Poly(lactic acid) porous scaffold with calcium phosphate mineralized surface and bone marrow mesenchymal stem cell growth and differentiation

This work aims to modify the surface of a poly(lactic acid) (PLA) porous scaffold with calcium phosphate (CaP) via a simple solution-based technique, and to evaluate the effects of this modification on the responses of rat bone marrow mesenchymal stem cells (rBMMSCs). Under appropriate modification conditions involving stepwise-treatments in the Ca-and-P supersaturated solution under gentle agitation, a thin, poorly crystallized CaP layer was deposited. The BMMSCs derived from adult rats were shown to adhere quite well to the CaP-coated scaffold, and to proliferate actively with culturing time, although some down-regulation was noted with regard to the unmodified PLA scaffold. The osteogenic differentiation of rBMMSCs was significantly higher on the CaP-modified scaffold than on the unmodified scaffold, as confirmed by alkaline phosphatase (ALP) activity. Moreover, the expression of genes associated with bone, including collagen type I, osteopontin and bone sialoprotein, was stimulated better on the CaP-modified PLA scaffold. Based on these results, the currently used CaP-treatment was deemed effective in stimulating the osteogenic development of rBMMSCs on the PLA-based scaffold, and the CaP-treated PLA scaffold may be useful for future bone tissue engineering.     

Genomic expression of mesenchymal stem cells to altered nanoscale topographies.

The understanding of cellular response to the shape of their environment would be of benefit in the development of artificial extracellular environments for potential use in the production of biomimetic surfaces. Specifically, the understanding of how cues from the extracellular environment can be used to understand stem cell differentiation would be of special interest in regenerative medicine.In this paper, the genetic profile of mesenchymal stem cells cultured on two osteogenic nanoscale topographies (pitted surface versus raised islands) are compared with cells treated with dexamethasone, a corticosteroid routinely used to stimulate bone formation in culture from mesenchymal stem cells, using 19k gene microarrays as well as 101 gene arrays specific for osteoblast and endothelial biology.The current studies show that by altering the shape of the matrix a cell response (genomic profile) similar to that achieved with chemical stimulation can be elicited. Here, we show that bone formation can be achieved with efficiency similar to that of dexamethasone with the added benefit that endothelial cell development is not inhibited. We further show that the mechanism of action of the topographies and dexamethasone differs. This could have an implication for tissue engineering in which a simultaneous, targeted, development of a tissue, such as bone, without the suppression of angiogenesis to supply nutrients to the new tissue is required. The results further demonstrate that perhaps the shape of the extracellular matrix is critical to tissue development.     

The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder

A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.     

The fabrication of the antibacterial paste based on TiO2 nanotubes and Ag nanoparticles-loaded TiO2 nanotubes powders

ABSTRACT

We successfully synthesised TiO₂ nanotubes (TNTs) and silver nanoparticles (Ag NPs)-loaded TiO₂ nanotubes paste. These were coated on a glass substrate by spin coating method, and their antibacterial activities were surveyed. The morphology of materials was defined by transmission electron microscopy (TEM) image; the crystalline structure and the composition of the materials were determined by X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS). Vibrational properties of the molecules existing in the sample were investigated by Fourier transform infrared (FTIR) spectroscopy, and the transmittances of films were determined by UV–Vis transmittance spectroscopy. This research shows that the structure and morphology of TNTs did not change after they underwent the processes of paste preparing and film coating on a glass substrate. Furthermore, the transmittance of TNTs film (about 75%) is higher than Ag NPs-loaded TiO₂ nanotubes (Ag/TNTs) film (about 65%) in the visible region. Moreover, the antibacterial property of Ag/TNTs film shows its effectiveness against Escherichia coli bacteria, and the antibacterial efficiency is 99.06% for 24 h-incubation period in the dark condition.     

Antibacterial and photocatalytic activities of TiO2 nanotubes

TiO₂ nanotubes have been prepared by anodisation of titanium foil and their antibacterial activities have been tested against Gram-positive bacteria (Bacillus atrophaeus) while photocatalytic activity was tested for the degradation of the methyl orange dye. We found that the annealing temperature strongly affected antibacterial activity and photocatalytic dye degradation, as well as the production of reactive oxygen species under illumination. However, different trends were observed for dye degradation and antibacterial activity dependence on the annealing temperature. The relationship between annealing conditions, crystal structure, reactive oxygen species generation, dye degradation and antibacterial activity is discussed.     

