Fabrication of nanofibrous macroporous scaffolds of poly(lactic acid) incorporating bioactive glass nanoparticles by camphene-assisted phase separation

Here we produced macroporous and nanofibrous scaffolds with bioactive nanocomposite composition, poly(lactic acid) (PLA) incorporating bioactive glass nanoparticles (BGnp) up to 30 wt%, targeting bone regeneration. In particular, the nanofibrous structure in the scaffolds was generated by using a bicyclic monoterpene, camphene (C₁₀H₁₆), through a phase-separation process with PLA-BGnp phase in chloroform/1,4-dioxane co-solvent. Furthermore, macropores were produced by the impregnation of salt particles and their subsequent leaching out, followed by freezing and lyophilization processes. The produced PLA-BGnp scaffolds presented highly porous and nanofibrous structure with porosities of 90–95% and pore sizes of over hundreds of micrometers. BGnp with sizes of ∼90 nm were also evenly impregnated within the PLA matrix, featuring a nanocomposite structure. The nanofibrous scaffolds exhibited enhanced hydrophilicity and more rapid hydrolytic degradation as the incorporated BGnp content increased. The bone-bioactivity of the scaffolds was substantially improved with the incorporation of BGnp, exhibiting rapid formation of apatite throughout the scaffolds in a simulated body fluid. The developed macroporous and nanofibrous scaffolds with PLA-BGnp bioactive composition are considered as a novel 3D matrix potentially useful for bone tissue engineering.     

单一热致相分离法制备聚乳酸纳米纤维大孔支架

在不结合其它致孔方法的条件下,基于单一的热致相分离的方法,采用聚左旋乳酸(PLLA),二氧六环,水三元体系,测量了体系的浊点和凝胶点,并在此基础之上系统地研究了溶液浓度,溶剂配比,凝胶温度,凝胶时间对支架大孔,纳米纤维的影响,在质量分数为5%,m(溶剂配比二氧六环)/m(水)=87/13,凝胶温度25℃,凝胶时间15min的条件下,制备了含有100μm以上大孔,同时孔壁上分布均匀的纳米纤维的PLLA支架,孔隙均匀,连通性很好。     

熔融缩聚合成聚乳酸-聚乙二醇共聚物及其性能研究

采用羧基封端乳酸预聚物与聚乙二醇熔融缩聚合成了聚乳酸-聚乙二醇共聚物,并用GPC、FTIR、1H-NMR等方法表征了预聚物与共聚物,结果表明,预聚物的羧基封端率高于95%,预聚物的相对分子质量可由投料比(物质的量比)控制.热分析结果表明,共聚物中聚乳酸链段呈无规分布,而聚乙二醇链段能够形成结晶微区.力学性能测试结果表明,共聚物的断裂伸长率达371%,有望在聚乳酸韧性改性方面得到应用.     

Poly(lactide-co-glycolide)/hydroxyapatite nanofibrous scaffolds fabricated by electrospinning for bone tissue engineering

Poly(lactide-co-glycolide) (PLGA) nanofibrous composite scaffolds having nano-hydroxyapatite particles (HAp) in the fibers were prepared by electrospinning of PLGA and HAp with an average diameter of 266.6 ± 7.3 nm. Microscopy and spectroscopy characterizations confirmed integration of the crystalline HAp in the scaffolds. Agglomerates gradually appeared and increased on the fiber surface along with increase of the HAp concentration. In vitro mineralization in a 5 × simulated body fluid (SBF) revealed that the PLGA/HAp nanofibrous scaffolds had a stronger biomineralization ability than the control PLGA scaffolds. Biological performance of the nanofibrous scaffolds of the control PLGA and PLGA with 5 wt% HAp (PLGA/5HAp) was assessed by in vitro culture of neonatal mouse calvaria-derived MC3T3-E1 osteoblasts. Both types of the scaffolds could support cell proliferation and showed sharp increase of viability until 7 days, but the cells cultured on the PLGA/5HAp nanofibers showed a more spreading morphology. Despite the similar level of the cell viability and cell number at each time interval, the alkaline phosphatase secretion was significantly enhanced on the PLGA/5HAp scaffolds, indicating the higher bioactivity of the as-prepared nano-HAp and the success of the present method for preparing biomimetic scaffold for bone regeneration.     

