载人航天任务二氧化碳吸附技术现状与发展

CO2吸附技术是载人航天中重要的生命保障技术。介绍了常见的密闭空间CO2吸附技术,并阐述了近年来国内外吸附技术的研究方向。首先介绍了五种常见的CO2吸附方式,并对四床分子筛的工作过程进行了较为详细的阐述。之后提到了两种新型的吸附剂,并展望了两种新型吸附剂在CO2去除组件以及系统集成中的应用价值。

Effects of Nanometer Hydroxyapatite on Proliferation of Periodontal Ligament Fibroblasts

Objective:To investigate possible effects of nanophase powder of hydroxyapatite on proliferation of periodontal ligament cells. Methods: With sol-gel method, the nanophase hydroxyapatite powders were fabricated. These powders were proved nanopaticles by transmission electron microscope. The effects on proliferation of periodontal ligament cell(PDLC) were observed in vitro with MTT [3-(4,5dimethylthiazo;-2-yl)-2,5-diphenytetralium bromide] method. Results: On the 2nd,3rd,4th day after treated with nanoparticles of hydroxyapatite, the proliferate activity of the PDLC increases significantly, compared with those with dense hydroxyaoatite and control but no significant difference could be found between the dense hydroxyapatite and the control. Conclusion: Nanophase hydroxyapatite can promote the regeneration of periodontal tissue.

Tethering of Gly-Arg-Gly-Asp-Ser-Pro-Lys Peptides on Mg-Doped Hydroxyapatite

Stem cell homing, namely the recruitment of mesenchymal stem cells （MSCs） to injured tissues, is highly effective for bone regeneration in vivo. In order to explore whether the incorporation of mimetic peptide sequences on magnesium-doped （Mg-doped） hydroxyapatite （HA） may regulate the homing of MSCs, and thus induce cell migration to a specific site, we covalently functionalized MgHA disks with two chemotactic/haptotactic factors： either the fibronectin fragment III1-C human （FF III1-C）, or the peptide sequence Gly-Arg-Gly-Asp-Ser-Pro-Lys, a fibronectin analog that is able to bind to integrin trans- membrane receptors. Preliminary biological evaluation of MSC viability, analyzed by 3-（4,5-dimethyl- thiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） test, suggested that stem cells migrate to the MgHA disks in resoonse to the grafted haototaxis stimuli.

Polymeric nanocomposites loaded with fluoridated hydroxyapatite Ln^(3+)(Ln = Eu or Tb)/iron oxide for magnetic targeted cellular imaging

Objective： To fabricate polymeric nanocomposites with excellent photoluminescence, magnetic properties, and stability in aqueous solutions, in order to improve specificity and sensitivity of cellular imaging under a magnetic field. Methods： Fluoridated LnS＋-doped HAP （Ln3＋-HAP） NPs and iron oxides （lOs） can be encapsulated with biocompatible polymers via a modified solvent exaction/evaporation technique to prepare polymeric nanocomposites with fluoridated Ln3＋-HAP/iron oxide. The nanocomposites were characterized for surface morphology, fluorescence spectra, magnetic properties and in vitro cytotoxicity. Magnetic targeted cellular imaging of such nanocomposites was also evaluated with confocal laser scanning microscope using A549 cells with or without magnetic field. Results： The fabricated nanocomposites showed good stability and excellent luminescent properties, as well as low in vitro cytotoxicity, indicating that the nanocomposites are suitable for biological applications. Nanocomposites under magnetic field achieved much higher cellular uptake via an energy-dependent pathway than those without magnetic field. Conclusion： 1tie nanocomposites fabricated in this study will be a promising tool for magnetic targeted cellular imaging with improved specificity and enhanced selection.

Adhesion of bone marrow mesenchymal stem cells on porous titanium surfaces with strontium-doped hydroxyapatite coating

Objective: To determine the adhesion behavior of bone marrow mesenchymal stem cells(MSCs) on a titanium surface with a nanostructured strontium-doped hydroxyapatite(Sr-HA) coating. Methods: Sr-HA coatings were applied on roughened titanium surfaces using an electrochemical deposition method. Primary cultured rat MSCs were seeded onto Sr-HA-, HA-coated titanium, and roughened titanium surfaces, and they were then cultured for 1,6, and 24 h.3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay was used to determine the metabolic condition of the cells. Scanning electron microscopy(SEM) was used to observe the cell morphology. The cytoskeletal structure was analyzed using fluorescence actin staining to characterize cell adherence. Quantitative real-time reverse transcription polymerase chain reaction(RT-q PCR) was used to analyze the gene expression levels of FAK(focal adhesion kinase), vinculin, integrin β1, and integrin β3 after culturing for 24,48, and 72 h. Results: MSCs cultured on the Sr-HA surface showed better cell proliferation and viability. Improvement of cell adhesion and structural rearrangement of the cytoskeleton were observed on the Sr-HA surface. The gene expression of FAK, vinculin, integrin β1, and integrin β3 was also elevated on the Sr-HA surface. Conclusions: Cell viability, adhesion, cell morphology, and the cytoskeletal structure were all upregulated considerably by the titanium surface modified with a Sr-HA coating.

