片状壳聚糖的脱乙酰化反应

本文采用一种新方法制备 10 0 %脱乙酰度的壳聚糖。低脱乙酰度壳聚糖溶解在酸溶液中并通过溶剂蒸发制备得到片状壳聚糖。片状壳聚糖进行一步碱处理就可以得到高脱乙酰度壳聚糖。     

羧甲基壳聚糖基生物医用材料降解代谢行为的研究进展

作为一种水溶性多糖高分子材料,羧甲基壳聚糖(carboxymethyl chitosan, CMCTs)具有优异的生物相容性和生物降解性以及保湿、止血、抗菌、可吸收等一系列优良的功能特性,因而被广泛应用于医工交叉领域。羧甲基壳聚糖进入体内后,在酶、氧、微生物、水等环境适宜时能够被降解,并经吸收、代谢、排泄。其体内降解速率主要取决于材料的尺寸、脱乙酰度、取代度、分子量等。了解羧甲基壳聚糖在动物体内的降解代谢行为,对羧甲基壳聚糖在转化过程中的质量控制和临床应用至关重要。然而就目前而言,羧甲基壳聚糖在生物体内降解代谢的影响因素及其体内吸收、分布、代谢、排泄规律缺乏系统性总结,这一现状从基础层面严重制约了其在生物医药领域的进一步发展。基于上述问题,本文对近年来羧甲基壳聚糖基生物医用材料的降解、代谢相关研究进行梳理和总结,重点阐述了羧甲基壳聚糖作为可降解材料的生物学特性、降解方式、代谢过程等,系统揭示羧甲基壳聚糖体内降解、代谢的规律,并对植入物尺寸、脱乙酰度、取代度、分子量、交联度及成分比例等影响羧甲基壳聚糖降解速率的主要因素进行归纳,以期为羧甲基壳聚糖基生物医用材料的研发和转化研究提供参考。     

不同脱乙酰度对壳聚糖表面物理及吸附性能的影响

壳聚糖是甲壳素部分脱乙酰化的产物,脱乙酰度的大小对壳聚糖的性能影响很大。利用碱液法,通过对反应时间的控制,制备了不同脱乙酰度的壳聚糖并对其性能进行了研究。结果表明,随着脱乙酰度的增大,壳聚糖膜的吸水率增加,而对其表面接触角的变化则没有影响。同时,壳聚糖海绵对Ca2+和牛血清蛋白(BSA)的吸附能力也随着脱乙酰度的增大而增加。     

壳聚糖/SiO2杂化材料膜制备的研究

由甲壳质制得不同脱乙酰度、粘度的壳聚糖;制成的壳聚糖盐酸溶液与正硅酸乙酯在不同的条件下混合,得到一种杂化材料;通过红外光谱检测和物理性质观测到部分产物有新键形成;反应温度、时间ｐＨ值对产物形成膜的物理和机械性质有影响;与壳聚糖膜相比,部分杂化膜不溶解于稀酸溶液。     

羧甲基壳聚糖水凝胶制备及其在药物控释中的应用

以戊二醛为交联剂制备了一系列羧甲基壳聚糖pH敏感水凝胶 .研究了合成条件对羧甲基壳聚糖水凝胶溶胀性能的影响 .实验结果表明羧甲基壳聚糖的脱乙酰度、交联剂用量对水凝胶溶胀率的影响较大 .pH=3 0时 ,水凝胶收缩 ,而pH =1 0 ,5 0 ,7 4 ,9 0时 ,水凝胶溶胀 ,且在碱性条件下水凝胶的溶胀率远大于酸性条件下的溶胀率 .包埋在此水凝胶中的水杨酸释放随载药介质的pH值和水凝胶半径大小的变化而显著不同 ,pH =1 0条件下载药的水凝胶的释药率大于pH =7 4 ,12 0条件下的释药率 ,且水凝胶的半径越大 ,释药速度和释药率也越大     

碱量法测定壳聚糖脱乙酰度的研究

碱量法(包括酸碱滴定法和电位滴定法)是目前测定壳聚糖脱乙酰度较为常用的方法,其原理是用过量的稀酸与一定量的待测壳聚糖反应,然后用标准NaOH溶液滴定过量的酸来测量壳聚糖中自由氨基的量,从而计算壳聚糖的脱乙酰度(DD值)。计算脱乙酰度的公式多用:DD=(-NH2)%/0.094×100%(公式一)。而另外一个碱量法中未用过的脱乙酰度计算公式为:DD=[203n/(G 42n)]×100%(公式二),本文用计算公式一和公式二分别计算在酸碱滴定法和双突跃电位滴定法中壳聚糖的脱乙酰度,结果表明:在酸碱滴定法中,用公式一的计算的结果准确度更高,而在双突跃电位滴定法中用公式二计算的结果准确度更高。     

