【作者】 杨亮；

【导师】 陆大年；

【作者基本信息】 东华大学 ， 纺织化学与染整工程， 2013， 博士

【摘要】 细菌纤维素是一类性能优异的生物高分子材料,在高分子功能材料研究领域中较为活跃,尤其是细菌纤维素增强复合材料的制备表征及性能研究颇受关注。细菌纤维素作为增强体制备的细菌纤维素复合材料种类繁多,性能各异,具有良好的应用前景,尤其在生物医学方面。细菌纤维素含有大量的羟基,具有良好的亲水性,与其他水溶性的高分子容易发生氢键结合,因而细菌纤维素增强水溶性高分子复合材料在细菌纤维素增强复合材料中的研究较为突出。目前细菌纤维素增强水溶性高分子复合材料的制备方法主要有以下三类：第一类是化学制备法,将细菌纤维素经过化学改性之后制备其复合材料；第二类是生物制备法,在细菌纤维素培养过程中加入其它水溶性高分子制备细菌纤维素增强复合材料；第三类是物理制备法,如冻融循环法、冷冻真空干燥法等,这两类方法在细菌纤维素增强水溶性高分子复合膜的制备中应用广泛。然而经过冻融法和冻干法制得细菌纤维素增强水溶性高分子复合材料容易吸水溶胀,降低了其机械性能,限制了其使用范围,另外,冻融循环法和冷冻真空干燥法对仪器的要求较高,成本也较大,因此,探索细菌纤维素增强水溶性高分子复合材料的新型制备方法,使得复合材料的性能进一步提高,而制备成本较低的理想方法是非常必要和迫切的。同时,制备性能、用途各异的细菌纤维素增强水溶性高分子多功能纳米复合材料已越来越被重视。为了进一步充分开发利用细菌纤维素增强水溶性高分子纳米复合材料,扩展其应用领域,应从以下两个方面着手：一是应对所需性能的细菌纤维素增强水溶性高分子纳米复合材料进行制备方法研究；二是应对细菌纤维素增强水溶性高分子纳米复合材料的应用进行开发研究。本课题首先探索得出细菌纤维素增强水溶性高分子复合材料的一种简易制备方法,即在过饱和的无机盐溶液中使用醛交联剂通过化学交联制备得到细菌纤维素增强水溶性高分子复合材料,包括细菌纤维素增强聚乙烯醇(BC/PVA)复合材料、细菌纤维素增强羧甲基纤维素钠(BC/CMC-Na)复合材料以及细菌纤维素增强黄原胶(BC/XG)复合材料。其次,对制得细菌纤维素增强水溶性高分子复合材料的性能进行表征研究,同时探索其在蛋白药物承载方面的初步应用。使用化学交联法制备细菌纤维素增强水溶性高分子复合材料,如BC/PVA、 BC/CMC-Na及BC/XG复合材料,为制备细菌纤维素增强复合材料提供了新思路,制得复合材料对蛋白药物的吸附及释放性能拓展细菌纤维素复合材料在生物医学方面的应用。首先,使用甲醛作为交联剂在过饱和氯化钠溶液中交联制备细菌纤维素／聚乙烯醇(BC/PVA)复合凝胶膜。通过对BC/PVA复合凝胶膜红外光谱特性、溶胀性能、力学性能、热稳定性的研究讨论了化学交联对BC/PVA复合凝胶膜性能的影响。实验结果表明甲醛作为交联剂分别与PVA和BC发生了化学交联,形成了新的化学键。化学交联后BC/PVA复合凝胶膜溶胀性能明显降低,拉伸强度和杨氏模量明显增加,而断裂伸长率降低,热稳定性明显增强。另外,作为增强体的细菌纤维素对化学交联也有明显贡献,随着BC/PVA复合凝胶膜中BC含量的增加,复合凝胶膜的溶胀性能降低,拉伸强度和杨氏模量增加。其次,对比双官能团交联剂与单官能团交联剂对BC/PVA复合凝胶膜性能的影响。参考甲醛交联制备BC/PVA复合凝胶膜的实验参数,分别使用单官能醛(甲醛、乙醛)和双官能团醛(乙二醛、戊二醛)作为交联剂通过化学交联法制备BC/PVA复合凝胶膜,在相近交联度下通过对复合凝胶膜红外光谱特性、溶胀性能、力学性能、热稳定性以及结晶性能的研究得出交联剂对复合凝胶膜性能的影响。实验结果表明在相近交联度下,双官能团醛交联剂交联制得BC/PVA复合凝胶膜溶胀性能相对较弱,拉伸强度和杨氏模量相对较高,而交联剂对BC/PVA复合凝胶膜热稳定性、结晶性能及生物降解性没有明显影响。然而通过化学交联制备得到的BC/PVA复合凝胶膜对蛋白药物牛血清白蛋白(BSA)的吸附效果和释放效果较差,可能是因为BC/PVA复合凝胶膜具有比较致密的表面结构。再次,为了提高BC/PVA复合材料对血清白蛋白的承载能力,制备了BC/PVA多孔结构复合材料和BC/PVA褶皱结构复合材料。即分别使用过饱和的氯化钠溶液和丙酮-无水乙醇处理BC与PVA混合浆液,再经过化学方法交联制备得到具有一定比表面积的BC/PVA多孔网状或褶皱状复合材料。这种BC/PVA多孔网状或褶皱状复合材料的结构对BSA的吸附提供了吸附空间,因此对BSA具有较好的吸附效果,并且对BSA的释放初期出现一定的线性释放,在创伤敷料方面有一定的应用前景。最后,为了进一步提高细菌纤维素增强水溶性高分子复合材料对BSA的吸附效果,通过化学交联法交联制备了细菌纤维素增强水溶性纤维素的复合材料,即细菌纤维素/羧甲基纤维素钠(BC/CMC-Na)和细菌纤维/素黄原胶(BC/XG)复合材料。即先用丙酮-无水乙醇分别处理BC/CMC-Na和BC/XG混合匀浆,最后将得到的复合材料在过饱和氯化钠溶液中经过化学交联,最终得到BC/CMC-Na和BC/XG复合材料。通过对所得BC/CMC-Na和BC/XG复合材料形态特征观察发现CMC-Na和XG能均匀的包覆在BC表面,并能进入到BC的网络结构中,最终形成的BC/CMC-Na和BC/XG复合材料呈现出多孔道网络结构。细菌纤维素增强的BC/CMC-Na和BC/XG多孔道网络结构复合材料提供了BSA的吸附空间,对BSA具有较好的吸附作用,同时也具有一定的释放效果,在手术后的防感染方面具有较好的应用前景。更多还原

【Abstract】 Cellulose is one of the most plentiful nature biopolymer on the Earth, being synthesized by plants and by some bacteria species as well. In particular bacterial cellulose (BC) composed of nano-sized fibril network is produced by some bacterial, such as Gluconacetobacter xylinus. The molecular formula of BC is (C6H10O5)n, having a β-1,4linkage between two glucose molecules. BC has unique structural, functional, physical and chemical properties. Recently, BC has obtained increasing attention in the research realm due to the unique properties it possesses; such as its remarkable mechanical properties in both dry and wet states, porosity, high purity and crystallinity, water absorption, excellent biodegradability and biocompatibility, therefore, BC has a wide range of applications in food, paper, and electronic industries, especially has potential application in biomedical engineering. For instance, bacterial cellulose has been used for wound dressings, vascular plants, artificial skin, and tissue engineering scaffold, and applied actively in other areas. From an environmental perspective, it is necessary to use renewable resources instead of increasingly scarce non-renewable resources. BC is produced by bacterial, so it is a green polymer. Lately, BC and functionalized BC used as reinforcement or scaffold to produce green nanocomposites, which exhibited some