Dual Esterase- and Steroid-responsive Energy Transfer Modulation of Ruthenium(II) and Rhenium(I) Complex-Functionalized Gold Nanoparticles

Abstract

A number of adamantane-containing ruthenium(II) and rhenium(I) complexes have been synthesized and characterized. These complexes were non-covalently functionalized with β-cyclodextrin-capped gold nanoparticles (β-CD-GNPs) through the host-guest interaction between cyclodextrin and adamantane, which were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX) and 2D ROESY 1H NMR experiments. The FRET properties of the resulted nano-conjugates could be modulated via both esterase-accelerated hydrolysis and competitive displacement of steroid, by monitoring the emission intensity and luminescence lifetime. The FRET efficiencies were found to vary with the nature of the chromophores and the length of the spacer between the transition metal complexes and the GNPs. The work has demonstrated a “proof-of-principle” assay method for the dual-functional detection of the important classes of bio-molecules, such as enzymes and steroids.