Chitosan-coated iron(III) oxide nanoparticles and tungsten disulfide quantum dots-immobilized Fiber-based WaveFlex Biosensor for Staphylococcus Aureus bacterial detection in real food samples

• Ultra-sensitive WaveFlex biosensor detects S. aureus in real food samples. • Novel SMF structure with AuNPs triggers LSPR for enhanced sensitivity. • Fe3O4–CS NPs and WS2-QDs further enhance biosensor sensitivity. • Antibody functionalization enables specific S. aureus detection. • Achieves maximum sensitivity of 2.74 nm/lg(CFU/mL) and LOD of 1.47 CFU/mL. The research proposes and investigates an extraordinarily sensitive, label-free WaveFlex biosensor utilizing optical fiber technology for the detection of Staphylococcus aureus ( S. aureus ), a common foodborne bacterium. The WaveFlex biosensor (plasmon Wave based Flexible optical fiber Biosensor) is based on a novel flexible tapered single-mode fiber structure, utilizing gold nanoparticles (AuNPs) to trigger the phenomenon of localized surface plasmon resonance (LSPR). Additionally, the sensitivity is further enhanced using chitosan-coated iron(III) oxide nanoparticles (Fe 3 O 4 –CS NPs) and tungsten disulfide quantum dots (WS 2 -QDs). The optical fiber surface is functionalized with antibodies to achieve specific detection of S. aureus . For S. aureus concentrations at 1 × 10 8 CFU/mL (colony-forming units per milliliter), the sensor's maximum sensitivity of 2.74 nm/lg (CFU/mL), and a detection limit (LOD) of 6.67 CFU/mL. This ultra-sensitive biosensor holds great potential for widespread applications in various fields, including disease detection, medical diagnostics, and food safety inspection.