Highly sensitive turn-on fluorescent detection of captopril based on energy transfer between fluorescein isothiocyanate and gold nanoparticles

A novel approach for highly sensitive detection of captopril was developed based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (Au NPs) and fluorescein isothiocyanate (FITC), in which FITC acts as the donor and Au NPs as the acceptor. The fluorescence intensity of fluorescein isothiocyanate (FITC) was strictly quenched as a result of noncovalently adsorbed on Au NPs. Upon the addition of captopril, the fluorescence intensity of FITC “turn-on” due to the competition between captopril and FITC towards the surface of Au NPs. Under the optimum conditions, the fluorescence intensity of the released FITC displays a linear relationship in the range of 20 μg L−1 to 500 μg L−1 of captopril. Lower limit of detection for captopril, at the signal-to-noise ratio of 3 (3σ), was 2.6 μg L−1. The developed methodology was successfully applied for the determination of captopril in human plasma.