医用硅橡胶的生物相容性缺点及现代改良

硅橡胶具有性能稳定、易于塑形、产品效益可观的优点,已广泛应用于生物医学工程领域和医疗卫生行业.尽管如此,硅橡胶在生物医学领域中的应用仍然受到其自身缺陷的挑战.表面疏水性、自身影像相容性欠佳、长期植入体内后发生钙化乃是医用硅橡胶制品在生物相容性方面亟待克服的缺点.近几年来国内外专家针对以上缺点进行了诸多改良研究,热点主要集中于硅橡胶的表面湿润性增加、X-线阻射功能增强、防钙化预处理等方面.取得了阶段性成果,但尚未使医用硅橡胶的生物相容性达到理想的境界.     

纳米铁显影增强硅橡胶的制备及影像可视性评价

目的 探讨纳米铁微粒作为显影标记物对医用硅橡胶改性的可行性并评价复合材料的影像可视性.方法 硅油与纯铁粉、碳包铁粉混合,按预定的配方比分别与甲基乙烯基硅橡胶共混、密炼、模压、硫化,得到纳米纯铁粉增强硅橡胶（第1组）、纳米碳包铁粉增强硅橡胶（第2组）,空白对照组为医用硅橡胶.CT扫描体外各组材料试件,获取图像并测得CT值,比较组间CT值均值的差异性;将2组材料试件植入犬皮下,获得标准X-线图像;X射线衍射技术分析材料内铁微粒的组分稳定性.结果 分别制备出铁粉显影增强硅橡胶和碳包铁粉显影增强硅橡胶,新材料在体内外的X-线图像清晰可见,复合材料的CT值随金属纳米粉体量和纳米微粒原子量的增加而增加,2组材料的CT值均值、组间配方比相同的材料的CT值均值差异显著（P＜0.001）;材料放置180 d后,单质铁出现衍射峰的位置基本没有变化,分散在硅橡胶中的纳米纯铁微粒、碳包铁微粒较为稳定.结论 金属纳米铁粉、碳包铁粉可作为硅橡胶显影性改良的标记物.     

硅橡胶膜细胞载体的应力分析及生物相容性

目的 报道一种自制的硅橡胶膜细胞载体,通过三维有限元方法计算其表面应变分布情况,并作细胞生物相容性分析,对材料进行全面评价,为细胞的应力刺激实验提供理论依据。方法 将硅橡胶材料制作成0.1 cm厚的透明薄膜,结合硅橡胶材料的泊松比以及弹性模量,应用三维有限元分析软件对数据进行处理,模拟硅橡胶受到牵张应变后产生的形变;通过MTT方法比较细胞在硅橡胶和标准培养板上的生长情况,并采取体外皮下包埋实验验证硅橡胶材料是否具有生物学毒性。结果 在对材料加载0.5%~20%的过程中,有效应变范围集中在硅橡胶膜的中心区域,约占总面积的90%;同时,硅橡胶材料虽然在生物相容性方面与标准培养板存在一定差异,但其本身无生物学毒性。结论 这种自制的硅橡胶细胞载体表面应力分布良好,生物相容性尚可满足细胞培养,但表面需进一步改善,可满足细胞的牵张应变实验。     

铁质纳米粉体对甲基乙烯基硅橡胶力学性能的影响

目的探讨铁质纳米粉体改性甲基乙烯基硅橡胶的力学性能变化及其在基胶中的分散状态。方法根据国家标准对前期制备出的纳米铁粉增强硅橡胶和碳包铁粉增强硅橡胶复合材料进行邵氏A硬度、拉伸强度、扯断伸长率、扯断永久变形率、撕裂强度等力学性能指标测试,使用热场发射扫描电镜（TFE．SEM）观察复合材料的表面形貌和断口形貌,了解纳米铁在硅橡胶基体的分散状态。结果复合材料试件的邵氏A硬度、拉伸强度、扯断伸长率、扯断永久变形率、撕裂强度的均值随着铁质纳米粉体添加量的增加而增加。当纳米铁在配方中的份数大于17份、碳包铁的份数大于19份时,复合材料的拉伸强度均值不再增加反而呈下降趋势;当铁质纳米粉体的在配方中超过15份时,扯断伸长率、撕裂强度的均值开始下降。铁质纳米微粒在硅橡胶的表面分散均匀,在配方比为85：15的硅橡胶,纳米铁试样的断面及配方比87：13的硅橡胶／碳包铁试件的断面,可观察到粉体的团聚体。结论纳米铁粉体和碳包铁粉体对甲基乙烯基硅橡胶力学性能的补强作用主要取决于纳米粉体的粒径、添加量以及在基胶中的团聚程度。     

