Preparation and characterization of bioactive collagen/wollastonite composite scaffolds

A novel biodegradable collagen/wollastonite composite was prepared as three-dimensional scaffolds by freeze-drying method. Scanning electron microscope (SEM) micrographs of scaffolds showed a continuous structure of interconnected pores, and pore size was about 100 m. The tensile strength of the scaffolds was improved by incorporation of wollastonite and the in vitro bioactivity of the scaffolds was evaluated by examining the hydroxyapatite (HA) deposition on their surface in simulated body fluid (SBF). After soaking in SBF for 7 days, collagen reconstituted to fibers and HA nodules formed on collagen fibers. The result suggests that the incorporation of wollastonite could improve the mechanical strength and the in vitro bioactivity of the composite. The scaffolds could be a potential biomaterial for bone tissue engineering.     

Fabrication and characterization of bioactive silk fibroin/wollastonite composite scaffolds

Composite scaffolds of silk fibroin (SF) with bioactive wollastonite were prepared by freeze-drying. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy analysis showed that random coil and β-sheet structure co-existed in the SF scaffold. The mechanical performance, surface hydrophilicity and water-uptake capacity of the composite scaffolds were improved compared with those of pure SF scaffold. The bioactivity of the composite scaffold was evaluated by soaking in a simulated body fluid (SBF), and formation of a hydroxycarbonate apatite (HCA) layer was determined by FT-IR and XRD. The results showed that the SF/wollastonite composite scaffold was bioactive as it induced the formation of HCA on the surface of the composite scaffold after soaking in SBF for 5 days. In vitro cell attachment and proliferation tests showed that the composite scaffold was a good matrix for the growth of L929 mouse fibroblast cells. Consequently, the incorporation of wollastonite into the SF scaffold can enhance both the mechanical strength and bioactivity of the scaffold, which suggests that the SF/wollastonite composite scaffold may be a potential biomaterial for tissue engineering.     

Preparation and HL-7702 cell functionality of titania/chitosan composite scaffolds

Titania/chitosan composite scaffolds were prepared through a freeze-drying technique. The composite scaffolds were highly porous with the average pore size of 120–300 μm, and the titania (TiO₂) powders were uniformly dispersed on the surface of the pore walls. The compressive strength of the composite scaffolds was significantly improved compared to that of pure chitosan scaffolds. Composite scaffold with 0.3 of TiO₂/chitosan weight ratio showed the maximum compressive strength of 159.7 ± 21 kPa. Hepatic immortal cell line HL-7702 was used as seeding cells on the scaffolds, and after different culture periods, cell attachment and function was analyzed. HL-7702 cells attached on the pore walls of the scaffolds with the spheroid shape after 1 day of culture, but more cell aggregations formed within the TiO₂/chitosan composite scaffolds as compared to pure chitosan scaffolds. Liver-specific functions, albumin secretion and urea synthesis were detected using a spectrometric method. The results showed that albumin secretion and urea synthesis rate of HL-7702 cells slightly decreased with the culture time, and there was no significant difference between composite scaffolds and pure chitosan scaffolds. In conclusion, the TiO₂/chitosan composite scaffolds possessed an improved mechanical strength compared to pure chitosan scaffolds and supported the attachment and functional expression of hepatocyte, implying their potential application in liver tissue engineering.     

Chitosan reinforced apatite–wollastonite coating by electrophoretic deposition on titanium implants

A novel bioactive porous apatite–wollastonite/chitosan composite coating was prepared by electrophoretic deposition. The influence of synthesis parameters like pH of suspension and current density was studied and optimized. X-ray diffraction confirmed crystalline phase of apatite–wollastonite in powder as well as composite coating with coat crystallinity of 65%. Scanning electron microscope showed that the porosity had interconnections with good homogeneity between the phases. The addition of chitosan increased the adhesive strength of the composite coating. Young’s modulus of the coating was found to be 9.23 GPa. One of our key findings was sheet-like apatite growth unlike ball-like growth found in bioceramics. Role of chitosan was studied in apatite growth mechanism in simulated body fluid. In presence of chitosan, dense negatively charged surface with homogenous nucleation was the primary factor for sheet-like evolution of apatite layer. The results suggest that incorporation of chitosan with apatite–wollastonite in composite coating could provide excellent in vitro bioactivity with enhanced mechanical properties.     

