Red fluorescent nanoprobe based on Ag@Au nanoparticles and graphene quantum dots for H2O2 determination and living cell imaging.

Abstract

A sensitive and turn-on fluorescence nanoprobe based on core-shell Ag@Au nanoparticles (Ag@AuNPs) as a fluorescence receptor and red emissive graphene quantum dots (GQDs) as a donor was fabricated. They were conjugated together through π-π stacking between the GQDs and single-strand DNA modified at the Ag@AuNPs surface. The absorption spectrum of the receptorsignificantly overlapped with the donor emission spectrum, leading to a strong Förster resonance energy transfer (FRET) and thus a dramatic quenching. The sensing mechanism relies on fluorescence recovery following DNA cleavage by •OH produced from Fenton-like reaction between the peroxidase-like Ag nanocore and H2O2. The red emissive feature (Ex/Em, 520nm/560nm) provides low background in physiological samples. The •OH production, great spectrum overlapping, and red emission together contributes to good sensitivity and living cell imaging capability. The fluorescence assay (intensity at 560nm) achieves a low detection limit of 0.49μM H2O2 and a wide linear range from 5 to 200μM, superior to most of the reported fluorescent probes. The RSD value for 100μM H2O2 was 1.4%. Thenanoprobe exhibits excellent anti-interferences and shows low cytotoxicity. The recovery of 100μM standard H2O2 in a cancer cell lysate was 85.8%. Most satisfactorily, it can realize monitoring and imaging H2O2 in living cells. This study not only presents a sensitive H2O2 probe but also provides a platform for detecting other types of reactive oxygen species.