半纤维素基水凝胶制备及应用研究进展

半纤维素基水凝胶是一种具有优异保水性、良好生物相容性和力学性能的三维网络状亲水聚合物,在软材料领域尤其是半纤维素基材料研究领域备受瞩目。本文综述了近年来半纤维素基水凝胶的研究进展,从化学交联和物理交联两个方面介绍了半纤维素基水凝胶的制备方法、形成机理和性能,比较了化学交联中光、酶、微波辐射和辉光放电电解等离子体等不同引发体系的差异,总结了半纤维素基水凝胶在药物控释、伤口敷料、高效吸附及3D打印等领域的最新应用和发展,并对半纤维素基水凝胶领域所面临的挑战进行了总结和展望,以期为新型半纤维素水凝胶的研究提供参考。     

原子转移自由基聚合方法制备的半纤维素基水凝胶及其性能

以传统稀碱抽提法从农业废弃物——玉米芯中分离出的半纤维素为原料,采用原子转移自由基聚合方法(ATRP),通过控制反应条件,将具有温度响应特性的N-异丙基丙烯酰胺(NIPAM)和交联功能单体二甲基丙烯酸乙二醇酯(EDG)引入上述聚合物侧链中,制备出具有PNIPAM链段和不饱和双键封端侧链的半纤维素衍生物,经紫外光辐照交联成功制备出新型半纤维素基水凝胶。研究结果表明,这种半纤维素基水凝胶具有显著的温度负响应特性。此外,水凝胶的温度响应特性以及溶胀/消溶胀行为还受到聚合物的交联度、接枝共聚物原料组成以及功能单体添加量等因素的影响。     

交联方式对半乳糖基温敏凝胶结构和性能的影响

为改善传统化学交联水凝胶的低力学性能、透明度、溶胀度和生物相容性, 以无机纳米粒子硅酸镁锂(LMSH)作为物理交联剂, 半乳糖氨基化的丙烯酸衍生物(GAC)作为生物相容性单体, N-异丙基丙烯酰胺(NIPAM)为功能单体, 采用原位自由基聚合制备得到兼具温度敏感性和生物相容性的纳米复合水凝胶poly(NIPAM-LMSH-GAC)。结果表明: LMSH在水凝胶基体中被完全剥离, 并起到交联作用; 相比于传统化学交联剂制备的此类水凝胶, 所得物理交联的纳米复合水凝胶具有更高的溶胀度、良好的温敏性、优异的脉冲响应性, 但鼠成纤细胞(L929)在纳米复合水凝胶表面的细胞数量略低; 物理交联剂LMSH的使用和一定量的GAC的使用并没有明显改变水凝胶的体积相转变温度(VPTT), 仍保持在33℃左右。     

交联方式对半乳糖基温敏凝胶结构和性能的影响

为改善传统化学交联水凝胶的低力学性能、透明度、溶胀度和生物相容性,以无机纳米粒子硅酸镁锂(LMSH)作为物理交联剂,半乳糖氨基化的丙烯酸衍生物(GAC)作为生物相容性单体,N-异丙基丙烯酰胺(NIPAM)为功能单体,采用原位自由基聚合制备得到兼具温度敏感性和生物相容性的纳米复合水凝胶poly(NIPAM -LMSH-GAC).结果表明:LMSH在水凝胶基体中被完全剥离,并起到交联作用;相比于传统化学交联剂制备的此类水凝胶,所得物理交联的纳米复合水凝胶具有更高的溶胀度、良好的温敏性、优异的脉冲响应性,但鼠成纤细胞(L929)在纳米复合水凝胶表面的细胞数量略低;物理交联剂LMSH的使用和一定量的GAC的使用并没有明显改变水凝胶的体积相转变温度(VPTT),仍保持在33℃左右.     

