Polydopamine-modified poly(l-lactic acid) nanofiber scaffolds immobilized with an osteogenic growth peptide for bone tissue regeneration

It is highly desirable for bone tissue engineering scaffolds to have significant osteogenic properties and capability to improve cell growth and thus enhance bone regeneration. In this study, a poly(l-lactic acid) (PLLA) nanofiber scaffold-immobilized osteogenic growth peptide (OGP) was prepared via polydopamine (PDA) coating. X-ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electron microscopy (SEM) were used to determine the OGP immobilization, hydrophilicity and surface roughness of the samples. The SEM and fluorescence images demonstrate that the PLLA nanofiber scaffolds immobilized with the OGP have excellent cytocompatibility in terms of cell adhesion and proliferation. The ALP activity and the Runx2 and OPN expression results indicated that the PLLA nanofiber scaffolds immobilized with OGP significantly enhanced the osteogenic differentiation and calcium mineralization of hMSCs in vitro. A rat model of critical skull bone defect was selected to evaluate the bone formation capacity of the scaffolds. Micro CT analysis and histological results demonstrated that the PLLA scaffolds immobilized with OGP significantly promoted bone regeneration in critical-sized bone defects. This study verifies that the PLLA scaffold-immobilized OGP has significant potential in bone tissue engineering.

Polydopamine-modified PLLA nanofiber scaffolds immobilized with osteogenic growth peptide were designed and prepared for promoting bone formation.     

Fabrication and characterization of poly(lactic-co-glycolic acid) microsphere/amorphous calcium phosphate scaffolds

Although hydroxyapatite (HAP) and β-tricalcium phosphate have been used extensively as osteoconductive minerals in biomaterial scaffolds for bone regeneration, they lack the capacity to stimulate osteoblastic differentiation of progenitor cells. In contrast, amorphous calcium phosphates (ACPs), which convert to HAP under aqueous conditions, have the potential to facilitate osteoblastic differentiation through the transient local release of calcium and phosphate ions. Therefore, in this study ACPs were synthesized using zinc and zirconia divalent cations as stabilizers (denoted ZnACP and ZrACP, respectively) and compared to HAP. Analysis of ion release into serum-containing cell culture medium revealed transiently elevated levels of calcium and phosphorous, consistent with the enhanced solubility of ZrACP and ZnACP relative to HAP. In addition, X-ray diffraction analysis revealed partial conversion of ZrACP to HAP but no conversion of ZnACP after 96 h. Next, scaffolds were fabricated by sintering mixtures of 300-500 μm poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres and 0.5 wt% calcium phosphate mineral (HAP, ZrACP or ZnACP) at 70 °C for 24 h. Scanning electron microscopy revealed a porous microsphere matrix with calcium phosphate particulates clinging to the microsphere surfaces both prior to and after 14 days in culture medium. Finally, the incorporation of calcium phosphate resulted in a lower compressive modulus in the range 127 to 74-89 MPa. Taken together, these results indicate that ZrACP, ZnACP and HAP minerals exhibit very different properties, and therefore may elicit different osteoblastic responses in vitro.     

聚乳酸-乙醇酸膜在模拟体液中降解的Monte Carlo 模拟

背景:聚乳酸-乙醇酸广泛应于医用植入物与药物缓释载体,由于影响其降解过程的因素较多,使得其失重性能难以模拟.目的:对聚乳酸-乙醇酸膜失重性能进行数值模拟,观察模拟与实际测量的相关性.设计:重复测量.单位:大连理工大学材料科学与工程学院.材料:重均分子量分别为63 000, 115 000和400 000的实验用的聚乳酸-乙醇酸 50/50,70/30 和75/25,购自山东省医用高分子材料重点实验室.1,4-二氧六环为天津化学试剂一厂生产,用作溶剂.方法:实验于2006-04/06在大连理工大学材料科学与工程学院完成.①将聚乳酸-乙醇酸分别按质量比50∶50,70∶30及75∶25溶于1,4-二氧六环,溶液浇铸成10 mm×10 mm×1 mm的聚合物膜.②聚乳酸-乙醇酸膜在37 ℃的Hank's模拟体液(pH 7.4)中浸泡,每周取出1次(质量比为50:50的聚乳酸-乙醇酸为每5天取1次),试样清洗并干燥之后使用凝胶渗透色谱仪测量其数均与重均分子量,计算降解速率.同时使用电子天平测量其失重性能,并与Monte Carlo法改进后实际测量值进行相关性分析.主要观察指标:①不同质量比聚乳酸-乙醇酸的降解速率.②模拟结果与实验值之间的相关系数.结果:①质量比50:50,70:30和75:25的聚乳酸-乙醇酸降解速率分别为0.058 5,0.016 6和0.010 1/d(数均分子量)或者0.061 0,0.017 5和0.008 5/d(重均分子量).②聚乳酸-乙醇酸 50/50,70/30和75/25的模拟结果与实验值之间的相关系数分别为0.973 6,0.987 4 和0.990 3.结论:数值模拟聚乳酸-乙醇酸膜失重性能与实验值符合良好.     

