Preparation of bi-continuous macroporous polyamide copolymer membranes for cell culture

[[abstract]]Skinless bi-continuous macroporous membranes with extremely high porosity, ∼80%, were prepared by the non-solvent induced phase separation (NIPS) process, from casting dopes composed of Elvamide (co-polymer of Nylon-6, -66, and -610), chitosan, and formic acid that were immersed in a water bath maintained at 10 °C. The Chitosan, while functioned as a pore former, migrated along with out-diffusing formic acid into the bath during the NIPS process, thereby, breaking the top gel-layer and the boundaries between cellular pores to yield a morphology featuring interpenetration networks of pores and polymer host. The amount of chitosan added to the dope affected significantly the pore size and porosity of the membranes formed, as revealed by SEM observations. At the highest chitosan/Elvamide ratio of 0.155, very large pore size (∼30 μm) and porosity (83%) were achieved, whereas at the lowest ratio of 0.1, the membrane became asymmetric, and the pore size was reduced to ∼15 μm. 1H NMR analyses indicated that chitosan was completely removed during the precipitation process. Furthermore, L929 cells were cultured on various porous membranes. It is interesting to find that this cell was able to dwell on the pore walls in the cross sectional region, although with a smaller proliferation than on a flat nonporous surface.[[incitationindex]]SCI[[booktype]]電子

The DSC study on physical aging of PET

[[abstract]]Isothermal enthalpy relaxation in polyethylene terephthalate (PET) was measured at different annealing temperature below the glass transition temperature (Tg) on a differentia l scanning calorimeter (DSC) . The endothermic peaks below Tg were found on DSC scan curves and the peaks increased in magnitude and shifted to higher temperature with increasing aging time. We found the empirical fractional exponential function could describe the aging phenomena. The time constant r e in the fractional exponential function was lower at higher aging temperature It meant the aging rate was increasing with aging temperature. The temperature dependent activation energy obtained from this method was about 40 Kcal / mole. Also from the fractional exponential function fitting ,we found that the relaxation curves of samples aging at different temperatures couldn't be superimposed by a shift in time.[[sponsorship]]明志工業專科學校[[conferencetype]]國內[[conferencedate]]19901105~19901105[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]臺北縣, 臺

Asymmetric composite membranes from chitosan and tricalcium phosphate useful for guided bone regeneration

[[abstract]]To fulfill the properties of barrier membranes useful for guided bone tissue regeneration in the treatment of periodontitis, in this study a simple process combining lyophilization with preheating treatment to produce asymmetric barrier membranes from biodegradable chitosan (CS) and functional β-tricalcium phosphate (TCP) was proposed. By preheating TCP/CS (3:10, w/w) in an acetic acid solution at 40°C, a skin layer that could greatly increase the mechanical properties of the membrane was formed. The asymmetric membrane with a skin layer had a modulus value almost 4-times that of the symmetric porous membrane produced only by lyophilization. This is beneficial for maintaining a secluded space for the bone regeneration, as well as to prevent the invasion of other tissues. The subsequent lyophilization at -20°C then gave the rest of material an interconnected pore structure with high porosity (83.9-90.6%) and suitable pore size (50-150 μm) which could promote the permeability and adhesiveness to bone cells, as demonstrated by the in vitro cell-culture of hFOB1.19 osteoblasts. Furthermore, the TCP particles added to CS could further increase the rigidity and the cell attachment and proliferation of hFOB1.19. The TCP/CS asymmetric composite membrane thus has the potential to be used as the barrier membrane for guided bone regeneration.[[incitationindex]]SCI[[booktype]]電子

Synthesis of Modified Silica Spheres Used for the Preparation of Dual Ultraviolet- and Thermo-cured Epoxyacrylate/Silica Composites

