溶性甲壳素。壳聚糖的结构特征使其具有了独特的物理化学性质和生物活性。本文介绍了壳聚糖的结构特性、重要的化学性质及衍生物的应用。     

甲壳素/壳聚糖在环境治理上的应用

天然高分子化合物甲壳素、壳聚糖具有原料丰富、无毒、易于生物降解等优点,国内外众多学者对它的开发应用展开研究,本文综述了甲壳素、壳聚糖及其衍生物对环境污染物的去除,介绍了它在环境治理尤其是废水处理中的研究和应用情况。     

Effects of Chitin/Chitosan and Their Oligomers/Monomers on Migrations of Macrophages

The effects of chitin/chitosan and their oligomers/monomers on the migrations of mouse peritoneal macrophage (PEM) and the rat macrophage cell line (rMp) were evaluated in vitro. In direct migratory assay using the blind well chamber method, the migratory activity of PEM was enhanced significantly by chitin and chitosan oligomers (NACOS and COS, respectively), but reduced by chitin, chitosan, and the chitosan monomer (GlcN). The migratory activity of rMp was increased significantly by chitin, chitosan, and the polymers, NACOS and GlcN.     

Poly(epsilon-caprolactone)/chitin and poly(epsilon-caprolactone)/chitosan blend films with compositional gradients: fabrication and their biodegradability

Poly(epsilon-caprolactone) (PCL)/chitin and PCL/chitosan blend films with compositional gradients were successfully fabricated by a dissolution/diffusion method; that is, repeatedly pouring the PCL/chitin (or PCL/chitosan) blend solutions, with variable composition, onto polysaccharide layers. The compositional gradient structure in the resulting films was characterized by polarized optic microscopy, ATR-FT-IR and trans-FT-IR microscopic spectroscopy. Enzymatic degradability of the PCL/chitin and PCL/chitosan blend films with compositional gradients in the presence of lysozyme was compared with those of homogeneous films and two-layer films. It was found that the degradation rate of PCL/chitin blend films with a compositional gradient was far lower than that of the neat chitin film, whereas the degradation rate of PCL/chitosan blend films with a compositional gradient was close to that of the neat chitosan film. The suppression of the chitosan crystallization, which accelerates the enzymatic degradation, at the surface of PCL/chitosan films with a compositional gradient was much more severe than that for PCL/chitin films with a compositional gradient.     

Water sorption on and water diffusion in chitin and chitosan

The kinetics of the sorption of water vapor on powders of crab-shell chitin and chitosan are studied via the methods of static sorption, thermography, and X-ray structural analysis. Sorption isotherms are obtained in the range of humidity from 10 to 95%. S-Shaped water-sorption isotherms observed for all chitin and chitosan samples are approximated via superpositioning of Langmuir and Flory-Huggins isotherms. The water-polysaccharide interaction parameters and the maximum sorption capacities of water located in chitin and chitosan are determined. The cluster integral is calculated, and the moisture values corresponding to water-cluster formation are determined. The water-diffusion coefficients are determined, and the effective activation energies of water diffusion are estimated: 70 kJ/mol in chitosan and 60 kJ/mol in chitin. The data on the concentration dependences of the coefficients of diffusion of water in the powdered chitin and chitosan are summarized.     

