Читать книгу Materials for Biomedical Engineering - Mohamed N. Rahaman - Страница 18

Biomaterials can be classified as natural materials or synthetic materials, depending on their source. Natural biomaterials are materials obtained from human and other vertebrate sources, invertebrate organisms, and from plants. They include bone taken from live humans or cadavers, collagen isolated from animal skin and bones, cellulose produced by certain types of bacteria or obtained from plants, silk from spiders, chitin extracted from the shells of crustaceans, alginate produced by seaweed, and hyaluronic acid extracted from rooster combs or from genetically engineered bacteria. Natural biomaterials are typically similar or identical to substances in living organisms.

In comparison, synthetic biomaterials are produced from industrial materials that have commonly undergone some degree of refinement. As illustrated in Figure 1.3, they are composed of:

 Metals, including their alloys, such as gold; stainless steels; titanium (Ti) and its alloys;

 Ceramics, including glasses and glass‐ceramics, such as aluminum oxide (Al2O3 ); the calcium phosphates hydroxyapatite and β‐tricalcium phosphate; bioactive glasses;

 Polymers such as polyethylene (PE); polymethyl methacrylate (PMMA); nylon; silicone (polydimethylsiloxane);

 Composites composed of one or more of the abovementioned classes of materials.

Figure 1.3 Schematic of the classes of materials used as biomaterials, along with examples of specific biomaterials in each class.

Metals, ceramics, and polymers are said to make up the primary classes of synthetic biomaterials. Semiconductors are sometimes described as a fourth class of synthetic materials but the few semiconductors that find use as biomaterials typically have structures similar to ceramics. Consequently, in this book, they are included, where appropriate, within the category of ceramics.