Graphite nanoparticle as nanoquencher for 17β-estradiol detection using shortened aptamer sequence

A graphite nanoparticle (GN) with a spherical shape and stacked by a few layered graphene sheets is an ideal fluorescent nanoquencher for the fluorophore. We developed a novel aptasensor based on fluorescence resonance energy transfer for the sensitive and specific detection of 17β-estradiol (E2) by using the GN as a fluorescent nanoquencher and the shorter E2 specific aptamer as the sensing probe. The physiological and chemical properties of the aptasensor in response to the E2 capture were investigated with an atomic force microscopic analysis and an E2 detection principle was clarified accordingly. Also, it was demonstrated that the sensitivity of the aptasensor was affected by the length of aptamer and the particle size of the nanoquencher, and the highest sensitivity for E2 detection was achieved with a shorter aptamer of 35 base sequences and a smaller GN with a particle size of around 5 nm. And the detection limit was 1.02 ng mL−1. Moreover, this presented no cross reaction with E2 analogs and was successfully utilized for the real environmental water monitoring.