Comparative adsorption studies of indigo carmine dye on chitin and chitosan

The adsorption of indigo carmine dye onto chitin and chitosan from aqueous solutions was followed in a batch system. The ability of these materials to adsorb indigo carmine dye from aqueous solution was followed through a series of adsorption isotherms adjusted to a modified Langmuir equation. The maximum number of moles adsorbed was 1.24 +/- 0.16 x 10(-5) and 1.54 +/- 0.03 x 10(-4) mol g(-1) for chitin and chitosan, respectively. The same interactions were calorimetrically followed and the thermodynamic data showed exothermic enthalpic values of -40.12 +/- 3.52 and -29.25 +/- 1.93 kJ mol(-1) for chitin and chitosan, respectively. Gibbs free energies for the two adsorption processes of indigo carmine dye presented a positive value for chitin and a negative one for chitosan, reflecting that dye/surface interactions are thermodynamic favorable for chitosan and nonspontaneous for chitin at 298.15 K. The interaction processes were accompanied by an increase of entropy value for chitosan (90 +/- 6 J mol(-1)K(-1)) and a decrease for chitin (-145 +/- 13 J mol(-1)K(-1)). Thus, dye/chitosan interaction showed favorable enthalpic and entropic processes, reflecting thermodynamic stability of the formed complex, while dye/chitin interaction showed an exothermic enthalpic value and a highly nonfavorable entropic effect, resulting in a nonspontaneous thermodynamic system.     

甲壳素、壳聚糖的改性

综述了壳聚糖的化学改性和物理改性。通过对壳聚糖的改性,一方面可增进其在有机溶剂中溶解行为,为进一步应用提供反应前体;另一方面增强机械或生化性质,扩展其应用范围。     

CHITIN AND CHITOSAN FOR VERSATILE APPLICATIONS

ABSTRACT

Chitin and chitosan are versatile polymers, where the interest in chitosan is due to the large variety of useful forms that are commercially available or can be made available. Chitin basically is obtained from prawn/crab shells; chemical treatment of chitin produces chitosan. This article surveys applications of chitin and chitosan in various industrial and biomedical fields.     

A study of embolizing materials for chemo-embolization therapy of hepatocellular carcinoma: embolic effect of cisplatin albumin microspheres using chitin and chitosan in dogs, and changes of cisplatin content in blood and tissue.

Hepatic artery of dogs was embolized with cisplatin (CDDP) albumin microspheres containing chitin and chitosan to investigate the in vivo CDDP release kinetics from CDDP albumin microspheres, the CDDP cumulative characteristics in the liver, and the influence of microsphere administration on hepatic tissue. Results showed that changes in blood CDDP content were dependent on CDDP albumin microsphere type and that release kinetics were better sustained when chitin was added to the microspheres or when the microspheres were treated with chitosan. In particular, the administration of CDDP in the chitin-containing CDDP chitosan albumin microspheres showed a blood CDDP content of approximately 0.26 micrograms Pt/ml 14 d after administration. The administration of chitin-containing or chitosan treated CDDP microspheres showed a CDDP content in the hepatic tissue of 0.14 to 0.23 micrograms Pt/g 28 d after administration. They also showed better control of CDDP release than those without chitin or chitosan treatment. No CDDP influence on hepatic tissue was observed. We conclude that, even in vivo, chitin and chitosan are effective embolic materials.     

Fabrication of a chitin/chitosan hydrocolloid wound dressing and evaluation of its bioactive properties

Research on Chemical Intermediates - The aim of this study was to develop a chitin/chitosan hydrocolloid (CCH) wound dressing. Chitosan was cross-linked with tripolyphosphate to prepare chitosan...     

Release characteristics of cisplatin chitosan microspheres and effect of containing chitin

To increase cisplatin (CDDP) content, to suppress burst effect during the initial phase of drug release, and to improve the capacity of the system for sustained release, we prepared various types of CDDP chitosan microspheres incorporating chitin and investigated the content of CDDP and its in vitro release kinetics from these microspheres. The results of this study showed that the CDDP content increased with increasing chitosan concentration and that the incorporation of chitin in the carrier matrix produced a more pronounced increase in drug content. The addition of chitin also led to inhibition of the initial burst effect. The rate of CDDP release reduced with increasing concentration of chitosan: that is, the 50% CDDP release time was about 0.5 h with the microspheres prepared with 1.0% of chitosan and about 4.5 h with those prepared with 5.0% of chitosan, indicating about nine-fold prolongation. The addition of chitin further resulted in retardation of the rate of CDDP release. Meanwhile, our chitosan microspheres were shown to undergo enzymatic degradation by lysozymes.