0’0-月桂酰壳聚糖的制备及表征

利用壳聚糖在甲磺酸溶剂中与月桂酰氯进行酰化反应,得到羟基上取代的0＇0-月桂酰基壳聚糖本实验制备了壳聚糖。通过元素分析计算产品的取代度,并对其进行了IR、1H-NMR表征。结果表明,通过此法月桂酰基能成功地接到了壳聚糖的羟基上,并获得较高的取代度。     

O'O-月桂酰壳聚糖的制备及表征

利用壳聚糖在甲磺酸溶剂中与月桂酰氯进行酰化反应,得到羟基上取代的O'O-月桂酰基壳聚糖本实验制备了壳聚糖。通过元素分析计算产品的取代度,并对其进行了IR、1H-NMR表征。结果表明,通过此法月桂酰基能成功地接到了壳聚糖的羟基上,并获得较高的取代度。     

取代度对壳聚糖基光交联水凝胶性能的影响

壳聚糖来源丰富,安全无毒,有着良好的生物相容性和可生物降解性,被广泛应用于生物医学领域。本研究以壳聚糖为基质,利用对叠氮苯甲酸对其进行改性,得到不同取代度的可光交联的壳聚糖衍生物,将其进行光交联得到了光交联壳聚糖基水凝胶。在通过红外光谱、¹H-NMR对壳聚糖衍生物进行结构表征的基础上,详细考察了叠氮化取代度对水凝胶失水率、蒸气透过率及药物释放性能的影响。结果表明,叠氮化取代度对于凝胶的性能有着显著影响,可以根据不同的使用环境制备出相应取代度的水凝胶来适应复杂的要求。     

羧甲基壳聚糖的合成

以壳聚糖原料，采用氟乙酸途径制备方式，得到制备羧甲基壳聚糖最佳工艺路线，并对产物进行了性能测定．其取代度达到90％以上。     

高脱乙酰度壳聚糖的制备及结构与性能研究

本文系统地研究了从虾壳制备高脱乙酰度、高分子量壳聚糖的方法。在一定条件下可得到脱乙酰度达97％,分子量达5×10~5左右的壳聚糖。用IR、NMR、DTA、TGA等分析技术对壳聚糖的结构与性能进行了研究。     

碱性离子液体碱化制备N-十二烷基化壳聚糖

合成了1-甲基-3-丁基咪唑醋酸盐([Bmim]OAc)、1-甲基-3-丁基咪唑碳酸盐([Bmim]2CO3)及1-甲基-3-丁基咪唑氢氧化物([Bmim]OH)离子液体,由FTIR、1HNMR和元素分析对其结构进行了确证。首先,用离子液体对壳聚糖碱化,再用碱化后壳聚糖与溴代十二烷进行烷基化反应,制备了高取代度的N-十二烷基化壳聚糖。用FTIR、1HNMR、XRD对烷基化产物进行了表征。考察了时间、温度及物料配比对N-十二烷基壳聚糖取代度的影响,得到较佳的反应条件:n([Bmim]OH)∶n(壳聚糖原料)=3∶1,45℃碱化1 h,n(溴代十二烷)∶n(碱化后壳聚糖)=2∶1,烷基化反应温度80℃,反应时间3 h,在该条件下十二烷基壳聚糖的取代度达到81%以上。离子液体重复使用3次后,N-十二烷基壳聚糖的取代度仍大于80%。     

一种制备丁二酰化壳聚糖的新方法

合成了甘氨酸盐酸盐离子液体([Gly]Cl),由1H-NMR对其结构进行了确证,并以其质量分数2%的水溶液为反应介质,制备水溶性丁二酰化壳聚糖。用XRD和FT-IR对产物进行了表征,结果表明:壳聚糖(CS)中引入了丁二酰基,并削弱了壳聚糖分子内和分子间的氢键作用,大大改善其水溶性。考察了反应时间、温度和反应物配比对丁二酰化壳聚糖取代度(DS)的影响,得到较佳的反应条件:反应时间4h,n(丁二酸酐):n(壳聚糖)=2.75,反应温度40℃,在该条件下丁二酰化壳聚糖的取代度达到90%以上。离子液体具有重复使用性,反应后的离子液体未经处理重复使用3次后,丁二酰化壳聚糖的取代度仍大于90%。     

