Surface modification of Mg-doped fluoridated hydroxyapatite nanoparticles using bioactive amino acids as the coupling agent for biomedical applications

Abstract

Hydroxyapatite (HA) has been extensively utilized in the field of biomaterials as a bioactive ceramic. Development of modified-HA by the substitution of Ca ions and OH⁻ groups not only makes its chemical composition similar to that of the natural bone tissue, but also improves the in vitro behavior of commercially synthesized HA. Accordingly, magnesium-fluoridated hydroxyapatite nanoparticles (Mg-FHA NPs) have been recently developed. However, due to the high surface energy of such NPs, they cannot be well dispersed in a biopolymer matrix to prepare a polymer/ceramic composite, which is usually demanded for tissue engineering applications. To overcome this shortcoming, the surface of Mg-FHA NPs was modified using a few well-known natural amino acids as the cost-effective and environment-friendly biomaterials in the present research. L-leucine, L-isoleucine, L-methionine, L-phenylalanine, L-tyrosine and L-valine amino acids were employed as the coupling agents and surface modification of Mg-FHA NPs was carried out by means of sonication technique. The results confirmed that using amino acid molecules led to the uniform dispersion of Mg-FHA NPs in the organic environment by making the surface of NPs hydrophobic, although the length and chemical reactivity of amino acid molecules affected the efficiency of NPs dispersion. The uniform distribution of Mg-FHA NPs could be regarded as a desired condition for polymer/ceramic composite preparation, with high applicability for biomedical purposes.