[[abstract]]To investigate the interfacial effect on properties of epoxyacrylate–silica composites, submicron-sized silica spheres were synthesized by sol–gel reaction under a basic environment and their surfaces were endowed with vinyl functional groups by further modification with 3-methacryloxypropyl trimethoxy silane. The pure silica (PS) and the modified silica (MPS) spheres were characterized by Fourier transform infrared, 29Si- and 13C-nuclear magnetic resonance (NMR), scanning electron microscope (SEM), and particle size analyzer. The silica spheres were then added to the presynthesized difunctional epoxyacrylate resin with one vinyl group and one epoxide group at each end, in addition to the photo- and thermo-curing agents. After cure, thermal and mechanical properties of the obtained epoxyacrylate–silica composites were measured and compared. Tensile mechanical properties including initial modulus, ultimate tensile strength, and elongation at break, as well as the fracture energy of the epoxyacrylate–silica composite were all increased by increasing the content of silica spheres. Moreover, the composites filled with MPS had stronger interfacial strength between silica sphere and matrix than those with PS and thus exhibited an additional increase of tensile mechanical properties and fracture toughness. The increase of fracture toughness was owing to the crack deflection and particle–matrix debonding as evidenced by SEM pictures on the fracture surface.[[incitationindex]]SCI[[booktype]]電子

Structure characterizations and protein resistance of chitosan membranes selectively crosslinked by poly(ethylene glycol) dimethacrylate

[[abstract]]Chitosan (CS) is a fragile material with a high modulus of elasticity. Improving its flexibility as well as membrane permeability are the key aspects that need to be addressed for using CS as a biomaterial. Poly(ethylene glycol) (PEG) has several unique properties such as protein resistance, low toxicity, immunogenicity, and good solubility in both water and organic solvents. In this study, a vinyl compound was grafted to the C-6 position of CS by protection-grafting-deprotection. The vinyl CS was then crosslinked with PEG dimethacrylate (PEGDMA) selectively at its C-6 position to form CS-g-PEG copolymer membranes. Analyses from spectra of Fourier-transform infrared and nuclear magnetic resonance confirmed the chemical structure of the crosslinking CS-g-PEG copolymer membranes. Thermal and mechanical properties of the prepared CS-g-PEG membranes were measured and well-correlated to their structures. The incorporation of PEGDMA into the CS increased the material’s flexibility and thermal resistance. Finally, the CS-g-PEG membranes were found to have good protein resistance and blood compatibility; therefore, it has potential application as the biomedical material especially for hemodialysis.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]電子

應用柏克萊的動力網狀模型來描述PP的黏度性質

[[abstract]]D. S. Soong 提出了分子的動力網狀模型來描述高分于系統的流變行為。黏度受到剪切率的影響主要是由於隨著剪切率的增加，紐纏密度逐漸地減少。在穩定狀態下，紐纏的生成速率和消失速率達到一個動態平衡。而黏度即正比於紐纏數目。紐纏的消失速率主要是由於剪切率的關係，而假設和其a 次方成正比;紐纏的生民速率則和熱擴散運動有關，並且假設和剪切率無關。最後的方程式非常簡單，而且可以描述大部份高分于的流變性質[[sponsorship]]明志工業專科學校[[conferencetype]]國內[[conferencedate]]19891104~19891104[[booktype]]紙本[[iscallforpapers]]Y[[conferencelocation]]臺北縣, 臺

Delivery of Berberine Using Chitosan/Fucoidan-Taurine Conjugate Nanoparticles for Treatment of Defective Intestinal Epithelial Tight Junction Barrier

