Rapid and Ultrasensitive Detection of Staphylococcus aureus Using a Gold-Interdigitated Single-Wave-Shaped Electrode (Au-ISWE) Electrochemical Biosensor

Staphylococcus aureus ( S. aureus ), a bacterium that causes staphylococcal food poisoning, is a Gram-positive human pathogen commonly found in the environment, as well as in the nose and on the skin of humans. Conventional detection methods for this bacterium involve bacterial counting and polymerase chain reaction (PCR), which are constrained by slow processing times and expensive equipment. This study reveals a promising functionalization of gold-interdigitated single-wave-shaped electrodes (Au-ISWE) with a self-assembled monolayer (SAM) to detect S. aureus with enhanced selectivity, label-free detection, cost-effectiveness, and rapid response. The Au-ISWE bioactive surface consisting of a Cr/Au-featured SiO 2 substrate was fabricated using a SAM of 6-mercaptohexanoic acid (MHA) to form 6-MHA/EDC-NHS/anti- S. aureus antibodies. The anti- S. aureus antibodies were immobilized on the surface of the ISWE using layer-by-layer interface self-assembly chemistry. Under optimal conditions, this sensing platform was electrochemically characterized, and its limit of detection (LOD) was measured using electrochemical impedance spectroscopy (EIS). The results of this analytical study demonstrate that this platform provides the desired electromechanical microelectrodes for anti- S. aureus antibody immobilization, which exhibits amplified impedance, enabling a wide detection range (10 to 10 6 CFU mL −1 ), a low LOD (10 CFU mL −1 ) within 30 min of response time, good linearity, and high sensitivity. Remarkably, the developed sensor showed a selectivity against different bacteria including B. cereus (Gram-positive bacteria) and E. coli (Gram-negative bacteria). Additionally, it exhibited a stable performance for 21 days at 4 °C, as confirmed by a stability test (approximately 97.3% of its activity retained). Finally, the results obtained using this sensing platform outperformed compared with those obtained using the standard PCR method.