Adsorption medical membranes

The combination with molecular-sieve adsorption or membrane permeation allows breaking an azeotrope without the need of a contaminating solvent. This is advantageous when separating ultrapure components, such as medical grade ethanol from its azeotrope with water. More details can be found elsewhere [5, 10, 14]. 

Using the MPC copolymers, improvements in biocompatibility of medical membranes such as a cellulose hemodialysis membrane (20,21), a polyolefin membrane for an oxygenator (22), and a covering membrane for an implantable biosensor are underway (25). The MPC copolymers have nonthrombogenicity, protein adsorption resistance, and good solute permeability. 

BIOELECTROCHEMISTRY. Application of the principles and techniques of electrochemistry to biological and medical problems. It includes such surface and interfacial phenomena as the electrical properties of membrane systems and processes, ion adsorption, enzymatic clotting, transmembrane pH and electrical gradients, protein phosphorylation, cells, and tissues. 

In some technological and medical applications protein adsorption and/or cell adhesion is advantageous, but in others it is detrimental. In bioreactors it is stimulated to obtain favourable production conditions. In contrast, biofilm formation may cause contamination problems in water purification systems, in food processing equipment and on kitchen tools. Similarly, bacterial adhesion on synthetic materials used for e.g. artificial organs and prostheses, catheters, blood bags, etc., may cause severe infections. Furthermore, biofilms on heat exchangers, filters, separation membranes, and also on ship hulls oppose heat and mass transfer and increase frictional resistance. These consequences clearly result in decreased production rates and increased costs. 

Adsorbents are used in medicine mainly for the treatment of acute poisoning, whereas other extracorporeal techniques based on physico-chemical principles, such as dialysis and ultrafiltration, currently have much wider clinical applications [1]. Nevertheless, there are medical conditions, such as acute inflammation, hepatic and multi-organ failure and sepsis, for which mortality rates have not improved in the last forty years. These conditions are usually associated with the presence of endotoxin - lipopolysaccharide (LPS) or inflammatory cytokines - molecules of peptide/protein nature [2]. Advantages of adsorption over other extracorporeal techniques include ability to adsorb high molecular mass (HMM) metabolites and toxins. Conventional adsorbents, however, have poor biocompatibility. They are used coated with a semipermeable membrane of a more biocompatible material to allow for a direct contact with blood. Respectively, ability of coated adsorbents to remove HMM solutes is dramatically reduced. In this paper, preliminary results on adsorption of LPS and one of the most common inflammatory cytokines, TNF-a, on uncoated porous polymers and activated carbons, are presented. The aim of this work is to estimate the potential of extracorporeal adsorption technique to remove these substances and to relate it to the porous structure of adsorbents. 

Polyurethane hydrogels are widely used in soft contact lenses, controlled release devices, semipermeable membranes and hydrophilic coatings (66). The properties of polyurethane hydrogels can be varied by variation of their components, such as the polyols, diisocyanate, chain extender, or cross-linker (67-69). Because of the excellent mechanical and physical properties, polyurethanes are widely used in medical applications such as coating for medical devices for preventing protein adsorption (70, 71). 

HoUow fibers are widely used for filtration, utilizing the semipermeable nature of their capillary walls. In the medical industry, hollow fiber bioreactors are often made from cellulose and synthetic polymers. Cellulose acetate and cuprammonium rayon are the widely used ceUulose-based hollow fibers, while synthetic hollow fibers are often made from polysulfone, polyamide, and polyacrylonitrile. Modifications can be made to these materials to improve their functions by using polymers based on phospholipid, a substance found in the human cell membrane. 2-methaCTyloyloxyethyl phosphoryl-choline (MPC) is a methacrylate monomer with a phospholipid polar group. When MPC-based copolymers are used as additives for polysulfone, protein adsorption and platelet adhesion can be effectively reduced, thereby improving blood compatibility. Cellulose acetate hollow fiber membranes can also be modified with MPC-based copolymers by means of blending or surface coating to obtain improved permeability. 

Membrane processes are very important in our everyday life, but also in industry, for example, for water and waste water treatment, in medical applications, or separation of petrochemicals. Membrane processes are an energy saving method for the separation of mixtures, which occur in nearly all production processes in the chemical industry. Membrane-based devices are much smaller and work at lower temperatures compared to conventional separation facilities with distillation, extraction, or adsorption processes. Classical separation methods used for purification of chemical products, notably distillation, extraction, and crystallization are energy and cost intensive. Over 50% of the energy costs in the chemical industry are used for the separation of gaseous or liquid mixtures. With membrane technology, the costs for difficult separations, for example, of azeotropic mixtures. 

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