聚-L-乳酸/β-磷酸三钙复合物生物可吸收骨折内固定棒的体内降解和组织相容性

将β-磷酸三钙(β-TCP)与聚-L-乳酸(PLLA)复合得到PLLA/β-TCP复合材料,用注射成型方法制备出可吸收骨折内固定棒,然后通过分子量、质量变化、扫描电镜观察、弯曲强度变化和组织学方法等研究可吸收骨折内固定棒的体内降解过程。结果表明,降解初期聚乳酸的分子量有大幅度下降,重量损失滞后。随着降解的进行,可吸收棒表面逐渐粗糙,内部逐渐出现微孔和小“沟壑”,弯曲强度从初始的151MPa下降至12周的106MPa。组织学分析显示,PLLA/β-TCP复合材料具有良好的组织相容性。     

生物可吸收高强度左旋聚丙交酯材料在体内的力学特征

目的观察生物可吸收固态压缩法增强的、高强度左旋聚丙交酯poly-L-lactide,PLLA材料在体内的力学变化特征,评价其作为骨固定装置材料的价值. 方法用特殊的加热压缩方法-固态压缩法(solid-state compressionSC)加工左旋聚丙交酯,得SC-PLLA试棒(3.2mm×30mm),植入兔的皮下和股骨内,在长达48周的降解时间里,观察材料的力学性能(弯曲强度和剪切强度)和扫描电镜(SEM)下的微观形态. 结果植入24周后,各组SC-PLLA在体内的力学强度均可维持在弯曲强度180Mpa以上,剪切强度75Mpa以上,它们都大于皮质骨强度.剪切强度的下降比弯曲强度快.SEM见SC-PLLA降解前内部有大量排列整齐的纵向纤维,并随降解而破坏并出现孔隙. 结论固态压缩法可获得高初始强度和维持强度的PLLA,满足一般的骨内固定要求.SC-PLLA是一种有前途的生物可吸收接骨材料.     

生物可吸收高强度固态压缩聚丙交酯的降解特征和强度维持

用特殊的加热压缩方法固态压缩法 (solid statecompression ,SC)加工左旋聚丙交酯 (poly L lac tide ,PLLA) ,获得高强度SC PLLA(弯曲强度 2 5 0Mpa,剪切强度 190Mpa)。将SC PLLA棒 (3.2mm× 30mm) ,置于PBS液或植入兔的皮下和股骨内 ,定期观察粘均分子量、结晶度、扫描电镜 (SEM )形态和机械性能 (弯曲强度和剪切强度 ) ,研究该材料的降解特征和强度特性 ,以评价其作为矫形外科骨固定装置材料的价值。结果表明 ,各组分子量在前 12周下降迅速 ,其后缓慢下降 ,至 72周时 ,各组分子量降解 98%以上 ;结晶度则与此相反 ,12周内上升迅速 ,36周达最大。SEM见SC PLLA降解前内部有大量排列整齐的纵向纤维 ,并随降解而破坏并出现孔隙。SC PLLA降解 2 4周后 ,各组的弯曲强度仍维持在 180MPa以上 ,剪切强度在 75MPa以上 ,都大于皮质骨强度 ,提示材料的强度维持时间满足一般的骨内固定要求。因此SC PLLA是一种有前途的生物可吸收接骨材料     

可吸收内固定材料L/DL-聚乳酸的体外降解特性

背景：目前以左旋聚乳酸为代表的可吸收骨折内固定物已应用于临床,这种人工合成的高分子聚合物充分展示了其优越性,但同时也存在不足,限制了其广泛应用。 目的：评价可吸收内固定材料L/DL-聚乳酸的体外降解情况。 方法：将L/DL-聚乳酸试件置于37 ℃恒温的磷酸盐缓冲液中,在2,4,8,12,20,28周时间点取材,进行大体观察、扫描电镜观察、三点弯曲强度测定、重均分子质量检测并计算其降解率。另将相同试件置于蒸馏水中,于不同时间点测其pH值变化。 结果与结论：降解早期试件重均分子质量和机械强度下降较快,8周时重均分子质量降解了74.29%,机械强度衰减了60.99%,随后趋于平缓;对试件降解过程中抗弯强度衰减率和重均分子质量降解率进行双变量相关性分析,结果表明两者呈正相关性(r=0.958,P < 0.05);pH值在20周后有较明显下降;L/DL-聚乳酸的降解腐蚀在其表面和内部几乎同时发生。提示L/DL-聚乳酸符合骨折内固定物的生物降解性和机械性能要求,有望在颌面外科领域应用。     

