PLGA组织工程支架材料在SBF中的降解性能和生物矿化性能

本文采用pH值测量、特性粘度、失重、DSC和电子探针的研究方法,研究了PLGA组织工程支架在模拟体液中的降解性能和生物矿化性能。研究发现随着在SBF中浸泡时间的增长,PLGA支架材料的分子量不断下降;浸泡在SBF中的PLGA组织工程支架材料的重量由沉积进程和降解进程共同决定;DSC测试显示,浸泡在SBF中的PLGA组织工程支架材料的羟基乙酸单元(GA)相对于乳酸单元(LA)更易降解;电子探针测试显示,浸泡在SBF中的PLGA组织工程支架材料表面有磷酸盐沉积物产生。     

支架结构对聚乳酸组织工程支架在SBF溶液中降解进程的影响

本文通过对不同孔隙率和不同孔径的聚乳酸组织工程支架在模拟体液（SBF）中的降解性能的研究,探讨支架结构对聚乳酸组织工程支架在SBF溶液中降解进程的影响.研究发现：孔径适中的200-300微米致孔剂制得的聚乳酸组织工程支架材料在降解1周后比其它两种孔径（致孔剂粒径100微米以下、致孔剂粒径300-400微米）的支架材料的分子量更高,支架的降解性能更稳定;孔隙率越高支架材料的分子量降低得越慢.聚乳酸组织工程支架的失重率并不随着降解时间的增长而逐步增大,而是呈起伏状态,这是由于组织工程支架在SBF溶液中既有降解进程,又有沉积进程造成的.     

聚乳酸组织工程支架在SBF溶液中的降解和矿化性能

本文利用扫描电镜、X射线衍射仪以及红外漫反射仪,并通过对聚乳酸组织工程支架在模拟体液(SBF)中的失重率、分子量以及模拟体液pH值变化的测试,系统地研究了聚乳酸组织工程支架在模拟体液中的降解和矿化性能。结果发现:在模拟体液中,随着时间的增长,聚乳酸组织工程支架的分子量不断下降;但是其重量并不随着时间的增长而减小,而是有升有降。X-射线衍射图谱和FTIR漫反射图谱研究表明,在模拟体液中,聚乳酸组织工程支架的表面有磷灰石沉积物出现。     

PLGA/HA骨支架材料的降解特性

采用有机泡沫法获得了HA多孔骨架.运用溶胶浇铸法将PLGA溶胶填充入多孔骨架中,制备出骨组织工程用PLGA/HA复合支架材料,并考察了其在模拟体液中的降解性能,通过SEM观察了其表面组织形貌.结果表明,随浆料中HA含量的增加,材料降解后质量损失增大,且随降解时间的延长,PLGA/HA骨支架材料表面粘附的磷灰石相增多,表明该复合材料具有良好的生物活性.     

聚丙交酯-乙交酯聚合物(PLGA)涂层体外降解行为研究

为了防止心血管支架植入后再狭窄的发生,目前采用将抑制平滑肌细胞生长的药物通过高分子载体涂在支架表面.由于支架植入体内后,涂层受到血液冲刷作用.本工作采用可降解高分子材料PLGA作为载体,将PLGA薄膜置于体外循环冲刷装置中,在37℃、pH7.4的Hank's模拟体液、模拟血流冲刷作用下的体外降解,并与静态降解作为对比.采用SEM、GPC、1H-NMR和DSC技术研究了聚合物在降解过程中形貌、分子量及分子量分布、失重率、组成和热性能的变化,并对降解机理进行探讨.与静态降解相比较,在流动体液中,高分子载体表面形貌、失重率以及分子量变化均较慢.上述结果与表面微环境有关.     

镁合金支架双重可控释放涂层的制备及药物释放性能研究

在镁合金支架材料WE42表面制备了双重可控腐蚀和药物缓释涂层,并对其药物释放性能进行了研究.DSC研究表明紫杉醇均匀分散在PLGA体系中.药物释放实验表明,PLGA可使紫杉醇长期持续释放,突释较弱,释放是由扩散-降解控制.随载药膜中PEG分子量和含量的增加,药物释放率增加.外层明胶涂层能有效降低药物释放率,延长药物释放时间.     

