Surface modification of starch based blends using potassium permanganate-nitric acid system and its effect on the adhesion and proliferation of osteoblast-like cells

The surface modification of three starch based polymeric biomaterials, using a KMnO₄/NHO₃ oxidizing system, and the effect of that modification on the osteoblastic cell adhesion has been investigated. The rationale of this work is as follows—starch based polymers have been proposed for use as tissue engineering scaffolds in several publications. It is known that in biodegradable systems it is quite difficult to have both cell adhesion and proliferation. Starch based polymers have shown to perform better than poly-lactic acid based materials but there is still room for improvement. This particular work is aimed at enhancing cell adhesion and proliferation on the surface of several starch based polymer blends that are being proposed as tissue engineering scaffolds.The surface of the polymeric biomaterials was chemically modified using a KMnO₄/HNO₃ system. This treatment resulted in more hydrophilic surfaces, which was confirmed by contact angle measurements. The effect of the treatment on the bioactivity of the surface modified biomaterials was also studied. The bioactivity tests, performed in simulated body fluid after biomimetic coating, showed that a dense film of calcium phosphate was formed after 30 days. Finally, human osteoblast-like cells were cultured on unmodified (control) and modified materials in order to observe the effect of the presence of higher numbers of polar groups on the adhesion and proliferation of those cells. Two of the modified polymers presented changes in the adhesion behavior and a significant increase in the proliferation rate kinetics when compared to the unmodified controls.     

生物材料细胞粘附肽仿生修饰的研究进展

RGD(Arg-G1y-Asp)短肽序列是一种细胞粘附肽,能被细胞膜上的整合素识别,参与细胞与基质间的粘附.为改善合成生物材料缺乏细胞识别信号的缺点,可将含RGD序列肽经本体或表面修饰引入材料,使材料具有良好的细胞亲和性.综述了采用含RGD肽对各种合成生物材料进行仿生修饰的研究进展.     

聚乳酸接枝多糖类生物仿生材料的研究进展

聚乳酸与多糖都是生物可降解、生物相容性材料,将聚乳酸的力学性能优越性和多糖的生物学优越性能综合利用起来,设计生物仿生材料是一种制备生物医用材料的新手段。文中综合讨论了聚乳酸与多糖接枝改性的最新研究进展,同时对于这类生物仿生材料目前存在的问题以及前景进行了评估。     

A novel strategy to graft RGD peptide on biomaterials surfaces for endothelization of small-diamater vascular grafts and tissue engineering blood vessel

To improve the performance of small-diamater vascular grafts, endothelization of biomaterials surfaces and tissue engineering are more promising strategies to fabricate small-diamater vascular grafts. In this study, a Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) peptide was grafted on the surfaces of poly(carbonate urethane)s (PCUs), with photoactive 4-benzoylbenzoic acid (BBA) by UV irradiation. The photoactive peptides (BBM-GRGDSP) were synthesized with classical active ester of peptide synthesis. The modified surfaces of PCU with the photoactive RGD peptides were characterized by water contact angle measurement and X-ray Photoelectron Spectroscopy (XPS), which results suggested that the peptides were successfully grafted on the PCU surfaces. The effect of these modified surfaces on endothelial cells (ECs) adhesion and proliferation was examined over 72 h. PCU surfaces coupled with the synthetic photoactive RGD peptides, as characterized with phase contrast microscope and the metabolic activity (MTT) assay enhanced ECs proliferation and spreading with increasing concentration of RGD peptides grafted on their surfaces. Increased retention of ECs was also observed on the polymers surfaces under flow shear stress conditions. The results demonstrated that GRGDSP peptides grafted on the surfaces of polymers with photoactive 4-benzoylbenzoic acids could be an efficient method of fabrication for artificial small-diamater blood vessels. The modified polymer is expected to be used for small-diamater vascular grafts and functional tissue engineered blood vessels to improve ECs adhesion and retention on the polymer surfaces under flow shear stress conditions.     

