Colloidal apatite nanoparticles exhibiting luminescence and magnetic susceptibility
A. Nickel, K.H. Prakash, M. Pedulla, R. Kumar
Montana Tech, US
Abstract:Hydroxyapatite (HA) has been recognized for some time as a potential candidate for engineering hard-tissue replacements and drug and gene delivery systems. However, the inability to collidally disperse nano-HA (nHA), and perhaps create primary nHA building blocks that can be utilized for bottom-up assembly, has been its Achilles heel. This work presents an effective way to synthesize highly dispersed colloidal nHA particles by controlled aging of a calcium phosphate gel in conjunction with citrate molecules. A range of multi-functional traits (e.g. simultaneous magnetic and luminescent behavior) is demonstrated by doping the apatite lattice in situ with metal ions. The as-synthesized suspensions (2g/L) were transparent and consisted of 10-20 nm spheriodal primary nHA, as revealed by TEM and FEM. Controls settled within 30 minutes, while dispersed nHA suspensions exhibited stability for months. XRD coupled with Rietveld refinement revealed size and shape modification of nHA as a function of citrate concentration. FTIR spectroscopy traced the evolution of the precursor compounds into nHA particulates. A possible molecular adsorption scenario is presented and a possible mechanism proposed. In effect the work demonstrates the possibility of synthesizing multi-functional nHA building blocks that can perhaps be more suitable for potential bio-medical applications stated earlier.