双重载药多层海藻酸盐-壳聚糖缓释微球的制备及体外释放

采用滴注法将海藻酸钠与钙离子交联,制成负载血管内皮生长因子(VEGF)的藻酸钙核心球,利用层层自组装技术在核心球的表面依次包覆壳聚糖、海藻酸和壳聚糖,壳聚糖中负载万古霉素(VAN),形成多药载药缓控体系.采用正交实验考察海藻酸钠浓度、钙离子浓度及壳聚糖浓度对VEGF和VAN的药物包封率和载药量的影响,优化了制备工艺.采用扫描电子显微镜观察多层微球的表面、截面形貌及粒径,采用傅里叶变换红外光谱检测海藻酸盐与壳聚糖的自组装情况,分别采用酶联免疫吸附(ELISA)双抗体夹心法和紫外分光光度法检测VEGF和VAN的包封率、载药量及体外释放情况.结果表明,海藻酸钠最优浓度为0.04g/mL,氯化钙最优浓度为0.15g/mL,壳聚糖最优浓度为0.01g/mL.微球光滑圆整,均质实心,直径900~1100μm,VEGF的包封率达61.31%,VAN的包封率为3.48%.体外释放实验结果表明,VEGF缓释时间为15.5d,并出现2个释放高峰;VAN缓释时间为4.5d,释药情况平稳持续,无明显突释.双重载药多层包覆微球兼具控制感染和促进血管生成两种潜能,有望应用于组织工程骨的基础研究和临床实践.     

中空SiO_2纳米微球的制备与表征

在乙醇/氨水介质中,将SiO2包覆在聚乙烯吡咯烷酮(PVP)功能化的聚苯乙烯(PS)微粒表面,利用一步法得到了中空纳米二氧化硅微球;研究了影响中空纳米二氧化硅微球形成的主要因素,并探讨了中空纳米SiO2微球的可能形成机理.结果表明,在一定的反应时间下,当氨水用量为0.6 mL、温度为70℃时,可以获得空心结构的SiO2纳米微球;通过控制四乙基原硅酸盐(TEOS)的量可以调节微球的包覆层厚度.     

核-壳介孔SiO_2微球的超微结构及拉曼光谱分析

采用溶胶-凝胶法制备了核-壳介孔SiO2微球,分别利用透射电镜和拉曼光谱对该微球的超微结构进行了观察及光谱分析。结果表明:制备的核-壳介孔SiO2微球是由外表面孔径为7nm、厚度30nm的有序介孔SiO2壳层,包裹着核直径为200nm的实心SiO2微球所组成,介孔壳层具有较大的比表面积,具有良好的光谱性质。     

制备方法对模板法制备SiO_2中空微球形貌的影响

模板法是制备无机中空微球的重要方法之一.首先通过苯乙烯和甲基丙烯酸的无皂乳液聚合法制得表面含羧基、粒径为360nm的单分散聚苯乙烯(PSt)乳胶粒,并以此为模板,分别采用表面改性-前驱体水解法(PHC)和SiO2纳米颗粒层层自组装法(LBL),制备出了不同壳层厚度的PSt/SiO2核壳结构复合微球,然后经500℃煅烧4h,得到SiO2中空微球.利用透射电镜和扫描电镜对微球结构形态进行了表征.研究表明,首先利用γ-氨丙基三乙氧基硅烷(KH-550)对PSt模板微球进行表面改性、然后再在乙醇-水混合介质中进行原硅酸乙酯(TEOS)水解与缩合反应的PHC法,是制备PSt/SiO2核壳结构复合微球的简便方法,复合微球经煅烧可制得表面均匀、结构致密、壳层厚度和形貌可控的SiO2中空微球;而LBL法制备PSt/SiO2核壳结构复合微球的工艺复杂,煅烧后所得SiO2中空微球结构疏松,易于破碎.     