Biomimetic coatings functionalized with adhesion peptides for dental implants

A complete biological integration into the surrounding tissues (bone, gingiva) is a critical step for clinical success of a dental implant. In this work biomimetic coatings consisting either of collagen type I (for the gingiva region) and hydroxyapatite (HAP) or mineralized collagen (for the bone interface) have been developed as suitable surfaces regarding the interfaces. Additionally, using these biomimetic coatings as a matrix, adhesion peptides were bound to further increase the specificity of titanium implant surfaces. To enhance cell attachment in the gingiva region, a linear adhesion peptide developed from a laminin sequence (TWYKIAFQRNRK) was bound to collagen, whereas for the bone interface, a cyclic RGD peptide was bound to HAP and mineralized collagen using adequate anchor systems. The biological potential of these coatings deduced from cell attachment experiments with HaCaT human keratinocytes and MC3T3-E1 mouse osteoblasts showed the best results for collagen and laminin sequence coating for the gingiva region and mineralized collagen and RGD peptide coatings for regions with bone contact. Our concept opens promising approaches to improve the biological integration of dental implants.     

仿生无机材料在石质文物保护中的应用

90年代,出现了一种模拟生物矿化中无机物在有机物调制下形成过程的合成技术-仿生合成.仿生无机材料是一种具有特殊化学和物理性能的新型材料,现已越来越广泛地应用于医学材料、纳米材料、薄膜材料和多孔材料等领域.由于仿生无机材料潜在广阔的应用空间,使得仿生合成无机材料技术成为材料化学研究的热点.本文介绍了仿生合成技术的基础理论和目前仿生无机材料的应用领域.分析了仿生无机材料在石质文物保护应用中的可行性及优越性,表明是一种很有潜力的新型保护材料.     

RGD修饰钛表面对人牙龈成纤维细胞初期黏附和铺展的影响

用羰基二咪唑(1,1'-carbonyldiimidazole,CDI)将含RGD的短肽共价连接到纯钛表面,研究接枝后的钛表面对原代培养的人牙龈成纤维细胞(human gingival fibroblasts,HGF)初期黏附和铺展的影响.结果表明,RGD修饰的纯钛表面粘附的细胞数比未修饰钛表面多,细胞铺展面积比钛表面的大,应力纤维的形成比钛表面早.RGD接枝钛表面更有利于人牙龈成纤维细胞的粘附,改善了纯钛的生物相容性.     

仿生有序结构羟基磷灰石研究进展

羟基磷灰石(hydroxyapatite,HAP)与人体硬组织主要无机组分具有相同的化学组成,因而被认为具备良好的生物相容性、可降解性和生物活性,并已在生物医学领域得到广泛应用。迄今为止,形态丰富的HAP纳米材料及其合成方法已经被报道出来,但是具有仿生有序结构的HAP材料及其制备方法仍然是相关领域最具挑战性的方向。在包括牙釉质、皮质骨和松质骨在内的硬组织中,纳米尺度的HAP通常会按照人体受力分布情况呈可控有序结构排列。因此,通过仿生天然硬组织微结构实现HAP的可控有序组装,有望进一步提升传统HAP基生物材料的力学和生物学性能。近年来,包括氧化铝模板法、有机溶剂/小分子调控法、磷酸氢钙相转化法、高分子/蛋白分子诱导矿化法、冷冻铸造等在内的HAP有序结构制备方法已经被发展出来,并实现了在纳米、微米等尺度上有序结构的制备。最近,作者课题组报道了HAP纳米线的扩大化溶剂热制备方法,并进一步提出了适用于控制HAP纳米线有序排列的表面小分子介导的液相自组装策略,获得了尺寸和方向均可控的宏观尺度HAP纳米线仿生有序结构。相比于传统无序结构HAP基生物材料,具有仿生有序结构的HAP表现出了良好的力学和生物学性能,对新型无机生物材料的设计、制备及其生物医学应用研究具有重要的指导意义。综述了仿生有序结构HAP的研究进展,包括其结构组成、合成方法及调控机制,最后总结了仿生有序结构HAP研究领域当前面临的挑战以及未来的发展前景。     

新型石质文物保护材料的应用探索

目前应用于石质文物保护的材料有很多种,对文物的保护起到了一定的效果,但是也存在许多问题.本文对有特殊性能的有机氟聚合物材料、纳米材料和仿生无机材料在石质文物保护中的探索研究进行了介绍,表明它们是很有潜力的新型石质文物保护材料.     

