Enzyme-Triggered Nanozyme In Situ Synthesis for Patulin Colorimetric/Electrochemical Dual-Mode Sensing

The sensitive detection of patulin (PAT) is of paramount important for food safety. Here, a novel colorimetric/electrochemical dual-mode sensor was constructed based on an enzyme-triggered nanozyme in situ synthesis strategy for the sensitive and reliable detection of PAT. Iron metal-organic framework (Fe-MOF) was hydrothermal synthesized on an exfoliated graphene paper (EGP) and utilized as the substrate for sensing. Due to the specific recognition between PAT and its aptamer, alkaline phosphatase (ALP) linked DNA chain was replaced. In the presence of ascorbic acid-phosphate (AAP) and K3[Fe(CN)6], Prussian blue nanoparticles (PB NPs) were in situ synthesized based on the ALP-triggered AAP hydrolysis. The produced ascorbic acid (AA) quickly reduced K3[Fe(CN)6] to K4[Fe(CN)6], which subsequently reacted with Fe-MOF on EGP to form PB NPs. The results showed that PB NPs possessed excellent peroxidase-like activity and electrochemical activity, endowing the sensor with good colorimetric and electrochemical dual-mode sensing abilities. In the presence of H2O2, PB NPs catalytically oxidized o-phenylenediamine (OPD) to form the deep yellow-color production with a distinct color change for colorimetric sensing. The electrochemical mode demonstrated high sensitivity with a lower limit of detection (LOD) of $2.6\times 10^{-{12}}$ g/mL compared to that of the colorimetric mode ( $2.2\times 10^{-{10}}$ g/mL). This portable dual-mode sensor based on ALP-triggered nanozyme in situ synthesis not only offers new insights into sensitive and reliable determination of PAT but also provides an effective way based on visual monitoring and sensitive determination to ensure food safety and health.