Mineralization of synthetic polymer scaffolds: a bottom-up approach for the development of artificial bone

The controlled integration of organic and inorganic components confers natural bone with superior mechanical properties. Bone biogenesis is thought to occur by templated mineralization of hard apatite crystals by an elastic protein scaffold, a process we sought to emulate with synthetic biomimetic hydrogel polymers. Cross-linked polymethacrylamide and polymethacrylate hydrogels were functionalized with mineral-binding ligands and used to template the formation of hydroxyapatite. Strong adhesion between the organic and inorganic materials was achieved for hydrogels functionalized with either carboxylate or hydroxy ligands. The mineral-nucleating potential of hydroxyl groups identified here broadens the design parameters for synthetic bonelike composites and suggests a potential role for hydroxylated collagen proteins in bone mineralization.     

Sol–gel derived organic–inorganic hybrid materials: synthesis,characterizations and applications

Organic/inorganic hybrid materials prepared by the sol–gel approach have rapidly become a fascinating new field of research in materials science. The explosion of activity in this area in the past decade has made tremendous progress in both the fundamental understanding of the sol–gel process and the development and applications of new organic/inorganic hybrid materials. Polymer-inorganic nanocomposite present an interesting approach to improve the separation properties of polymer material because they possess properties of both organic and inorganic such as good permeability, selectivity, mechanical strength, and thermal and chemical stability. Composite material derived by combining the sol–gel approach and organic polymers synthesis of hybrid material were the focus area of review It has also been demonstrated in this review that a more complete understanding of their structure–property behavior can be gained by employing many of the standard tools that are utilized for developing similar structure–property relationships of organic polymers. This review article is introductory in nature and gives introduction to composite materials/nanocomposite, their applications and the methods commonly employed for their synthesis and characterization. A brief literature survey on the polysaccharide templated and polysaccharide/protein dual templated synthesis of silica composite materials is also presented in this review article.     

TiO2 synthesis inspired by biomineralization: control of morphology, crystal phase, and light-use efficiency in a single process

Hydroxyapatite is mineralized along the long axis of collagen fiber during osteogenesis. Mimicking such biomineralization has great potential to control inorganic structures and is fast becoming an important next-generation inorganic synthesis method. Inorganic matter synthesized by biomineralization can have beautiful and functional structures that cannot be created artificially. In this study, we applied biomineralization to the synthesis of the only photocatalyst in practical use today, titanium dioxide (TiO(2)). The photocatalytic activity of TiO(2) mainly relates to three properties: morphology, crystal phase, and light-use efficiency. To optimize TiO(2) morphology, we used a simple sequential peptide as an organic template. TiO(2) mineralized by a β-sheet peptide nanofiber template forms fiber-like shapes that are not observed for mineralization by peptides in the shape of random coils. To optimize TiO(2) crystal phase, we mineralized TiO(2) with the template at 400 °C to transform it into the rutile phase and at 700 °C to transform it into a mixed phase of anatase and rutile. To optimize light-use efficiency, we introduced nitrogen atoms of the peptide into the TiO(2) structure as doped elemental material during sintering. Thus, this biomineralization method enables control of inorganic morphology, crystal phase, and light-use efficiency in a single process.     

Solvothermal Transformation of a Calcium Oleate Precursor into Large‐Sized Highly Ordered Arrays of Ultralong Hydroxyapatite Microtubes

Hydroxyapatite (HAP), a well‐known member of the calcium phosphate family, is the major inorganic component of bones and teeth in vertebrates. The highly ordered arrays of HAP structures are of great significance for hard tissue repair and for understanding the formation mechanisms of bones and teeth. However, the synthesis of highly ordered HAP structure arrays remains a great challenge. In this work, inspired by the ordered structure of tooth enamel, we have successfully synthesized three‐dimensional bulk materials with large sizes (millimeter scale) that are made of highly ordered arrays of ultralong HAP microtubes (HOAUHMs) by solvothermal transformation of calcium oleate precursor. The core–shell‐structured oblate sphere consists of a core that is composed of HAP nanorods and a shell that consists of highly ordered HAP microtube arrays. The prepared HOAUHMs are large: 6.0 mm in diameter and up to 1.4 mm in thickness. With increasing solvothermal reaction time, the HOAUHMs grow larger; the microtubes become more uniform and more ordered. This work provides a new synthetic method for synthesizing highly ordered arrays of uniform HAP ultralong microtubes that are promising for biomedical applications.     

