Broadband excitable NIR-II luminescent nano-bioprobes based on CuInSe2 quantum dots for the detection of circulating tumor cells

Biosensing of circulating tumor cells (CTCs) is of vital significance in cancer theranostics. Thus, the development of highly efficient luminescent nano-bioprobes is imperative to meet the growing demand of CTCs-related clinical diagnosis and biomedical research. Herein, we exquisitely manipulate the stoichiometry of Se/In to synthesize CuInSe2 (CISe) quantum dots (QDs) with near-infrared (NIR) emission peak tunable from 920 to 1224 nm. Meanwhile, the excitation band of these CISe QDs spans from ultraviolet to NIR regions, which is highly desired for various bioapplications. Through surface coating of thin ZnS shell, an absolute NIR-II photoluminescence quantum yield of 21.8% can be achieve, which is the highest among Pb/Cd-free QDs reported so far. By virtue of their intense NIR-II emission, we demonstrate the application of CISe nanoprobes for autofluorescence-free bioassay of CTCs (e.g., human breast cancer MCF-7 cells) spiked in whole blood samples, with the limit of detection down to 12 cell/well of a 96-well plate. Furthermore, the [email protected] nanoprobes are exploited for tumor-targeted bioimaging in live mice with a signal-to-noise ratio of 5.8. These findings reveal the great potentials of the novel NIR-II luminescent CuInSe2 nanoprobes in the field of cancer diagnosis and imaging-guided surgery.