Functional Modular Stacking Nanoprobes Based on Bimetallic Doped Carbon Dots for Multimodal Bioimaging and...

Carbon dots (CDs) have emerged as promising nanoplatforms for biomedical applications due to their unique physicochemical properties. Specifically, the modular assembly strategy allows for the construction of multifunctional carbon dots that combine multiple diagnostic and therapeutic modalities. In this study, gadolinium/holmium-doped gallic acid-based carbon dots (Gd/Ho-GCDs) using a microwave-assisted one-step synthesis protocol is developed. The precursors included citric acid, urea, gallic acid (GA), HoCl₃·6H₂O, and GdCl₃·6H₂O. Comprehensive characterization showed that the synthesized Gd/Ho-GCDs displayed excellent aqueous dispersibility and has a highly monodisperse spherical morphology, with an average diameter of 4.8 nm. Notably, the modular integration of functional components endowed the Gd/Ho-GCDs with trimodal imaging functionality, including fluorescence emission, computed tomography (CT) capability (slope = 13.589 HU mM^-1), and dual T1/T2-weighted magnetic resonance imaging (MRI) contrast with high relaxivities (r1 = 11.656 mM^-1 s^-1, r2 = 15.021 mM^-1 s^-1). Furthermore, the Gd/Ho-GCDs exhibited exceptional biocompatibility and outstanding photothermal conversion efficiency. In vivo evaluations confirmed the dual-modality therapeutic efficacy of Gd/Ho-GCDs, which achieved significant tumor growth inhibition through a synergistic combination of gallic acid-mediated chemotherapy and photothermal ablation. This modular engineering approach establishes a new paradigm for developing multifunctional theranostic platforms, potentially advancing the clinical translation of integrated diagnosis and treatment systems.