Highly sensitive determination of Microcystin-LR using colorimetric and photothermal dual-mode aptasensor with europium hexacyanoferrate nanozyme

MC-LR inhibits the activity of protein phosphatase, causing liver tumors. It is vital to detect MC-LR in water samples. Herein, this work developed the colorimetric and photothermal dual-mode aptasensor of microcystin-LR (MC-LR) detection with europium hexacyanoferrate (Eu-HCF) nanozyme. The peroxidase-like (POD-like) activity of Eu-HCF was higher than that of Ca-HCF, Mn-HCF and Cu-HCF nanozymes. The POD-like activity of Eu-HCF in the presence of MC-LR aptamer decreased, indicating that the MC-LR aptamer (Apt) was adhered to the surface of the Eu-HCF nanozyme. When the MC-LR Apt specifically recognized MC-LR, which further increased this inhibition. Therefore, detection of MC-LR was achieved using this colorimetric and photothermal dual-mode aptasensor with Eu-HCF nanozyme. The colorimetric aptasensor exhibited analytical performance for MC-LR detection in the range of 1-1500 ng L -1 and a detection limit of 0.33 ng L -1 . This photothermal aptasensor showed linearity with MC-LR concentration at 1-1500 ng L -1 , achieving a detection limit of 0.27 ng L -1 . The proposed sensor had good selectivity for MC-LR detection in the presence of other microcystins and some metal ions. The proposed colorimetric and photothermal dual-mode aptasensor was successfully utilized for determination of MC-LR in tap and lake water samples with recovery rates ranged from 97.2% to 110.4%.