Biomimetic calcium phosphate crystal mineralization on electrospun cellulose-based scaffolds

Novel cellulose based-scaffolds were studied for their ability to nucleate bioactive calcium phosphate crystals for future bone healing applications. Cellulose-based scaffolds were produced by electrospinning cellulose acetate (CA) dissolved in a mixture of acetone/dimethylacetamide (DMAc). The resulting nonwoven CA mats containing fibrils with diameters in the range of 200 nm to 1.5 μm were saponified by NaOH/ethanol for varying times to produce regenerated cellulose scaffolds. Biomimetic crystal growth nucleated from the fiber surface was studied as a function of surface chemistry. Regenerated cellulose scaffolds of varying treatments were soaked in simulated body fluid (SBF) solution. Scaffolds that were treated with CaCl(2), a mixture of carboxymethyl cellulose (CMC) and CaCl(2), and NaOH and CaCl(2), were analyzed using X-ray photoelectron spectroscopy, X-ray powder diffraction, and scanning electron microscopy to understand the growth of bioactive calcium phosphate (Ca-P) crystals as a function of surface treatment. The crystal structure of the nucleated Ca-P crystals had a diffraction pattern similar to that of hydroxyapatite, the mineralized component of bone. The study shows that the scaffold surface chemistry can be manipulated, providing numerous routes to engineer cellulosic substrates for the requirements of scaffolding.     

碳酸钙微球的制备及其机理

为了制备出形貌更好的碳酸钙微球,以氯化钙和碳酸钠为原料,通过乙醇溶液和添加柠檬酸2种不同的方法制备。利用场发射扫描电镜、X射线衍射和傅里叶变换红外光谱等方法对制备的产物进行分析。结果表明,50%体积分数的乙醇溶液与1.0 mol·L-1柠檬酸调控下都能制备出形貌良好的碳酸钙微球,采用柠檬酸制备的碳酸钙微球成球性较好,制备的碳酸钙微球均由不同的晶型构成。实验通过改变反应条件进一步探索了在柠檬酸控制下碳酸钙微球的成球机理。     

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。     

Biomimetic mineralization of novel silane crosslinked collagen

Studies on the mechanisms of mineralization of connective tissues, have gained momentum in the recent past. In the present study, Biomimetic mineralization of modified fish scale collagen in vitro is reported. The fish scale collagen was crosslinked with 3-Aminopropyl triethoxysilane and the crosslinked collagen (FCSi) was characterized using conventional methods. The biomimetic mineralization capacity of FCSi was evaluated in SBF solution for 7 days. Formation of hydroxyapatite crystals on the matrix in vitro has been confirmed by FTIR, XRD and SEM-EDAX techniques. The FCSi may be used as a scaffold in bone tissue engineering and as an osteoinductive material in experimental animal models before applying clinically.     

The co-effect of organic matrix from carp otolith and microenvironment on calcium carbonate mineralization

In vitro mineralization experiment is an effective way to study the effect of organic matrix on calcium carbonate crystallization, and to reveal the relationship between organic matrix and inorganic crystal in natural biominerals. In natural biominerals, organic matrix plays an important role in crystal formation and stability, together with microenvironment changes, they can affect crystal polymorph, morphology, density, size, orientation etc.In this work, we systematically studied the effects of different organic matrices in fish otoliths, the organic matrix concentration changes, as well as the co-effect of organic matrices with temperature, pH value and Mg ion changes in the in vitro CaCO₃ mineralization experiments.The organic matrix and concentration change experiments prove that water soluble matrix (WSM) plays an important role in crystal form transition. It can induce CaCO₃ crystals with same crystal polymorph as the otolith from which organic matrix was extracted. The temperature change experiment proves that CaCO₃ has a tendency to form calcite, vaterite, and then aragonite in priority as temperature goes up. Under different temperature, WSM from lapillus/asteriscus still has the effect to mediate different CaCO₃ crystals. The pH change experiment shows that, near the neutral environment, as pH value goes up, calcites have a tendency to form crystal aggregates with more faces exposed, the organic matrix still keeps crystal mediation effect. The Mg^2 + experiment shows that, Mg ion can promote aragonite formation, together with lapillus organic matrix, aragonites with different shapes are formed.     

