羟基磷灰石微球的制备及生物医学应用

羟基磷灰石微球具有独特的球形结构,形态规则,流动性好,比表面积大,表现出良好的生物相容性和生物活性,在生物医学领域有着广泛的应用.总结了羟基磷灰石微球的不同制备方法,如模板法、水热法、喷雾干燥法、微乳液法、沉淀法等,分析了不同制备方法对羟基磷灰石微球形貌、尺寸、结晶度等的影响,讨论了不同方法下羟基磷灰石微球形成机理.最...     

以碳酸钙为模板制备空心羟基磷灰石微球及其表征

以碳酸钙为模板和钙源,与磷酸氢二铵通过水热反应,制备出尺寸均匀、形态规则的空心羟基磷灰石微球。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)测试制备的样品,结果显示,制备的空心羟基磷灰石微球具有与碳酸钙微球模板相似的形貌,空心,尺寸均匀且形貌规则。并通过改变水热反应时间探索了羟基磷灰石微球的形成机理。此羟基磷灰石空心微球在生物医学领域具有较大的应用前景。     

非均相悬浮法制备多孔羟基磷灰石微球

为了获得具有吸附和生物学功能的多孔羟基磷灰石(HA)微球,以自制的纳米羟基磷灰石(HA)粉体为原料,用非均相悬浮法制备了HA/明胶微球,将微球在1 250℃下焙烧,成功制备了直径100~500μm的多孔HA微球.采用光学显微镜、SEM分析、XRD分析和BET氮吸附法研究了微球形貌、尺寸、物相组成、比表面积和孔径,测定了微球对水中F-离子的吸附性能.结果表明:微球具有良好球形形貌和相互贯通的纳米微孔;尺寸比较均匀,分散性良好;微球的主要结晶相为羟基磷灰石;BET表面积为1.867 0~2.089 5 m~2/g,孔径6.53~6.85 nm;对氟离子的平衡吸附容量为1.909~1.940 mg/g.通过控制m(HA)/m(明胶)比例、油温、搅拌速度和搅拌时间,可以在一定范围内控制微球直径和比表面积.     

微米级椭球形掺铕羟基磷灰石的发光和细胞毒性研究（英文）

利用碳酸钙模板和离子交换过程成功制备了一种新型掺铕羟基磷灰石微球。通过扫描电子显微镜(SEM)、X射线衍射(XRD)、感应耦合等离子体(ICP)、光致发光谱和体外MTT实验对微球物化性能、发光性和细胞毒性进行了表征。研究结果显示:掺铕羟基磷灰石微球呈椭球形,直径约为2.5μm,长度约为7μm,并具有刺猬状表面;在晶体结构上与纯相六方羟基磷灰石相同,具有高结晶性;铕离子成功进入羟基磷灰石晶相。同时,研究还表明该掺铕羟基磷灰石颗粒在紫外光激发下显示出红色荧光。光致发光光谱表明铕离子的~5D_0→~7F_(1-4)跃迁明显在光致发光活性中具有重要作用。体外细胞毒性实验结果显示:MC3T3-E1小鼠胚胎骨细胞在掺铕羟基磷灰石浸提液中能够持续增殖,没有细胞形态上的变化,并且细胞相对增值率计算结果表明该掺铕羟基磷灰石细胞毒性等级为1级。     

微米级椭球形掺铕羟基磷灰石的发光和细胞毒性研究

利用碳酸钙模板和离子交换过程成功制备了一种新型掺铕羟基磷灰石微球。通过扫描电子显微镜(SEM)、X射线衍射(XRD)、感应耦合等离子体(ICP)、光致发光谱和体外MTT实验对微球物化性能、发光性和细胞毒性进行了表征。研究结果显示: 掺铕羟基磷灰石微球呈椭球形, 直径约为2.5 μm, 长度约为7 μm, 并具有刺猬状表面; 在晶体结构上与纯相六方羟基磷灰石相同, 具有高结晶性; 铕离子成功进入羟基磷灰石晶相。同时, 研究还表明该掺铕羟基磷灰石颗粒在紫外光激发下显示出红色荧光。光致发光光谱表明铕离子的⁵D₀→⁷F_1-4跃迁明显在光致发光活性中具有重要作用。体外细胞毒性实验结果显示: MC3T3-E1小鼠胚胎骨细胞在掺铕羟基磷灰石浸提液中能够持续增殖, 没有细胞形态上的变化, 并且细胞相对增值率计算结果表明该掺铕羟基磷灰石细胞毒性等级为1级。     

