In Vitro Characterizations of PLLA/β-TCP Porous Matrix Materials and RMSC-PLLA-β-TCP Composite Scaffolds

To develop a novel degradable poly (L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) bioactive materials for bone tissueengineering, β-TCP powder was produced by a new wet process. Porous scaffolds were prepared by three steps, i.e. solventcasting, compression molding and leaching stage. Factors influencing the compressive strength and the degradation behaviorof the porous scaffold, e.g. weight fraction of pore forming agent-sodium chloride (NaCl), weight ratio of PLLA: β-TCP,the particle size of β-TCP and the porosity, were discussed in details. Rat marrow stromal cells (RMSC) were incorporatedinto the composite by tissue engineering approach. Biological and osteogenesis potential of the composite scaffold weredetermined with MTT assay, alkaline phosphatase (ALP) activity and bone osteocalcin (OCN) content evaluation. Resultsshow that PLLA/β-TCP bioactive porous scaffold has good mechanical and pore structure with adjustable compressive strengthneeded for surgery. RMSCs seeding on porous PLLA/     

Osteogenesis and Degradation Behavior of rhBMP-2/β-Tricalcium Phosphate Porous Composite Materials

Ultrafine β-tricalcium phosphate (β-TCP) powders with good crystalline structure were produced by a new wet process. Through bone tissue engineering approach, porous β-TCP ceramic was combined with recombined human bone morphogenetic proteins-2 (rhBMP-2) to develop a novel composite material. Osteogenesis capacity of the composite was investigated intramuscularly in rat with histological analyses and SEM examination. Pure β-TCP porous ceramic was investigated as the control. Results show that the composite materials possess good biocompatibility, biodegradation and strong osteogenesis capacity through inductive process after implantation. Material degradation began from 2 weeks post-implantation accompanying with the changing of pore structure, with the enwrapping and separation of materials by hyperplatic mesenchymal cells and fibroblast, and with the phagocytose reaction of multinucleated giant cells. Early in 72 h, immature cartilage could be found within novel composite; mature lamellar bone was induced to generate after 3 weeks. With strong osteoinduction capacity and controllable biodegradation, the novel rhBMP-2/β-TCP porous ceramic is expected to be a promising bone grafting substitute for bone tissue engineering.     

Hierarchical Micropore/Nanorod Apatite Hybrids In-Situ Grown from 3-D Printed Macroporous Ti6Al4V Implants with Improved Bioactivity and Osseointegration

The advent of three-dimensional(3-D) printed technique provides great possibility in the fabrication of customized porous titanium(Ti) implant. However, the bioinert property of the printed Ti poses an outstanding problem. Hybrid micro-arc oxidation and hydrothermal(MAO–HT) treatment on porous metals is able to produce multi-scaled hierarchical orthopedic implant, showing great potential for surface modification of 3-D printed implant. In this study, cylindrical porous Ti6Al4V(Ti64) scaffolds with pore size of 640 μm, porosity of 73% were 3-D printed by electron beam melting process, and their surfaces were left untreated or treated by a combined MAO–HT procedure. In vitro bioactivity was tested by immersion in simulated body fluid for different time points. Then, 12 scaffolds in each group were implanted into the femoral condyles of New Zealand rabbit for 8 weeks. Osseointegration was evaluated by qualitative and quantitative histological analysis, and the bone ingrowth features were probed by sequential fluorescent labeling at 3 and 6 weeks post-surgery. Following the MAO–HT treatment, the porous Ti64 scaffold was endowed with multi-scaled micro/nano-topographies and high amounts of Ca P on its surface.The treated scaffold exhibited drastically enhanced apatite forming ability compared with the untreated one. In vivo test revealed significantly that a higher amount of bone ingrowth and bone implant contact at the treated scaffold. The 2 types of scaffolds had different patterns of bone ingrowth: the treated scaffold exhibited a pattern of contact osteogenesis, by which bone formed directly on the treated implant surface, whereas bone formed distal to the implant surface of the untreated scaffold. MAO–HT treatment can significantly enhance the in vitro apatite-inducing ability and in vivo osseointegration capacity of 3-D porous Ti64 scaffold and may provide as a viable approach for the fabrication of bioactive 3-D printed porous implant for orthopedic applications.     

