【作者】 李琳；

【导师】 辛忠；

【作者基本信息】 华东理工大学 ， 材料化学工程， 2011， 博士

【摘要】 生物医用材料(biomedical material)是用于对生物体进行诊断、治疗、修复或替换其病损组织、器官或增进其功能的新型高技术材料。磷酰胆碱(PC)是组成细胞膜的基本单元(如卵磷脂分子等)的亲水端基,在外层细胞膜中占重要地位,它直接影响生物体细胞如何与外界发生作用。基于仿细胞膜结构出发设计合成的磷酰胆碱聚合物因其具有良好的生物相容性而备受关注,为人们寻找生物相容性材料开辟了新途径。本论文拟创制新型含磷酰胆碱功能基团的聚合物,并对该类聚合物进行较为系统全面的性能表征,以期能够为不同生物医学领域(如人造器官、角膜接触镜等)新材料的开发和应用提供思路和支持,现取得研究结果如下：首先,经过环构化、氧化、缩合、开环四步反应,合成了磷酰胆碱单体2-甲基丙烯酰氧乙基磷酰胆碱(MPC)。环构化反应中以三氯化磷和乙二醇为原料,合成了中间体2-氯-1,3,2-二氧磷杂环戊烷(CDP),氧化反应是以氧气为氧化剂,对CDP进行氧化,制备了中间体2-氯-2-氧-1,3,2-二氧磷杂环戊烷(COP),缩合反应是以甲基丙烯酸羟乙酯(HEMA)和COP为原料,合成了中间体2-烷基-2-氧-1,3,2-二氧磷杂环戊烷(OPEMA),最后以三甲胺为开环试剂,经过对OPEMA的开环反应合成了MPC。对各步反应条件进行优化确定的最佳合成条件为：环构化反应在温度0℃,三氯化磷与乙二醇摩尔比1.1：l,滴加速度0.7mL/min时,产品收率为80%；氧化反应中,提高氧气流量可以缩短反应时间,但容易造成开环反应生成副产物,在反应温度15℃,氧气流量5mL/min时,产品收率最高(67%)；在较高温度下不利于缩合反应进行,温度降至-16℃时,收率可以达到89%；开环反应中,当投料摩尔比为OPEMA:N(CH3)3=1:1.9时,产品MPC收率达到最高77%。其次,进行了含MPC二元共聚物的制备与性能研究。采用自由基聚合制备了MPC与甲基丙烯酸丁酯(BMA)的共聚物：PMB10(投料量nMPC=10%)、PMB20(投料量nMpc=20%)及MPC与甲基丙烯酸异辛酯(EHMA)的共聚物：PMEH10(投料量nMPC=10%)、PMEH20(投料量nMPc=20%),考察了共聚物薄膜的生物相容性及溶胀特性。牛血清蛋白(BSA)吸附性能测试显示,蛋白质吸附量随着磷酰胆碱在聚合物中含量的升高而降低,PMEH20薄膜对BSA的吸附量比均聚物薄膜PEHMA降低了73.6%；血小板黏附性能测试显示,含有MPC的PMEH20薄膜有更好的抗血小板黏附性；用菲克(Fickian)动力学模型描述共聚物薄膜溶胀初期的过程,PMB20、PMEH10、PMEH20薄膜在溶胀初期均属于菲克溶胀过程,说明水分了在聚合物中的扩散控制着聚合物溶胀过程,PMB10薄膜在溶胀初期属于非菲克(non-Fickian)溶胀过程,水分子扩散与高分子链段松弛共同控制着溶胀过程；用Schott动力学模型描述聚合物薄膜的整个溶胀过程,发现磷酰胆碱含量越高的聚合物其初始溶胀速率和最大平衡溶胀程度越大。再次,将含磷酰胆碱基团的共聚物PMEH20以不同质量百分比(5wt%、10wt%、15wt%)添加到基材聚氨酯(SPU)中,制备了共混薄膜SP-5、SP-10、SP-15。牛血清蛋白吸附性测试显示SP-15薄膜比空白SPU薄膜对BSA吸附量减少了81.7%,血小板黏附性能测试显示PMEH20的加入能够有效抑制聚氨酯薄膜对血小板的黏附；静态水接触角测试发现,共混膜中的不同极性高分子链段呈不均匀分布,进一步通过动态水接触角测试分析,随着PMEH20添加量的增加,前进角逐渐增大,而后退角逐渐减小,说明共混膜表面高分子链段在极性环境(水)中可以发生重排,磷酰胆碱基团在水环境中可以分布于共混膜表面,发挥其生物相容性作用；薄膜力学性能测试显示随着PMEH20的添加量增多,薄膜力学性能先增大,后降低,SP-10薄膜材料的综合力学性能最好；考察了SP-10薄膜的稳定性,经3wt%氯化钠溶液、30wt%双氧水、1wt%高锰酸钾水溶液、浓盐酸、20wt%硫酸、30wt%氢氧化钠溶液浸泡处理后,其质量损失均在0.2%以下,其稳定性与空白SPU相当；用热失重分析(TGA)考察了共混膜的热稳定性,发现在5wt%-10wt%的添加范围内,基体聚氨酯的热稳定性基本不受影响。第四,以MPC、甲基丙烯酸甲酯(MMA)、甲基丙烯酰氧丙基三(三甲基硅氧烷基)硅烷(TRIS)为原料制备了Poly(MMA-co-MPC-co-TRIS)三元共聚物(PMMT),以期在维持原有材料高透明性、透氧性的同时解决材料表面蛋白质沉积等问题。牛血清蛋白吸附性测试显示,对于PMMT-2薄膜(MPC摩尔含量16.6%),其蛋白质吸附量比不含MPC的PMMA和Poly(MMA-co-TRIS)聚合物薄膜分别下降了75.3%和76.8%；血小板黏附测定同样表明三元共聚物表面黏附的血小板细胞数量显著降低,生物相容性有了很大提高；水接触角及溶胀度测试显示,MPC的添加可以显著改善薄膜的界面润湿性,且PMMT-2的平衡含水量达到了55%；PMMT-、PMMT-2薄膜在全部可见光范围内具有较高的透光性,最高透光率超过97.0%；利用DSC分析了PMEH0、PMEH20、PMMT-1、PMMT-2四种MPC共聚物中水的状态,发现MPC含量更高的聚合物中,可冻结水的比例也更高,由此推测,正是由于其吸收的水分中可冻结水的比例高,在与蛋白质相接触时,排列在材料表面最外层的可冻结水使蛋白质自身的水化层不被破坏,起到了稳定蛋白质构象的作用,从而减少了蛋白质在材料表面的吸附。最后,以MPC、甲基丙烯酸羟乙酯(HEMA、甲基丙烯酰氧丙基三(三甲基硅氧烷基)硅烷(TRIS)为原料制备了含MPC的Poly(HEMA-co-MPC-co-TRIS)三元共聚物(PHMT),以期提高表面润湿性的同时解决材料表面蛋白质沉积等问题。通过水接触角测试发现,在PHMT三元共聚物表面存在着链段的重排现象,在极性环境(水)中,磷酰胆碱基团可以翻转重排于薄膜表面,使表面接触角从114.0°下降到24.2°,显著改善了薄膜的表面润湿性；PHMT薄膜表面吸附的牛血清白蛋白(BSA)、牛血清纤维蛋白(Fib)、牛血清球蛋白(IgG)三种蛋白质的量比不含MPC的聚合物薄膜明显减少,即MPC基团在聚合物中的引入可以显著提高材料表面抗蛋白质沉积的性能；用AFM对旋涂法制备的PHMT薄膜表面形貌进行考察,发现其在玻璃基片上可以形成平整光滑的表面,粗糙度Rq=1.01nm,并且在全部可见光范围内(400-700nm)透光率均超过93.0%；由于MPC基团的引入,PHMT共聚物在30℃时的平衡含水量达到63%,比不含MPC的聚合物有显著提高。更多还原

