【作者】 吴疆；

【导师】 陈圣福；

【作者基本信息】 浙江大学 ， 应用化学， 2014， 博士

【摘要】 抗蛋白质非特异性吸附材料可以有效减少材料表面的蛋白质吸附从而提高材料的生物相容性。传统的聚乙二醇(PEG)材料在复杂的生物环境中,其长效性和稳定性非常有限,已有研究发现PEG分子能够激活部分人体的免疫,PEG修饰的蛋白质药物活性急剧下降。而两性离子材料如聚甲基丙烯酰氧基乙基磷酰胆碱(pMPC).聚磺基甜菜碱甲基丙烯酸酯(pSBMA)和聚羧基甜菜碱甲基丙烯酸酯(pCBMA)越来越多地被证实比PEG有更加长效的生物相容性。因此研究PEG以及两性离子材料抗蛋白质非特异性吸附的机理不仅有助于更加了解材料抗蛋白质吸附的机制,优先选择合适的抗蛋白质非特异性材料,更有助于设计并发现更优秀的抗蛋白质非特异性吸附材料。本论文围绕抗蛋白质非特异性吸附材料的内在机理和特性,首先创建了低场核磁方法学考察PEG和具有代表性的两性离子聚合物pSBMA不同的水合能力,以及大分子PEG与蛋白质的作用情况；进一步探索溶液状态下长短链PEG以及pSBMA对比PEG和蛋白质不同的作用特性；最后设计蛋白质在水凝胶中的扩散直接体现PEG和SBMA与蛋白质不同的作用力。主要内容和结论包括以下六个部分：1、利用低场核磁采集不同浓度的PEG水溶液CPMG序列反演得到T2横向弛豫时间,定量计算PEG紧密结合的水分子量,结果表明一个EG单元结合一个水分子,并得到DSC方法验证,同时跟踪聚合物的溶解过程中自身链段的物理行为。2、利用低场核磁T2反演技术定量研究pSBMA和PEG不同的水合能力以及材料周围水分子的状态。证明pSBMA每个单元比PEG结合更多的水(SB-8个,EG-1个),同时pSBMA的水合层水分子排列比PEG更加紧密,而饱和水层形成后pSBMA周围的水分子比PEG周围的水分子更自由。3、利用低场核磁T2反演技术定量研究不同分子量的PEG与蛋白质的相互作用,发现PEG与蛋白质在溶液中存在较强的相互作用,且该相互作用和PEG分子量以及蛋白质类型相关,并定量计算PEG与蛋白质的结合常数在104到105M-1。4、通过荧光、高场核磁共振、原子力显微镜进一步研究不同分子量PEG与蛋白质相互作用的方式及对结合区域的影响。验证了PEG和蛋白质的相互作用与分子量密切相关,小分子量PEG (400Da)由于较高的亲水性和较短的分子链,无法与蛋白质形成多点接触,从而急剧降低了和蛋白质分子的相互作用力。5、通过荧光、高场核磁共振、原子力显微镜对比研究大分子量的pSBMA和PEG与蛋白质分子不同的相互作用。证明pSBMA和蛋白质的相互作用不明显,而PEG和蛋白质之间的疏水相互作用有可能导致蛋白质分子结构的变化。6、研究荧光标记蛋白质在PEG和SBMA不同配比的水凝胶中的扩散行为,发现蛋白质分子在PEG水凝胶中扩散的速度明显低于在SBMA水凝胶中的扩散速度,进一步证明了PEG和蛋白质存在较大的相互作用,而SBMA与蛋白质几乎没有相互作用。更多还原

【Abstract】 Nonfouling materials could effectively prevent nonspecific protein adsorption on the surface and thus improve the biocompatibility. Polyethylene glycol (PEG) is a well-known nonfouling materials in biomedical applications. However, its long-term effectiveness and stability is very limited especially in biological applications due to the extremely complicated internal environment. It is observed that certain people could generate immunoresponse to PEG and the PEG modification would dramatically decrease the activity of protein. Nowadays, zwitterionic materials, poly(2-methacryloyloxyethyl phosphorylcholine)(pMPC), poly(sulfobetaine methacylate)(pSBMA) and poly(carboxybetaine methacylate)(pCBMA), have demonstrated excellent resistance to nonspecific protein adsorption and long-term biocompatibility over PEG. A comprehansive understanding of the difference of nonspecific protein adsorption mechanism between PEG and zwitterionic materials will not only help us to provide the insight of the protein resistance and also select and design more appropriate materials to resist nonspecific protein adsorption. This paper mainly focuses on two typical nonfouling materials through comparatively investigating the hydration water layer of PEG and the representive of zwitterionic polymer pSBMA, as well as the binding behavior of PEG and pSBMA with protein, and last the diffusion behavior of the protein in PEG, PEG-pSBMA mixed and pSBMA hydrogels. The main contents and conclusions of this dissertation include the following six parts:1. The strong interaction between water molecules and PEG was investigated through each T2component in water/PEG mixtures using multi-exponential inversion of T2relaxation time measured by the Can—Purcell—Meiboom—Gill (CPMG) sequence of low-field nuclear magnetic resonance (LF-NMR). Results show that about one water molecule is tightly bound with one ethylene glycol (EG) unit. This result was also supported by the endothermic behavior of water/PEG mixtures measured by differential scanning calorimetry (DSC).2. Eight water molecules are tightly bound with one sulfobetaine (SB) unit, and additional water molecules over8:1ratio mainly swell the pSBMA matrix, which is obtained through the measurement of T2relaxation time by LF-NMR. This result was also supported by the endothermic behavior of water/pSBMA mixtures measured by DSC. Furthermore, by comparing both results of pSBMA and PEG, it is found that (1) the hydrated water molecules on the SB unit are more tightly bound than on the ethylene glycol (EG) unit before saturation, and (2) the additional water molecules after forming the hydration layer in pSBMA solutions show higher freedom than those in PEG.3. The interactions of bovine serum albumin (BSA) and lysozyme (LYZ) with different molecular weight (MW) PEGs was investigated through the T2relaxation time of PEGs measured by LF-NMR. The results show that a large number of PEG molecules could associate with protein molecules with association constants in the range～104to105M-1.4. The interactions between PEG and proteins in aqueous solution were investigated using fluorescence spectroscopy, atomic force microscopy (AFM), and nuclear magnetic resonance (NMR). The molecular weight effect of each on PEG-protein interactions as well as binding characteristics were examined. In contrast to too long and too short PEG chains, collective results indicated that the PEG with optimal MW exhibits the highest interacting with proteins.5. The interactions between two model proteins (BSA and LYZ) and two typical antifouling polymers of PEG and pSBMA in aqueous solution were investigated using fluorescence spectroscopy, AFM and NMR. Collective data clearly demonstrate the existence of medium interactions between PEG and proteins through multiple weak hydrophobic interaction, while there are no detectable interactions between pSBMA and proteins.6. The protein-polymer interaction was investigated through the diffusion behavior of the labeled protein in the PEG, PEG-pSBMA mixed and pSBMA hydrogel. It was observed that the protein diffusion rate through PEG hydrogel is much smaller than pSBMA hydrogel, indicating the interaction between the protein-PEG is stronger than protein-pSBMA.更多还原