壳聚糖的表面性能及分子量与脱乙酰度的影响

应用红外光谱法对四种壳聚糖样品进行了结构表征,同时估算了其脱乙酰度,并用粘度法测定了分子量。根据Washburn的浸渍理论和van Oss-Chaudhury-Good的组合理论,应用柱状灯芯技术,对壳聚糖的表面性能进行了测试。研究发现,壳聚糖的分子量和脱乙酰度都影响其表面性能。当脱乙酰度相同时,分子量与表面能γS及表面能分量γSLW、酸碱比值γS+/γS-成正比,而与其酸性力γS+和碱性力γS-以及极性率γAB/γs成反比;而分子量相近时,表面性能可能主要受脱乙酰度的影响。随着脱乙酰度的增加,壳聚糖的表面能γS及其分量γSLW、酸碱比值γS+/γS-都增大。实验所测得的壳聚糖的表面能数据得到文献的支持。     

疏水壳聚糖的制备及其凝血性能

为增强壳聚糖的止血效果,采用酰基化改性在壳聚糖氨基上连接长链烷基以形成疏水性壳聚糖。采用单因素实验对反应温度、月桂酸酐的浓度进行筛选,以疏水壳聚糖的黏度、取代度及凝血效果作为评价指标,通过梯度设计筛选得到的最优工艺条件为:温度55℃,壳聚糖质量分数为1%,月桂酸酐浓度7.84×10-3 mol/L。采用红外、核磁共振、接触角测试仪对其进行了表征,表明合成了疏水壳聚糖。体外凝血实验结果表明:疏水壳聚糖的止血效果与氨基的取代度在一定范围内呈正相关性,当取代度为10.8%和15.9%的疏水壳聚糖与血液分别混合后(疏水壳聚糖在混合物中质量分数不小于0.75%),1~4 s左右可形成稳定的凝胶,从而凝血。又通过小鼠肝脏止血实验发现疏水壳聚糖粉末能够迅速止血,且效果显著优于壳聚糖。     

疏水壳聚糖的制备及其凝血效果研究

为增强壳聚糖的止血效果,采用酰基化方法在壳聚糖氨基上连接长链烷基以形成疏水性壳聚糖。该制备工艺中采用单因素设计对反应过程中的温度、浓度进行筛选,以疏水壳聚糖的黏度、取代度以及凝血效果作为评价指标,通过梯度设计筛选得到最优工艺条件：温度55℃,壳聚糖浓度1%（g/ml）,月桂酸酐浓度0.3%（g/ml）。采用红外、核磁等方法对其进行表征,表明合成了疏水壳聚糖。由体外凝血实验发现,疏水壳聚糖的止血效果与其取代度在一定范围内呈正相关性,当其取代度小于9%时,1%（g/ml）的疏水壳聚糖乙酸溶液止血效果不理想;当超过15%时,相同质量浓度的疏水壳聚糖乙酸溶液呈凝胶状态,无法与血液充分混合,严重影响其止血效果。通过该实验发现取代度为9%-15%的疏水壳聚糖与血液混合后,且疏水壳聚糖的浓度不小于0.75%（g/ml）时,具有良好的凝血效果。又通过小鼠在体肝脏止血实验发现疏水壳聚糖粉末能够迅速止血,且效果显著优于壳聚糖。因此,由该方法合成的疏水壳聚糖作为止血材料时,能够显著改善壳聚糖的止血效果,达到快速止血,有望开发为新型止血材料。     

TEMPO-NaOCl-NaBr体系选择性氧化壳聚糖及其产物的结构表征

壳聚糖的功能化改性及其生物医学等领域的应用是近年来备受人们关注的重要研究方向.文章研究了TEMPO-NaOCl-NaBr体系对不同形态壳聚糖的氧化过程及其产物的结构表征.发现NaOcl、NaOCl-NaBr、TEMPO-NaOCl和TEMPO-NaOCl-NaBr体系的氧化反应速率递增,溶胀态壳聚糖和壳聚糖纤维由于有着...     

