FITC functionalized magnetic core–shell Fe3O4/Ag hybrid nanoparticle for selective determination of molecular biothiols

Abstract

A sensing strategy for chromogenic detection of molecular biothiols has been proposed based on fluorescein isothiocyanate (FITC) functionalized magnetic core–shell Fe3O4/Ag hybrid nanoparticles. Ag coated magnetic Fe3O4 nanoparticles were initially synthetized. FITC was subsequently conjugated on the surface of core–shell nanoparticles by Ag–SCN linkage and then the fluorescence of FITC was quenched. Upon addition of molecular biothiols, since the AgS bond is stronger than Ag–SCN, a place-displacement between thiols and FITC would occur and thereby the fluorescence of FITC would recover. Thus, a fluorescence “off-on” probe was attained by virtue of biothiols, so after magnetic separation, the fluorescence signal change of FITC in clear solution could be employed for quantitative determination of typical molecular biothiols such as glutathione (GSH) and cysteine (Cys). High sensitivity was obtained with the detection limits of 10nM and 20nM for GSH and Cys, respectively. As well as, the assay strategy presented excellent selectivity toward molecular biothiols against other amino acids. Furthermore, confocal imaging was achieved in living cells, indicating that this fluorescent probe is potentially applicable for imaging molecular thiols in biological systems.