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...     

乳液模板法制备聚酰亚胺中空微球及其形貌调控EI北大核心CSCD

以聚酰胺酸(PAA)为前驱体、甲基硅油(SO)为油相、乙醇和水作为沉淀剂,采用乳液模板法制备了聚酰亚胺(PI)中空微球。重点研究了沉淀剂中乙醇的比例、PAA溶液的固含量及PAA溶液/SO体积比对微球粒径和形貌的影响;采用光学显微镜、扫描电镜、红外光谱和热重分析仪对微球的形成过程、粒径和形貌、化学结构和热稳定性进行了表征。当沉淀剂中乙醇/水体积比为1:1、PAA溶液固含量为6%、PAA溶液/SO体积比为1:1时,PI微球的粒径为4.75μm。制备出的PI中空微球均具有较好的热稳定性,其起始热分解温度为442℃。     

水凝胶模板制备纳米TiO2及微流控合成TiO2微球

以聚丙烯酰胺丙烯酸和聚乙二醇/聚丙烯酸两种水凝胶作为模板, 丙烯酸做抑制剂合成纳米颗粒。水凝胶的缓慢吸水和网络结构, 减缓了钛酸四丁酯的水解速率, 并抑制TiO₂的颗粒长大, 制备出的TiO₂纳米粉粒径分布窄, 且为锐钛矿相结构。对比研究发现, 聚乙二醇/聚丙烯酸水凝胶的吸水膨胀率更小, 前驱体溶液的稳定性更高。选用聚乙二醇/聚丙烯酸前驱体溶液, 采用微流控技术制备TiO₂微球, 制备出的微球具有球形度好、单分散的优点, 焙烧后TiO₂的晶体结构为锐钛矿。     

SrMoO4粉体的化学溶液沉积制备及其发光性能研究

采用化学溶液沉积技术,用廉价的无机盐作为初始原料、常见的有机试剂为溶剂,制备了晶相单一且结晶良好的钼酸锶粉体;借助XRD、SEM和荧光分光光度计,对钼酸锶粉体的晶相、形貌、粒径分布和室温光致发光性能进行了表征.结果表明,所制备的钼酸锶粉体具有单一的四方相;粉体晶粒发育饱满、晶界清晰,晶粒呈现不规则的球状,尺寸在纳米-微...     

微乳液法制备球形氧化铝粉体的研究

用十六烷基三甲基溴化铵／正丁醇／环己烷／盐水反相微乳液体系制备出了纳米级不同粒径的球形氧化铝粉体,运用TG—DSC、SEM、XRD等手段对氧化铝及其前驱体进行表征,结果表明,通过改变水与表面活性剂的摩尔比（ω）,可实现球形纳米氧化铝粉体粒径的可控操作,并且具有分布均匀、分散性好和无团聚的特征。     

W/O微乳液制备纳米羟基磷灰石的影响因素研究

W/O微乳液制备的纳米羟基磷灰石粉体具有颗粒细小、团聚度低、分散性好、表面活性高等优点。综述了W/O微乳液制备纳米羟基磷灰石的原理;重点论述了影响粉体粒径和形貌的水油比、表面活性剂与助表面活性剂类型、前驱物浓度、反应温度等因素;并初步展望了该领域的研究发展趋势。     

超临界CO2抗溶剂法制备聚乳酸药物缓释微球

以L-聚乳酸为模型体系,超临界CO2为抗溶剂,采用超临界流体抗溶剂法制备聚乳酸微球.考察了压力、温度、溶液浓度、溶液流速、二氯甲烷-丙酮混合溶剂、聚合物分子量等参数对制备微球的形态、粒径及其分布的影响.结果表明,改变工艺参数,可在一定范围内调控微球粒径,所制微球平均粒径0.67～6.64μm,溶液浓度及其流速为主要影响因素;实验条件一定时,采用二氯甲烷-丙酮混合溶剂及强制分散溶液法制备得较小粒径微球.释放度实验结果表明,微球按一级释放方程释药,具缓释效果.     

化学沉淀法制备纳米氧化铝过程中的防团聚研究

分别以无水乙醇、去离子水为溶剂,以NH3·H2O、NH4HCO3为沉淀剂,采用化学沉淀法制备了纳米Al2O3粉体.利用TEM、XRD、FT-IR和激光粒度仪研究了溶剂、沉淀剂、浓度、前驱体等因素对纳米Al2O3粉体制备过程中的团聚程度的影响.结果表明:当NH4HCO3和Al(NO3)3水溶液浓度分别为3.0mol/L和0.3mol/L时,借助超声分散和微波干燥,得到的纳米Al2O3粉体粒度均匀、分散良好,1100℃煅烧所得粉体平均粒径为20nm.     

