Tuneable carbon dots coated iron oxide nanoparticles as superior T ₁ contrast agent for multimodal imaging

Multifunctional hybrid nanoparticles garner heightened interest for prospective biomedical applications, including medical imaging and medication administration, owing to their synergistic benefits of constituent components. Therefore, we demonstrated an optimized protocol for synthesizing magnetofluorescent nanohybrids comprising fluorescent carbon dots with magnetic nanoparticles.

Carbon dot-coated iron oxide nanoparticles (CDs@Fe₂O₃) were synthesized with varying citric acid concentrations by a one-pot hydrothermal synthesis method for the development of a low-cost and biocompatible contrast agent (CA) for enhanced multimodal imaging (fluorescent and T ₁ and T ₂ weighted magnetic resonance imaging (MRI)) to replace the conventional CAs.

The physicochemical characterization of the synthesized CDs@Fe₂O₃ revealed that 3 g of citric acid used for the synthesis of nanoparticles, keeping Fe(II) and Fe(III) ratio 1:2 provides higher stability of -78 mV zeta potential, saturation magnetization of 24 emu/g, with a hydrodynamic diameter of 68 nm. Carbon coating affects surface spins on Fe₂O₃, resulting in fewer surface-based relaxation centres, making T ₁ relaxation relatively more prominent. Furthermore, the surface-engineered iron oxide NPs are efficient in producing both T ₁ and T ₂ weighted MRI as well as fluorescence-based imaging. The molar relaxivity and molar radiant efficiency derived from phantom studies demonstrate their effectiveness in multimodal medical imaging. The cytotoxicity assay, haemolysis assay, haematology, and histopathology studies show that the optimized CDs@Fe₂O₃ are biocompatible, haemocompatible, and negligibly toxic.

We can conclude the significant potency of CDs@Fe₂O₃ for multimodal diagnosis.