desirable properties, and the properties of BC based nanocomposites was extensive investigated in order to expand its applications area, especially for biomedical application.At present, there are kinds of BC based nanocompoistes with various properties, those BC based nanocomposites with various properties because of different matrix of the nanocomposites, for instance, electroconductive nanocompistes based on BC, magnetic nanocomposites based on BC, antibacterial nanocompiste BC nanocompiste, and some BC based nanocomposites possess drug loading and releasing, all of those BC based nanocomposite revealed potential applications, especially for biomedical application. So far, there are three main methods for preparing BC based nanocomposites:the first one is prepared BC based nanocomposites used modified BC, for instance, BC was modified by organic acid to improve it hydrophobicity in order to ameliorate interface adhesion between BC and hydrophobic polymer for prepare BC based nanocomposites; the second prepared BC based nanocomposites was add matrix during BC cultivate process, for instance, add polyethylene oxide (PEO), polyethylene glycol (PEG), poly(vinyl alcohol)(PVA)during BC cultivate to prepare BC/PEO, BC/PEG, BC/PVA nanocomposites, respectively; the last one is prepared BC based nanocomposites by physical or chemical method, for instance, electron beam or γ-irradiation, or physically using thermal cycling, or chemical crosslinked with different chemical crosslinkers, there are various chemical crosslinkers such as glutaraldehyde, bis(sulfosuccinimidyl),suberate, D,L-glyceraldehyde, carbodiimide, epichlorohydrin and genipin have been used to cross-link BC based nanocomposites with gelatin, chitosan, pachyman and its derivatives and elastin in aqueous or organic solutions, respectively. At present, the more popular method for preparing BC based composite membrane is freezing and lyophilization and freezing-thaw method. These methods present typical physical cross-linking, have the advantages of no residual amounts of the toxic chemical cross-linking agents left, and the resulting BC based composites membrane demonstrated desirable properties. However, both of the reezing and lyophilization and the freezing-thaw method accompanies with high consumption of energy and time, and those methods required corresponding precision apparatuses to control the rate of heating and refrigerating. In addition, most of the BC based composites membranes were aquiferous, it is easy to swell, so the mechanical strength and toughness of these nanocomposites were expected to be improved. In addition, the chemical crosslinked BC based nanocomposite in aqueous or organic solutions. However, BC nanocomposites prepared by chemical crosslinking in inorganic salt solutions are not investigated yet, and effects of the chemical crosslinkers on properties of the BC/PVA nanocomposite hydrogels were not investigated when the crosslinking degree was approximate. Therefore, it is necessary to explore an economic way to get BC based composites with promising properties, and expand its applications.BC/PVA nanocomposite hydrogels using BC as the reinforcement and PVA as the matrix materials were formed in coagulating bath of the sodium chloride and cross-linked with formaldehyde. The ATR-FTIR spectrum, ESR, mechanical, and thermal properties of the PVA and BC/PVA nanocomposite hydrogel revealed that chemical cross-linking between PVA and formaldehyde, BC and formaldehyde were achieved, respectively, and BC was conducive to the chemical cross-linking, too. The ESR of the BC/PVA nanocomposite hydrogels were decreased after chemical cross-linking, and decreased with the BC content at room temperature. It was