Analysis of cell binding and internalization of multivalent PEG-based gene delivery vehicles

RGD peptides have been incorporated into several gene delivery vehicles to enhance specific interactions of nonviral vehicles with the cell surface. However, there are contradictory results regarding the effect of linear RGD peptides on specific cell surface binding of polyethylene glycol (PEG)-conjugated gene delivery vehicles. This study sought to understand how coupling RGD peptides to PEG vehicles affects cell binding and internalization using a novel four arm PEG backbone. Coupling multiple RGD peptides to the PEG backbone increased the affinity of the vehicle for the cell surface, and that the PEG backbone did not reduce the affinity of RGD peptides for integrin receptors in both kinetic and equilibrium studies. Kinetic studies suggest that cellular internalization of PEG-based vehicles is not regulated by the RGD peptides on the vehicle, but rather by nonspecific interactions with heparan sulfate proteoglycans either alone or in combination with integrins. These results suggest that while increasing the number of RGD peptides per vehicle increases cell binding, but it does not contribute to increased internalization or transfection efficiency.     

Ligand density-dependent influence of arginine–glycine–aspartate functionalized gold nanoparticles on osteogenic and adipogenic differentiation of mesenchymal stem cells

Extracellular matrix (ECM) plays a very important role in regulating cell function and fate. It is highly desirable to fabricate biomimetic models to investigate the role of ECM in stem cell differentiation. In this study, arginine–glycine–aspartate (RGD)-modified gold nanoparticles (Au NPs) with tunable surface ligand density were prepared to mimic the ECM microenvironment. Their effect on osteogenic and adipogenic differentiation of human mesenchymal stem cells (MSCs) was investigated. The biomimetic Au NPs were taken up by MSCs in a ligand density-dependent manner. The biomimetic NPs with a high RGD density had an inhibitive effect on the alkaline phosphatase (ALP) activity, calcium deposition, and osteogenic marker gene expression of MSCs. Their effect on oil droplet formation and adipogenic marker gene expression was negative when RGD density was low, while their effect was promotive when RGD density was high. The biomimetic Au NPs regulated the osteogenic and adipogenic differentiation of MSCs mainly through affecting the focal adhesion and cytoskeleton. This study highlights the roles of biomimetic NPs on stem cell differentiation that could provide a meaningful strategy in fabricating functional biomaterials for tissue engineering and biomedical applications.

Open image in new window

     

Investigations on the in vitro bioactivity of swift heavy oxygen ion irradiated hydroxyapatite

Poly(propylene fumarate) (PPF) is an ultraviolet-curable and biodegradable polymer with potential applications for bone regeneration. In this study, we designed and fabricated three-dimensional (3D) porous scaffolds based on a PPF polymer network using micro-stereolithography (MSTL). The 3D scaffold was well fabricated with a highly interconnected porous structure and porosity of 65%. These results provide a new scaffold fabrication method for tissue engineering. Surface modification is a commonly used and effective method for improving the surface characteristics of biomaterials without altering their bulk properties that avoids the expense and long time associated with the development of new biomaterials. Therefore, we examined surface modification of 3D scaffolds by applying accelerated biomimetic apatite and arginine-glycine-aspartic acid (RGD) peptide coating to promote cell behavior. The apatite coating uniformly covered the scaffold surface after immersion for 24 h in 5-fold simulated body fluid (5SBF) and then the RGD peptide was applied. Finally, the coated 3D scaffolds were seeded with MC3T3-E1 pre-osteoblasts and their biologic properties were evaluated using an MTS assay and histologic staining. We found that 3D PPF/diethyl fumarate (DEF) scaffolds fabricated with MSTL and biomimetic apatite coating can be potentially used in bone tissue engineering.     

Stem cells and biomimetic materials strategies for tissue engineering

Stem cells have been recognized as a promising alternative to somatic cells in the application of cell therapy owing to their potential to renew themselves through cell division and to differentiate into a wide range of specialized cell types. In order to maintain the phenotype expression and differentiated functions of stem cells, the simulated natural environment of the biomimetic material support has to provide the appropriate signals to the attached cells. Scaffolds with biomimetic components and nanotexture can provide chemical, physical as well as spatial cues that are essential to mimic natural tissue growth. Moreover, the plasticity of stem cells provides the basic possibility for multiple-tissue engineering using a certain type of stem cells. Progress in the understanding of self-renewal and directed differentiation of stem cells on biomimetic materials will lead scientists to propose the possibility of cell-based therapies to treat diseases, including the use of stem cells in tissue engineering. In this review paper, we will discuss the current state of the art and future perspectives on stem cells and biomimetic materials strategies for tissue engineering.     

