Hydroxyapatite and chondroitin sulfate from Prionace glauca shark jaw:
Physicochemical and structural characterization
Abstract
In the present work, the potential of the blue shark (Prionace glauca)
jaw as a source of both bioapatite and chondroitin sulfate is explored.
A chemical and structural characterization of this fishing by-product by
Scanning Electron Microscopy (SEM), Electron Dispersive Spectroscopy
(EDS), FT-Raman spectroscopy and X-Ray Diffraction (XRD) was carried
out. The sandwich-type structure in cross section of the jaw based on
alternate layers with prevalence in mineralized or organic tissue is
shown and these bands respectively confirmed as hydroxyapatite (HA) or
CS-enriched zones. As result of this, an optimized process in sequential
steps for the recovery of both biomaterials and their purification
process is proposed, by combining enzymatic proteolysis, chemical
precipitation and separation using ultrafiltration membrane for CS
production together with controlled thermal treatment for hydroxyapatite
obtaining. The purified CS was characterized by Gel Permeation
Chromatography (GPC), Nuclear Magnetic Resonance (NMR) and Strong Anion
Exchange Chromatography (SAX-HPLC), revealing a polymeric material with
a molecular weight of 67kDa and prevalent 6S-GalNAc sulfation (68%),
followed by 4S-GalNAc (13%), a significant proportion of disulfated
disaccharides (12%) and only 7% of non-sulfated units. In the case of
the bioapatite a purified biphasic 60:40 porous calcium phosphate of
hydroxyapatite: whitlockite/β-TCP was confirmed. Hydroxyapatite as major
component (85%) was also obtained for jaws directly subjected to the
thermal treatment. This proved the influence of the enzymatic hydrolysis
and centrifugation on the composition of the mineral fraction.