Surface treatment and biomimetic mineralization of porous microspheres fabricated by calcium gluconate-<Emphasis Type="Italic">g</Emphasis>-poly(D,L-lactide)

Porous hybrid microspheres were fabricated by the synthesized calcium gluconate-g-poly(D,L-lactide) (CG-g-PDLLA) composites. These hybrid microspheres were treated with an alkaline solution for different period of time to control the amount of generated carboxylate groups and remained CG on the surface. The microspheres were then incubated in a supersaturated simulated body fluid (1.5 SBF) solution for different time to investigate their biomimetic mineralization behavior. The depositions were found to have a fine cluster morphology, a similar crystal structure and chemical structure to natural hydroxyapatite, and a medium Ca/P of approximately 1.30. The effect of surface treating time on the structure and mineralization behavior of these microspheres has been discussed in detail. The results indicate that the nucleation and growth of apatite on the surface are influenced by the induced carboxylate groups and the remained CG. The hybrid CG-g-PDLLA microspheres have the potential as a novel alternative in bone tissue engineering.     

Hydrolysis and biomineralization of porous PLA microspheres and their influence on cell growth

Poly(lactic acid) (PLA) microspheres have great potential in bone tissue engineering. However, their applications have been limited by surface and bulk properties such as hydrophobicity, lack of cell recognition sites and acidic degradation products. Apatite is a mineral which can effectively promote the adhesion and growth of bone cells. In this study, the bonelike mineral, carbonate apatite, was successfully used to functionalize porous PLA microspheres by a biomimetic mineralization method. To improve apatite formation, porous PLA microspheres were first selectively hydrolyzed in NaOH solution to increase the density of polar anionic groups on the surface, and then immersed in simulated body fluid for biomineralization. The morphology, composition, and phase structure of bioactive mineral grown on the original and hydrolyzed PLA microspheres were analyzed and compared quantitatively. The results showed that the hydrolysis which took place on the PLA microspheres enhanced the nucleation and growth of apatite. MG-63 cells attached well and spread actively on the mineralized PLA microspheres, indicating their strong potential in bone tissue engineering.     

盐溶液调控海藻酸钙微球中的自由羧酸根及其对阿霉素的装载和释放行为研究

采用膜乳化-凝胶化法制备了粒径窄分布的海藻酸钙微球.用不同浓度的氯化钠溶液处理微球来调控微球中的自由羧酸根的含量.用原子吸收光谱和红外光谱表征了微球中钙、钠离子以及化学基团的变化,证明盐处理后海藻酸钙微球内发生了钠离子置换钙离子的过程,海藻酸中的羧酸根由螯合态转变为自由态.用盐处理后的微球吸附带正电荷的小分子抗癌药物阿霉素的能力大大提高,其中用浓度1.8%的氯化钠溶液处理后的微球载药量达到1310μg/mg,是未处理微球的10倍.负载药物的微球具有pH敏感的释放行为,在pH5.5的PBS溶液中的释放速率和释放量显著大于在pH 7.4的PBS溶液中.     

不同表面官能团和化学组成共聚物微球的表面生物矿化研究

采用具有不同共聚物组成和端基官能团的聚己内酯-b-聚乙二醇共聚物(PCL-b-PEG),通过双乳液溶剂挥发法制备了一系列具有不同表面性质的生物降解高分子微球.采用生物模拟矿化的方法以磷灰石修饰微球表面.进一步通过扫描电镜、热重分析仪、X-射线衍射仪和光电子能谱仪对微球表面磷灰石的形貌、含量、结构和组成进行了分析.研究了微球表面亲水性、粗糙度、官能团以及矿化时间对于磷灰石形成的影响.最终实验结果表明,随着共聚物中PEG含量增加,微球表面粗糙度和亲水性增加,因此微球表面磷灰石含量增加.同时微球表面官能团以及矿化时间的不同也会对磷灰石的形成和分布产生明显影响.     

