Biomedical Engineering Reference
In-Depth Information
the local mechanical properties of callus and surrounding tissues [17-19].
Multifield measurement of bone tissues has also received recent attention
from a number of researchers [4,20-22].
In the relevant literature, piezoelectric signals have usually been measured
by charge amplifiers, which detected the polarized charges on bone surfaces
by transferring them to a capacitor in an instrument. This is a relatively simple
way to determine the quantitative relationships between the electric charge
and external force. However, this method cannot reveal the time-dependent
variation of the polarized charges in bone, during which the magnitude of
charges may influence the bone remodeling process or osteocyte viability.
Over the past decades, various new techniques have been developed and
employed to investigate the piezoelectric properties of bone tissue. Based
on the concept of converse piezoelectric effect, the piezoelectric coefficient
d
23
has been determined using a sensitive dilatometer [20]. A piezoelectric
force microscope and an atomic force microscope have also been employed
to measure piezoelectric properties of bone [21,22]. More recently, Hou, Fu,
and Qin [4] investigated the stretching-relaxation properties of bone piezo-
voltages. Fu et al. [23] studied the influence of shear stress on the signs of
piezovoltages in bone by means of three-point and four-point bending
experiments. In this chapter, our discussion focuses on the developments in
references 3-5 and 23.
9.2 Removal of Soft Tissue from Bone Samples
Cleaning of fresh bones to remove their soft tissues while preserving their
structural integrity is a basic, practical, and essential part of bone studies.
This section briefly summarizes the development presented in Yin et al. [5].
It describes the effects of water, trypsin, and detergent macerations on bone
microstructures and mechanical properties during the preparation process.
In particular, two typical laundry powders—one without enzymes and the
other with two enzymes—are used.
9.2.1 Removal of Soft Tissues
In Yin et al. [5], three maceration fluids containing different additives and
2 L of water are evaluated (Table 9.1) and compared with the same amount
of additive-free water. Solution A is additive-free water. Solution B contains
20 g trypsin (Sigma Aldrich, Australia). The molecular weight of trypsin is
23,800, and it consists of 223 amino acids. The pH value of trypsin is 7.8.
Solution C contains 40 g Surf laundry powder (Unilever, Australia). There
is no added enzyme in Surf laundry powder. The pH value of Solution C
is 11. Solution D contains 40 g Biozet laundry powder (KAO, Australia).
