Biomedical Engineering Reference
In-Depth Information
sample fluorescence, particularly when attempts were made to characterise the
organic phase of the tissue. Because of the presence of high fluorescence, very
noisy data were obtained and useful information was lost in the background.
In a study of synthetic carbonated apatites, Nelson and Featherstone [14]
employed chemical analysis, X-ray diffraction, and infrared and Raman
spectroscopy to characterise samples, which were prepared using a variety
of methods. Other studies on hydroxyapatite, bone, and related compounds
[15-20] broadly agreed with the spectral findings of these workers.
Composition of cortical bone tissue has been determined in the physiologic
state (i.e., without deproteination), as well as in the deproteinated state (which
isolates the mineral phase of the tissue). The spectra obtained are compared
with those reported by other workers [12,13]. Raman spectra obtained from
commercial hydroxyapatite have been compared with the inorganic matrix
(the natural apatite), which were considered in the context of previous stud-
ies [14-23] making it possible to compare and contrast in detail the spectra
from natural and synthetic calcium phosphate and to establish a correlation
between the spectral lines.
In this reported study, cortical bone was taken from the midshaft region
of human (56 years old, male) and sheep (mature bone) femoral tissue.
The tissue was obtained in a frozen state, at 0°C. Commercial synthetic
hydroxyapatite powder (P120 type) was obtained from Plasma Biota1 (UK).
Calcium carbonate, calcium phosphate, calcium hydroxide, and sodium
hydroxide samples were obtained from BDH (UK) for use as controls.
Preparation of bone Samples
Sample preparation in cases is extremely important, and it becomes even
more crucial when biological samples are involved. Cubes of cortical bone
tissues used in that study were prepared, measuring 4 mm along each axis.
The size was selected to fit into the sample holders used and provided a suf-
ficiently large surface area-to-volume ratio to ensure effective penetration of
the deproteinating agent into the tissue. At the same time, the samples were
large enough to be easily handled. Four samples were prepared: two from
the human tissue and two from the sheep tissue; one from each of these
groups was then deproteinated. The method of preparation involved cut-
ting the tissue using a small hacksaw and a diamond band saw (EXAKT
cutting-grinding system) with a recirculating water system. The time during
which the bone was exposed to room temperature (during the preparation
process) was kept to a minimum (10 min). The samples were refrozen as soon
as cutting was completed and then allowed to thaw for 30 min at room tem-
perature prior to spectrochemical analysis. The transverse faces of the cubes
(with respect to the long axis of the femur) were analysed.
The deproteination procedure used was based on that of Termine and
coworkers [16]. The deproteinating agent used (hydrazine) was anhydrous
to prevent changes to the mineral of the tissue. A prepared bone sample
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