【作者】 王雪飞；

【导师】 沈家骢； 计剑；

【作者基本信息】 浙江大学 ， 材料学， 2010， 博士

【摘要】 随着蛋白质基因技术、组织再生医学及药物科学的发展和交叉,应用于组合装置的先进药物控释涂层研究已成为生物医用植入体和组织再生材料研究的重要内容。本论文将弱聚电解质电荷密度的pH值依赖性和生物大分子多层膜层间扩散机制有机结合,探索通过深入研究pH值调控生物大分子多层膜指数增长行为的基本规律,建立采用pH增强的指数增长多层膜快速构建负载基因和寡肽的薄膜涂层材料的新方法。本论文首先研究了具有显著多层膜层间扩散特性的聚赖氨酸（PLL）与透明质酸（HA）和DNA在不同pH条件下的组装行为。研究结果显示,pH调控可有效增强PLL/HA和PLL/DNA多层膜的指数增长行为,能够实现生物大分子多层膜的快速构建。但PLL与弱聚阴离子HA和强聚阴离子DNA组装时表现出不同的规律:对于PLL/HA组装,单独降低HA溶液pH,或单独升高PLL溶液pH,或降低HA溶液pH的同时升高PLL溶液pH,均能加快PLL/HA多层膜的指数增长;对于PLL/DNA组装,PLL溶液pH在PLL/DNA多层膜的增长中起主导作用,而DNA溶液pH对多层膜增长行为的影响较小。PLL和DNA在较高pH（pH 9.5或10.0）下交替组装可以实现DNA多层膜的快速增长。这一规律显示弱聚电解质的电荷密度变化是影响多层膜pH增强指数增长特性的主要因素。依据pH值对PLL/DNA多层膜指数增长行为的影响规律,建立了基因薄膜涂层材料的快速制备技术。PLL/DNA 10.0/4.6多层膜在7.5双层（PLL最外层）时,多层膜内PLL和DNA质量总和可达121.2μg/cm²。调节组装溶液pH可以调节多层膜内聚电解质比例。增加两种组装溶液间pH差值,可以提高多层膜的N/P比（聚阳离子中的自由氨基与DNA中磷酸根的摩尔比）。多层膜的N/P比也随着最外层PLL组装溶液pH的升高而增大。PLL/DNA 9.5/5.0和10.0/4.6多层膜在7.5双层时,N/P比分别可达6.3和9.8。相应地,PLL/DNA多层膜释放的DNA复合物的尺寸随N/P比增加而减小。（PLL/DNA 10.0/4.6）₇ PLL 10.0多层膜的N/P比达到9.8,释放的DNA复合物的直径低至151 nm。具有较高DNA含量和N/P比的多层膜释放的质粒DNA具有相对较高的基因转染水平。（PLL/DNA 9.5/5.0）₇ PLL9.5和（PLL/DNA 10.0/4.6）₇ PLL 10.0多层膜释放的质粒DNA转染细胞后,转染效率分别为10.43%和9.67%,而（PLL/DNA7.2/7.2）₇ PLL 7.2多层膜的细胞转染效率仅为0.18%。这种含有较多DNA和较高N/P比的多层膜为提高原位基因传递体系的转染效率提供了一种新方法。依据pH值对多肽类物质在PLL/HA多层膜中扩散行为的增强作用,建立了负载HIV-1转录反式激活因子（TAT）的薄膜涂层体系。研究表明TAT能够扩散进入整个PLL/HA指数增长多层膜。多层膜负载的肽含量不仅可通过调节多层膜厚度,也可通过调节多层膜组装pH和TAT载入pH实现调控。当TAT载入pH在9.5时,（PLL/HA9.5/2.9）₅多层膜负载的TAT密度高达25.0μg/cm²。与TAT和HA交替组装方法相比,TAT扩散进入（PLL/HA 9.5/2.9）₅多层膜不仅能够负载高密度的肽,而且可实现寡肽的有效释放。细胞培养实验表明多层膜负载的TAT仍具有穿越Hep G2细胞膜的能力。在细胞内吞实验中,功能化（PLL/HA 9.5/2.9）₅ TAT 9.5多层膜比10倍量自由TAT肽更能有效转导细胞。这些结果显示寡肽扩散进入快速增长多层膜的负载方式为原位持续传递肽提供了一种有效方法。更多还原