Reparation of silica/poly(methacrylic acid)/poly(divinylbenzene-co-methacrylic acid) tri-layer microspheres and the corresponding hollow polymer microspheres with movable silica core

 Hollow poly(divinylbenzene-co-methacrylic acid) (P(DVB-co-MAA)) microspheres were prepared by the selective dissolution of the non-crosslinked poly(methacrylic acid) (PMAA) mid-layer in ethanol from the corresponding silica/PMAA/P(DVB-co-MAA) tri-layer hybrid microspheres, which were afforded by a three-stage reaction. Silica/PMAA core-shell hybrid microspheres were prepared by the second-stage distillation polymerization of methacrylic acid (MAA) via the capture of the oligomers and monomers with the aid of the vinyl groups on the surface of 3-(methacryloxy)propyl trimethoxysilane (MPS)-modified silica core, which was prepared by the Stöber hydrolysis as the first stage reaction. The tri-layer hybrid microspheres were synthesized by the third-stage distillation precipitation copolymerization of functional MAA monomer and divinylbenzene (DVB) crosslinker in presence of silica/PMAA particles as seeds, in which the efficient hydrogen-bonding interaction between the carboxylic acid groups played as a driving force for the construction of monodisperse hybrid microspheres with tri-layer structure. The morphology and the structure of silica core, silica/PMAA core-shell particles, the tri-layer hybrid microspheres and the corresponding hollow polymer microspheres with movable silica cores were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS).     

Simple method for preparation of porous polyimide film with an ordered surface based on in situ self-assembly of polyamic acid and silica microspheres

In this Article, we addressed a facile method for the fabrication of porous polyimide film with an ordered surface based on the solvent-evaporation-assisted in situ self-assembly of polyamic acid (PAA, precursor of polyimide) and silica microspheres during vacuum-drying of PAA/silica colloid solution. Hydroxyl groups on the surface of silica microspheres have strong hydrogen-bonding with PAA chains, which improve the dispersion of silica microspheres in PAA/DMF solution and further help the self-assembly of PAA/silica colloid solution via solvent evaporation. The approach is simple, neither the preparation of special template nor complex preparation process and precise control over condition is necessary. Furthermore, the method could be employed for mass production of ordered porous polyimide films, and by changing the content and size of silica microspheres, the pore size and porous structure of the porous polyimide films could be tunable. The wettability behavior of the as-prepared porous polyimide films is also studied; the ordered surface topography of the porous polyimide films could change the wettability from hydrophilicity to hydrophobicity.     

A new approach to mineralization of biocompatible hydrogel scaffolds: an efficient process toward 3-dimensional bonelike composites

As a first step toward the design and fabrication of biomimetic bonelike composite materials, we have developed a template-driven nucleation and mineral growth process for the high-affinity integration of hydroxyapatite with a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel scaffold. A mineralization technique was developed that exposes carboxylate groups on the surface of cross-linked pHEMA, promoting high-affinity nucleation and growth of calcium phosphate on the surface, along with extensive calcification of the hydrogel interior. Robust surface mineral layers a few microns thick were obtained. The same mineralization technique, when applied to a hydrogel that is less prone to surface hydrolysis, led to distinctly different mineralization patterns, in terms of both the extent of mineralization and the crystallinity of the apatite grown on the hydrogel surface. This template-driven mineralization technique provides an efficient approach toward bonelike composites with high mineral-hydrogel interfacial adhesion strength.     

Photoassisted decomposition of malonic acid on TiO2 studied by in situ attenuated total reflection infrared spectroscopy

The photoassisted mineralization, i.e., conversion to CO2 and water, of malonic acid over P25 TiO2 was investigated by in situ attenuated total reflection infrared (ATR-IR) spectroscopy in a small volume flow-through cell. Reassignment of the vibrational bands of adsorbed malonic acid, assisted by deuterium labeling, reveals two dissimilar carboxylate groups within the molecule. This indicates adsorption via both carboxylate groups, one in a bridging or bidentate and the other in monodentate coordination. During irradiation the coverage of malonic acid strongly decreases, and oxalate is observed on the surface in at least two different adsorption modes. The major oxalate species observed during irradiation is characterized by monodentate coordination of both carboxylate groups. In the dark, however, part of these species adopts another adsorption mode, possibly interacting only with one carboxylate group. During band gap illumination a large fraction of the surface is not covered by acid. Oxalate is a major intermediate in the mineralization of malonic acid. However, the observed transient kinetics of adsorbed malonic and oxalic acid indicates additional pathways not involving oxalate. The rate constant for oxalate decomposition is slightly larger than the one for oxalate formation from malonic acid. As the oxalate is desorbing slowly from the surface its concentration in the liquid phase is small, despite the fact that it is a major intermediate in the mineralization of malonic acid.     

