Membrane materials medicine

Ward RA> Feldhoff PW, Klein E (1985) Membrane materials for therapeutic application in medicines. In Lloyd DR (ed) Materials science of synthetic membranes. ACS Symposium Series 269. American Chemical Society, Washington, DC, p 99... 

Over the past few decades, membrane materials and processes have been intensively studied due to multiple practical appHcations involving their abihty for selectivity and their capacity for concentration and fractioning in numerous domains such as environmental protection, biomedicine, and organic chemistry and in industries such as food, pharmaceutical, and electronics. This chapter is a general presentation which proposes some of the appUcations of membrane materials in pharmaceutics, such as for obtaining pure water in the pharmaceutical industry (at synthesis, formulation or conditioning of the pharmaceutical active substances), decontamination of polluted waters with medicines or medication wastes, and controlled drug deUvery devices for release of medications. The last part of the chapter is dedicated to a new class of materials—molecularly imprinted membranes and their applications such as chiral separation of optically active medications or the controlled release of enantiomers. 

Although ISEs are perhaps the earliest of practical medical sensors, and have good response capabilities for baseline, "housekeeping", ions of relevance to medicine, then-use is mainly restricted to the automated central hospital laboratory. Such in vitro use has, nevertheless, stimulated re-evaluation of their responsive constituents and membrane materials, eg, with regard to blood compatibility, which may have relevance to future in vivo use. Therefore, interest in the avoidance of leachables, for example, and investigation of alternative polymers is ongoing. 

R. A. Ward, P. W. Feldhoff, and E. Klein, Membrane materials for therapeutic applications in medicine, in Materials Science of Synthetic Membranes, D. R. Lloyd (Ed.), pp. 99-118, American Chemical Society, Washington, DC (1985). 

Membranes were originally developed as agents (filters, sieves) for solid-liqnid separations by mechanical means. In this context any interaction (adsorption) of the components with the membrane material was to be avoided. Recently however, the controlled (selective) adsorption of certain molecules on such membranes has become the object of intensive study. This does not mean that the primary sieving function of the membrane has lost its importance in such cases. Quite the opposite, it is the combination of the two functions of the membranes, sieving and adsorption, which opens up new possibilities for improving the efficiency of separation processes, especially in areas such as biotechnology and medicine (bioseparation). 

Polymers used in medicine fall into two main categories those that are sufficiently inert to fulfill a long-term structural function as biomaterials or membranes, and those that are sufficiently hydrolytically unstable to function as bioeradible materials, either in the form of sutures or as absorbable matrices for the controlled release of drugs. For the synthetic organic polymers widely used in biomedicine this often translates to a distinction between polymers that have a completely hydrocarbon backbone and those that have sites in the backbone that are hydrolytically sensitive. Ester, anhydride, amide, or urethane linkages in the backbone usually serve this function. 

Along these lines, supramolecular, bimolecular, as well as unimolecular approaches successfully mimicked the function of natural ion channels by using completely artificial and very simple molecules. Ion fluxes satisfied several criteria that these molecules form ion channels embedded in the bilayer lipid membrane. Non-peptidic artificial ion channels as well as helical bundles are now in our hands and it is likely that many more will soon emerge. The biological importance of these molecules may attract interest from many diverse branches of science—neurobiology, clinical medicine, biophysics, membrane technology, materials science, and others. 

There are minor uses for magnesium peroxide in household products, veterinary medicine, and metallurgy. Magnesium peroxide is a strong oxidizer and can cause fire when in contact with combustible materials. It is a powerful irritant to skin, eyes, and mucous membranes. 

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. 

MTT assay is a standard colorimetric assay used to determine cytotoxicity of potential medicinal agents and other toxic materials. It is based on the reduction of the tetrazolium salt MTT by viable cells. A mitochondrial dehydrogenase enzyme is able to cleave the tetrazolium rings of the pale yellow MTT and form dark purple formazan crystals, which are largely impermeable to cell membranes resulting in the accumulation of these crystals within healthy cells. Solubilization of the cells by the addition of a detergent results in the liberation of crystals, which are solubilized. The metabolic activity of cells is directly proportional to the concentration of the created formazan product (22), whose color is quantified in a colorimetric assay. 

DOT CLASSIFICATION 4.1 Label Flammable Solid SAFETY PROFILE A poison by subcutaneous route. Moderately toxic by ingestion and intraperitoneal routes. Questionable carcinogen with experimental tumorigenic data. An irritant to skin, eyes, and mucous membranes. Some persons suffer a skin rash if they come in contact with this material or the fumes evolved when it is heated. Human mutation data reported. Pure hexamethylenetetramine may be taken internally in small amounts and has been used in medicine as a urinary antiseptic. Its major industrial use is in the manufacture of phenolic resins. 

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. 

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