Hydroxyapatite structures for tissue engineering applications have been produced by hydrothermal (HT) treatment of aragonite in the form of cuttlefish bone at 200 degrees C. Aragonite (CaCO(3)) monoliths were completely transformed into hydroxyapatite after 48 h of HT treatment. The substitution of CO(3) (2-) groups predominantly into the PO(4) (3-) sites of the Ca(10)(PO(4))(6)(OH)(2) structure was suggested by FT-IR spectroscopy and Rietveld structure refinement. The intensity of the nu(3)PO(4) (3-) bands increase, while the intensity of the nu(2)CO(3) (2-) bands decrease with the duration of HT treatment resulting in the formation of carbonate incorporating hydroxyapatite. The SEM micrographs have shown that the interconnected hollow structure with pillars connecting parallel lamellae in cuttlefish bone is maintained after conversion. Specific surface area (S (BET)) and total pore volume increased and mean pore size decreased by HT treatment.

Highly porous hydroxyapatite (Ca(10)(PO(4))(6)·(OH)(2), HA) was prepared through hydrothermal transformation of aragonitic cuttlefish bones (Sepia officinalis L. Adriatic Sea) in the temperature range from 140 to 220°C for 20 min to 48 h. The phase composition of converted hydroxyapatite was examined by quantitative X-ray diffraction (XRD) using Rietveld structure refinement and Fourier transform infrared spectroscopy (FTIR). Johnson-Mehl-Avrami (JMA) approach was used to follow the kinetics and mechanism of transformation. Diffusion controlled one dimensional growth of HA, predominantly along the a-axis, could be defined. FTIR spectroscopy determined B-type substitutions of CO(3) (2-) groups. The morphology and microstructure of converted HA was examined by scanning electron microscopy. The general architecture of cuttlefish bones was preserved after hydrothermal treatment and the cuttlefish bones retained its form with the same channel size (~80 × 300 μm). The formation of dandelion-like HA spheres with diameter from 3 to 8 μm were observed on the surface of lamellae, which further transformed into various radially oriented nanoplates and nanorods with an average diameter of about 200-300 nm and an average length of about 8-10 μm.

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Highly porous hydroxyapatite (Ca10(PO4)6(OH)2, HA) was prepared through hydrothermal (HT) transformation of aragonitic cuttlefish bones (Seppia Officinalis L. Adriatic Sea) in the temperature range from 140°C to 220°C for 20 minutes to 48 hours. Mechanism of hydrothermal transformation of bones was investigated by DTA/TG analyzer coupled online with FTIR spectrometric gas cell equipment (DTA-TG-EGA-FTIR analysis), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). DTA-TG-EGA-FTIR analysis have shown the release of CO2 at about 400°C, 680°C and 990°C. The first release could be attributed to organics not completely removed from the heat treated bones, and the second release to decomposition of unconverted aragonite, whereas, the third one could be attributed to CO3 2– groups incorporated in the structure of HA. The interconnecting porous morphology of the starting material (aragonite) was maintained during the HT treatment. The formation of dandelion-like HA spheres with diameter from 3 to 8 μm were observed, which further transformed into nanoplates and nanorods with an average diameter of about 200-300 nm and an average length of about 8-10 μm.