An Introduction to Materials in Medicine

The use of materials in medicine relates primarily to longer-term use of biologic or synthetic materials interacting with living tissue. Such short-term-use items as blood bags and syringe needles are generally not considered part of the definition. D.F. Williams, in "Progress in Biomedical Engineering" (1987), provided the definition which has become the standard. He described it as "a non-viable material used in a biomedical device intended to interact with biological systems."

Examples of Uses

• Many people have fillings in their teeth made of a metal amalgam, plastic or gold. When injured or operated upon so that the skin has to be sewn shut, a biological material such as catgut or a synthetic material such as plastic is used to suture the wound. In severe burns, a material resembling some of the properties of skin may be used. Cochlear implants that enable some deaf persons to hear are now available as are pacemakers, which help to control irregular heartbeats. Insulin pumps to assist diabetics and artificial knee parts are also available because of research on materials used for medical purposes.

Materials

• Polymers of various types--commonly known as plastic, metals, such as titanium, and ceramics, such as alumina--are frequently used because of their ability to remain stable in the body. A material which flaked or corroded excessively might not be satisfactory. Material scientists once believed that the best materials to use were those that were inert, that had no reaction to the environment inside the body. They now know that no material is inert in the body and develop materials and coatings that are biocompatible. These materials are capable of being in the body for long periods without degrading or causing harm to the surrounding tissue. A well-known example is the concern caused by the material used in breast implants.

Hip Replacements

• As humans age, they tend to suffer bone loss and weakened connective tissue. Between the ages of 80 and 90, 33 percent of women and 17 percent of men will suffer hip fractures. Titanium used in hip replacements corrodes but has no adverse effect on the body. A ceramic coating is used to cover the end of the joint because it wears better than metal.

Material Scientist and Engineers

• Chemistry, biochemistry, physics and engineering disciplines play a significant role in the development of materials used in medicine. In addition to physicians, dentists and materials scientists, expertise is required areas such as nanotechnology, neurology, blood coagulation, cell adhesion, protein synthesis, immunology, and electronics and hydraulics engineering.

Non-Scientists Involvement

• Federal regulations cover medical materials development. The Food and Drug Administration must approve all devices just as it approves medications. This means that members of Congress will be involved to some extent. Legal issues can arise in cases where devices cause damage to people. When body parts or functions involve artificial devices, ethical issues also arise. All humans are affected by materials in medicine.