Facile preparation of gadolinium(iii) chelates functionalized carbon quantum dot-based contrast agent for magnetic resonance/fluorescence multimodal imaging.

Suffering from high inherent toxicity generated from heavy metals in semiconductor quantum dots and a complex preparation process, the medical application of conventional gadolinium(iii)/semiconductor quantum dot-based magnetic resonance/fluorescence multimodal imaging (MRI/FI) contrast agent has been limited. In this paper, a new kind of biocompatible carbon quantum dot functionalized by gadolinium(iii) chelates (named as Gd(iii)/CQDs) was obtained through one-step pyrolysis of gadopentetate monomeglumine, which provides simultaneously a carbon source and a gadolinium(iii) source. The Gd(iii)/CQDs show good magnetic resonance response and photoluminescence properties with longitudinal relaxation rate and quantum yield of 5.5-6.4 mM L-1 S-1 [Gd(iii)%, 0.5 mM] and 2.6-8.9%, respectively. The Gd(iii)/CQDs with diameters in the range of 2-3 nm can be well dispersed in deionized water, phosphate-buffered saline buffer solution or culture medium to form a stable dispersion, which with low cytotoxicity can penetrate into cells and show green fluorescence (excitation at 488 nm), presenting a great potential to be used as an MRI/FI contrast agent.