Chitosan-Based Nanocomposite Scaffolds for Tissue Engineering Applications

This article reports the fabrication of three-dimensional porous chitosan and hydroxyapatite (HA)/chitosan composite scaffolds by the thermally induced phase separation (TIPS) technique, for bone tissue engineering. Different amounts of HA nanoparticles (10%, 20%, and 30% g/g) were added to the chitosan solution to produce HA/chitosan composite scaffolds of varying compositions. The morphology and pore structure of the scaffolds vis-à-vis composition were characterized using scanning electron microscopy (SEM) and an energy dispersive X-ray (EDX). Both pure chitosan and HA/chitosan composite scaffolds were highly porous and had interconnected pores. The pore sizes ranged from several micrometers to a few hundred micrometers. The HA nanoparticles were well dispersed and physically coexisted with chitosan in the composite scaffolds. However, some agglomeration of HA nanoparticles was observed on the surface of pore walls when a relatively large amount of HA was used. The composite 3D scaffolds are very promising for use in bone tissue engineering application.     

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.     

Preparation,mechanical properties and in vitro degradability of wollastonite/tricalcium phosphate macroporous scaffolds from nanocomposite powders

A new class of scaffolds with a gain size of 200 nm was prepared from wollastonite/tricalcium phosphate (WT) nanocomposite powders (termed “nano-sintered scaffolds”) through a two-step chemical precipitation and porogen burnout techniques. For a comparison, WT scaffolds with a grain size of 2 μm were also fabricated from submicron composite powders (termed “submicron-sintered scaffolds”) under the same condition. The resultant scaffolds showed porosities between 50 ± 1.0% and 65 ± 1.0% with a pore size ranging from 100 μm to 300 μm. The WT nano-sintered scaffolds exhibited compressive strength and elastic modulus values that were about twice that of their submicron-sintered counterparts. The in vitro degradation tests demonstrated that the degradability could be regulated by the grain size of bioceramics. The decreased specific surface area of pores in the nano-sintered scaffolds led to their reduced degradation rate. The mechanical properties of the nano-sintered scaffolds exhibited less strength loss during the degradation process. The WT macroporous nano-sintered scaffolds are a promising and potential candidate for bone reconstruction applications.     

Biodegradable polyurethane composite scaffolds containing Bioglass® for bone tissue engineering

Five types of solid and porous polyurethane composites containing 5–20 wt.% of Bioglass® inclusions were synthesized. Porous structures were fabricated by polymer coagulation combined with the salt-particle leaching method. In-vitro bioactivity tests in simulated body fluid (SBF) were carried out and the marker of bioactivity, e.g. formation of surface hydroxyapatite or calcium phosphate layers upon immersion in SBF, was investigated. The chemical and physical properties of the solid and porous composites before and after immersion in SBF were evaluated using different techniques: Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA). Moreover the surface structure and microstructure of the composites was characterised by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM), respectively. Mercury intrusion porosimetry, SEM and microtomography (μCT) were used to determine pore size distribution and porosity. The fabricated foams exhibited porosity >70% with open pores of 100–400 μm in size and pore walls containing numerous micropores of <10 μm. This pore structure satisfies the requirements for bone tissue engineering applications. The effects of Bioglass® addition on microstructure, mechanical properties and bioactivity of polyurethane scaffolds were evaluated. It was found that composite foams showed a higher storage modulus than neat polyurethane foams. The high bioactivity of composite scaffolds was confirmed by the rapid formation of hydroxyapatite on the foam surfaces upon immersion in SBF.     