In vitro evaluation of osteoblastic differentiation on amorphous calcium phosphate-decorated poly(lactic-co-glycolic acid) scaffolds

Calcium phosphate-decorated polyester matrices are promising scaffolds for bone tissue engineering that combine the tunable degradation of synthetic polymers and the osteoconductivity of calcium phosphate minerals. In this study, scaffolds decorated with stabilized amorphous calcium phosphate (ACP) minerals-which exhibit sustained dissolution and release of calcium and phosphate ions-were tested for their ability to support osteoblast proliferation and stimulate differentiation. The two ACPs tested were zirconia-hybridized ACP (ZrACP), which releases ions over a few days and converts in aqueous solution to hydroxyapatite (HAP), and zinc-hybridized ACP (ZnACP), which has a longer period of sustained ion release. MC3T3-E1 pre-osteoblasts were cultured in these scaffolds for up to 21 days, and cell number, alkaline phosphatase (ALP) activity and expression of osteogenic and bone-specific proteins were measured. Cell number, prostaglandin E(2) (PGE(2) ) synthesis and osteopontin (OPN) mRNA expression were elevated on calcium phosphate-decorated scaffolds relative to PLGA controls, while mRNA expression of osteocalcin (OCN), bone sialoprotein and bone morphogenetic protein (BMP)-4 were suppressed. Although MC3T3-E1 responses to the two ACPs were not statistically different, ZrACP-which converts more quickly to HAP-gave rise to slightly higher levels of mRNA expression for BMP-4, osterix, vascular endothelial growth factor (VEGF)-A, OCN and OPN, but slightly lower levels of PGE(2) synthesis, ALP activity and cell number. These results indicate that sintered PLGA microsphere scaffolds decorated with 0.5 wt% ZnACP or ZrACP support cell attachment and elicit a series of biological responses, but these responses do not appear to accelerate osteoblast differentiation.     

纳米碳酸钙/聚左旋乳酸复合材料的制备与性能

目的:生物降解材料(聚左旋乳酸)存在初始强度低和降解速率快等局限性,利用纳米技术有望解决生物降解材料的力学性能缺陷.制备纳米碳酸钙/聚左旋乳酸复合材料并评价其力学性能.方法:实验于2002-09/2004-01在吉林大学化学学院实验室完成.采用溶液共混法制备纳米碳酸钙,聚左旋乳酸复合材料.将聚左旋乳酸、10%和30%的纳米碳酸钙,聚左旋乳酸复合材料加工成60 mm×6 mm×2 mm的条形试样,在Instron-1121型材料试验机上测试弯曲强度和拉伸弹性模量,加载速度为1 mm/min:用XCJ-4简支梁式试验冲击仪测试无缺口冲击强度.结果:力学测试显示10%,30%纳米碳酸钙,聚左旋乳酸复合材料的冲击强度、弯曲强度、拉伸弹性模量均高于聚左旋乳酸材料,差异有显著性意义(P＜0.05).30%纳米碳酸钙/聚左旋乳酸复合材料的冲击强度、弯曲强度、拉伸弹性模量均高于10%纳米碳酸钙,聚左旋乳酸复合材料,差异有显著性意义(P＜0.05).结论:纳米碳酸钙与聚左旋乳酸复合后力学性能有所提高.30%纳米碳酸钙,聚左旋乳酸复合材料力学性能最佳.     

