In this study, luminescent and magnetic core/shell Gd1-x-yCexTbyBO3@SiO2 nanoparticles were synthesized and used to design a drug delivery system for Celecoxib (CLX). CLX was chosen as the model drug because it is a nonsteroidal anti-inflammatory drug that is highly hydrophobic with relatively low bioavailability. The core was synthesized by Pechini sol-gel method and silica coating was carried out by a Modified Stöber method. Drug loading was carried out in ethanol with high efficiency and an improved drug dissolution was obtained in phosphate-buffered saline (PBS) at pH 7.4. Dissolution rate of CLX adsorbed onto the drug carrier at different pH conditions were examined and compared.
The obtained core particles had a diameter of about 240 nm and core/shell particles had a diameter of about 300 nm. The core/shell particles possessed high luminescence intensity and soft magnetic properties. Drug loading was carried out in ethanol with 12.7% loading efficiency and a substantial decrease of about 8% in photoluminescence intensity was observed in drug loaded samples, which made the quantification of the released drug possible by comparing the photoluminescence intensities. The solubility of the drug was enhanced when compared to crystalline CLX, a sustained release profile was achieved and increasing luminescence intensity was observed during drug release. 55% of the loaded drug was released after 72 h in PBS at pH 7.4 while 20% drug release was observed in a pH 5.5 solution. Drug release at pH 5.5 followed a first order release kinetic model while the release at pH 7.4 followed a Higuchi's kinetic model with Fickian diffusion mechanism. An in vitro loss in cell viability with CLX loaded carrier was observed for the colon cancer cell line HCT-116. These results suggest that the designed drug carrier has promising applications for poorly soluble drugs with improved bioavailability, in addition to its application as a bioimaging agent in fluorescence microscopy and magnetic resonance imaging.