The Cyborg Transformed

The Six Million Dollar Man, based on Martin Caidin’s Cyborg, brought bionic humans into the sitting rooms of millions of people. Today’s melding of human and technology may not help men run faster, but it still saves lives. Photo courtesy Mary Ellen Bowden.

In the book Cyborg, the basis for the popular TV series The Six Million Dollar Man, test pilot and former moon walker Steve Austin crashes his plane in the California desert. His mangled body is re-created with enhanced powers, and he becomes the cyborg, or bionic man.

In the grand strategy to put Steve back on his feet, man-made materials are everywhere (though playing second fiddle to computers and feedback loops). Author Martin Caidin based his reconstruction on an imaginative extrapolation of state-of-the-art theory and practice in his “present” of 1972. Despite their science-fiction-sounding names, his materials really existed. Silastic, a silicone rubber, covered Steve’s skull before his scalp was reattached. Steve’s damaged mitral heart valve is fixed with a “Hufnagel disk valve,” a medical device invented by medical pioneer Charles A. Hufnagel, who pioneered heart valves and heart-lung machines in the 1950s and 1960s. Caidin describes the valve as a ring of metal rimmed with Teflon with a white disk made of Silastic. To replace or restore Steve’s broken bones the surgeons used Vitallium, an alloy, and Cerosium, a pioneer ceramic bone-replacement material.

Possibly the oddest replacement part, put into real-world use just three years after Steve’s rehabilitation, is made from a material often deployed in extreme weather conditions. GORE-TEX, a popular waterproof and breathable fabric that protects both serious and armchair explorers, was first used in a biocompatible form as a patch for damaged arteries.

The story of synthetic vascular grafts and stents, today the most common internal artificial devices, shows how replacement parts evolve. In 1947 a research fellow at Columbia University’s College of Physicians and Surgeons named Arthur Voorhees accidentally left behind a silk suture in the heart of an experimental dog. Later, he noticed that heart tissue had coated the silk. Voorhees then sewed up a silk tube and successfully grafted it into the artery of a dog. In the course of further experiments a young colleague suggested that Voorhees turn to an extremely light synthetic fabric used to make parachute canopies and spinnakers for sail boats—Union Carbide’s Vinyon-N, a type of nylon. In 1952 a patient whose abdominal artery ruptured became the first human to receive such a graft.

Researchers continued to experiment with various synthetic materials in the search for long-lasting materials that would function like an artery or vein without being attacked by the body’s immune system. By the 1960s DuPont’s Dacron—a type of polyester—led the market, in part because surgeon Michael DeBakey pioneered its use. (DeBakey would become more famous for his work with the artificial heart.) In 1975 W. L. Gore & Associates (Gore) joined the synthetic materials field as a strong market competitor. Gore-Tex is expanded polytetrafluorethylene (ePTFE), which in its unexpanded form is better known as Teflon, the non-stick fry-pan coating. Like the Teflon in Steve’s new heart valve, Gore ePTFE was chosen for internal use partly because it is nearly inert in that environment. (Teflon is so inert it was used in the Manhattan Project to protect against the effects of highly corrosive uranium hexafluoride gas.) Unlike Teflon, the porosity of this material permitted the body’s own tissue to grow through the graft, helping to integrate it into the circulation system. The interstices in woven or knitted Dacron serve a similar function. Both synthetic materials can be attached to a stent, a metal supporting structure.

Because synthetics do have drawbacks (such as inducing blood clots), doctors still prefer to patch a patient’s damaged blood vessel with a graft taken from a healthy vessel. But the potential for clotting—which can lead to heart attacks or strokes—can be reduced with heparin, a powerful natural substance produced by the body and available commercially since the 1930s. In the 1980s molecular chemists developed a way of making the synthetic and the natural work together by bonding heparin molecules directly onto the polymers used as grafts.

Natural healing, synthetic materials, electronics, and information science all played a part in remaking Steve. Yet Caidin could not have imagined the bioengineering and regenerative medicine that began to emerge in the mid-1980s. These multidisciplinary fields incorporate clinical medicine, cell biology, biochemistry, biotechnology, other life sciences, and engineering. Instead of only man-made materials this type of medicine also uses natural molecules, cells, and tissues that are induced to grow in the body or in the laboratory.

Scientists have not just developed special bioactive coatings for artificial body parts; they have also experimented in coaxing cells, whole tissues, and even organs to grow in bioreactors. So far, skin is the biggest success story. Surgeons can now choose from several FDA-approved bioengineered skin grafts—often used to replace skin damaged beyond self-repair by wounds, infections, or burns. Bioengineered bladders, though still in clinical trials, are probably next. To create new skin or a new bladder a patient’s own stem cells or stem cells from donors are used as “seeds,” which are then placed on a biodegradable polymer. As the seeds grow, the polymer scaffolding is slowly absorbed by the body, leaving only the new organ.

What bordered on science fiction in 1972 is now routine: replacement hips, heart valves, patches for arteries and veins, and artificial skin. And while much science fiction still focuses on the artificial rather than the natural, in the real science future, grown natural tissues will likely play an even bigger role in replacement parts. The contributions of chemical scientists were underestimated in Cyborg; in the world of today, where science is as wonderful as fiction, there is plenty of work for them.

Mary Ellen Bowden is a senior research fellow at the Chemical Heritage Foundation.