Preparation of luminescent and mesoporous Eu3+/Tb3+ doped calcium silicate microspheres as drug carriers via a template route

Abstract

Luminescent and mesoporous Eu³⁺/Tb³⁺ doped calcium silicate microspheres (LMCS) were synthesized by using mesoporous silica spheres as the templates. The LMCS and drug-loaded samples were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N₂adsorption/desorption, and photoluminescence (PL) spectra. The results reveal that the LMCS have uniform spherical morphology with a diameter around 400 nm and the mesopore size of 6 nm. The prepared samples exhibit little cytotoxicity at concentrations below 5 mg mL⁻¹via MTT assay. In addition, drug storage/release properties of the LMCS were demonstrated for ibuprofen (IBU). The obtained LMCS can be used to encapsulate drugs and release them. Under excitation by UV light, the IBU-loaded samples still show the characteristic ⁵D₀–⁷F_1–3 emission lines of Eu³⁺ and the characteristic ⁵D₄–⁷F_3–6 emission lines of Tb³⁺. The PL intensity of Eu³⁺ in the drug carrier system increases with the cumulative released amount of IBU, making the drug release able to be tracked or monitored by the change of luminescence of Eu³⁺. The LMCS reported here with mesoporous structure, good biocompatibility and luminescent property can be a promising drug delivery carrier.