层层自组装芸香叶苷海藻酸钠/壳聚糖盐酸盐微球的制备及释药性研究

为了提高载药微球的成球性和机械性能,以搅拌共沉淀法制得的CaCO_3微球为吸附剂,采用离子交联法制备载芸香叶苷的海藻酸钙(ALG-Ca)模板凝胶,利用层层自组装技术(LBL)将带有相反电荷的海藻酸钠(ALG)和壳聚糖盐酸盐(CHI)逐层络合得到不同膜层的载芸香叶苷微球。通过FT-IR、SEM、溶胀实验和体外释药实验对载药微球的性能进行研究,结果表明,以CaCO_3微球为吸附剂可提高载药ALG-Ca/(CHI/ALG)3微球的机械性能和成球性,微球剖面边缘出现层层膜结构且膜层总厚度约为20.22μm,载芸香叶苷ALG-Ca/(CHI/ALG)n微球释药实验发现,在37℃、pH=1.2生理盐水和pH=6.8 PBS溶液的环境下,聚合物膜层数越多对芸香叶苷缓释能力越强。     

单分散PS/SiO_2纳米复合微球的制备与表征

采用一种简单和低成本的方法制备单分散SiO2包覆聚苯乙烯(PS)(PS/SiO2)核-壳型纳米复合微球.首先在聚乙烯吡咯烷酮(PVP)存在下制备了PS纳米微球,然后在NH4OH/乙醇溶液中通过溶胶-凝胶过程在PS微球表面包覆SiO2.PS纳米微球的制备在水介质中进行,无需使用共单体,使用的是常用的过硫酸钾自由基引发剂;包覆处理前不用进行溶剂交换或离心处理.研究了PVP,NH4OH和原硅酸乙酯(TEOS)的用量对PS/SiO2纳米复合微球尺寸和形态的影响.随着PVP用量增加,PS微球变小,因此得到较小的PS/SiO2纳米复合微球;NH4OH用量对SiO2包覆层的厚度没有影响,但对SiO2包覆层的表面形态有影响,随着NH4OH用量增加包覆层表面变得粗糙;随着TEOS溶液用量增加,生成的SiO2增加,其包覆层的厚度增加.     

海藻酸盐-壳聚糖复合微/纳米凝胶研究进展

综述了海藻酸盐-壳聚糖复合微/纳米凝胶研究进展.指出海藻酸盐与壳聚糖的生物相容性、黏附性和降解性良好,以其为原料制备微/纳米凝胶具有方法简便安全、对药物包载效果好等优点,且与常规尺寸凝胶相比分散性和透过性较好.两者复合制备微/纳米凝胶主要采用一步交联、两步交联、自组装等方法,与单一组分凝胶相比优势明显,在药物输送等领域具有良好的应用前景.     

聚合物模板微球表面电性对中空二氧化硅微球形貌的影响

分别以过硫酸钾和偶氮二异丁基脒盐酸盐为引发剂,以聚乙烯吡咯烷酮(PVP)为分散剂,在水中引发苯乙烯聚合制备了2种表面分别带负电性和正电性基团的聚苯乙烯(PS)模板微球.在氨水催化下,利用正硅酸乙酯的水解缩合,形成PS/SiO_2复合微球,去除模板后得到中空SiO_2微球,并对其进行FTIR、电子显微镜、TGA以及氮气吸附等分析表征.结果表明,PS模板微球表面的电性决定了OH-的分布,从而导致PS模板微球表面SiO_2壳层不同的形成机制.当以表面带负电的PS微球为模板时,可得到树莓状的中空SiO_2微球;而以表面带正电的PS微球为模板时,得到是表面光滑的,具有介孔结构的中空SiO_2微球.     

种子表面改性法制备核壳结构PSt/SiO_2复合微球

首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360nm的单分散聚苯乙烯(PSt)种子乳液,并以EtOH/H2O混合物为分散介质,利用γ-氨丙基三乙氧基硅烷(KH-550)在25℃下对PSt微球表面进行改性,得到了表面硅烷化并带有正电荷的改性PSt种子乳液,然后在碱性条件下加入原硅酸乙酯(TEOS)使其和微球进行共水解与共缩聚,制备出了核壳结构PSt/SiO2复合微球,并利用电镜对复合微球的结构形态进行了表征.研究表明,PSt种子乳液改性时体系的zeta电位随着KH-550用量的增加而升高,当KH-550用量为PSt种子重量的1/3时,体系的zeta电位从原来的-34.5mV升高到了38mV,达到对PSt微球表面改性的最佳值;在制备PSt/SiO2复合微球时,TEOS水解缩聚形成的SiO2包覆到改性微球上的量随着反应时间的延长而增加,反应24h时达到97.9%的最大值;随介质中水含量的增加,吸附到复合微球表面上的SiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比降低到60/28.5时,得到结构均一、壳层厚度为35nm的核壳结构PSt/SiO2复合微球。     

