聚乳酸/纳米羟基磷灰石复合纳米纤维支架的制备与表征

利用热致相分离法制备了纳米羟基磷灰石增强型聚乳酸纳米复合支架,研究了该支架的微观形貌、孔隙率、力学性能和体外降解等特性。扫描电镜显示该复合支架具有纳米纤维状三维网络空间结构。聚乳酸与纳米羟基磷灰石的质量配比为80∶20时,复合支架的压缩模量最高,比纯聚乳酸纳米支架高215%。制备得到的复合支架的孔隙率都大于88％。体外降解结果表明加入纳米羟基磷灰石可有效减缓聚乳酸纳米复合支架的降解速度。     

聚-L-乳酸/β-磷酸三钙多孔支架材料的制备及性能研究

以氯化钠为致孔剂,采用溶液浇铸致孔剂—粒子滤出复合法制备了不同比例梯度(9∶1,8∶2,7∶3)的聚-L-乳酸/β-磷酸三钙(PLLA/β-TCP)复合材料多孔支架,研究了PLLA/β-TCP多孔支架的孔隙率、力学性能、生物相容性。研究结果表明,随着制备过程中致孔剂用量的增加,多孔支架的孔隙率逐渐增加,而与致孔剂的颗粒大小基本无关;致孔剂的颗粒大小只影响多孔支架的孔径;材料的压缩强度和压缩模量随孔隙率的增大而降低;PLLA/β-TCP多孔复合支架材料具有良好的生物相容性。     

气体发泡法制备PLLA/BCP多孔复合支架及其性能研究

用气体发泡法制备的聚乳酸(PLLA)多孔支架,力学性能通常随着孔隙率的增加而降低,且支架表面的疏水性限制着其在骨支架中的应用。通过共混PLLA与双相磷酸钙(BCP)陶瓷粉末,以碳酸氢铵(AB)作为致孔剂,采用气体发泡法制备了PLLA/BCP多孔复合支架,分析了AB粒径对支架孔径的影响以及AB和BCP的含量对PLLA支架力学性能及亲水性能的影响。结果表明,随着AB粒径的增大,支架的孔径尺寸也相应增大;随着AB含量的增加,PLLA/BCP复合支架的孔隙率相应增大、力学性能呈下降趋势;BCP的加入对PLLA支架的孔隙率影响不大,随着BCP含量的增加,支架的力学性能和亲水性能整体上升。通过调节AB的粒径和含量、BCP的含量,控制支架材料的孔隙率(52.2%~82.1%)、力学性能(压缩强度0.52~1.24MPa)以及亲水性能,制备的PLLA/BCP多孔复合支架能更好地满足骨组织工程的要求。     

基于活塞挤出式3D打印制备PLA/PCL生物支架的研究

以聚乳酸(PLA)、聚己内酯(PCL)为原料,乙酰柠檬酸三丁酯为相容剂,采用熔融共混法制备了PCL含量不同的PLA/PCL复合材料,结合新型活塞挤出式三维打印技术打印多孔生物支架,并进行材料的孔隙率计算、接触角测量、表面形貌观察、力学性能测试。结果表明:随着PCL用量的增加,复合材料疏水倾向增大;支架成型难度增加,孔隙率变小,纤维表面变得光滑,压缩强度下降,冲击韧性更好。     

聚乳酸接枝丙烯酸纳米孔纤维膜制备及其细胞相容性研究

以V(二氯甲烷)/V(N,N-二甲基甲酰胺)=4∶1为溶剂,通过电纺制备直径为(650±60)nm,孔径为96 nm×72 nm聚乳酸(PLLA)纳米孔纤维膜。利用氧等离子体处理将亲水性单体丙烯酸(AA)接枝到纤维表面制备聚乳酸接枝丙烯酸(PLLAg-PAA)纳米孔纤维膜。与PLLA纳米孔纤维膜相比,PLLA-g-PAA纳米孔纤维膜的水接触角从(119.4±1.2)°降低到(42.3±0.6)°,拉伸强度、杨氏模量和断裂伸长率略有降低。将牙髓干细胞(DPSCs)在纤维膜支架上培养,细胞生长密度顺序为PLLA-g-PAA纳米孔纤维膜PLLA纳米孔纤维膜PLLA纤维膜。由于PLLA-g-PAA纳米孔纤维膜表面粗糙,比表面积大,孔隙率高和表面亲水性好,更有利于细胞的粘附、迁移、分化和繁殖。PLLA-g-PAA纳米孔纤维膜有望成为优良的组织工程支架材料。     

