Polymer artificial organs

Ishihara, K. (2000) Bioinspired phospholipid polymer biomaterials for making high performance artificial organs. Science and Technology of Advanced Materials, 1, 131—138. 

Polymers are organic materials and are sensitive to natural or artificial UV sources. This is of primary importance for outdoor exposure of unprotected parts and for some industrial applications such as electrical welding, photocopier light exposure devices. .. 

Long-term inertness without loss of strength, flexibility, or other necessary physical property is needed for use in artificial organs, prostheses, skeletal joints, etc. Bioerodability is needed when the polymer is used as a carrier such as in controlled release of drugs, removal of unwanted materials, or where the materials purpose is short-lived, such as in their use as sutures and frames for natural growth. 

Applications. Medical Applications. The medical applications of si-loxane polymers are numerous (7, 8, 36). For example, prostheses, artificial organs, facial reconstruction, and catheters take advantage of the inertness, stability, and pliability of the polysiloxanes. Artificial skin, contact lenses, and drug delivery systems take advantage of the high permeability of these polymers, as well. 

However, to date, almost all of the artificial organs (artificial hearts, blood vessels, hips and knees, etc.) have been constructed from hard and dry materials. These artificial organs, to some extent, have successfully served as substitutes for real organs, but are still far from satisfactory. For example, artificial hips and knees made of metals and ceramics, which are hard and dry materials, lack the shockabsorbing function and have a high frictional resistance against sliding motion [3]. Another example is artificial blood vessels. Blood blots occur in artificial blood vessels made of polymers due to protein adsorption at the surface of the blood vessel wall [4]. 

In order to construct artificial organs with an excellent function similar to the real biological organ, material innovation is urgently required, i.e., one should find a man-made soft and wet material as substitute for biotissue. Synthetic hydrogels, which consist of polymer networks swollen with large amounts of water (the same as biotissue), are the only candidates [5]. Different from biotissue, tlie water content... 

This approach was considered because it would permit the synthesis of biomaterials (for drug delivery systems, sutures, artificial organs, etc.) which are derived from nontoxic metabolites (amino acids and dipeptides) while also having other desirable properties for example, the incorporation of an anhydride linkage into the polymer backbone could result in rapid biodegradability, an iminocarbonate bond may provide mechanical strength, and an ester bond may result in better film and fiber formation. 

Besides the many immunological events that can be initiated by the synthetic polymers as just described, there are also the pathological implications to be considered, such as the in vivo fate of the Ag-Ab complexes. Consequently, there is an urgent need for emphasis on immunological studies of biomaterials. Meanwhile, from our data and the information in the literature as just described, it appears that artificial organs may not be immune to immune responses. But the long-term effects of such responses as well as these effects on the complement system seem to be much more complex than are realized at present. 

As we shall see in Chapter 15, polyurethane is a polymer of choice for a wide variety of biomedical applications. Polyurethane is used extensively in the construction of devices such as vascular prostheses, membranes, catheters, plastic surgery, heart valves, and artificial organs. Polyurethanes are also used in drug delivery systems such as the sustained and controlled delivery of pharmaceutical agents, for example, caffeine and prostaglandin. ... 

---