A gold nanoparticle-based fluorescence sensor for high sensitive and selective detection of thiols in living cells

A novel gold nanoparticle (AuNP)-based sensor for detecting thiols in aqueous solution has been developed. Due to the weak N···Au interactions, meso-(4-pyridinyl)-substituted BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) dyes were coordinated to AuNP surfaces, which effectively quenched the fluorescence of organic/inorganic hybrid systems. The fluorescent quenching mechanism was mainly ascribed to the highly efficient fluorescent resonance energy transfer (FRET) and the inner filter effect. In the presence of thiols, meso-(4-pyridinyl)-substituted BODIPY chromophore were displaced and released from the AuNP surfaces and thus restored the fluorescence of BODIPY chromophore. The modulation of the fluorescence quenching efficiency of BODIPY-AuNPs in the presence of thiols can achieve a large turn-on fluorescence enhancement (40-fold) in aqueous solution. The new AuNP-based fluorescence sensor displayed desired properties such as high specificity, relatively low detection limit (30 nM for Cys), appreciable water solubility and rapid response time (within 2 min for Cys/Hcy). Moreover, the sensor has been successfully applied for monitoring and imaging of intracellular thiols within living HeLa cells.