PLA/HA多孔生物支架的制备及性能研究

以聚乳酸(PLA)、羟基磷灰石(HA)为主要原料,氯化钠为致孔剂,采用溶液共混-粒子沥滤法制备了PLA/HA复合多孔生物支架,并测试研究了该PLA/HA多孔支架的孔隙率、孔隙连通率及力学性能。结果表明:PLA/HA(85/15)复合多孔支架的孔隙率略低于纯PLA多孔支架,可达到81.6%,可以满足组织工程对支架材料的要求。另外,PLA/HA支架材料的弯曲强度和压缩强度均在PLA与HA的质量比为85/15时达到最大值,分别为76.1和75.7 MPa。     

改进粒子沥滤法制备PLA/HA支架及其性能

采用溶剂浇铸/真空挥发/粒子沥滤法(SC/VV/PL)制备了聚乳酸(PLA)和PLA/羟基磷灰石(HA)多孔支架,研究了支架的结构、力学性能、亲水性能等.从扫描电镜结果可以看出支架孔径与所用的致孔剂氯化钠(NaCl)的粒径符合良好,PLA和PLA/HA支架的孔隙率均大于79%,压缩模量、接触角、吸水率的测试结果表明,HA的加入显著改善了PLA支架的力学性能和亲水性能.     

PDLA/(β-TCP/HA)多孔支架的制备

本文用共沉淀法制得的缺钙羟基磷灰石粉末与硬脂酸混合后压制成坯体,在马弗炉中于1050℃烧结得到β-TCP/HA多孔支架。在90kPa压强下将支架浸入聚乳酸溶液,离心后,真空干燥,得到多孔PDLA/(β-TCP/HA)复合支架。用XRD,IR表征复合支架的成分,用SEM观察内部孔隙结构。结果表明,β-TCP/HA多孔支架含有β-TCP和HA两相。复合后的支架抗压强度从2~3 MPa提高到3.5~5 MPa,并且抗压强度随聚乳酸复合量的增加而提高。孔隙结构和连通性基本没有改变,孔隙率略有下降。     

聚苯胺/聚乳酸复合纳米纤维表面形貌对生物相容性的影响

外加电场作用下聚苯胺能够调节细胞附着、增殖、迁移和分化,在体液环境下发生脱掺杂会使聚苯胺基导电可降解纳米纤维电活性减弱,但在一定程度上仍能促进细胞的黏附、生长和增殖。本文选择酒石酸作为聚苯胺在等离子体处理后的聚乳酸纳米纤维表面原位聚合过程中的酸掺杂剂,考察酒石酸与苯胺摩尔比分别在1∶1, 1∶2和1∶4下不同形貌的聚苯胺/聚乳酸复合纳米纤维对生物相容性的影响。采用SEM、TEM和FTIR表征聚苯胺形貌及化学成分,接触角评价其润湿性,MTT、ALP和免疫荧光染色评价聚苯胺/聚乳酸复合纳米纤维生物相容性。结果表明,酒石酸与苯胺摩尔比在1∶1、1∶2和1∶4下的聚苯胺形貌分别为纳米颗粒状、纳米纤维状和纳米空心管状,聚苯胺附着在聚乳酸纳米纤维表面,不会对静电纺丝的多孔结构基体产生影响;聚苯胺/聚乳酸复合纳米纤维表面润湿性良好,有助于细胞的黏附和生长;纳米纤维状的聚苯胺对生物相容性的增强效果明显优于纳米颗粒状聚苯胺,而纳米空心管状结构的聚苯胺对生物相容性增强作用更佳。     

