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Development of Theranostic Nanoprobes Based on Gd-Doped CdSe QDs Radiolabeled with 177Lu
Arezou Karimian1, Asghar Hadadi1, Samaneh Zolghadri2
1Department of Medical Radiation Engineering, SR.C., Islamic Azad University, Tehran, Iran.
Purpose:
Hybrid imaging platforms integrating multiple modalities provide synergistic advantages by combining anatomical, functional, and molecular information. The aim of this study was to develop and evaluate a theranostic nanoprobe based on gadolinium-doped cadmium selenide quantum dots (Gd-CdSe QDs) modified with thioglycolic acid (TGA) and radiolabeled with 177Lu for potential biomedical applications.
Methods:
Gd-CdSe QDs were synthesized via a three-step aqueous-phase method and subsequently characterized for their structural and optical properties. The QDs were surface-modified with TGA and radiolabeled with 177Lu under mild, chelator-free conditions. Physicochemical characterization included particle size, fluorescence properties, and quantum yield. Cytotoxicity was evaluated in vitro, while biodistribution and imaging performance were studied in both normal and tumor-bearing mice using fluorescence imaging (FLI), magnetic resonance imaging (MRI), and single-photon emission computed tomography (SPECT).
Results:
The Gd-CdSe QDs exhibited a narrow size distribution (~ 3.5 nm), strong fluorescence emission (λem ≈ 610 nm), high photostability, and a quantum yield (QY) of ~ 50%. Radiolabeling with 177Lu achieved > 99% radiochemical purity (RCP) without the need for chelators. Cytotoxicity assays indicated acceptable biocompatibility at low concentrations with dose-dependent effects. In vivo biodistribution revealed predominant hepatic uptake and notable tumor accumulation, attributed to retention effects. MRI and SPECT imaging confirmed dual-modality tumor visualization and accumulation of the nanoprobe at tumor sites.
Conclusion:
The TGA-modified Gd-CdSe QDs radiolabeled with 177Lu demonstrated favorable physicochemical properties, biocompatibility, and multimodal imaging capabilities. This multifunctional trimodal platform (FLI/MRI/SPECT) with potential for therapy shows strong potential for preclinical applications in cancer diagnosis and image-guided therapy development.