原位水化法制备羟基磷灰石/壳聚糖复合支架材料

以含Ca2+和PO34-的溶液为无机相,壳聚糖(chitosan,CS)溶液为高分子相,采用原位水化法制备羟基磷灰石(hydroxyapatite,HAP)/CS复合多孔支架材料。XRD和IR的表征和分析表明水化24h后,复合支架中的钙磷盐从磷酸氢钙(dicalciumphos phate dehydrate,DCPD)转化为HAP。SEM和EDS显示15μm左右的棒状HAP颗粒均匀地分散在多孔支架的孔壁上,压缩强度的测试结果表明这种结构显著提高复合支架的力学性能。     

聚乳酸-羟基乙酸共聚物/磷酸钙骨水泥多孔复合支架的制备

利用定向冰晶-冷冻干燥法制备了具有定向孔隙结构的磷酸钙骨水泥支架材料, 将两种具有不同降解速率的聚乳酸-羟基乙酸共聚物(PLGA) 与磷酸钙骨水泥多孔支架进行多次浸润复合, 以改善支架的力学性能。结果表明: PLGA 与支架材料复合可大大提高复合支架材料的抗压强度, 经过PLGA 二次复合后, 复合支架抗压强度可达6. 37 MPa ±0. 54 MPa 。经过PLGA 复合的支架材料保持了复合前的孔隙结构, 在孔的轴向方向上具有定向排列的开口孔隙, 这些开口孔隙的存在有利于植入初期新生组织的长入。覆盖在骨水泥基体表面的PLGA 膜可以增强基体的强度并弥补基体表面的缺陷, 充填在孔隙内部的PLGA 泡沫体可以很好地承受外加载荷, 使复合支架材料具有较好的强度和韧性。      

Fabrication of HA/PHBV composite scaffolds through the emulsion freezing/freeze-drying process and characterisation of the scaffolds

Biodegradable polymer-based scaffolds containing osteoconductive hydroxyapatite (HA) particles can be very useful for bone tissue engineering. In this investigation, HA nanoparticles were incorporated in poly(hydroxybutyrate-co-valerate) (PHBV) polymer to fabricate osteoconductive composite scaffolds. PHBV and HA/PHBV scaffolds were made using an emulsion freezing/freeze-drying technique. The scaffolds produced were subsequently characterized using several techniques. It was found that the scaffolds were highly porous and had interconnected porous structures. The pore size ranged from several microns to around 300 mum. The spherical HA nanoparticles which were produced in-house through a nanoemulsion process could be incorporated into composite scaffolds although some of these nanoparticles existed on the surface of pore walls when a relatively large amount of HA was used for composite scaffolds. The incorporation of HA nanoparticles also enhanced compressive mechanical properties of the scaffolds.     

3-D high-strength glass–ceramic scaffolds containing fluoroapatite for load-bearing bone portions replacement

This study aimed to fabricate and investigate the structure, mechanical properties and bioactivity of three-dimensional (3-D) glass–ceramic scaffolds for bone tissue engineering. The scaffold material was a fluoroapatite-containing glass–ceramic synthesized by a melting–quenching route. Glass–ceramic powders were mixed with polyethylene particles acting as pore formers; the blend was pressed to obtain “green” compacts that were thermally treated to remove the organic phase and to sinter the inorganic one. The structure and morphology of the resulting scaffolds were characterized by X-ray diffraction, scanning electron microscopy, density measurements and capillarity tests. Crushing tests were carried out to investigate the mechanical properties of the scaffolds. The in vitro bioactivity was assessed by soaking the scaffolds in simulated body fluid for different time frames and by analyzing the modifications that occurred on the sample surface. The scaffolds had an interconnected macroporous structure with pores up to 50% vol. and they showed an orthotropic mechanical behaviour and strength well above 20 MPa. In addition, in vitro tests put into evidence the excellent bioactivity of the material. Therefore, the prepared scaffolds can be used in bone reconstructive surgery as effective load-bearing grafts thanks to their ease of tailoring, bioactive properties and high mechanical strength.     

Fabrication of fibrous poly(butylene succinate)/wollastonite/apatite composite scaffolds by electrospinning and biomimetic process

In this paper, a novel kind of Poly(butylene succinate) (PBSU) /wollastonite/apatite composite scaffold was fabricated via electrospinning and biomimetic process. Pure PBSU scaffold and composite scaffolds with 12.5 wt% and 25 wt% wollastonite were firstly fabricated by electrospinning. SEM micrographs showed that all the electrospun scaffolds had homogeneous fibrous structures with interconnected pores and randomly oriented ultrafine fibers. The composite scaffolds were then surface modified using a biomimetic process. SEM and XRD results showed that apatite could deposit on the surfaces of the composite fibers after incubation in SBF and a novel fibrous structure with microspheres composed of worm-like apatite on composite fibers was formed. Incubation time and wollastonite content were found to influence the morphology of the scaffolds during the biomimetic process obviously. Both the amount and the size of the microspheres on the composite scaffolds increased with increased incubation time. After a certain incubation time, microspheres formed on the composite fibers with less wollastonite had a relatively larger size. Therefore, the microstructure of the composite scaffolds could be adjusted by controlling the wollastonite content and the incubation time. All of these results suggest that it is an effective approach to fabricate PBSU/wollastonite/apatite fibrous composite scaffolds with different material content and controllable microstructure for bone tissue engineering.     