Modulation of Lumen Formation by Microgeometrical Bioactive Cues and Migration Mode of Actin Machinery

How endothelial cells (ECs) express the particular filopodial or lamellipodial form of the actin machinery is critical to understanding EC functions such as angiogenesis and sprouting. It is not known how these mechanisms coordinately promote lumen formation of ECs. Here, adhesion molecules (RGD peptides) and inductor molecules (BMP‐2 mimetic peptides) are micropatterned onto polymer surfaces by a photolithographic technique to induce filopodial and lamellipodial migration modes. Firstly, the effects of peptide microgeometrical distribution on EC adhesion, orientation and morphogenesis are evaluated. Large micropatterns (100 μm) promote EC orientation without lumen formation, whereas small micropatterns (10–50 μm) elicit a collective cell organization and induce EC lumen formation, in the case of RGD peptides. Secondly, the correlation between EC actin machinery expression and EC self‐assembly into lumen formation is addressed. Only the filopodial migration mode (mimicked by RGD) but not lamellipodial migration mode (mimicked by BMP‐2) promotes EC lumen formation. This work gives a new concept for the design of biomaterials for tissue engineering and may provide new insight for angiogenesis inhibition on tumors.     

Synthesis and characterization of matrix metalloprotease sensitive-low molecular weight hyaluronic acid based hydrogels

Hyaluronic acid is a naturally derived glycosaminoglycan (GAG) involved in biological processes. A low molecular weight hyaluronic acid (50 kDa)-based hydrogel was synthesized using acrylated hyaluronic acid. Matrix metalloproteinase (MMP) sensitive hyaluronic acid-based hydrogels were prepared by conjugation with two different peptides: cell adhesion peptides containing integrin binding domains (Arg-Gly-Asp: RGD) and a cross-linker with MMP degradable peptides to mimic the remodeling characteristics of natural extracellular matrices (ECMs) by cell-derived MMPs. Mechanical properties of these hydrogels were evaluated with different molecular weights of acrylated hyaluronic acid (10 kDa and 50 kDa) cross-linked by MMP sensitive peptides by measuring elastic modulus, viscous modulus, swelling ratio and degradation rate. The MMP sensitive hydrogel based on the 50 kDa hyaluronic acid showed a 31.5-fold shorter gelation time, 4.7-fold higher storage modulus and 0.51-fold smaller swelling ratio than those of the hydrogel based on the 10 kDa. Degradation rate was dependent on MMP sensitivity of the peptide cross-linker. MMP sensitive hyaluronic acid based hydrogels were degraded faster than MMP insensitive-hyaluronic acid-based hydrogels. Human mesenchymal stem cells (MSCs) were cultured in MMP-sensitive or insensitive hyaluronic acid-based hydrogels (50 kDa hyaluronic acid) and/or immobilized cell adhesive RGD peptides. Cells cultured in the MMP-sensitive hydrogel with RGD peptides showed dramatic cell spreading compared with that of the control, which remained round. This MMP-sensitive low molecular weight hyaluronic acid-based hydrogel could be useful in tissue engineering by improving tissue defect regeneration and tissue remodeling.     

Hyaluronic acid hydrogel immobilized with RGD peptides for brain tissue engineering

In this paper, hyaluronic acid hydrogels with open porous structure have been developed for scaffold of brain tissue engineering. A short peptide sequence of arginine–glycine–aspartic acid (RGD) was immobilized on the backbone of the hydrogels. Both unmodified hydrogels and those modified with RGD were implanted into the defects of cortex in rats and evaluated for their ability to improve tissue reconstruction. After 6 and 12 weeks, sections of brains were processed for DAB and Glees staining. They were also labeled with GFAP and ED1 antibodies, and observed under the SEM for ultrastructral examination. After implanting into the lesion of cortex, the porous hydrogels functioned as a scaffold to support cells infiltration and angiogenesis, simultaneously inhibitting the formation of glial scar. In addition, HA hydrogels modified with RGD were able to promote neurites extension. Our experiments showed that the hyaluronic acid-RGD hydrogel provided a structural, three-dimensional continuity across the defect and favoured reorganization of local wound-repair cells, angiogenesis and axonal growth into the hydrogel scaffold, while there was little evidence of axons regeneration in unmodified hydrogel.     