β-磷酸三钙/聚乳酸组织工程支架在模拟体液中的降解和矿化性能

利用扫描电镜、X射线衍射仪、红外漫反射仪,以及对β-磷酸三钙/聚乳酸组织工程支架在模拟体液(SBF)中失重率和模拟体液pH值的变化的测试,系统研究了聚乳酸组织工程支架在模拟体液中的降解和矿化性能。结果发现,随着β-磷酸三钙/聚乳酸组织工程支架在模拟体液中浸泡时间的增长,模拟体液的pH值有下降趋势;支架材料的质量是降解和矿化作用共同影响的结果。X射线衍射图谱和红外光谱(FT-IR)漫反射图谱研究表明,浸在SBF中的支架表面有磷灰石沉积物出现,且沉积物与β-磷酸三钙的晶型相似。     

β-磷酸三钙/聚乳酸组织工程支架在模拟体液中的降解和矿化性能EI北大核心CSCD

利用扫描电镜、X射线衍射仪、红外漫反射仪,以及对β-磷酸三钙/聚乳酸组织工程支架在模拟体液(SBF)中失重率和模拟体液pH值的变化的测试,系统研究了聚乳酸组织工程支架在模拟体液中的降解和矿化性能。结果发现,随着β-磷酸三钙/聚乳酸组织工程支架在模拟体液中浸泡时间的增长,模拟体液的pH值有下降趋势;支架材料的质量是降解和矿化作用共同影响的结果。X射线衍射图谱和红外光谱(FT-IR)漫反射图谱研究表明,浸在SBF中的支架表面有磷灰石沉积物出现,且沉积物与β-磷酸三钙的晶型相似。     

PLA-PEG-PLA/PLA组织工程支架在模拟体液中的降解和生物矿化性能

系统研究了含有聚乳酸-聚乙二醇-聚乳酸嵌段共聚物(PLA-PEG-PLA)的聚乳酸组织工程支架在模拟体液(SBF)中的降解和生物矿化性能。通过研究可以得到如下结论:随着含有PLA-PEG-PLA共聚物的聚乳酸组织工程支架在模拟体液中浸泡时间的增长,模拟体液的pH值有下降趋势;支架材料的质量有升有降,是降解和矿化作用共同影响的结果。X射线衍射图谱和FT-IR漫反射图谱研究表明,浸在SBF中的支架表面有磷灰石沉积物出现,并且PLA-PEG-PLA共聚物降解速度比PLA快。     

负载PEO-b-PLL/DNA-TGF beta1粒子的PLGA/纤维蛋白凝胶复合支架的制备及其体外干细胞诱导分化性能

采用粒径分布在450～600μm的无规明胶颗粒为致孔剂制备乳酸-乙醇酸共聚物(PLGA)海绵体,以纤维蛋白凝胶为负载聚氧化乙烯-b-聚赖氨酸(PEO-b-PLL)/DNA粒子和骨髓间充质干细胞(BMSCs)的传递介质,通过负压将其导入PLGA多孔支架,在凝血酶和Ca2+作用下原位凝胶,构建了一种负载PEO-b-PLL/DNA粒子的PLGA/纤维蛋白凝胶/BMSCs复合支架。系统地表征了复合支架的形貌及微结构。考察了PLGA海绵体和纤维蛋白水凝胶的体外降解性能以及PEO-b-PLL/DNA粒子的体外释放行为。重点研究了BMSCs在复合支架中的形态、活性和向软骨细胞分化等生物学性能。研究结果表明:PLGA海绵体具有高孔隙率、高孔连通性;纤维蛋白凝胶均匀填充在PLGA海绵体孔隙中,而PEO-b-PLL/DNA粒子分布在纤维蛋白凝胶三维结构中;体外降解实验显示,8周后PLGA分子量为初始分子量的50%以下,而伴随着纤维蛋白凝胶的快速降解,PEO-b-PLL/DNA粒子被快速释放到溶液中;体外细胞培养结果显示,BMSCs在复合支架体系中具有良好的形态、活性和分泌软骨细胞外基质的能力。     

A study on the in vitro degradation of poly(L-lactide)/chitosan microspheres scaffolds

Recent research shows that the addition of chitosan microspheres (CMs) to poly(L-lactide) (PLLA) can result in a composite scaffold material with improved biocompatibility and mechanical properties for tissue engineering applications. However, research regarding the influence of CMs on scaffold degradation is absent in the literature. This paper presents a study on the in vitro degradation of scaffolds made from PLLA with CMs. In this study, the PLLA/CMs scaffolds with a 25% ratio of CMs to PLLA were immersed in phosphate-buffered saline (PBS) solution at 37°C for 8 weeks. The in vitro degradation of the scaffolds was investigated using micro-computed tomography (μCT), weight loss analysis, Raman spectroscopy, and differential scanning calorimetry (DSC). Microstructure changes during degradation were monitored using μCT. The μCT results were consistent with the results obtained from Raman spectra and DSC analysis, which reflected that adding CMs into PLLA can decrease the degradation rate compared with pure PLLA scaffolds. The results suggest that PLLA/CMs scaffold degradation can be regulated and controlled to meet requirements imposed a given tissue engineering application.     

