Hydroxyapatite/β-tricalcium Phosphate Composite for Guiding Bone Tissue Growth into a Titanium Tube in 8 mm Dog Tibia Cavity Defects

We developed a fixation method and evaluate bone regrowth in the cavities of a Ф4 mm× 8 mm titanium（Ti）tube through porous hydroxyapatite（HAP）/β-tricalcium phosphate（β-TCP）composite filling（group A）,chitosan/calcium phosphate composite filling（group B）,and HAP particle modification（group C）.After 2 and 5 months of implantation in dog tibia defects,new bone formation in the three groups was studied by histology and histomorphometry.Group A displayed the most bone regenerated area in both 2 and 5 months post-operation.The chitosan/calcium phosphate composite in group B mostly degraded 2 months after implantation,leading to fibrous tissue invasion after 5 months.By contrast,less bone formation was observed in group C.These results indicated that filling the cavities of metalprostheses with a porous HAP/β-TCP composite can be used for stable long-term fixation in clinicalsettings.

Effect of Fluoride on the Ion-association of Calcium Phosphate and Crystallization of Hydroxyapatite

Using a titration setup to accurately control the reaction conditions and in situ monitor the reaction,we showed that fluoride exhibited negligible effects on the ion association process of calcium and phosphate and the formation of ACP nanospheres in a buffer solution with constant ionic strength.However,the stability of ACP increased with increasing fluoride concentration,which was ascribed to the inhibitory effect of fluoride on the aggregation of ACP nanospheres and the nucleation of nanocrystals on the surface of ACP nanospheres.Furthermore,fluoride could inhibit the lateral growth of HAP nanosheets and promote the formation of rod-like crystals.These results further improve our understanding of the crystallization pathway of HAP crystals and the regulatory effects of fluoride.

Calcium phosphate conversion technique:A versatile route to develop corrosion resistant hydroxyapatite coating over Mg/Mg alloys based implants

Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.

X-ray diffraction investigation of amorphous calcium phosphate and hydroxyapatite under ultra-high hydrostatic pressure

The changes in the crystal structures of synthetically prepared amorphous calcium phosphate（ACP） and hydroxyapatite（HAP） in water（1：1 mass ratio） were studied by synchrotron X-ray diffraction（XRD） under ultra-high hydrostatic pressures as high as 2.34 GPa for ACP and 4 GPa for HAP. At ambient pressure, the XRD patterns of the ACP and HAP samples in capillary tubes and their environmental scanning electron micrographs indicated amorphous and crystalline characteristics for ACP and HAP, respectively. At pressures greater than 0.25 GPa, an additional broad peak was observed in the XRD pattern of the ACP phase, indicating a partial phase transition from an amorphous phase to a new high-pressure amorphous phase. The peak areas and positions of the ACP phase, as obtained through fitting of the experimental data, indicated that the ACP exhibited increased pseudo-crystalline behavior at pressures greater than 0.96 GPa. Conversely, no structural changes were observed for the HAP phase up to the highest applied pressure of 4 GPa. For HAP, a unit-cell reduction during compression was evidenced by a reduction in both refined lattice parameters a and c. Both ACP and HAP reverted to their original structures when the pressure was fully released to ambient pressure.

Hybrid Composites of Phosphate Glass Fibre/Nano-Hydroxyapatite/Polylactide: Effects of Nano-Hydroxyapatite on Mechanical Properties and Degradation Behaviour

Hydroxyapatite/polylactide (HA/PLA) composites have been intensively investigated for their potential as biodegradable fixation devices to heal bone fractures. However, most of these composites failed to achieve a bone-mimicking level of mechanical properties, which is an essential demand of the targeted application. In this study, the nano-hydroxyapatite/polylactide composites were used as the matrix and continuous phosphate glass fibres (PGF) served as the major reinforcement to obtain the nano-HA/PGF/PLA hybrid composites. While the PGF volume fraction remained constant (25%), the nano-HA content (in weight) varied from 0% to 20%. As nano-HA loading increased, the flexural modulus of the composites increased from 8.70 ± 0.35 GPa to 14.97 ± 1.30 GPa, and the flexural strengths were enhanced from 236.31 ± 10.83 MPa to 310.55 ± 22.88 MPa. However, it is found that the degradation rates are higher with more nano-HA loaded. Enhanced water absorption ability, as well as increased voids in the composites is possible reasons for the accelerated degradation of composites with higher nano-HA loading. The hybrid composites possess mechanical properties that are superior to most of the HA/PLA composites in previous research while maintaining the biodegradability. With a proper loading of nano-HA in composites of 10 weight percent, the composites are also found with improved mechanical properties without catastrophic degradation. The composites developed in this study have great potential as biodegradable bone fixation device with enhanced load-bearing ability as confirmed and superior bioactivity as anticipated.