Towards understanding biomineralization: calcium phosphate in a biomimetic mineralization process

Abstract Biomineralization processes result in organic/inorganic hybrid materials with complex shapes, hierarchical structures, and superior material properties. Recent developments in biomineralization and biomaterials have demonstrated that calcium phosphate particles play an important role in the formation of hard tissues in nature. In this paper, current concepts in biomineralization, such as nano assembly, biomimetic shell structure, and their applications are introduced. It is confirmed experimentally that enamel- or bone-liked apatite can be achieved by oriented aggregations using nano calcium phosphates as starting materials. The assembly of calcium phosphate can be either promoted or inhibited by different biomolecules so that the kinetics can be regulated biologically. In this paper, the role of nano calcium phosphate in tissue repair is highlighted. Furthermore, a new, interesting result on biomimetic mineralization is introduced, which can offer an artificial shell for living cells via a biomimetic method.     

聚合物在生物传感器中的应用研究进展

综述了近年来高分子材料在生物传感器的应用研究进展，介绍了高分子复合物，水凝胶，溶胶－凝胶，改性聚合物，电生聚合物，氧化还原聚合物，离子交换聚合物和具有特殊结构的聚合物在酶和电子媒介体固定化方面的应用以及由其制备的生物传感器的性能，对应用于生物传感器的高分子材料的分类，制备方法和原理及其特性进行了深入的探讨，并指出了目前其存在的主要问题及解决方法，对高分子材料在生物传感器中的应用前景予以展望。     

Grafting RGD containing peptides onto hydroxyapatite to promote osteoblastic cells adhesion

Ceramics possess osteoconductive properties but exhibit no intrinsic osteoinductive capacity. Consequently, they are unable to induce new bone formation in extra osseous sites. In order to develop bone substitutes with osteogenic properties, one promising approach consists of creating hybrid materials by associating in vitro biomaterials with osteoprogenitor cells. With this aim, we have developed a novel strategy of biomimetic modification to enhance osseointegration of hydroxyapatite (HA) implants. RGD-containing peptides displaying different conformations (linear GRGDSPC and cyclo-DfKRG) were grafted onto HA surface by means of a three-step reaction procedure: silanisation with APTES, cross-linking with N-succinimidyl-3-maleimidopropionate and finally immobilisation of peptides thanks to thiol bonding. Whole process was performed in anhydrous conditions to ensure the reproducibility of the chemical functionalisation. The three-step reaction procedure was characterised by high resolution X-ray photoelectron spectroscopy. Efficiency of this biomimetic modification was finally demonstrated by measuring the adhesion of osteoprogenitor cells isolated from HBMSC onto HA surface.     

Engineering the morphology of a self-assembling protein fibre

Biological assemblies provide inspiration for the development of new materials for a variety of applications. Our ability to realize this potential, however, is hampered by difficulties in producing and engineering natural biomaterials, and in designing them de novo. We previously described a self-assembling system comprising two short complementary segments of straight synthetic polypeptides (termed standards in this report). Their interaction results in the formation of long fibres--about 50 nm in diameter--that extend straight and without branching for tens to hundreds of micrometres. Our aim is to influence and, ultimately, to control fibre morphology. Here, we show that the standard peptides can be supplemented with special peptides to effect morphological changes in the fibres. Specifically, we created half-sized subunits of the standard peptides, which were combined to make nonlinear peptides. When mixed with the standard peptides, these nonlinear peptides produced kinked, waved and branched fibres. We related the numbers of these features to the special/standard ratios empirically. Furthermore, the extent and frequency of kinking was altered by changing the standard-fibre background: more kinking was observed in a background of thinner, less-stable fibres. The ability to perform such transformations holds promise for bottom-up assembly and engineering responsive biomimetic materials for applications in surface and tissue engineering.