Bioactive Bone Cement Based on CaO─SiO2─P2O5 Glass

A CaO─SiO₂─P₂O₅─CaF₂ glass powder hardened within 4 min when mixed with an ammonium phosphate solution to form CaNH₄PO₄·H₂O. After it had soaked in a simulated body fluid for 3 d, forming hydroxyapatite, the cement showed a compressive strength of 80 MPa. Implanted into a rat tibia, the mixed paste formed a tight chemical bond to the living bone within 4 weeks. Such a bioactive cement could be useful not only for fixing various kinds of implants to the surrounding bones but also, by itself, as a bone filler.     

Potential of a sensitive uric acid biosensor fabricated using hydroxyapatite nanowire/reduced graphene oxide/gold nanoparticle

In this study, a ternary nanocomposite consisting of gold nanoparticles (AuNPs), hydroxyapatite (HAP) nanowires, and reduced graphene oxide (rGO) is synthesized by a simple one‐step hydrothermal method, which is used to modify glassy carbon electrode (GCE) for detecting uric acid. The nanocomposite is characterized through various methods such as scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. Electrochemical measurements of the modified GCE are performed in a conventional three‐electrode system. Experimental results show that the obtained HAP nanowire and rGO are mixed homogeneously, and the AuNPs are deposited into this matrix. The GCE modified by the nanocomposites have superior electrocatalytic activities for uric acid. The peak current intensities of UAO (uricase)/HAP‐rGO/AuNPs sensing system linearly increase as the uric acid concentration increases substantially in a range of 1.95 × 10^?5 to 6.0 × 10^?3 M (R² = .9943), with a detection limit of 3.9 × 10^?6 M (S/N = 3) and analytical sensitivity of 13.86 mA/M. The biosensor performs well in determining uric acid concentration in human urine samples.     

Characterization of thermal sprayed hydroxyapatite powders and coatings

Calcium phosphate materials such as hydroxyapatite (HA) have biocompatible properties that can promote osteogenesis or new bone formation. Thermal spraying is an economical and effective process for coating the hydroxyapatite onto metal. It has been reported that plasma spraying changes the degree of crystallinity as well as the phase composition of the HA. This article reports the preparation and characterization of HA powders and coatings by two thermal spray processes (plasma and combustion flame) and suggests that the state of the starting powder adversely affects the coating characteristics. The raw HA powders are synthesized through a chemical reaction involving calcium hydroxide and orthophosphoric acid. Phase analysis using an X- ray diffractometer revealed that the synthesized powder consists of predominantly the HA phase. Calcined and crushed HA powders of various size ranges were fed into the plasma jet to produce HA coatings on metallic substrates. In addition, some HA powders were sprayed into distilled water by plasma spraying and combustion flame spraying to study powder melting characteristics. Other samples were plasma sprayed onto a solid rotating target to study atomization and impact behavior. The morphology of the rapidly solidified powders and thermal sprayed coatings were examined by scanning electron microscopy (SEM). An X- ray sedimentation particle size analyzer, laser diffraction particle size analyzer, and image analyzer performed the particle size analysis. Preliminary results indicate that particle cohesion, size range, and thermal treatment in the plasma affect the phase and structure of the as- sprayed coating, and some post- spray treatment may be necessary to produce a dense and adherent coating with the desired biocompatible properties.     

溶液钙浓度和水热合成条件对微弧氧化TiO2／羟基磷灰石复合膜层形貌和组成的影响

钛在含钙磷的溶液中微弧氧化，表面形成含有钙磷元素的，均匀多孔的氧化膜层，水热合成后转化为含羟基磷灰石晶体的复合氧化膜。研究表明：钙离子浓度未使膜层的形貌和相组成发生明显变化；仅在较低的浓度下增加溶液Ca^2 的浓度，膜层中Ca，P元素的相对含量和Ca／P比都会增加；在不同的水热温度和溶液钙浓度下，得到的羟基磷灰石具有不同的晶体形貌，相对含量和Ca／P比；缩短恒温时间可以使HA晶粒细化。这为优化生物医用钛表面TiO2／羟基磷灰石复合膜层的成分和形貌提供了依据。     

Formation and Properties of Hydroxyapatite–Calcium Poly(vinyl phosphonate) Composites

Ceramic–polymer composites composed of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) and calcium poly(vinyl phosphonate) salt were prepared by warm-pressing powder mixtures of tetracalcium phosphate (Ca₄(PO₄)₂O, TetCP) and poly(vinyl phosphonic acid) (PVPA) at a weight ratio of 3.5:1. The effects of temperature (to 300°C), pressure (to 690 kpsi), or compaction time (to 1 h) on the extent of conversion were studied using X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy coupled with energy dispersive spectroscopy. The conversion of TetCP to HAp and formation of the calcium poly(vinyl phosphonate) salt was enhanced at higher temperature, pressure, and/or longer compaction time. Mechanical property determinations showed both the tensile strengths and elastic moduli continuously increase with increasing temperature, pressure, and compaction time. However, the glass transition temperature values of the composites were only minimally higher than that of the unreacted polymer.     

