Membrane bioartificial organs

Membrane separation in the medical field has been included in a chapter focused on medical extracorporeal devices, which illustrates the use of membranes for separation of biological fluids and for preparation of bioartificial organs able to accomplish ex vivo biological transformation (Part headed Transformation ). 

Medical applications are among the most important in the membrane market, with hemodialysis, blood oxygenators, plasma separation and fractionation being the traditional areas of applications, while artificial and bioartificial organs and regenerative medicine represent emerging areas in the field. 

Membrane, with appropriate permeability characteristics, as well as, physicochemical properties, is used in bioartificial organs as selective barriers to compartmentalize isolated cells while allowing the transport of nutrients and metabolites to cells and the transport of catabohtes and specific metabolic products to blood. Moreover, the membrane avoids the contact between immune system components with xenogenic cells to prevent immunological response and rejection of xenograft. 

CytocompatibUity is a key issue for membrane in bioartificial organs. In this respect, the development of new materials with physicochemical properties that provide improved blood/cell compatibility is strictly related to the progress in this promising... 

Whole-cell, hollow-fiber MBR are still under development. Despite their significant potential they have, so far, found only limited application for biochemicals production. One of the reasons is that cleaning of the hollow-fiber membranes is difficult, especially when whole-cell biocatalysts are immobilized in the small fibers. The mass transfer between the nutrients and cells has also to be taken into consideration and enhanced. Immobilizing the biocatalysts in porous beads, instead of directly on the membrane, may tend to avoid some of these problems, and to simplify membrane cleaning. The concept of using MBR as bioartificial organs is technically very attractive the various MBR under development, however, must still be validated with clinical results. One can expect, however, that their development will follow the success of artificial kidneys, which are currently employed worldwide. 

Examples of medical textiles used in extracorporeal medical devices include the use of hollow fibres and membranes (made om polyester, polypropylene, silicone, viscose) for production of bioartificial organs, such as the kidneys, liver and lungs. 

Sakai S., Ono T., Ijima H., Kawakami K. Aminopropyl-silicate membrane for microcapsule-shaped bioartificial organs control of molecular permeability. J. Membr. Sd. 2002 202 73-80 Sakai S., Ono T., Ijima H., Kawakami K. Permeability of alginate/sol-gel s)mthesized aminopropyl-silicate/alginate membrane templated by calcium-alginate gel. J. Membr. Sci. 2002 205 183-189... 

Fissell WH IV, Humes DH, Roy S, Fleischman A. Ultrafiltration membrane, device, bioartificial organ, and methods. United States Patent20060213836 2006. 

Figure 11. Scheme of a bioartificial pancreas surrounded by a hydrogel membrane [266], Some methods used for artificial organs design are presented in table 17. 

As liver performs multiple and complex functions, artificial organ or bioartifidal organ exploiting a synthetic cartridge to host biological components such as cells (hepatocytes in the case of a bioartificial liver) have been investigated. Among all of these potentialities, we only focus here on purely artificial systems. Membrane-based bioartificial livers (BAL) will not be described here, but could be found in other reviews [22-25] and in another chapter in the present book. 

Stange J, Mitzner SR, Risler T et al. Molecular adsorbent recychng system (MARS) Chnical results of a new membrane-based blood purification system for bioartificial hver support. Artif Organs 1999 23 319-30. 

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