碳纳米管-聚丙烯腈纳米纤维膜的制备及对亚甲基蓝的吸附

采用静电纺丝技术制备碳纳米管-聚丙烯腈(CNT-PAN)复合纳米纤维膜,以期利用CNT增强PAN纳米纤维的力学性能和染料吸附性能。通过扫描电子显微镜、物理吸附仪和电子万能试验机等对不同CNT含量的复合纤维膜的微观结构、孔隙率、比表面积以及力学性能进行了表征分析。以亚甲基蓝为模板分子研究了不同条件下纳米纤维膜对染料的吸附效果。结果表明,随着CNT含量的增加,纳米纤维的直径略微增大,膜孔隙率和孔径变化不大。CNT的加入明显提高了PAN的力学性能和对染料的吸附性能,CNT的质量分数为10%时CNT-PAN复合纳米纤维膜的性能最佳,与纯PAN纤维膜相比,断裂强度提高了152%,染料吸附率提高了将近30%。     

Synthesis and Characterization of Biocompatible Poly(ethylene glycol)-b-Poly(L-lactide) and Study on Their Electrospun Scaffolds

A series of multiblock copolymer, Poly(L-lactide)-b-Poly(ethylene glycol) (PLLA-b-PEG) were synthesized and characterized by Fourier transform infrared spectra, differential scanning calorimetry and wide angle X-ray diffraction. PLLA-b-PEG fibrous scaffolds were prepared by electrospinning. The morphology of the fibers was affected by the solution concentration and different weight ratio of PLLA/PEG. In comparison with the electrospun PLLA membrane, the electrospun fibrous membranes of PLLA-b-PEG demonstrated an enhanced water absorption percentage and reductive water contact angle. The electrospun PLLA-b-PEG with weight ratio 90/10 and 75/25 fibrous membranes exhibited good flexibility and deformability to be beneficial for tissue engineering scaffolds.     

Influence of hydroxyapatite and BMP‐2 on bioactivity and bone tissue formation ability of electrospun PLLA nanofibers

An excellent bioactive scaffold material which could induce and promote new bone formation is essential in the bone repair field. In this study, the bioactive material hydroxyapatite (HA) and the bone morphogenetic protein‐2 (BMP‐2) were added to poly‐l‐lactic acid (PLLA) using the electrospinning method. Scanning electron microscopy investigations performed on four different fiber scaffolds, PLLA, PLLA/HA, PLLA/BMP‐2 and PLLA/HA/BMP‐2, revealed that the fibers of all scaffolds are closely interwoven, and the presence of large interconnected voids between the fibers, resulting in a three‐dimensional porous network structure that was similar to the structure of the extracellular matrix of healthy bones. In the MG63 cell culture growth experiments, the composite scaffold material PLLA/HA/BMP‐2 showed a higher bioactivity than the other three scaffold materials. The four scaffold materials were implanted in rabbits’ tibia for 30 and 90 days. The results of the animal experiments indicate that the capability of the PLLA/HA/BMP‐2 composite to induce and promote bone tissue formation was better compared with PLLA/HA or PLLA/BMP‐2, suggesting that PLLA combined with HA/BMP‐2 is a promising material for bone tissue repair. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42249.     

Fabrication of macroporous chitosan/poly(l-lactide) hybrid scaffolds by sodium acetate particulate-leaching method

For tissue engineering applications, 3-D macroporous chitosan/poly(l-lactide) (PLLA) scaffolds were prepared by the particulate-leaching method using sodium acetate as the porogen in an acidic water/dioxane solution. The stability and dispersity of chitosan on the chitosan/PLLA hybrid scaffolds were determined by measuring water contact angles, establishing crystallinity using X-ray diffraction, and using eosin staining to observe the chitosan under a light microscope. The porous structure of the particulate-leached chitosan/PLLA scaffolds was investigated in terms of pore morphology, interconnectivity, etc. by using scanning electron microscopy. Chitosan/PLLA scaffolds produced by particulate-leaching showed a highly porous structure and improved stability and dispersity of chitosan as compared to pure PLLA and chitosan-coated PLLA scaffolds. The highly porous structure that resulted from a high concentration of chitosan improved the efficiency of cell adhesion after culturing cells for 4?h. After 48?h, the cultured cells showed increased cell proliferation on the hybrid scaffolds. Thus, particulate-leached chitosan/PLLA scaffolds can be applied to tissue engineering of various types, including the industrial membrane field.     