Biomimetic synthesis of PbS nanocubes in the lysozyme solution

Cubic phase PbS nanocubes were fabricated using lysozyme as template by biomimetic synthesis method at room temperature. The prepared nanocubes are uniform and monodispersed with homogeneous size around 45 nm. The interaction of Pb²⁺/PbS with the lysozyme was studied through Fourier transform infrared (FTIR) spectroscopy, and the shift of characteristic IR peaks of the lysozyme suggesting that Pb²⁺/PbS can react with − OH and − NH groups of the lysozyme. Optical properties of the obtained PbS nanocubes were investigated by photoluminescence (PL) spectroscopy. PbS nanocrystals exhibit a well-defined emission feature at 470 nm excited by 300 nm wavelength (λ_ex). The experimental results indicated that the lysozyme not only induced nucleation, but also inhibited the further growth of PbS crystals and play an important role in formation of PbS nanocubes.     

Biomimetic mineralization of calcium phosphate crystals in polyacrylamide hydrogel: Effect of concentrations of calcium and phosphate ions on crystalline phases and morphology

Calcium phosphate crystals were synthesized in polyacrylamide (PAAm) hydrogel, and the effects of the concentrations of calcium and phosphate ions on the crystalline phases and morphology were investigated. PAAm hydrogels containing diammonium hydrogen phosphate ((NH₄)₂HPO₄) were transformed into calcified materials by diffusion of calcium ions from calcium nitrate (Ca(NO₃)₂) aqueous solution into the gels. Several kinds of calcium phosphate crystals were precipitated at various Ca(NO₃)₂ concentrations (0.5–4.0 mol·dm^? 3), or (NH₄)₂HPO₄ contents (3.6–21.6 mmol) in the gels. The crystalline phases were mainly determined by the (NH₄)₂HPO₄ content in the gels. When the (NH₄)₂HPO₄ content was ≥ 10.8 mmol, hydroxyapatite (HAp) formed near the interfaces between Ca(NO₃)₂ solution and the gels, whereas octacalcium phosphate (OCP) formed in gels with ≤ 10.8 mmol (NH₄)₂HPO₄. HAp crystals were granular in form and about 200 nm in diameter, and OCP crystals were spherulitic with diameter 10–70 μm.     

PP/elastomer/calcium carbonate composites: effect of elastomer and calcium carbonate contents on the deformation and impact behavior

The morphology and mechanical behavior of ternary polypropylene/ethylene-octene copolymer/calcium carbonate composites have been investigated as a function of elastomer and filler contents. A separate dispersion of phases was observed. Increasing concentration of EOC and CaCO₃ promotes a decrease of matrix ligament thickness between elastomer particles resulting in a huge increase of the toughness. The stiff filler used in this study provided the unusual additional benefit of substantially increasing in Young's and flexural modulus of the composites.     

Biomimetic mineralization of partially bioresorbable glass fiber reinforced composite