混杂结构聚乳酸/钙磷盐/胶原骨支架的表面处理研究

目的将聚乳酸/钙磷盐/胶原复合材料作为制造骨组织工程支架的材料.方法采用碱式反应法和共混法获得两种胶原/钙磷盐复合材料,然后通过真空吸附法在聚乳酸/磷酸三钙的支架表面沉积胶原,又通过碱式反应法沉积钙磷盐.结果观测碱式反应法合成胶原-钙磷盐复合材料胶原交联纤维束间形成薄膜状粘连.共混法获得胶原-钙磷盐复合材料显示钙磷盐和胶原海绵紧密结合.快速成形工艺获得混杂结构支架可见最后用碱式反应法合成的片状钙磷盐颗粒沉积在胶原海绵的表面.结论此法获得了具有混杂结构的支架,可以应用于骨的修复.     

纳米羟基磷灰石/聚磷酸钙纤维/聚乳酸骨组织工程复合支架的特性

背景:近年来国内外在骨与软骨组织支架复合材料方面进行了广泛的研究,取得了积极的成果,但仍存在许多问题.目的:观察纳米羟基磷灰石/聚磷酸钙纤维/聚乳酸(HAP/CPP/PLLA)骨组织工程支架复合材料的特性.方法:采用溶媒浇铸、粒子滤取技术与气体发泡相结合的方法制备出纳米HAP/CPP/PLLA 骨组织工程支架复合材料,测试该支架复合材料的物理力学性能,并用扫描电子显微镜对其微观结构进行观察.结果与结论:结果表明,纳米HAP/CPP/PLLA 支架复合材料具有三维、连通、微孔网状结构,并具有较高的孔隙率和较好的压缩模量,是理想的骨组织工程支架材料.     

Fabrication of strontium/calcium containing poly(γ-glutamic acid) – organosiloxane fibrous hybrid materials for osteoporotic bone regeneration

Recent researches have proved that combination of several therapeutic metal ions, such as silicate (Si), calcium (Ca), strontium (Sr) and so on, with biomaterials may have promising effects for stimulating bone regeneration. In the present study, the Sr/Ca containing silicate hybrid materials (Sr/Ca-γ-PGA-silica) with a mimetic native extracellular matrix (ECM) structure have been developed by electrospinning. With the aim to promote the solubility of γ-PGA in aqueous-based solution and introduce Sr/Ca elements into the prepared hybrid materials, SrCO₃ and CaCO₃ were employed due to their nontoxicity and no by-products during chemical reaction between γ-PGA and SrCO₃/CaCO₃. Results of SEM, EDX and elemental mapping images showed that Sr and Ca have been successfully incorporated into the prepared fibrous hybrid materials with homogeneous dispersion. Results of ICP-AES revealed that there was continuous Si, Sr and Ca ion release behavior of Sr/Ca-γ-PGA-silica hybrid materials in Tris–HCl buffer solution and the Si ions release rate can be tailored by adjusting the molar ratio of Sr to Ca. Immersion of Sr/Ca-γ-PGA-silica hybrid materials in a simulated body fluid (SBF) resulted in the formation of an apatite-like surface layer within 3 days, indicating their excellent bioactivity. In addition, the prepared Sr/Ca-γ-PGA-silica hybrid materials supported the proliferation and alkaline phosphatase (ALP) activity of osteoblast in vitro, showing their good biocompatibility. Altogether, the results indicated that the prepared Sr/Ca-γ-PGA-silica hybrid materials with an adjusted ionic release behavior have great potential for providing an excellent ECM for osteoporotic bone regeneration.

Recent researches have proved that combination of several therapeutic metal ions, such as silicate (Si), calcium (Ca), strontium (Sr) and so on, with biomaterials may have promising effects for stimulating bone regeneration.     

Enzymatic,urease‐mediated mineralization of gellan gum hydrogel with calcium carbonate,magnesium‐enriched calcium carbonate and magnesium carbonate for bone regeneration applications

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO₃) has been successfully applied as a bone regeneration material, but hydrogel‐CaCO₃ composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone‐forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate‐based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO₃, Mg‐enriched CaCO₃ and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg₅(CO₃)₄(OH)₂.4H₂O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium:magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast‐like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO₃ in the form of calcite successfully reinforced hydrogels and promoted osteoblast‐like cell adhesion and growth, but magnesium enrichment had no definitive positive effect. Copyright © 2017 John Wiley & Sons, Ltd.     

