Dual-modality colorimetric and electrochemiluminescence biosensor integrated portable devices for Staphylococcus aureus detection

This study presented a dual-mode biosensor that integrates electrochemiluminescence (ECL) and colorimetric methods for detecting Staphylococcus aureus ( S. aureus ) in seafood. The biosensor utilized self-enhanced gold nanoclusters (DPEA-AuNCs) as luminescent materials, which exhibited positive potential peaks without coreactant, effectively reduced the instability. Additionally, DPEA-AuNCs exhibited enzyme-like activity, catalyzing the substrate 3′ 3′ 5′ 5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce blue reaction products for visual detection. DPEA-AuNCs were immobilized on magnetic iron tetraoxide (Fe 3 O 4 ) nanoparticles via aptamer, enabling solid-liquid separation by magnetic field. The precipitate was utilized for ECL detection, while the supernatant was employed for absorbance measurements. When S. aureus bound to the aptamer, the DPEA-AuNCs detached from Fe 3 O 4 , resulting in a poor ECL signal intensity. Meanwhile, the DPEA-AuNCs in the supernatant catalyzed the TMB substrate, resulting in color change to blue. A Microsoft mini-program was developed to analyze the correlation between RGB values and S. aureus concentration for rapid detection. The biosensor demonstrated low detection limits of 1.78 CFU/mL and 2.35 CFU/mL for ECL and colorimetric modes, respectively. This method exhibited detection sensitivity and accuracy while simplifying operations, offering an intuitive and efficient approach to food safety detection.