聚乳酸单轴拉伸膜的包装特性研究

目的研究了不同拉伸比的PLLA薄膜的热学性能、阻隔性能和热收缩性能。方法采用双螺杆挤流延试验机单轴拉伸制备了不同拉伸比的PLLA热收缩膜和定向拉伸膜,采用差示扫描量热分析仪(DSC)、透湿仪和透氧仪对不同拉伸比的PLLA薄膜的热学性能和阻隔性能进行了评估,并对PLLA膜的热收缩性进行了测定。结果热收缩膜的拉伸比由1增大到6.5时,PLLA的结晶度由0.2%增加到41.8%,结晶速率明显提高,阻隔性得到了一定的改善。随着拉伸比例的增大,热收缩率随之增大。定向拉伸膜的结晶度得到了大幅度提高,其阻隔性也得到了改善,但不呈现热收缩性。结论通过单轴拉伸可以有效地提高PLLA薄膜的结晶速率和结晶度,经过中等拉伸比例的PLLA薄膜,其阻湿阻氧能力相对较强。     

聚丙烯酸-聚乳酸接枝共聚物涂膜的制备及性能

采用溶液聚合法合成了生物降解材料聚丙烯酸-聚乳酸接枝共聚物(PAA-g-PLLA),通过红外、核磁和凝胶渗透色谱对其结构进行了表征,测定了涂膜的附着力、黏度和硬度等基本性能。正交实验结果表明最佳的合成工艺条件为:硬软单体的质量比为55∶35,过氧化苯甲酰(BPO)的用量为3%,反应温度为85℃,甲基丙烯酸羟乙酯-聚乳酸大单体(HEMA-PLLA)与软硬单体的质量比为1∶2,单体与溶剂的质量比为2∶2。对比聚丙烯酸涂膜和PAA-g-PLLA涂膜的接触角,以及PLLA降解性能看出,PAA-g-PLLA涂膜具有降低表面能和自抛光的双重特性。     

聚乳酸无机成核剂的研究进展

聚乳酸已然成为生物可降解塑料领域的主导品种,但仍存在结晶速率慢、耐热性差等缺陷,尤其是结晶速率慢严重制约其发展.无机物由于价格低廉、来源广泛已被广泛应用于提高聚乳酸的结晶速率.对此,概述了无机物提高聚乳酸结晶速率的理论基础,重点综述了无机物尤其是层状硅酸盐对提高聚乳酸结晶速率的研究进展,并展望了聚乳酸无机成核剂以后的发展方向.     

原位反应挤出制备聚乳酸与聚醚酯嵌段共聚物合金的性能研究

以0.35%(质量分数)的过氧化二异丙苯(DCP)为引发剂和2%(质量分数)的马来酸酐(MAH)为增容剂,通过原位反应挤出的方法制备了聚乳酸(PLLA)/聚醚酯嵌段共聚物(TPEE)合金。利用TG、差示扫描量热(DSC)、SEM等研究了其热性能和相形态,并测试了合金的力学性能和熔体流动速率。结果表明,在引发剂DCP的存在下,MAH的添加使得反应挤出制备的合金中PLLA与TPEE之间产生部分共价键连接而增加了相容性。合金的热稳定性、韧性随TPEE含量的增加而升高,但模量和强度下降。另外,不同TPEE含量的合金的熔体流动速率均高于纯PLLA和TPEE,表明在原位反应挤出过程中PLLA与TPEE均发生了一定程度的降解反应。同时,对合金的流变性能也进行了研究。     

聚L-乳酸/环糊精复合材料性能研究

为制备具有功能性的聚乳酸复合材料,以聚L-乳酸(PLLA)和α-环糊精(α-CD)为原料,通过熔融共混技术制备PLLA/α-CD复合材料。研究结果显示α-CD促进了PLLA的结晶,提高了PLLA的结晶速率,但材料变脆;而PLLA/α-CD复合材料非等温结晶后的熔融行为则地受到降温速率的强烈影响,降温速率的增加使得PLLA/α-CD复合材料由单熔融峰转变为双熔融峰。热分解性能研究结果则表明添加α-CD能使PLLA的热分解温度升高。     

The double porogen approach as a new technique for the fabrication of interconnected poly(L-lactic acid) and starch based biodegradable scaffolds