线性滴定法同时测定壳聚糖的脱乙酰度及其胺基的表观离解常数

本文用线性滴定法测定了壳聚糖的脱乙酰度，并同时测定了壳聚糖中胺基的表现离解常数，对文献中的两个计算脱乙酰度的公式，给出了具体的含义，修正了公式中的错误。重复测定（ｎ＝５）不同粘度的样品的结果表明相对标准偏差小于１．４％，同时讨论了脱乙酰度与壳聚糖的粘度，胺基表现解常数之间的关系。     

酸碱电导滴定法测定壳聚糖脱乙酰度

研究了酸碱滴定中壳聚糖溶液电导的变化，利用电导变化两个转折点之间碱的用量来计算壳聚糖的脱乙酰度，消除了壳聚糖吸附的残留酸或碱的影响。该方法具有准确可靠、重复性好、转折点明显等优点。用于实际样品的测定，结果较好，相对标准偏差小于0.6%。     

壳聚糖超声可控降解及降解动力学研究

通过正交实验法考察了壳聚糖溶液浓度、反应温度、超声强度以及醋酸溶液浓度对超声降解反应的影响,确定了最佳反应条件,制备了一系列不同分子量的壳聚糖.研究了壳聚糖溶液浓度、反应温度以及壳聚糖原料分子参数与降解速率常数的关系.通过红外光谱、X-射线衍射和凝胶渗透色谱对降解产物进行了表征.结果表明,超声降解壳聚糖的最佳条件为10℃,壳聚糖溶液浓度2.5g/L.降解速率常数随壳聚糖溶液浓度和反应温度的降低而增大.高分子量和低脱乙酰度的壳聚糖原料有较高的降解速率和降解速率常数,壳聚糖原料的分子量对降解速率和降解速率常数的影响大于脱乙酰度对其的影响.超声波导致了壳聚糖分子量的降低和产物晶体结构的破坏,但没有改变产物的脱乙酰度和糖残基结构.     

甲壳素类液晶高分子的研究Ⅳ.脱乙酰度对壳聚糖液晶性的影响

通过壳聚糖乙酰化法制备了不同脱乙酰度的壳聚糖 ,并研究了脱乙酰度这一结构因素对壳聚糖溶致液晶性的影响 .观察到脱乙酰度为 5 0 %左右时 ,壳聚糖在水中和二氯乙酸中的溶致液晶临界浓度最高 .壳聚糖在水中的溶致液晶临界浓度远低于在二氯乙酸中的临界浓度 .     

卷烟化学指标的因子分析

运用因子分析法对A牌号卷烟的18个化学指标进行分析,结果表明:烟丝的总糖、还原糖、总氮、总植物碱、水分、氯离子、钾离子、葡萄糖、麦芽糖、苹果酸、异戊酸、苯甲醇、茄酮、β-大马酮14个指标,及主流烟气的水分、CO、烟碱、焦油4个指标所含的信息可由8个因子来表示。该8个因子模型解释了试验数据总方差的86.7%;烟丝的致香成分、水分、糖类物质、有机酸类物质对卷烟A的质量风格具有重要影响,特别是致香成分在进行卷烟质量表征时应该重点关注。因子分析结果为卷烟的化学表征和质量控制提供了有用的参考。     

The Distribution of Total Particulate Matter (TPM) And Nicotine Between Mainstream and Sidestream Smoke in Bidis and Cigarettes

ABSTRACT

The mainstream (MS) and sidestream (SS) smoke of three types of popular Indian cigarettes, a brand of low tar Indian cigarettes, a brand of US cigarettes and two brands of popular Indian bidis were analysed for carcinogenic total particulate matter (TPM) and nicotine levels employing standard smoking conditions and/or modified smoking standards.

The analysis clearly demonstrated relatively higher levels of TPM and nicotine in MS of three types of popular Indian cigarettes when compared with a brand of low tar Indian cigarettes or a brand of US cigarettes or reported values for MS of western cigarettes. This was also reflected in MS/SS ratios of TPM and nicotine as TPM and nicotine levels in SS of Indian and US cigarettes were similar, when tested employing standard smoking conditions.

