Ag₂S Quantum Dots Conjugated Chitosan Nanospheres toward Light-Triggered Nitric Oxide Release and Near-Infrared Fluorescence Imaging

Nanoscaled light-triggered nitric oxide (NO) delivery vehicles with the ability of near-infrared (NIR) fluorescence imaging was presented, which consisted of chitosan (CS)-based S-nitrosothiols (SNO) and encapsulated silver sulfide quantum dots (Ag₂S QDs). CS-SNO compounds that bore NO-storing functional groups were prepared via amino modification of chitosan. Water-soluble Ag₂S QDs were synthesized and conjugated with the CS-SNO compounds with the aid of ethylenediaminetetraacetic acid (EDTA). The biocompatible Ag₂S-CS-SNO nanospheres, with dimension of ∼117 nm, exhibited bright NIR fluorescence and satisfactory photostability under NIR irradiation. The Ag₂S-CS-SNO nanospheres could release NO under irradiation of UV or visible light at physiological pH and temperature yet would hardly release NO if NIR irradiation was applied. Cell imaging was successfully performed, demonstrating that the Ag₂S-CS-SNO nanospheres could emit readily observable NIR fluorescence and release NO in living cells. The NIR fluorescence imaging of the Ag₂S-CS-SNO nanospheres did not interfere with the light-triggered NO release from them, which would provide new perspectives for the application of multifunctional nanostructured materials in diagnostics and imaging.