Cu-In-S/ZnS:Gd3+ quantum dots with isolated fluorescent and paramagnetic modules for dual-modality imaging in vivo

Gd3+-doped quantum dots (QDs) have been widely used as small-sized bifunctional contrast agents for fluorescence/magnetic resonance (FL/MR) dual-modality imaging. However, Gd3+ doping will always compromise the FL of host QDs. Therefore, balancing the Gd3+ doping and the optical properties of QDs is crucial for constructing high-performance bifunctional nanoprobes. Additionally, most paramagnetic QDs are synthesized in the organic phase and need to be transferred to the aqueous phase for bioimaging. Herein, ingeniously designed shell-doped Cu-In-S/ZnS:Gd3+ QDs have been prepared in the aqueous phase. It has been demonstrated that isolating paramagnetic Gd3+ from fluorescent Cu-In-S core via doping Gd3+ into ZnS shell not only avoided the decrease of FL quantum yield (QY), but also ensured the water accessibility of paramagnetic Gd3+ ions, by which the FL QY and r1 relaxivity of Cu-In-S/ZnS:Gd3+ QDs achieved as much as 15.6% and 15.33 mM(-1)center dot s(-1), respectively. These high-performance QDs with excellent stability, low biotoxicity, and good tumor permeability were successfully applied for in vivo tumor FL/MR dual-modality imaging, and have shown significant potential in the precision detection and diagnosis of diseases.