Development and characterization of α-tricalcium phosphate/monocalcium aluminate composite bone cement

Calcium phosphate cements have received much attention in recent decades owing to their biocompatibility, in situ handling, and shaping abilities. However, their low initial mechanical strength is still a major limitation. On the other hand, calcium aluminate cements (CACs) set fast and have a high initial strength and good corrosion resistance in contact with body fluids, making them excellent dental restorative materials. Therefore, the chemical, mechanical and biological properties of new-TCP/CA cement after aging in simulated body fluid (SBF) were investigated. The results indicated that the composites have setting times not appropriated for immediate applications and have degradation rates higher than those of the traditional CPCs. Moreover, the compressive strength of composite was lower than 5MPa and did not increase with SBF immersion. However, the α-TCP/CA composites showed a higher bioactivity at early stages and were not only more biocompatible but also more noncytotoxic.

Osteogenesis and Degradation Behavior of rhBMP-27/β-Tricalcium Phosphate Porous Composite Materials

Ultrafine-tricalcium phosphate(β-TCP)powders with good crystalline structure were produced by a new process through bone tissue engineering approach rorous β-TCPcermic 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 pureβ-TCP porous carmic wsa investigated as the control results show that the compostie materials possess good bilcompatibility biodegradation and strong osteogenesis capacity through inductive process after implantation material degradation began from 2 weeks post-implantation accompanying with the changing o pore structure with the enwrapping and separation fo materials by hyperplatic mesenchymal cells and fibroblast and with the phagocytose reaction of multinucleated giant cells early in 72h immature cartilage could be found within novel composite mature lamellar bone was induced to generate after 3 weeks with strong osteoinduction capacity and controlable bildegradation the novel rhBMP-2\β-TCP porous ceramic is expected to be a promising bone grafting substitute for bone tissue engineering

Three-dimensional printing of β-tricalcium phosphate/calcium silicate composite scaffolds for bone tissue engineering

Bioactive scaffolds with interconnected porous structures are essential for guiding cell growth and new bone formation. In this work, we successfully fabricated three-dimensional （3D） porous β-tricalcium phosphate （β-TCP）/calcium silicate （CS） composite scaffolds with different ratios by 3D printing technique and further investigated the physiochemical properties, in vitro apatite mineralization properties and degradability of porous β-TCP/CS scaffolds. Moreover, a series of in vitro cell experiments including the attachment, proliferation and osteogenic differentiation of mouse bone marrow stromal cells were conducted to testify their biological performances. The results showed that 3D printed β-TCP/CS scaffolds possessed of controllable internal porous structures and external shape. Furthermore, the introduction of CS decreased the shrinkage of scaffolds and improved the in vitro apatite formation activity and degradation rate. Meanwhile, compared with pure β- TCP scaffold, the β-TCP/CS composite scaffolds were more conducive to promote cell adhesion, spread and osteogenesis differentiation. However, when the content of CS was increased to 45%, the ions dissolution rate of the composite scaffolds was so high that leaded to the increase in pH value, which inhibited the proliferation of cells. Our results suggested that the introduction of appropriate CS into β-TCP bioceramic is an effective strategy to prepare bioactive 3D printed bioceramic scaffolds for hard tissue regeneration.

Microemulsion Synthesis of Mesoporous β-tricalcium Phosphate Powder with a Novel System

The synthesis of mesoporous β-tricalcium phosphate(β-TCP)powder was performed by using the microemulsion approach,with hexadecyltrimethyl ammonium bromide(CTAB)/cyclohexane/n-octyl alcohol microemulsion system.The influences of different pH values and calcination temperatures on the phase composition of the β-TCP powder were studied.The in vitro proliferation of bone marrow mesenchymal stem cells(BMSCs)in the suspensions of β-TCP powders with meso-structure was studied.The phase composition,mesoporous structure,powder morphology,cell morphology and the optical density(OD)were characterized through X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),Fourier transform infrared(FTIR)spectroscopy,Nadsorption-desorption isotherms,inverted phase contrast microscopy and Multiskan spectrum,respectively.The mesoporous β-TCP powder with specific surface area of 12.85 m^(2)/g and the average pore size 7.11 nm was obtained through the microemulsion approach(100 g/L CTAB/250 mL/L cyclohexane/250 mL/L n-octyl alcohol)with a controlled pH of 7.0,after calcinating the powder at 800℃.It was confirmed that mesoporous β-TCP powder benefits the activity of BMSCs more than the non-mesoporous β-TCP powder.

