人工髓核材料-聚乙烯醇水凝胶/聚乙烯纤维复合物的生物相容性研究*

目的评估人工髓核材料聚乙烯醇水凝胶／聚乙烯纤维复合物的生物相容性。方法根据ISO10993-1标准，采用细胞毒性试验（琼脂扩散法）、皮内刺激试验、Ame’s致突变试验、微核试验和体内植入（360天）试验对聚乙烯醇水凝胶／聚乙烯纤维复合物的生物相容性进行评估。结果聚乙烯醇水凝胶／聚乙烯纤维复合物的细胞毒性评分小于Ⅰ级，细胞生长无明显抑制现象，对皮内无刺激作用，Ames致突变试验为阴性，微核出现率为3．48‰，无致突变反应。体内植入符合植入材料生物学评价要求。结论聚乙烯醇水凝胶／聚乙烯纤维复合物具有良好的生物安全性，是一种无毒、对皮肤及肌肉、椎间隙无刺激作用的生物医用材料，在动物体内不引起排异反应，可应用于临床。     

人工髓核材料-聚乙烯醇水凝胶的溶胀性能研究

利用冷冻-解冻法制得聚乙烯醇(PVA)水凝胶弹性体,研究了其用于人工髓核材料的溶胀特性,以及聚乙烯醇浓度、溶胀温度、溶胀体系的pH值对其溶胀性能的影响,采用扫描电镜对其微观形貌进行了观察,并对其溶胀动力学进行了探讨。结果表明,聚乙烯醇水凝胶是一种多孔网状结构,网络孔径大小与水凝胶中聚乙烯醇的含量有关;增加聚乙烯醇的浓度,提高溶胀温度以及溶胀体系的pH值,其平衡溶胀率减小;通过溶胀动力学方程对其溶胀过程进行了描述,水凝胶中聚乙烯醇的含量,试样尺寸以及溶胀体系的pH值,是溶胀速率快慢的重要影响因素。     

人工髓核材料(半晶聚乙烯醇水凝胶弹性体)的研制

研制一种可替代椎间盘髓核并恢复其功能的生物医用材料 ,探讨半晶聚乙烯醇水凝胶弹性体材料临床应用的可行性。聚乙烯醇 (PVA)水溶液在 - 2 0℃下冷冻 6～ 12 h,室温下融化 1～ 2 h,上述过程重复 1～ 3次 ,然后对试样进行真空脱水 ,制得人工髓核材料 (半晶 PVA水凝胶弹性体 )。差示扫描量热法 (DSC)和力学性能试验研究了 PVA水溶液浓度、真空脱水和 γ射线辐照对水凝胶 PVA的结晶度和力学性能的影响     

人工髓核材料的研究进展

椎间盘退变性疾病是一种临床常见疾病,40%的下腰背疼痛是由腰椎间盘退变引起的。临床手术治疗只能在短期内缓解症状,无法达到根治的目的。在髓核摘除术后,人工髓核组织材料包括最早的硅橡胶、不锈钢和现在使用的水凝胶材料被用来填补病变的髓核组织,维持椎间盘足够的高度。随着组织工程和材料科学的不断发展,有希望使用干细胞或多能细胞来修复病变椎间盘或逆转其退变过程,重塑椎间盘的生理功能。现阶段组织工程仍然需要面临的问题是能否找到一种近似于髓核组织结构和功能的细胞外支架,为种子细胞的生长和生理活动提供合适的环境。文章就人工髓核材料的发展历史以及目前的研究情况展开综述。     

硅凝胶人工晶体的生物相容性

本文参照国内外有关医用高分子材料的生物学评价试验方法,对国产医用级硅凝胶人工晶体作了系统的生物学评价。结果表明:硅凝胶人工晶体对眼及皮肤无刺激作用、无热原、无毒性、体外溶血率小于5％,对细胞生长有促进作用,长期植入皮下时,随植入时间延长,囊壁厚度逐渐变薄,炎性细胞反应30天基本消失。染色体及骨髓多染红细胞未受影响。因此,可以认为硅凝胶人工晶体有良好的生物相容性。     

