Biomedical Engineering Reference
In-Depth Information
occurring in the tissue from which cells were
extracted. A more complex example is an ortho-
pedic implant, such as a hip replacement. Here
the objective is to have the implant integrate with
bone tissue, forming a strong bond between the
implant surface and bone.
BOX 8.1
A DICTIONARY
DEFINITION OF A
SURFACE
sur-face (sûr“f Ə s) n. Abbr. sur. 1. a. The outer
or the topmost boundary of an object. b. A
material layer constituting such a boundary.
2. Mathematics. a. The boundary of a three-
dimensional figure. b. The two-dimensional
locus of points located in three-dimensional
space. c. A portion of space having length
and breadth but no thickness. (Merriam-Web-
ster , www.merriam-webster.com )
8.1.3 Scope
The foregoing examples serve to broadly intro-
duce the scope and topic of this chapter: how
to modify the surface of biomaterials to achieve
biocompatibility. First on the agenda is to identify
exactly what a surface is and why it is important
to biomaterial performance. Second is a discus-
sion of how surfaces influence the “biological
response” to artificial materials that controls bio-
compatibility, to the extent this is currently under-
stood. Third, examples of modifying surfaces to
achieve biocompatibility are discussed within the
context of the basic mechanisms of biocompat-
ibility. Importantly, this chapter does not provide
a review of the substantial literature on biomate-
rial surface-modification techniques. That task
has been admirably carried out in many good
topics [4-8] and review articles [9,10] appearing
elsewhere. The agenda concludes with a discus-
sion of the general technology that enables a
researcher to engage in biomaterial surface modi-
fication and a specific example using ideas and
technology discussed in this chapter.
BOX 8.2
A SCIENTIFIC
DEFINITION OF A
SURFACE
The outermost region of a material that is
chemically and/or energetically unique by
virtue of being located at a boundary.
is a simplified concept of the surface region. In
reality, of course, the surface region is three-
dimensional because atoms and molecules are
three-dimensional.
An important question asks just how thick
the surface region is. A useful answer to this
question is given in Box 8.2 . Accordingly, a sur-
face is not defined by an arbitrary thickness such
as a nanometer or micrometer but rather as a
chemical or energetic distinction from bulk-
phase properties. As long as the surface region
is a small portion of the total system, the
8 .2 THE SURFACE REGION
8.2.1 Ordinary and Scientific Definitions
The ordinary dictionary definition of a surface
given in Box 8.1 is effectively the same as that
used in surface science. A surface is the topmost
boundary of a material that has thickness no less
than the atoms or molecules that occupy this
boundary region. The mathematical definition
of a surface as a planar region with no thickness
 
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