Background signal-free and highly sensitive electrochemical aptasensor for rapid detecting tumor markers with Pb-MOF functionalized dendritic DNA probes

Abstract How to eliminate the background signal of the electrochemical aptasensor and improve its signal amplification efficiency is one of the key factors to build a highly sensitive and selective sensor. Herein, we developed a multi-signal amplified, zero background electrochemical aptasensor for rapid detection of tumor markers, with carcinoembryonic antigen (CEA) as a model analyte. A type of dendritic DNA scaffold labeled with a lead-based metal organic framework (HCR-Pb-MOF) was prepared by hybrid chain reaction as signal tags. After one-step replacement of the signal tags into the supernatant by the target, the inner Pb2+ ions in the replaced tags were detected by square-wave voltammetry (SWV) for qualification. The assay has some distinct advantages. Firstly, one HCR-Pb-MOF can load many Pb-MOFs, with each Pb-MOF containing large amounts of Pb2+; thus, multi-amplified signals from Pb2+ can be obtained after one-step replacement of the target. Secondly, Pb-MOF can also completely avoid the leakage of Pb2+, which is usually observed in the MOF probes electrostatically adsorbing metal ions, to achieve zero background. Thus, the aptasensor with a one-step replacement detection strategy can greatly improve sensitivity, with the detection limit of CEA being 0.333 pg mL−1. Finally, the stirring bar was employed after introducing the target into the system. Therefore, the whole sample detection time can be reduced to within 10 min. This aptasensor was successfully applied to rapidly and accurately analyze CEA in human serum, with results consistent to those of ELISA. All of these findings prove that this multi-signal amplified, rapid, zero background electrochemical aptasensor can meet the requirements for rapid and highly sensitive detection of tumor markers in human serum.