壳聚糖水凝胶的制备及其在药物释放中的应用

水凝胶作为性能良好的载体,在药物的控释、组织工程等领域有着广泛的应用。壳聚糖是一类天然的带正电荷的碱性多糖,由其形成的水凝胶具有较好的生物相容性、生物降解性、抗菌和低细胞毒性,因此,壳聚糖水凝胶有着良好的生物应用前景。本文综述了壳聚糖水凝胶的制备方法(包括物理交联法和化学交联法),在物理交联法部分着重介绍了离子化合物及聚电解质分子与壳聚糖通过离子交联形成水凝胶,以及利用分子链间的疏水作用形成壳聚糖水凝胶的方法;而在化学交联法部分介绍了合成壳聚糖水凝胶的化学手段,包括交联剂、光照辐射和酶的使用。继而概述了壳聚糖水凝胶在药物缓释应用方面的研究进展,包括温度、pH值和电场响应的药物控释体系。最后展望了壳聚糖水凝胶未来的发展前景。     

聚丙烯酰胺/聚甲基丙烯酸(2-甲基氨基)乙酯高强度双网络水凝胶的制备及pH响应性

利用两步法合成了聚丙烯酰胺(PAM)/聚甲基丙烯酸(2-甲基氨基)乙酯(PDMAEMA)双网络水凝胶,第一网络为锂藻土(Laponite)物理交联的PAM纳米复合水凝胶,第二网络为化学交联剂N,N-亚甲基双丙烯酰胺(BIS)交联PDMAEMA。研究了2种网络相对含量、纳米黏土Laponite用量、化学交联剂BIS用量对水凝胶强度和pH响应性的影响。研究结果表明,PAM/PDMAEMA双网络水凝胶具有高强度,改变单体AM和DMAEMA的配比、交联剂的用量,其拉伸强度在36～91.9 kPa范围内可调。PAM/PDMAEMA双网络水凝胶还具有灵敏的pH刺激响应性,在pH=4时双网络水凝胶溶胀度急剧下降。     

低化学交联反蛋白石水凝胶的制备及多重刺激响应性

将物理交联与化学交联相结合,利用蛋白石结构光子晶体模板法制备了低化学交联的聚N-异丙基丙烯酰胺/丙烯酸(C-dots/BIS-P(NIPAm-AA))反蛋白石结构光子晶体水凝胶(IOH₍P(NIPAm-AA)))。其中,pH敏感性单体丙烯酸(AA)和温敏性单体N-异丙基丙烯酰胺(NIPAm)的引入赋予了IOH₍P(NIPAm-AA))多重刺激响应性。通过扫描电镜表征了IOH₍P(NIPAm-AA))的内部微观结构,探究了共聚单体AA含量对IOH₍P(NIPAm-AA))的影响,并基于结构色的变化来研究IOH₍P(NIPAm-AA))对外部刺激的响应行为。结果表明,低化学交联的IOH₍P(NIPAm-AA))具有规整有序的三维大孔结构。随着共聚单体AA用量从0.54 mL增大到0.9 mL,IOH₍P(NIPAm-AA))的结构色由蓝色转为蓝绿色再变为黄绿色,同时反射光谱发生了明显的红移。IOH₍P(NIPAm-A...     

生物可降解温敏性物理交联水凝胶的研究进展

近年来,原位形成的水凝胶体系已有诸多报道,通过溶剂交换、紫外线照射、离子浓度、pH值和温度的改变可原位诱导凝胶化转变。温敏性凝胶体系通常具有微妙的疏水-亲水两亲性平衡,在不需要有机溶剂、偶联剂和其它外界刺激的条件下,仅通过改变环境温度即可触发凝胶化相转变。生物可降解的温敏性水凝胶具有广阔的应用前景,既能作为药物缓释与输送的载体,也可用作组织再生的支架等生物医学材料。文中根据凝胶基体共聚物拓扑结构的不同,详细综述了近年生物可降解温敏性物理交联水凝胶的研究进展,及其化学物理结构与凝胶化行为、凝胶特性之间的内在联系。     

生物可降解温敏性物理交联水凝胶的研究进展EI北大核心CSCD

近年来,原位形成的水凝胶体系已有诸多报道,通过溶剂交换、紫外线照射、离子浓度、pH值和温度的改变可原位诱导凝胶化转变。温敏性凝胶体系通常具有微妙的疏水-亲水两亲性平衡,在不需要有机溶剂、偶联剂和其它外界刺激的条件下,仅通过改变环境温度即可触发凝胶化相转变。生物可降解的温敏性水凝胶具有广阔的应用前景,既能作为药物缓释与输送的载体,也可用作组织再生的支架等生物医学材料。文中根据凝胶基体共聚物拓扑结构的不同,详细综述了近年生物可降解温敏性物理交联水凝胶的研究进展,及其化学物理结构与凝胶化行为、凝胶特性之间的内在联系。     