磁性SiO2/PSt中空复合微球的细乳液法制备及表征

采用双原位细乳液聚合工艺,将疏水改性的磁性纳米粒子(MNP)加入到细乳液反应体系的油相中,利用增长的聚合物和单体TEOS之间的相分离原理,实现了聚合物的生成和TEOS的水解缩合同步进行,一步获得了磁性SiO2/PSt中空复合微球.通过红外光谱(FTIR)、透射电镜(TEM)、热重差热分析(TGA/DSC)和振动磁强计(VSM)对中空复合微球进行了表征.结果表明,制备的SiO2/PSt中空复合微球的尺寸范围为300～600 nm,当加入磁性纳米粒子后,得到的磁性SiO2/PSt中空微球保持了原来的中空结构,中空复合微球内腔的大小可以通过改变单体TEOS的加入量来控制.SiO2/PSt中空微球对磁性纳米粒子的包封率达到了86%.磁性SiO2/PSt中空复合微球具有超顺磁性,饱和磁强度值为14.7 emu/g.     

柔软的球状和长方体状氧化硅中空结构的制备研究

采用自组装形成的芘纳米结构作为模板,成功地制备了柔软的球状和长方体状氧化硅中空结构.当不同量的芘在十六烷基三甲基溴化铵(CTAB)溶液中自组装时,产生的自组装结构展现出明显的从球状到长方体状的形貌变化.这些结构被用作氧化硅前驱体溶胶-凝胶反应的模板,获得了球状和长方体状氧化硅/芘复合结构.通过乙醇除去模板后,生成了柔软的球状(直径约为400nm)和长方体状(长为0.5—2.5μm)的氧化硅中空结构.这些结果展现了采用有机纳米结构作为模板来合成无机中空结构的优势:合成简便、结构多样以及结构形貌的灵活可控.     

三元添加剂水溶液体系制备CaCO3空心球

利用原位聚合方法, 通过加入一定量的引发剂使甲基丙烯酸原位聚合, 在三嵌段共聚物(P123)、聚甲基丙烯酸(PMAA)和十二烷基硫酸钠(SDS)的三元添加剂混合溶液体系中成功地制备了CaCO3空心球. 采用扫描电子显微镜(SEM)和X射线粉末衍射(XRD)对合成样品的形貌、结构进行了表征. 结果显示, 方解石CaCO3空心球直径约0.5-2 μm. 空心球壁由直径约25-35 nm的圆形粒子组成, 壁厚约100-300 nm. 利用核鄄壳机理解释了空心球结构的形成过程.     

Chemical‐Template Synthesis of Micro/Nanoscale Magnesium Silicate Hollow Spheres for Waste‐Water Treatment

Micro/nanoscale magnesium silicate hollow spheres were synthesized by using silica colloidal spheres as a chemical template in one pot. The hollow spherical structure, consisting of well‐separated nanoscale units, was microscale as a whole and could be easily handled in solution. The as‐synthesized magnesium silicate hollow spheres with large specific surface area showed availability for the removal of organic and heavy‐metal ions efficiently from waste water. Importantly, the micro/nanoscale magnesium silicate hollow spheres that had adsorbed organic pollutants could be regenerated by calcination and used repeatedly in pollutant removal. Magnesium silicate hollow spheres synthesized by a scaled‐up chemical template method may have potential applications in removing cationic dyes and heavy‐metal ions from waste water.     

Fabrication of spherical colloidal crystals using electrospray

We demonstrated the use of electrohydrodynamic atomization to prepare uniform-sized emulsion droplets in which equal spheres of silica or polystyrene were dispersed. The size of the emulsion droplets was easily controlled by the electric field strength and the flow rate, independently of the diameter of the nozzles. During the evaporation of solvent in the droplets, spherical colloidal crystals were formed by self-assembly of the monodisperse colloidal spheres. The diameter of the spherical colloidal crystals was in the range of 10-40 microm. Depending on the stability of colloidal particles, the morphology of the self-assembled structure was varied. In particular, silica spheres in ethanol droplets were self-assembled into compactly packed silica colloidal crystals in spherical shapes, whereas polystyrene latex spheres in toluene droplets self-assembled into spherical colloidal crystal shells with hollow cores. The silica colloidal assemblies reflected diffraction colors according to the three-dimensionally ordered arrangement of silica spheres.     