One of the most widely used fabrication methods of three dimensional porous scaffolds involves compression moulding of a polymer salt mixture, followed by salt leaching. However, the scaffolds prepared by this technique have typically limited interconnectivity. In this study, besides salt particles, an additional polymeric porogen, poly(ethylene oxide), PEO, was added to poly(L-lactic acid), PLLA, to enhance the interconnectivity of the scaffolds. Compression moulded specimens were quenched and put into water, where PEO crystallized and phase separated. Following the leaching of PEO fraction, the permeability and interconnectivity among the macropores formed by salt leaching could be observed. The porosities obtained in the prepared scaffolds were between 76 to 86%. Moreover, the highest porosity of 86% was obtained with minimum fraction of total porogen. The water absorption of the porous scaffolds prepared with PEO could vary between 280 to 450% while water uptake of pure PLLA scaffolds was about 93%. The increase of interconnectivity induced by compounding PLLA with PEO could also be obtained in porous PLLA/starch blends and PLLA/hydroxyapatite composites demonstrating the versatility and wide applicability of this preparation protocol. The simplicity of this organic solvent free preparation procedure of three-dimensional porous scaffolds with high interconnectivity and high surface area to volume ratio holds a promise for several tissue engineering applications.     

γ-辐照L型聚乳酸的结构与性能研究

考察了辐射剂量(D)在0～25 kGy范围和空气气氛下,γ-辐照对L型聚乳酸(PLLA)的粘均分子量(-Mη)、力学性能、热稳定性和化学结构的影响.结果表明:在0～15 kGy的剂量范围内,所研究的PLLA的-Mη随D增大而减小;而在15～25 kGy的剂量范围内,其-Mη则随D的增大而提高;PLLA的拉伸和弯曲性能受D的影响较小,而它的冲击强度随D的增大而呈现升高的趋势;PLLA的热分解温度因γ-辐照则有所下降,γ-辐照使PLLA的化学结构略有变化.     

Polysaccharide nanofibrous scaffolds as a model for in vitro skin tissue regeneration

Tissue engineering and nanotechnology have advanced a general strategy combining the cellular elements of living tissue with sophisticated functional biocomposites to produce living structures of sufficient size and function at a low cost for clinical relevance. Xylan, a natural polysaccharide was electrospun along with polyvinyl alcohol (PVA) to produce Xylan/PVA nanofibers for skin tissue engineering. The Xylan/PVA glutaraldehyde (Glu) vapor cross-linked nanofibers were characterized by SEM, FT-IR, tensile testing and water contact angle measurements to analyze the morphology, functional groups, mechanical properties and wettability of the fibers for skin tissue regeneration. The cell-biomaterial interactions were studied by culturing human foreskin fibroblasts on Xylan/PVA Glu vapor cross-linked and Xylan/PVA/Glu blend nanofibrous scaffolds. The observed results showed that the mechanical properties (72 %) and fibroblast proliferation significantly increased up to 23 % (P < 0.05) in 48 h Glu vapor cross-linked nanofibers compared to 24 h Glu vapor cross-linked Xylan/PVA nanofibers. The present study may prove that the natural biodegradable Xylan/PVA nanofibrous scaffolds have good potential for fibroblast adhesion, proliferation and cell matrix interactions relevant for skin tissue regeneration.     

聚乳酸多孔微球的制备及释药性能

将聚乳酸(PLLA)/四氢呋喃(THF)溶液分散在甘油(连续相)中,通过自乳化结合热致相分离(TIPS)制备一系列PLLA多孔微球,微球由捆束状纳米纤维组成。通过改变PLLA浓度、(PLLA/THF)∶甘油比值、溶剂种类以及淬火温度等条件研究所得多孔微球结构与形貌。结果表明,PLLA的质量分数为2%~5%、m(PLLA/THF)∶m(甘油)=1∶3、-20℃和-196℃淬火均能得到形状规整的PLLA多孔微球。多孔微球孔隙率和比表面积最高可达95.44%和32.53m2/g。PLLA多孔微球对牛血清蛋白的药载量为0.355 mg/mg,30 h内释放率达到59.8%,是一种非常良好的药物缓释载体。     

Preparation and characterization of bioactive and biodegradable Wollastonite/poly(D,L-lactic acid) composite scaffolds

Composite scaffolds of poly(D,L-lactic acid) (PDLLA) with bioactive wollastonite were fabricated by the conventional solvent casting-particulate leaching method. The pore structures and morphology of the scaffolds were determined by scanning electron microscopy (SEM). The bioactivity of the composites was evaluated by soaking in a simulated body fluid (SBF), and the formation of the hydroxyapatite (HAp) layer was determined by SEM and energy-dispersive spectrometer. The results showed that the wollastonite/PDLLA composites were bioactive as it induced the formation of HAp on the surface of the composite scaffolds after soaking in SBF for seven days. In addition, pH and ion concentration changes of SBF solutions with composite scaffolds were examined. The results showed that the composites could release Ca and Si ions, which could neutralize the acidic degradation by-products of the PDLLA, and stabilize the pH of the SBF solutions between 6.7 and 7.2 within a three-week soaking period. Furthermore, the measurements of the water contact angles suggested that incorporation of wollastonite into PDLLA could improve the hydrophilicity of the composites and the enhancement was dependent on the wollastonite content. All these results suggest that incorporation of wollastonite into PDLLA might be a useful approach for the preparation of composite scaffolds for tissue repair and tissue-engineering applications.     