Pressure‐activated microsyringe (PAM) fabrication of bioactive glass–poly(lactic‐co‐glycolic acid) composite scaffolds for bone tissue regeneration

The aim of this work was the fabrication and characterization of bioactive glass–poly(lactic‐co‐glycolic acid) (PLGA) composite scaffolds mimicking the topological features of cancellous bone. Porous multilayer PLGA–CEL2 composite scaffolds were innovatively produced by a pressure‐activated microsyringe (PAM) method, a CAD/CAM processing technique originally developed at the University of Pisa. In order to select the optimal formulations to be extruded by PAM, CEL2–PLGA composite films (CEL2 is an experimental bioactive SiO₂–P₂O₅–CaO–MgO–Na₂O–K₂O glass developed at Politecnico di Torino) were produced and mechanically tested. The elastic modulus of the films increased from 30 to > 400 MPa, increasing the CEL2 amount (10–50 wt%) in the composite. The mixture containing 20 wt% CEL2 was used to fabricate 2D and 3D bone‐like scaffolds composed by layers with different topologies (square, hexagonal and octagonal pores). It was observed that the increase of complexity of 2D topological structures led to an increment of the elastic modulus from 3 to 9 MPa in the composite porous monolayer. The elastic modulus of 3D multilayer scaffolds was intermediate (about 6.5 MPa) between the values of the monolayers with square and octagonal pores (corresponding to the lowest and highest complexity, respectively). MG63 osteoblast‐like cells and periosteal‐derived precursor cells (PDPCs) were used to assess the biocompatibility of the 3D bone‐like scaffolds. A significant increase in cell proliferation between 48 h and 7 days of culture was observed for both cell phenotypes. Moreover, qRT–PCR analysis evidenced an induction of early genes of osteogenesis in PDPCs. Copyright © 2015 John Wiley & Sons, Ltd.     

In vitro cellular testing of strontium/calcium substituted phosphate glass discs and microspheres shows potential for bone regeneration

Phosphate‐based glasses (PBGs) are ideal materials for regenerative medicine strategies because their composition, degradation rates, and ion release profiles can easily be controlled. Strontium has previously been found to simultaneously affect bone resorption and deposition. Therefore, by combining the inherent properties of resorbable PBG and therapeutic activity of strontium, these glasses could be used as a delivery device of therapeutic factors for the treatment of orthopaedic diseases such as osteoporosis. This study shows the cytocompatibility and osteogenic potential of PBGs where CaO is gradually replaced by SrO in the near invert glass system 40P₂O₅·(16‐x)CaO·20Na₂O·24MgO·xSrO (x = 0, 4, 8, 12, and 16 mol%). Direct seeding of MG63 cells onto glass discs showed no significant difference in cell metabolic activity and DNA amount measurement across the different formulations studied. Cell attachment and spreading was confirmed via scanning electron microscopy (SEM) imaging at Days 3 and 14. Alkaline phosphatase (ALP) activity was similarly maintained across the glass compositions. Follow‐on studies explored the effect of each glass composition in microsphere conformation (size: 63‐125 μm) on human mesenchymal stem cells (hMSCs) in 3D cultures, and analysis of cell metabolic activity and ALP activity showed no significant differences at Day 14 over the compositional range investigated, in line with the observations from MG63 cell culture studies. Environmental SEM and live cell imaging at Day 14 of hMSCs seeded on the microspheres showed cell attachment and colonisation of the microsphere surfaces, confirming these formulations as promising candidates for regenerative medicine strategies addressing compromised musculoskeletal/orthopaedic diseases.     

Stability of insulin during the erosion of poly(lactic acid) and poly(lactic-co-glycolic acid) microspheres.

In recent years, the acylation of peptides during the erosion of poly(lactic acid) and poly(lactic-co-glycolic acid) microspheres has been described in the literature. To investigate whether insulin is prone to the covalent attachment of lactic or glycolic acid, insulin-loaded PLA and PLGA microspheres containing 5% bovine insulin were manufactured using a w/o/w multiple emulsion-solvent evaporation technique. Microspheres were characterized for their insulin encapsulation efficiency and release characteristics in phosphate-buffered saline (PBS) at pH 7.4 and 37 degrees C. Moreover, the stability of the peptide during 18 days of release was evaluated using HPLC and HPLC-MS techniques. The results showed that the insulin loading efficiencies of PLA and PLGA microspheres were 75.18% and 79.63%, respectively. The microspheres were spherical with relatively porous surfaces with an average diameter of 40 and 53 mum, respectively. Insulin release from the microspheres was characterized by an initial burst, which was attributed to the amount of protein located on or close to the microsphere surface. The total ion chromatogram (TIC) of insulin samples extracted after 18 days of erosion in phosphate buffer pH 7.4 at 37 degrees C revealed that deamidation was the major mechanism of instability. Surprisingly, no acylation products were found. Control experiments in concentrated lactic acid solutions confirmed a minimal reactivity of the peptide under these conditions.     

