Amino acid functionalized ZrO2 nanoparticles decorated reduced graphene oxide based immunosensor

Abstract

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.