Surface Functionalized Multifunctional Gd₂O₃–Fluorescein Composite Nanorods for Redox Responsive Drug Delivery and Imaging Applications

We have developed multifunctional Gd2O3–fluorescein based magnetic–fluorescent composite nanorods with small, uniform shape and size distribution and excellent colloidal stability for multimodal imaging and redox responsive drug delivery applications. Gd2O3 nanorods have been synthesized via high temperature colloidal route, and composite development has been achieved via one-step polyacrylate coating. This unique coating approach provides controlled surface functional groups along with near zwitterionic surface charge. For redox responsive drug loading, hydrophilic drug daunorubicin has been modified with disulfide linkage and loaded with the composite nanorods via covalent linkage. High drug loading (∼82%) has been observed with excellent redox responsive release behavior. These composite nanorods have been used as multimodal imaging probe, for fluorescence imaging as well as magnetic resonance imaging (MRI). Fluorescence imaging of the composite nanorods inside cancer-positive KB cells exhibit efficient cellular internalization and drug delivery with high cytotoxic effect. These surface functionalized composite nanorods, having small size, excellent colloidal stability, high drug loading capability, and redox responsive release behavior along with multimodal imaging potential, can serve as a prospective nano-biomaterial in drug delivery and imaging purposes.