聚(L-乳酸)的包装特性研究进展

综述了左旋聚乳酸的包装特性,包括力学性能、结晶性能和气体阻隔性能,讨论了左旋聚乳酸的分子取向、结晶形态、物理老化、共混和多层复合工艺对其包装特性的影响,最后提出了今后在包装领域内对PLLA 主要的工作重点以及展望。     

聚L-乳酸的固态缩聚

采用熔融 /固态缩聚方法制备了聚L 乳酸。考察了不同催化剂、反应温度、反应时间和预聚物颗粒大小对固态缩聚反应速度的影响。结果表明 ,利用真空干燥箱 ,在适宜的反应条件下反应 ,有利于最终聚合物分子量的控制。     

一种可促进成骨细胞黏附和生长的聚乙二醇接枝聚乳酸材料

用氨基封端聚乙二醇(H2N-PEGNH2)对聚乳酸(PLA)进行了本体改性,通过FITC荧光标记牛血清白蛋白(FITC-BSA)对材料的抗非特异性蛋白吸附性能进行了检测,在材料上体外培养Wistar大鼠成骨细胞,检测了材料的细胞相容性.结果表明:与聚乳酸相比,得到的产物聚乙二醇改性聚乳酸(PPLA)明显降低了对牛血清白蛋白的非特异性吸附,仅为PLA的37.3%,显著促进了成骨细胞的黏附和生长.由于该材料具有良好的亲水性、可降解性、细胞相容性及可反应性,预计在组织工程和药物缓释中有潜在应用.     

Bio-functionalized PCL nanofibrous scaffolds for nerve tissue engineering

Surface properties of scaffolds such as hydrophilicity and the presence of functional groups on the surface of scaffolds play a key role in cell adhesion, proliferation and migration. Different modification methods for hydrophilicity improvement and introduction of functional groups on the surface of scaffolds have been carried out on synthetic biodegradable polymers, for tissue engineering applications. In this study, alkaline hydrolysis of poly (ε-caprolactone) (PCL) nanofibrous scaffolds was carried out for different time periods (1 h, 4 h and 12 h) to increase the hydrophilicity of the scaffolds. The formation of reactive groups resulting from alkaline hydrolysis provides opportunities for further surface functionalization of PCL nanofibrous scaffolds. Matrigel was attached covalently on the surface of an optimized 4 h hydrolyzed PCL nanofibrous scaffolds and additionally the fabrication of blended PCL/matrigel nanofibrous scaffolds was carried out. Chemical and mechanical characterization of nanofibrous scaffolds were evaluated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle, scanning electron microscopy (SEM) and tensile measurement. In vitro cell adhesion and proliferation study was carried out after seeding nerve precursor cells (NPCs) on different scaffolds. Results of cell proliferation assay and SEM studies showed that the covalently functionalized PCL/matrigel nanofibrous scaffolds promote the proliferation and neurite outgrowth of NPCs compared to PCL and hydrolyzed PCL nanofibrous scaffolds, providing suitable substrates for nerve tissue engineering.     

成核剂己二酸二苯甲酰肼对聚乳酸性能的影响

针对聚乳酸左旋度低导致其结晶能力差的缺陷,以己二酸为原料经酰化和氨化反应合成了己二酸二苯甲酰肼,在考察其热稳定性和几何空间结构基础上,采用差示扫描量热仪、X射线衍射仪和熔融指数仪研究其对聚乳酸结晶性能和流动性的影响。结果显示,己二酸二苯甲酰肼具有良好的热稳定性,可显著加速聚乳酸的结晶。当己二酸二苯甲酰肼的质量分数在1.5%到3%时,对聚乳酸具有更好的结晶成核效应,尤其是质量分数3%的己二酸二苯甲酰肼可使聚乳酸的起始结晶温度从101.4℃提高到117.6℃,结晶峰值温度从94.5℃提高到110.7℃。而当己二酸二苯甲酰肼在聚乳酸中的质量分数大于1.5%时,可提高聚乳酸树脂的流动性。