One-pot synthesis of gadolinium(III) doped carbon dots for fluorescence/magnetic resonance bimodal imaging

A combination of fluorescence and magnetic resonance imaging (MRI) can provide high-resolution macroscopical anatomical information and high-sensitivity microscopical optical signal simultaneously. In this work, harmless gadolinium(III) doped carbon dots are synthesized in a convenient one-pot hydrothermal approach and used for fluorescence/magnetic resonance multimodal imaging. Unlike typical carbon dots, TEM analysis shows that the carbon dots are particles with irregular shape. Furthermore, Fourier-transform infrared (FTIR) spectra demonstrated structural difference between gadolinium-undoped and doped carbon dots. Nonetheless, the gadolinium-doped carbon dots exhibit strong and stable fluorescence with excitation-dependent emission behavior. Moreover, as an MRI contrast agent, the gadolinium-doped carbon dots represent considerable magnetic resonance properties with a longitudinal relaxation rate of 14.08 mM(-1) s(-1). In addition, cytotoxicity study reveals that the gadolinium-doped carbon dots show very low toxicity to NCI-H446 cells with an IC50 value of 6.28 mg mL(-1). Direct application in cell labeling and in vivo MRI suggests that the gadolinium-doped carbon dots are dual functional fluorescent/MRI probes with excellent biocompatibility.