Photoluminescence and doping mechanism of theranostic Eu(3+)/Fe(3+) dual-doped hydroxyapatite nanoparticles

Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu(3+) doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca(2+) with Fe(3+) in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu(3+) and Fe(3+) doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu(3+) and Fe(3+) doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu(3+) and Fe(3+), and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.