纳米羟基磷灰石/聚己内酯复合生物活性多孔支架研究

采用水热法制备了纳米羟基磷灰石（n-HA）及其与聚己内酯（PCL）的复合材料. 用熔融浇铸/食盐微粒浸出法制备了孔径在200～400μｍ、大孔互相贯通的复合材料支架. 通过细胞培养和体内动物实验研究了该支架的生物学性能. 结果表明,复合支架的孔隙率随致孔剂用量的增加而增加,而抗压强度随之而减小;支架的最大孔隙率可达86%,相应的抗压强度为2.4MPa. 成骨细胞在支架上的细胞粘附率和增殖随磷灰石含量增加而提高,复合材料明显高于单纯的PCL支架. 组织学观察显示,新生骨长入多孔支架和复合材料形成了直接的骨性结合. n-HA/PCL复合材料支架有很好的生物相容性和生物活性.     

几种聚乳酸／生物活性陶瓷复合材料生物活性的比较

采用溶解共混法制备含30％硅灰石的聚乳酸／硅灰石新型生物医用复合物膜．将其放入37．5℃模拟体液中,分别在1,3和6d取出样品,从沉积物形成速度以及沉积物的量考察复合物的生物活性,并与目前研究应用较多的聚乳酸／羟基磷灰石、聚乳酸／磷酸三钙以及聚乳酸／珍珠层粉进行比较。扫描电镜和红外光谱分析表明,聚乳酸／硅灰石、聚乳酸／羟基磷灰石和聚乳酸／磷酸三钙复合物膜的生物活性明显优于聚乳酸／珍珠层粉,这三种复合物膜表面在浸泡一天时表面出现类骨羟基磷灰石沉积物,6d时表面完全被沉积物覆盖。聚乳酸／硅灰石复合物材料具有较好的生物活性,适于应用在骨修复以及骨组织工程领域。     

Effect of enzymatic degradation of chitosan in polyhydroxybutyrate/chitosan/calcium phosphate composites on in vitro osteoblast response

Polyhydroxybutyrate/chitosan/calcium phosphate composites are interesting biomaterials for utilization in regenerative medicine and they may by applied in reconstruction of deeper subchondral defects. Insufficient informations were found in recent papers about the influence of lysozyme degradation of chitosan in calcium phosphate/chitosan based composites on in vitro cytotoxicity and proliferation activity of osteoblasts. The effect of enzymatic chitosan degradation on osteoblasts proliferation was studied on composite films in which the porosity of origin 3D scaffolds was eliminated and the surface texture was modified. The significantly enhanced proliferation activity with faster population growth of osteoblasts were found on enzymatically degraded biopolymer composite films with α-tricalcium phosphate and nanohydroxyapatite. No cytotoxicity of composite films prepared from lysozyme degraded scaffolds containing a large fraction of low molecular weight chitosans (LMWC), was revealed after 10 days of cultivation. Contrary to above in the higher cytotoxicity origin untreated nanohydroxyapatite films and porous composite scaffolds. The results showed that the synergistic effect of surface distribution, morphology of nanohydroxyapatite particles, microtopography and the presence of LMWC due to chitosan degradation in composite films were responsible for compensation of the cytotoxicity of nanohydroxyapatite composite films or porous composite scaffolds.     

