Gadolinium-doped carbon quantum dots loaded magnetite nanoparticles as a bimodal nanoprobe for both fluorescence and magnetic resonance imaging

Nowadays, it is highly desired to develop dual-modal fluorescence and magnetic resonance imaging (FI/MRI) probes in medical imaging because it unites the respective advantages of each imaging modality: high sensitivity of FI and superior spatial resolution of MRI. In this study, a facile strategy to fabricate a new bimodal imaging nanoprobe (Gd-CQDs@N-Fe₃O₄) was reported by integrating the fluorescence ability of carbon quantum dots (CQDs) and T₁ and T₂ contrast-enhancing functionality of Gd(III) ions and Fe₃O₄ nanoparticles into a single hybrid nanostructure. The hybrid composites were investigated by FT-IR, XRD, TEM, XPS, VSM, and so on, which confirmed that Gd-CQDs@N-Fe₃O₄ nanoparticles were successfully obtained and exhibited superparamagnetic property at room temperature. The derived nanoprobes presented an excitation wavelength-independent emission behavior. In addition, r₁ and r₂ relaxivities of the synthesized imaging nanoprobes were measured to be 5.16 and 115.6 mM^{− 1} s^{− 1}, which nominated Gd-CQDs@N-Fe₃O₄ nanocomposites as a suitable T₁-T₂ contrast agent. The Gd-CQDs@N-Fe₃O₄ nanoparticles combining two synergetic imaging modalities showed great potential in FI/MRI dual-modal imaging for a more complementary and accurate detection.