Functional polymer scaffolds for blood vessel tissue engineering

Scaffold pore size plays a critical role in the infiltration of the cells into the structure. For engineered blood vessels, co-cultures of endothelial (EC) on the lumen, and smooth muscle cells (SMC) on the external surface of tubular scaffolds are performed. The more adequate pore sizes for EC are, in general, smaller than for SMC. In the present work, poly(ε-caprolactone) (PCL) flat film and hollow fibers are prepared by phase inversion. The influence of polymer and coagulation solution compositions on pore morphology of the films is analysed and the results are applied to obtain, in a one step process, PCL hollow fibers with suitable pore size for both EC and SMC

Controlled drug delivery through tailor-made blend polymeric membranes

In this work, we prepare tailor-made membranes by blending sulfonated poly(ether ether ketone) (S-PEEK) and poly(ether sulfone) (PES) polymers, at various ratios. Timolol (TM) is used as a model drug for the investigation of the controlled delivery through these membranes and their application to a transdermal TM patch is discusse

Impregnated membranes for direct methanol fuel cells at high methanol concentrations

Sulfonated poly(phthalazinone ether ketone) (SPPEK) impregnated Solupor® microporous film (SPPEK–PE) and pure SPPEK membranes with two different ion-exchange capacities (IECs) were prepared and characterized for use in DMFC applications. Swelling, proton conductivity, diffusion and DMFC experiments were performed at various methanol concentrations to understand the effect of impregnation of an ion-conductive polymer membrane to the fuel cell performance.\ud \ud Impregnating SPPEK into PE decreases swelling degree and methanol permeability of the membranes, but at the same time the proton conductivity. Unlike perfluorinated membranes, SPPEK–PE shows an increase in its DMFC performance at high methanol concentration and that makes it more attractive for mobile DMFC applications where high methanol concentrations are needed to compete with Li-ion batteries

Insight into the transport mechanism of solute removed in dialysis by a membrane with double functionality

The present study aims at shedding light on the transport mechanisms involved in a functionalized membrane designed for improving hemodialysis. This membrane is prepared by embedding absorptive micro particles within its porous structure. To understand the transport mechanism through the membrane and make suggestions for its optimization, a mathematical model coupling convection, diffusion and adsorption is developed and validated by comparison of experimental and theoretical results. In fact, the model provides a description of the concentration profile from the donor (feed) compartment across the several layers with different properties to the acceptor (dialysate) compartment. In addition, the model allows to predict the influence of various parameters such as molecule diffusivity, membrane thickness, presence of convection, content of adsorptive particles on the flux intensification across the membrane. Comparison with experimental measurements demonstrates that the model is able to describe the transmembrane mass flux variation over time as a function of hydrodynamic conditions and membrane/module geometric parameters. The model also illustrates how the proposed double-layer membrane concept offers significant benefits in terms of toxin removal in comparison to conventional dialysis. As so, the main achievement of the developed model is that it may serve as tool for the further improvement of functionalized membrane in terms of toxin removal and optimization of process condition

The matching conditions of controlled Lagrangians and IDA-passivity based control

This paper discusses the matching conditions resulting from the controlled Lagrangians method and the interconnection and damping assignment passivity based control (IDA-PBC) method. Both methods have been presented recently in the literature as means to stabilize a desired equilibrium point of an Euler±Lagrange, respectively Hamiltonian, system. In the context of mechanical systems with symmetry, the original controlled Lagrangians method is reviewed, and an interpretation of the matching assumptions in terms of the matching of kinetic and potential energy is given. Secondly, both methods are applied to the general class of underactuated mechanical systems and it is shown that the controlled Lagrangians method is contained in the IDA-PBC method. The $\lambda$-method as described in recent papers for the controlled Lagrangians method, transforming the matching conditions (a set of non-linear PDEs) into a set of linear PDEs, is discussed. The method is used to transform the matching conditions obtained in the IDA-PBC method into a set of quadratic and linear PDEs. Finally, the extra freedom obtained in the IDA-PBC method (with respect to the controlled Lagrangians method) is used to discuss the integrability of the closed-loop system. Explicit conditions are derived under which the closed-loop Hamiltonian system is integrable, leading to the introduction of gyroscopic terms

Sorption induced relaxations during water diffusion in S-PEEK

This paper presents an analysis of the sorption kinetics of water vapor and liquid water in the glassy polymer sulfonated poly(ether ether ketone) (S-PEEK). Sorption isotherms are determined experimentally using a gravimetric sorption balance, and the relative contributions of Fickian diffusion and relaxational phenomena are quantified as a function of the water concentration in the polymer using the model of Hopfenberg and Berens.Analysis of the sorption isotherms and determination of the sorption kinetics prove the occurrence of both Fickian sorption behavior and relaxational phenomena already at very low water concentrations in the polymer. With increasing water concentration, the relative importance of relaxation phenomena increases, whereas the relative contribution of Fickian diffusion decreases.Based on the water vapor sorption kinetics only, the Fickian diffusion coefficient increases over two orders of magnitude with increasing water vapor concentration. Taking also the diffusion kinetics from liquid water sorption experiments into account reveals a change of even three orders of magnitude of the Fickian diffusion coefficient when the water concentration in the polymer increases

Bioengineered Kidney Tubules Efficiently Clear Uremic Toxins in Experimental Dialysis Conditions

Patients with end-stage kidney disease (ESKD) suffer from high levels of protein-bound uremic toxins (PBUTs) that contribute to various comorbidities. Conventional dialysis methods are ineffective in removing these PBUTs. A potential solution could be offered by a bioartificial kidney (BAK) composed of porous membranes covered by proximal tubule epithelial cells (PTECs) that actively secrete PBUTs. However, BAK development is currently being hampered by a lack of knowledge regarding the cytocompatibility of the dialysis fluid (DF) that comes in contact with the PTECs. Here, we conducted a comprehensive functional assessment of the DF on human conditionally immortalized PTECs (ciPTECs) cultured as monolayers in well plates, on Transwell® inserts, or on hollow fiber membranes (HFMs) that form functional units of a BAK. We evaluated cell viability markers, monolayer integrity, and PBUT clearance. Our results show that exposure to DF did not affect ciPTECs’ viability, membrane integrity, or function. Seven anionic PBUTs were efficiently cleared from the perfusion fluid containing a PBUTs cocktail or uremic plasma, an effect which was enhanced in the presence of albumin. Overall, our findings support that the DF is cytocompatible and does not compromise ciPTECs function, paving the way for further advancements in BAK development and its potential clinical application.</p