13C-engineered carbon quantum dots for in vivo magnetic resonance and fluorescence dual-response

C-13-engineered carbon quantum dots (C-13-QDs) were used as magnetic resonance (MR) and fluorescence dual-response probe. The enhanced C-13-MR signal was observed at 171 ppm from carboxylic and carboxyl carbons in C-13-QDs with 160-fold improvement on signal-to-noise ratio even when no hyperpolarization was applied, whereas the intrinsic fluorescence of C-QDs was still maintained. The stable MR and fluorescence dual-response was successfully used for long-term observation of zebrafish embryonic development. Cross-validation between MR and fluorescence confirmed the distribution of C-13-QD in zebrafish. C-13-MR provides specific information about the presence, magnitude, and progression of 13C-QDs by defining MR intensity, whereas fluorescence reveals the location of C-13-QD5 with its high sensitivity. C-13-MR and fluorescence was simultaneously observed within C-13-QDs, and this work may expand the applications of isotope-engineered nanomaterials.