Novel synthesis method combining a foaming agent with freeze-drying to obtain hybrid highly macroporous bone scaffolds

Three-dimensional macroporous scaffolds are commonly used in bone tissue engineering applications since they provide sufficient space for cell migration and proliferation, facilitating bone ingrowth and implant vascularisation. The aim of this work was to combine two simple methods, freeze-drying and gas-foaming, in order to fabricate highly macroporous bone scaffolds made of chitosan/agarose matrix reinforced with nanohydroxyapatite. The secondary goal of this research was to comprehensively assess biomedical potential of developed biomaterials. In this work, it was demonstrated that simultaneous application of freeze-drying and gas-foaming technique allows to obtain hybrid(as proven by ATR-FTIR)macroporous bone scaffolds(pore diameter 50 um) characterized by high open(70%) and interconnected porosity. Novel scaffolds were non-toxic, favoured osteoblasts adhesion and growth and induced apatite formation on their surfaces, indicating their high bioactivity that is essential for good implant osseointegration. Biomaterials were also prone to enzymatic degradation, degradation in acidified microenvironment(e.g. osteoclast-mediated), and slow degradation under physiological p H of 7.4.Moreover, the scaffolds revealed microstructure(70% open porosity, SSA approx. 30 m2/g, high share of macropores with diameter in the range 100-410 um) and compressive strength(1–1.4 MPa) comparable to cancellous bone, indicating that they are promising implants for cancellous bone regeneration.     

Ultrastructural Analysis on the Osteogenesis and Transformation of Calcium Phosphate Ceramics in Vivo

To study the osteogenesis and transformation process of calcium phosphate bioceramic in vivo, biodegradable porous β-tricalcium phosphate ceramics (β-TCP, φ5×8 mm) were implanted in the tibia of rabbits. β-TCP ceramics with surrounding bone tissue were retrieved and observed by SEM, TEM and EPMA every month after implantation.The results showed that osteogenesis was active and β-TCP ceramics bonded to bones directly. The new bones were forming and maturing as materials were continuously degrading, and materials were finally replaced by new bone. Parts of the materials were degraded, absorbed and recrystallized, while the rest were dispersed to the spongy bone and the Haversian lamella in an irregular arrangement, becoming incorporated into bone formation directly by remodeling the structure. Some β-TCP crystals cleaved along its (001) rhombohedral plane and formed lath-like crystals in vivo.     

Evaluating and Modeling the Mechanical Properties of the Prepared PLGA/nano-BCP Composite Scaffolds for Bone Tissue Engineering

In this paper, preparation of nano-biphasic calcium phosphate (nBCP), mechanical behavior and load-bearing of poly (lactide-co-glycolide) (PLGA) and PLGA/nBCP are presented. The nBCP with composition of 63/37 (w/w) HA/β-TCP (hydroxyapatite/β-tricalcium phosphate) was produced by heating of bovine bone at 700℃. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation (TIPS) at -60℃ under 4 Pa (0.04 mbar) vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.     

EPMA Study of the Interface of β-Tricalcium Phosphate Ceramics in Vivo

Electron probe and X-ray energy spectrum were used to investigate the chemical composition of the interface between material and new bone after porous tricalcium phosphate ceramic implanted in tibia of rabbits. The element changes of the interface, the materials transformation and the situation of new bone formation at different implantation period were observed. The results showed that the carbon element content decreased gradually in new bone tissue, and the content of calcium and phosphor element increased by degrees with the implantation time. At the same time, calcium-phosphor ratio in the new bone kept a higher level. New bone grew into the materials interior, material dispersed and degraded simultaneously. Both composition of materials and new bone tended to be consentient. Finally, the materials were substituted by new bone. After implantation, not only the materials itself dissolved and degraded partially, but also new bone formed on the outer and pore surface of β-TCP porous bioceramics, which showed that the degradation products of lifeless calcium phosphate inorganic materials took part in constituting of new bone tissue.     

EPMA Study of the Interface of β-Tricalcium Phosphate Ceramies in Vivo

Electron probe and X-ray energy spectrum were used to investigate the chemical composition of the interface between material and new bone after porous tricalcium phosphate ceramie implanted in tibia of rabbits. The element changes of the interface, the materials transformation and the situation of new bone formation at different implantation period were observed. The results showed that the carbon element content decreased gradually in new bone tissue, and the content of calcium and phosphor element increased by degrees with the implantation time. At the same time, calcium-phosphor ratio in the new bone kept a higher Ievel. New bone grew into the materials interior, material dispersed and degraded simultaneously. Both composition of materials and new bone tended to be consentient. Finally, the materials were substituted by new bone. After implantation, not only the materials itself dissolved and degraded partially, but also new bone formed on the outer and pore surface of β-TCP porous bioceramics, which     