利福平/聚乳酸-聚羟基乙酸缓释微球的制备及特性

背景:虽然国内外有很多制备利福平/聚乳酸-聚羟基乙酸共聚物(poly lactic acid-glycolic acid copolymer,PLGA)微球的报道,但这些微球粒径多在10 μm左右,不适合与磷酸钙骨水泥复合制备成具有良好降解性的抗结核修复材料.目的:制备大粒径利福平/PLGA缓释微球,观察其理化特性和体外缓释特性.方法:以PLGA为载体,将利福平分散于PLGA的有机溶剂中,采用复乳溶剂挥发法制备利福平/ PLGA缓释微球.光镜和扫描电镜下观察微球的形态特征,测定微球平均直径和跨距,高效液相色谱法测定载药量和包封率,以溶出法和高效液相色谱法观察其体外释药特性,并拟合药物体外释放曲线建立曲线方程.结果与结论:利福平/PLGA微球电镜观察呈圆球形,分散性好,粘连少,粒径分布集中,平均粒径(80.0±9.4) μm.载药量、包封率分别为(33.18±1.36)%,(54.79±1.13)%.体外缓释试验显示突释期内微球释放度为(14.66±0.18)%,前3 d累计释放度(18.09±0.45)%,到42 d体外累积释放度达到(92.17±1.23)%.提示利福平/PLGA微球具有良好的缓释效果,是一种较为理想的抗结核药物的载体材料和释放系统;PLGA是良好的药物缓释载体,可以用来制备载药缓释微球.     

Biodegradable poly(ethylenimine) for plasmid DNA delivery

Poly(ethylenimine) (PEI) has been known as an efficient gene carrier with the highest cationic charge potential. High transfection efficiency of PEI, along with its cytotoxicity, strongly depends on the molecular weight. Synthesis of cationic copolymers derived from the low molecular weight of PEI and hydrophilic poly(ethylene glycol) (PEG), which are water soluble and degradable under physiological conditions, was investigated for plasmid delivery. Hydrophilic PEG is expected to reduce the toxicity of the copolymer, improve the poor solubility of the PEI and DNA complexes, and help to introduce degradable bonds by reaction with the primary amines in the PEI. Considering the dependence of transfection efficiency and cytotoxicity on the molecular weight of the PEI, high transfection efficiency is expected from an increased molecular weight of the copolymer and low cytotoxicity from the introduction of PEG and the degradation of the copolymer into low molecular weight PEIs. Reaction conditions were carefully controlled to produce water soluble copolymers. Results from a gel retardation assay and zetapotentiometer indicated that complete neutralization of the complexes was achieved at the charge ratios of copolymer/pSV-β-gal plasmid from 0.8 to 1.0 with the mean particle size of the polyplexes ranging from 129.8±0.9 to 151.8±3.4 nm. In vitro transfection efficiency of the synthesized copolymer increased up to three times higher than that of starting low molecular weight PEI, while the cell viability was maintained over 80%.     

构建球磨碳酸钙/聚磷酸钙纤维/聚乳酸组织工程支架复合材料

背景:近年来国内外在骨与软骨组织支架材料方面取得了积极的成果,但仍存在炎症反应高、生物相容性低等许多问题,因此复合材料技术是解决目前存在问题的重要途径之一.目的:制备球磨碳酸钙/聚磷酸钙纤维/聚乳酸组织工程支架复合材料.方法:采用溶媒浇铸、粒子滤取技术与气体发泡相结合的方法制各出球磨碳酸钙/聚磷酸钙纤维,聚乳酸组织工程支架复合材料.测试该支架复合材料的物理、力学及降解性能,并用扫描电子显微镜对其微观结构进行观察.结果与结论:制备出孔隙率在60%-80%之间的球磨碳酸钙,聚磷酸钙纤维,聚乳酸组织工程支架复合材料,具有三维、连通、微孔网状结构,其密度的实验值和计算值基本相吻和;压缩模量值均在3 MPa以上,能够满足软骨组织工程支架复合材料对压缩模量的要求.随着降解时间的延长,支架复合材料的降解速率在增大;球磨碳酸钙,聚磷酸钙纤维,聚乳酸组织工程支架复合材料的降解液的pH值基本保持在6-7.5之间,球磨碳酸钙粉末的加入稳定了降解液的pH值.该支架复合材料降解一定时期后仍为三维、连通、微孔网状结构.     

