The Challenge for High Polymers in Medicine,Surgery, and Artificial Internal Organs

High polymers are used in medicine, surgery, or artificial organs in three ways: 1) to construct complete artificial replacements for human organs, 2) to repair, sustain, or augment function of normal organs, and 3) to provide a biochemical function.

Artificial hearts, heart lung machines, and artificial kidneys are examples of artificial organs that man is designing and building to replace natural organs. Plastics are used widely in their construction. Plastics offer a variety of properties needed for these applications, including ease of fabrication, chemical inertness, and nontoxic properties, and a wide range of physical properties in hardness, flexibility, and permeability.

Externally, as adjuncts or assists to natural organs, there are many applications of plastics in present use from clothing to glasses to dentures. Internally, the applications include vascular prostheses, check valve balls for heart valves, encapsulating resins for pacemakers, meshes and foams for reconstructive surgery, drainage tubes, and cannulae for hemodialysis. The plastics most widely used in surgical implants are polytetrafluoroethylene, polypropylene, saturated aromatic polyesters, and polysiloxanes. Growing use is being made of segmented polyurethanes, acrylics, and epoxy resins. Experimental work is under way on polyelectrolytes and various hydrogels based on polyhydroxyl compounds.

The newest class of applications of high polymers is that wherein the polymer has a definite and specific chemical interaction with the biochemistry of the body, i.e., it plays a pharmaceutical role. Examples of this include: 1) synthetic ion exchange resins for absorbing metabolites from the blood; 2) synthetic polyelectrolytes capable of absorbing specific viruses; 3) synthetic polymers such as (a) polyinosinic-polycytidylic acid (a synthetic ribonucleic acid) or (b) a copolymer of vinyl pyran and an undisclosed comonomer which promotes the production of interferon, a chemical substance normally produced by cells as an antiviral agent; and 4) synthetic natural-like polypeptides, enzymes, and chemical modifications of these with enhanced biologic activity.

The future of the use of high polymers in these applications appears to be in the earliest stages. Half a million Americans die each year of heart disease and 60,000 die of kidney disease, hence the potential for artificial versions of these organs is very large. The use of surgical devices is growing steadily. The use of polymers as drugs has not yet been tapped. In 50 years, biochemists will have a battery of synthetic polymer drugs which will cure many diseases, prevent cancer, speed wound healing, and eventually, it is hoped, provide a chemical regime for regeneration of lost limbs and organs.