壳聚糖与柠檬醛缩合反应产席夫碱及其抗菌活性

通过壳聚糖与柠檬醛在超声波振荡下反应制备了壳聚糖缩柠檬醛席夫碱。采用[L9（33）]正交实验探讨了反应时间、反应温度及反应物配比对壳聚糖席夫碱缩合率和取代度的影响。最佳条件为：反应物配比n（壳聚糖）∶n（柠檬醛）=1∶6,反应温度40～50 ℃,反应时间10 h,壳聚糖席夫碱的缩合率可达86%,取代度为0.82。红外光谱和X射线衍射光谱结果表明产物具有壳聚糖席夫碱的结构特征。对大肠杆菌、金黄色葡萄球菌和黑曲霉的抗菌实验表明,该产物对大肠杆菌、金黄色葡萄球菌和黑曲霉的最低抑菌浓度分别为1 g/L、1 g/L和5 g/L,其抗菌活性随浓度的增加而增加,且优于壳聚糖。     

Current state of chitin purification and chitosan production from insects

Chitin, and especially its deacetylated variant chitosan, has many applications, e.g. as carrier material for pharmaceutical drugs or as a flocculant in wastewater treatment. Despite its versatility and accessibility, chitin, the second most abundant polysaccharide on Earth, has so far been commercially extracted only from crustaceans and to a minor extent from fungi. Insects are a viable alternative source of chitin, but they have not been exploited in the past due to limited availability. Today however, for the sustainable production of animal feed, insect farming is being developed substantially. The availability of large quantities of insect biomass and chitin-rich side products such as exuviae and exoskeletons has been increasing. This review provides an overview of recently published studies of chitin extraction from insects, its subsequent conversion into chitosan and the primary analytical methods used to characterize insect-based chitin and chitosan. We have discovered a large number of research articles published over the past 20 years, confirming the increased attention being received by chitin and chitosan production from insects. Despite numerous publications, we identified several knowledge gaps, such as a lack of data concerning chitin purification degree and chitosan yield. Furthermore, analytical methods used to obtain physicochemical characteristics, structural information and chemical composition meet basic qualitative requirements but do not satisfy the need for a more quantitative evaluation. Despite the current shortcomings that need to be overcome, this review presents encouraging data on the use of insects as an alternative source of chitin and chitosan in the future. © 2020 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).     

Chitosan and modified chitosan membranes I. Preparation and characterisation

Chitosan has been prepared from prawn shell and crab shell chitin. The molecular weight of the material derived from prawn shells is higher than that obtained from crab shell. The molecular weight, tensile strength, elongation at the break, and hydrophilic properties of chitosan are extremely dependent on the degree of deacetylation achieved when chitin is hydrolyzed to chitosan. Graft copolymers have been prepared with chitosan and a series of vinyl monomers using both heterogeneous and homogeneous reaction conditions. The hydrophilic properties of chitosan can be modified by blending with poly(vinyl alcohol).     

Ultraviolet-light-filtering behavior of fullerene-amine derivative/chitosan blended membranes

The aminated fullerene/chitosan blended membranes with novel ultraviolet-light-filtering properties have been prepared by mixing chitosan with fullerene ethylenediamine or ethanolamine derivative in a solution containing 2% acetic acid, then casting the mixture on a glass plate. The effects of fullerene-amine derivative and chitosan structures on light transmission properties of the blended membranes are investigated systematically. The fullerene derivative kind, aminated fullerene content and crosslinking degree of chitosan greatly affect their light-filtering properties, while deacetylation degree, molecular weight and carboxymethylation of chitosan only have slight influence. Further, a possible mechanism for the UV filtering property was discussed. The strong interactions, especially electron donor-acceptor occur in condensed state may play a significant role in the unique optical property.     

Factors Influencing the Antibacterial Activity of Chitosan and Chitosan Modified by Functionalization

The biomedical and therapeutic importance of chitosan and chitosan derivatives is the subject of interdisciplinary research. In this analysis, we intended to consolidate some of the recent discoveries regarding the potential of chitosan and its derivatives to be used for biomedical and other purposes. Why chitosan? Because chitosan is a natural biopolymer that can be obtained from one of the most abundant polysaccharides in nature, which is chitin. Compared to other biopolymers, chitosan presents some advantages, such as accessibility, biocompatibility, biodegradability, and no toxicity, expressing significant antibacterial potential. In addition, through chemical processes, a high number of chitosan derivatives can be obtained with many possibilities for use. The presence of several types of functional groups in the structure of the polymer and the fact that it has cationic properties are determinant for the increased reactive properties of chitosan. We analyzed the intrinsic properties of chitosan in relation to its source: the molecular mass, the degree of deacetylation, and polymerization. We also studied the most important extrinsic factors responsible for different properties of chitosan, such as the type of bacteria on which chitosan is active. In addition, some chitosan derivatives obtained by functionalization and some complexes formed by chitosan with various metallic ions were studied. The present research can be extended in order to analyze many other factors than those mentioned. Further in this paper were discussed the most important factors that influence the antibacterial effect of chitosan and its derivatives. The aim was to demonstrate that the bactericidal effect of chitosan depends on a number of very complex factors, their knowledge being essential to explain the role of each of them for the bactericidal activity of this biopolymer.     

