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Working with Nature |
As new applications for polymers were being found, some researchers wondered whether they could also play a role in the human body, perhaps in repairing or replacing body tissues and cartilage. The idea was not entirely new. The natural polymer collagen, found in animal connective tissue, had been used as surgeon's thread for more than 2,500 years. And as early as the 1860s, an artificial polymer called collodion, invented a decade earlier by the French chemist Louis Ménard, was used as a liquid dressing for minor wounds. Collodion, made from a solution of cellulose nitrate in alcohol and ether, formed a solid film that could be peeled off after the wound healed. The excellent barrier properties of polymers were also central to an experiment in 1933 by Italian biologist Vincenzo Bisceglie, who implanted tumor cells encased in a nitrocellulose membrane in a guinea pig. The cells survived, protected by the membrane against attack by the host animal's immune cells.
Meanwhile, the question of contending with the body's immune system was becoming a critical one in medicine. Scientists were beginning to recognize that many diseases of the heart, liver, and kidney actually involved failures of these organs, and they were initiating efforts to replace damaged organs with healthy ones. However, the body's immune cells--which are designed to seek out and destroy any foreign tissue--are unable, for example, to distinguish between an unwanted bacterial infection and a much-desired transplanted kidney. Although some early drugs, such as corticosteroids, azathioprine, and 6-mercaptopurine, helped in combating rejection, the problem began to fade only after 1969, when Swiss microbiologist Jean Borel discovered that a soil fungus, cyclosporin A, would selectively interfere with the specific immune cells that drive the rejection reaction. The 1983 approval of cyclosporin A by the U.S. Food and Drug Administration (FDA) gave transplant surgeons a tool that has since saved the lives of thousands of patients with heart, liver, or kidney failure.
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