羟基磷灰石/离子液体混合膜修饰电极的制备及其应用于水中痕量镉离子的高选择性测定

利用溴代十六烷基三甲基铵(CTAB)为模板, 合成制备了棒状羟基磷灰石颗粒, 并以SEM, XRD, IR等手段进行了表征. 用制备的羟基磷灰石与自制的离子液体([BMIM]PF6)充分混合涂覆在玻碳电极表面制备了羟基磷灰石/离子液体修饰电极, 研究了镉离子在该修饰电极上的富集和电化学行为. 结果发现, 羟基磷灰石对镉离子有较好的富集作用, 而离子液体则可以在开路条件下使镉离子还原为金属镉, 氧化扫描时可以得到镉的灵敏氧化溶出峰, 以此为基础建立了一种高选择性地测定痕量镉离子的新方法, 该方法可以较好地避免铅、汞、银等重金属离子的干扰, 对镉离子检出限可达2.0×10－8 mol•L－1, 在4.0×10－8～2.2×10－7 mol•L－1的浓度范围内, 氧化溶出峰电流与Cd(II)的浓度呈良好的线性关系. 该研究有望在环境检测和环境治理方面发挥重要作用.     

Nucleation of Hydroxyapatite on Silica-Gel: Experiments and Thermodynamic Explanation

Silica-gels prepared from ethanol, TEOS and water, using a hydrochloric acid as catalyst, were slowly dried and heated in air up to 900°C. Plate-like pieces of heat treated silica-gel were used for hydroxyapatite nucleation experiments in a simulated body fluid (SBF) medium since sol-gel processing gives the silica an active surface. The SBF was changed every 3 days.After 9 days in the SBF, hydroxyapatite was observed by SEM on the surface of the silica-gel samples. The presence of hydroxyapatite was confirmed by FTIR. Subsequent growth of hydroxyapatite was evaluated after 12 and 21 days total soaking time in SBF. A thermodynamic analysis was made in order to explain the nucleation and growth of the hydroxyapatite on the silica-gel.     

ESCA-Analysis of tin compounds on the surface of hydroxyapatite

The formation of tin compounds on the surface of hydroxyapatite, the main crystalline component of teeth, is discussed controversially. SnF₂ is used as an anticaries agent in toothpaste preparations. Pure hydroxyapatite (HAP) is treated with extracts of commercially available toothpastes containing tin fluoride and analyzed by electron spectroscopy (ESCA). Survey spectra and depth profiles are recorded. The chemical shifts measured for the HAP samples are compared with those of standard tin compounds. It is concluded that on the surface of hydroxyapatite a mixture of two-valent fluoro-phosphato compounds is formed. SnO is not found in the mixture.     

Cadmium removal from single- and multi-metal (Cd + Pb + Zn + Cu) solutions by sorption on hydroxyapatite

Heavy metal contamination of waters and soils is particularly dangerous to the living organisms. Different studies have demonstrated that hydroxyapatite has a high removal capacity for divalent heavy metal ions in contaminated waters and soils. The removal of Cd from aqueous solutions by hydroxyapatite was investigated in batch conditions at 25+/-2 degrees C. Cadmium was applied both as single- or multi-metal (Cd + Pb + Zn + Cu) systems with initial concentrations from 0 to 8 mmol L(-1). The adsorption capacity of hydroxyapatite in single-metal system ranged from 0.058 to 1.681 mmol of Cd/g of hydroxyapatite. In the multi-metal system competitive metal sorption reduced the removal capacity by 63-83% compared to the single-metal system. The sorption of Cd by hydroxyapatite follows the Langmuir model. Cadmium immobilization occurs through a two-step mechanism: rapid surface complexation followed by partial dissolution of hydroxyapatite and ion exchange with Ca resulting in the formation of a cadmium-containing hydroxyapatite.     

