壳聚糖改性的高分子表面活性剂的合成与性能

以商品壳聚糖(CTS)为原料,通过对-NH_2的化学改性,合成制备了壳聚糖改性的水溶性两性离子表面活性剂.采用正交试验法对合成反应工艺作了优化;通过红外光谱(IR)、核磁共振(H-NMR)及元素分析(EA)等方法对烷基壳聚糖中间体(RCTS)与最终产物,即烷基壳聚糖磺酸季铵盐(SRCTS)的分子结构进行了表征,并对SRCTS的水溶性、表面张力以及泡沫性能作了初步的探索.结果表明:经改性的SRCTS具有良好的表面活性与泡沫稳定性,其最低表面张力值可降至29.1mN/m;泡沫半衰期可提高65%.     

水溶性N,O-羟乙基壳聚糖的合成

在Na OH存在下,以溴乙醇为羟乙基化试剂对壳聚糖进行了改性,得到羟乙基壳聚糖(HECTS);用元素分析法(EA)确定了产物的羟乙基取代度(DS),并以产物的取代度为基准,用四因素三水平正交实验优化了反应的条件;同时,用FT-IR和~1H NMR表征了产物结构,超声辅助直接溶解法评价了产物的水溶性。结果表明,壳聚糖经碱化处理后再用溴乙醇改性,生成的产物为N,O-羟乙基壳聚糖(N,O-HECTS),羟乙基取代度为82.42%及其以上的N,O-HECTS在中性条件就具有较好的水溶性;当n溴乙醇/n壳聚糖单元=5.0,nNaOH/n壳聚糖单元=10.0,反应温度为50.0℃和反应时间为36.0h时,N,O-HECTS的羟乙基取代度可达112.39%。     

壳聚糖改性及用其整理纺织品抗菌性能的研究

用羟甲基化和醚化等方法制备了改性壳聚糖羟甲基壳聚糖和羟乙基乙基醚壳聚糖。在中性条件下它们溶解于水。实验显示，改性壳聚糖具有较好的抑菌作用和吸湿保湿性能。对织物进行的后整理实验发现，羟乙基乙基醚壳聚糖适用于对棉布的整理加工，羟甲基壳聚糖适用于对真丝绸的整理加工。经整理后的织物具有较好的抗菌性，且吸湿、透湿、染色性能较优。研究表明改性壳聚糖可作为优良的功能性天然“绿色”纺织品整理剂。     

壳聚糖及其衍生物抗菌活性的研究进展

壳聚糖是自然界目前发现的唯一碱性多糖,具有自然来源丰富,生物相容性好,可被生物降解,安全无毒和抗菌性强等许多天然的优良特性,现其广谱抗菌性已得到广泛的认可,但较差的水溶性限制了它的进一步应用。因此,通过一定的改性方法制备壳聚糖衍生物以提高其水溶性,是目前壳聚糖研究方面的热点之一。本论文就近年来几种常见的壳聚糖亲水改性方法及其衍生物在抗菌方面的应用进展进行综述,以期对壳聚糖的深入研究提供参考。     

壳聚糖功能化改性及其在药物载体中的应用

壳聚糖为天然多糖甲壳素脱除部分乙酰基的产物,因其优异的理化性质和生物学活性,成为生物医学应用中最有前景的聚合物之一。由于壳聚糖在中性和碱性溶液中溶解性较差,其应用受到了一定限制,通常对其进行功能化改性,生成一系列壳聚糖衍生物。壳聚糖衍生物可改善壳聚糖的水溶性、生物活力及力学性能,从而提高其利用价值,扩大其应用领域。本文综述了几种壳聚糖常用的功能化改性方法,包括接枝共聚、交联、羧甲基化、酰基化、烷基化。并介绍了改性壳聚糖作为药物载体应用的研究进展,旨在为改性壳聚糖的研究提供一定理论基础。     