聚L乳酸/β-磷酸三钙可吸收材料体内降解过程中的生物力学特性

背景：临床应用的金属内固定材料初始弯曲强度及弹性模量约为皮质骨的4倍及20倍,其力学性能不能随骨愈合过程动态变化,出现医学上的“应力遮挡效应”,影响骨愈合且需要二次手术取出。 目的：观察β-磷酸三钙与聚L乳酸复合可吸收内固定材料在动物体内降解后的生物力学特性。 方法：在30只新西兰大白兔腰背部左侧皮下植入聚L乳酸可吸收棒状材料为对照组,右侧植入聚L乳酸/β-磷酸三钙可吸收棒状材料作为实验组。于术前及术后4,8,12,16,24周观察两组材料的弯曲强度、剪切强度及扭转强度。 结果与结论：降解过程中两组材料的弯曲强度、剪切强度及扭转强度随时间的延长呈逐步下降趋势;术后12,16,24周实验组材料弯曲强度均高于对照组材料(P < 0.05)。术后4,8,12,16,24周实验组材料剪切强度均高于对照组材料(P < 0.05)。术后各时间点实验组材料扭转强度均稍高于对照组材料,但差异无显著性意义(P > 0.05)。说明聚L乳酸/β-磷酸三钙可吸收材料的体内降解速度较纯聚L乳酸慢,其力学强度能维持较长时间,可满足松质骨骨折的固定及骨组织愈合的要求。     

左旋聚乳酸的改性实验

背景：目前临床上大量使用的金属支架永久存留于人体,对人体存在潜在的风险。 目的：观察改性对左旋聚乳酸的作用以及改性材料用于可降解支架制备的可行性。 方法：以左旋聚乳酸/聚己内酯为95∶5的比例,用溶液法制备左旋聚乳酸、聚乳酸/聚己内酯共聚材料(PLCL-J 9505)和聚乳酸/聚己内酯共混材料(PLCL-H 9505)薄膜。 结果与结论：力学性能测试结果显示,3个月左旋聚乳酸材料的脆性明显升高,材料变得容易断裂,成为制备支架的一大缺陷;PLCL-J材料力学性能损失过快,第3周屈服完全消失,第4周拉伸强度开始急剧下降,到第10周已经完全丧失力学性能;PLCL-H材料不仅初始时断裂伸长率高,而且在降解过程中能始终保持较高的弹性。特性黏数测试和表面形态观测结果显示PLCL-J材料的降解速率过快,不适合在支架上应用,而左旋聚乳酸和PLCL-H基本是匀速的水解,且PLCL-H相对于左旋聚乳酸降解速率有一定程度的增加。提示左旋聚乳酸与聚己内酯共混改性比例为95∶5时不仅能保证材料具备支架所需的力学强度,还能显著提高材料的断裂伸长,达到了增塑目的的同时,也加快降解速率,有望成为制备可降解支架的新型材料。     

PLLA/β-TCP复合骨折内固定材料的体外降解性能的研究

对自行研制的可吸收PLLA/β-TCP复合骨折内固定材料的体外降解性能进行评价。在体外降解实验中,将含量为20%、30%、40%、50%的β-TCP和单纯PLLA试件分别置于SBF缓冲液中,于3、6、91、3周取材,测试其机械强度,并与初始机械强度对比。对含量为20%的β-TCP复合材料中PLLA降解过程中分子量的变化进行了测试。结果表明:加入β-TCP可加快聚乳酸的降解,从而调整其降解速度和强度,使其与人体骨折愈合时间相符合。     

生物可吸收性甲壳素纤维增强聚乳酸复合材料体内体外降解性研究

对酸化改性甲壳素纤维增强聚乳酸复合材料板材进行了体外降解及动物体内植入实验。该复合材料板材初始弯曲强度为114．72MPa，初始弯曲模量为3980．05MPa。在37℃，乳酸钠林格组织液中浸泡16周后，其弯曲强度降至31．42MPa。其体外耐水解特性及耐强度衰减特性均明显优于初始弯曲强度远高于它的PGA／PLA和PGA自增强复合材料。该复合材料的降解产物可通过体内代谢吸收，提示了该材料潜在的应用前景。     