Chitosan hydrogel covalently crosslinked by gold nanoparticle: Eliminating the use of toxic crosslinkers

Tissue engineering has directed a lot of effort toward the development of devices with suitable biocompatibility and mechanical properties. Chitosan has been pointed as a valuable material to be applied in scaffolds due to its antimicrobial activity and biocompatibility. Nevertheless, the low mechanical resistance associated with the requirement of toxic crosslinkers has hampered translational application of chitosan hydrogel. Herein, the use of gold nanoparticles (AuNP) as crosslinker is reported as a great strategy to obtain chitosan hydrogel without using toxic reactants. In addition, the resultant chitosan hydrogel, crosslinked by AuNP of 30 nm (AuNP30), presented outstanding properties compared to chitosan hydrogel crosslinked by glutaraldehyde. Chitosan hydrogel crosslinked by AuNP30 presented lower porosity, which provided lower swelling degree and slower degradation rate. In addition, compressive strength was about two times higher than the chitosan hydrogel crosslinked by glutaraldehyde. The crosslink by AuNP30 also increased the biocompatibility of the hydrogel. Chitosan hydrogel crosslinked by AuNP30 did not show cytotoxicity against MEF cells, whereas cell viability of cells incubated with extract from chitosan hydrogel crosslinked by glutaraldehyde was only 41%. In conclusion, the results reported herein pointed that the use of AuNP30 as crosslinker agent provided to chitosan hydrogel enhanced properties that made it suitable to application in biomedical devices.     

不同脱乙酰度壳聚糖的制备及其聚集行为研究

壳聚糖的脱乙酰度直接影响壳聚糖的物理化学和生物特性。在乙酸-水-甲醇体系中研究壳聚糖的乙酰化反应工艺,考察了反应时间、壳聚糖质量浓度对乙酰化反应的影响,优化了反应条件。研究表明,反应时间为6h时,壳聚糖乙酰化反应基本完全,乙酰化反应后,相对重均分子质量基本不变,壳聚糖相对分子质量分布变宽。在优化后的反应条件下,改变乙酸酐加入量分别制备了脱乙酰度为76%,64%和54%的不同脱乙酰度的壳聚糖。芘荧光光谱研究表明,壳聚糖的临界聚集浓度(CSC)随脱乙酰度的降低而增加。     

Swelling Properties of a Nickel-containing Cross-linked Chitosan

The swelling kinetics and equilibrium swelling degree of a series of nickel-containing chitosan cross-linked with glutaraldehyde at amino:aldehyde reactant ratios of 1:0.05, 1:0.17, and 1:0.5 were studied. At an amino:aldehyde reactant ratio of 1:0.17 the cross-linked chitosan was shown to swell in the basic solvent (50 mM tris-HCl, 0.2 M NaCl, pH = 7.5) and to have the best nickel retaining properties. Based on these results, the nickel-containing cross-linked chitosan has been concluded to be a potentially good candidate for the specific binding of proteins having terminal histidines.     

Influence of chitosan characteristics on coagulation and flocculation of organic suspensions

Several samples of chitosan with different degrees of deacetylation and of different molecular weights were tested for the coagulation–flocculation of organic suspensions. Organic suspensions were prepared by mixing mushroom powder with tap water. Experiments were carried out at pH 5, pH 7, and pH 9. Because decreasing the pH reduced the amount of chitosan required to reach the required turbidity, at pH 9, a high concentration of chitosan was required to achieve the required treatment levels, whereas the difference was less significant between pH 7 and pH 5 (the required concentration of chitosan was halved). Though viscosity, correlated to the molecular weight of chitosan, affected treatment performance, its influence on the efficiency of coagulation–flocculation could be substantially reduced by slightly increasing the concentration of the polymer. This is of importance in the processing of industrial effluents: the aging of a chitosan solution, which may cause partial depolymerization, and loss of viscosity, will have a limited impact on process efficiency. The degree of deacetylation also has a limited effect on treatment performance, especially when the degree of deacetylation exceeds 90%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2070–2079, 2005