外科植入硅橡胶材料钙化及抗钙化研究进展

硅橡胶钙化是材料植入体内后其表面或基质内出现病理性矿化的现象,尚无有效防治方法.钙化的重要过程是材料表面的磷酸根离子与钙离子结合启动成核聚集,缓慢增大、融合,逐渐形成较大的羟基磷灰石钙盐堆积.其研究已发展到细胞和基因水平,如基质Gla蛋白质簇是一种硅橡胶假体周围组织钙化的抑制因子.钙化过程中有机模板对无机晶体的调制作用需理论上的突破.硅橡胶自身局部抗钙化性能受到重视.揭示硅橡胶钙化和钙化抑制的机理,可为构建新型抗钙化功能材料提供依据.     

IgE-mediated anaphylactoid reactions to rubber

Delayed hypersensitivity to rubber chemicals is well known, but there are only a limited number of case reports on an immediate type of hypersensitivity inducing contact urticaria. We have recently seen several patients with rubber glove-induced contact urticaria who have had both positive skin prick tests and positive RAST tests to natural latex from the rubber tree (Hevea brasiliensis). We now report on five patients who also developed systemic reactions. It is clear that sensitized subjects are at risk of developing anaphylaxis during medical examination or surgery when rubber gloves are used. The occurrence of IgE-mediated allergy to rubber is probably underestimated.     

涤纶网加强型医用硅橡胶引流条的研制及临床应用

为解决外科手术中的引流问题 ,研制了一种涤纶网加强型医用硅橡胶引流条。该产品是用医用加成型硅橡胶与涤纶网复合 ,通过模压方式制作的波纹状引流条。经临床应用表明引流效果好 ,使用方便 ,能促进伤口愈合     

Grafting of a synthetic heparinoid polyelectrolyte onto silicone rubber

Using a [3H]-labelled polyelectrolyte as a tracer, the 60Co grafting of a synthetic heparinoid polyelectrolyte onto silicone rubber was studied. The polyelectrolyte was labelled by the coupling of a radioactive amine to carboxylate groups of the polyelectrolyte. The amount of grafted polyelectrolyte was found to be dependent on the radiation dose.     

The effect of plasma-induced graft copolymerization of PHEMA on silicone rubber towards improving corneal epithelial cells growth

A PHEMA grafted polymer film was prepared by plasma induced graft copolymerization onto an elastic material, silicone rubber. The control, Ar plasma-treated, and PHEMA-grafted silicone rubber surfaces were characterized by ESCA, FTIR-ATR, and SEM techniques. ESCA verified the respective chemical shift of control and Ar plasma-treated films. The presence of the grafted PHEMA was also verified by ESCA. The amounts of grafted PHEMA did not monotonously increase with the plasma exposure conditions, but decreased after passing a maximum. The introduction of PHEMA onto a hydrophobic support provided an adequate surface for rabbit corneal epithelium cell attachment and growth. Cell attachment and growth onto these surfaces were examined by light microscopy. Cell attachment onto the control and Ar plasma-treated surface was negligible, while improved attachment and growth of rabbit corneal epithelium cells was demonstrated on the PHEMA-grafted polymer surface. The PHEMA-grafted silicone rubber surface demonstrated a confluent cell layer after 72 h.     

Microporous flow surface variation and short term thrombogenicity in dogs

This study was designed to evaluate the effect of three luminal surface coatings on short-term thrombogenicity in 4 mm internal diameter vascular prostheses. Microporous replamineform grafts (20–30 μm pore size) composed of silicone rubber were coated with medical grade biomaterials: Biolite^®, TEDMAC-heparin, and Biomer^®.These grafts were compared to each other and to control grafts of silicone rubber and Biomer that did not have coatings. Following three hours of implantation in the canine femoral artery, the prostheses were removed, opened longitudinally and evaluated for quantity of thrombus, % thrombus free surface, and type of thrombus. Silicone rubber grafts coated with Biolite carbon had the least thrombogenic flow surface followed by the control Biomer grafts, Biomer-coated silicone rubber grafts, TEDMAC-heparin coated silicone rubber grafts, and the control silicone rubber grafts. Due to the small number of samples, no statistical analysis was performed. Hence, the conclusions drawn are tentative.     

引导组织生长硅橡胶人工颅骨的研制及皮下植入试验

为减少颅骨修补术后皮下积液及响颅综合症的发生 ,研制一种新型引导组织生长硅橡胶人工颅骨。通过模压方法制备硅橡胶颅骨 ,采用硅橡胶粘合剂在颅骨的外表面复合聚酯无纺布 ,并进行了物理、化学性能和生物安全性评价。家兔皮下种植实验表明 ,聚酯无纺布具有显著诱生组织细胞爬生作用 ,引导组织生长硅橡胶人工颅骨是一种安全、可靠的颅骨修复用品     

Biocompatibility of standard and silica-free silicone rubber membrane oxygenators.