Influence of Na+ content on the structure and morphology of TiO2 nanoparticles prepared by hydrothermal transformation of alkaline titanate nanotubes

ABSTRACT

The objective of this study is to investigate the role of Na⁺ content in the morphology evolution of TiO₂ nanoparticles prepared by hydrothermal approach. Various TiO₂ morphology from 0-dimensional (0D) nanoparticles to 1-dimensional (1D) nanorods were synthesised by hydrothermally treating the alkali titanate nanotubes with different Na⁺ content. The XRD patterns show the phase transformation and crystallographic nature of alkali titanate nanotubes are strongly dependent on the Na⁺ content, the cation exchange of Na⁺ by H⁺ ion exchange affects the crystallinity of the tubes and causes disorder of the interlayers of nanotubes. The SEM and TEM images confirm that Na⁺ rich titanate nanotubes were thermally stable. Moreover, BET measurements revealed that the Na⁺ content plays an important role on the specific surface area of formed TiO₂ nanoparticles. The photocatalytic activity of the TiO₂ nanoparticles was characterised via the decomposition rate of an aqueous solution of methyl orange (MO) under UV light irradiation. The TiO₂ nanoparticles prepared by hydrothermally treating the alkali titanate nanotubes with no Na⁺ content has a surface area of 55.1 m²/g with nearly 100% photodecomposition of MO in 20 min.     

Direct imaging of titania nanotubes located in mouse neural stem cell nuclei

Titania nanotubes (TiO₂-NTs) are a potential drug vehicle for use in nanomedicine. To this end, a preliminary study of the interaction of a model cell with TiO₂-NTs has been carried out. TiO₂-NTs were first conjugated with a fluorescent label, fluorescein isothiocyanate (FITC). FITC-conjugated titania nanotubes (FITC-TiO₂-NTs) internalized in mouse neural stem cells (NSCs, line C17.2) can be directly imaged by confocal microscopy. The confocal imaging showed that FITC-TiO₂-NTs readily entered into the cells. After co-incubation with cells for 24 h, FITC-TiO₂-NTs localized around the cell nucleus without crossing the karyotheca. More interestingly, the nanotubes passed through the karyotheca entering the cell nucleus after co-incubation for 48 h. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were also employed in tracking the nanotubes in the cell. These results will be of benefit in future studies of TiO₂-NTs for use as a drug vehicle, particularly for DNA-targeting drugs. This article is published with open access at Springerlink.com     

矿化柞蚕丝胶膜表面粗糙度的调控及其对骨髓间充质干细胞生长行为的影响

生物材料表面的粗糙度是影响细胞行为的重要因素之一。为了调控丝蛋白生物材料表面的粗糙度,并评价材料表面粗糙度对细胞生长行为的影响,首先,通过湿化学共沉淀法,以柞蚕丝胶(AS)溶液为模板,诱导了羟基磷灰石(HAp)晶体成核,进而调控了AS膜表面的粗糙度。然后,采用SEM、粗糙仪、FTIR及EDX等对HAp/AS复合膜表面形貌、粗糙度及成分进行了表征。最后,通过SEM和CellTiter 96?AQueous单溶液细胞增殖检测试剂盒(MTS)检测了骨髓间充质干细胞(BMSCs)在HAp/AS复合膜表面的形貌及增殖率。结果表明:纯AS膜的表面粗糙度为0.15μm,矿化1、8及24h后,表面粗糙度分别为0.38、0.46和1.20μm;矿化24h后,在HAp/AS复合膜表面可观察到直径为30~80nm的球状复合物,生成的矿化物为HAp;HAp/AS复合膜具有良好的细胞相容性,表面粗糙度为1.20μm的复合膜能够显著促进BMSCs的增殖,粗糙度对BMSCs在HAp/AS复合膜表面的粘附和形貌有着重要的影响。因此,可通过矿化的方法在生物大分子表面诱导HAp晶体的成核与生长,从而调控材料的表面粗糙度,研究材料界面上的细胞行为。     