The aim of this study was to investigate the biomimetic mineralization on the surface of a glass fiber reinforced composite with partially resorbable biopolymer matrix. The E-glass fibers were preimpregnated with a novel biopolymer of poly(hydroxyproline) amide, and further impregnated in the monomer system of bis-phenyl glycidyl dimethacrylate (Bis-GMA)—triethylene glycol dimethacrylate (TEGDMA), which formed interpenetrating polymer networks (IPN) with the preimpregnation polymer. After light-initiated polymerization of the monomer system, the rhombic test specimens (n = 6) were immersed in the simulated body fluid (SBF) with the bioactive glass for 24 h, and then the apatite nuclei were allowed to grow for 1, 3, 5 and 7 days in the SBF. The control test specimens (n = 3) were immersed in SBF without the bioactive glass. According to the scanning electron microscope (SEM), a mineral layer was formed on the surface of all the specimens, which were immersed with bioactive glass. The layer was thickened by the prolonged immersion time to a uniform layer. The Ca/P atomic ratio of the mineral varied between 1.30 and 1.54 as analyzed by the energy dispersive X-ray analysis (EDXA). The Fourier transform infrared spectroscopy (FT-IR) spectra gave signals for the mineral, which are characteristic of both bone-like apatite and orthocalciumphosphate. In conclusion, the mineral layer was formed on the surfaces of the specimens by biomimetic mineralization, the mineral being a mixture of bone-like apatite, orthocalciumphosphate and other calcium phosphates.     

Nontoxic poly(ethylene oxide phosphonamidate) hydrogels as templates for biomimetic mineralization of calcium carbonate and hydroxyapatite architectures

A simple protocol has been developed for the creation of the biomimetic hybrid materials, calcium carbonate, and hydroxyapatite, by in situ growth and mineralization in newly developed nontoxic hydrogel templates. A series of poly(ethylene oxide phosphonamidate) hydrogels with different network structures were synthesized by reacting various poly(ethylene glycol)s with phosphorous oxychloride and diamines in a one-pot protocol, which exhibits promising advantages including a short reaction time, an easy separation, and a high yield with a mass producible feasibility. The hydrogels were proven to be nontoxic according to an in vitro viability assay using human embryonic kidney 293T cells. Careful control of growth and mineralization conditions such as ions transport rate, pH, type of hydrogel, and mineralization temperature resulted in a variety of calcium carbonate and hydroxylapatite architectures including nanorods, nanowires, and well-defined hybrid structures. The resulting materials were analyzed by infrared spectroscopy, electron microscopes, energy-dispersive X-ray spectroscopy, and X-ray powder diffraction.     

聚苯乙烯磺酸钠/L-谷氨酸协同作用下新型碳酸钙微球的简易合成

聚苯乙烯磺酸钠(PSSS)/L-谷氨酸(L-Glu)二元体系中,利用缓慢扩散的CO2与在有机_无机界面上富集的钙离子相结合,合成了碳酸钙微球.实验表明,PSSS/L_Glu浓度比对碳酸钙晶体的形貌和晶型有着重要影响.通过改变实验条件,还得到了菱形和立方形晶体.取向聚积理论很好地解释了微球晶体的形成.PSSS/L-Glu间的协同作用在晶体化过程中发挥着重要作用.通过X射线粉末衍射仪、透射电镜、扫描电子显微镜等分析手段对产物进行了表征.     

P(GMA-co-MMA)磁性复合微球的制备及木瓜蛋白酶的固定化

在改性Fe3O4纳米颗粒存在的条件下用乳液聚合法制备了表面带有环氧基的聚甲基丙烯酸缩水甘油酯一聚甲基丙烯酸甲酯P(GMA-co-MMA)磁性复合微球,对其粒径、形态、磁含量、磁性质进行了表征;在复合微球表面引入氨基后,以戊二醛为交联剂,固定木瓜蛋白酶,探讨了给酶量、戊二醛浓度对固定化酶活性的影响,考察了酶学性质.结果表...     

Calcium carbonate microspheres as carriers for the anticancer drug camptothecin

Biogenic calcium carbonate has come to the attention of many researchers as a promising drug delivery system due to its safety, pH sensitivity and the large volume of information already in existence on its medical use. In this study, we employed bovine serum albumin (BSA) as an additive to synthesize a series of porous calcium carbonate microspheres (CCMS). These spheres, identified as vaterite, are stable both in aqueous solutions and organic solvents. Camptothecin, an effective anticancer agent, was loaded into the CCMS by simple diffusion and adsorption. The camptothecin loaded CCMS showed sustained cell growth inhibitory activity and a pH dependent release of camptothecin. With a few hours, the release is negligible under physiological conditions (pH = 7.4) but almost complete at pH 4 to 6 (i.e. pHs found in lysosomes and solid tumor tissue respectively). These findings suggest that porous, biogenic calcium carbonate microspheres could be promising carriers for the safe and efficient delivery of anticancer drugs of low aqueous solubility.     