PEG化壳聚糖/DNA自组装复合物的制备、表征和体外Hela细胞转染研究

通过有机合成和高分子聚合等方法将亲水性的聚乙二醇接枝到壳聚糖的氨基侧链上，得到了改性的壳聚糖—聚乙二醇接枝共聚物，应用现代波谱等技术对中间产物和最终产物进行了表征，采用绿色荧光蛋白基因质粒pEGFP—N1为DNA模型，在溶液中通过自动(静电)吸附得到PEG化的壳聚糖／DNA自组装复合物，初步研究了该自组装复合物对Hela细胞的体外转染效率。结果表明，活化的聚乙二醇被成功地接枝到壳聚糖上，使不溶于水的壳聚糖改性为水溶性的PEG化的壳聚糖。PEG化壳聚糖／DNA自组装复合物在Hela细胞体外转染率达到81％。因此，PEG化的壳聚糖有可能成为基因转染的非病毒载体。     

聚乙二醇改性壳聚糖作为小分子药物载体的研究进展

壳聚糖具有抗菌、抗氧化、增强胶凝特性以及可作为生物活性分子的微型或纳米载体等优点,其化学改性和应用近年来受到广泛关注。然而,壳聚糖既不溶于有机溶剂也不溶于水,极大地限制了它的应用。在改性的壳聚糖中,聚乙二醇化壳聚糖不仅能保持壳聚糖的优点,还能提高水溶性,并能有效运输生物活性分子。本文综述了近5年间聚乙二醇化壳聚糖作为紫杉醇、阿霉素、5-氟尿嘧啶等小分子载体的研究进展,为今后的研究提供有益参考和理论依据。     

新型壳聚糖双季铵盐的制备及其抗氧化活性

将2,3-环氧丙基三甲基氯化铵(CTA)与壳聚糖反应,制备了水溶性壳聚糖季铵盐(HTCC),然后,以HTCC与氯乙酰氯反应得到氯乙酰壳聚糖季铵盐(CAHTCC),最后,以吡啶取代CAHTCC中的活泼氯,得到水溶性壳聚糖双季铵盐(PAHTCC)。 通过红外光谱和¹³C核磁共振光谱等技术手段对产物结构进行了表征,同时测试了原料壳聚糖及其衍生物清除羟自由基、超氧阴离子以及DPPH的活性。 结果表明,PAHTCC的活性较原料壳聚糖及壳聚糖单季铵盐HTCC均有明显提高,在实验浓度1.6 g/L时,其对羟自由基、超氧阴离子及DPPH的清除率分别达到68.5%、74.3%和80.8%。 聚阳离子性大幅增强,进而抗氧化活性提高。     

聚乙二醇改性壳聚糖作为小分子药物载体的研究进展

壳聚糖具有抗菌、抗氧化、增强胶凝特性以及可作为生物活性分子的微型或纳米载体等优点,因此其化学改性和应用近年来受到广泛关注。然而,壳聚糖既不溶于有机溶剂也不溶于水,极大地限制了它的应用。在改性的壳聚糖中,聚乙二醇化壳聚糖不仅能保持壳聚糖的优点,还能提高水溶性,并能有效运输生物活性分子。因此,本文总结了2008-2012年聚乙二醇化壳聚糖作为紫杉醇、阿霉素、5-氟尿嘧啶等小分子载体的最新进展,为今后聚乙二醇化壳聚糖的研究提供有益参考和理论依据。     

壳聚糖及其衍生物应用于肥胖治疗的研究进展

肥胖是并发高血脂、脂肪肝、糖尿病和心脑血管损害等疾病的主要危险因子,减肥药物（食品）是一种有效的控制体重的手段。壳聚糖对脂肪和胆固醇具有良好的吸附性能,正在成为一种新型的减肥药物（食品）。结合本课题研究方向,综述了药用壳聚糖及其衍生物在治疗肥胖及其并发症方面应用的研究进展。通过在壳聚糖C6住-OH上改性制备了水溶性、油溶性和两亲性良好的壳聚糖衍生物,并通过动物试验研究了其减肥功效。     