Electrospun multifunctional tissue engineering scaffolds

Tissue engineering holds great promises in providing successful treat- ments of human body tissue loss that current methods are unable to treat or unable to achieve satisfactory clinical outcomes. In scaffold-based tissue engineering, a high- performance scaffold underpins the success of a tissue engineering strategy and a major direction in the field is to create multifunctional tissue engineering scaffolds for enhanced biological performance and for regenerating complex body tissues. Electrospinning can produce nanofibrous scaffolds that are highly desirable for tissue engineering. The enormous interest in electrospinning and electrospun fibrous structures by the science, engineering and medical communities has led to various developments of the electrospinning technology and wide investigations of eiectrospun products in many industries, including biomedical engineering, over the past two decades. It is now possible to create novel, multicomponent tissue engineering scaffolds with multiple functions. This article provides a concise review of recant advances in the R ＆ D of electrospun multifunctional tissue engineering scaffolds. It also presents our philosophy and research in the designing and fabrication of electrospun multicomponent scaffolds with multiple functions.     

Preparation and application of highly porous aerogel-based bioactive materials in dentistry

In this study, the possibility of preparation and application of highly porous silica aerogel-based bioactive materials are presented. The aerogel was combined with hydroxyapatite and p.tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in themesoporous region with a maximum pore diameter of 7,4 and 12.7 nm for the composite materials. The newly developed bioactive materials were characterized by scant electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.     

原位共聚法制备聚DL丙交酯/β-磷酸三钙复合材料及性能研究

采用原位共聚法制备聚DL丙交酯/β-磷酸三钙(PDLLA/β-TCP)复合骨修复材料.以辛酸亚锡作引发剂,将一定比例的β-磷酸三钙与DL丙交酯(DLLA)混匀后在真空体系下开环聚合,并持续均匀振荡,得到PDLLA/β-TCP复合材料.通过扫描电镜(SEM)、能谱分析(EDS)表征复合材料的有机-无机界面及整体复合情况;通过复合材料中PDLLA分子量及复合材料力学强度的测试考察了β-TCP的较佳加入量.研究发现:复合材料中β-TCP在PDLLA基质中分布均匀,有机-无机界面结合紧密;β-TCP比例越大,复合材料中PDLLA分子量越小;β-TCP对材料强度有增强作用,当β-TCP比例为30 wt%时,复合材料抗压强度可达99 MPa,抗弯强度可达76 MPa.     

水基高固相含量β-磷酸三钙浆料的制备及其流变性研究

为了制备出高固相体积含量、分散性好的β-TCP陶瓷浆料,本文系统地研究了影响β-TCP浆料流变性的因素如浆料的pH值、分散剂的用量、固相含量、球磨时间等.实验表明,当pH值=9时,加入2%(体积分数)左右的分散剂,球磨8h,能够制备出满足凝胶注模成型工艺的高固相含量、低粘度β-TCP/BG陶瓷浆料.     

共沉淀法制备HA/β-TCP双相生物陶瓷粉末新工艺研究

在加热条件下，通过调节Ca(NO3)2-(NH4)2HPO4-NH3H2O-H2O体系的pH值．制得了不同HA和β-TCP比例的纯双相粉末．并对其反应历程进行了初步研究。新工艺和常规方法比较，大大缩短了陈化时间，反应重复性好。     

β-TCP porous pellets as an orthopaedic drug delivery system: ibuprofen/carrier physicochemical interactions

Abstract

Calcium phosphate bone substitute materials can be loaded with active substances for in situ, targeted drug administration. In this study, porous β-TCP pellets were investigated as an anti-inflammatory drug carrier. Porous β-TCP pellets were impregnated with an ethanolic solution of ibuprofen. The effects of contact time and concentration of ibuprofen solution on drug adsorption were studied. The ibuprofen adsorption equilibrium time was found to be one hour. The adsorption isotherms fitted to the Freundlich model, suggesting that the interaction between ibuprofen and β-TCP is weak. The physicochemical characterizations of loaded pellets confirmed that the reversible physisorption of ibuprofen on β-TCP pellets is due to Van der Waals forces, and this property was associated with the 100% ibuprofen release.     

