Bacteriophage binding receptor like-peptides and MXene-AgNPs modified label-free impedimetric biosensor for detection of Staphylococcus aureus in real samples.

This is the first report of a label-free impedimetric biosensor utilizing a bacteriophage receptor-binding protein-like peptide for the selective detection of Staphylococcus aureus (S. aureus) in clinical samples. The biosensor platform was constructed by modifying screen-printed carbon electrodes with a nanocomposite composed of MXene and silver nanoparticles (AgNPs), enabling effective immobilization of the engineered peptide sequence (CKGGGGGRHYMDQTNRHYMDQTNG). The peptide was specifically designed to preserve a key binding motif (HYMD), facilitating high-affinity interaction with S. aureus surface teichoic acids. Electrochemical impedance spectroscopy (EIS) was employed to monitor bacterial attachment through changes in charge transfer resistance. The biosensor exhibited a broad linear detection range from 10 to 10⁶ CFU/mL, with a limit of detection (LOD) of 2.78 CFU/mL. Repeatability and reproducibility tests confirmed high precision with low standard deviations across replicate measurements. Chronoimpedance analysis enabled rapid detection within approximately 7.5 min and demonstrated minimal signal interference in complex matrices such as human serum and urine. This peptide-based biosensor offers a promising, cost-effective, and portable alternative to conventional diagnostic tools for S. aureus detection. The integration of MXene-AgNP nanostructures and phage-derived recognition elements may pave the way for next-generation biosensors capable of real-time pathogen monitoring in clinical and point-of-care settings.