聚乳酸复合材料降解过程中降解速率及pH值的研究

本文用溶液法将聚乳酸和甲壳素进行复合，以改善聚乳酸的降解性，制备一种具有适宜降解速率的组织工程支架材料。结果显示，当PLA／CS为1：0．4时，PLA／CS复合材料的降解失重百分率为最小；同时，随着降解时问的增加，复合材料的失重百分率逐渐上升；纯聚乳酸在降解4周后pH值下降得很快，而复合材料在整个降解过程中的pH值一直很稳定，在6．5左右。由此表明，甲壳素可改善PLA的降解速率，且在降解过程中，PLA／CS复合材料的pH值非常接近生理盐水的pH值。     

可吸收羟基磷灰石/聚DL-乳酸骨折内固定材料机械强度和生物降解性研究

目的评价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的机械强度和生物降解性。方法体外降解实验是把相同分子量的HA/PDLLA和单纯PDLLA试件分别置于PBS缓冲液中,于2、4、6、8、10、12周取材,测试生物降解率、吸水率、失重率、机械强度及降解液pH值,并作扫描电镜(SEM)观察;体内实验是用一枚HA/PDLLA棒内固定兔股骨髁松质骨部横形截骨,作X线摄片、组织学、机械强度及材料骨界面SEM观察。结果HA/PDLLA复合材料较单纯PDLLA材料降解速度减慢,机械强度提高,骨折正常愈合。结论HA/PDLLA材料具有足够的强度保证实验性松质骨骨折正常愈合。     

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。     

可吸收羟基磷灰石／聚ＤＬ—乳酸骨折内固定材料机械强度和生物降解性研究

目的：评价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的机械强度和生物降解性。方法：体外降解实验是把相同分子量的ＨＡ／ＰＤＬＬＡ和单纯ＰＤＬＬＡ试件分别置于ＰＢＳ缓冲液中,于２、４、６、８、１０、１２周取材,测试生物降解率、吸水率、失重率、机械强度及降解液pH值,并作扫描电镜（ＳＥＭ）观察;体内实验是用一枚ＨＡ／ＰＤＬＬＡ棒内固定兔股骨髁松质骨部横形截骨,作Ｘ线摄片、组织学、机械强度及材料——骨界面ＳＥＭ观察。结果：ＨＡ／ＰＤＬＬＡ复合材料较单纯ＰＤＬＬＡ材料降解速度减慢,机械强度提高,骨折正常愈合。结论：ＨＤ／ＰＤＬＬＡ材料具有足够的强度保证实验性松质骨骨折正常愈合。     

聚丁二酸丁二醇酯/聚碳酸亚丙酯生物膜的制备及相关性能评价

背景：聚丁二酸丁二醇酯、聚碳酸亚丙酯是近年来发展的新型医用材料,具有良好的生物相容性、可降解性及价格低廉等优点。 目的：采用静电纺丝法制备聚丁二酸丁二醇酯/聚碳酸亚丙酯生物膜,评价其理化性能、体外降解性能及对细胞增殖的影响。 方法：采用静电纺丝法制备聚丁二酸丁二醇酯/聚碳酸亚丙酯生物膜：常温下称取聚丁二酸丁二醇酯、聚碳酸亚丙酯各0.9 g,溶解于10 mL三氯甲烷中,磁力搅拌,待其充分溶解后,将纺丝液加入纺丝管内,调整纺丝距离约15 cm,最后开启电源将电压调至18 kV即可,扫描电镜观察其表面形态,检测其强度、接触角、吸水率及体外降解过程中的pH值和失重率。将人骨肉瘤细胞MG63与生物膜共培养7 d后,采用CCK-8检测细胞增殖。 结果与结论：扫描电镜可见聚丁二酸丁二醇酯/聚碳酸亚丙酯生物膜呈均匀多孔状,孔孔交通,纤维直径约  0.88 μm,平均孔径约5.68 μm,孔隙率为78.3%,断裂强度平均为2.31 MPa,断裂伸长率为23.48%,接触角约为87°,吸水率为68.54%;生物膜降解过程中pH值呈缓慢降低,第12周时pH值为6.76,同时该生物膜处于均匀缓慢的降解过程中,12周时失重率为6.04%。CCK-8实验结果显示该生物膜对细胞的增殖具有一定的促进作用。表明静电纺丝聚丁二酸丁二醇酯/聚碳酸亚丙酯生物膜具有良好的理化性能,具备良好的空间维持能力、湿润性及降解性,能为骨组织再生提供充足的时间。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

