ABSTRACT
Nano-Sb2O3 has excellent synergistic flame-retardant effects. It can effectively improve the comprehensive physical and mechanical properties of composites, reduce the use of flame retardants, save resources, and protect the environment. In this work, nanocomposites specimens were prepared by the melt-blending method. The thermal stability, mechanical properties, and flame retardancy of a nano-Sb2O3â»brominated epoxy resin (BEO)â»poly(butylene terephthalate) (PBT) composite were analyzed, using TGA and differential scanning calorimetry (DSC), coupled with EDX analysis, tensile testing, cone calorimeter tests, as well as scanning electron microscopy (SEM) and flammability tests (limiting oxygen index (LOI), UL94). SEM observations showed that the nano-Sb2O3 particles were homogeneously distributed within the PBT matrix, and the thermal stability of PBT was improved. Moreover, the degree of crystallinity and the tensile strength were improved, as a result of the superior dispersion and interfacial interactions between nano-Sb2O3 and PBT. At the same time, the limiting oxygen index and flame-retardant grade were increased as the nano-Sb2O3 content increased. The results from the cone calorimeter test showed that the peak heat release rate (PHRR), total heat release rate (THR), peak carbon dioxide production (PCO2P), and peak carbon monoxide production (PCOP) of the nanocomposites were obviously reduced, compared to those of the neat PBT matrix. Meanwhile, the SEMâ»energy dispersive spectrometry (EDX) analysis of the residues indicated that a higher amount of C element was left, thus the charring layer of the nanocomposites was compact. This showed that nano-Sb2O3 could promote the degradation and charring of the PBT matrix, improving thermal stability and flame retardation.
ABSTRACT
Fabrication of small diameter vascular grafts (SDVGs) with appropriate responses for clinical application is still challenging. In the present work, the production and characterization of solid alginate based microfibers as potential SDVG candidates through the method of microfluidics were considered original. A simple glass microfluidic device with a 'L-shape' cylindrical-flow channel in the microfluidic platform was developed. The gelation of microfibers occurred when the alginate solution and a CaCl2 solution were introduced as a core flow and as a sheath flow, respectively. The diameters of the microfibers could be controlled by varying the flow rates and the glass capillary tubes diameters at their tips. The generated microfibers had somewhat rough and porous surfaces, their suture retention strengths were comparable to the strength of other tissue engineered grafts. The encapsulated mesenchymal stem cells proliferated well in the microfibers, and showed a stable endothelialization under the angiogenesis effects of vascular endothelial growth factor and fibroblastic growth factor. The in vivo implant into the mice abdomens indicated that cell composite microfibers caused a mild host reaction. These encouraging results suggest great promise of the application of microfluidics as a future alternative in SDVGs engineering.
Subject(s)
Alginates , Biocompatible Materials , Blood Vessel Prosthesis , Microfluidic Analytical Techniques , Alginates/chemistry , Alginates/metabolism , Animals , Biocompatible Materials/chemistry , Biocompatible Materials/metabolism , Cell Proliferation/drug effects , Cell Survival/drug effects , Cells, Cultured , Equipment Design , Female , Fibroblast Growth Factors , Glucuronic Acid/chemistry , Glucuronic Acid/metabolism , Hexuronic Acids/chemistry , Hexuronic Acids/metabolism , Male , Mesenchymal Stem Cells/cytology , Mesenchymal Stem Cells/drug effects , Mice , Microfluidic Analytical Techniques/instrumentation , Microfluidic Analytical Techniques/methods , Vascular Endothelial Growth Factor A/pharmacokinetics , Vascular Endothelial Growth Factor A/pharmacologyABSTRACT
Vaccinia Tian Tan (VTT) was attenuated by deletion of the TC7L-TK2L and TA35R genes to generate MVTT3. The mutant was generated by replacing the open reading frames by a gene encoding enhanced green fluorescent protein (EGFP) flanked by loxP sites. Viruses expressing EGFP were then screened for and purified by serial plaque formation. In a second step the marker EGFP gene was removed by transfecting cells with a plasmid encoding cre recombinase and selecting for viruses that had lost the EGFP phenotype. The MVTT3 mutant was shown to be avirulent and immunogenic. These results support the conclusion that TC7L-TK2L and TA35R deletion mutants can be used as safe viral vectors or as platform for vaccines.