【Abstract】 Biomedical materials are the advanced materials being studied and developed recently, which could diagnose, treat and repair the organism or being used as the artificial organs. The lipid bilayer membrane of many cells types have an asymmetric lipid composition, the zwitterionic lipid phosphatidylcholine is the major component. The bio-inspired polymer containing phosphorylcholine functional group has been focused due to its excellent biocompatibility and anti-biofouling properties. In this study, in order to provide a new way and support to the development and application of biomaterials (such as artificial organs, contact lens, etc), novel polymers containing phosphorylcholine functional group were prepared and characterized. The main results are as follows:Firstly,2-methacryloyloxyethyl phosphorylcholine(MPC) was synthesized through four steps. In the first step,2-chloro-l,3,2-dioxaphospholane (CDP) was prepared by the reaction of ethylene glycol with phosphorus trichloride. In the second step, CDP was subsequently oxidized by oxygen to 2-chloro-2-oxo-l,3,2-dioxaphospholane (COP). In the third step, the synthesis of 2-(2-oxo-l,3,2-dioxaphospholoyloxy) ethyl methacrylate (OPEMA) was achieved by the reaction of COP with 2-hydroxyethyl methacrylate. In the fourth step, MPC was prepared by the reaction of OPEMA with triethylamine through the ring cleavage reaction. The optimized process was accomplished as follows:to give a yield of 80%for the synthesis of CDP, the reaction temperature was 0℃, the mole ratio of phosphorus trichloride: ethylene glycol=1.1:1, the dropwise speed of ethylene glycol was 0.7mL/min; in the second step, the number of oxidizing agents available for this is limited owing to possible cleavage of the ring, the highest yield of COP was achieved on the reaction condition:reaction temperature 15℃, flow rate of oxygen 5mL/min; in the third step, the synthesis of OPEMA at low reaction temperature(below-15℃) could give a higher yield(more than 80%); the increasing in the mole ratio of triethylamine to OPEMA was helpful to increase the yield of MPC, when the ratio was 1.9:1, the yield was the highest.Secondly, copolymers poly (MPC-co-BMA) and poly (MPC-co-EHMA) were prepared and characterized. MPC was copolymerized with butyl methacrylate(BMA) and 2-ethylhexyl methacrylate(EHMA), respectively, using 2,2’-azodiisobutyronitrile (AIBN) as initiator. They were PMB10, PMB20, PMEH10, PMEH20 according to the different feed mole fractions of MPC (10%,20%) in the polymers. The biocompatibility and swelling capacity were studied. The protein adsorption measurement showed that the amount of adsorbed proteins was reduced by the introduction of MPC in the polymers, for PMEH20 