Electrochemical cell respiration strategy by Cu(II)-chitosan functionalized carbon paper for rapid and sensitive detection of staphylococcus aureus

This study presents an innovative electrochemical biosensor for the rapid and sensitive detection of Staphylococcus aureus ( S. aureus ), a significant foodborne pathogen. The biosensor is based on carbon paper modified with a Cu(Ⅱ)-crosslinked chitosan hydrogel film. Unlike conventional methods that rely on biomolecular recognition, this paper sensor detects S. aureus by measuring its unique respiration cycle, specifically its ability to reduce ferricyanide to ferrocyanide in the presence of mannitol. The chitosan hydrogel enhances the surface concentration of ferrocyanide and exhibits anti-fouling properties, while Cu(Ⅱ) crosslinking improves conductivity and diffusion. The biosensor demonstrates high sensitivity (0.082 μA/μM in I-t tests and 5.31 μA/μM in DPV tests) and low limits of detection (3.47   μM in I-t tests and 0.64   μM in DPV tests). It achieves a detection linear range of 10 0 to 10 5 CFU/mL with an LOD of 3.4 CFU/mL as well as excellent repeatability (RSD of 4.2%) and stability (retaining 83.4% of its initial signal after 15 days). Its performance in real food and wound samples confirms its high sensitivity and reasonable recovery rates, even in complex matrices. This research provides a strong foundation for the application of electrochemical biosensors in food safety monitoring and pathogen detection.