仿生矿化的机理和应用研究进展

碳酸钙、磷酸钙为代表的生物矿物广泛分布于自然界中,经过不同的矿化过程,在生物体内呈现出多样的结构、形貌和功能,构成生物体多种组织和器官.在人工材料合成领域,仿生矿化通过调控碳酸钙、磷酸钙等矿物的成核与生长,获得具有复杂高级结构和特殊生物功能的无机或无机/有机复合材料.本文重点介绍仿生矿化机理和应用的最近研究进展,包括仿...     

Organically-templated metal sulfates, selenites and selenates

The literature on inorganic open-framework materials abounds in the synthesis and characterization of metal silicates, phosphates and carboxylates. Most of these materials have an organic amine as the template. In the last few years, it has been shown that anions such as sulfate, selenite and selenate can also be employed to obtain organically templated open-framework materials. This tutorial review provides an up-to-date survey of organically templated metal sulfates, selenites and selenates, prepared under hydrothermal conditions. The discussion includes one-, two-, and three-dimensional structures of these materials, many of which possess open architectures. The article should be useful to practitioners of inorganic and materials chemistry, besides students and teachers. The article serves to demonstrate how most oxy-anions can be used to build complex structures with metal-oxygen polyhedra.     

Dentin Phosphoprotein Mimetic Peptide Nanofibers Promote Biomineralization

Dentin phosphoprotein (DPP) is a major component of the dentin matrix playing crucial role in hydroxyapatite deposition during bone mineralization, making it a prime candidate for the design of novel materials for bone and tooth regeneration. The bioactivity of DPP‐derived proteins is controlled by the phosphorylation and dephosphorylation of the serine residues. Here an enzyme‐responsive peptide nanofiber system inducing biomineralization is demonstrated. It closely emulates the structural and functional properties of DPP and facilitates apatite‐like mineral deposition. The DPP‐mimetic peptide molecules self‐assemble through dephosphorylation by alkaline phosphatase (ALP), an enzyme participating in tooth and bone matrix mineralization. Nanofiber network formation is also induced through addition of calcium ions. The gelation process following nanofiber formation produces a mineralized extracellular matrix like material, where scaffold properties and phosphate groups promote mineralization. It is demonstrated that the DPP‐mimetic peptide nanofiber networks can be used for apatite‐like mineral deposition for bone regeneration.     

Spectroscopic characterization of porous nanohydroxyapatite synthesized by a novel amino acid soft solution freezing method

In this paper, we have reported a novel method to synthesize nanoporous hydroxyapatite (HAP) powders by freezing organic–inorganic soft solutions. The formation of porous and crystalline HAP nanopowder was achieved via calcining the samples at 600 °C followed by sintering at temperatures ranging from 900 °C to 1100 °C. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopic (SEM) techniques. The results showed the formation of a carbon free nanoporous hydroxyapatite powders due to the decomposition of organic template enclosing the precipitated HAP. It was also observed that the rapid grain growth with retainment of pores while the crystallinity of the HAP nanopowder increased with the increase in sintering temperature which is substantiated from the XRD and SEM results. Such organized porous materials can act as a better biomaterial for bone tissue engineering.     

Phosphorus-containing compounds regulate mineralization

Phosphorus is the main constitutive element of minerals and fat in the body. The process of mineral formation is defined as mineralization. The minerals in the body are mainly apatite, which is the inorganic phase that composes bones and teeth. It is worth noting that people with high fat content tend to cause excessive bone mineralization, which leads us to believe that different phosphorus-containing compounds in the body are mutually transformed and can regulate mineralization in different ways. The conversion and regulation of different phosphorus-containing compounds on the mineralization are essential for formation of a complex hierarchical structure and adaptation of the bone to various mechanical environments. Therefore, this review introduces the natural phosphorus-containing compounds in the body, introduces the hierarchical structure of the bone, and summarizes recent studies on different phosphorus-containing compounds (inorganic, organic, and phosphorus-containing proteases) involved in the biomineralization. We also discuss potential research directions of the biomineralization, offering the basis for future investigation of advanced bone substitute materials.     