温度/pH双重敏感性芦苇半纤维素基水凝胶的制备与表征

通过自由基聚合反应制备出以芦苇半纤维素为基材的温度/pH双重敏感性水凝胶材料。考察不同单体丙烯酸(AA)和N-异丙基丙烯酰胺(NIPAAm)摩尔比对其温度和pH的响应能力,探讨水凝胶的形成机制和消溶胀动力学行为。结果表明,四种不同单位摩尔比水凝胶均具有温度和pH双重敏感性,NIPAAm摩尔比含量高的水凝胶对温度响应更为敏感,而结构中的AA对水凝胶pH敏感行为起主要作用,消溶胀动力学符合准一级模型,消溶胀速率随NIPAAm摩尔比增加而加大。     

Effect of AAc-GA content on swelling behaviors of temperature-sensitive PNIPAAm-based hydrogels

A series of temperature-sensitive poly(NIPAAm-co-AAc-GA) hydrogels were synthesized by the copolymerization of glycyrrhetinic acid with vinyl monomer (AAc-GA) and N-isopropylacrylamide (NIPAAm) in N, N-dimethylformamide (DMF). Since GA has the specific binding capacity to asialoglycoprotein receptors on the membrane of hepatocyte, the hydrogel with GA could be expected as good candidate for hepatic cell culture. The results showed that macroporous and channel network structure was formed in the hydrogel matrix. With increasing the AAc-GA content, the swelling ratios of hydrogels and lower critical solution temperature (LCST) increased because of the hydrophilic group of AAc-GA and the macroporous structure. In addition, the prepared hydrogels could respond quickly to temperature and exhibited good reversible temperature-responsive characteristics.     

微晶和氢键双增强水凝胶AG/PVA/CB[7]的制备和性能

以天然高分子琼脂糖(AG)为第一物理交联网络、聚乙烯醇(PVA)为第二物理交联网络、七元瓜环(CB[7])为交联剂,制备了双网络AG/PVA/CB[7]水凝胶。使用SEM、FT-IR和XRD等手段表征AG/PVA/CB[7]水凝胶的形貌、结构以及交联方式,研究了这种水凝胶的力学性能、溶胀性能和宏观自愈性能。结果表明：这种凝胶具有高强度和自愈性,高分子链之间通过氢键和微晶共同交联使其机械性能提高;该凝胶的力学性能随着冷冻-解冻次数的增加而提高,交联剂CB[7]的加入也使其力学性能提高,循环5次后其拉伸强度为0.37 MPa,杨氏模量为 0.23 MPa,平衡溶胀率为140%。     

Cell adhesion and accelerated detachment on the surface of temperature-sensitive chitosan and poly(N-isopropylacrylamide) hydrogels

A series of temperature-sensitive poly(NIPAAm-co-CSA) hydrogels were synthesized by the copolymerization of acrylic acid-derivatized Chitosan (CSA) and N-isopropylacrylamide (NIPAAm) in aqueous solution. Their swelling properties and L929 cell adhesion and detachment behaviors were studied. It was found that poly(NIPAAm-co-CSA) hydrogels were temperature-sensitive associated with the roles of the component PNIPAAm. Most significantly, poly(NIPAAm-co-CSA) hydrogels exhibited simultaneously good swelling properties. The investigation of L929 cell adhesion and detachment of poly(NIPAAm-co-CSA) hydrogels indicated the cell adhesion and spreading was higher on the surface of poly(NIPAAm-co-CSA) hydrogels than that of PNIPAAm hydrogel at 37 degrees C due to the incorporation of CS, which having excellent cell affinity. Poly(NIPAAm-co-CSA) hydrogels showed more rapid detachment of cell sheet compared to PNIPAAm hydrogel because of the highly hydrophilic and hygroscopic nature of CS chains when reducing the culture temperature from 37 degrees C to 20 degrees C.     