【Abstract】 With the development and interdisciplines of protein technology, gene technology, tissue regeneration medicine and pharmacy, advanced drug controlled release coatings applied in drug/medical devices becomes an important issue of biomedical implants and tissue regenerative materials. This thesis explores to establish a facile method to rapidly construct multilayers embedded with gene or oligo-peptide via the synergetic action of pH tunable charge density and diffusivity of the weak natural polyelectrolytes.The exponential growth behaviors of multilayers of the diffusible poly-L-lysine （PLL） with hyaluronic acid （HA） or DNA at different pH are investigated. The data indicate that pH controlled assembly can enhance the exponential growth behavior of PLL/HA and PLL/DNA multilayers, and realize the rapid fabrication of biomacromolecule multilayers. As HA is a weak polyelectrolyte and DNA is a strong polyelectrolyte, the characteristic growth behavior is different between PLL/HA and PLL/DNA multilayers constructed via pH controlled assembly. PLL/HA exponential growth is amplified by decreasing pH of HA solution or increasing pH of PLL alone or simultaneously. In PLL/DNA systems, the pH of PLL solution exerts a dominant role in the multilayer growth while that of DNA has little effect. The rapid growth of multilayer embedded with DNA can be achieved at high pH （pH 9.5 and 10.0）. The growth behavior characteristic indicates that the change of charge density of weak polyelectrolyte is the main effect to influence the pH amplified exponential growth of the multilayers.Based on the pH effect on the exponential growth behavior of PLL/DNA multilayer, rapid fabrication of gene coating is established. PLL/DNA 10.0/4.6 film （PLL and DNA are deposited at pH 10.0 and pH 4.6, respectively） could reach 121.2μg/cm² within 7.5 bilayers. The N/P ratios （molar ratio of free amino groups in polycation to phosphate groups in DNA） within the multilayers are proved to be elevated by increasing either the pH difference between the two deposition solutions or the pH value of the outmost deposition solution. The N/P ratios of PLL/DNA 9.5/5.0 and 10.0/4.6 are respectively 6.3 and 9.8 within 7.5 bilayers. The PLL/DNA multilayers are degraded as exposed to trypsin solution and the mean diameters of the degraded DNA complexes decrease when the N/P ratio increases. The diameter of DNA complexes degraded from PLL/DNA 10.0/4.6 film reaches 151 nm. Relatively higher transfection level is achieved for plasmid degraded from the PLL/plasmid 9.5/5.0 and 10.0/4.6 films, and the transfection efficiency are 10.43% and 9.67%, respectively, while the transfection efficiency in PLL/plasmid 7.2/7.2 multilayer is 0.18%. The film with more DNA and higher N/P ratio might provide a new method to enhance transfection in localized gene delivery system.Based on the enhancement effect of pH on the diffusion behavior of polypeptide, coating systems incorporated with a trans-activating transcriptional factor （TAT） peptide are established. The result indicates that TAT could diffuse throughout the exponentially growing PLL/HA film. The amount of peptide embedded within multilayer could be adjusted not only by the multilayer thickness but also by the multilayer assembly pH and TAT loading pH. The density of TAT loaded into the （PLL/HA 9.5/2.9）₅ film can reach 25.0μg/cm² when TAT loading pH is 9.5. Compared with direct layer-by-layer assembly of TAT and HA, the postdiffusion of TAT into （PLL/HA 9.5/2.9）5 film can be loaded much more peptide and realize the sustained release of oligo-peptide. The cell culture results indicate that the TAT embedded within the film maintains the ability to traverse across the Hep G2 cell membrane. The functionalized （PLL/HA 9.5/2.9）₅ TAT 9.5 film is more efficient than the 10-fold more amount of free TAT peptide in the TAT uptake test. The postdiffusion of oligo-peptide within an exponential growth multilayer can serve as an effective approach for localized and sustained peptide delivery.更多还原