Hydroxyapatite/ovalbumin composite particles as model protein carriers for bone tissue engineering: I. Synthesis and characterization

Hydroxyapatite (HAp) nanoparticles were synthesized from the co-precipitation reaction between calcium oxide from discarded egg shells and phosphoric acid in the absence and the presence of ovalbumin (OVA). 2-Amino-2-hydroxymethyl-propane-1,3-diol (tris-base) was used to control the pH during the co-precipitation (i.e., 7–9). The formation of HAp was confirmed by X-ray diffraction analysis, while both the Fourier-transform infrared spectroscopy and the thermogravimetric analysis confirmed the existence of OVA within the HAp–OVA particles. The crystallite sizes of the individual crystalline entities within the HAp and the HAp–OVA particles were approximated from the (002) reflection peaks by means of the Scherrer's equation. The average particle sizes of the HAp and the HAp–OVA particles were measured by particle size analysis. Transmission electron microscopy revealed that these particles were aggregates of rod-like HAp nanocrystals, whereas scanning electron microscopy revealed that these particles ultimately formed into larger aggregates. Lastly, the decrease in the pH during the precipitation process and the presence of OVA were responsible for the observed increase in the values of pore size, BET specific surface area, and pore volume of the resulting HAp particles.

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► CaO from discarded egg shells was used as the source of calcium.
► Precipitation of CaO with H3PO4 into HAp was achieved with tris-base
► Precipitation was done with or without ovalbumin (OVA)
► HAp–OVA composite particles are envisioned as model carriers of proteins
► 2nd work in the series showed that release of OVA was good for up to 21 days