多壁纳米碳管的制备与表面改性处理

以Co-MCM-41作催化剂,采用化学气相沉积(CVD)法催化热解无水乙醇制备纳米碳管(CNTs),然后将纳米碳管在120℃下用浓硝酸回流,进行纯化及表面酸氧化改性处理。通过XRD、FT-IR、TEM、N2吸附-脱附和Raman光谱等分析手段对酸处理前后的纳米碳管进行了表征。结果表明制备出品质较好、管径均匀、管壁较厚、顶端开口的多壁纳米碳管。浓硝酸氧化处理后在纳米碳管的表面存在羧基和羟基等官能团。     

Biomaterials control of pluripotent stem cell fate for regenerative therapy

Pluripotent stem cells (PSCs) derived from either the embryo or reprogramming processes have the capacity to self-renew and differentiate into various cells in the body, thereby offering a valuable cell source for regenerative therapy of intractable disease and serious tissue damage. Traditionally, methods to expand and differentiate PSCs have been confined to 2D culture through the use of biochemical signals; the use of biomaterials beyond the commercially available culture dish has not been widespread. Nevertheless, biomaterials with tailored physical, chemical, and geometrical cues can mimic the native stem cell niche to tune the microenvironmental conditions for PSCs to preserve their self-renewal capacity or to switch their phenotype, a status ultimately needed to gain regenerative functions ex vivo and in vivo. Recently efforts to explore biomaterials to regulate PSC behavior have accelerated. The biomaterials properties investigated include surface chemistry, immobilized ligand, nano-/micro-topography, matrix stiffness, geometrical complexity, 3D configuration, and combinations thereof. This review aims to cover the current advances of biomaterials-based control over PSCs, particularly for the preservation of self-renewal capacity as well as for their differentiation into target cells. Furthermore, it aims to suggest future research directions that would facilitate the eventual translation of these advances.     

Collagen gel three-dimensional matrices combined with adhesive proteins stimulate neuronal differentiation of mesenchymal stem cells

Three-dimensional gel matrices provide specialized microenvironments that mimic native tissues and enable stem cells to grow and differentiate into specific cell types. Here, we show that collagen three-dimensional gel matrices prepared in combination with adhesive proteins, such as fibronectin (FN) and laminin (LN), provide significant cues to the differentiation into neuronal lineage of mesenchymal stem cells (MSCs) derived from rat bone marrow. When cultured within either a three-dimensional collagen gel alone or one containing either FN or LN, and free of nerve growth factor (NGF), the MSCs showed the development of numerous neurite outgrowths. These were, however, not readily observed in two-dimensional culture without the use of NGF. Immunofluorescence staining, western blot and fluorescence-activated cell sorting analyses demonstrated that a large population of cells was positive for NeuN and glial fibrillary acidic protein, which are specific to neuronal cells, when cultured in the three-dimensional collagen gel. The dependence of the neuronal differentiation of MSCs on the adhesive proteins containing three-dimensional gel matrices is considered to be closely related to focal adhesion kinase (FAK) activation through integrin receptor binding, as revealed by an experiment showing no neuronal outgrowth in the FAK-knockdown cells and stimulation of integrin β1 gene. The results provided herein suggest the potential role of three-dimensional collagen-based gel matrices combined with adhesive proteins in the neuronal differentiation of MSCs, even without the use of chemical differentiation factors. Furthermore, these findings suggest that three-dimensional gel matrices might be useful as nerve-regenerative scaffolds.     

