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Collagen/silicocarnotite composites, cross-linked with chondroitin sulphate: In vitro bioactivity

Radev Lachezar (University of Chemical Technology and Metallurgy, Sofia, Bulgaria)
Hristov Vladimir (University of Chemical Technology and Metallurgy, Sofia, Bulgaria)
Michailova Irena (University of Chemical Technology and Metallurgy, Sofia, Bulgaria)
Fernandes Maria H.V. (University of Aveiro and CICECO, Aveiro, Portugal)
Salvado Isabel M.M. (University of Aveiro and CICECO, Aveiro, Portugal)

In this work we present the experimental results on synthesis, structure evolution and in vitro bioactivity of collagen- silicocarnotite-chondroitin sulphate composites. The obtained samples were synthesised by mixing collagen (C) and silicocarnotite (S) powder with C:S ratio of 75:25 and 25:75 wt.% in the presence of chondroitin sulphate (ChS). Collagen was diluted in 5M CH3COOH before mixing. The obtained materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) before and after in vitro test in 1.5 simulated body fluid. XRD of synthesized samples showed that before immersion carbonate containing hydroxyapatite (CO3HA) were formed in situ in the composites. FTIR depicts the presence of HPO4 2- and the 'red shift' of COO- and SO3 - from ChS was also observed. This 'red shift' could be attributed that the ChS prefers to chelate Ca2+ from partially dissolved S powder. SEM of the prepared samples show the presence of nanosized hydroxyapatite (HA) whiskers and flower-like HA assemblies. After in vitro test, XRD proved the presence of HA with well-defined crystallinity. According to the FTIR results B-type CO3HA can be observed. SEM of the precipitated layers show the presence of HA spheres. Inductively coupled plasma atomic emission spectroscopy results lead to a conclusion that after in vitro test of the prepared composites silicon containing carbonate substituted hydroxyapatite (Si-CO3HA) may be formed on the surface of the immersed samples.

Keywords: silicocarnotite, collagen, chondroitin sulphate, hydroxyapatite whiskers, in vitro bioactivity