纳米羟基磷灰石/胶原复合材料制备方法比较研究

低温下,通过将水热合成的纳米羟基磷灰石浆料与中性胶原溶胶共混和在中性胶原中原位形成羟基磷灰石两种方法制备羟基磷灰石／胶原复合材料,采用XRD、FTIR、扫描电镜、透射电镜和力学性能测试等方法对两种复合材料的特性进行了表征。通过对两种方法制备的复合材料的特性进行比较,发现两种方法均制备得到了纳米羟基磷灰石／胶原复合材料,复合材料在晶相组成、化学组成、纳米羟基磷灰石晶体尺寸、胶原纤维的结构等方面都与天然骨相似。但原位合成纳米羟基磷灰石晶体的结晶度比水热合成的纳米羟基磷灰石更接近于自然骨,原位合成的羟基磷灰石／胶原复合材料的均匀性、界面结合紧密度、力学性能等方面均优于共混法。原位合成法是改善纳米羟基磷灰石／胶原复合材料均匀性和力学性能的有效方法。     

生物降解高分子/羟基磷灰石复合材料研究进展

由于高分子/HA复合材料兼具HA优良的生物性能和高分子材料良好的力学性能而受到了广泛的重视.本文综述了近年来生物降解高分子/羟基磷灰石复合材料的研究进展,介绍了胶原及其衍生物、聚酯、甲壳素及其衍生物、淀粉等可降解高分子材料与羟基磷灰石复合作为骨修复材料的研究进展,并对此类材料存在的问题和发展前景进行了讨论.     

复合凝胶途径制备胶原-海藻酸钠-羟基磷灰石支架材料

羟基磷灰石和胶原是人体骨的主要成分,近年来,制备纳米羟基磷灰石/ 胶原复合材料已成为目前生物材料研究的热点之一[1-3].海藻酸钠是一种酸性的多聚糖,具有良好的生物相容性,目前已经被广泛应用于化学、生物、医药、食品等领域;海藻酸钠能与钙离子交联,可进一步获得具有良好弹性性能的网状结构[4,5].     

多孔纳米羟基磷灰石-聚乳酸复合材料的

本文以TIPS法,在溶液中制备得到多孔纳米羟基磷灰石-聚乳酸复合材料,并对无机相与有机相之间的界面结合情况进行了研究,结果表明纳米羟基磷酸钙与聚乳酸基体之间结合良好。     

纳米羟基磷灰石复合材料在硬组织工程领域中的应用研究

人体骨骼的晶体成分主要是纳米羟基磷灰石(n-HA),n-HA具有优良的生物相容性、骨传导性和骨结合能力,被广泛应用于硬组织修复材料中。本文综述了纳米羟基磷灰石在构建人体骨修复支架材料、骨替代材料和口腔医用材料方面的应用研究。     

胶原-羟基磷灰石复合骨组织引导再生膜的制备及性能研究

本研究结合原位合成法和凝胶途径制备了胶原-羟基磷灰石复合膜材料。扫描电镜结果显示,复合膜由胶原纤维三维网络构成,无机相均匀分布于网络中。红外与X射线衍射图谱显示,复合膜的无机相为碳酸取代的弱结晶羟基磷灰石,复合膜具有类似自然骨的组成。与纯胶原膜相比,复合膜的溶胀性能大为改善。通过对复合凝胶的控制脱水,使复合膜具有较高的力学强度和模量,结合微观形貌和脱水控制过程讨论了复合膜的增强机制。本研究制备的胶原-羟基磷灰石复合膜可作为一种良好的骨组织引导再生膜材料。     

羟基磷灰石相关复合材料的研究进展

羟基磷灰石(HAp)作为骨骼中的无机矿物成分,是天然的生物陶瓷材料.由于特殊的结构组成,其具有良好的生物相容性和生物活性.然而,纯的HAp纳米颗粒容易团聚且机械强度低,因此往往需要进一步改性和功能化用于合成HAp相关的复合材料.本综述对元素或官能团掺杂、聚合物/HAp交联、HAp固定在载体材料表面等方式制备的HAp复合...     

