Extracorporeal artificial organs

Extracorporeal artificial organs provide mass-transfer operations to support failing or impaired organ systems [126]. Common examples include kidney substitute, hemodialysis, cardiopulmonary bypass (CPB), apheresis therapy, peritoneal dialysis, lung substitute and assist, and plasma separation. A critical component involved in the extracorporeal artificial organ is the membrane, which serves to separate the undesired substance from the blood or plasma. Ideally, materials used as the membrane in these particular applications should have appropriate cellular and molecular permeability, as well as blood compatibility (i.e., hemocompatibility). Over the years, both natural and synthetic polymers have been used as membrane materials. 

Malchesky PS. Extracorporeal artificial organs. In Ratner BD, Hoffman AS, Schoen FJ, Lemons JE, editors. Biomaterials science an introduction to materials in medicine. San Diego, CA Elsevier 2004. [chapter 7.6]. 

Design of Ideal Scaffold for Extracorporeal BAL or Implantable Artificial Organ... 

DESIGN OF IDEAL SCAFFOLD FOR EXTRACORPOREAL BIOARTIFICIAL LIVER (BAL) OR IMPLANTABLE ARTIFICIAL ORGAN... 

Blood compatible materials are essential for artificial organs which are used in contact with blood. The immunological aspects of blood compatibility are stressed. Complement activation induced by material-blood interaction is most likely related to transient leukopenia during extracorporeal circulation such as hemodialysis. Although transient, it may be harmful, especially if it occurs frequently. Some complications associated with hemodialysis may be caused due to the repeated complement activation and leukostasis in the lung. Cellulosic membranes induce the phenomenon more severely than synthetic membranes. Reused cellulosic membranes sterilized with aldehyde after the first use show less complement activation and leukopenia. Aldehyde treated biological substances may play a important role in enhancing blood compatibility. 

If a technique is developed to readily and securely cover a polymer surface with a layer of adequate cells, hybrid-type artificial organs for use in vascular reconstruction and extracorporeal liver support, for example, may be possible. For cell-culture substrates several polymer surfaces are already available which distinctly favor cell covering. Cationic surfaces or immobilization of cell-adhesive proteins such as fibronectin and collagen have been utilized in these cases. 

Polymeric materials having antithrombogenic activity are very important and their development is expected in the field of artificial organs such as the artificial vessel or the devices for extracorporeal circulation. In previous papers >2 we described that the binding of sulfonate and amino acid sulfamide groups onto cross-linked polystyrene endows these materials with antithrombic activity which requires the presence of a plasma cofactor, antithrombin III. These insoluble materials operate as catalysts of the inactivation of thrombin by its inhibitor as does soluble heparin. The catalytic effect of this mucopolysaccharide was demonstrated to require the formation of complexes between heparin and either antithrombin III or thrombin or both > >. ... 

The attachment of proteins and other biomolecules to PEG-grafted surfaces is also of interest for a number of applications. In solid-phase immunoassay and extracorporeal therapy, antibodies or other bioactive molecules are immobilized to a support that interacts with cells, blood, or plasma. Biocompatibility of implants and artificial organs can be improved by the attachment of growth factors to the surface via PEG spacers. These applications are all based on the regulating function of PEG in the interaction between a biomolecule, usually a protein, and another biomolecule or cell. More specifically, immobilization of the biologically active molecules to the free end of grafted PEG chains offers a way to minimize the interactions (deformation and nonspecific adsorption) of attached biomolecules with underlying surface, thus maximize the functions of immobilized biomolecules. 

Lindstrom SJ, Mermen MT, RosenfeldtFL, Salamonsen RF. Quantifying recirculation in extracorporeal membrane oxygenation a new technique validated. International Journal of Artificial Organs 2009 32(12) 857-63. 

In case of biomaterials such as artificial organs, implants or extracorporal systems which are necessarily in contact with blood, they have to have the highest known standard of biocompatibility, called haemocompatibility. That means compatibility and inertness to platelets and to other cellular components of blood, no contact activation and also no adhesion of plasma proteins which are known to trigger cellular reactions when they are adsorbed on surfaces and interact with their receptors. Additionally it means no level effect of complement activation and no cytotoxicity. 

Chang TMS. Semipermeable aqueous microcapsules (artificial cells)—with emphasis on experiments in an extracorporeal shunt system. Trans Am Soc Artif Internal Organs 1966 12 13-19. 

Lung. No implantable, artificial lung exists, and transplantation of this organ is relatively rare. Much work has been done, however, on extracorporeal oxygenators, which are used in over 100,000 operations each year. These oxygenators add fresh oxygen to the blood and permit removal of carbon dioxide. Several designs have... 

Extracorporeal devices are mechanical organs that are used for blood purification they include the artificial kidney (dialyser), the artificial liver, and the mechanical lung. The function and performance of these devices both benefit from fibre and textile technology. Extracorporeal devices must possess certain requirements, such as bacterial resistance, and they must be anti-allergenic and non-toxic, have good breathability, and possess the ability to withstand sterilisation. Table 5.3 illustrates the function of each device and the materials used in their manufacture. 

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