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     

甲壳素短纤维增强聚己内酯复合材料的制备及生物学评价

用共混法制备甲壳察短纤维增强聚己内酯复合材料，并对纯聚己内酯和甲壳察短纤维增强聚己内酯复合材料进行体外细胞毒性和生物相容性评价，为临床应用提供有价值的实验依据。对该两种材料进行体外细胞毒性试验、急性全身毒性试验、溶血试验、热源试验和过敏试验。结果显示受试材料最终细胞毒性级为0级，对细胞生长和增殖无明显抑制作用，材料中不存在潜在致敏性物质，浸提液无溶血反应和急性全身毒性反应，无热源反应，表明该复合材料具有良好的细胞和组织相容性，其作为胸壁缺损修补材料应用于临床具有可行性和安全性。     

PCL/ZrO_2骨组织工程支架3D打印制备方法及其性能研究

目的为制备出满足骨缺损修复需要的具有一定力学强度和生物活性的骨组织工程支架,本文选取聚己内酯(polycaprolactone, PCL)和纳米氧化锆(ZrO_2)粉末制备出三维多孔复合材料支架。方法采用高温熔融挤出3D打印方式制备PCL/ZrO_2复合材料支架,为获取支架的几何形态、力学性能和生物学性能,利用扫描电子显微镜(scanning electron microscope, SEM)和万能试验机(material testsystem,MTS)分别分析了支架的形貌和压缩性能,并通过体外细胞培养的方式测试复合材料支架的生物相容性。结果制备完成的复合材料支架具有良好的三维孔隙结构,孔径≥400μm,孔隙率≥40%。对比纯PCL支架,PCL/ZrO_2复合材料支架的力学性能显著提高,杨氏模量提高0.4倍左右,抗压强度提高0.5倍左右。在体外实验中,细胞培养7 d后PCL/ZrO_2复合材料支架上的细胞增殖对比纯PCL支架有显著提高。结论基于该结果,本文制备出的PCL/ZrO_2生物活性骨组织支架在骨组织工程方面有一定的应用前景。     

编织型丝素纤维人工韧带及其体外降解性能研究

该研究制备了一种丝素纤维人工韧带,分别在PBS和蛋白酶XIV溶液中进行体外降解试验。并对其表面形态、质量损失、降解液pH及力学性能等进行了观察和测试。结果表明,PBS溶液中降解70天后,丝素纤维人工韧带表面形貌和质量损失率没有发生明显变化,力学性能基本保持不变,溶液pH稳定呈中性。而酶降解70天的丝素纤维人工韧带表面发现多根纤维断裂,质量损失率高达18.4%,丝素纤维人工韧带材料直径下降达21.8%,最大断裂强力损失了近50%。降解后溶液的pH值呈弱酸性,且溶液中存在肉眼可见的絮状物。蛋白酶XIV对天然蛋白丝素纤维人工韧带材料具有明显的降解作用。该研究可为体外评价可降解人工韧带降解速率、建立体内外降解性能之间的关系提供参考。     

可生物降解PLA/PCL、PELA/PECL高分子共混体系的早期降解行为——相结构与降解性能的关系

本文以吸水率,GPC、SEM等考察了聚d,1—乳酸(PLA)/聚ε—己内酯(PCL)、聚d,1—乳酸—聚乙二醇(PEG)/聚ε—己内酯—聚乙二醇(PEG)可生物降解共混多相体系的体外降解行为,研究了PH值、共混组成及相容性对降解性能的影响,并就共混物形态结构与降解性能的关系作了讨论。PLA/PCL共混体系,随PLA含量增大,吸水性增强,降解速率加快。PLA/PCL(75/25)共混物表现出较PLA更高的吸水宰,经65天降解,分子量显著下降。由于聚乙二醇链段的亲水性和内增容作用,PELA/PECL(50/50)共混物的吸水率较PLA/PCL(50/50)共混物大为提高。     

Characterization of knitted polymeric scaffolds for potential use in ligament tissue engineering

Different scaffolds have been designed for ligament tissue engineering. Knitted scaffolds of poly-L-lactic acid (PLLA) yarns and co-polymeric yarns of PLLA and poly(glycolic acid) (PLGA) were characterized in the current study. The knitted scaffolds were immersed in medium for 20 weeks, before mass loss, molecular weight, pH value change in medium were tested; changes in mechanical properties were evaluated at different time points. Results showed that the knitted scaffolds had 44% porosity. There was no significant pH value change during degradation, while there was obvious mass loss at initial 4 week, as well as smooth molecular weight drop of PLLA. PLGA degraded more quickly, while PLLA kept its integrity for at least 20 weeks. Young's modulus increased while tensile strength and strain at break decreased with degradation time; however, all of them could maintain the basic requirements for ACL reconstruction. It showed that the knitted polymeric structures could serve as potential scaffolds for tissue-engineered ligaments.     