Local Application of Alendronate on <i>β</i>-Tricalcium Phosphate Accelerated Induction of Osteogenesis with Formation of Giant Osteoclast-Like Cell

Intrinsic osteoinductivity—the ability to induce bone formation in ectopic sites without addition of osteogenic factors has been reported in various porous materials. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like cells are thought to play an important role in material-induced osteoinduction. To investigate the influence of osteoclastic activity on intrinsic osteoinduction, we loaded alendronate (10–2 , 10–4 , and 10–6 M) onto porous β-tricalcium phosphate (β-TCP) blocks to inhibit osteoclastic activity, and evaluated osteoinductivity by implantation of the blocks into the dorsal muscles of adult beagle dogs. Alendronate-loaded porous β-TCP blocks increased both speed and amount of osteoinduction, as measured 4 weeks after implantation, with the 10–4 M alendronate-loaded β-TCP being especially active. This finding indicates that β-TCP loaded with 10–4 M alendronate might prove crucial in providing the desirable balance between the degradation rate of bone scaffolds and their osteoinductive replacement. Thus, material-induced osteoinduction may be controlled by local application of alendronate, establishing alendronate loading as a promising therapeutic approach.

Microstructure and mechanical properties analysis of β-tricalcium phosphate/carbon nanotubes scaffold based on rapid prototyping

β-TCP ceramic scaffolds were fabricated with selective laser sintering (SLS) in this work. Carbon nanotubes (CNTs) were mixed with porous β-TCP matrix to enhance the mechanical performance of the bone tissue engineering scaffolds. Scaffold reconstruction and microstructure analysis were fulfilled based on micro-computed tomography (Micro-CT) scanning data. Results show that the strength of scaffold mixed with 0.2% CNTs reaches 0.819 MPa which has been improved by 85.7% compared with that without CNTs. Micro-CT analysis shows that the scaffold has a good interconnectivity, and pore size mainly distributes in the two regions of 60-340 μm and 500-620 μm.

Synthesis of Crystalline Hydroxyapatite from CaCO_3 and CaHPO_4·2H_2O by Mechanochemical Method

The mixture of CaHPO 4·2H 2O and CaCO 3 was ground in an aqueous system under appropriate conditions to investigate the mechanochemical reaction for the synthesis of crystalline hydroxyapatite (HA) powder. Hydroxyapatite of high crystallinity powder including trace Ca 10 (PO 4) 6CO 3(OH) and Ca 9HPO 4(PO 4) 6OH can be synthesized by mechanical activation without further thermal treatment at a high temperature. The synthesis reaction during the grinding process was almost completed within 1h. The as-ground powder exhibits a particle distribution of 20-100nm in size with a spherical or rodlike morphology. The composition and degree of crystallinity of the mechanochemical synthesized hydroxyapatite powders were coincident with the cement-type hydroxyapatite.

Microwave assisted synthesis & properties of nano HA-TCP biphasic calcium phosphate

Biphasic calcium phosphate （BCP） nanopowders were synthesized by using microwave and non-microwave irradiation assisted processes. The synthesized powders were pressed under a pressure of 90 MPa, and then were sintered at 1000-1200℃ for 1 h. The mechanical properties of the samples were investigated. The formed phases and microstructures were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results showed that the synthesis time was shorter, along with a more homogeneous microstructure, when the microwave irradiation assisted method was applied. The compression strength and the Young＇s modulus of the samples synthesized with microwave irradiation were about 60 MPa and 3 GPa, but those of the samples synthesized without microwave irradiation were about 30 MPa and 2 GPa, respectively. XRD patterns of the microwave irradiation assisted and non-microwave irradiation assisted nanopowders showed the coexistence of hydroxyapatite （HA） and lricalcium phosphate （TCP） phases in the system.

