Electrocatalytically Amplified Immunosensing Enabled by Titanium Oxynitride-Supported Ru Nanodots on Graphene Oxide...

Electrocatalytically amplified electrochemical immunosensing is a powerful strategy for sensitive and interference-free detection of biomarkers. Herein, we report a high-performance electrochemical immunosensor enabled by a hierarchical hybrid architecture comprising Ru nanodots anchored on titanium oxynitride nanoflakes dispersed on graphene oxide (Ru/TiON-GO), linked via APTES to biorecognition building blocks. The engineered heterostructure exhibits advanced electrocatalytic activity, arising from synergistic electronic coupling between Ru nanodots and the highly conductive TiON-GO support, effectively promoting interfacial electron transport between the electrocatalytic surface and the [Fe(CN)₆]^3-/4- redox probe. Leveraging this electrocatalytic platform, a prostate-specific antigen (PSA) impedimetric immunosensor was constructed, achieving a limit of detection of 0.06 ng mL^-1 (2.3 pM) and a wide linear response covering clinically relevant concentration range. The immunosensor demonstrates excellent selectivity in human serum, operating in interference-free mode even in the presence of common coexisting biomolecules, highlighting suitability for medical diagnostics. Density functional theory calculations further elucidate the origin of the enhanced electrocatalytic performance, with charge density difference plots and density of states analysis revealing Ru-driven electron redistribution and increased density of states near the Fermi level. This work establishes the Ru/TiON-GO nanocomposite as a robust electrocatalytic platform for advanced immunosensing applications, paving the way toward next-generation electrochemical diagnostic devices.