Multifunctional chitosan modified Gd2O3: Yb3+,Er3+@nSiO2@mSiO2 core/shell nanoparticles for pH responsive drug delivery and bioimaging

Gd2O3: Yb3+, Er3+@ nSiO(2)@ mSiO(2) (Gd@mSi) core/shell structure nanospheres were synthesized through a sol-gel method. Then biocompatible polysaccharide chitosan (CS) was grafted onto the surface of the nanoparticles to fabricate a pH responsive CS@Gd@mSi system. Furthermore, cancer targeting ligand folic acid (FA) was modified through the abundant amino groups on the chitosan polymer shell. The nanospheres with a Gd2O3: Yb3+, Er3+ core can be candidates for T-1-weighted magnetic resonance imaging (MRI) contrast agents. The CS decorated nanocomposites showing good biocompatibility and red emission under 980 nm laser excitation can be potential candidates for bioimaging in vitro. FA modified nanospheres loaded with doxorubicin hydrochloride (DOX) show higher cytotoxicity for HeLa cells in vitro compared with those nanoparticles with chitosan shells only and pure DOX. The CS@Gd@mSi system can be a potential drug carrier with MRI, UCL, and finely controlled pH-dependent drug release properties.