快速响应的聚(N-异丙基丙烯酰胺)水凝胶的合成及性能

以羧甲基纤维素的水溶液为反应介质制备了快速响应的温度敏感性聚(N-异丙基丙烯酰胺)水凝胶。利用DSC对其相转变温度进行了表征,并测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。结果表明,在聚合/交联过程中羧甲基纤维素的存在对PN IPA水凝胶的相转变温度几乎没有影响;与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且具有较快的响应速率。     

新型温敏网络半互穿多孔水凝胶的制备及其固定化酶的研究

以甲基丙烯酸羟乙酯(Hydroxyethyl methacrylate,HEMA)、N,N-二乙基丙烯酰胺(N,N-diethyl-Acrylamide,DEAAm)为原材料,通过自由基聚合反应合成一种温敏型多孔水凝胶,经接枝反应引入乙烯基,制得新型温敏网络半互穿多孔水凝胶。利用红外光谱(IR)、核磁共振碳谱(13 C NMR),结合扫描电镜(SEM)表征中间产物和最终产物。采用称重法研究最终产物的溶胀、去溶胀动力学,分析其溶胀性能和温度响应性。运用点击反应原理,以新型温敏网络半互穿多孔水凝胶固定肌酸激酶。釆用BCA(Bicinchoninic Acid)蛋白试剂盒法测定酶的固载量,pH法测定酶活。结果表明,新型温敏水凝胶合成成功,肌酸激酶的平均固载量为24.77mg·g~(-1),肌酸激酶的平均酶活为9.67U·g~(-1)。该新型温敏水凝胶对肌酸激酶具有良好的选择性和温度响应性,对实现肌酸激酶的高效利用具有很好的借鉴意义。     

Polyacrylamide hydrogels and semi-interpenetrating networks (IPNs) with poly(N-isopropylacrylamide): Mechanical properties by measure of compressive elastic modulus

Semi-IPN hydrogels (based on cross-linked polyacrylamide having poly(N-isopropylacrylamide) (PN1PAAm) inside) were synthesized and their properties, such as swelling ratio and compressive elastic moduli, were studied at several temperatures. Equilibrium swelling ratios of semi-IPN markedly decreased due to the presence of less hydrophilic PNIPAAm chains. The semi-IPN presented greater elastic modulus when compared to the cross-linked PAAm hydrogel. The effect was explained as being an additional contribution of the PNIPAAm chains, which collapsed around the PAAm networks, to the elastic modulus. It was pointed out that the PAAm networks support the collapsed chains. According to the results presented in this work, semi-IPN hydrogels present better mechanical properties than the PAAm hydrogel, mainly when the PNIPAAm chains are in a collapsed state.     

Preparation and characterization of novel biocompatible cryogels of poly (vinyl alcohol) and egg-albumin and their water sorption study

Polyvinyl alcohol (PVA) and egg albumin are water-soluble, biocompatible and biodegradable polymers and have been widely employed in biomedical fields. In this paper, novel physically cross-linked hydrogels composed of poly (vinyl alcohol) and egg albumin were prepared by cyclic freezing/thawing processes of aqueous solutions containing PVA and egg albumin. The FTIR analysis of prepared cryogels indicated that egg albumin was successfully introduced into the formed hydrogel possibly via hydrogen bonds among hydroxyl groups, amide groups and amino groups present in PVA and egg albumin. The gels were also characterized thermally and morphologically by DSC and SEM-techniques, respectively. The prepared so called ‘cryogels’ were evaluated for their water uptake potential and influence of various factors such as chemical architecture of the spongy hydrogels, pH and temperature of the swelling bath were investigated on the degree of water sorption by the cryogels. The effect of salt solution and various simulated biological fluids on the swelling of cryogel was also studied. The in vitro biocompatibility of the prepared cryogel was also judged by methods such as protein (BSA) adsorption, blood clot formation and percentage hemolysis measurements.     

Radiation preparation of PVA/CMC copolymers and their application in removal of dyes

Copolymer hydrogels composed of poly(vinyl alcohol) (PVA) and carboxymethyl cellulose (CMC) was prepared by using electron beam irradiation as crosslinking agent. The copolymers were characterized by FTIR and the physical properties such as gelation. The thermal behavior and swelling properties of the prepared hydrogels were investigated as a function of PVA/CMC composition. The factors effecting adsorption capacity of acid, reactive and direct dyes onto PVA/CMC hydrogel, such as CMC content, pH value of the dye solution, initial concentration and adsorption temperature for dyes were investigated. Thermodynamic study indicated that the values the negative values of ΔH suggested that the adsorption process is exothermic. The value of ΔH (38.81 kJ/mol) suggested that the electrostatic interaction is the dominant mechanism for the adsorption of dyes on hydrogel.