Gadolinium-doped carbon dots with high quantum yield as an effective fluorescence and magnetic resonance bimodal imaging probe

It is highly desired to develop the dual-modality fluorescence and magnetic resonance imaging (MRI) probes in medical imaging because it can provide high-resolution macroscopical anatomical information and high-sensitivity microscopical optical signal simultaneously. In this study, harmless gadolinium-doped carbon dots (Gd-CDs) were prepared via a convenient one-pot hydrothermal approach for fluorescence/MR bimodal imaging. The derived Gd-CDs exhibit enhanced blue photoluminescence with a quantum yield as high as 69.86% and significantly improved longitudinal relaxivity (r₁ = 14.33 mM⁻¹ s⁻¹, 0.5 T) in comparison with commercial Magnevist (Gd-DTPA, r₁ = 4.5 mM⁻¹ s⁻¹, 0.5 T). Here Gd³⁺ions are simply chelated onto CDs by carboxyl groups. Moreover, unlike the previous reports, Gd³⁺chelation does not perturb core optical properties of CDs. Excellent water solubility, good cell-membrane permeability and negligible cytotoxicity make Gd-CDs an ideal dual-modal fluorescence/MR imaging nanoprobe, suggesting its potential and significance in practical biological and clinic applications in the future.