表达绿色荧光蛋白基因的花鲈胚胎干细胞株的建立及其体外分化

以带有绿色荧光标记的基因(pCMV-EGFP)为报告基因,用Genejammer、Genejuice和Metafectene三种脂质体介导花鲈胚胎干细胞(LJES1)的基因转移.实验发现,Genejammer介导的细胞转化效率最高,高达27.3%,其余分别为12.1%和5.3%.转移绿色荧光蛋白(GFP)基因的LJES1细胞经过药物筛选和单克隆化培养,获得了表达GFP基因的阳性克隆细胞株,经PCR对GFP阳性细胞株的基因组DNA及提取的RNA扩增,获得了目的条带,证实了GFP基因已经整合到LJES1细胞的基因组中,并获得了正常的表达.通过体外诱导,GFP阳性细胞能够分化为神经细胞、肌肉细胞、成纤维细胞等,用悬滴法培养获得了GFP阳性细胞的拟胚体,证实了经过长期的药物筛选后,LJES1细胞仍然保持着发育的多能性.这一研究,为进一步利用海水鱼类胚胎干细胞进行遗传操作及基因工程的研究提供了方法上的探索.     

Integrating concepts of material mechanics,ligand chemistry,dimensionality and degradation to control differentiation of mesenchymal stem cells

The role of substrate mechanics in guiding mesenchymal stem cell (MSC) fate has been the focus of much research over the last decade. More recently, the complex interplay between substrate mechanics and other material properties such as ligand chemistry and substrate degradability to regulate MSC differentiation has begun to be elucidated. Additionally, there are several changes in the presentation of these material properties as the dimensionality is altered from two- to three-dimensional substrates, which may fundamentally alter our understanding of substrate-induced mechanotransduction processes. In this review, an overview of recent findings that highlight the material properties that are important in guiding MSC fate decisions is presented, with a focus on underlining gaps in our existing knowledge and proposing potential directions for future research.     

离子种类对金属掺杂纳米管TiO_2光催化活性的影响

使用市售Degussa P-25TiO2粉末,采用水热合成法制备了1.0%(原子分数)Ag+、Cu2+、Fe3+、Mn2+和V5+掺杂纳米管TiO2催化剂。结果表明,随着煅烧温度增高,样品的比表面积逐渐降低,锐钛矿含量先增后减,禁带宽度逐渐变窄,变化范围与掺杂金属的种类有关。掺杂金属后,纳米管TiO2催化剂的比表面积略有降低,锐钛矿含量略有增大,禁带宽度变窄。向纳米管TiO2中掺杂Ag+、Cu2+、Fe3+和V5+,催化剂的光催化活性提高,而掺杂Mn2+,光催化活性略有降低。550℃煅烧1.0%Fe3+掺杂纳米管TiO2具有最好的催化效果,其254nm光催化臭氧氧化对腐植酸的去除率为77.4%。     

Growth of carbon nanotubes directly on a nickel surface by thermal CVD

A simple method of growing carbon nanotubes directly on nickel substrate without chemical pretreatment is reported. It is demonstrated that carbon nanotubes growth is directly affected by the roughness on the surface. Carbon nanotubes density is large in each growth zone observed on the surface; these zones being spread sparsely for coarse roughness of the surface. The density of carbon nanotubes decreases and the number of growth zones increases as the roughness on the surface is reduced. The above trend was not affected with C₂H₂ flow time changing from 10 to 2 min. A similar result was obtained using a Ni alloy as substrate, but the effect of surface roughness on the growth of CNTs was less pronounced. The CNTs grown on the Ni alloy were free of amorphous carbon and uniformly distributed.     

Neurogenic differentiation of human umbilical cord mesenchymal stem cells on aligned electrospun polypyrrole/polylactide composite nanofibers with electrical stimulation

Adult central nervous system (CNS) tissue has a limited capacity to recover after trauma or disease. Recent medical cell therapy using polymeric biomaterialloaded stem cells with the capability of differentiation to specific neural population has directed focuses toward the recovery of CNS. Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal cells. Here we report on the fabrication of an electrospun polypyrrole/polylactide composite nanofiber film that direct or determine the fate of mesenchymal stem cells (MSCs), via combination of aligned surface topography, and electrical stimulation (ES). The surface morphology, mechanical properties and electric properties of the film were characterized. Comparing with that on random surface film, expression of neurofilament-lowest and nestin of human umbilical cord mesenchymal stemcells (huMSCs) cultured on film with aligned surface topography and ES were obviously enhanced. These results suggest that aligned topography combining with ES facilitates the neurogenic differentiation of huMSCs and the aligned conductive film can act as a potential nerve scaffold.