Spiral coil membrane oxygenators made from either standard silicone rubber or silica-free silicone rubber were compared using three priming techniques. Standard priming, carbon dioxide priming, and denucleation priming were employed with each type of device. Four-hour venovenous membrane oxygenator perfusions were carried out on awake sheep anticoagulated with heparin. Virtually no differences were observed in any parameters measured between standard silicone rubber and filler-free silicone rubber membranes. Significantly greater platelet losses occurred during the first hour of perfusion with standard priming and with carbon dioxide priming than with denucleation priming, using either type of membrane. These experiments demonstrate that denucleation priming reduces platelet losses during extracorporeal membrane oxygenator perfusion, but that the use of filler-free silicone rubber does not improve the biocompatibility of the membrane.     

硅橡胶材料在面部整形中的应用

背景：硅橡胶材料可作为一种较理想的面部整形植入材料。 目的：评价硅橡胶材料在面部整形的应用。 方法：以 “硅橡胶,复合材料,生物力学性能,计算机辅助设计与制造, 头面部整形”为中文关键词;以“Silicone rubber,Composite,Mechanical properties, Computer Aided Design and Manufacturing, Head and facial plastic surgery” 为英文关键词,采用计算机检索2001-01/2010-12相关文章。纳入与硅橡胶材料在面部整形的应用相关的文章;排除重复研究或Meta分析类文章。以22篇文献为主重点进行了讨论硅橡胶材料的研究及其在面部整形的应用。 结果与结论：计算机的模型可用于面部整形的手术方案设计。整形术可解决了颜面部的外部造型美观问题,但有6%可发生各类并发症,其原因有：①手术操作失当。②未按美容术原则施术;③无菌观念淡薄。计算机术前的仿真设计和效果预览使患者参与自身个性化设计,显著增加手术成功率。在临床上只要把握好固体硅胶美容术的手术要点,严格手术操作原则,绝大多数并发症是可以避免的。     

Aspects of silicone rubber as encapsulant for neurological prostheses

The paper presents some measurements of the hydrothermal stability of experimental adhesive joints in water at 100°C. The joints are between one adhesive silicone rubber and ten metal or metal-oxide adherends, all combinations of interest to the neurological prosthesis maker. The probable adhesion mechanism is then considered, in the search for some parameter by which the experimental results could have been predicted. Evidence is produced that physical adsorption plays little or no part in the adhesion, but that hydrothermal stability seems to be a function of the adherend ionic charge. In pursuit of this idea, the valency, the Slater potential and the iso-electric point for the surface (IEPS) of the adherend are examined as possible prediction parameters. It is concluded that, at least in neutral and acidified water, the IEPS is a promising predictor, with the benefit that it is experimentally determinable for adherends of unknown composition. The most stable joints seem to occur when the charge density on the adherend has an optimum negative value.     

Mechanical properties of antibacterial silicone rubber for hydrocephalus shunts.

In an effort to find a solution to the serious problem of bacterial colonization of cerebrospinal-fluid shunting devices, room-temperature and heat-vulcanizing silicone rubbers were impregnated with gentamicin sulphate. The effects on the mechanical properties of the two rubbers were studied. Results show that the tensile strength and extensibility of the room-temperature-vulcanizing silicone rubber reduced with increasing concentration of the drug. For the heat-vulcanizing silicone rubber, the tensile strength was also found to decrease with increasing drug content. The extensibility after an initial reduction at low concentrations was found to increase at drug concentrations in excess of 10 mg/g. Nevertheless, the changes in mechanical properties measured are considered not to be so great as to preclude the application of drug-impregnated silicone rubbers to cerebrospinal-fluid shunting devices.     

Improved biocompatibility of silicone rubber by removal of surface entrapped air nuclei

Biomaterials activate the complement system which is important since C3a promotes platelet aggregation and release, and C5a activates neutrophils that may augment coagulation. Tiny air nuclei (microbubbles) are found in the surface roughness of biomaterials on exposure to a liquid, therefore two interfaces exist: (a) a blood/biomaterial, and (b) a blood/air interface. Experiments were carried out that documented that air bubbles activate complement and augment in vitro platelet aggregation in human plasma. The air nuclei were removed from the surface of silicone rubber by a technique termed denucleation to determine if complement activation and platelet aggregation could be reduced. We observed a significant reduction in C3a and C5a in the plasma samples incubated with denucleated silicone rubber as compared to the control samples (p less than 0.001, ANOVA). The plasma incubated with the denucleated silicone caused reduced platelet aggregation as compared to the plasma incubated with the control silicone when added to a platelet suspension (p less than 0.001, ANOVA). Surface chemical analysis by x-ray photo-electron spectroscopy (XPS) showed no change in the silicone rubber surface after the denucleation procedure.     