不同反应条件对原位聚合聚DL丙交酯/β-磷酸三钙复合材料强度的影响

在骨修复领域以无机钙质成分增强的聚乳酸基复合材料应用最为广泛.本文采用原位共聚法制备聚DL丙交酯/β-磷酸三钙(PDLLA/β-TCP)复合骨修复材料.以辛酸亚锡作引发剂,将一定比例的β-磷酸三钙与D L丙交酯(DLLA)混匀后在真空体系下开环聚合,并持续均匀振荡,得到PDLLA/β-TCP复合材料.研究发现,TCP的加入对材料强度有增强作用,但β-TCP的加入对PDLLA的分子量将造成不利影响.在引发剂质量分数为0.1%,150℃反应16h,β-TCP的加入量为30%条件下,材料抗压强度达95MPa,抗弯强度达69MPa.     

β-TCP porous pellets as an orthopaedic drug delivery system: ibuprofen/carrier physicochemical interactions

Calcium phosphate bone substitute materials can be loaded with active substances for in situ, targeted drug administration. In this study, porous β-TCP pellets were investigated as an anti-inflammatory drug carrier. Porous β-TCP pellets were impregnated with an ethanolic solution of ibuprofen. The effects of contact time and concentration of ibuprofen solution on drug adsorption were studied. The ibuprofen adsorption equilibrium time was found to be one hour. The adsorption isotherms fitted to the Freundlich model, suggesting that the interaction between ibuprofen and β-TCP is weak. The physicochemical characterizations of loaded pellets confirmed that the reversible physisorption of ibuprofen on β-TCP pellets is due to Van der Waals forces, and this property was associated with the 100% ibuprofen release.     

碳酸氢氨制孔制备聚乳酸(PLLA)/β磷酸三钙(β-TCP)复合骨修复多孔支架材料

采用混合溶剂(氯仿,丙酮)溶解后的聚乳酸(PLLA)与β磷酸三钙(β-TCP)、制孔剂碳酸氢氨(NH4HCO3)复合,冷冻干燥成型制备聚乳酸/β磷酸三钙多孔复合支架材料.正交实验结果表明,适当比例的混合溶剂在-10℃间体积收缩干燥制备的材料具有良好的成型性能和力学强度,碳酸氢氨(粒径200～400μm)质量比为30%(wt),PLLA/β-TCP质量比为1:1时,制备的支架材料抗压强度5.6MPa,孔隙率66.3%,孔径200～400μm.得到理想的复合骨修复多孔支架材料.     

Preparation of PLGA/β-TCP composite scaffolds with supercritical CO 2 foaming technique

A high porosity scaffold with suitable compressive strength prepared by a gentle method has become a pressing need. To meet this demand, poly(DL-lactide-co-glycolide) (PLGA) and β-tricalcium phosphate (β-TCP) were designed to prepare composite scaffolds by the supercritical technique. The preparation process consisted of three units: the mixing of PLGA and β-TCP, compression molding of the mixture, and the foaming process. Six influencing factors — temperature, pressure of the scCO₂ system, maintaining time of scCO₂, the ratio of β-TCP to PLGA, the rate of depressurization, and the molecular weight — were investigated. The results collectively indicated that the optimized conditions for the foaming process were that CO₂ pressure and temperature be 8MPa and 39°C, respectively, which should be kept for 8h; the content of β-TCP in the mixture should be 25% and the depressurizing rate be 0.1 MPa/s, using PLGA of an 80kDa molecular weight. Scaffolds with a porosity of 65.47% and a compressive strength of 4.76 MPa could be obtained. The pore size ranged around 100 µm. The material’s use as tissue engineering scaffolding is expected.     

Sol-gel prepared β-TCP/FHA biphasic coatings

β-tricalcium phosphate/fluoridated hydroxyapatite (β-TCP/FHA) biphasic coatings were prepared on titanium alloy substrate by means of sol-gel method. The coatings combine the initial dissolution of β-TCP with the long-term stability of FHA to create a high quality bioactive coating. Ca(NO₃)₂, P₂O₅ and HPF₆ were dissolved in ethanol respectively and mixed in designed sequence and Ca : P : F ratios to form a sol. After the sol was refluxed for 24 h, the as-refluxed sol was used for FHA coating. β-TCP powders were dispersed into the sols to form colloidal sols for β-TCP/FHA biphasic coatings. The as-refluxed sols with different Ca : P : F ratios only resulted in apatite coatings with low F content. Biphasic coatings were prepared with the colloidal sols. The β-TCP contents of the coatings could be tailored by varying the amount of the powders in the colloidal sols. The surface morphology of the coatings becomes rougher with increasing amount of the powders, which favors cell attachment. However, excessive amount of powders results in powder agglomeration, leading to more cracks in the coatings. Fine powders and good dispersion are essential factors for good biphasic coatings.