Perfluorosulfonate ion-exchanged membranes (PFSIEMs) have been prepared by the melt-extrusion method. Subsequently, the effect of annealing on the properties of PFSIEMs was studied. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis suggested that −SO 3 − groups could be brought to the membrane surface, presumably by side chain movement during the course of thermal annealing. In the presence of coexisting ion clusters and crystallization, area resistance increased with the rise of the treatment temperature. X-ray diffraction (XRD) analysis further showed that the annealing treatment should increase the crystallinity of membranes, markedly. The equivalent weight (EW) and water uptake were also employed to evaluate the effect of annealing on membranes. For membranes prepared by melt extrusion, abnormal fluctuations are solely evident in the thermogravimetric (TG) traces of annealed specimens. In addition, two glass transition temperatures, ca. 120 and ca. 250 °C, have been observed in the differential scanning calorimetry (DSC) analysis. When the thermal annealing temperature was increased, however, the lower endothermic peak shifted to the high temperature region, mostly because water molecules can serve as the plasticizer to reduce T g . In addition, we also found that the dynamic mechanical property of membranes can be substantially impacted by annealing. Changes in the temperature relaxation have been explored with dynamic mechanical analysis (DMA).
The chemistry and topography of the material surfaces have an important effect on cell behaviors. In this study, we reported the preparation of thermoresponsive micropatterned surfaces (TS) and galactosylated TS for modulating the adhesion/detachment of cells. A thickness of 1 μm of poly(N-isopropylacrylamide) grafted layer was fabricated on the polystyrene surface with microgrooves using ultraviolet-induced copolymerization. The thick grafted layer was in favor of the interactions between cells and materials. The following immobilization of galactose ligand with specific affinity to hepatocyte onto TS promoted the adhesion of human hepatocyte line (HL-7702 cells). The microgrooves structure could facilitate cell adhesion and regulate the oriented growth of cells. Moreover, narrow grooves accelerated the spontaneous detachment of cells only by reducing temperature. Thus, micropatterned biofunctional designs with controlled geometrical features presented in this study have sufficient biofunctional activities in facilitating cell sheet engineering and regenerative medicine.
A novel polystyrene (PS) substrate with microscale porous structure was facilely fabricated by crystalline-controlled casting method using mixed solvent [N,N-dimethylformamide and ethyl alcohol (v/v)] based on the nonsolvent induced phase separation process. The substrate surfaces exhibited a bi-continuous microscale porous morphology with high porosity, large pore size and pore-pore connection structure. Moreover, behaviors of the normal human liver cell line (HL-7702) seeded on this substrate surface were carefully investigated. The results indicated that the cell adhesion, spread and cell-cell connection on the surface with subcellular pore size (∼ 10 μm) were similar to the cells proliferated on the flat PS surface. However, the number of HL-7702 cells proliferated on the PS microscale porous surface was higher than cells on the conventional PS flat surface, suggesting that the pore-pore structure was conducive to HL-7702 cell proliferation. Furthermore, hematoxylin and eosin staining and micronucleus test were performed. The results showed that fewer damages for nuclear and cytoplasm and less cell genotoxicity were caused by the microscale porous structure within the scope of pore size (∼ 10 μm) than that of the flat surface.
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