Dialysis membranes poly membrane

The use of synthetic polymers in medicine and biotechnology is a subject of wide interest. Polymers are used in replacement blood vessels, heart valves, blood pumps, dialysis membranes, intraocular lenses, tissue regeneration platforms, surgical sutures, and in a variety of targeted, controlled drug delivery devices. Poly(organosiloxanes) have been used for many years as inert prostheses and heart valves. Biomedical materials based on polyphosphazenes are being considered for nearly all the uses mentioned above. 

Godjevargova Z, Dimon A, and Petrov S. Chemical modification of dialysis membrane based on poly(acrylonitrile-methylmethacrylate-sodium vinylsulphonate). J. Appl. Polym. Sci. 1992 44 2139-2143. 

Satchera, D.M., Childs, R.F., Mika, A.M., and Dickson, J.M. Acid recovery using diffusion dialysis with poly(4-vinylpyridine)-fiUed microporous membranes. J. Membr. Sci., 148, 119-127, 1998. 

In this device, a poly(vinyl chloride) (PVC) membrane separates an internal K+ solution from an external layer of digoxin antibody that is trapped at the sensor surface with a dialysis membrane. The digoxin-crown ether conjugate, which selectively binds K+, is present only in the PVC layer due to its hydrophobic properties. Competition between free digoxin (analyte) that freely crosses the... 

Another approach involved the use of a carbonate membrane bonded to SU8 channels with a glass layer used to seal the device [29]. The system used a stacked approach with a dialysis membrane sandwiched between an SU8 perfusion channel and a poly(dimethylsiloxane) flow channel (Figure 48.4). Bonding the membrane reduced the chance of leakage and resulted in a more robust device. A fluorescent dye and glucose solution were used for optical characterization of the system. A eommercially available glucose sensor was used to determine the concentration of glucose in the dialysate. A recovery of 80% was obtained at flow rate of 1.5 tiL/min. 

CA films by using the phase inversion process. These CA films were cast from solvent/nonsolvent solutions to yield size exclusion membranes consisting of a thin permselective outer layer and a more porous sublayer. These membranes permitted the rapid permeation of a 1500-dalton poly (ethylene glycol) ester of ferrocene however the reproducibility of results presents a problem with these CA mem-branes. Christie et demonstrated that thin films of plasticized polyvinylchloride (PVC), normally used for potentiometric ion-selective electrode applications, applied to electrodes over a polycarbonate dialysis membrane offered improved selectivity ratios for the amperometric detection of phenolic compounds and H2O2 in the presence of the common biological interferents, ascorbic acid and uric acid, over those observed at the dialysis membrane alone or at a composite dialysis/membrane. 

The most common type of microdialysis probe is constructed as a concentric tube as shown in Fig. 1. The probes usually consist of a semiper-meable membrane, such as polysulfone, polyethersulfone, polyamide, polycarbonate-poly ether copolymer, or cuprophan [4], glued between the tip of the inner cannula and the outer shaft, which are made of steel or plastic. The perfusion fluid (perfusate) enters the inlet flowing through the inner tube to its distal end and exits the inner tube to enter the space between the inner tube and the outer dialysis membrane where molecular exchange takes place. After the exchange, the fluid containing the molecules of interest (dialysate) is transferred towards the proximal end of the probe and is collected at the outlet for later... 

In the field of membrane dialysis the results of an evaluation study for the artificial kidney-chronic uremia programme have been reported (15 contributors). Comparative clinical studies are concerned principally with the relative merits of celiulosic and polyacrylonitrile-based membranes. New membranes based on poly(vinyl alcohol) modified in various ways and on ethylene-vinyl acetate copolymers have been described. The manufacture, and influence of manufacturing parameters, on the structure and function of membranes for artifical kidneys have been discussed. The use of assymmetric hollow fibre haemodialysers (polyamide, polyurethane, polyester) has been considered in some detail. ... 

In 2002, Uhneanu et al. used a thin organic layer that is supported by a porous hydrophobic membrane such as porous Teflon or poly vinylidenedifluoride (PVDF), or sandwiched between two aqueous dialysis membranes [295]. With this setup, they showed that the transfer of highly hydrophilic ions at one interface can be studied by limiting the mass transfer of the other ion-transfer reaction at the other interface. They have also shown that cyclic voltammetry for coupled ion-transfer reactions at the two interfaces in series is analogous to cyclic voltammetry for electron-transfer reactions studied by Stewart et al. [207], as the diffusion equations of the reactants and products are analogous, and as the overall Nernst equation for the coupled ion transfer equal to the two individual Nemst equations for ion distribution is also analogous to the Nemst equation for the heterogeneous ET. 