Conversion of the Echinoderm Mellita eduardobarrosoi Calcite Skeleton into Porous Hydroxyapatite by Treatment with Phosphated Boiling Solutions

The influence of the boiling solution technique (a nonhydrothermal wet treatment) in the formation of hydroxyapatite (HA) from a novel source, an echinoderm known as Mellita eduardobarrosoi, whose skeleton contains calcite as an inorganic constituent, was investigated. The experimental plan explores the conversion using a batch boiling system composed of KH₂PO₄ + KOH aqueous solutions at initial pH's of 8, 9, 10, 11, and 12, where granules of skeleton were dispersed to yield PO₄/CaCO₃ ratios of 1.0, 1.5, and 2.0. Chemical and X-ray diffraction analysis of the resulting material showed that the conversion of calcite by this technique is almost always higher than 70%, pH's 10 and 11 yielding the highest conversion. Depending on the operating conditions, the obtained material is a mixture of the original calcite and HA of varying stoichiometry and composition. Nevertheless, the interconnected porosity is preserved.     

离子束溅射沉积羟基磷灰石涂层钛种植体材料的制备和表征

采用Ａｒ＾＋离子束溅射沉积技术和钛基体上沉积羟基磷灰石薄膜涂层,Ａｒ＾＋离子束的能量分别为０．９ｋｅＶ、１．２ｋｅＶ和１．５ｋｅＶ。利用Ｘ射线衍射（ＸＲＤ）、扫描电（ＳＥＭ０、透射电镜（ＴＥＭ）和红外光谱（ＦＴＩＲ）等检测方法,对制备的羟基磷灰石薄膜涂层进行了表征。Ｘ射线衍射和透射电结果表明该薄膜涂层为非晶态;红外光谱中无羟基（ＯＨ）特征峰存在,ＣＯ３根吸收峰的出现说明制备过程中会引入ＣＯ３根;扫     

生物活性梯度涂层中羟基磷灰石的相转变与结构稳定性

重点研究了生物活性梯度涂层中羟基磷灰石高温结构稳定性。探讨了羟基磷灰石在喷涂和热处理过程中的相变化,对比研究了不同热处理条件对羟基磷灰石晶体稳定性和羟基恢复的影响。发现经等离子喷涂后的生物活性梯度涂层中的羟基磷灰石结晶程度明显降低,并出现β－ＴＣＰ杂相。羟基磷灰石晶体中的羟基已完全分解脱落。适当条件的热处理可使喷涂涂层中的磷酸三钙转变为羟基磷灰石,晶体中的羟基可大部分恢复,其中大气热处理比真空热处     

Effects of power level on characteristics of vacuum plasma sprayed hydroxyapatite coating

In this study, hydroxyapatite coatings were obtained with a vacuum plasma spray system at different power levels that were achieved by altering the plasma current and voltage. The effects of spray power level on coating characteristics were investigated. X-ray diffraction was used to identify the crystallinities of as-sprayed coatings, Electron Probe Microanalysis was employed to detect the surface chemical composition of as-sprayed coatings and Scanning Electron Microscopy revealed the microstructure. The results indicated that spray power greatly affected the crystallinity, chemical composition, and microstructure of as-sprayed hydroxyapatite coatings, which were linked to the melting state of hydroxyapatite powder. Presently at School of Materials Science and Engineering, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030, Republic of China.     

Thermal spraying of functionally graded calcium phosphate coatings for biomedical implants

Biomedical requirements in a prosthesis are often complex and diverse in nature. Biomaterials for implants have to display a wide range of adaptability to suit the various stages of the bio-integration process of any foreign material into the human body. Often, a combination of materials is needed. The preparation of a functionally graded bioceramic coating composed of essentially calcium phosphate compounds is explored. The coating is graded in accordance to adhesive strength, bioactivity, and bioresorbability. The bond coat on the Ti-6Al-4V stub is deposited with a particle range of the hydroxyapatite (HA) that will provide a high adhesive strength and bioactivity but have poor bioresorption properties. The top coat, however, is composed of predominantly α-tricalcium phosphate (α-TCP) that is highly bioresorbable. This arrangement has the propensity of allowing accelerated bio-integration of the coating by the body tissues as the top layer is rapidly resorbed, leaving the more bioactive intermediate layer to facilitate the much needed bioactive properties for proper osteoconduction. The processing steps and problems are highlighted, as well as the results of post-spray heat treatment.