Polymeric-coated Fe-doped ceria/gold hybrid nanocomposite as an aptasensor for the catalytic enhanced colorimetric detection of 2,4-dinitrophenol

The Meisenheimer charge transfer reaction has, for many years, been the predominant mode of interaction to detect explosive compounds via the naked eye. However, this method is majorly sensitive to 2,4,6-trinitrotoluene and insensitive to many other explosive compounds. In this work, we report on the development of a novel aptamer-based amphiphilic polymer-coated Fe-doped ceria/gold (Au) hybrid nanocomposite (NC) as a peroxidase mimetic nanozyme for explosive colorimetric detection. Polymeric-Fe-doped ceria NC was synthesized and incorporated in-situ in the hydrothermal synthetic pot of citrate-Au nanoparticles to form a polymer-Fe-doped ceria/Au NC. A streptavidin (strep)-biotinylated DNA aptamer (B-Apt) binding complex was immobilised on the polymer-Fe-doped ceria/Au NC surface and the modified NC was used as a functional nanozyme in a peroxidase mimic assay to catalyse the oxidation of 3,3′,5,5′-tetramethylbenzidine by H2O2. Screening of several explosives showed that 2,4-dinitrophenol (DNP) bonded with higher affinity to the aptamer based on the selective greenish colorimetric catalytic reaction observed. The peroxidase mimetic activities of several nanozymes were tested and our analysis showed that the polymer-Fe-doped ceria/Au NC generated enhanced catalytic activity for DNP detection. Several optimisation reactions including the kinetic reaction mechanism was conducted and a limit of detection of 0.45 µg/mL (2.4 µM) was obtained for DNP recognition. The peroxidase mimetic strep-B-Apt-polymer-Fe-doped ceria/Au NC biosensor was successfully applied for the detection of DNP in tap water and river water with satisfactory recoveries in the range of 97–117%.