Poly(l-lactic acid) short fibers prepared by solvent evaporation using sodium tripolyphosphate

A porous material consisting of biodegradable polymer fibers may be one of the best candidates for implants used in the regeneration of damaged tissue, because it has a continuous pore structure that would allow ingrowth of nutriments, tissues, blood vessels or cells. In the present work, short fibers of biodegradable poly(l-lactic acid) (PLLA) were successfully prepared by the dropwise addition of PLLA dissolved in methylene chloride to a poly(vinyl alcohol) (PVA) solution containing sodium tripolyphosphate with stirring. It was suggested that droplets of the PLLA solution form spheres coated with PVA, which are then deformed into fibrous shapes due to stirring. The length of fibers was 200-800 μm and was controlled by the stirring rate, the PLLA concentration of the droplets and the PVA concentration. A PLLA porous block could be easily prepared by sintering the PLLA fibers at 173 °C for 10 min. The material had a continuous pore structure with the average pore size of approximately 40 μm and porosity of about 80%.     

In vitro degradation of PLLA/nHA composite scaffolds

Porous Poly‐l ‐lactide (PLLA) scaffolds and PLLA/nanohydroxyapatite (nHA) composite scaffolds with interconnected pore networks and a porosity of over 90% were fabricated with lyophilization techniques. In this study, the degradation behavior of PLLA and PLLA/nHA composite scaffolds is investigated over 8 weeks in phosphate buffer solution at 37°C. Thermal analysis using differential scanning calorimetry (DSC) showed that the percent crystallinity of all the samples increased by approximately 10%, which represents a considerable increase in the glass transition temperature. The melting range enthalpy of the scaffolds did not change to lower temperatures as would be expected. The spectroscopic analysis performed by Fourier transform infrared spectroscopy suggested that nHA particles should not appreciably affect the absorbance pattern when evenly mixed with the PLLA. This is consistent with the analysis of the scaffold microstructure and morphology with scanning electron microscopy, which drew a low content of nHA with no significant effect on solvent crystallization or pore structure. The compressive modulus and the yield strength of the scaffolds were investigated in conjunction with the study of their degradation rates. In comparison with the mechanical properties of the PLLA scaffolds, which remained largely unchanged, those of the PLLA/nHA composite scaffolds decreased as the degradation progressed. POLYM. ENG. SCI., 54:2571–2578, 2014. © 2013 Society of Plastics Engineers     

In vitro degradation and biocompatibility of poly(l-lactic acid)/chitosan fiber composites

In this study, poly(l-lactic acid) (PLLA) fibers were prepared by the dry-wet-spinning method, while chitosan (CHS) fibers were prepared via the wet-spinning method. The two fibers were blend spun and then fabricated into PLLA/CHS fabrics. In vitro degradation experiments of the fabrics were carried out in a phosphate-buffered solution at 37 °C with a pH of 7.4. Changes in molecular parameters (molecular weights and molecular weight distributions), phase structures (crystallinities), morphologies (fiber surface topologies) of the PLLA fibers, and their macroscopic properties (the fabric weight losses and mechanical strengths) were monitored with degradation times. These results were compared with control samples with no degradation. The hydrolysis mechanism of PLLA/CHS fabrics was analyzed. It was found that the degradation rate of dry-wet-spun PLLA fibers was higher than those of the melt-spun or dry-spun ones. Furthermore, the compatibility between PLLA/CHS fabrics and osteoblast under the in vitro degradation was investigated for the potential application of using the PLLA/CHS fabrics as supporting materials for chest walls and bones. Cell strain hFOB1.19 human SV40-transfected osteoblast and PLLA/CHS mixed fabrics were incubated. The cell morphology at early stages of cultivation was also studied. Excellent adhesion between osteoblast and PLLA/CHS fabrics was observed, indicating good biocompatibility of the fabrics with osteoblast.     

