Biomedical Engineering Reference
In-Depth Information
3.2
Chapter 3.2
Classes of materials used
in medicine
Sascha Abramson, Harold Alexander, Serena Best, J. C. Bokros, John B. Brunski, Andr´ Colas, Stuart L. Cooper,
Jim Curtis, Axel Haubold, Larry L. Hench, Robert W. Hergenrother, Allan S. Hoffman, Jeffrey A. Hubbell,
John A. Jansen, Martin W. King, Joachim Kohn, Nina M. K. Lamba, Robert Langer, Claudio Migliaresi, Robert B. More,
Nicholas A. Peppas, Buddy D. Ratner, Susan A. Visser, Andreas von Recum, Steven Weinberg, and Ioannis V. Yannas
purity, and physical properties of the materials they were
using, but they also recognized the need for new materials
with new and special properties. This stimulated the de-
velopment of many new materials in the 1970s. New
materials were designed
de novo
specifically for medical
use, such as biodegradable polymers and bioactive ce-
ramics. Some were derived from existing materials fab-
ricated with new technologies, such as polyester fibers
that were knit or woven in the form of tubes for use as
vascular grafts, or cellulose acetate (CA) plastic that was
processed as bundles of hollow fibers for use in artificial
kidney dialysers. Some materials were ''borrowed'' from
unexpected sources such as pyrolytic carbons or titanium
alloys that had been developed for use in air and space
technology. And other materials were modified to provide
special biological properties, such as immobilization of
heparin for anti-coagulant surfaces. More recently bio-
materials scientists and engineers have developed a grow-
ing interest in natural tissues and polymers in combination
with living cells. This is particularly evident in the field of
tissue engineering, which focuses on the repair or re-
generation of natural tissues and organs. This interest has
stimulated the isolation, purification, and application of
many different natural materials. The principles and ap-
plications of all of these biomaterials and modified bio-
materials are critically reviewed in this chapter.
3.2.1 Introduction
Allan S. Hoffman
Biomaterials can be divided into four major classes of
materials: polymers, metals, ceramics (including carbons,
glass-ceramics, and glasses), and natural materials (in-
cluding those from both plants and animals). Sometimes
two different classes of materials are combined together
into a composite material, such as silica-reinforced sili-
cone rubber (SR) or carbon fiber- or hydroxyapatite (HA)
particle-reinforced poly (lactic acid). Such composites
are a fifth class of biomaterials. What is the history behind
the development and application of such diverse materials
for implants and medical devices, what are the composi-
tions and properties of these materials, and what are the
principles governing their many uses as components of
implants and medical devices? This chapter critically
reviews this important literature of biomaterials.
The wide diversity and sophistication of materials cur-
rently used in medicine and biotechnology is testimony to
the significant scientific and technological advances that
have occurred over the past 50 years. From World War II to
the early 1960s, relatively few pioneering surgeons were
taking commercially available polymers and metals, fab-
ricating implants and components of medical devices from
them, and applying them clinically. There was little gov-
ernment regulation of this activity, and yet these earliest
implants and devices had a remarkable success. However,
there were also some dramatic failures. This led the sur-
geons to enlist the aid of physical, biological, and materials
scientists and engineers, and the earliest interdisciplinary
''bioengineering'' collaborations were born.
These teams of physicians and scientists and engineers
not only recognized the need to control the composition,
3.2.2 Polymers
Stuart L. Cooper, Susan A. Visser, Robert
W. Hergenrother, and Nina M. K. Lamba
Many types of polymers are widely used in biomedical
devices that include orthopedic, dental, soft tissue, and
