A novel aptasensor strategy for protein detection based on G-quadruplex and exonuclease Ⅲ-aided recycling amplification

The detection of biomarkers is of great significance in the diagnosis of numerous diseases,especially cancer.Herein,we developed a sensitive and universal fluorescent aptasensor strategy based on magnetic beads,DNA G-quadruplex,and exonuclease III(Exo III).In the presence of a target protein,a label-free single strand DNA(ssDNA) hybridized with the aptamer was released as a trigger DNA due to specific recognition between the aptamer and target.Subsequently,ssDNA initiates the Exo Ⅲ-aided recycling to amplify the fluorescence signal,which was caused by N-methylmesoporphyrin IX(NMM)insertion into the G-quadruplex structure.This proposed strategy combines the excellent specificity between the aptamer and target,high sensitivity of the fluorescence signal by G-quadruplex and Exo Ⅲ-aided recycling amplification.We selected(50-1200 nmol/L) MUC1,a common tumor biomarker,as the proof-of-concept target to test the specificity of our aptasenso r.Results reveal that the sensor sensitively and selectively detected the target protein with limits of detection(LODs) of 3.68 and 12.83 nmol/L in buffer solution and 10% serum system,respectively.The strategy can be easily applied to other targets by simply substituting corresponding aptamers and has great potential in the diagnosis and monitoring of several diseases.