Influence of Biphasic Calcium Phosphate Incorporation Into Alginate Matrices

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Biphasic calcium phosphate (BCP), containing β-tricalcium phosphate and hydroxyapatite, was synthesized by co-precipitation method to obtain a biomimetic artificial bone-like composite using calcium nitrate tetrahydrate [Ca(NO3)∙4H2O] as calcium precursor and ammonium dihydrogen phosphate (NH4H2PO4) as phosphorous precursor, maintaining Ca/P ratio of 1.67. The synthesized biphasic calcium phosphate mixture was dispersed in a sodium alginate (Alg) matrix dissolved in distilled water and lyophilized. The chemical structure, possible interactions between components and morphology of the obtained powder and scaffolds were studied through Fourier transform infrared (FT- IR) spectroscopy, X-ray diffraction (XRD) thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) in order to observe the interactions between BCP and the polymer. The particle size of the powder was also analyzed using the dynamic light scattering (DLS) analysis. Calcined powder had a particle size of 1.8 �m. In addition to the low crystalline hydroxyapatite (HA), as the main phase in the dried samples, β-tricalcium phosphate (β-TCP) was formed after the thermal treatment of 1000˚C as shown by XRD and FT-IR. The obtained composite material presented a highly porous microstructure with interconnected layers where the BCP particles were well dispersed. The micro-structure of the scaffolds was influenced with the change in pore dimensions and rearrangement of the layers due to the incorporation of the BCP particles and by the treatment of the scaffolds with CaCl2.
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