Electrochemical “signal on/off” paper-based aptasensor for ochratoxin A detection based on MXene-Au and Pt@NiCo-LDH-catalyzed signal amplification

Electrochemical sensing technology integrated with a paper-based analytical device (PAD) offers an effective method for analyte detection. Nevertheless, it is still challenging to realize reliable and sensitive analysis owing to the basic shortcomings (inferior conductivity and high batch-to-batch variability) of paper-based working electrodes (WE) and lack of efficient signal amplification label. Herein, we proposed a novel electrochemical aptasensor to detect ochratoxin A (OTA), with MXene-Au as sensing substrates and Pt nanoparticles (NPs) anchored hollow structure NiCo-layered double hydroxides ([email protected]) as signal amplification materials. The complementary DNA (cDNA) was firstly assembled onto the MXene-Au/WE via Au-S bonds. Then aptamer (apta)-binding [email protected] with excellent peroxidase (POD)-like activity was immobilized through hybridization to trigger the “signal on” state, generating a significant electrochemical signal. The presence of OTA enabled the dissociation of the apta-cDNA hybrid, releasing signal amplification labels to achieve “signal off” state. Based on the “signal on/off” strategy, the aptasensor exhibited a wider linear range from 20 fg/mL to 100 ng/mL and a lower limit of detection of 8.9 fg/mL (S/N = 3). This work provided a new avenue for the versatile design of electrochemical paper-based platform that enabled the on-site detection of various analytes.