羟基磷灰石生物陶瓷材料的制备及其新进展

羟基磷灰石常用作医用生物陶瓷材料。本文对羟基磷灰石及其复合生物陶瓷材料的各种制备方法进行了概述和评论．重点介绍了羟基磷灰石制备方法的新进展．并对未来的发展前景进行了分析。     

硼酸盐玻璃转化制备中空羟基磷灰石微球的研究

利用锂钙硼玻璃在磷酸盐溶液中的原位转化反应制备表面多孔且中空的羟基磷灰石(HAP)微球,通过XRD、SEM和BET对微球的物相组成、形貌和球壳的孔结构进行了表征.结果表明,微球具有良好的中空结构,600℃热处理后,微球球壳完全由HAP晶体组成,并显示出一定的机械强度(单个微球的抗压强度达到(2.1±0.6)MPa),球壳的气孔率为85%,平均孔径60nm.此外,对中空HAP微球的形成机理进行了分析.在磷酸盐溶液中,玻璃表面原位生成Ca-P-OH水化物,并在玻璃表面原来Ca2+的位置沉积下来,形成微球壳,而由Li+和B3+占据的位置,因其溶出形成孔隙.这样的结构将使之成为贮库型药物释放系统的载体.     

中空羟基磷灰石微球作为rhBMP-2缓释载体的研究

利用锂钙硼玻璃在磷酸盐溶液中的原位转化反应制备表面多孔且中空的羟基磷灰石(HA)微球, 将重组人骨形态发生蛋白2(rhBMP-2)装载到微球中, 研究了微球中rhBMP-2的体外缓释行为, 并采用体外细胞培养技术, 将载有rhBMP-2的微球和大鼠骨髓间充质干细胞(MSCs)一起培养, 测定细胞的碱性磷酸酶(ALP)活性, 并与单纯rhBMP-2的作用进行比较. 结果显示, 微球中所装载的rhBMP-2具有明显的缓释效应, 体外释放周期达到1000h以上, 该微球缓释系统具有一定的生物活性, 其作用效果优于单纯使用rhBMP-2.     

中空层状羟基磷灰石微球对溶菌酶的吸附与缓释研究

利用锂钙硼玻璃在磷酸盐溶液中的原位转化反应制备表面多孔且具有中空层状结构的羟基磷灰石(HA)微球,以溶菌酶为蛋白的药物模型,研究了中空层状结构的羟基磷灰石微球对溶菌酶的吸附及缓释特性,结果显示,中空微球对不同浓度的溶菌酶溶液,具有不同的吸附机理,当溶菌酶溶液的浓度低于0.8mg/mL时,溶菌酶的吸附主要发生在微球的外表面,符合Langmuir模型,释放速率较快,48h内基本释放完全;当溶菌酶溶液的浓度高于0.8mg/mL时,溶菌酶扩散进入微球内部及球壁的微孔中,使得吸附量显著增加,满足Henry吸附模型,溶菌酶的释放周期明显增加,可持续释放800h,微球对蛋白具有很好的缓释效果。     

原位纳米羟基磷灰石/壳聚糖复合载药微球的制备及释放性能研究

为应对骨缺损修复过程中的细菌感染问题,利用原位法制备了具有药物缓释功能的纳米羟基磷灰石(n-HA)和壳聚糖(CS)复合微球,并与纯CS载药微球和共混法n-HA/CS复合载药微球进行对比研究。利用相差显微镜和扫描电镜对微球进行形貌观察,结果显示原位法复合载药微球表面形态和球形度均较好。对载药微球的载药率、药物包封率和体外药物释放进行了测试和分析,结果表明原位法复合载药微球载药率和药物包封率最高,分别为(0.3907±0.0203)%和(7.4221±0.3858)%,并具有明显的缓释效果。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.