块状壳聚糖多孔支架内交替浸渍沉积磷灰石层

在聚合物支架内沉积羟基磷灰石涂层有望提高支架的生物活性和骨传导性. 本研究采用交替浸渍沉积法, 以块状壳聚糖(Cs)三维多孔支架为沉积模板, 在氯化钙溶液和磷酸氢二钠溶液中交替浸渍, 沉积了羟基磷灰石(HA)涂层. 应用XRD、FT-IR、SEM、孔隙率测试、焙烧法和压缩实验对沉积前后支架的组成、形貌、孔隙率、无机物沉积量以及压缩强度进行了表征. 研究结果表明, 支架上沉积物为低结晶度的碳酸羟基磷灰石, 沿c轴择优生长, 与天然骨中磷灰石类似. 扫描电镜照片显示, 磷灰石在支架孔壁上的沉积量呈梯度分布, 外部沉积量多于内部, 靠近支架表面孔隙部分堵塞, 但内部仍保持连通的孔隙结构. 经6次交替浸渍处理的支架, 孔隙率为94.0%, 羟基磷灰石沉积量达到总质量的13.5%, 压缩强度则由0.055 MPa提高到0.109 MPa.     

In situ mineralization of hydroxyapatite on poly(vinyl alcohol) monolithic scaffolds for tissue engineering

A poly(vinyl alcohol) (PVA)/hydroxyapatite (HAp) composite monolithic scaffold is prepared via thermally impacted non-solvent induced phase separation method, successively followed by an alternate soaking process. The morphology of the resulting composite monolith is observed by scanning electron microscopy (SEM). The formation of hydroxyapatite is confirmed by X-ray diffraction, SEM in combination with energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The effects of soaking cycle and soaking time upon the formation of hydroxyapatite on the monolith surface are systematically investigated. With the increase of soaking cycle and soaking time, the amount of the formed hydroxyapatite increases. As the soaking cycle increases, the water uptake of the composite monolith decreases. The PVA/HAp composite monolith greatly has a promising application as scaffold of bone tissue engineering.     

A comparison of the adsorption of saliva proteins and some typical proteins onto the surface of hydroxyapatite

Adsorption of protein from saliva on hydroxyapatite was compared with adsorption of several typical proteins with different electric charges, i.e. lysozyme, human serum albumin, β-lactoglobulin and ovalbumin. Adsorbed amounts of these proteins were determined and electrophoretic mobilities of protein-covered hydroxyapatite particles were measured, at different values for the adsorbed mass and, therefore, at various degrees of surface coverage. Also, adsorption kinetics were investigated by streaming potential measurements of a hydroxyapatite surface in contact with a protein solution, allowing monitoring of changes in the zeta-potential of the protein-covered hydroxyapatite surface in real time. The adsorbed amounts show that, as compared to most of the other proteins, the saliva proteins have remarkably low adsorption affinity. The measured values for the electrophoretic mobilities indicate that the positively charged proteins in the saliva mixture preferentially adsorb onto the negatively charged hydroxyapatite surface; this is most pronounced at low protein concentration in solution (i.e. at low coverage of the surface by the protein). Preferential uptake of the positively charged saliva proteins during the initial stages of the adsorption process is also concluded from the results of the kinetics experiments. Preferential adsorption of positive proteins is somewhat suppressed by the presence of Ca²⁺ ions in the medium. The results suggest that an acquired pellicle on a tooth in an oral environment contains a significant fraction of positively charged proteins. The positively charged proteins in the pellicle reduce the zeta-potential at the tooth surface to low values; consequently, electrostatic forces are expected to play only a minor role in the interaction with other components (e.g. bacterial cells).     

Phospholipid bilayer formation on hydroxyapatite sol-gel synthesized films

Lipid bilayers supported by porous biomaterials are being explored as models for cell membranes. Hydroxyapatite is a relevant material currently being used extensively for biomedical applications. In this study, hydroxyapatite films produced via a sol-gel chemistry route have been characterized and explored as a scaffolding material for lipid membranes. The hydroxyapatite has been characterized using XRD, SEM, and AFM, followed by vesicle-fusion of lipids characterized by fluorescence microscopy and fluorescence recovery after photobleaching (FRAP) to determine the diffusion coefficient of this system. The HA films produced in this work were found to produce slow lateral diffusion and, in the two-phase lipid systems, some domains were observed. The low lateral diffusion coefficients were believed to be a result of the large undulations present on the hydroxyapatite film surface.     