Efficient and toxicity-free surface immobilization of nano-hydroxyapatite for bone-regenerative composite scaffolds by grafting polyvinyl pyrrolidone

An effective approach to fabricate porous bone regenerative composite scaffolds with surface-immobilized nano-hydroxyapatite (nHA) is developed in this research. In the typical preparation process, surface-repellent stable colloidal nHA with surface carbonyl functionality was fabricated through in-situ polyvinyl pyrrolidone (PVP)-grafting synthesis without any organic solvents and potentially harmful additives. Followed by freezing and lyophilizing homogenous PVP-grafted nHA and chitosan mixtures, three dimensional nHA and chitosan composite scaffolds were then obtained. The TEM images and XPS analysis show that the discrete nHA was anchored at nano-level on the pore surface of chitosan scaffold by mediating PVP chemical-linkage. The PVP-grafting offers an efficient and safe approach to prepare nHA with the surface reactivity and is promising to be widely used in the fabrication of novel composite scaffolds for bone tissue engineering.     

Biocompatibility,degradability, bioactivity and osteogenesis of mesoporous/macroporous scaffolds of mesoporous diopside/poly(l-lactide) composite

Bioactive mesoporous diopside (m-DP) and poly(l-lactide) (PLLA) composite scaffolds with mesoporous/macroporous structure were prepared by the solution-casting and particulate-leaching method. The results demonstrated that the degradability and bioactivity of the mesoporous/macroporous scaffolds were significantly improved by incorporating m-DP into PLLA, and that the improvement was m-DP content-dependent. In addition, the scaffolds containing m-DP showed the ability to neutralize acidic degradation products and prevent the pH from dropping in the solution during the soaking period. Moreover, the scaffolds containing m-DP enhanced attachment, proliferation and alkaline phosphatase activity of MC3T3-E1 cells, which were also m-DP content-dependent. Furthermore, the histological and immunohistochemical analysis results showed that the scaffolds with m-DP significantly promoted new bone formation and improved the materials degraded in vivo, indicating good biocompatibility. The results suggested that the mesoporous/macroporous scaffolds of the m-DP/PLLA composite with osteogenesis had a potential for bone regeneration.     

硅酸钙纳米线复合电纺丝支架的制备及离子释放研究

电纺丝支架已被广泛用于组织工程领域, 其中硅酸钙等生物活性陶瓷复合的电纺丝支架, 在应用中展现出了优异的生物活性。硅酸钙复合电纺丝支架中硅酸钙降解释放的硅酸根离子(SiO₃^2-)已被证实具有促进成血管性能, 但其有效活性离子浓度范围比较窄, 仅在0.79~1.8 μg/mL之间。因此精确控制组织工程材料的离子释放浓度, 使材料释放的离子能较长时间保持在有效活性浓度范围, 对于组织工程应用具有重要意义。本研究通过调节电纺丝孔径大小及硅酸钙纳米线的不同复合方式, 制备了多种硅酸钙复合电纺丝纤维支架, 并比较了其在体外环境下的离子释放模式及对人脐静脉内皮细胞的增殖促进作用。实验结果表明, 混纺及同时电喷-电纺复合方式的小孔径硅酸钙复合电纺支架由于高分子的疏水作用和小孔径结构对离子扩散的阻碍, 可以实现离子缓释。通过体外细胞实验发现, 具有离子缓释效果的支架可以更好地促进人脐静脉内皮细胞的增殖, 说明通过调控支架离子缓释, 可以有效调控其生物活性, 获得最佳组织工程应用效果。     

海藻酸钙水凝胶/聚乳酸复合材料的制备与性能

通过化学发泡-冷冻干燥-粒子滤出复合法制备聚乳酸(PLLA)大孔支架, 然后在大孔内以海藻酸钠(SA)、碳酸钙、葡萄糖酸内酯(GDL)为原料, 通过原位相转变制备海藻酸钙水凝胶/聚乳酸复合材料(CA/PLLA); 分别利用SEM、压缩强度测试和细胞培养对CA/PLLA支架的形貌、力学性能及生物相容性进行了研究。结果表明: PLLA具有直径小于2 mm、孔道相互连通的孔洞, 且在大孔中能够形成均匀的CA。CA/PLLA复合材料的压缩强度(2.74 MPa)远大于单一的海藻酸钙水凝胶的压缩强度(0.10 MPa)。在CA/PLLA复合支架中, 软骨细胞呈簇状圆形生长状态, 与其在天然软骨陷窝里生长状态一致。这种软硬结合、天然与合成高分子杂化的CA/PLLA复合材料的力学强度和生物相容性同时得到提高, 可进一步作为骨和软骨修复材料研究。