found that the mechanical properties of the nanocomposite hydrogels were apparently affected by chemical cross-linking and the content of BC. Tensile strength and the Young’s modulus of the nanocomposite hydrogels were increased because of chemical cross-linking and with BC content, and the elongation at break was decreased. In addition, our result demonstrated that not only the PVA hydrogels but also the BC/PVA nanocomposite hydrogels, the thermal stability were remarkably enhanced because of chemical cross-linking. Briefly, the BC/PVA nanocomposite hydrogels, prepared by chemical cross-linking, exhibited promising mechanical properties and desirable thermal stability, so the BC/PVA nanocomposite hydrogels described in this study provides information for further development and optimization of a variety of nanofiber-polymer matrix composite hydrogels.BC/PVA nanocomposite hydrogels using BC as the reinforcement and PVA as the matrix materials were formed in coagulating bath of sodium chloride and cross-linked with aldehyde crosslinkers. The ATR-FTIR spectrum, ESR, mechanical, and thermal properties of BC/PVA nanocomposite hydrogel revealed that chemical cross-linking between BC/PVA and aldehyde were achieved, respectively, and BC was conducive to the chemical crosslinking, too. The crosslinking degree could be controlled by crosslinking time. It was found that the crosslinkers affect some properties of the nanocomposite hydrogels. When the crosslinking degree at approximately level, all of the ESR of the nanocomposite hydrogels was increased with temperature. The ESR of the glyoxal and glutaraldehyde cross-linked BC/PVA nanocomposite hydrogels were lower than formaldehyde and acetaldehyde cross-linked hydrogels, especially at high temperature area. It was found that the mechanical properties of the nanocomposite hydrogels were apparently influenced by crosslinkers and the content of BC. The tensile strength and Young’s modulus of the glyoxal and glutaraldehyde cross-linked BC/PVA nanocomposite hydrogels were higher than formaldehyde and acetaldehyde cross-linked hydrogels. In addition, our result demonstrated that the thermal stability of the BC/PVA nanocomposite hydrogels was remarkably enhanced after chemical cross-linking. However, the crosslinkers had slight effect on the thermal stability of the hydrogels. Meanwhile, the crystallinity degree of the nanocomposite hydrogel was hardly influened by the crosslinkers.The porous sponge-like or wrinkle sponge-like structure BC/PVA composites were prepared in coagulating bath and cross-linked with aldehyde crosslinkers. The ATR-FTIR spectroscopy and ESR tests revealed that chemical crosslinking between BC/PVA composite and glyoxal were achieved. The results of in vitro drug load and release studies revealed the porous BC/PVA composites are promising candidates as controlled drug-delivery systems.The porous sponge-like or wrinkle sponge-like structure sodium carboxymethylcellulose (BC/CMC-Na) and BC/xanthan gum (BC/XG) composites, using BC as scaffold, CMC-Na or XG as martin, were prepared in coagulating bath and cross-linked with glyoxal, respectively. The ATR-FTIR spectroscopy and ESR tests revealed that chemical crosslinking between BC/CMC-Na or BC/XG composite and glyoxal were achieved, respectively. In addition, It was demonstrated that the thermal stability of the BC/CMC-Na or BC/XG composite was enhanced after chemical cross-linking. Meanwhile, the crystallinity degree of the BC/CMC-Na or BC/XG composite was hardly influened by the chemical crosslinking. The results of in vitro drug load and release studies revealed the porous BC/CMC-Na and BC/XG composites are promising candidates as controlled drug-delivery systems.更多还原