Apparent solubility distributions of hydroxyapatite and enamel apatite

Samples of human dental enamel and hydroxyapatite were equilibrated at 5 mg/40 ml for 9 days at 37 degrees C with acetate buffers adjusted to a range of saturations with respect to hydroxyapatite. Sigmoidal apparent solubility distributions, in which the fraction dissolved was plotted against--log(ion activity product for hydroxyapatite) (pIHA), were constructed. About 10% of the hydroxyapatite and 14% of the enamel was very soluble, dissolving even at pIHA 55. The apparent solubility distributions for both solids were invariant with pH (4.5, 5.0, 5.5), within experimental error, showing that solubility was controlled by a phase with the stoichiometry of hydroxyapatite, probably in the form of a surface layer or complex on the crystals, in agreement with other studies on carbonate-apatites and bone mineral. The pIHA at 50% dissolution was employed as an average value. The pIHA (50%) values for pooled data (58.76 for enamel and 60.17 for hydroxyapatite) were lower than the respective pIHA previously measured by conventional equilibration techniques. However, the average pIHA measured for enamel was higher than that obtained by the same technique in another study, possibly because of differences in specimen preparation and equilibration time. The possible implications of the findings for understanding the process of dental caries are discussed.     

Synthesis of Nano-hydroxyapatite via Microbial Method and Its Characterization

Nanoparticles of hydroxyapatite were successfully synthesized by microbial method at ambient temperature and pressure, using calcium chloride and specific substrate as reactants. The compositional and morphological properties of products of the syntheses were studied by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The characterization data obtained showed that the phase composition, functional groups, and surface morphology of samples obtained by microbial method were mainly similar to that by chemical precipitation method. The hydroxyapatite powder was shown to be nanometer-grade in size and sphere-like in shape.     

Influence of process parameters on the sol–gel synthesis of nano hydroxyapatite using various phosphorus precursors

Hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ has attracted widespread interest from both orthopedic and dental fields due to its excellent biocompatibility and tissue bioactivity properties. Since nanophase materials can mimic the dimensions of constituent components of natural tissues, the implants developed from nanophase material could serve as a successful alternative. However, the defects of hydroxyapatite ceramics, mainly brittleness and low fracture toughness, have been overcome by the use of nanophase hydroxyapatite coatings on the implant surfaces that integrate the good mechanical properties of metals and the bioactivity of hydroxyapatite. In the present investigation, Sol?Cgel hydroxyapatite was prepared from two different phosphorus precursors such as triethyl phosphate and phosphorus pentoxide respectively with calcium nitrate tetrahydrate as a calcium precursor. The effects of pH and liquid P³¹ Nuclear Magnetic Resonance spectroscopy for the solution aged at different periods were investigated and the synthesized hydroxyapatite powder was characterized by Transmission electron microscopy, X-ray Powder Diffraction, Fourier transform infrared spectroscopy and thermal analysis respectively. In order to fully understand the bioactivity of the synthesized materials, they were coated on 316L Stainless Steel implant surface by spin coating method at the spin speed of 2,000 Revolutions per minute. The effect of nanoparticles on the surface of 316L Stainless Steel implant was studied by adhesive strength measurements. The corrosion resistance property of the hydroxyapatite coatings was evaluated by electrochemical impedance analysis. From the results, it was observed that the hydroxyapatite coatings obtained from different precursors have very high resistance to corrosion with higher adhesive strength.     

