A novel strategy for detection of small molecules based on aptamer/gold nanoparticles/graphitic carbon nitride nanosheets as fluorescent biosensor.

Herein, a novel ultrasensitive strategy has been developed by designing a label free fluorescent nano-aptasensor for monitoring of small moecules in human plasma. In this nano-aptasensor, graphitic carbon nitride nanosheets were used as fluorescent probe. The fluorescence intensity of the probe was decreased by interaction between graphitic carbon nitride nanosheets and label-free aptamer/gold nanoparticles conjugate, via Fluorescence resonance energy transfer mechanism. Upon addition of the analyte, the fluorescence of graphitic carbon nitride nanosheets was restored due to the aptamer/analyte interaction, and the aggregation of gold nanoparticles in the presence of salt. The influence of various factors on sensing method was investigated, and under the approved conditions, the fluorescence signal showed a linear relation with Digoxin concentration in the range of 10-500 ng L-1 with limit of detection down to 3.2 ng L-1 relative standard deviations for 25, 100 and 500 ng L-1 of analyte concentrations were 2.6, 4.0 and 6.5%, respectively. This strategy provided a simple, rapid, cost effective and reproducible experimental model, with successful application for determination of Digoxin in plasma samples without any pretreatment steps.