聚碳酸亚丙酯/壳聚糖纳米纤维三维多孔支架复合骨髓间充质干细胞修复兔骨缺损

背景:骨组织工程细胞移植技术是近年来的研究热点,支架材料是其重要组成部分,同时也是三大要素中最有望取得突破性进展的环节,随着组织工程材料工艺的革新,有望为更好地修复骨缺损带来新的希望。目的:评价聚碳酸亚丙酯/壳聚糖纳米纤维(propylene carbonate/chitosan nanofibers,PPC/CSNF)三维多孔支架复合骨髓间充质干细胞(bone marrow mesenchymal stem cell,BMSCs)修复兔股骨髁部骨缺损的能力。方法:二次相分离法制作PPC/CSNF复合三维多孔支架,将第3代的BMSCs种植到复合材料上。36只新西兰大白兔右侧股骨髁制作直径6mm深10mm骨缺损,于缺损处实验组植入复合BMSCs的PPC/CSNF多孔支架,对照组植入单纯PPC/CSNF多孔支架,标准组于兔髂后上棘取自体松质骨移植于缺损部位,空白组不做处理。术后第4,8,12周取材,通过大体观察、放射学检查和组织学检查等方法评价其修复缺损情况。结果与结论:实验组放射学评价与标准组无显著差异,两组结果均优于对照组(P<0.05);实验组大体标本与标准组基本一致;实验组组织学检查新骨生成速度、生成量优于对照组(P<0.05);空白组不能自行修复骨缺损,最后缺损由纤维组织充填。结果显示PPC/CSNF多孔支架具有较好的细胞和组织相容性,复合兔BMSCs能加速新骨形成,可用于修复兔股骨髁部骨缺损。     

聚碳酸亚丙酯/壳聚糖纳米纤维三维多孔支架复合骨髓间充质干细胞修复兔骨缺损

背景：骨组织工程细胞移植技术是近年来的研究热点,支架材料是其重要组成部分,同时也是三大要素中最有望取得突破性进展的环节,随着组织工程材料工艺的革新,有望为更好地修复骨缺损带来新的希望。目的：评价聚碳酸亚丙酯/壳聚糖纳米纤维（propylene carbonate/chitosan nanofibers,PPC/CSNF）三维多孔支架复合骨髓间充质干细胞（bone marrow mesenchymal stem cell,BMSCs）修复兔股骨髁部骨缺损的能力。方法：二次相分离法制作PPC/CSNF复合三维多孔支架,将第3代的BMSCs种植到复合材料上。36只新西兰大白兔右侧股骨髁制作直径6mm深10mm骨缺损,于缺损处实验组植入复合BMSCs的PPC/CSNF多孔支架,对照组植入单纯PPC/CSNF多孔支架,标准组于兔髂后上棘取自体松质骨移植于缺损部位,空白组不做处理。术后第4,8,12周取材,通过大体观察、放射学检查和组织学检查等方法评价其修复缺损情况。结果与结论：实验组放射学评价与标准组无显著差异,两组结果均优于对照组（P〈0.05）;实验组大体标本与标准组基本一致;实验组组织学检查新骨生成速度、生成量优于对照组（P〈0.05）;空白组不能自行修复骨缺损,最后缺损由纤维组织充填。结果显示PPC/CSNF多孔支架具有较好的细胞和组织相容性,复合兔BMSCs能加速新骨形成,可用于修复兔股骨髁部骨缺损。     