As a summary, it is possible to improve both, blood compatibility and the adsorption of dialysate contaminants, such as endotoxins, through a chemical modification of the membrane poly-mer, as realized in some polysuHone dialysis membranes. 

Van Koten and Frey used a hyperbranched poly(triallylsilane) as the support for palladium- pincer complexes.[63] The supported palladium-pincer complexes were applied in the catalytic aldol condensation of benzaldehyde and methyl isocyanate. Their activity was similar to that of single site Pd catalysts. According to the authors, the complex is suitable for continuous membrane applications, as demonstrated by their purification by means of dialysis. 

The presence of the term y) makes the permeability coefficient a function of the solvent used as the liquid phase. Some experimental data illustrating this effect are shown in Figure 2.7 [11], which is a plot of the product of the progesterone flux and the membrane thickness, 7, against the concentration difference across the membrane, (cio — cif ). From Equation (2.28), the slope of this line is the permeability, P]. Three sets of dialysis permeation experiments are reported, in which the solvent used to dissolve the progesterone is water, silicone oil and poly(ethylene glycol) MW 600 (PEG 600), respectively. The permeability calculated from these plots varies from 9.5 x 10 7 cm2/s for water to 6.5 x 10 10 cm2/s for PEG 600. This difference reflects the activity term yj/ in Equation (2.28). However, when the driving force across the membrane is... 

Plastic microdevices for high-throughput screening with MS detection were also prepared for detection of aflatoxins and barbiturates. These devices incorporated concentration techniques interfaced with electrospray ionization MS (ESI-MS) through capillaries [2], The microfluidic device for aflatoxin detection employed an affinity dialysis technique, in which a poly (vinylidene fluoride) (PVDF) membrane was incorporated in the microchip between two channels. Small molecules were dialyzed from the aflatoxin/antibody complexes, which were then analyzed by MS. A similar device was used for concentrating barbiturate/antibody complexes using an affinity ultrafiltration technique. A barbiturate solution was mixed with antibodies and then flowed into the device, where uncomplexed barbiturates were removed by filtration. The antibody complex was then dissociated and electrokinetically mobilized for MS analysis. In each case, the affinity preconcentration improved the sensitivity by at least one to two orders of magnitude over previously reported detection limits. 

Fig. 4. Scatchard plots for the binding of tilorone hydrochloride to calf thymus DNA (a) Me. lysodeikticus DNA (b) poly (dA-dT) poly (dA-dT) (c) and poly (dG-dC) poly (dG-dC) (d). Each different symbol corresponds to a separate experiment. Thus, each figure represents a set of 4 or 5 separate experiments, r is moles of bound tilorone/base pair concentration and (u) is the concentration of unbound tilorone. Equilibrium dialysis was carried out by a procedure and an apparatus (Dianorm, supplied by Dr. Virus KG, Bonn, Germany) described by Weder et al.61 Dialysing membrane (0.02S mm thick) was sandwiched between two halves of a Teflon (round) macro-cell (dialysable volume = 1 ml). The DNA, or labelled tilorone solutions were introduced by separate micro syringes on either side of the membrane through the side valves. The valves were closed air tight and the macro-cells were fixed into a rotating machine. All equilibrium dialysis studies were carried out at 20°, and at 10 rotations/min. Under these conditions equilibrium was attained in 4-5 hr. After the equilibrium was reached 0.8 ml of the solution from either side of the membrane was withdrawn by microsyringes and the radioactivity was determined using dioxan scintillation fluid...

The membranes produced from polyelectrolyte complexes on the basis of weak polyelectrolytes, e.g. poly(carboxylic adds) (PAA and PMAA) and polyamines [poly(2-N,N-dimethylaminoethyl methacrylate), polyethylenepiperidine, polyethyl-enepyperasine, polyethylenimine] have been prepared140,141 and used in dialysis and ultrafiltration. Permeability coeffirients of membranes made from poly electrolyte complexes are much higher (4 and 20 times, resp.) in comparison with the cellulose-based membranes (Cuprophane, Film 1(M)). 

Polyelectrolyte complexes are very promising materials for preparing semi-permeable membranes of definite permeability and selectivity The methods of preparation and the properties of membranes made of polyelectrolyte complexes based on strong polyelectrolytes, e.g. poly(sodium sterene sulfonate) and poly(vinylbenzyl-trimethyl ammonium chloride) were described These membranes may be applied for reverse osmosis in the desalting of sea-water, for dialysis and ultrafiltration in purifications and concentration of water solutions containing coUoids or micro-and macroparticles ... 

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