Cytocompatible 3D chitosan/hydroxyapatite composites endowed with antibacterial properties:toward a self-sterilized bone tissue engineering scaffold

Bone tissue scaffolds based on bioactive polymer–hydroxyapatite composites have caused infections that seriously limit their extended application. In this study, we proposed a practical ion substitution method to synthesize in situ silver phosphate on the surface of a two-level, threedimensional chitosan/nano-hydroxyapatite scaffold. A release test of silver ions in a phosphate buffered saline(PBS) solution was performed to demonstrate that silver ions were released continuously from the silver phosphate during the initial 6 days of the study. The antibacterial property and cytocompatibility of the scaffolds treated with different concentrations of silver nitrate solution were assessed by in vitro assays with Escherichia coli and MC3T3-E1, respectively. The ability of the silver-containing scaffolds to induce bacteriostasis was confirmed by the inhibition zone(15 mm) and high bactericidal rate([99 %). Cell proliferation, morphology and the alkaline phosphatase activity of MC3T3-E1 cultured on the scaffold with low silver phosphate contents were comparable with those cultured on control samples.

Effect of small peptide(P-15) on HJMSCs adhesion to hydroxyap-atite

P-15, a synthetic peptide of 15-amino acids, has been tested in clinical trials to enhance cell adhesion and promote osseointe-gration. This feature of P-15 has also inspired the development of designing new bone substitute materials. Despite the increasing applications of P-15 in bone graft alternatives, few studies focus on the mechanism of cell adhesion promoted by P-15 and the mechanical property changes of the cells interacting with P-15. In this article, we used atomic force microscope(AFM) based single cell indentation force spectroscopy to study the impact of P-15 on the stiffness and the adhesion ability of human jaw bone mesenchymal stem cells(HJMSCs) to hydroxyapatite(HA). We found that the stiffness of HJMSCs increases as the concentration of P-15 grows in short culture intervals and that the adhesion forces between HJMSCs and HA particles in both the presence and absence of P-15 are all around 30 p N. Moreover, by calculating the binding energy of HJMSCs to HA particles mixed with and without P-15, we proved that P-15 could increase the adhesion energy by nearly four times. Scanning electron microscope(SEM) was also exploited to study the morphology of HJMSCs cultured in the presence and absence of P-15 on HA disc surface for a short term. Apparent morphological differences were observed between the cells cultured with and without P-15. These results explain the probable underlying adhesion mechanism of HJMSC promoted by P-15 and can serve as the bases for the design of bone graft substitute materials.

Role of adsorbed proteins on hydroxyapatite-coated titanium in osteoblast adhesion and osteogenic differentiation

The method of plasma-spray coating of hy- droxyapatite （HA） onto pure titanium has been demon- strated to be effective to enhance the osteogenic differentiation and accelerate bone regeneration. Yet it is still a big challenge to figure out the interplay among im- plant surface properties, adsorbed proteins and cell-surface interactions. In this study, the plasma-sprayed HA-coated titanium （HA-Ti） surface was compared with the titanium substrate in terms of protein adsorption, cell adhesion and differentiation. The phase composition, wettability and to- pography were characterized. Compared to the Ti substrate, the HA-Ti had a smaller water contact angle, but larger micro-scale roughness, and showed a poorer ability to ad- sorb fibronectin （Fn）, bovine serum albumin （BSA） and serum proteins. However, it could adsorb larger amount of recombinant human bone morphogenetic protein 2 （BMP- 2）. The osteoblasts and bone marrow mesenchymal stem cells （BMSCs） tended to adhere on the Ti substrate. By contrast, the BMSCs cultured on the HA-Ti showed a stronger tendency toward osteogenesis differentiation.

Biocompatibility Evaluation of Polyethylene Terephthalate Artificial Ligament Coating Hydroxyapatite by Fibroblasts Cells in Vitro

Hydroxyapatite(HA) based materials have been widely used in the field of ligament tissue engineering in the past decades.It has been previously reported that HA can increase the penetration of marrow-derived mesenchymal stem cells(MSCs) and MSCs cells into scaffolds due to increased cell differentiation in biological media.Additionally,it was found that there are much difference between MSCs and anterior cruciate ligament (ACL) cells.For that reason,we mainly evaluate the biocompatibility of polyethylene terephthalate(PET) silk scaffold with fibroblasts cells in vitro.We cultured mouse fibroblasts cells on the substrate of PET fiber and PET-HA scaffold,respectively,and then observed the morphology by using scanning electron microscopy.Our data indicate that PET-HA scaffold has good biocompatibility with fibroblasts cells and can potentially be useful in enhancing the fibroblasts cell differentiation and proliferation.