Photoelectron spectroscopic studies of the formation of hydroxyapatite films on titanium pretreated with etidronic acid

X‐ray photoelectron spectroscopy in the core and valence band region was used to study the formation of hydroxyapatite films on the surface of titanium. The approach used achieves the adhesion of hydroxyapatite by the initial formation of a thin, mainly oxide‐free, etidronate film on the metal. In this approach, it was not possible to prepare hydroxyapatite films of any reasonable thickness on the titanium surface without prior treatment with etidronic acid. Because hydroxyapatite is a principal component of teeth and bones, it is likely that the coated metals will have desirable biocompatible properties. The hydroxyapatite film showed no changes when the film was exposed to air, water, and 1 m sodium chloride solution as representative components of the environment of the film in the human body. These films formed on titanium may find application in medical implants. The thin hydroxyapatite and etidronate film on the metal show differential charging effects that caused a doubling of some of the spectral features. Copyright © 2012 John Wiley & Sons, Ltd.     

聚醚醚酮复合材料表面生物活性涂层的制备与性能

以聚醚醚酮/钡玻璃粉(PEEK-BGF)复合材料为基体, 通过硅烷偶联剂, 在复合材料表面构建具有生物活性的纳米羟基磷灰石(nHA)和甲基丙烯酸酯基的光固化树脂复合涂层. 采用扫描电子显微镜(SEM)和X射线光电子能谱(XPS)分析了材料表面形貌和元素分布, 测试了涂层与复合材料之间的粘接强度. 通过检测大鼠成骨细胞总蛋白含量和碱性磷酸酶表达水平, 评价新型光固化纳米羟基磷灰石/聚甲基丙烯酸酯(nHA/PMMA)复合涂层的生物活性. 研究结果表明, nHA填充的光固化复合材料形成粗糙的表面, 随着nHA的填充量提高, 涂层表面生物学活性得到提高.     

Protein Adsorption onto Nanosized Hydroxyapatite Particles for Controlled Drug Release

Nanosized hydroxyapatite(nsHAp) was synthesized to examine its possibility as a controlled release carrier of protein. To achieve effective protein release from nanosized hydroxyapatite, the study of the adsorptive properties of protein on nsHAp and different influence parameters such as pH, calcium, and phosphate concentrations during the adsorption process is necessary. Ovalbumin(OVA) was selected as the model of growth factors. The results show that the amount of OVA adsorbed onto nsHAp in acetic buffer(pH=3.6) is more than that in acetic buffer(pH=5.6) because of the electric interaction. The amount of OVA adsorption in phosphate buffer solution(PBS) is smaller than that in acetic buffer because of surface complexation and surface hydroxylation. The presence of Ca2 dramatically increases the adsorbed amount of OVA in acetic buffer on maintaining the same pH. Meanwhile, the release kinetics of OVA adsorbed onto nsHAp(nsHAp-OVA) was also examined. The amount of released OVA in PBS(pH=5.6) was significantly smaller than that released in solution of pH=7.0. All the results suggest that nanosized hydroxyapatite particles could be successfully used as controlled released carrier of protein.     

Surface modifications of Nitinol for biomedical applications

Cathodic electrophoretic deposition (EPD) has been utilized for the fabrication of composite films for the surface modification of NiTi shape memory alloys (Nitinol). In the proposed method, chitosan (CH) was used as a matrix for the incorporation of other functional materials, such as heparin, hydroxyapatite and bioglass. Chitosan-heparin films were deposited from solutions of non-stoichiometric chitosan-heparin complexes. It was found that the addition of anionic heparin to the solutions of cationic chitosan resulted in a significant increase in the cathodic deposition rate. The thickness of the films prepared by this method varied in the range of 0.1-3 microm. The ability of the chitosan-heparin films to bind antithrombin, as measured by binding of (125)I-radiolabeled antithrombin, was much greater than that of pure chitosan films. Composite chitosan-hydroxyapatite films, with thickness of 1-30 microm, were obtained as monolayers or laminates, containing chitosan-hydroxyapatite layers, separated by layers of pure chitosan. The hydroxyapatite nanoparticles showed preferred orientation in the chitosan matrix with the c-axis parallel to the substrate surface. The films showed corrosion protection of the Nitinol substrates in Ringer's physiological solutions. The feasibility of the fabrication of composite films containing hydroxyapatite and bioglass in the chitosan matrix has been demonstrated. The method offers the advantages of room temperature processing. The deposition mechanisms and possible applications of the films are discussed.     