membrane, the amount of adsorbed proteins was reduced 73.6% compared with PEHMA homopolymer membrane. The platelet adhesion measurement showed that no evidence of any blood platelet attachment was apparent on the MPC containing polymer membranes (PMEH20). To study the initial stage of the water diffusion process in the polymers, Fickian diffusional mechanism was adopted. The diffusional mechanism in PMB20, PMEH10, and PMEH20 was Fickian, the diffusion of water control the rate of water content. While the water transport mechanism becomes non-Fickian in PMB10, both diffusion and polymer relaxation control the overall rate of water content. For extensive swelling, Schott second order dynamic equation was adopted, and it was found that both the maximum swelling and the initial swelling rate were increased due to the introduction of MPC in the polymers.Thirdly, the copolymer PMEH20 was blended with a segmented polyurethane (SPU), the blended membranes were SP-5, SP-10 and SP-15 according to the different weight percentage of PMEH20 (5%,10%,15%) in the membranes. The test of protein (bovine serum albumin) adsorption showed that the blended membrane SP-15 adsorbed fewer proteins than the blank SPU membrane (reduced 81.7%); the platelet adhesion measurement showed a decreased amount of platelet with an increasing amount of PMEH20 in the blended membrane. There existed unequal distribution of the polar and apolar polymer chains in the blended polymers as measured by the static water contact angle, and the dynamic contact angle measurement showed that the advancing angle increased and the reducing angle decreased with the increasing of PMEH20 in the blended membranes, which indicated that the surface of blended membranes exhibit surface rearrangement under different environmental conditions, the phosphorylcholine groups could rearranged on the upper surface of the membrane in the water environment and as a result increase the biocompatibility of the polymer. The mechanical properties of the SPU membranes were determined by tensile stress-strain measurements, and the SP-10 membrane showed a better mechanical property. The stability of SP-10 was evaluated by immersing the films in different solusions (3wt%NaCl,30wt%H22O2, lwt%KMnO4, HC1,20wt%H2SO4,30wt%NaOH) for a certain time, and the mass loss rate of SP-10 was all below 0.2%, it was comparable to the blank SPU film.As measured by TGA, it was found that in the range of 5wt%-10wt%(the weight percentage of PMEH20 in the blended films), there was no big difference of the thermal stability between the SPU-based films.Fourthly, a novel poly (methyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine-co-tris(trimethylsiloxy)-3-methacryloxypropylsilane) terpolymer (PMMT) was synthesized and the anti-biofouling properties were