A highly sensitive electrochemical aptasensor for vascular endothelial growth factor detection based on toehold-mediated strand displacement reaction.

An electrochemical aptasensor with high sensitivity, specificity, and good intra-day reproducibility is reported to meet the detection needs of vascular endothelial growth factor (VEGF). The toehold-mediated strand displacement recycling amplification and VEGF aptamer are integrated in the biosensor. The probe A is hybridized with the VEGF aptamer to form the probe A-aptamer complex. When VEGF is introduced, the aptamer specifically binds with VEGF, and probe A can be liberated. Then, the free probe A captures the toehold region of the Hp1, leading the exposure of the toehold region on the other end of Hp1. Similarly, Hp2 and Hp3 are also immobilized on the surface of the electrode; thus, the methylene blue labelled on Hp2 and Hp3 causes the current response. With the signal transduction mechanism, the expression level of VEGF can be detected quantitatively. With a series of optimizations of sensor parameters, high sensitivity and specificity of the VEGF detection sensor can be achieved with a detection limit as low as 10 pg mL. This significant performance has good intra-day reproducibility, and it can be applied to human biological samples such as serum, urine, and saliva to detect the VEGF content.