聚磷酸钙/左旋聚乳酸软骨组织工程支架复合材料的分析

背景用左旋聚乳酸(PLLA),聚羟基乙酸(PGA)等可降解吸收性高分子材料加工而成的纤维状支架材料和海绵状支架材料在软骨组织工程中已获得广泛应用.但这类支架材料存在着弹性模量低,受力时易变形,容易导致种子细胞损伤和降解吸收时间过长等缺陷.目的研制出可任意调控降解速率且具有良好力学性能、生物相溶性能和毒理学性能的聚磷酸钙(Calcium Polyphosphate,CPP)纤维,并用该纤维为增强材料研制软骨组织工程复合材料.设计以不同质量比例分组对照的实验研究.地点和对象实验在兰州交通大学材料工程研究所完成,基体材料选用PLLA(中科院化学所高分子合成室提供),增强材料选用自制CPP纤维.干预以高强度、高模量可设计降解速率的CPP纤维为增强材料,PLLA为基体材料,应用溶媒投放、颗粒滤取技术制备出CPP/PLLA软骨组织工程支架复合材料,测试了该支架复合材料的物理力学性能和体外37℃下Hank's人工降解液中的生物降解特性.主要观察指标物理力学性能,降解性能.结果CPP/PLLA支架复合材料具有三维连通、微孔、网状微观结构,微孔分布均匀,微孔尺寸为130～350μm,孔隙率90%;压缩模量随CPP纤维体积分数的增加而增加;降解速率随CPP纤维体积分数的增大而增大.结论CPP/PLLA支架复合材料的物理力学性能和体外降解性能在体外构建的组织化软骨的早期生物学性能基本满足软骨组织工程的要求,故可用作软骨组织工程支架材料.     

The development of non-viral gene-activated matrices for bone regeneration using polyethyleneimine (PEI) and collagen-based scaffolds

The healing potential of scaffolds for tissue engineering can be enhanced by combining them with genes to produce gene-activated matrices (GAMs) for tissue regeneration. We examined the potential of using polyethyleneimine (PEI) as a vector for transfection of mesenchymal stem cells (MSCs) in monolayer culture and in 3D collagen-based GAMs. PEI-pDNA polyplexes were fabricated at a range of N/P ratios and their optimal transfection parameters (N/P 7 ratio, 2μg dose) and transfection efficiencies (30±8%) determined in monolayer culture. The polyplexes were then loaded onto collagen, collagen-glycosaminoglycan and collagen-nanohydroxyapatite scaffolds where gene expression was observed up to 21 days with a polyplex dose as low as 2μg. Transient expression profiles indicated that the GAMs act as a polyplex depot system whereby infiltrating cells become transfected over time as they migrate throughout the scaffold. The collagen-nHa GAM exhibited the most prolonged and elevated levels of transgene expression. This research has thus demonstrated that PEI is a highly efficient pDNA transfection agent for both MSC monolayer cultures and in the 3D GAM environment. By combining therapeutic gene therapy with highly engineered scaffolds, it is proposed that these GAMs might have immense capability to promote tissue regeneration.     

改性纳米羟基磷灰石/聚乳酸-聚羟乙酸复合骨髓基质干细胞修复兔桡骨缺损

背景:前期试验证实骨髓基质干细胞能够在改性纳米羟基磷灰石/聚乳酸-聚羟乙酸材料表面黏附、增殖,该材料具有良好的生物安全性。目的:观察骨髓基质干细胞与改性纳米羟基磷灰石/聚乳酸-聚羟乙酸材料复合修复兔桡骨缺损的效果。方法:建立兔15mm桡骨缺损模型,随机分为3组:空白对照组不进行任何处理,实验组植入改性纳米羟基磷灰石/聚乳酸-聚羟乙酸+骨髓基质干细胞组织工程化骨,对照组植入单纯改性纳米羟基磷灰石/聚乳酸-聚羟乙酸支架材料。结果与结论:①X射线评价:术后1～12周,实验组骨缺损修复程度及速度明显优于空白对照组与对照组(P<0.05)。②组织学检测:实验组术后4周即可观察到新生骨和纤维组织长入材料空隙,局部形成陷窝结构;8周时新生骨组织增多,部分可观察到成熟的骨小梁结构;12周时可见大量成熟骨细胞,骨小梁排列紧密,移植材料逐步被新生骨取代,与正常骨组织形态基本一致,且骨小梁出现时间早于空白对照组与对照组。说明骨髓基质干细胞复合改性纳米羟基磷灰石/聚乳酸-聚羟乙酸构建的组织工程化骨能够促进骨缺损处新骨的生成,较单纯支架材料具有明显优势。