空心球羟基磷灰石等离子喷涂粉体的制备

羟基磷灰石等离子喷涂粉体被广泛用于等离子喷涂方法制备的骨及牙等医用种植体表面的生物活性涂层产品中,研制高性能的羟基磷灰石喷涂粉体对提高等离子喷涂羟基磷灰石生物活性涂层的使用性能有着重要意义.本研究采用水热、喷雾造粒、等离子球化及空心化等方法制备出一种新型空心球羟基磷灰石喷涂粉体.扫描电镜照片显示该粉体外观主要呈规则球形,平均粒径约为80.4μm,内部为空心结构,空心部分呈球状位于粉体中心,其平均壳壁厚度约为13.3μm.另外,本工作探讨了团聚结构羟基磷灰石粉体在等离子焰流中的空心化过程,认为粉体的初始孔隙率、粉体在焰流中的熔化程度、熔滴内部的气密性是影响空心化效果的主要因素.最后,通过等离子喷涂方法制备了团聚结构和空心球结构两种羟基磷灰石粉体涂层,结果表明:空心球结构羟基磷灰石粉体涂层的致密性及结合强度均优于团聚结构羟基磷灰石粉体涂层.     

PLLA/HA复合微球的制备

采用了一种新的微球制备方法液滴-冷凝法,以左旋聚乳酸[Poly(L-lactic-acid),PLLA]和羟基磷灰石(Hydroxyaptite,HA)为原料制备了复合微球。采用正交试验,以复合微球的粒径、球形度、成球率和孔隙率为考察指标,研究了PLLA溶液浓度、PLLA/HA质量比及冷凝液的温度梯度对复合微球成型和性能的影响,应用扫描电镜(SEM)对聚乳酸微球的微观形貌、孔隙结构进行了观察和表征。研究结果表明,应用该工艺制备的微球粒径均一,球径可控,其表面和内部都存在丰富的微孔,且孔间互相贯通。当采用较低浓度的PLLA溶液和适中的冷凝液温度梯度时,复合微球的各项指标均较好。该微球材料有望在骨缺损填充等领域得到应用。     

The control of paracetamol particle size and surface morphology through crystallisation in a spray dryer

The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed.     

Spray Dried Polylactide Microsphere Preparation: Influence of the Technological Parameters

Spray drying technique has been widely used in the pharmaceutical technological field with different applications. Recently it has been also successfully employed in the preparation of microparticulate drug delivery systems. The structure of the microparticles obtained is different according whether the drug is dispersed or dissolved in the polymeric solution to be spray dried.

Microcapsules are obtained by spraying a drug suspension in a solution of the polymeric coating, while polymeric matrices (microspheres), in which the drug is embedded, are obtained by spraying a solution of the drug and of the polymer.

The aim of this work is the investigation of several technological parameters that can affect the preparation and therefore the characteristics of the microparticles obtained by spray drying method. The effect of the inlet/outlet temperatures, spray rate of feed and of concentration of the starting polymeric solution on the characteristics of diazepam loaded poly-D, L-lactide microparticles are studied and evaluated with respect to yield of production, shape, size, and in vitro drug release behaviours.     

Investigations on Factors Affecting Chitosan for Dissolution Enhancement of Oxcarbazepine by Spray Dried Microcrystal Formulation With an Experimental Design Approach

In the present work effect of chitosan on microcrystal formulation for dissolution enhancement of oxcarbazepine using controlled crystallization technique coupled with spray drying was explored. The work was extended for exploration of simplified approach for stable particle size reduction. The study was performed with an experimental design approach i. e. a fractional factorial design of resolution 5 (with all 2 factor interaction) for the screening of predefined independent variables drug concentration, chitosan concentration, feed rate, inlet temperature and percent aspiration for spray drying. Whereas percent drug dissolved, wettability time, flowability in terms of angle of repose and particle size were designated as response variables. Resultant models were analyzed using multiple linear regression analysis, which generated equation to plot response surface curves along with desirability function. Results showed that chitosan concentration had significant effect on dissolution enhancement of oxcarbazepine at a level of 2% w/v. Increase in drug concentration showed decreased dissolution rate however on particle size it did not show statistically significant effect. Topographical characterization was carried out by SEM which showed that feed rate, percent aspiration and inlet temperature had significant effect on particle morphology. For deriving optimized formulation results were analyzed using desirability function for the maximum percent drug dissolved and least drug polymer matrix particle size. DSC studies showed that drug was molecularly associated with chitosan matrix or particles.     