核壳结构PAM-ZnS纳米杂化微球的制备研究

随着高新科技的发展,人们对材料的要求越来越高,纳米材料的研究和材料的杂化已成为材料发展的重点之一.近年来,有彬无机杂化材料因其具有可调的光、电、磁等特性而备受关注．有彬无机杂化材料的杂化尺度通常为纳米级,甚至小到分子水平,因而可实现不同组分性质结合于一体,并产生协同效应．纳米ZnS材料因具有热红外透明、荧光、磷光等特性已引起人们极大的兴趣,例如ZnS纳米颗粒量子点及其掺杂具有独特的光电性质,主要用于传感器和高分辨显示器．     

ZnO/PS core-shell hybrid microspheres prepared with miniemulsion polymerization

The hybrid microspheres of ZnO/PS with different core-shell structures were prepared in miniemulsion polymerization. 3-(trimethoxysilyl)propyl methacrylate (MPS) was used as a functional co-monomer to enhance the surface polarity of ZnO nanoparticles and to prevent water from quenching the luminescent properties of ZnO. The morphology of hybrid particles was examined with a transmission electron microscope. The luminescence spectra were measured using a Shimadzu RF-5301 PC spectrofluorimeter (Xe source) at room temperature. The crystallization structure of samples was characterized with a Rigaku wide-angle X-ray diffractometer. The chemical composition and structure of the ZnO colloids, MPS-modified ZnO colloids, and ZnO/PS hybrid microspheres were analyzed with IR.     

碳纳米管/壳聚糖复合微球的原位仿生矿化及表征

对碳纳米管(CNTs)进行酸化处理, 采用乳化交联法制备CNTs/壳聚糖(CS)复合微球, 在其表面诱导羟基磷灰石仿生合成, 研究了CNTs对复合微球仿生矿化的影响, 并与纯CS微球的仿生矿化进行了对比. 利用扫描电子显微镜(SEM)、 X射线衍射仪(XRD)、 溶胀率和含水率测试等考察了复合微球矿化前后的形貌特征、 物相结构及稳定性. 结果表明, 在相同时间下, CNTs/CS复合微球表面纳米羟基磷灰石的形成能力明显优于纯CS微球, 且形态稳定性更高. 细胞实验结果表明, 与MG63细胞共培养7 d时, 矿化复合微球细胞增殖明显.     

The synthesis of organo-soluble anatase nanocrystals from amorphous titania

Highly soluble anatase nanocrystals of 4 nm diameter have been prepared by the reaction of amorphous titania with trifluoroacetic acid. The solubility of the nanocrystals is a result of surface bound carboxylate groups, and enables the organic-inorganic hybrid material to be processed from solution to yield high quality coatings and thin-films.     

Structure controlling and adsorption application of polyethersulfone porous microspheres prepared via electrospraying

The focus of this work is to control the structure of electrosprayed polymer microspheres and then study the effect of different structures on the microspheres＇ adsorption properties. Scanning electron microscopy （SEM） coupled with image analysis software was employed to evaluate the size distributions and the structure of microspheres. According to the observation and analysis results, two types of polyethersulfone （PES） porous microspheres （perfect sphere-shaped and collapsed） were prepared via electrospraying technology by adjusting the solvent and polymer molecular weight. The porous PES microspheres can remove bisphenol A （BPA） from its aqueous solution effectively. Compared with collapsed microspheres, the rough microspheres had much higher specific surface area and better mobility in the BPA aqueous solution, so it showed a better adsorption capacity than that of collapsed microspheres. The solvent evaporation rate and the occurrence rate of phase separation significantly affect the structure and morphology of microspheres.     

具有核壳结构磁性复合微球的制备与表征

采用两步法制备了具有核壳结构的Fe3O4/P(MMA/DVB)(core)-P(St/GMA/DVB)(shell)磁性复合微球.首先,用改进的细乳液聚合制备了Fe3O4/P(MMA/DVB)微球;然后,加入总量不同的苯乙烯(St)、甲基丙烯酸缩水甘油酯(GMA)和二乙烯基苯(DVB),通过种子乳液聚合,制备了不同磁含量的核壳结构的磁性复合微球.分别用X-射线衍射(XRD)、高倍透射电镜(HR-TEM)、热重分析(TGA)、振动样品磁力计(VSM)等手段对磁性微球的性能进行了表征.实验结果表明,Fe3O4/P(MMA/DVB)微球的磁含量为84 wt%;通过改变加入壳层单体的量,核壳复合微球的磁含量可控在20 wt%~76 wt%之间.该微球具有超顺磁性,相应的饱和磁化强度为12~50Am2/kg.     