可吸收固位钉治疗多发性肋骨骨折

背景：介绍可吸收材料的种类及优点,可吸收肋骨钉治疗多发性肋骨骨折适应证及禁忌证。对比观察采用可吸收固位钉和保守方法治疗多发性肋骨骨折的疗效。 方法：以“肋骨骨折,可吸收固位钉,内固定”为检索词,检索2002/2010 PubMed数据库、维普数据库与可吸收固位钉与多发性肋骨骨折相关文献,重点探讨了可吸收材料的种类及优点,以及可吸收肋骨钉治疗多发性肋骨骨折适应证及禁忌证。并进行了临床验证,对120例多发性肋骨骨折的患者采用可吸收钉进行内固定,同时以行保守治疗的多发肋骨骨折患者80例做对照。 结果：可吸收肋骨固定钉具有良好的组织相容性;抗弯曲强度略高于人体骨皮质;无毒副作用;3~5年可完全降解,避免二次手术。临床验证表明采用可吸收钉固定的患者恢复肋骨连续性,胸骨疼痛持续时间,住院时间较保守治疗者明显缩短(P < 0.01);同时可吸收钉固定患者的肺不张例数,胸廓畸形例数,胸腔积液例数,胸膜粘连例数比保守治疗者减少(P < 0.01)。 结论：对胸外伤引起多根多段肋骨骨折,用可吸收肋骨钉进行固位方法简易,并发症少,疗效可靠。     

生物可吸收性甲壳素纤维增强聚乳酸复合材料体内体外 …

对酰化改性甲壳素纤维增强聚乳酸复合材料板进行了体外降妥及动物及体内植入实验。该复合材料板材初始弯曲强度为１１４．７２ＭＰａ,初始弯曲模量为３９８０．０５ＭＰａ。在３７℃,乳酸钠林格组织液中浸泡１６周后,其弯曲强度降至３１．４２ＭＰａ。其体外耐水解特性及耐强度衰减特性均明显优于初始弯曲强度远高于它的ＰＧＡ／ＰＬＡ和ＰＧＡ自增强复合材料。该复合材料的降解产物可通过体内代谢吸收,提示了该材料潜在的应用前     

Effect of gamma,ethylene oxide,electron beam,and plasma sterilization on the behaviour of SR-PLLA fibres in vitro

The aim of this study was to evaluate the effect of various sterilization processes on the physical and mechanical properties of self-reinforced bioabsorbable fibres made out of polylactide (PLLA). The samples were sterilized using plasma, ethylene oxide (one and two cycles), gamma (25 kGy at room temperature, 25 kGy in dry ice, and 2 x 25 kGy at room temperature), and electron beam (15, 25, and 55 kGy) sterilization. The intrinsic viscosity, crystallinity, and mechanical properties (modulus of elasticity, yield strength, and ultimate tensile strength) were tested before and immediately after each sterilization treatment, as well as up to 30 weeks in vitro. Compared with unsterilized fibres, the intrinsic viscosity was markedly decreased after radiation sterilization (gamma and electron beam) and the loss in mechanical properties was accelerated during in vitro degradation. Plasma and ethylene oxide (one and two cycles) did not markedly alter the properties of the samples after sterilization or during in vitro degradation. These data are important for determining the effect of various sterilization processes on the physical and mechanical properties of polylactide-based materials and can be used to predict how fast degradation of the mechanical properties of the self-reinforced PLLA will occur. They can also be used to tailor the degradation kinetics to optimize implant design.     

Enhanced retention of polymer physical characteristics and mechanical strength of 70:30 poly(L-lactide-co-D,L-lactide) after ethylene oxide sterilization

This study examined the effect of ethylene oxide (EtO) and electron beam (e-beam) irradiation on the properties of 70:30 poly(L-lactide-co-D,L-lactide). The effects of sterilization upon the polymer physical characteristics and strength retention of the material were examined, both initially and after being subjected to real time ageing. Commercially available 70:30 poly(L-lactide-co-D,L-lactide) material was fabricated into rectangular, cylindrical, screw, and sheet designs, and tested in compression, shear, or tension. Sterilization of 70:30 poly(L-lactide-co-D,L-lactide) by ethylene oxide had a nearly negligible effect on the physical properties of the polymer, regardless of specimen size or manufacturing technique. The molecular weight and inherent viscosity of the specimens decreased by approximately 3% after sterilization by EtO. However, sterilization of 70:30 poly(L-lactide-co-D,L-lactide) by e-beam irradiation resulted in immediate changes to some of the physical properties of the polymer. Specimens sterilized by e-beam irradiation displayed an immediate decrease in inherent viscosity of approximately 67% as compared to the respective nonsterile samples. The immediate decrease in inherent viscosity and molecular weight with e-beam irradiation required approximately 39 weeks of real time ageing of the EtO sterilized parts. At all time points investigated in the present study, the strength retention of the EtO sterilized devices equaled or exceeded that of the e-beam irradiated samples.     

