Dialysis membranes reuse

The impact of hemodialysis on drug therapy depends on drug characteristics (e.g., molecular weight, protein binding, and Vp), dialysis prescription (e.g., dialysis membrane composition, filter surface area, blood and dialysate flow rates, and reuse of the dialysis filter), and clinical indication for dialysis. 

Membrane-Enclosed Enzymatic Catalysis (MEEC) has been developed as a useful, practical new method for the manipulation of enzymes in organic synthesis. The enzyme in soluble form is enclosed in commercially available dialysis membranes. It combines the simplicity of use of soluble enzymes with certain of the advantages of immobilized enzymes. Containment permits separation of the enzyme from the reaction medium, straightforward separation of the product, and recovery of the enzyme for reuse [53],... 

Fresh high-flux dialysis membranes achieve approximately 23—37% reductions in plasma P2M levels [344]. However, dialyzer reuse significantly impairs the removal of P2M [345]. Indeed, it has been recognized that non-specific adsorption of middle molecules on the surface of these synthetic high-flux membranes, rather than difiusion through the membrane, can account for significant amounts of the device s clearance [346, 347]. With the surface area of membranes in the dialysis device amounting to less than 2 m, the adsorption capacity of the device is obviously too small. 

The miniPERM Bioreactor (30, 31) consists of two components, the production module (40 ml) containing the ceUs and the nutrient module (600 ml of medirrm). The modules are separated by a semi-permeable dialysis membrane (MWCO 12.5 kDa) which retains the cells and mAb in the production module but allows metabolic waste products to diffuse out to the nutrient module. There is a permeable silicone rubber membrane for oxygenation and gas exchange in the production module. The whole unit rotates (up to 40 r.p.m.) within a CO2 incubator. It can be purchased as a complete disposable ready to use unit or the nutrient module (polycarbonate) can be autoclaved and reused at least ten times. 

Antibody-catalyzed reactions, too, can be conducted on a gram scale (Reymond, 1994) the biocatalyst was separated by dialysis in a cellulose membrane (12-14 kDa, antibody 150 kDa) and reused. The enantioselective hydrolysis of the enol ether (4) to the ketone (5) ran with an e.e. of 89-91% (Figure 18.10). 

In a hollow fiber dialyzer the blood flows down the bore of the fiber, providing good fluid flow hydrodynamics. An advantage of the hollow fiber design is that only 60-100 mL of blood is required to fill the dialyzer. At the end of a dialysis procedure hollow fiber dialyzers can also be easily drained, flushed with sterilizing agent, and reused. Dialyzer reuse is widely practiced, in part for economic reasons, but also because the biocompatibility of the membrane appears to improve after exposure to blood. 

With the planned consolidation of the top four U.S. dialysis providers into two vertically integrated companies, the field of available dialyzers is likely to narrow. Meanwhile, the decrease in dialyzer reuse will continue to drive increased production. Given that the Center for Medicare and Medicaid Services (CMS), formerly known as the Healthcare Financing Administration (HCFA), will continue its downward pressure on costs, and possibly institute a capitated payment system (i.e., a fixed monthly payment to cover all patient costs including hospitalization), only incremental improvements in commercially available dialyzer membranes are expected in the next 5 years. 

This chapter, in addition to surveying membrane types and production, overviews applications of gas and liquid membrane separation and polymer films as banier layers. Water purification for reuse and in desalination using reverse osmosis and nano-, ultra-, and microfiltration are discussed. Electrodialysis, dialysis, and hemodialysis are also covered. Membranes in emerging technologies are described including fuel cell membranes, membranes in lithium batteries, conducting polymer membranes, and thin film membranes used in LED and photovoltaic applications. 

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