Alkaline treatment kinetics of calcium phosphate by piezoelectric quartz crystal impedance

Calcium phosphate film was prepared by electrochemical deposition technology. Subsequently, the alkaline treatment process of calcium phosphate film in 0.1 mol/L NaOH solution was monitored on real time by the piezoelectric quartz crystal impedance （PQCI） technique. The variations of morphology and composition for the alkaline treatment products were characterized by scanning electron microscopy （SEM）, Fourier transform infrared （FT-IR） and X-ray diffraction （XRD）, respectively. The dynamic variations of calcium phosphate can be characterized by the change of equivalent circuit parameters. The results show that the forming process of hydroxyapatite （HA） is composed of three stages： （1） acidic calcium phosphate dissolution; （2） phase transformation; and （3） HA formation. Furthermore, the correlative kinetic equations and parameters are obtained by fitting the static capacitance （C8）-time curves.

Synthesis of Biphasic Calcium Phosphate by Hydrothermal Route and Conversion to Porous Sintered Scaffold

Biphasic calcium phosphate (BCP) consisting of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) was successfully synthesized by new hydrothermal route using β-TCP as precursor. The X-ray diffraction analysis of as-synthesized powder indicated that β-TCP had been transformed into HA phase and amount of HA formed gradually increased with prolonged time. The results revealed that the recent technique may be able to control the composition of the obtained BCP which would influence the bioresorbability. Porous body of BCP was prepared by impregnation of polymeric sponge template with the slurry of the powder followed by sintering. The X-ray diffraction of porous product revealed that the composition of β-TCP increased after sintering indicating that HA had been decomposed. Porous BCP obtained from the recent technique possessed both macro and micropores structure which are useful for rapid tissue formation. Besides, the recent porous fabrication technique yielded porous BCP which preserved the sponge template morphology, enabling it to fabricate porous material with controlled pores structure.

In-situ growth of Ca/P salt on Ti surface induced by femtosecond lasers in hydroxyapatite suspension

Pure Ti plate surfaces are micro-ablated by femtosecond lasers in the ambience of hydroxyapatite suspension. It is found that three-stage hierarchical surface structures are produced with various laser energies. When the laser energy is 150μJ, a lava-like structure with a distribution of nanoholes is dispersed evenly on the laser ablated surface. While in the case of 300 μJ, the grooves-and-islands micro-patterns covered with nanoparticles are generated on the surface. Remarkably, Ca/P based substances are revealed to firmly deposit on the micro-structured surfaces. More phosphate growth is seen for the higher laser energy. Discussions suggest that the additional elements deposition could be attributed to the chemical reaction of plasma related ions in the suspension and their subsequent crystallisation on the fresh surfaces of Ti plate due to the femtosecond laser ablation.

羟基磷灰石的电化学制备及其除氟性

采用清洁简便的多扫循环伏安法制备出羟基磷灰石(HAP),利用X射线衍射仪与红外光谱仪分析了合成的中间产物二水磷酸氢钙(DCPD)、最终产物HAP的晶面结构与官能团。扫描电镜显示HAP的表面形貌呈现分散性较好的棒状结构。同时,以水中F^(-)为吸附对象,研究了水中条件参数如pH、温度、阴离子含量等对所合成HAP吸附F^(-)容量的影响。结果表明,在pH为3~6的范围内,HAP对F^(-)的吸附量随pH升高逐渐增大,并在pH为6时达到最大;pH在6~10的范围内,HAP对F^(-)的吸附量随pH升高逐渐下降。水中可能共存的阴离子如Cl^(-)、NO_(3)^(-)、SO_(4)^(2-)、CO_(3)^(2-),不干扰HAP对F^(-)的吸附。在15~55℃的温度范围内,温度升高,HAP吸附容量增加,并在55℃时达到8.36 mg/g的最大吸附量,高于文献中同类材料的吸附量;经过4次吸附-脱附试验,HAP对模拟废水中F^(-)的去除效果依然符合国家标准。此外,HAP对F^(-)的吸附是一熵增、吸热的自发过程,符合Langmuir-Freundlich、Dubinin-Radushkevich两种吸附等温模型,并遵循颗粒内扩散的动力学反应机制。

Effect of minor amounts of β-calcium pyrophosphate and hydroxyapatite on the physico-chemical properties and osteoclastic resorption of β-tricalcium phosphate cylinders