Investigations on factors affecting chitosan for dissolution enhancement of oxcarbazepine by spray dried microcrystal formulation with an experimental design approach

In the present work effect of chitosan on microcrystal formulation for dissolution enhancement of oxcarbazepine using controlled crystallization technique coupled with spray drying was explored. The work was extended for exploration of simplified approach for stable particle size reduction. The study was performed with an experimental design approach i. e. a fractional factorial design of resolution 5 (with all 2 factor interaction) for the screening of predefined independent variables drug concentration, chitosan concentration, feed rate, inlet temperature and percent aspiration for spray drying. Whereas percent drug dissolved, wettability time, flowability in terms of angle of repose and particle size were designated as response variables. Resultant models were analyzed using multiple linear regression analysis, which generated equation to plot response surface curves along with desirability function. Results showed that chitosan concentration had significant effect on dissolution enhancement of oxcarbazepine at a level of 2% w/v. Increase in drug concentration showed decreased dissolution rate however on particle size it did not show statistically significant effect. Topographical characterization was carried out by SEM which showed that feed rate, percent aspiration and inlet temperature had significant effect on particle morphology. For deriving optimized formulation results were analyzed using desirability function for the maximum percent drug dissolved and least drug polymer matrix particle size. DSC studies showed that drug was molecularly associated with chitosan matrix or particles.     

Chemical processing of nanophase WC–Co composite powders

Abstract

The future development of advanced engineered materials for structural, electrical, magnetic, catalytic, and other applications will depend to an increasing extent on improved control of the size, distribution, and morphology of the constituent phases of the materials. In advanced materials systems, this development is in the direction of diminishing scale and increasing uniformity of the structure, extending into the nanoscale regime. The capabilities for synthesising novel nanophase structures are now becoming available in the laboratory and efforts are being made to scale up these processes to produce the quantities required for prototype development, field testing, and commercial applications. This paper addresses the scientific and technical issues relating to the chemical processing of nanophase WC–Co composite powders and the integration of the various processing steps into a new spray conversion processing technology. The new technology involves three coordinated steps: preparation and mixing of starting solutions; spray drying to form chemically homogeneous precursor powders; and fluid bed thermochemical conversion of the precursor powders to nanophase WC–Co powders. Both spray drying and fluid bed conversion are proven scalable technologies and offer the potential for producing bulk quantities of cemented carbide powders at lower manufacturing cost.

MST/1318     

Protein micro and nanoencapsulation within glycol-chitosan/Ca²+/alginate matrix by spray drying

Encapsulation of therapeutic peptides and proteins into polymeric micro and nanoparticulates has been proposed as a strategy to overcome limitations to oral protein administration. Particles having diameter less than 5 μm are able to be taken up by the M cells of Peyer's patches found in intestinal mucosa. Current formulation methodologies involve organic solvents and several time consuming steps. In this study, spray drying was investigated to produce protein loaded micro/nanoparticles, as it offers the potential for single step operation, producing dry active-loaded particles within the micro to nano-range. Spherical, smooth surfaced particles were produced from alginate/protein feed solutions. The effect of operational parameters on particle properties such as recovery, residual activity and particle size was studied using subtilisin as model protein. Particle recovery depended on the inlet temperature of the drying air, and mean particle size ranged from 2.2 to 4.5 μm, affected by the feed rate and the alginate concentration in the feed solution. Increase in alginate:protein ratio increased protein stability. Presence of 0.2?g trehalose/g particle increased the residual activity up to 90%. Glycol-chitosan-Ca(2+)alginate particles were produced in a single step operation, with resulting mean diameter of 3.5 μm. Particles showed fluorescein isothiocyanate labeled bovine serum albumin (BSA)-protein entrapment with increasing concentration toward the particle surface. Similar, limited release profiles of BSA, subtilisin and lysozyme were observed in gastric simulation, with ultimate full release of the proteins in gastrointestinal simulation.     