人工软骨材料——聚乙烯醇水凝胶的研制

聚乙烯醇溶液于－２０℃左右的温度下冷冻６－１２ｈ,室温下颌化１－２ｈ,上述过程反复进行１－３次,然后对试样进行真空脱水处理,制得一种人工软骨材料－ＰＶＡ水凝胶。     

聚乙烯醇水凝胶及其复合物的研究与在人工软骨替代材料上的应用

聚乙烯醇水凝胶是一种具有良好生物相容性和力学性能的高弹性材料。本文介绍了聚乙烯醇水凝胶的成型方法，复合改性技术的研究进展，着重对聚乙烯醇水凝胶作为替代材料在关节软骨损伤修复中的研究现状和存在问题进行了综述，并概述了其应用前景和发展方向。     

聚乙烯醇体内植入和降解产物生物相容性研究

作者对国产医用级聚乙烯醇（ＰＶＡ）降解材料的降解产物进行系统的生物学评价。结果表明：ＰＶＡ材料降解产物的ＬＤ５０为３．８ｇ／ｋｇ，无溶血、对皮肤和眼粘膜无刺激，不引起致敏反应。细胞增减可促进细胞的生长和细胞集落的形成；同时，将ＰＶＡ材料动物体内植入２８０天，与周转组织相容性良好。该研究进一步证实，ＰＶＡ材料有良好的生物相容性。     

人工材料与人工脏器的生物相容性

目前临床上使用的许多装置都是用金属、玻璃、陶瓷和高分子等材料制作的,现在一般把这些医用材料统称为“生物材料”(Biomaterial)。研究这些材料,首先遇到的问题是如何快速、准确地评价材料的生物相容性,这对于研究新生物材料和加快研究周期将起着重要的作用。但只有少数体外试验能对表面进行很好的表征,并与体内试验结果有相关性。因此,本文结合作者的研究工作,简要介绍生物材料与血液的生物相容性以及生物相容性的评价方法。     

壳聚糖水凝胶与星形胶质细胞体外生物相容性评价的实验研究

研究壳聚糖水凝胶材料与星形胶质细胞的体外生物相容性,初步探讨壳聚糖水凝胶作为神经组织工程支架材料的可行性。利用氯化壳聚糖、β-甘油磷酸钠和羟乙基纤维素制备壳聚糖水凝胶,MTT法评价其细胞毒性;体外培养鉴定新生Wistar大鼠脑皮层星形胶质细胞;壳聚糖水凝胶与星形胶质细胞体外共培养,观察星形胶质细胞在材料上的生长;MTT法检测接种后1、35、、7d的细胞增殖度。体外成功制备壳聚糖水凝胶,该材料无细胞毒性;体外分离、培养得到状态良好的星形胶质细胞;体外星形胶质细胞在材料上培养呈星形,生长良好,有分支状突起形成;MTT结果表明,材料-细胞共培养组中的细胞增殖度明显高于单纯细胞组（P〈0.001）。壳聚糖水凝胶与星形胶质细胞在体外具有良好的生物相容性,有望作为神经组织工程支架材料。     

可吸收羟基磷灰石/聚DL-乳酸复合骨折内固定材料的生物相容性研究

可吸收骨折内固定材料要求具有良好的生物相容性。对自行研制的可吸收羟基磷灰石／聚ＤＬ乳酸（ＨＡ／ＰＤＬＬＡ）复合骨折内固定材料进行了一系列生物相容性实验,包括Ａｍ ｅｓ 实验、微核实验、急性和亚急性毒性实验、溶血实验、凝血试验和肌肉、骨内长期植入实验。结果表明,ＨＡ／ＰＤＬＬＡ 材料无毒,无致突变性,不引起溶血和凝血。结论：ＨＡ／ＰＤＬＬＡ 复合材料具有很好的生物相容性。     

沉淀法原位复合聚乙烯醇(PVA)/羟基磷灰石(HA)水凝胶的结构与性能研究

研究了制备聚乙烯醇(PVA)，羟基磷灰石(HA)复合水凝胶的沉淀法原位复合技术，对该法制备的复合水凝胶的力学强度、结晶性能和微观形貌进行了分析，并与物理共混法加以比较。结果表明，沉淀法原位复合技术可在PVA水凝胶基体中合成得到粒度细，分散好的晶相HA陶瓷微粒，复合后水凝胶的结晶度和拉伸强度比之基体试样均有大幅度提高。     

