Thermal reduction synthesis approach of reduced graphene oxide for the preparation of a label-free and prompt immuno sensing of Salmonella enterica via electrochemical techniques

This work comprises an immunosensor fabrication decorated with reduced graphene oxide (rGO) onto Indium tin oxide (ITO) coated electrodes to detect Salmonella enterica antigen. The rGO was synthesized with a modified Hummer technique and characterized via UV, XRD, FTIR, RAMAN and SEM techniques. The synthesized rGO was optimized at different concentrations to develop an immunosensor. An EDC-NHS interaction immobilized the monoclonal antibody against the selected antigen. Electrochemical techniques such as electrochemical impedance spectroscopy and cyclic voltammetry were deployed to characterize the modified electrodes in 5 mM Zobell's solution, followed by a differential pulse voltammetry analysis for sensor validation. The fabricated sensor has a 44 CFU/mL detection limit (LoD) and a 135 CFU/mL quantification limit (LoQ) with a linear range of 10 1 –10 7 CFU/mL. This proposed immunosensor can be applied to any sample containing traces of Salmonella enterica. • Development of a Highly Sensitive Immunosensor: A low detection limit of 44 CFU/mL, significantly surpassing traditional culture-based methods . • Optimization of Electrode Fabrication : The optimal concentration of rGO (1 mg/mL) and anti-Salmonella antibody dilution (1:100) were identified, along with an incubation time of 30 min for effective antigen-antibody interaction, ensuring maximum sensor performance . • Excellent Specificity and Selectivity : The fabricated immunosensor exhibited high specificity towards Salmonella enterica with negligible interference against E . coli and B . brevis . • Rapid and Efficient Detection : Qualitative detection of Salmonella enterica within 40 mins, significantly reducing the time required compared to conventional techniques, which take several days . • Validation through Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) : The stepwise immunosensor fabrication were successfully verified using CV and EIS, confirming the efficacy of the biosensor.