Decomposition rate control of PLLA plate by heat treatment

It is difficult to control the decomposition rate and the mechanical property of scaffolds after forming the poly(L ‐lactide) (PLLA) scaffolds. The purpose of this study is to control the decomposition rate and mechanical properties of the PLLA plate after forming. We carried out accelerated decomposition experiments using the enzyme on the (PLLA) with various crystallinity, which were prepared by changing the heat treatment condition, and elucidated the relationship between the crystallinity and the decomposition rate. A high positive correlation was observed between the heat treatment temperature and the crystallinity. A high negative correlation was observed between the crystallinity and the decomposition rate. Using the obtained empirical formula, it became possible to calculate the required period to decompose a certain amount of the PLLA if the heat treatment temperature was known. Changing the crystallinity of the PLLA plate could arbitrarily control the decomposition rate of the PLLA plate after forming. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of new nano-composite scaffolds loaded with vascular stents

In this study, vascular stents were fabricated from poly (lactide-ɛ-caprolactone)/collagen/nano-hydroxyapatite (PLCL/Col/nHA) by electrospinning, and the surface morphology and breaking strength were observed or measured through scanning electron microscopy and tensile tests. The anti-clotting properties of stents were evaluated for anticoagulation surfaces modified by the electrostatic layer-by-layer self-assembly technique. In addition, nano-composite scaffolds of poly (lactic-co-glycolic acid)/polycaprolactone/nano-hydroxyapatite (PLGA/PCL/nHA) loaded with the vascular stents were prepared by thermoforming-particle leaching and their basic performance and osteogenesis were tested in vitro and in vivo. The results show that the PLCL/Col/nHA stents and PLGA/PCL/nHA nano-composite scaffolds had good surface structures, mechanical properties, biocompatibility and could guide bone regeneration. These may provide a new way to build vascularized-tissue engineered bone to repair large bone defects in bone tissue engineering.     

Preparation and characterization of poly(L‐lactide)/ poly(ϵ‐caprolactone) fibrous scaffolds for cartilage tissue engineering

Polyblend fibrous scaffolds in mass ratios of 100/0, 90/10, 80/20, and 70/30 from poly(L ‐lactide) (PLLA) and poly(?‐caprolactone) (PCL) for cartilage tissue engineering were prepared in three steps: gelation, solvent exchanging, and freeze‐drying. Effects of the blend ratio, the exchange medium, and the operating temperature on the morphology of scaffolds were investigated by SEM. PLLA/PCL scaffolds presented an ultrafine fibrous network with the addition of a “small block” structure. Smooth and regular fibrous networks were formed when ethanol was used as the exchange medium. Properties of the scaffolds, such as thermal and mechanical properties, were also studied. The results suggested that the compressive modulus declined as PCL amount increased. The incorporation of PCL effectively contributed to reduce the rigidity of PLLA. Bovine chondrocytes were seeded onto PLLA/PCL scaffold. Cells attached onto the fibrous network and their morphology was satisfactory. This polyblend fibrous scaffold will be a potential scaffold for cartilage tissue engineering. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1676–1684, 2004     

Process study,development and degradation behavior of different size scale electrospun poly(caprolactone) and poly(lactic acid) fibers

This study describes the preparation of electrospun poly(caprolactone) (PCL) and poly(lactic acid) (PLA) fibrous scaffolds with and without nano-hydroxyapatite (nHAp) having nanoscale, microscale and combined micro/nano (multiscale) architecture. Processing parameters such as polymer concentration, voltage, flow rate and solvent compositions were varied in wide range to display the effect of each one in determining the diameter and morphology of fibers. The effect of each regulating parameter on fiber morphology and diameter was evaluated and characterized using scanning electron microscope (SEM). Degradability of the selected fibrous scaffolds was verified by phosphate buffered saline immersion and its morphology was analyzed through SEM, after 5 and 12 months. Quantitative measurement in degradation was further evaluated through pH analysis of the medium. Both studies revealed that PLA had faster degradation compared to PCL irrespective of the size scale nature of fibers. Structural stability evaluation of the degraded fibers in comparison with pristine fibers by thermogravimetric analysis further confirmed faster degradability of PLA compared to PCL fibers. The results indicate that PLA showed faster degradation than PCL irrespective of the size-scale nature of fibrous scaffolds, and therefore, could be applied in a variety of biomedical applications including tissue engineering.