[[abstract]]Bacterial-derived lipopolysaccharides (LPS) can cause defective intestinal barrier function and play an important role in the development of inflammatory bowel disease. In this study, a nanocarrier based on chitosan and fucoidan was developed for oral delivery of berberine (Ber). A sulfonated fucoidan, fucoidan-taurine (FD-Tau) conjugate, was synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy. The FD-Tau conjugate was self-assembled with berberine and chitosan (CS) to form Ber-loaded CS/FD-Tau complex nanoparticles with high drug loading efficiency. Berberine release from the nanoparticles had fast release in simulated intestinal fluid (SIF, pH 7.4), while the release was slow in simulated gastric fluid (SGF, pH 2.0). The effect of the berberine-loaded nanoparticles in protecting intestinal tight-junction barrier function against nitric oxide and inflammatory cytokines released from LPS-stimulated macrophage was evaluated by determining the transepithelial electrical resistance (TEER) and paracellular permeability of a model macromolecule fluorescein isothiocyanate-dextran (FITC-dextran) in a Caco-2 cells/RAW264.7 cells co-culture system. Inhibition of redistribution of tight junction ZO-1 protein by the nanoparticles was visualized using confocal laser scanning microscopy (CLSM). The results suggest that the nanoparticles may be useful for local delivery of berberine to ameliorate LPS-induced intestinal epithelia tight junction disruption, and that the released berberine can restore barrier function in inflammatory and injured intestinal epithelial.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]電子

Preparation of asymmetric polyhydroxybutyrate/chitosan composite membrane for guided bone regeneration

[[abstract]]In this study, an asymmetric composite membrane composed of a porous chitosan layer and a dense polyhydroxybutyrate (PHB) layer was prepared, and its mechanical properties as well as cellular compatibility were evaluated. First, the PHB dense layer with a thickness of ca. 32 m was obtained by direct oven-drying. After being treated with plasma to produce free radicals on the surface and subsequently graft polymerized with poly(acrylic acid), the PHB was immersed in the CS solution where the CS chains could be chemically bonded to the PHB surface via carbodiimide activation. After lyophilization, an asymmetric PHB/CS composite membrane was obtained. Compared to the porous CS membrane, the composite membrane had higher tensile mechanical properties. In addition, the fibroblast cells (L929 and HGF) and human osteoblast cells (hFOB1.19) were cultured on both sides of the composite membrane. All the cells could proliferate very well indicating that both PHB and CS layers were cellular compatible. Yet, the PHB dense layer could prohibit the fibroblast cells to penetrate through the membrane. Thus, the asymmetric composite membrane can be use as a potential barrier membrane for guided bone regeneration in periodontal tissue engineering.[[sponsorship]]Taiwan Polymer Society[[conferencetype]]國際[[conferencedate]]20131117~20131122[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Kaohsiung, Taiwa

Preparation and properties of dual-curable epoxyacrylate composites filled with different functionalized silica spheres

[[abstract]]In this study, uniform-sized silica spheres were first synthesized by sol-gel reaction under a basic environment and their surfaces were modified to possess different functional groups including vinyl, epoxide and amino groups by reaction with 3-methacryloxypropyl trimethoxy silane (MPTMS), vinyl triethoxysilane (VTEOS), 3-glycidoxy propyltrimethoxy silane (GPTMS) and 3-Aminopropyl trimethoxysilane (APTMS). The functionalized silica spheres were characterized by FTIR, 29Si and 13C solid-NMR and SEM. These silica spheres with size ranging from 150~250 nm were then added to the pre-synthesized difunctional epoxyacrylate resin with one epoxide end group and one vinyl terminal groups. After photo- and thermal cure, mechanical properties and fracture toughness were measured to elaborate the effects of different functionalized silica spheres on the properties of epoxyacrylate-silica composites. Tensile mechanical properties including initial modulus, ultimate tensile strength and elongation at break, and also the fracture toughness of the epoxyacrylate-silica composite were all increased with increasing the amount of modified silica spheres. The increase of fracture toughness was due to the crack deflection and particle-matrix debonding as evidenced by SEM pictures on the fracture surface. Among these composites, the one filled with the MPTMS-modified silica had the best tensile mechanical properties and fracture toughness.[[sponsorship]]Polymer Processing Society[[conferencetype]]國際[[conferencedate]]20130715~20130719[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Nuremberg, German

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead