A split aptamer-labeled ratiometric fluorescent biosensor for specific detection of adenosine in human urine

A dual-emission ratiometric fluorometric aptasensor is presented for highly specific detection of adenosine. An adenosine binding aptamer (ABA) was split into two halves (termed as ABA1 and ABA2). ABA1 was covalently bound to blue-emitting carbon dots (with excitation/emission maxima at 365/440nm) as responsive fluorophore (referred to as ABA1-CDs). ABA2 was linked to red-emitting silica-coated CdTe quantum dots (with excitation/emission maxima at 365/613nm) acting as internal reference and referred to as ABA2-QDs@SiO2. Upon addition of graphene oxide, the fluorescence of ABA1-CDs is quenched. After subsequent addition of ABA2-QDs@SiO2 and different amounts of adenosine, the blue fluorescence is recovered and causes a color change from red to royalblue. The method represents a ratiometric turn-on assay for visual, colorimetric and fluorometric determination of adenosine. The limit of detection is as low as 2.4nM in case of ratiometric fluorometry. The method was successfully applied to the determination of adenosine in (spiked) human urine. Recoveries range from 98.8% to 102%.