AuNP-rGO-Decorated Disposable Immunosensors for Rapid and Accurate Detection of Type-Specific Antigens Causing Scrub Typhus

Abstract Gold nanoparticle-decorated reduced graphene oxides (AuNPs-rGOs) were used for the fabrication of a screen printer manufactured carbon electrode-based sensitive and portable immunosensor for the detection of scrub typhus. The AuNPs-rGOs were synthesized via a chemical reduction method and characterized via Fourier transform infrared spectroscopy, UV‒Vis spectroscopy, field emission scanning microscopy, and transmission electron microscopy. Furthermore, 56 kDa type-specific antigen (TSA) antibodies were used for immobilization over AuNPs-rGOs modified with SPCE via EDC-NHS (1:1) cross-linking chemistry. A type-specific antigen was used at different concentrations to observe the sensor response via cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy using potassium ferricyanide (K4[Fe(CN)6] 3−/4-) as a redox indicator. The developed immunosensor showed excellent sensitivity of 47.80µAcm-2ng-1 and an LOD of 0.02ngµL-1. The developed immunohybrid immunosensor is portable because of its easy mobile connectivity and fast and low cost among scrub typhus biosensors. The sensor is highly specific for TSA detection and performs well in validation with ELISA-positive blood samples and TSA-spiked blood samples.