In this study

a DNA biosensor was constructed for the sensitive detection of target DNA by chain reaction

with a specially designed DNA sequence as capture probe and a G-quadruplex-hemin complex as signal molecule.In the presence of target DNA

the capture DNA and the target DNA could recognize each other

while the target DNA could have a continuous chain reaction with the assistant probe

leading to the formation of a large number of G-quadruplex on the electrode surface.In the presence of hemin

the G-quadruplex combines with the hemin to form a G-quadruplex-hemin complex

which emits a strong electrochemical signal.Therefore

the detection of target DNA could be realized as the electrochemical signal obtained by differential pulse voltammetry(DPV) has a corresponding relationship with concentration of the target DNA in the system.Under the optimal conditions for the concentration of each component

the DPV current response has a good linear relationship with the target DNA concentration in the range of 0.01-10 pmol/L

and the minimum detection limit reaches to 8 fmol/L.With the advantages of high sensitivity and good specificity

the sensor has a good application prospect.