生物降解材料聚乳酸－聚乙二醇共聚物体内外降解

本文对ＤＬ－聚乳酸－聚乙二醇共聚物（ＰＥＬＡ）体内外降解进行了研究。采用凝胶渗透色层法（ＧＰＣ）测定分子量，扫描电镜（ＳＥＭ）观察。ＰＥＬＡ在最初第５天出现降解，２月时分子量丧失体内外分别为９７．２８％和９２．０％，而重量仅丧失８％。对其原因进行了讨论，同时将ＰＥＬＡ与ＤＬ－聚乳酸（ＰＬＡ）进行了比较，探讨分析了二者的降解机理。结果表明ＰＥＬＡ是一种新型生物降解材料。     

可分解食道支架缝合线体外降解性能的研究

采用磷酸盐缓冲溶液(PBS)(pH=7.4)为降解介质,37℃下对可分解食道支架聚(L-丙交酯)(PLLA)和聚(乙交酯-丙交酯)(PGLA)缝合线进行8周的体外降解实验。通过测试降解过程中其质量损失、pH值、特性粘度、抗张强度、取向度、结晶度、熔点及表面形貌等变化情况,对其体外降解行为进行研究。结果表明PLLA缝合线各项性能无明显变化,而PGLA缝合线各项性能发生了显著变化。随着降解进行PGLA缝合线的pH值、特性粘度、抗张强度、取向度和结晶度逐渐下降,质量损失率增加,6周时抗张强度几乎为零,8周时质量损失率近70%。DSC结果表明,随着体外降解PGLA缝合线晶区熔点保持不变,晶区的熔融热焓逐渐增加,而无定形区产生新的有序区.并且含量不断增加。SEM结果表明PGLA缝合线在降解过程中,涂层首先脱落,然后线体以横向断裂方式断裂。因此,PGLA缝合线适用于良性食道狭窄的可分解食道支架,而PLLA缝合线制备的支架分解时间大于2个月,不适于良性狭窄的治疗。     

In vitro degradation of polymeric networks of poly(propylene fumarate) and the crosslinking macromer poly(propylene fumarate)-diacrylate

Polymeric networks of poly(propylene fumarate) (PPF) crosslinked with poly(propylene fumarate)-diacrylate (PPF-DA) are currently being investigated as an injectable, biodegradable bone cement. This study examined the effect of crosslinking density, medium pH, and the incorporation of a beta-tricalcium phosphate (beta-TCP) filler on the in vitro degradation of PPF/PPF-DA. Cylindrical specimens were submerged in buffered saline at 37 degrees C and the change in weight, geometry, and compressive mechanical properties were monitored over a 52-week period. All formulations showed an initial increase in modulus and yield strength over the first 12 weeks, achieving maxima of 1307+/-101 and 51+/-3MPa, respectively, for the beta-TCP composite. PPF/PPF-DA networks with the lower crosslinking density demonstrated the greatest degradation with a 17% mass loss. Samples in the lower buffer pH 5.0 compared to physiological pH 7.4 did not show any differences in mass loss, but exhibited a faster decrease in the compressive strength over time. The beta-TCP composites maintained their mechanical properties at the level following their initial increase. These results show that the degradation of PPF/PPF-DA networks can be controlled by the crosslinking density, accelerated at a lower pH, and prolonged with the incorporation of the beta-TCP filler.     

Degradation of composite materials composed of tricalcium phosphate and a new type of block polyester containing a poly(L-lactic acid) segment

Degradation of a new type of poly(L-lactic acid)/poly(ethylene; hexamethylene/ sebacate) block polyester and its composite containing 10 and 30 wt% tricalcium phosphate (TCP) were studied in vitro. Film specimens of thickness 100 and 250 microm for each of the three materials were immersed in phosphate buffered saline (pH 7.4) at 37 degrees C for up to 24 weeks. At appropriate intervals, water absorption, dry and wet tensile strength, molecular weight, and thermal properties of the specimens were measured by weighing, tensile strength testing, size exclusion chromatography, and differential scanning calorimetry, respectively. The decrease in tensile strength was greater in the unblended and thicker polymer film than in the other five films. The retention of tensile strength after 24 weeks increased with increasing TCP content. This trend was also noticed in the retention of molecular weight. The tensile strength of the materials having molecular weights below 5 x 10(4)-6 x 10(4) Mw or 2 x 10(4)-3 x 10(4) Mn dropped substantially and the materials became fragile. Blending of TCP to the PLLA block polyester retarded degradation, suggesting that TCP neutralized the carboxyl end groups formed by hydrolysis of ester bonds.     