无机材料的仿生合成

生物矿化重要的特征之一是细胞分泌的有机基质调制无机矿物的成核和生长, 形成具有特殊组装方式和多级结构特点的生物矿化材料(如骨、牙和贝壳)。仿生合成就是将生物矿化的机理引入无机材料合成, 以有机物的组装体为模板, 去控制无机物的形成,制备具有独特显微结构特点的无机材料, 使材料具有优异的物理和化学性能。仿生合成已成为无机材料化学的研究前沿。本文综述了无机材料仿生合成的发展现状。     

Fructose 1,6‐Bisphosphate Trisodium Salt as A New Phosphorus Source for the Rapid Microwave Synthesis of Porous Calcium–Phosphate Microspheres and their Application in Drug Delivery

Calcium phosphates (CPs), as the major inorganic component of biological hard tissues, have been investigated for applications as biomaterials owing to their excellent biocompatibility. However, the traditional synthetic CPs are usually prepared from inorganic phosphorus and calcium sources. Herein, we report a new strategy for the synthesis of a variety of calcium–phosphate nanostructures, including porous amorphous calcium phosphate (ACP) microspheres, hydroxyapatite (HAP) nanorods, and ACP/HAP composite microspheres, by using fructose 1,6‐bisphosphate trisodium salt (FBP) as an organic phosphorus source in aqueous solution in a rapid microwave‐assisted hydrothermal reaction. The important role of FBP and the effect of the experimental conditions on the formation and evolution of the CPs nanostructures were investigated. The crystal phase and composition of the as‐prepared products were characterized by powder X‐ray diffraction (XRD), FTIR spectroscopy, and thermogravimetric (TGA) analysis and the morphologies of the products were characterized by SEM and TEM. This method is facile, rapid, surfactant‐free, and environmentally friendly. The as‐prepared porous ACP microspheres have a relatively high drug‐loading capacity and good sustained drug‐release behavior; thus, they are promising for applications in drug delivery.     

仿生矿化增强材料

近年来,随着材料科学领域的发展,机械性能优异且具有特定功能的有机-无机复合材料成为了研究热点。而天然的生物矿化过程产生了在自然界中分布广泛、结构特征多样性、机械性能优异的天然生物矿物,比如牙齿、骨骼、珍珠、贝壳、海胆刺、海洋红虫颚等。这些天然复合增强材料中的矿化组织结构特点和矿化机理为仿生设计与合成具有特定结构、特定功能和优异机械性能的材料提供了理论依据。通过模拟天然过程的仿生矿化方法,利用有机基质调控无机矿物成核生长为固态矿物,最终能够定向组装具有特定有序结构和先进功能的有机-无机复合材料。本文主要综述了自然界中通过生物矿化过程得到的高强度、高韧性的天然复合增强材料,以及受生物矿化增强现象的启发,在化学与材料仿生矿化合成中出现的一些有机-无机复合的增强材料。     

骨及生物材料中的纳米磷酸钙

纳米磷酸钙在自然界骨组织的形成过程中起到了关键作用。尽管骨的类型有所不同,但在其初级结构中的无机成分都是纳米磷酸钙。纳米磷酸钙结构能够给予骨良好的机械性能和生物学活性。在生物体中,无机纳米磷酸钙在有机基质的调控下能定向自组装成特定的生物矿物。体外细胞实验显示小尺寸纳米羟基磷灰石更能促进骨髓基质干细胞的增殖,而同尺寸的结晶型纳米磷酸钙则比无定形磷酸钙更能利于干细胞分化。鉴于纳米磷酸钙具有很好的生物相容性和骨诱导性,可以发展成为理想的生物材料常用于骨组织工程和生物医学。     

Nanoscale Confinement Controls the Crystallization of Calcium Phosphate: Relevance to Bone Formation

A key feature of biomineralization processes is that they take place within confined volumes, in which the local environment can have significant effects on mineral formation. Herein, we investigate the influence of confinement on the formation mechanism and structure of calcium phosphate (CaP). This is of particular relevance to the formation of dentine and bone, structures of which are based on highly mineralized collagen fibrils. CaP was precipitated within 25–300 nm diameter, cylindrical pores of track etched and anodised alumina membranes under physiological conditions, in which this system enables systematic study of the effects of the pore size in the absence of a structural match between the matrix and the growing crystals. Our results show that the main products were polycrystalline hydroxapatite (HAP) rods, together with some single crystal octacalcium phosphate (OCP) rods. Notably, we demonstrate that these were generated though an intermediate amorphous calcium phosphate (ACP) phase, and that ACP is significantly stabilised in confinement. This effect may have significance to the mineralization of bone, which can occur through a transient ACP phase. We also show that orientation of the HAP comparable, or even superior to that seen in bone can be achieved through confinement effects alone. Although this simple experimental system cannot be considered, a direct mimic of the in vivo formation of ultrathin HAP platelets within collagen fibrils, our results show that the effects of physical confinement should not be neglected when considering the mechanisms of formation of structures, such as bones and teeth.     