Grafting cyclodextrins to calcium phosphate ceramics for biomedical applications

The grafting of hydroxyapatite/beta-tricalcium phosphate with β-cyclodextrin was achieved using a two step reaction with (3-glycidyloxypropyl)trimethoxysilane as a linker. Firstly, the silane group was brought to react with the hydroxyl groups at the surface of the hydroxyapatite/beta-tricalcium phosphate and secondly, the epoxy group was brought to react with the β-cyclodextrin. The amount and distribution of covalently bound β-cyclodextrin were investigated by thermogravimetric analysis, colorimetric total sugar assay, fluorescence spectroscopy and confocal laser scanning microscopy. The concentration of grafted β-cyclodextrin was found to be approximately 3.5?μmol per gram of material corresponding to an almost complete surface coverage, when assuming a closed hexagonal packed monolayer.     

羟基磷灰石与牛血清白蛋白相互作用的原位红外光谱研究

应用原位(in situ)全反射红外光谱研究牛血清白蛋白在电化学法制备的羟基磷灰石表面的吸附和成键行为, 探索电化学法制备的HA生物材料/生物环境界面过程和生物相容性的微观本质.     

Hydroxyapatite coating on porous polyurethane facilitated by tetraethoxysilane

Biomimetic growth of calcium phosphate compounds on porous polyurethane (PU) treated with tetraethoxysilane (TEOS) and soaked in simulated body fluid (SBF) solution was studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), and Fourier transformed infrared spectroscopy–attenuated total reflectance (FTIR–ATR). Polyurethane was treated with TEOS in order to produce silanol groups which stimulated the growth of hydroxyapatite when immersed in SBF solution. Polyurethanes that were not treated with TEOS did not show calcium phosphate growth upon immersion in SBF solution. The Ca and P determined by EDAX and inductively coupled plasma spectroscopy (ICP) analysis revealed that the surface layer was not stoichiometric hydroxyapatite, but carbonated, containing hydroxyapatite with a Ca/P ratio of 1.5–1.6. This was confirmed by FTIR–ATR.     

Synthesis of hydroxyapatite crystals using amino acid-capped gold nanoparticles as a scaffold

Inorganic composites are of special interest for biomedical applications such as in dental and bone implants wherein the ability to modulate the morphology and size of the inorganic crystals is important. One interesting possibility to control the size of inorganic crystals is to grow them on nanoparticles. We report here the use of surface-modified gold nanoparticles as templates for the growth of hydroxyapatite crystals. Crystal growth is promoted by a monolayer of aspartic acid bound to the surface of the gold nanoparticles; the carboxylate ions in aspartic acid are excellent binging sites for Ca(2+) ions. Isothermal titration calorimetry studies of Ca(2+) ion binding with aspartic acid-capped gold nanoparticles indicates that the process is entropically driven and that screening of the negative charge by the metal ions leads to their aggregation. The aggregates of gold nanoparticles are believed to be responsible for assembly of the platelike hydroxyapatite crystals into quasi-spherical superstructures. Control experiments using uncapped gold nanoparticles and pure aspartic acid indicate that the amino acid bound to the nanogold surface plays a key role in inducing and directing hydroxyapatite crystal growth.     

Solid-state P-31 NMR study of the formation of hydroxyapatite in the presence of glutaric acid

We demonstrate that glutaric acid can be used to prepare nanorods of hydroxyapatite under hydrothermal condition at 100 degrees C with a Ca(2+):glutaric acid molar ratio of 1:4. Frequency-switched Lee-Goldburg irradiation is employed to obtain high-resolution (31)P{(1)H} correlation spectra of the reaction mixture at two different reaction periods, from which it is shown that octacalcium phosphate is the precursor phase of the final hydroxyapatite product. In addition, the spectra show that a substantial amount of water molecules is trapped between the glutaric acid and the hydroxyapatite surface, indicating that water molecules may play a prominent role in the noncovalent interaction of the glutaric acid and the HAp surface.