Comparative analysis of Indian bidis/cigarettes and a brand of US cigarettes employing modified smoking standard (i.e. 2 puffs/min instead of 1 puff/min) revealed significantly lower values of TPM and nicotine in SS of Indian bidis when compared with corresponding values in Indian/US cigarettes. This shows that contribution of TPM and nicotine in SS from a single bidi to environmental tobacco smoke (ETS) is very much less than that of a single cigarette, and contribution of SS from Indian and US cigarettes to ETS appear to be similar. Reduced levels of TPM and nicotine in SS of bidis, probably due to lack of added burning agents, result into relatively higher deliveries of TPM and nicotine in MS as reflected by higher MS/SS values.     

Environmental Application of Chitosan Resins for the Treatment of Water and Wastewater: A Review

Chitosan is a polysaccharide formed mainly from repeating residues of D-glucosamine, having primary amino groups. It is of great interest not only as an underutilized resource, but also as a new functional material of high potential in various fields, and recent progress in chitin chemistry is quite noteworthy. The purpose of this review is to take a closer look at chitosan application in water technology based on (a) its ability to bind toxic pollutants, (b) the mod of chitosan modification, (c) the nature of the interaction of chitosan with different pollutants, and (d) chitosan regeneration and recycling.     

沸石在去除卷烟烟气中亚硝胺的应用

吸烟污染;沸石;添加剂;沸石在去除卷烟烟气中亚硝胺的应用     

Lactic acid demineralization of green crab (Carcinus maenas) shells: effect of reaction conditions and isolation of an unusual calcium complex

Chitin and chitosan are potentially useful and environmentally friendly biopolymers with a wide range of value-added applications. Effective and green technologies for isolation of these materials are potentially important. Here, we report the use of lactic acid for the demineralization of green crab shells. Green crab shells and lactic acid, produced during cheese making, are two waste streams that could be tapped for large-scale chitin and chitosan processing. We have studied the effect of concentration and temperature on the demineralization of green crab shells. An unusual calcium lactate/lactic acid complex was also isolated and crystallographically characterized. The results have implications not only for the use of weak acids in the isolation of chitin and chitosan but also for the use of lactic acid as a solvent in green chemistry.     

甲壳素/壳聚糖接枝共聚反应

综述了近年来甲壳素/壳聚糖接枝共聚的研究进展。以不同单体分类，分别综述了壳聚糖与小分子乙烯基单体、大分子聚乙二醇单体、聚乳酸单体、环糊精、树状大分子接枝的研究，并介绍了新的接枝技术——生物催化接枝共聚，以及接枝壳聚糖衍生物的应用。     

Quantitation of nicotine in tobacco products by capillary electrophoresis

A simple and rapid capillary electrophoresis (CE) method was developed for the quantitation of nicotine in commercial tobacco products. The method involves a 6 min run at 30 kV, using a 50 mM phosphate buffer (pH 2.5), paraquat as internal standard, and UV detection at 260 nm. Nicotine was extracted from tobacco products in <15 min. Recoveries from spiked extracts were >95%, and the extraction efficiencies of water, 1 M HCI, 1 M acetic acid, 5 mM phosphate buffer (pH 2.5), and 1% triethanol amine were similar. Nicotine concentrations in 67 samples of cigarettes, cigars, and bidis varied between 0.37 and 2.96% (w/w). An established gas chromatography/mass spectrometry method using toluene extraction consistently yielded lower nicotine values than the CE method. Experimental evidence suggests that this is due to insufficient extraction of nicotine by toluene.     

Grafting of 18β-Glycyrrhetinic Acid and Sialic Acid onto Chitosan to Produce a New Amphipathic Chitosan Derivative: Synthesis,Characterization, and Cytotoxicity

Chitosan is the only cationic polysaccharide found in nature. It has broad application prospects in biomaterials, but its application is limited due to its poor solubility in water. A novel chitosan derivative was synthesized by amidation of chitosan with 18β-glycyrrhetinic acid and sialic acid. The chitosan derivatives were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and measurement of the zeta potential. We also investigated the solubility, cytotoxicity, and blood compatibility of chitosan derivatives. 18β-glycyrrhetinic acid and sialic acid could be grafted onto chitosan molecular chains. The thermal stability of the synthesized chitosan derivatives was decreased and the surface was positively charged in water and phosphate-buffered saline. After chitosan had been modified by 18 β-glycyrrhetinic acid and sialic acid, the solubility of chitosan was improved greatly in water and phosphate-buffered saline, and percent hemolysis was <5%. Novel amphiphilic chitosan derivatives could be suitable polymers for biomedical purposes.