"Nanotheranostics" for Tumor Imaging and Targeted Drug Delivery.

Abstract

The magnetic resonance imaging (MRI) technique is a promising tool that improves cancer detection, facilitates diagnosis and monitors therapeutic effects. Superparamagnetic iron oxide nanoparticles (SPIOs) have emerged as MRI contrast agents for tumor imaging and as potential vectors for targeted anti-cancer drug delivery; nevertheless, the application of SPIOs has been hampered due to a lack of specificity to tumor tissues and premature drug release. This project aims at developing multifunctional SPIOs for both cancer imaging and targeted drug delivery via conjugation of tumor specific antibodies with SPIOs. The application of anti-TAG-72 antibodies as tumor targeting modalities was evaluated in cultured colorectal cancer cells and in xenograft models by using fluorescent imaging and positron emission tomography (PET) imaging. It was demonstrated that antibody-labeled SPIOs were superior imaging agents and drug carriers for increased tumor specificity. The regulation and kinetics of intracellular drug release from SPIOs were explored by means of fluorescence imaging. In vitro and in vivo fluorescence resonance energy transfer (FRET) imaging was employed to investigate the mechanisms of premature drug release from nanocarriers. The large volume and high hydrophobicity of cell membranes were found to play an important role in premature drug release. The encapsulation of SPIOs into nanocarriers decreased drug release in a dose-dependent mode. This study provided future opportunities to improve the efficiency of nanocarriers by exploring the mechanism of drug release and disassembly of SPIO-loaded polymeric nanoparticles.