A thermosensitive amphoteric microsphere and its potential application as a biological carrier

Thermosensitive poly(N-isopropylacrylamide) moieties were introduced onto amphoteric styrene/glycidyl methacrylate copolymer seed microspheres prepared by use of amphoteric initiators. The resulting microspheres exhibited thermosensitive and amphoteric behavior, so dual sensitivity to both pH and temperature was observed. The colloidal properties of the microspheres before and after seeded polymerization were characterized by varying the temperature and the pH. The results indicated that the specific surface structure emerged when the environmental conditions were changed. In addition, the reactive epoxy groups on the microsphere surface could be utilized to immobilize the protein molecules. The behavior of protein adsorption and immobilization onto the microspheres was examined in order to understand their potential applications in biological areas.     

Characterization of the surface hydrolysis of kevlar-49 fibers by diffuse reflectance FTIR spectroscopy

A modified diffuse reflectance technique is used to characterize the surface hydrolysis of Kevlar-49 fibers. Treatment with 10 wt% NaOH solution produces carboxylate groups on the surface which increase rapidly up to treatment times of about 20 min at room temperature or 50 min in boiling solution. After this maximum the carboxylate groups decrease and then level out. This behavior can be explained by considering the increase as due to hydrolysis of the surface amide groups, competing with the decrease due to removal of the extensively hydrolyzed, fragmented molecules into the treatment solution. Our results shows that mild conditions (10 wt% NaOH and room temperature) as well as relatively small treatment times (less than 20 min) can be used for modifying the surface of the Kevlar-49 fiber without destroying the skin and thus deteriorating the mechanical properties of the fiber.     

膜乳化-溶剂挥发法制备表面羧基功能化苯乙烯-马来酸酐共聚物微球

以苯乙烯-马来酸酐共聚物(PSMA)为原料,利用膜乳化-溶剂挥发法,成功制备了表面光滑、尺寸均一的表面羧基功能化聚合物微球.研究表明:将膜乳化法和溶剂挥发法相结合,可以有效提高微球粒径的均一性,乳化剂种类及浓度、连续相流速、分散相中聚合物浓度等参数对微球粒径及粒径分布有显著影响.此外,利用盐酸使微球酸酐基团水解,可以得...     

A Simple Approach to Fabricate CdS-SiO2 Hybrid Microspheres by Producing CdS Nanoparticles on the Surface of Thiolated SiO2 Microspheres

IntroductionSemiconductor nanoparticles show a quantum sizeeffect and have attracted much attention because oftheir unique photochemical and photophysical proper-ties[1—4].In recent years,quantumdots of CdS and in-organic nanoparticles hybrid composites …     

Fast Adsorption of Soft Hydrogel Microspheres on Solid Surfaces in Aqueous Solution

The real‐time adsorption behavior of polymeric colloidal microspheres onto solid surfaces in aqueous solution was visualized for the first time using high‐speed atomic force microscopy (HS‐AFM) to reveal how the softness of the microspheres affects their dynamic adsorption. Studies that focus on the deformability of microspheres upon dynamic adsorption have not yet been reported, most likely on account of a lack of techniques that appropriately depict the dynamic adsorption and deformation behavior of individual microspheres at the nanoscale in real time. In this study, the deformability of microspheres plays a crucial role on the adsorption kinetics, that is, soft hydrogel microspheres adsorb faster than harder elastomeric or rigid microspheres. These results should provide insight towards development of new colloidal nanomaterials that exhibit effective adsorption on specific sites in aqueous solution.     

Controllable preparation of nanoparticle-coated chitosan microspheres in a co-axial microfluidic device

In this work, we describe a novel and simple microfluidic method for fabricating nanoparticle-coated chitosan microspheres. Uniform droplets of aqueous chitosan solution were dispersed into an oil phase containing partially hydrophilic nanoparticles via a co-axial microfluidic device. Recirculating flow in the continuous phase in the area between drops enhanced mixing and allowed the nanoparticles to coat the surface of the droplets as they passed through the channel. The chitosan droplets were then crosslinked with glutaraldehyde and nanoparticle-coated microspheres were obtained. SEM characterization shows that the microspheres are monodispersed with uniform nanoparticle distribution on the surface. The dispersity, size and composition of the microspheres could all easily be controlled by changing the microfluidic flow parameters and three different types of nanoparticles were successfully used to synthesize hybrid microspheres to demonstrate the method's versatility.