羟基磷灰石/胶原矿化机理的研究进展

仿生合成的羟基磷灰石(HAp)/胶原复合材料的结构和成分与天然骨相似,具有很好的生物相容性、生物活性和生物可降解性,有望成为新一代的骨替代材料。羟基磷灰石/胶原矿化过程其实质是晶体在自组装的胶原纤维上形成的过程,但这一过程在体内是如何进行的至今仍然不清楚。对胶原矿化机理的研究能为制备具有更优越结构和功能的新型骨替代材料提供理论参考。本文概述了羟基磷灰石/胶原矿化机理的研究进展。     

羟基磷灰石及其复合材料对重金属的吸附研究进展

羟基磷灰石具有特殊的晶体结构,对二价的重金属离子有很强的结合力,是一种可用于环境污染治理的新型功能性材料。它可有效地吸附去除水中的Pb2+,Cd2+,Cu2+,Zn2+,Co2+,Ni2+等重金属离子,但其粉体的结构却限制了它在水环境中的实际应用。随着纳米技术、复合材料技术的发展,在羟基磷灰石的基础上开发出的具有高效吸附性能或分离特性的新型材料在重金属吸附研究中显示了潜在的优势。本文综述了羟基磷灰石及其复合材料对水中重金属去除方面的研究进展,探讨了它对重金属吸附机理,并对羟基磷灰石进一步的研究提出了展望。     

可降解聚乳酸/羟基磷灰石杂化材料Ⅰ.纳米羟基磷灰石的合成

可降解聚乳酸/羟基磷灰石杂化材料Ⅰ.纳米羟基磷灰石的合成;化学共沉淀;共沸蒸馏;纳米羟基磷灰石;表面处理剂     

Fabrication and characterization of low-cost freeze-gelated chitosan/collagen/hydroxyapatite hydrogel nanocomposite scaffold

In the present research, chitosan/collagen and chitosan/collagen/nano-hydroxyapatite (nHAP) hydrogel nanocomposites were prepared using naturally extracted chitosan from Persian Gulf shrimp wastes and rat tail-tendon collagen. Freeze-gelation method was used to prepare highly porous scaffolds. The morphology, chemical structure, water retainability, and thermal properties were characterized using SEM, FTIR, water content experiment, simultaneous thermal analysis (STA), respectively. Atomic force microscopy (AFM) nanoindentation and unconfined compression test were used to assess different feature of the mechanical properties of the hydrogels. The obtained results were so promising that the prepared nanocomposites can be considered as a potential candidate for cartilage tissue engineering.     

Fabrication of chitosan/collagen/hydroxyapatite scaffolds with encapsulated Cissus quadrangularis extract

Here, we demonstrated the fabrication of a composite scaffold (chitosan [CS], collagen [Col], and hydroxyapatite [HA]) with the incorporation of encapsulated Cissus quadrangularis (CQ) extract for tissue engineering applications. First, the crude extract of CQ loaded nanoparticles were synthesized via double emulsion technique using polycaprolactone (PCL) and polyvinyl alcohol (PVA) as oil and aqueous phases, respectively. Both PCL (20, 40, and 80 mg/mL) and PVA (0.5%, 1%, and 3% w/v) concentrations were varied to determine the optimum concentrations for CQ‐loaded nanoparticle preparation. The CQ‐loaded PCL nanoparticles (CQ‐PCL NPs), prepared with 20 mg/mL PCL and 0.5% (w/v) PVA, exhibited the smallest size of 334.22 ± 43.21 nm with 95.54 ± 1.49% encapsulation efficiency. Then, the CQ‐PCL NPs were incorporated into the CS/Col/HA scaffolds. These scaffolds were also studied for their ultrastructure, pore sizes, chemical composition, compressive modulus, water swelling, weight loss, and biocompatibility. The results showed that the addition of CQ‐PCL NPs into the scaffolds did not dramatically alter the ultrastructure and properties of the scaffolds, compared to CS/Col/HA scaffolds alone. However, incorporation of CQ‐PCL NPs in the scaffolds improved the release profile of CQ by preventing the initial burst release and prolonging the release rate of CQ. In addition, the CQ‐PCL NPs‐loaded CS/Col/HA scaffolds supported the attachment and proliferation of MC3T3‐E1 osteoblast cells.     

