Facile synthesis of hydroxyapatite nanoparticles mimicking biological apatite from eggshells for bone-tissue engineering

A facile synthesis of hydroxyapatite (HAp) nanoparticles that mimicked biological apatite by utilizing eggshells as a bio-calcium precursor was presented via the hydrothermal method and with the assistance of cetyl-trimethylammonium bromide for bone-tissue engineering. The synthesized HAp was characterized by the X-ray powder diffraction method, Fourier transform infrared spectroscopy, field emission scanning microscopy, energy-dispersive X-ray spectroscopy, and nitrogen adsorption-desorption isotherms. The HAp nanoparticles were produced in film and pellet forms to determine their biomineralization and protein adsorption through in vitro studies in simulated body fluids and minimum essential medium supplemented with fetal bovine serum, respectively. A pure HAp nanocrystalline phase with rod-shaped nanoparticles of 161 nm in mean length and 52 nm in mean diameter was produced. The HAp was revealed to be a carbonated HAp exhibiting A-and B-type CO32- substitutions with CO32- content of 2.14 +/- 1.36 wt.%, trace amounts of some important elements (Mg, Na, and K), and Ca/P atomic ratio of 1.54, thereby confirming that the HAp resembled the biological apatite in terms of morphology, structure, and composition. The HAp showed high biomineralization capability with the quick release of a double layer of bone-like apatite after 3 days in SBF and extremely high protein adsorption with 1213 +/- 178 mu g of proteins adsorbed on the HAp surface after 24 h. The HAp material had high bioactivity and cell affinity (cell adhesion, spreading, and proliferation). Thus, it has potential as a biomaterial for fabrication of BTE scaffolds. To our knowledge, this article is the first detailed study on biological tests of the HAp material derived from eggshells.