Gadolinium-doped fluorescent carbon quantum dots as MRI contrast agents and fluorescent probes

In this research passivated gadolinium-doped carbon quantum dots (Gd-doped CQDs) were synthesized from starch by a hydrothermal method. The X-ray diffraction (XRD) pattern of the Gd-doped CQDs showed the formation of highly amorphous carbon. The Fourier transform infrared spectroscopy (FTIR) results suggested that the CQDs are functionalized with C-N and N-H bonds. The synthesized CQDs with a size distribution of 2-8 nm have an absorption peak at 271 nm in UV-Visible spectroscopy (UV-Vis). The photoluminescence (PL) in CQDs was dependent on the excitation wavelength. The QY of the synthesized CQDs was calculated to be 13.2%. The Gd-doped CQDs exhibited sustained PL in ionic solutions with different ionic strengths and different temperatures up to 65 degrees C. Fluorescence imaging on mouse C-34/connective tissue-L929 cells confirmed that Gd-doped CQDs could be well distributed over the cytoplasm. The magnetic resonance imaging (MRI) showed that the Gd-doped CQDs have extremely high longitudinal and transverse relaxivity values of as high as 218.28 mM(-1) s(-1) and 364.68 mM(-1) s(-1). The synthesized Gd-doped CQDs are promising candidates as multifunctional imaging probes and MRI contrast agents in biomedical diagnosis and brain mapping applications.

Automated summary

In this study, gadolinium-doped carbon quantum dots (Gd-doped CQDs) were synthesized using a hydrothermal method and characterized. The synthesized CQDs exhibited highly amorphous carbon structure, functionalized with C-N and N-H bonds. UV-Vis spectroscopy showed an absorption peak in the synthesized CQDs, and the photoluminescence (PL) depended on the excitation wavelength. The Gd-doped CQDs showed sustained PL in ionic solutions with different ionic strengths and temperatures. Additionally, the Gd-doped CQDs were well distributed in cells and showed excellent imaging performance in MRI, making them promising for biomedical diagnosis and brain mapping applications.