Immobilization of cellulose extracted from Robinia Pseudoacacia seed fibers onto chitosan: Chemical characterization and study of methylene blue removal

The design of economical adsorbents to remove pollutants from contaminated water is attracting more attention. In this study, cellulose was successfully extracted from Robinia Pseudoacacia seed fibers and immobilized onto chitosan beads. The prepared spherical beads were then used for the biosorption of methylene blue dye from aqueous media. Samples were investigated using several analytical methods, namely FT-IR, XRD, EDX, SEM, and TGA analyses. The adsorption experiments showed that combining cellulose with chitosan improved the removal of methylene blue. The maximum uptake amount of methylene blue using cellulose–chitosan composite beads was 55 mg/g. However, it was about 35 mg/g at 20 °C for chitosan beads. The kinetic data complied strongly with the pseudo-second order equation, suggesting that the biosorption phenomenon has predominantly a chemical nature. Overall, the current study has shown a promising technique to design new adsorbents from abundant natural polymers for eliminating cationic dyes from water.     

壳聚糖接枝共聚改性最新研究进展

壳聚糖是一种天然高分子,也是迄今为止唯一发现的阳离子碱性多糖。壳聚糖分子链中富含羟基和氨基等反应性官能团,具有生物相容性、生物可降解性、抗菌性、无细胞毒性等优良性能,在生化、医药、环保、农业等领域有广泛的应用前景。然而,由于其大分子具有较好的立构规整性和较强的氢键作用,除稀盐酸、稀醋酸外,壳聚糖不溶于水和其它有机溶剂,因而限制了它的应用范围。为了扩大其应用领域,常通过接枝共聚反应来改善壳聚糖的性能。本文介绍了壳聚糖接枝共聚改性的最新研究进展,包括自由基引发接枝法、偶联接枝法以及催化接枝法。     

Catalytic,Asymmetric Synthesis of Phosphonic γ‐(Hydroxyalkyl)butenolides with Contiguous Quaternary and Tertiary Stereogenic Centers

A procedure that enables high yielding access to phosphonic γ‐(hydroxyalkyl)butenolides with excellent regio‐, diastereo‐ and enantiocontrol is reported. The simultaneous construction of up to two adjacent quaternary stereogenic centers by a catalytic asymmetric vinylogous Mukaiyama aldol reaction unites biologically and medicinally relevant entities, namely α‐hydroxy phosphonates and γ‐(hydroxyalkyl)butenolides. This is achieved by utilizing a readily available chiral copper‐sulfoximine catalyst showing a broad functional group tolerance for both the electrophilic and nucleophilic reactants. A discussion about potential factors affecting the observed level of enantioselectivity, which stems from the enantiopure sulfoximine ligand, is also included.     

Review: Preparation and Application of Magnetic Chitosan Derivatives in Separation Processes

Chitosan is one of the most abundant natural polysaccharide in nature. Due to its unique properties, chitosan has fascinated the scientific community since its discovery. When modified with other materials and combined with magnetic particles, the resulting composite material, a magnetic chitosan derivative, is provided with three significant characteristics. First, chitosan has excellent properties for preconcentration/extraction, such as adsorption and chelating effects, low cost, and nontoxicity. Second, new functional groups have enhanced the properties of chitosan that include water solubility, stability, recyclability, and enhanced adsorption capacity. Finally, due to the efficient and fast adsorption processes, as well as simple and convenient magnetic separation, the magnetic adsorbents greatly reduce the time of sample handling. In this article, recent synthesis and modification methods of magnetic chitosan derivatives are reviewed along with some applications in analytical separations.     

