A fluorescence turn-on organosilane-coated Cyst/QDs nanocomposites for highly sensitive and selective monitoring silver ions in living organisms

Abstract

The practical applications of Cd-based quantum dots (QDs) in biological systems have been restricted by their high toxicity and poor biocompatibility. Herein, we constructed a new water-soluble Cyst/QDs nanocomposites composed of silicon-functionalized CdSe/CdS QDs and cystine as a turn-on fluorescent probe for the imaging and detection of Ag+ in living organisms. CdSe/CdS-Si-NH2 QDs with rich amino groups (-NH2) on their surface were firstly synthesized by reacting 3-aminopropyltrimethoxysilane with CdSe/CdS QDs capped with 2-mercaptoethanol. CdSe/CdS-Si-NH2 QDs emit the bright green fluorescence at 575 nm in aqueous solution with quantum yield of 10.6 % and superior photo-stability. Meanwhile, their fluorescence intensity can be effectively enhanced by cystine based on its strong affinity towards Cd2+ on the surface of Cd-based QDs. Besides, the addition of Ag+ results in a strongly enhanced fluorescence of as-prepared Cyst/QDs nanocomposites in aqueous solution. Under the optimal conditions, the response was linearly proportional to natural logarithm of Ag+ concentration ranging from 4.0×10−9 to 1.0×10−6 mol/L with a detection limit of 1.65 nM. Furthermore, Cyst/QDs nanocomposites can be exploited as a possible fluorescent probe for in vivo imaging based on its excellent luminescent properties, low toxicity and great biocompatibility. Bio-imaging study also revealed that Cyst/QDs nanocomposites could be applied to detecting Ag+ in live cells and organisms (zebrafish). Thus, our research provides an efficient method for creating low-toxic and biocompatible Cd-based QDs nanoprobe for a sensitive and selective detection of Ag+ in live cells and organisms.