Synthesis and Biological Properties of Alanine-Grafted Hydroxyapatite Nanoparticles

Hydroxyapatite attracts great attention as hard tissues implant material for bones and teeth. Its application in reconstructive medicine depends on its biocompatibility, which is in a function of composition and surface properties. The insertion of a protein element in the composition of implants can improve the cell adhesion and the osseointegration. Having this in mind, the proposal of this work was to develop L-alanine-grafted hydroxyapatite nanoparticles and to study their biocompatibility. Two L-alanine sources and three grafting methods were used for hydroxyapatite surface functionalization. The efficiency of grafting was determined based on X-ray powder diffraction, Fourier-transform infrared spectroscopy, thermal analyses, and field-emission scanning electron microscopy. The results indicated the formation of hydroxyapatite with 8-25 wt% of organic content, depending on the grafting method. Protein adsorption, cell adhesion, and viability studies were carried out to evaluate biological properties of grafted materials. The viability of MG-63 human osteoblastic cells following 24 h incubation with the alanine-grafted hydroxyapatite samples is well preserved, being in all cases above the viability of cells incubated with hydroxyapatite. The alanine-grafted hydroxyapatite prepared in situ and by simple mixture showed higher protein adsorption and cell adhesion, respectively, indicating their potential toward use in regenerative medicine.