Medical membranes

Hanft S. C-208R Key Medical Membrane Devices for the New Millennium. Connecticut Business Communications Company Inc., 2002 p. 58. 

There is one more group of operations in the figure. Among the operations are facilitated transport, active transport, membrane reactors, medical membrane devices, and membrane energy conversion systems. Although the techniques in question are still under basic research they are available on the market, but their marketability is rather low. 

Though application of ion exchange membranes to ion sensors was reported several decades ago, the membranes do not have selectivity for specific ions and are not used practically except for particular cases such as the measurement of the concentration of hydrofluoric acid (instead of with a glass electrode).300 Medically, membranes with specific crown ethers have been widely used as ion sensors for diagnosis such as the determination of Na+ and K+ in blood and urine, and specific bilayer membranes have been used to determine anions for the same purpose (Chapter 5.3.5).301... 

The concept of a membrane has been known since the eighteenth century, but was used little outside of the laboratory until the end of World War II. Since then, the U.S. medical membrane device market was valued at 2.1 billion in 2010 and is forecast to grow to 2.9 billion by 2016, with a compound annual growth rate (CAGR) of 5% [1]. 

BCC Research, Medical Membrane Devices Markets and Technologies, Report Code MST043E, Published January 2012. 

Applications - films, housewares, medical, membranes, nail care, ophthalmic, printing inks ... 

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. 

MAJOR PRODUCT APPLICATIONS capacitors, coatings, crown models, ignition wires, inks, laminates, medical, membranes, mold coating, molded parts, printing, rollers, seals, varnish, windshield wipers ... 

Mitsuru Suzuki, Medical Membrane Department, Toyobo Corp., Osaka, Japan... 

In this chapter, the state-of-the-art artifleial membranes used in cUnically established blood treatment processes is reviewed. Information on medical membrane preparation and surface modification is often not disclosed. For this reason, the typical feamies of commercial medical membranes will be reported as provided by the manufacturers. The criteria that have driven membrane development will also be discussed to inform membranologists about what is currently available commercially and the opportunities for further development in selected medical treatments. Proper consideration is given to the influence of membrane-blood interactions on membrane performance and the therapeutic success of a membrane-based treatment. Membranes used in accessories for the above treatments or for related pharmaceutical purposes are not considered. 

In this Section, it is implicitly assumed that the mass transport resistance at the fluid-membrane interface on either side of the membrane is negligible. Also the following is information that is made available publicly by the membrane manufacturers, when not otherwise noted. As in technical processes, mass transport across semipermeable medical membranes is conveniently related to the concentration and pressme driving forces according to irreversible thermodynamics. Hence, for a two-component mixture the solute and solvent capacity to permeate a semipermeable membrane under an applied pressure and concentration gradient across the membrane can be expressed in terms of the following three parameters Lp, hydraulic permeability Pm, diffusive permeability and a, Staverman reflection coefficient (Kedem and Katchalski, 1958). All of them are more accurately measured experimentally because a limited knowledge of membrane stmcture means that theoretical models provide rather inaccurate predictions. 

The earliest membranes used for medical purposes were prepared with cellulose by exploiting the spinning expertise of the textile industry. Only in the late 1960s, did techniques become available to prepare artificial membranes with the available technical polymers and to exploit the convenient properties of these polymers. Medical membranes have been traditionally classified as either namral or synthetic, depending on whether their backbone was made of cellulose or of a technical polymer, respectively (Klinkmann and Vienken, 1994). The reason for this was that, at that time, the material used was correlated with the membrane separation properties, ceUulosic membranes generally being less... 

The first membranes used in medicine were made of cellophane, a ceUulose-based material that was used at that time as sausage casing (Kolff and Berk, 1943). To take advantage of the physical strength of cellulose membranes, but to improve on their diffusive permeability and biocompatibUity, techniques have been developed over the years to produce cellulose-based membranes with walls as thin as 5 p.m and featuring microdistrib-uted hydrophobic side branches. Below, the main features of the commercial semiperme-able medical membranes with a ceUulosic backbone are briefly discussed. 

Thermoplastic synthetic polymers are used for preparing semipermeable medical membranes owing to their good mechanical resistance and low density, which make it possible to easily prepare thin self-supporting hollow-fiber membranes, and their low energy requirement and processing costs. In the following, the main features of the commercial semipermeable medical membranes made of synthetic polymers are briefly discussed. 

Materials used to make medical membranes were primarily developed for technical applications and were adapted to medical use only later on. In spite of the changes to polymer formulation and of the proposed polymer chemical modifications, the bloodcontacting surface of commercial medical membranes bears but a pale resemblance to... 

In 2006 GE announced a new amorphous TPI, Extern , with Tg < 311°C, and high strength, stiffness, chemical and creep resistance at T < 230°C.The new TPI finds applications in auto, aerospace and military products, downhole oil and gas production, medical membranes, electrical connectors, electronics for lead-free soldering, semiconductor wafer handling, and specialty films for insulators and flexible circuitry. 

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