studied in order to evaluate the potential of this silicone hydrogel to be used as contact lens material. Protein adsorption measurement showed that for PMMT-2 membrane (MPC:16.6mol%), the amount of adsorbed proteins was decreased by 75.3%and 76.8%compared with the MPC free polymers poly methyl methacrylate (PMMA) and poly (methyl methacrylate-co-tris (trimethylsiloxy)-3-methacryloxypropylsilane) (PMT), respectively. SEM pictures showed clearly that the terpolymer films suppressed the adhesion of platelets, the biocompatibility was increased dramatically. The introduction of MPC in PMMT-1 and PMMT-2 increased the wettability of the surface dramatically. The equilibrium water content of PMMT-2 membrane reached 55%, which may offer comfortable wear feeling. PMMT-1 and PMMT-2 films exhibited high transparency in the visible light wave range (the highest transmittance was 97.0%). Water structure in polymers was determined by differential scanning calorimetry (DSC), the polymers containing more amount of MPC possessed more freezing water content, which indicated that MPC containing polymers take up large quantities of freezing water and that proteins adsorbed on these copolymers assume conformations similar to those of the native proteins while the corresponding MPC free polymers induce significant changes in conformation. It was concluded that the water layer associated with the MPC containing surface preserves the native conformation of adsorbed proteins.Finally, a novel poly 2-hydroxyethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine-co-tris(trimethylsiloxy)-3-methacryloxypropylsilane (PHMT) terpolymer was synthesized and the anti-biofouling properties were studied in order to evaluate the potential of this polymer to be used as contact lens material. The phosphorylcholine unit played an important role in the terpolymer:increasing both the surface hydrophilicity and the anti-biofouling properties of the original material. Water contact angle measurements suggested that the phosphorylcholine head groups could rearrange on the upper surface of the TRIS containing polymer in the water environment, improving the wettability of the surface. Compared with MPC free polymer poly 2-hydroxyethyl methacrylate-co-tris(trimethylsiloxy)-3-methacryloxypropylsilane membrane, lower protein adsorption (for three typical plasma proteins BSA, Fib and IgG) was observed on the surface of PHMT polymer. As observed by AFM, smooth surface (Rq=1.01nm) was formed by spin coating method from the terpolymer solution, and the equilibrium water content reached 63%, much higher than the polymers without MPC unit, which may offer comfortable wear feeling. Moreover, PHMT film exhibited high transparency in the visible light wave range (relatively constant at approximately 94.0%).更多还原