Preparation of CaCO_3 Hollow Spheres in an Aqueous Binary-additive System

CaCO3 hollow spheres were prepared easily in anion surfactants （sodium dodecylbenzenesulfonate （SDBS）） and aspartic （Asp） acid binary-additive system by using an easy rapid agitation method. The as-prepared products were characterized with scanning electron microscopy （SEM）, FT-IR and X-ray diffraction. The results suggested that the CaCO3 hollow spheres have diameters ranging from 1 to 2 μm, and their wall is constituted of many nano-particles. Moreover, the possible formation mechanism of the hollow spherical structure was proposed.     

Synthesis and utilization of monodisperse hollow polymeric particles in photonic crystals

We developed a process to fabricate 150-700 nm monodisperse polymer particles with 100-500 nm hollow cores. These hollow particles were fabricated via dispersion polymerization to synthesize a polymer shell around monodisperse SiO(2) particles. The SiO(2) cores were then removed by HF etching to produce monodisperse hollow polymeric particle shells. The hollow core size and the polymer shell thickness, can be easily varied over significant size ranges. These hollow polymeric particles are sufficiently monodisperse that upon centrifugation from ethanol they form well-ordered close-packed colloidal crystals that diffract light. After the surfaces are functionalized with sulfonates, these particles self-assemble into crystalline colloidal arrays in deionized water. This synthetic method can also be used to create monodisperse particles with complex and unusual morphologies. For example, we synthesized hollow particles containing two concentric-independent, spherical polymer shells, and hollow silica particles which contain a central spherical silica core. In addition, these hollow spheres can be used as template microreactors. For example, we were able to fabricate monodisperse polymer spheres containing high concentrations of magnetic nanospheres formed by direct precipitation within the hollow cores.     

Fabrication of superhydrophobic surfaces from binary colloidal assembly

In this work, superhydrophobic surfaces were derived from binary colloidal assemblies. CaCO(3)-loaded hydrogel spheres and silica or polystyrene ones were consecutively dip-coated on silicon wafers. The former assemblies were recruited as templates for the latter self-assembly. Due to the hydrophilicity difference between silicon wafers and CaCO(3)-loaded hydrogel spheres, the region selective localization of silica or polystyrene spheres leads to irregular binary structures with a hierarchical roughness. The subsequent modification with low surface energy molecules yields a superhydrophobic surface. The heating treatment may largely enhance the mechanical stability of the resulting binary structures, which allows regeneration of the surface superhydrophobicity, providing a good durability in practice.     

A bio-inspired approach to the synthesis of CaCO3 spherical assemblies in a soluble ternary-additive system

Two different soluble polymers, poly(ethylene glycol) (PEG) and poly(methacrylic acid) (PMAA), with individual functions were successfully employed in combination with a third additive, sodium dodecyl sulfate (SDS), in one system, and spherical assemblies (e.g., hollow spheres) with multiscale constructs of CaCO3 were obtained. The variation of polymer concentration drastically changed both the morphology and polymorph of the produced CaCO3 crystals due to the corresponding transformation of the micelle structure. This study suggests that noncovalent interaction and cooperation between soluble macromolecules play key roles in controlling the growth of biominerals. The results also suggest a novel and facile route toward biomimetic inorganic synthesis.     

Hydrothermal synthesis of hollow silica spheres under acidic conditions

It is well-known that silica can be etched in alkaline media or in a unique hydrofluoric acid (HF) solution, which is widely used to prepare various kinds of hollow nanostructures (including silica hollow structures) via silica-templating methods. In our experiments, we found that sto?ber silica spheres could be etched in generic acidic media in a well-controlled way under hydrothermal conditions, forming well-defined hollow/rattle-type silica spheres. Furthermore, some salts such as NaCl and Na(2)SO(4) were found to be favorable for the formation of hollow/rattle-type silica spheres.     

以手性两亲小分子自组装体为模板制备介孔二氧化硅空心球

合成了手性阳离子型两亲性小分子化合物,利用圆二色谱分析了其在水中形成的自组装体的结构;以该化合物的自组装体为模板,在正丙醇和氨水的混合溶剂中制备得到了介孔二氧化硅空心球;利用扫描电镜、透射电镜、X射线衍射仪以及氮气吸附-脱附试验装置分析了二氧化硅空心球的形貌及孔结构.结果表明,两亲性小分子在水中形成的自组装体呈现手性堆积;合成的介孔二氧化硅空心球的直径约为600~800nm,壁厚约为100~150nm,其孔道垂直于球的表面,孔径约为3.0nm,比表面积约为306m2·g-1.正丙醇作为模板控制二氧化硅空心球的空腔尺寸和形貌,而两亲性小分子的自组装体作为模板控制放射状孔道的形貌和尺寸.