131I-labeled polyethylenimine-entrapped gold nanoparticles for targeted tumor SPECT/CT imaging and radionuclide therapy

Purpose: Polyethylenimine (PEI) has been widely used as a versatile template to develop multifunctional nanosystems for disease diagnosis and treatment. In this study, we manufactured iodine-131 (I-131)-labeled PEI-entrapped gold nanoparticles (Au PENPs) as a novel nanoprobe for single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and radionuclide therapy. Materials and methods: PEI was PEGylated and sequentially conjugated with Buthus martensii Karsch chlorotoxin (BmK CT, a tumor-specific ligand which can selectively bind to MMP2), 3-(4'-hydroxyphenyl) propionic acid-OSu (HPAO), and fluorescein isothiocyanate to form the multifunctional PEI template for entrapment of Au NPs. Then, the PEI surface was radiolabeled with I-131 via HPAO to produce the novel nanoprobe (BmK CT-Au PENPs-I-131). Results: The synthesized multifunctional Au PENPs before and after I-131 radiolabeling were well-characterized as follows: structure, X-ray attenuation coefficient, colloid stability, cytocompatibility, and radiochemical stability in vitro. Furthermore, BmK CT-Au PENPs-I-131 were suitable for targeted SPECT/CT imaging and radionuclide therapy of tumor cells in vitro and in a xenograft tumor model in vivo. Conclusion: The developed multifunctional Au PENPs are a promising theranostic platform for targeted imaging and treatment of different MMP2-overexpressing tumors.