Flame spray synthesis of ZrO2 nano-particles using liquid precursors

This paper studies the feasibility of using flame spray to produce ZrO₂ nano-particles using a liquid precursor. The effects of varying precursor concentrations and ratio of diluting medium on the phase composition, size and morphology of ZrO₂ nano-particles are discussed. The morphology and size of the ZrO₂ nano-particles was very much dependent on the precursor concentration. The solvent ratio of H₂O:ethanol also played a part in determining the characteristics of the ZrO₂ nano-particles. The nano-particles had the best characteristics when the precursor concentration was low and ethanol (added as solvent) content was high. In particular, the best characteristics were obtained using precursor concentration of 0.25 M, H₂O:ethanol ratio of 0:1. The nano-particles had very small particle size (50 nm), relatively high specific surface area (28.6 m²/g) and high degree of crystallinity. However, particles synthesized tend to be agglomerated.     

颗粒级配对Si_(3)N_(4)w/Si_(3)N_(4)复合材料弯曲强度与介电性能的影响EI北大核心CSCD

为了获得一种弯曲和介电性能良好的氮化物陶瓷材料,本工作首先以氮化硅晶须(Si_(3)N_(4w))为原料,采用喷雾造粒工艺制备3种具有不同粒径分布的Si_(3)N_(4w)球形颗粒粉体,研究雾化盘转速对Si_(3)N_(4w)球形颗粒粉体粒径分布的影响。然后以喷雾造粒得到的Si_(3)N_(4w)球形颗粒为原料,采用干压法制备3种颗粒级配的Si_(3)N_(4w)预制体,研究颗粒级配Si_(3)N_(4w)预制体的孔径分布。采用化学气相渗透(CVI)和先驱体浸渍裂解(PIP)工艺在3种颗粒级配的Si_(3)N_(4w)预制体中进一步制备Si_(3)N_(4)基体,研究Si_(3)N_(4w)/Si_(3)N_(4)复合材料制备过程中的物相和微结构演变以及颗粒级配对Si_(3)N_(4w)/Si_(3)N_(4)复合材料的微结构、密度、弯曲强度和介电性能的影响。结果表明:3种颗粒级配的Si_(3)N_(4w)预制体均具有二级孔隙特征,其中小孔孔径均约为0.7μm,大孔孔径分别为45.2,30.1μm和21.3μm。在制备的3种颗粒级配的Si_(3)N_(4w)/Si_(3)N_(4)复合材料中,S13样品的颗粒级配效果最好,复合材料的弯曲强度达到81.59 MPa。此外,该样品的介电常数和介电损耗分别为5.08和0.018。良好的弯曲强度和介电性能表明制备的Si_(3)N_(4w)/Si_(3)N_(4)复合材料有望应用于导弹天线罩领域。     

喷雾干燥YPSZ纳米结构热喷涂粉末材料制备及表征

YPSZ纳米结构粉末材料的研究是热喷涂制备YPSZ纳米结构涂层必须首先进行研究的问题。本文采用喷雾干燥方法制备适合于热等离子体喷涂的YPSZ纳米结构粉末原料,同时采用等离子体喷涂制备涂层。利用扫描电子显微镜分析晶粒大小、颗粒形貌,X射线衍射分析相组成,对喷雾干燥后粉末进行热重-差热分析,测定粉末的松装密度、振实密度及流动性。结果表明制备的YPSZ粉末材料具有实心、流动性好、松装密度高、振实密度高、球形度高、单斜相少等优点,采用热等离子体喷涂沉积制备YPSZ纳米结构涂层。     

Preparation,characterization and dissolution behavior of artemisinin microparticles

In the present study, a modified 4-fluid nozzle spray drier was used to prepare microparticles of a poorly water soluble drug, artemisinin with the aim of improving its solubility. We also investigated the effect of process variables on the physical properties and dissolution rate of spray dried artemisinin. A full factorial experimentally designed study was performed to investigate the following spray drying variables: inlet temperature and feed concentration. The artemisinin powder and spray dried artemisinin microparticles were characterized by scanning electron microscopy (SEM), differential scanning calorimetric (DSC), X-ray diffraction (XRD) and dissolution. SEM study suggested that the inlet temperature and feed concentration impacted on the particle size of the spray dried particles. The crystallinity of spray dried particles was slightly decreased with increasing inlet temperature and concentration. The dissolution of spray dried particles was markedly improved as compared to commercial artemisinin. A dissolution surface-response model was used to elucidate the significant and direct relationships between drug feed concentration and inlet temperature on one hand and dissolution on the other hand. The best dissolution was found to be 117.00 ± 5.15 μg/mL at the drug feed concentration of 10 g/L and inlet temperature of 140 °C.