Visible light-triggered nitric oxide release from near-infrared fluorescent nanospheric vehicles.

Bifunctional Ag₂S QDs@CS-RBS nanospheres with ultralow toxicity for biomedical use were fabricated. These are capable of releasing NO under irradiation of visible light and emitting in near-infrared (NIR) region fluorescence excited by NIR laser under physiological environment. Glutathiose (GSH)-capped Ag₂S QDs were synthesized and encapsulated by chitosan (CS) to form NIR fluorescent Ag₂S QDs@CS nanospheres. A type of iron/sulfur/-nitrosyl cluster, Roussin's black salt anion Fe₄S₃(NO)₇⁻ (RBS) was conjugated with the Ag₂S QDs@CS to obtain Ag₂S QDs@CS-RBS nanospheres. A variety of characterization methods were employed to analyze the nanospheres. In vitro cell imaging and in vivo mice imaging experiments demonstrated that the Ag₂S QDs@CS-RBS nanospheres could emit readily observable NIR fluorescence and deliver NO in living cells and small animals. The NIR imaging of the Ag₂S QDs@CS nanospheres would not interfere with the light-triggered NO release from them, as the excitation lasers needed for these two functions are in different wavelength regions. This work provides new perspectives for the application of multifunctional nano-structured materials in diagnostics and bioimaging. [ABSTRACT FROM AUTHOR]