β-Tricalcium Phosphate(β-TCP),one of the most used bone graft substitutes,may contain up to 5 wt%foreign phase according to standards.Typical foreign phases includeβ-calcium pyrophosphate(β-CPP)and hydroxyapatite(HA).Currently,the effect of small amounts of impurities on β-TCP resorption is unknown.This is surprising since pyrophosphate is a very potent osteoclast inhibitor.The main aim of this study was to assess the effect of small β-CPP fractions(<1 wt%)on the in vitro osteoclastic resorption of β-TCP.A minor aim was to examine the effect of β-CPP and HA impurities on the physico-chemical properties of β-TCP powders and sintered cylinders.Twenty-six batches of β-TCP powder were produced with a Ca/P molar ratio varying between 1.440 and 1.550.Fifteen were further processed to obtain dense and polished β-TCP cylinders.Finally,six of them,with a Ca/P molar ratio varying between 1.496(1 wt% β-CPP)and 1.502(1 wt% HA),were incubated in the presence of osteoclasts.Resorption was quantified by white-light interferometry.Osteoclastic resorption was significantly inhibited by β-CPP fraction in a linear manner.The presence of 1% β-CPP reduced β-TCP resorption by 40%,which underlines the importance of controllingβ-CPP content when assessing β-TCP biological performance.

钛合金钙磷涂层电沉积技术研究进展

钛合金表面电沉积钙磷涂层技术具有处理温度低、组织结构易控和经济高效等优势,在保持植体优良机械性能的同时提高生物活性,有望替代等离子喷涂技术。为了促进钛合金表面电沉积钙磷涂层技术的临床转化,首先简述钛合金表面电沉积钙磷涂层机理,然后详述近年来在电解液参数(钙磷比、添加剂、p H值和气氛)、外场条件(电场、温度、磁场、超声波)和沉积时间对钛合金表面电沉积钙磷涂层影响的研究进展。其中,钙磷比改变电解液中钙源和磷源离子的临界浓度;p H值调节电解液中磷源离子的存在形式,直接影响涂层的物相种类;添加剂通过与钙源、磷源、溶剂或沉积晶体发生静电吸引、配位或特征吸附等作用,能够进一步调控涂层的种类和形态;控制气氛可有效防止空气中CO_(2)对涂层物相产生影响;进一步通过电场、温度、磁场、超声波和沉积时间的调控,可以优化涂层的结构形态和性能。最后,阐述了钛合金表面电沉积钙磷涂层技术的现存问题,并对其未来发展方向做了展望。

仿生再矿化治疗在牙釉质早期脱矿的作用及机制

背景:随着饮食改善和生活水平提高,酸性饮食和正畸治疗等成为导致牙釉质表面脱矿的主要原因。作为牙齿龋坏的第一步,牙釉质脱矿应被积极干预,机械磨除损伤较大且不符合微创医学理念,仿生再矿化是目前应对牙釉质脱矿的最佳方式。目的:通过对牙釉质早期脱矿的仿生再矿化治疗机制、应用方式及研究进展进行综述,为进一步攻克仿生再矿化热点难题提供思路。方法:以“Enamel demineralization,Biomimetic remineralization,amelogenin,Amorphous calcium phosphate”等作为英文关键词在PubMed数据库检索,以“釉质脱矿,仿生再矿化,釉原蛋白”等关键词在中国知网数据库进行检索,通过筛选最终共得到72篇文献进行综述分析。结果与结论:①目前针对釉质脱矿有药物治疗如含氟制剂等、激光治疗、树脂渗透、再矿化治疗等治疗方式,仿生再矿化是目前牙釉质早期脱矿最理想的修复方式。②狭义的釉质再矿化指早期釉质脱矿后内部的矿物质再沉积,广义的釉质再矿化包括釉质表面和内部两方面的矿化沉积。③临床仿生再矿化试剂多以釉原蛋白、非釉原蛋白、釉原蛋白肽、酪蛋白磷酸肽-不定形磷酸钙复合物等为主要成分。蛋白及肽类材料优势在于符合生理机制,可通过诱导定向生成高强度再矿化材料,劣势在于制作工艺相对复杂,成本较高;不定形磷酸钙复合物再矿化效果好,但需与其他材料结合使用以发挥作用;其他磷酸钙材料便于携带、有利美观,但易导致牙石形成。④未来研究应着重于以下几个方面:增加随机对照试验数据和临床结果,明确各个方式的适应证;发掘更多仿生再矿化方法,寻找合适替代材料;寻找合理的材料结合方式,以使其优缺点互补;加强临床应用便携性,以增加日常使用频率,使短期实验结论获得长期临床数据支持。