A cellular automaton simulation of the degradation of porous polylactide scaffold: I. Effect of porosity

A cellular automaton method that includes a fabricating model for solvent casting/porogen leaching and a multiple-particle random walk model for oligomer molecular diffusion was used to simulate degradation behaviors and their dependence on the initial porosities (80%, 90% and 95%) of porous polylactide (PLA) scaffolds. Changes in the mass loss, molecular weight, numbers of PLA chains and ester groups, oligomer molecules release and average degradation rate with degradation time were investigated. The results show that during degradation, higher initial porosity resulted in greater molecular weight and a higher average number of ester groups and less mass loss, a lower number of oligomer molecules being released and a lower ratio of oligomer molecules remaining in the scaffold to those in the whole model. The average degradation rate and average number of PLA chains initially changed in direct proportion to the initial porosity, but there was an inverse change later in the degradation. In addition, no hollow structures were found in any of the scaffolds during the degradation, which indicates there was no dramatic autocatalytic phenomenon such as that seen for massive solid structures such as a plate in the porous PLA scaffold. The above simulated results are consistent with recent experimental reports, suggesting our simulating method has potential application in studying the degradation behaviors of porous scaffolds for tissue engineering.     

左旋聚乳酸/多壁碳纳米管/羟基磷灰石电纺丝纳米纤维的形态及生物降解性能

采用静电纺丝法制备了左旋聚乳酸/多壁碳纳米管/羟基磷灰石(PLLA/MW NT s/HA)杂化纳米纤维无纺毡,分析了MW NT s的加入对杂化纤维形态结构的影响,以及不同工艺条件下纤维的直径分布,并研究了纤维无纺毡在磷酸盐缓冲溶液(pH 7.4,37℃)中的体外降解过程。结果表明:MW NT s的加入使PLLA/HA纤维直径略有减小;PLLA/MW NT s/HA杂化纤维体系降解液的pH值下降到一定程度后,在降解后期呈缓慢上升趋势;碱性MW NT s/HA的加入抑制了PLLA降解过程中的自催化作用,减缓了PLLA的降解速度。     

Preparation and characterization of oxidized alginate covalently cross-linked galactosylated chitosan scaffold for liver tissue engineering

Liver tissue engineering (LTE) requires a perfect extracellular matrix (ECM) for hepatocytes culture to maintain high level of liver-specific functions. Here, we reported a LTE scaffold derived from oxidized alginate covalently cross-linked galactosylated chitosan via Schiff base reaction, without employing any extraneous chemical cross-linking agent. The structure of galactosylated chitosan (GC) and oxidized alginate was confirmed by Fourier transformed infrared (FTIR) spectra, proton nuclear magnetic resonance (¹H-NMR) spectroscopy, X-ray diffraction (XRD) or thermogravimetric (TG) analysis. The structure and properties of a series of the scaffolds were characterized by FTIR, XRD, scanning electron microscopy (SEM), porosity, equilibrium swelling, mechanical properties, thermal stability and in vitro degradation. FTIR spectra confirmed the characteristic peak of Schiff base groups in the scaffolds and XRD indicated the scaffolds could be amorphous. SEM analysis showed that the scaffolds displayed highly porous surfaces with average pore size of 50-150 μm and interconnected pore structure in the internal structure with average pore size of 100-250 μm. Porosity measurement suggested the scaffolds had a porosity of about 70%. The compressive modulus of the scaffolds (hydrated) was in the range of 4.2-6.3 kPa. Further studies showed that, with the increase of the oxidized alginate content, the equilibrium swelling and in vitro degradation rate of the scaffolds decreased and the thermal stability slightly increased, which might mainly attribute to the difference of the degree of cross-linking and the nature properties of the raw materials. Additionally, the biocompatibility of the scaffolds was evaluated in vitro. The results showed that the hepatocytes cultured on the scaffolds had a typical spheroidal morphology, formed multi-cellular aggregates and presented perfect integration with the scaffolds, which suggested that the scaffolds may be potential candidates for LTE strategies.     

