Page 326 - Vibrational Spectroscopic Imaging for Biomedical Applications

300 Cha pte r T e n

This chapter describes some microscopic aspects of internal stress
states in which biomaterials quality is directly associated with
increased fracture risk, sometimes despite improved chemical purity
and structural design. Raman techniques for the measurement of bio-
materials quality will be described and discussed together with how
these have advanced our understanding of the microscopic mecha-
nisms by which biomaterials strength may be improved.

10.1 Introduction
Understanding modern biomedical materials requires a multidisci-
plinary approach involving characterizations by different analytical
approaches and advanced spectroscopic techniques. Studies of new
processing procedures directed at the preparation of biocompatible
materials caused an increased interest in natural biomaterials and in
new investigation methods that allow analyzing their behavior in
order to rationally explain their unique properties. Traditionally, the
applicability of implant materials in medicine is determined by test-
ing procedures that thoroughly examine structural reliability, bio-
compatibility, cellular response, and lifetime in the human body. In
case of inorganic materials for bone or joint replacement, it is neces-
sary to complement biological methods with mechanical studies of
structural resistance and durability in the presence of a biological
environment. These studies should also give information about phase
composition and its interaction with structural properties, as well as
about the kinetics of fracture propagation. Vibrational spectroscopy
allows studying the processes occurring in biomaterials under strain
and analyzing the interaction between implant and biological sys-
1,2
tems. Vibrational spectroscopy methods have been extensively used
for in vitro and in vivo investigations of degradation mechanisms and
3–5
kinetics of several biomedical devices; they have also been used for
characterizing the crystalline and amorphous domains in biomineral-
6,7
ization processes. In particular, Raman spectroscopy has proved to
be a valuable tool in the field of biomaterials engineering, allowing
the study of the processes occurring during their preparation and
8
use. When coupled with an optical microscope, Raman spectroscopy
has been widely applied to determine phase compositions, to ana-
9
7
lyze the degree of crystallinity in bone tissue, and the rate of tissue
regeneration. Raman mapping on the microscopic scale is very
10
helpful in the study of biomaterial surfaces and events at biomaterial
surfaces such as wear and elastic/plastic strain intensification. 1,2,11 A
Raman spectrum typically contains a large amount of information in
its sharp, well-resolved spectral bands. The band spectral positions,
intensities, and shapes provide an interpretable and fairly unique fin-
gerprint for qualitative analysis. The Raman microscopy provides
us with the essential information needed to verify the reliability of