In situ formation of G-quadruplex/hemin nanowires for sensitive and label-free electrochemical sensing of acid phosphatase

Abstract

The abnormal variation of the concentration of acid phosphatase (ACP) in human body can be related to several pathophysiological diseases. Herein, a highly sensitive and non-label electrochemical biosensor for detecting ACP on the basis of target-induced inhibition of metal ion/pyrophosphate (PPi) coordination and G-quadruplex/hemin nanowires signal amplification is described. The target ACP molecules can hydrolyze PPi into phosphate to prevent the coordination between Cu2+ and PPi, and the un-coordinated Cu2+ further triggers cyclic cleavage of a G-quadruplex sequence (GS)-containing hairpin probes by the Cu2+-dependent DNAzyems on the sensor electrode to release the GS, which leads to in situ formation of the GS/hemin nanowires via the stacking of the free GS on the surface-immobilized GS with the presence of hemin. The many hemin molecules in the nanowires can thus yield dramatically enhanced current response for detecting ACP sensitively with the detection limit of 0.45 U/L. Besides, low levels of ACP present in diluted serum samples can also be selectively detected with this method. In addition to its sensitivity and selectivity, the developed method can realize substantial signal amplifications without using enzymes or nanomaterials, which can facilitate the establishment of convenient and sensitive strategies for detecting low concentrations of phosphatase for disease diagnosis.