层状固体模板组装有机/无机纳米结构材料

主要介绍了几种有机／无机层状固体模板组装纳米功能材料的研究进展，对模板的类型、制备、纳米结构材料的产生及其应用前景进行了综述。     

Emerging of Inorganic Hole Transporting Materials For Perovskite Solar Cells

Hole transporting material (HTM) is a significant component to achieve the high performance perovskite solar cells (PSCs). Over the years, inorganic, organic and hybrid (organic‐inorganic) material based HTMs have been developed and investigated successfully. Today, perovskite solar cells achieved the efficiency of 22.1 % with with 2,2’,7,7’‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine) 9,9‐spirobifluorene (spiro‐OMeTAD) as HTM. Nevertheless, synthesis and cost of organic HTMs is a major challenging issue and therefore alternative materials are required. From the past few years, inorganic HTMs showed large improvement in power conversion efficiency (PCE) and stability. Recently CuO_x reached the PCE of 19.0% with better stability. These developments affirms that inorganic HTMs are better alternativesto the organic HTMs for next generation PSCs. In this report, we mainly focussed on the recent advances of inorganic and hybrid HTMs for PSCs and highlighted the efficiency and stability of PSCs improved by changing metal oxides as HTMs. Consequently, we expect that energy levels of these inorganic HTMs matches very well with the valence band of perovskites and improved efficiency helps in future practical deployment of low cost PSCs.     

Molecularly templated materials in chemical sensing

Biologically-based recognition elements (e.g., antibodies, aptamers, enzymes, etc.) are used as the recognition element within a wide variety of assays and sensor systems. There are, however, compelling reasons for researchers to develop inexpensive, robust, and reusable alternatives for these expensive and unstable biorecognition elements. This review summarizes recent research efforts on the development of molecularly templated (sometimes called molecularly imprinted) organic and inorganic polymers as possible replacements for expensive/labile biorecognition elements. The review begins with a briefing on biosensing and the pertinent issues and limitations. The focus then swings toward molecularly templating within organic and inorganic (xerogels) polymers to create materials with analyte binding characteristics akin to a biorecognition element. The review then describes several recent developments wherein analyte recognition and an analyte-dependent transduction methodology are simultaneously incorporated directly within the templated materials. The review ends by outlining the current state-of-the-art and the remaining issues and impediments.     

Utilization of the pleiotropy of a peptidic aptamer to fabricate heterogeneous nanodot-containing multilayer nanostructures

Peptide aptamers (=binders) against inorganic materials often show a capacity for mineralization of their target atoms; thus they are able to function both as binding molecules and as mediators for mineralization. Although the mechanisms underlying these two properties of peptide aptamers are not yet fully understood, they have been used separately to fabricate various nanostructures. Here, we present a novel method of nanofabrication, in which binding and mineralization by a peptide aptamer are alternately utilized to assemble multilayered nanostructures comprised of metal loaded cage proteins ornamented with Ti-binding peptides.     

复合生物材料的研究进展

从力学性能的改善和降解速率的可调度等角度,总结了复合生物材料与单一组分的材料相比,在生物医学领域应用中所表现出的综合使用性能的优越性。综述了复合生物材料,特别是用于骨修复的各类有机／无机复合材料近年来的研究进展状况。提出将与人骨中磷灰石微晶类似的羟基磷灰石纳米粒子与可降解聚酯材料进行复合,能够得到具有优越骨诱导性能并且能够降解的新型骨修复材料。这方面的研究代表了有机／无机复合生物材料领域新的发展方向。     

羟基磷灰石/丝素蛋白复合纤维的制备及其矿化研究

在以静电纺丝法制备羟基磷灰石(HAP)/丝素蛋白(SF)复合纤维的前提下, 采用同轴共纺法获得了以HAP为“芯”、SF为“皮”的双组分电纺纤维(电纺膜), 并通过扫描和透射电镜、红外光谱以及X射线衍射等手段对电纺纤维进行了表征. 结果表明, HAP均存在于上述两种方法制备的纳米纤维中, 但同轴共纺法不仅可以避免HAP/SF共混电纺时pH值对丝素蛋白结构的影响, 并且能大大提高电纺膜中HAP的含量. 同时, 我们还分别以SF纤维、HAP/SF复合纤维和HAP/SF“皮-芯”纤维作为有机基质, 对羟基磷灰石在其上的矿化过程进行了探索, 结果表明含较多羟基磷灰石的HAP/SF“皮-芯”纤维更有利于矿化的进行.