Polymers for biodegradable medical devices. VII. Hydroxybutyrate-hydroxyvalerate copolymers: degradation of copolymers and their blends with polysaccharides under in vitro physiological conditions

The hydrolytic degradation of hydroxybutyrate-hydroxyvalerate copolymers was monitored in vitro at 37 degrees C and pH 7.4. Direct use of bulk properties such as weight loss and tensile strength did not reveal substantial changes in the polymer matrix over degradation periods of several months. Despite this, the polymers were demonstrated to undergo significant modification during this period, in ways that markedly influence their subsequent behaviour. Combined use of goniophotometry and surface energy measurements revealed that surface modification begins at an early stage and is accompanied by diffusion of water into the matrix and a progressive increase in polymer porosity. Relatively little change in the molecular weight and some increase in the crystallinity of the matrix occurred during these early months. As a result, the tensile strength of the polymer varies little in this period. As the porosity of the matrix increases, hydrolytic chain scission within the matrix and diffusion out of degradation products proceeds more effectively. Decrease in matrix molecular weight, increase in matrix erosion, weight loss and loss of tensile strength began at a much more dramatic rate. The apparent resistance of the polymer to degradation in the early months is followed by an accelerated degradation phase around and beyond 1 yr. The use of filters that can dissolve or hydrolytically degrade more rapidly than the hydroxybutyrate matrix accelerates the development of porosity within the matrix and thus enhances the decomposition process.     

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。     

Porous calcium polyphosphate scaffolds for bone substitute applications -- in vitro characterization

Porous structures were formed by gravity sintering calcium polyphosphate (CPP) particles of either 106-150 or 150-250 microm size to form samples with 30-45 vol% porosity with pore sizes in the range of 100 microm (40-140 microm). Tensile strength of the samples assessed by diametral compression testing indicated relatively high values for porous ceramics with a maximum strength of 24.1 MPa for samples made using the finer particles (106-150 microm). X-ray diffraction studies of the sintered samples indicated the formation of beta-CPP from the starting amorphous powders. In vitro aging in 0.1 M tris-buffered solution (pH 7.4) or 0.05 M potassium hydrogen phthalate buffered solution (pH 4.0) at 37 degreesC for periods up to 30d indicated an initial rapid loss of strength and P elution by 1 d followed by a more gradual continuing strength and P loss resulting in strengths at 30d equal to about one-third the initial value. The observed structures, strengths and in vitro degradation characteristics of the porous CPP samples suggested their potential usefulness as bone substitute materials pending subsequent in vivo behaviour assessment.     

Design of bioinspired polymeric materials based on poly(D,L-lactic acid) modifications towards improving its cytocompatibility

To design novel bioinspired polymeric material, poly(D,L-lactic acid) (DL-PLA) was on the base and modified in the bulk. Firstly, maleic anhydride (MA) groups were introduced to the side chain of DL-PLA by the way of melting free radical copolymerization using benzoyl peroxide as an initiator. Then, to neutralize the acid generated during DL-PLA degradation, aliphatic diamine was immobilized by the N-acylation of anhydrides with butanediamine. As the following stage, adhesive peptides Arg-Gly-Asp-Ser (RGDS) were grafted into the backbone of DL-PLA by using carbodiimide as a coupling agent, in order to endow DL-PLA with bioactivity and biospecificity. The characterizations of the obtained polymers were by the means of GPC-MALLS, FTIR, (13)C NMR and XPS to explore the structures and rhodamine-carboxyl interaction method, ninhydrin reaction and amino acid analyzer to determine the content of MA, butanediamine, and RGDS, respectively, followed the test of pH changes during degradation in distilled water (pH = 6.45). Finally, the osteoblast behavior on different DL-PLA based films was investigated and the results indicated that the introduction of diamine could promote cell attachment and viability, and the incorporation of RGDS further improved its cytocompatibility. The synthetic DL-PLA based bioinspired material may have potentials for tissue engineering and other biomedical applications.