Synthesis and PMR spectra of 7-hydroxyalkylguanosinium acetates

Guanosine and 9-methylguanine treated with epoxides in glacial acetic acid are hydroxyalkylated stereoselectively at the N₇ position of the guanine moiety. Previously unreported 7-(hydroxyalkyl)guanosinium acetates from the reactions of six epoxides with guanosine and 7-(hydroxyalkyl)-9-methylguaninium acetates from the reactions of two epoxides with 9-methyl guanine in glacial acetic acid have been prepared and characterized by their pmr spectra. By using an excess of epoxide, quantitative conversion of guanosine or 9-methylguanine to the corresponding 7-hydroxyalkylguanosinium or 7-hydroxyalkyl-9-methylguaninium acetate was achieved. Comparisons of the pmr spectra of the 7-(hydroxyalkyl)guanosinium acetates in DMSO-d₆ to the spectrum of guanosine reveal that the H₈ and amino group proton absorptions common to guanosine are shifted to a lower field, the absorptions of the H₁ proton is absent, and the coupling constant of the H′₁-H′₂ protons of the ribosyl group is decreased from about 5.7 ± 0.1 Hz in guanosine to about 3.5 ± 0.1 Hz in the products. The use of the pmr spectral features of 7-(hydroxyalkyl)-9-methylguaninium compounds in characterizing 7-hydroxyalkylguanosinium compounds is discussed. Evidence is presented which suggests that extensive delocalization of positive charge exists in both the pyrimidine and imidazole rings of N₇-hydroxyalkylated guanosine and N₇-hydroxyalkylated-9-methylguanine. The possible effects of charge delocalization upon the hydrogen bonding potential of 7-hydroxyalkylated guanine moieties in DNA is discussed.     

Dielectric relaxations of chitosan: The effect of water on the α‐relaxation and the glass transition temperature

In this work thermal relaxations of chitosan are reported by using a novel methodology that includes subtraction of the dc conductivity contribution, the exclusion of contact and interfacial polarization effects, and obtaining a condition of minimum moisture content. When all these aspects are taken into account, two relaxations are clearly revealed in the low frequency side of the impedance data. We focus on the molecular motions in neutralized and non‐neutralized chitosan analyzed by dielectric spectroscopy in the temperature range from 25 to 250 °C. Low and high frequency relaxations were fitted with the Havriliak and Negami model in the 10^?1 to 108 Hz frequency range. For the first time, the low frequency α‐relaxation associated with the glass‐rubber transition has been detected by this technique in both chitosan forms for moisture contents in the range 0.05 to 3 wt % (ca. 18–62 °C). A strong plasticizing effect of water on this primary α‐relaxation is observed by dielectric spectroscopy and is supported by dynamic mechanical analysis measurements. In the absence of water (<0.05 wt %) the α‐relaxation is obscured in the 20–70 °C temperature range by a superposition of two low frequency relaxation processes. The activation energy for the σ‐relaxation is about 80.0–89.0 kJ/mol and for β‐relaxation is about 46.0–48.5 kJ/mol and those values are in agreement with that previously reported by other authors. The non‐neutralized chitosan possess higher ion mobility than the neutralized one as determined by the frequency location of the σ‐relaxation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2259–2271, 2009     

Self-diffusion of water-ethanol mixture in chitosan membranes obtained by pulsed-field gradient nuclear magnetic resonance technique

The self-diffusion of water and ethanol for crosslinked and uncrosslinked chitosan membranes have been investigated by pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy. It has been shown that during diffusion processes, water and ethanol are localized in different parts of the chitosan membrane. In the crosslinked membrane, the self-diffusion coefficient for water is higher, but that for ethanol is essentially lower, than those for the uncrosslinked membrane. For this reason, the mobility selectivity is essentially higher in crosslinked membrane as compared to the uncrosslinked. The sorption selectivity are the same for these two types of membranes.     

壳聚糖膜的处理方法与其渗透汽化性能间的关系

对壳聚糖均质膜折脱酸处理、干燥方法与所得膜的渗透汽化性能间的关系进行了研究。结果表明，处理方法的不同直接影响到膜的透过、分离性能。用含３ｗｔ．％ＮａＯＨ的醇水溶液（乙醇／水＝５０／５０（ｗｔ．／ｗｔ．））进行脱酸处理的膜，其α水／乙醇值，在料液温度为５５－７５℃的范围内几乎不变。     

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.