Vibrational and thermal study on the in vitro and in vivo degradation of a poly(lactic acid)-based bioabsorbable periodontal membrane

Fourier transform Raman (FT-Raman), attenuated total reflection/Fourier transform infrared (ATR/FT-IR) spectra and differential scanning calorimetry (DSC) measurements were performed on a poly(lactic acid)-based biodegradable periodontal membrane in order to study its in vitro and in vivo degradation mechanism and kinetics. For this purpose, the hydrolitic in vitro degradation of the membrane was investigated in two aqueous media: saline phosphate buffer (SPB, pH=7.4) and 0.01 M NaOH solution. Moreover, a membrane implanted in vivo for four weeks for treatment of contiguous vertical bony defects, was examined. Vibrational and thermal measurements show that the membrane has a prevalently amorphous structure and is composed of low molecular weight polymeric chains. The degradation is faster in NaOH solution than in SPB and occurs heterogeneously without any significative increase in crystallinity. The DSC and spectroscopic measurements are discussed in comparison with the trend of % weight loss and show a progressive decrease in molecular weight. Regarding the Raman analysis, the I₈₇₅/I₁₄₅₂ intensity ratio was identified as a marker of the degree of degradation. Regarding the in vivo degradation, the presence, spectroscopically revealed, of a biological component entrapped in the membrane proves the good integration of the membrane with the surrounding tissues. The membrane seems to degrade faster in vivo than in vitro. A comparison with the degradation mechanism and kinetics of a periodontal membrane previously studied, Vicryl® periodontal mesh, is made.     

A study on the rate of degradation of the bioabsorbable polymer polyglycolic acid (PGA)

As part of a study to characterise bioabsorbable scaffolds for tissue engineering an investigation has been conducted into the rate of degradation of polyglycolic acid (PGA). This is one of the most commonly used bioabsorbable materials and has been used in sutures since the 60s and more recently in cell scaffolds, drug delivery devices and bone fixation pins. This study looks at the influence that surface-to-volume ratio i.e. thickness of material, has on degradation. By degrading various thicknesses of PGA in a buffer saline solution over 24 days and testing their properties at regular intervals, a knowledge of how surface-to-volume ratio affects degradation was developed. Properties such as weight loss, crystallinity, molecular weight and structural integrity were measured. Results showed that rate of mass loss was dependent on sample thickness but crystallinity, melting point and molecular weight were independent of thickness.     

Synthesis and characterization of novel THTPBA/PEG-derived polyurethane scaffolds for tissue engineering

Novel polyurethane (PU) scaffold materials were designed and prepared on the basis of a coupling reaction between tetra-hydroxyl-terminated poly(butadiene-co-acrylonitrile) prepolymer (THTPBA) and poly(ethylene glycol) (PEG) via 1,6-hexamethylene diisocyanate as anchor molecule. The hydrophilicity, degradability, mechanical, and biomedical properties of the THTPBA/PEG PU materials were scrutinized by swelling and goniometry, FTIR and gravimetry methods, tensile stress–strain measurements and hemolysis, platelet activation, dynamic (erythrocyte aggregation) and static coagulation as well as MTT assays. The experimental results indicated that the hydrophilicity and mass loss were enhanced with increased concentrations and molecular weight (MW) of PEG. The degradation may be attributable to the cleavage of urethane or ester bonds in polymer chains. The in vitro blood compatibility and MTT cytotoxicity investigations elicited that the MW of PEG and mass ratios of THTPBA to PEG had important influence on the biomedical properties. The tensile stress–strain investigations showed that the highly crosslinked architecture offered high elastic modulus and mechanical strength. The PU scaffolds with proper component ratios and MW of PEG exhibited improved mechanical properties and biocompatibility as well as low toxicity, and can be employed as potential candidates for blood-contacting applications.     

生物活性玻璃/PLA-PEG-PLA/聚乳酸组织工程支架在SBF溶液中的降解和矿化

通过测定pH值、质量损失率、SEM、XRD和FTIR,系统研究了生物活性玻璃/聚乳酸-聚乙二醇-聚乳酸嵌段共聚物（PLA-PEG-PLA）/聚乳酸组织工程支架在模拟体液（SBF）中的降解和生物矿化性能。研究结果表明：随着支架在SBF溶液中浸泡时间的延长,SBF的pH值和支架的质量呈下降趋势;生物活性玻璃的存在使pH值升高,而PLA-PEG-PLA嵌段共聚物的存在使pH值降低。XRD、FTIR图谱和SEM图像表明：在SBF中浸泡一定时间后,有无定型或结晶不完善的磷灰石在生物活性玻璃/PLA-PEG-PLA/聚乳酸组织工程支架表面沉积形成,并且PLA-PEG-PLA共聚物降解速度比聚乳酸快;在SBF中浸泡7天后,PLA-PEG-PLA共聚物的含量已经很难通过FTIR检测出来。