Aqueous synthesis of Ag and Mn co-doped In2S3/ZnS quantum dots with tunable emission for dual-modal targeted imaging.

ABSTRACT

Here, we present the microwave-assisted synthesis of In2S3/ZnS core/shell quantum dots (QDs) co-doped with Ag+ and Mn2+ (referred to as AgMnIn2S3/ZnS). Ag+ altered the optical properties of the host QDs, whereas the spin magnetic moment (S=5/2) of Mn2+ efficiently induced the longitudinal relaxation of water protons. To the best of our knowledge, this is the first report of the aqueous synthesis of color-tunable AgMnIn2S3/ZnS core/shell QDs with magnetic properties. The synthetic procedure is rapid, facile, reproducible, and scalable. The obtained QDs offered a satisfactory quantum yield (45%), high longitudinal relaxivity (6.84s-1mM-1), and robust photostability. In addition, they exhibited excellent stability over a wide pH range (5-12) and high ionic strength (0.15-2.0M NaCl). As seen by confocal microscopy and magnetic resonance imaging, AgMnIn2S3/ZnS conjugated to hyaluronic acid (referred to as AgMnIn2S3/ZnS@HA) efficiently and specifically targeted cluster determinant 44, a receptor overexpressed on cancer cells. Moreover, AgMnIn2S3/ZnS@HA showed negligible cytotoxicity in vitro and in vivo, rendering it a promising diagnostic probe for dual-modal imaging in clinical applications. STATEMENT OF SIGNIFICANCE: In this manuscript, we reported a facial and rapid method to prepare In2S3/ZnS core/shell quantum dots (QDs) co-doped with Ag+ and Mn2+ (referred to as AgMnIn2S3/ZnS). Ag+ dopants were used to alter the optical properties of the In2S3 host, whereas Mn2+ co-dopants with their unpaired electrons provided paramagnetic properties. The emission wavelength of the core/shell QDs could be tuned from 550 to 743nm with a maximum PL quantum yield of 45%. The resulting core/shell QDs also maintained a stable emission in aqueous solution at broad ranges of pH (5-12) and ionic strength (0.15-2.0M NaCl), as well as a high photostability under continuous irradiation. In vivo cytotoxicity experiments showed that up to 500µg/mL AgMnIn2S3/ZnS@HA did not cause obvious toxicity to zebrafish embryos. In vitro targeted cell luminescence and magnetic resonance imaging showed that AgMnIn2S3/ZnS conjugated to hyaluronic acid was selectively and efficiently internalized in CD44-expressing tumor cells, confirming that the resultant QDs could function as dual-modal imaging probes for accurate diagnosis.