The influence of hydroxyapatite modification on the cross-linking of polydimethylsiloxane/HAp composites

Hydroxyapatite (HAp) was modified by the action of various hydrophobic agents based on silicon-containing compounds. The influence of the type of applied agent on the thermodynamic and kinetic parameters of the cross-linking of poly(dimethyl siloxane)/HAp composites was investigated. All the modified HAp particles became hydrophobic and these samples were used to synthesize the polysiloxane/hydroxyapatite composites (PDMS/HAp). The possible modes of interaction between the hydroxyapatite and hydrophobing agents were discussed. The most probable interaction between hydroxyapatite and the applied hydrophobing agents is hydrogen bonding. PDMS/HAp composites were formed directly in the cell of the DSC and cross-linking was investigated in situ. It was determined that the introduction of hydroxyapatite into polysiloxane matrices changed the enthalpy of cross-linking, as well as the activation energy of cross-linking and reaction order, while the introduction of modified HAp led to thermodynamic and kinetic parameters more similar to those of the cross-linking of unfilled elastomer.     

Controlling coupling reaction of EDC and NHS for preparation of collagen gels using ethanol/water co-solvents

To control the crosslinking rate of the collagen gel, ethanol/water co-solvent was adopted for the reaction solvent for the collagen microfibril crosslinking. Collagen gel was prepared by using EDC and NHS as coupling agents. Ethanol did not denaturate the helical structure of the collagen and prevented the hydrolysis of EDC, but showed the protonation of carboxylate anions. In order to control the intra- and interhelical crosslink of the collagen triple helix, variations of the mole ratio of carboxyl group/EDC/NHS, and of the ethanol mole concentration were investigated. Increase in the EDC ratio against the carboxyl group increased the crosslinking rate. Furthermore, an increase in the ethanol mole concentration resulted in an increase of the crosslinking rate until ethanol mole concentration was 0.12, but showed gradual decrease as the ethanol mole concentration was further increased. This is because the adsorption of solvent by the collagen gel, protonation of carboxylate anion, and hydrolysis of EDC is at its most optimum condition for the coupling reaction when the ethanol mole concentration is 0.12. The re-crosslinking of the collagen gel showed an increase in the crosslinking rate, but did not show further increase when the coupling reaction was executed for the third time. This implied that the highest possible crosslinking rate for the intra- and interhelical is approximately 60% when EDC/NHS is used.     

Preparation and characterization of collagen/chitosan poly (ethylene glycol)/nanohydroxyapatite composite scaffolds

Porous three‐dimensional collagen/chitosan scaffolds combined with poly (ethylene glycol) (PEG) and hydroxyapatite were obtained through a freeze‐drying method. Physical cross‐linking was examined by dehydrothermal treatment. The prepared materials were characterized by different analyses, eg, scanning electron microscopy (SEM), measurements of porosity and swelling, mechanical properties, and resistance to enzymatic degradation. The porosity of scaffolds and their swelling ratio decreased with the addition of hydroxyapatite. Moreover, after exposure to collagenase, the collagen/chitosan matrices containing PEG showed much faster degradation rate than matrices with the addition of hydroxyapatite. The results indicated that the addition of hydroxyapatite led to improvement of stiffness. The highest degree of porosity and swelling were demonstrated by collagen/chitosan/PEG matrices without hydroxyapatite.     