Mucoadhesive poly(vinyl alcohol) hydrogels produced by freezing/thawing processes: Applications in the development of wound healing systems

Ultrapure poly(vinyl alcohol) (PVA) hydrogels were prepared by exposing an aqueous solution of 15 or 20 wt% PVA to repeated cycles of freezing for 6 or 12 h at -20°C and thawing for 2 hours at 25°C. The adhesive characteristics of the PVA gels in contact with a reconstituted mucus surface were quantified using a tensile technique. As the number of freezing/thawing cycles increased, the work of fracture (adhesion) decreased due to the increase in the PVA degree of crystallinity. Crystallinity was determined using differential scanning calorimetry. PVA gels prepared from the 20 wt% solution and exposed to two cycles of freezing/ thawing exhibited the largest work of adhesion. Drug delivery studies were conducted with ketanserin, a wound healing enhancer. Release studies were conducted using PVA samples prepared from a 20-wt% solution that were exposed to two or three freezing cycles for 12 h followed by thawing for 2 h. Results from the release of the drug from the PVA sample exposed to two cycles showed that approximately 80% of the ketanserin was released within 4 h.     

Swelling Behaviors of Poly(N‐isopropylacrylamide) Nanosized Hydrogel Particles/Poly(vinyl alcohol)/Water Systems: Effect of the Degree of Hydrolysis of PVA

Using poly(vinyl alcohol) as a drug model, the swelling behaviors of thermosensitive poly(N‐isopropylacrylamide) gel with various concentrations of PVA are investigated. The swelling ratio in PVA9000 is larger than that of PVA89000 at the same composition because the fully hydrolyzed PVA acts as a steric hindrance. A lattice‐based molecular thermodynamic model is used to obtain interaction parameters and then directly applied to describe the swelling behaviors of the gel. Using only one adjustable parameter, the PVA selectivity can be theoretically predicted and the ternary phase diagrams of PNIPA/water/PVA system can be generated. Lastly, the calculated results are compared with the swelling data for PNIPA/PVA copolymer gel, and are found to be in good agreement with the proposed model.

     

Long-term in vivo performance and biocompatibility of poly(vinyl alcohol) hydrogel macrocapsules for hybrid-type artificial pancreas

A bag-shaped macrocapsule suitable for Langerhans islets entrapment and immunoisolation was constructed using a semipermeable hydrogel membrane of poly(vinyl alcohol) (PVA) cross-linked chemically and sterilized by a radiation method. Empty (not seeded with Langerhans islets), sealed, sterile macrocapsules were implanted into the intraperitoneal cavity of adult female Buffalo rats for periods of up to 6.5 months. Long-term in vivo performance of the macrocapsule membrane was evaluated on the basis of the permeability measurements of glucose and albumin. The results of experiments revealed the progressive, disadvantageous alterations of the PVA hydrogel membrane resulting in a decrease in the permeability of solutes. Histochemical examinations of the cellular enzyme activities in the implant-encapsulating tissue, regarding the acid and alkaline phosphatases, were performed to evaluate the activity of cells involved in the inflammatory response to the long-term macrocapsule implantation.     

A Simple Access to the (Log/Normal) Molecular Weight Distribution Parameters of Polymers Using PGSTE NMR

A log/normal MWD is characterized by two parameters, its mean molecular weight M₀ and width σ. It is demonstrated how these parameters can be obtained by model fitting a stretched exponential function (SEF), as characterized by two parameters β and D_S, to the PGSTE response curve. Based on simulations, two general empirical equations relating β and D_S to M₀ and σ are found. The model enables the MWD characteristics to be determined if the scaling law between diffusivity and molecular weight is known. The sensitivity and relative error of σ and M₀ are discussed and the applicability of the model is illustrated by analyzing experimental NMR response curve of some PEO samples. The key advantages of this technique are its simplicity, numerical robustness, and reliability.