“Three-in-one” nanohybrids as synergistic nanozymes assisted with exonuclease I amplification to enhance colorimetric aptasensor for ultrasensitive detection of kanamycin

Kanamycin (KAN) residues in animal-derived food can cause serious threats to human health. Herein, a colorimetric aptasensor was described using "three-in-one" nanohybrids (hemin@Fe-MIL-88NH2/PtNP) as synergistic nanozymes assisted with the exonuclease I (Exo I) signal amplification for the ultrasensitive detection of KAN. In the presence of KAN and Exo I, the KAN aptamer (APT) was specifically bound to KAN, and the remaining APT complementary strand (cDNA1) captured hemin@Fe-MIL-88NH2/PtNP labeled with the cDNA1 complementary strand (cDNA2). Due to the synergistic effect of hemin, Fe-MIL-88NH2 and platinum nanoparticles (PtNPs), hemin@Fe-MIL-88NH2/PtNP exhibited superior catalytic performance and could efficiently catalyze the 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 system for signal development. Moreover, Exo I could digest APT and release KAN into a new cycle for signal amplification. Based on multiple signal amplification effects, our proposed aptasensor achieved a wide detection range from 0.01 to 100 ng mL-1 with a low detection limit of 2 pg mL-1. This assay also successfully detected KAN-added milk and shrimp samples with added recovery ranges of 93.58%-106.08% and relative standard deviations (RSDs) of 2.20%-5.50%. The aptasensor enabled ultrasensitive, specific, and fast detection of KAN, and exhibited promising applications in the efficient detection of food pollutants.