Poly-L-ornithine/fucoidan-coated calcium carbonate microparticles by layer-by-layer self-assembly technique for cancer theranostics

Recently, the layer-by-layer (LbL) self-assembly technology has attracted the enormous interest of researchers in synthesizing various pharmaceutical dosage forms. Herewith, we designed a biocompatible drug delivery system containing the calcium carbonate microparticles (CaCO₃ MPs) that coated with the alternatively charged polyelectrolytes, i.e., poly-L-ornithine (PLO)/fucoidan by LbL self-assembly process (LbL MPs). Upon coating with the polyelectrolytes, the mean particle size of MPs obtained from SEM observations increased from 1.91 to 2.03?μm, and the surface of LbL MPs was smoothened compared to naked CaCO₃ MPs. In addition, the reversible zeta potential changes have confirmed the accomplishment of layer upon a layer assembly. To evaluate the efficiency of cancer therapeutics, we loaded doxorubicin (Dox) in the LbL MPs, which resulted in high (69.7%) drug encapsulation efficiency. The controlled release of Dox resulted in the significant antiproliferative efficiency in breast cancer cell line (MCF-7 cells), demonstrating the potential of applying this innovative drug delivery system in the biomedical field.     

放射自显影海藻酸钙栓塞微球的制备

利用乳化-内部凝胶化法,将放射显影剂碘化油包封于海藻酸钙微球中.通过改变机械搅拌速率可以控制微球的粒径分布.碘化油/海藻酸钙微球可以作为栓塞制剂阻断患处血供,还可以兼具放射自显影的作用,有利于减少碘化油所导致的不良反应,方便治疗.     

乙醇-水混合溶液中碳酸钙晶须的合成

不加任何添加剂,在乙醇-水的体积比为V(乙醇):V(水)=1:1、温度50℃、原料浓度0.25mol/L的条件下,利用沉淀法制得了大小均匀、长度为10～30μm、长径比为20～30:1的文石型碳酸钙晶须.同时,实验中还得到了树枝形和稻穗状等特殊形貌的晶体.用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、红外光谱仪(...     

Micropatterned TiO2 effects on calcium phosphate mineralization

The effects of implant surface topography and chemistry on biomineralization have been a research focus because of their potential importance in orthopedic and bone replacement applications. While a vast amount of research is focusing on chemical modified surfaces and rough surfaces, little attention has been paid to the well-defined micropatterned surface effects on calcium phosphate mineralization process due to the difficulties in preparing microfabricated biomaterial surfaces. This work focuses on the effects of microgrooved TiO₂ surfaces on the calcium phosphate mineralization process. Firstly, we developed a new process that can prepare microgrooved TiO₂ coatings on glass substrates using soft-lithography and sol–gel technology. Then microgrooved TiO₂ surfaces were used to induce Ca–P mineralization under biomimetic conditions. The results revealed that topography dominated the growth and distribution of mineralization at the initial days and then the effects of topography become weak with the extended immersion days.     

磷酸钙在纳米羟基磷灰石／硅橡胶复合材料表面的仿生合成

将纳米羟基磷灰石，硅橡胶复合材料浸泡于模拟体液（SBF）中仿生合成了磷酸钙，利用IR、XRD、ICP和SEM等测试手段对表面沉积物进行表征．结果表明：在模拟体液中浸泡后，复合材料表面形成了分布均匀的以羟基磷灰石为主要成分的晶粒，表面羟基磷灰石的比例得到提高，生物学性能得以进一步改善；表明纳米羟基磷灰石，硅橡胶复合材料是一种生物活性材料．