Synthesis and characterization of a nano‐hydroxyapatite/chitosan/polyethylene glycol nanocomposite for bone tissue engineering

A novel nanocomposite involving nano‐hydroxyapatite/chitosan/polyethylene glycol (n‐HAP/CS/PEG) has been successfully synthesized via co‐precipitation approach at room temperature. The purpose to synthesize such nanocomposite is to search for an ideal analogue which may mimick the composition of natural bone for bone tissue engineering with respect to suitable biocompatibility, cytotoxicity and mechanical properties. The FTIR spectra of n‐HAP/CS and n‐HAP/CS/PEG scaffolds indicated significant intermolecular interaction between the various components of both the nanocomposites. The results of XRD, TEM and TGA/DTA suggested that the crystallinity and thermal stability of the n‐HAP/CS/PEG scaffold have decreased and increased respectively, relative to n‐HAP/CS scaffold. The comparison of SEM images of both the scaffolds indicated that the incorporation of PEG influenced the surface morphology while a better in‐vitro bioactivity has been observed in n‐HAP/CS/PEG than in n‐HAP/CS based on SBF study, referring a greater possibility for making direct bond to living bone if implanted. Furthermore, MTT assay revealed superior non‐toxic nature of n‐HAP/CS/PEG to murine fibroblast L929 cells as compared to n‐HAP/CS. The comparative swelling studies of n‐HAP/CS/PEG and n‐HAP/CS scaffolds revealed a better swelling rate for n‐HAP/CS/PEG. Also n‐HAP/CS/PEG showed higher mechanical strength relative to n‐HAP/CS supportive of bone tissue ingrowths. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of polyaniline/silicon dioxide composites and preparation of conductive films

The focus of this study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO₂) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO₂ composite films were prepared by drop‐by‐drop and spin coating methods. The electrical conductivities of HCl doped PANI film and PANI/SiO₂ composite films were measured according to the standard four‐point‐probe technique. The composite films exhibited an increase in electrical conductivity over neat PANI. PANI and PANI/SiO₂ composites were also investigated by spectroscopic methods including UV‐Vis, FT‐IR, and Photoluminescence. UV‐Vis and FT‐IR studies showed that SiO₂ particles affect the quinoid units along the polymer backbone and indicate strong interactions between the SiO₂ particles and the quinoidal sites of PANI (doping effect). The photoluminescence properties of PANI and PANI/SiO₂ composites were studied and the PANI/SiO₂ composites showed increased intensity as compared to neat PANI. The increase of conductivity of PANI/SiO₂ composite may be partially due to the doping or impurity effect of SiO₂ where the silicon dioxides compete with chloride ions. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO₂ were well dispersed and isolated in composite films. Copyright © 2009 John Wiley & Sons, Ltd.     

Recent advances in application and progress of advanced materials as adsorbents in sample preparation for plant growth regulators

Plant growth regulators are a class of physiologically active substances that could modify or regulate basic physiological processes in the plant and defense against abiotic and biotic stresses, including natural plant growth regulators and synthetic ones. Different from natural plant growth regulators with low content and high cost of extraction in plants, synthetic ones can be produced in large-scale production and widely used in agriculture for increasing and securing yield and quality of the harvested produce. However, like pesticides, the abuse of plant growth regulators will have negative impacts on human beings. Therefore, it is important to monitor plant growth regulators residues. Due to the low concentration of plant growth regulators and complex matrices of food, it is necessary to isolate and extract plant growth regulators by appropriate adsorbents in sample preparation for obtaining satisfactory results. In the last decade, several advanced materials as adsorbents have shown superiority in sample preparation. This review briefly introduces the recent application and progress of advanced materials as adsorbents in sample preparation for extraction of plant growth regulators from the complex matrix. In the end, the challenge and outlook about the extraction of plant growth regulators of these advanced adsorbents in sample preparation are presented.