Effect of gamma,ethylene oxide,electron beam,and plasma sterilization on the behaviour of SR-PLLA fibres in vitro

- The aim of this study was to evaluate the effect of various sterilization processes on the physical and mechanical properties of self-reinforced bioabsorbable fibres made out of polylactide (PLLA). The samples were sterilized using plasma, ethylene oxide (one and two cycles), gamma (25 kGy at room temperature, 25 kGy in dry ice, and 2 × 25 kGy at room temperature), and electron beam (15, 25, and 55 kGy) sterilization. The intrinsic viscosity, crystallinity, and mechanical properties (modulus of elasticity, yield strength, and ultimate tensile strength) were tested before and immediately after each sterilization treatment, as well as up to 30 weeks in vitro. Compared with unsterilized fibres, the intrinsic viscosity was markedly decreased after radiation sterilization (gamma and electron beam) and the loss in mechanical properties was accelerated during in vitro degradation. Plasma and ethylene oxide (one and two cycles) did not markedly alter the properties of the samples after sterilization or during in vitrodegradation. These data are important for determining the effect of various sterilization processes on the physical and mechanical properties of polylactidebased materials and can be used to predict how fast degradation of the mechanical properties of the self-reinforced PLLA will occur. They can also be used to tailor the degradation kinetics to optimize implant design.     

Aeration of medical plastics

Because the metabolic reaction that gives ethylene oxide is sterilizing qualities also takes place with human protein, it is imperative that any residual gas be removed before the sterilized material is used on the patient. This paper presents a method of estimating aeration time required following sterilization of polyvinyl choride (PVC) to reduced toxic residues to a desired level. The method proposed involves calculation of the coefficient of diffusivity, and the use of a simplified diffusion equation to estimate aeration time.     

Biocompatibility of supercritical CO2-treated titanium implants in a rat model

Supercritical phase CO2 is a promising method for sterilizing implantable devices and tissue grafts. The goal of this study is to evaluate the biocompatibility of titanium implants sterilized by supercritical phase CO2 in a rat subcutaneous implantation model. At 5 weeks post implantation titanium implants sterilized by supercritical phase CO2 produce a soft tissue reaction that is comparable to other methods of sterilization (steam autoclave, ultraviolet light radiation, ethylene oxide gas, and radio-frequency glow-discharge), as indicated by the thickness and density of the foreign body capsule, although there were some differences on the capillary density. Overall the soft tissue response to the implants was similar among all methods of sterilization, indicating supercritical phase CO2 treatment did not compromise the biocompatibility of the titanium implant.     

Poly(ethylene glycol)-poly(L-lactide) diblock copolymer prevents aggregation of poly(L-lactide) microspheres during ethylene oxide gas sterilization

Sterilization procedure is one of the most important obstacles in the clinical applications of biodegradable microspheres. The microspheres prepared with poly(alpha-hydroxy acid) were severely aggregated during ethylene oxide (EO) gas sterilization, and could not be used in clinical applications. In this study, the effects of EO gas sterilization on the poly(L-lactide) (PLLA) microspheres were analyzed by nuclear magnetic resonance spectroscopy (1H-NMR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), scanning electron microscope (SEM) and size fractionation. The aggregation between the microspheres might be stimulated by high mobility of amorphous regions of PLLA on the microsphere surfaces since both water vapor and gas mixture can reduce glass transition temperature (Tg) of PLLA below the sterilization temperature. During EO gas sterilization, there were no changes in the molecular structure and the molecular weight of PLLA in microspheres, but there were changes in the crystallinity of PLLA in microspheres. In this study, poly(L-lactide)-poly(ethylene glycol) diblock copolymers (PLE) were blended with PLLA homopolymers in various ratios to design the microsphere suitable for EO gas sterilization. Aggregation of PLLA microspheres was markedly prevented when more than 4wt% of PLE was blended in the microspheres. This inhibition effect on aggregation may be due to the increased initial crystallinity of the microspheres, which help to maintain the microsphere morphology during EO gas sterilization.     

