Nanoporous Polyether Sulfone Membrane, Preparation and Characterization: Effect of Porosity and Mean Pore Size on Performance

Flat sheet membranes were prepared by phase inversion technique using polyether sulfone (PES) dissolved in dimethylacetamide (DMAc) with and without adding polyvinylpyrrolidone (PVP) or polyethyleneglycol (PEG). The characteristics of the prepared membranes were evaluated using Scanning Electron Microscope (SEM) images, Atomic Force Microscopy (AFM), and Optical Contact Angle (OCA) measurements, and porosity tests. The porosity test and SEM images show that increasing additives to a certain value increases the porosity of the membrane. Also, as the coagulation bath temperature is increased, the porosity of the membrane is increased. The roughness of the membrane is increased by increasing the additive concentration. The analysis of AFM images confirms the nanoporous structure of the prepared membranes, and that the membranes with appropriate pore size distribution can be prepared by the applied method. Permeability tests using single-layer membranes show that the direct relationship between porosity and the flux of pure water or salt solution is dominated by the effect of applied additive while the salt rejection shows an inverse relationship with the mean pore size regardless of the applied additive. The salt permeation flux is a function of total porosity while the salt rejection is a function of surface porosity. Pervaporation tests show that both permeation flux and enrichment factor depend on the total porosity of the support membrane

Fabrication of Polyethersulfone-Based Symmetric Membrane by Applying Pause Stage in Coagulation

Phase inversion is a common method for preparation of polymeric membranes. It is noticeable that most of the membranes prepared by this method have an asymmetrical structure. In this type of membranes, separation of particles occurs only by top dense layer in a high operating pressure. On the other hand, the separation process using symmetric membranes containing surface pores occurs on the top surface and in the depth of the membrane at lower operating pressure. In this research, preparation of polyethersulfone-based membranes was performed through the phase inversion method by dimethylacetamide as a solvent and water as the nonsolvent. Changing the coagulation conditions by applying one pause stage in an environment with the precise control of temperature and humidity, along with using polyvinylpyrrolidone as a hydrophilic additive, were attempted in order to controlthe porosity and structural changes of the membrane. Scanning electron microscopy (SEM) images, bubble point test, porosity, and mean pore radius measurements were used to study the structure of the prepared membranes. The performance of the membranes was evaluated by pure water permeation test and elimination of bacteria from cell culture medium. The results obtained illustrate that the implemented method is capable of preparation of membranes with symmetrical structure and pore diameter less than 0.4 μm featuring acceptable pure water flux and bacteria removalability. It was also observed that increase in the concentration of polyvinylpyrrolidone additiveleads to an increase in porosity, permeation and pore size of the membrane samples. On the other hand, the tensile strength and elongation-at-break of the membrane samples were reduced upon increasing in polyvinylpyrrolidone concentration

Human Bone Marrow Mesenchymal Stem Cell Behaviors on PCL/Gelatin Nanofibrous Scaffolds Modified with A Collagen IV-Derived RGD-Containing Peptide

Objective: We introduce an RGD (Arg-Gly-Asp)-containing peptide of collagen IV origin that possesses potent cell adhesion and proliferation properties. Materials and Methods: In this experimental study, the peptide was immobilized on an electrospun nanofibrous polycaprolactone/gelatin (PCL/Gel) hybrid scaffold by a chemical bonding approach to improve cell adhesion properties of the scaffold. An iodine-modified phenylalanine was introduced in the peptide to track the immobilization process. Native and modified scaffolds were characterized with scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). We studied the osteogenic and adipogenic differentiation potential of human bone marrow-derived mesenchymal stem cells (hBMSCs). In addition, cell adhesion and proliferation behaviors of hBMSCs on native and peptide modified scaffolds were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and 4',6-diamidino-2-phenylindole (DAPI) staining, and the results compared with tissue culture plate, as the control. Results: FTIR results showed that the peptide successfully immobilized on the scaffold. MTT assay and DAPI staining results indicated that peptide immobilization had a dramatic effect on cell adhesion and proliferation. Conclusion: This peptide modified nanofibrous scaffold can be a promising biomaterial for tissue engineering and regenerative medicine with the use of hBMSCs

Enhanced Cardiac Differentiation of Human Cardiovascular Disease Patient-Specific Induced Pluripotent Stem Cells by Applying Unidirectional Electrical Pulses Using Aligned Electroactive Nanofibrous Scaffolds

In the embryonic heart, electrical impulses propagate in a unidirectional manner from the sinus venosus and appear to be involved in cardiogenesis. In this work, aligned and random polyaniline/polyetersulfone (PANI/PES) nanofibrous scaffolds doped by Camphor-10-sulfonic acid (β) (CPSA) were fabricated via electrospinning and used to conduct electrical impulses in a unidirectional and multidirectional fashion, respectively. A bioreactor was subsequently engineered to apply electrical impulses to cells cultured on PANI/PES scaffolds. We established cardiovascular disease-specific induced pluripotent stem cells (CVD-iPSCs) from the fibroblasts of patients undergoing cardiothoracic surgeries. The CVD-iPSCs were seeded onto the scaffolds, cultured in cardiomyocyte-inducing factors, and exposed to electrical impulses for 1 h/day, over a 15-day time period in the bioreactor. The application of the unidirectional electrical stimulation to the cells significantly increased the number of cardiac Troponin T (cTnT+) cells in comparison to multidirectional electrical stimulation using random fibrous scaffolds. This was confirmed by real-time polymerase chain reaction for cardiac-related transcription factors (<i>NKX2.5, GATA4</i>, and <i>NPPA</i>) and a cardiac-specific structural gene (<i>TNNT2</i>). Here we report for the first time that applying electrical pulses in a unidirectional manner mimicking the unidirectional wave of electrical stimulation in the heart, could increase the derivation of cardiomyocytes from CVD-iPSCs