Crossreactivity between allergens in natural rubber latex and banana studied by immunoblot inhibition

Background An association between allergic reactions to natural rubber latex and to banana has been reported but the immunochemical properties of the putative crossreacting allergens remain unknown. Obfective To study extracts of banana and natural rubber latex and sera from latex-allergic patients for possible crossreacting allergens and IgE antibodies. Methods Sera from 22 latex-allergic patients and 22 control subjects with no evidence of allergy to latex or to banana were studied. All patients had positive and controls negative reactions in skin-prick testing using an eluate of latex gloves. IgE antibodies to natural rubber latex and to banana were evaluated by immunoblotting and by radioailergosorbent test (RAST) and crossreactivity between allergens in banana and natural rubber latex by immunoblot inhibition. Skin-prick testing was used to examine in vivo reactivity to banana. Results Ten of the 22 (45%) latex-allergic patients sera recognized altogether 14 allergens in banana by immunoblotting. The most frequently identified banana allergens were 23, 32, 36, 39 and 47kDa proteins. The banana skin-prick test was positive in 14 of 18 (78%) latex-allergic patients studied and banana RAST in 12 of 14 patient sera tested. Fourteen of 21 interviewed patients reported symptoms from eating or handling bananas. In immunoblot inhibition studies a dose-dependent inhibition of IgE binding to banana extract with natural rubber latex proteins was observed in all five patient sera tested and, likewise, the binding of IgE to natural rubber latex extract was inhibited with banana proteins in four of the five patient sera. Conclusions The present results confirm the existence of crossreacting allergens in natural rubber latex and banana and provide new information on the immunochemical nature and heterogeneity of these allergens.     

In vivo degradation of silicone rubber poppets in prosthetic heart valves.

Dynamic shear modulus G' was measured throughout the volume of three nonvariant silicone rubber poppets which were recovered from aortic prosthetic heart valves that had been implanted for 4 days, 52 days, and 8 years. Similar measurements were obtained for two unused silicone rubber poppets. Although the recovered poppets exhibited no obvious physical evidence of damage, the silicone rubber had undergone in vivo degradation throughout the poppet volume as indicated by decreases in modulus. The measurements also indicate that the poppet surface degrades at a rate faster than the core. Further, comparison with data reported in the literature suggests that the surfaces of variant poppets degrade at a rate faster than the surfaces of nonvariant poppets.     

Reduced adherence of Candida to silane-treated silicone rubber

Silicone rubber is widely used in the construction of medical devices that can provide an essential role in the treatment of human illness. However, subsequent microbial colonization of silicone rubber can result in clinical infection or device failure. The objective of this study was to determine the effectiveness of a novel silane-treated silicone rubber in inhibiting microbial adherence and material penetration. Test material was prepared by a combination of argon plasma discharge treatment and fluorinated silane coupling. Chemicophysical changes were then confirmed by X-ray photoelectron spectroscopy, contact-angle measurement, and atomic force microscopy. Two separate adherence assays and a material penetration assay assessed the performance of the new material against four strains of Candida species. Results showed a significant reduction (p < 0.01) of Candida albicans GDH 2346 adherence to silane-treated silicone compared with untreated controls. This reduction was still evident after the incorporation of saliva into the assay. Adherence inhibition also occurred with Candida tropicalis MMU and Candida krusei NCYC, although this was assay dependent. Reduced penetration of silane-treated silicone by Candida was evident when compared to untreated controls, plaster-processed silicone, and acrylic-processed silicone. To summarize, a novel silicone rubber material is described that inhibits both candidal adherence and material penetration. The clinical benefit and performance of this material remains to be determined.     

Cystic osteolysis induced by silicone rubber prosthesis

Synovitic symptoms and radiologically documented cystic lesions in several carpal bones and distal radius developed two years after the implantation of silicone rubber scaphoid prosthesis for pseudoarthrosis. Open biopsy revealed granulomatous synovitis and osteitis and foreign material in carpal tissues. Ultrastructurally dense material was found in the cytoplasm of histiocytic, often multinucleated cells. Electron-probe analysis of the material showed a definite peak for silicon, proving the causal relationship of symptoms and signs to the silicone rubber prosthesis.