Processing, annealing and sterilisation of poly-L-lactide

Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioabsorbable. Degradation of PLLA proceeds through hydrolysis of the ester bonds in the polymer chains and is influenced significantly by the polymer's molecular weight and crystallinity. To evaluate the effects of processing and sterilisation on these properties, PLLA pellets were either compression moulded or extruded, subjected to annealing at 120 degrees C for 4h and sterilised by ethylene oxide (EtO) gas. Procedures were used to evaluate the mechanical properties, molecular weight and crystallinity. Upon processing, the crystallinity of the material fell from 61% for the PLLA pellets to 12% and 20% for the compressed and extruded components, respectively. After annealing, crystallinity increased to 43% for the compression-moulded material and 40% for the extruded material. Crystallinity further increased upon EtO sterilisation. A slight decrease in molecular weight was observed for the extruded material through processing, annealing and sterilisation. Young's modulus generally increased with increasing crystallinity, and extension at break and tensile strength decreased. The results from this investigation suggest that PLLA is sensitive to processing and sterilisation, altering properties critical to its degradation rate.     

Effect of sterilization on the physicochemical properties of molded poly(L-lactic acid)

In this study, the process of manufacturing and sterilizing an orthopedic implant constructed from poly(L-lactic acid) (PLLA) was closely simulated. The hydrogen peroxide gas plasma (HPGP) sterilization process was comparatively investigated against ethylene oxide (EtO). Characterization of the physical, thermal, mechanical, morphological, and chemical properties was monitored. The results indicate that the HPGP sterilization process did not have a significant influence on M(n) or M(w) initially or through 12 weeks of in vitro conditioning when compared with EtO. Only indications of physical aging were evident in the analysis of the thermal and mechanical properties by differential scanning calorimeter and tensile testing for each sterilization processes. Using wide angle X-ray diffraction to determine morphology characteristics, it was determined that no changes were observed between the as molded, HPGP, and EtO specimens initially or through the 12 week in vitro conditioning period. Contact angle measurements revealed a significant reduction in the surface energy following treatment by the HPGP process, suggesting the formation of polar groups. However, surface chemistry analysis by ATR-FTIR indicated no significant chemical modification from either sterilization method. PLLA showed intermediate levels of residual hydrogen peroxide absorption following processing by HPGP.     

Effect of surface roughness and sterilization on bacterial adherence to ultra-high molecular weight polyethylene

Sterilization with ethylene oxide (EO) and gas plasma (GP) are well-known methods applied to ultra-high molecular weight polyethylene (UHMWPE) surfaces in the belief that they prevent major material changes caused by gamma irradiation. However, the influence of these surface sterilization methods on bacterial adherence to UHMWPE is unknown. UHMWPE samples with various degrees of roughness (0.3, 0.8 and 2.0 µm) were sterilized with either GP or EO. The variations in hydrophobicity, surface free energy and surface functional groups were investigated before and after sterilization. Sterilized samples were incubated with either Staphylococcus aureus or Staphylococcus epidermidis in order to study bacterial adherence to these materials. Fewer bacteria adhered to UHMWPE after sterilization with EO than after sterilization with GP, especially to the smoothest surfaces. No changes in chemical composition of the UHMWPE surface due to sterilization were observed using X-ray photoemission spectroscopy analysis. The decreased bacterial adherence to UHMWPE found at the smoothest surfaces after sterilization with EO was not directly related to changes in chemical composition. Increased bacterial adherence to rougher surfaces was associated with increased polar surface energy of EO-sterilized surfaces.     

一次性射频等离子手术电极灭菌方式的选择与验证

目的选择一次性射频等离子手术电极灭菌方式,并对灭菌效果进行验证。方法综合比较4种常用灭菌方式的特征和环境,基于一次性射频等离子手术电极材料及特性,选择环氧乙烷灭菌法进行灭菌。灭菌完成后确认一次性射频等离子手术电极的性能,并采用生物指示剂对产品微生物及环氧乙烷残留进行测试。结果采用环氧乙烷灭菌方法对一次性射频等离子手术电极进行灭菌,灭菌器内灭菌参数为:预真空度60 k Pa±5 k Pa、灭菌温度50℃±5℃、相对湿度55%RH±20%RH、灭菌压力0~5k Pa、保压时间1 min、加药计量895 g、灭菌剂作用时间6 h、排残真空度-60 k Pa±5 k Pa、排残次数3次、每次排残时间为30 min、有毒气体解吸时间为14 d。结论环氧乙烷灭菌法是针对包装后一次性射频等离子手术电极可行且有效的灭菌方法。