Amino acid functionalized ZrO₂ nanoparticles decorated reduced graphene oxide based immunosensor

Here, a study is reported on a simple, one-step method for the synthesis of a zirconium dioxide-reduced graphene oxide (ZrO₂-RGO) nanocomposite involving the reduction of graphene oxide (GO) and in situ growth of ZrO₂ NPs using hydrazine as a reducer. This ZrO₂-RGO nanocomposite was functionalized with l-methionine (Meth) for immunosensor application. Morphological and structural studies clearly indicated that ZrO₂ NPs (6 nm) were decorated onto the RGO sheets, and enhanced exfoliation, thereby preventing the restacking of the RGO sheets. RGO improved the electrochemical properties of the ZrO₂-RGO nanocomposite and minimized the aggregation of ZrO₂ NPs. FTIR studies confirmed the functionalization of the ZrO₂-RGO nanocomposite with Meth and biomolecules (anti-OTA and BSA). The Meth functionalized ZrO₂-RGO nanocomposite had enhanced biocompatibility and wettability as confirmed by MTT assay and contact angle studies, respectively. Furthermore, a uniform thin film of the Meth/ZrO₂-RGO nanocomposite was electrophoretically deposited onto an indium tin oxide (ITO) coated glass substrate and utilized for covalent immobilization of monoclonal antibodies specific to ochratoxin A (anti-OTA) for the detection of ochratoxin A (OTA). The fabricated BSA/anti-OTA/Meth/ZrO₂-RGO/ITO immunoelectrode exhibited a wide linear detection range of 1-20 ng mL^-1 with a sensitivity of 4.8 μA ng^-1 mL cm^-2 and a detection limit of 0.079 ng mL^-1 for OTA detection.