A dual-readout aptasensor integrating FRET and nanozyme-like catalytic activity for detection of Vibrio parahaemolyticus

Vibrio parahaemolyticus , a major foodborne pathogen associated with seafood contamination, poses serious threats to public health, highlighting the need for development of rapid, sensitive, and reliable detection methods. In this study, a dual-mode fluorometric and colorimetric biosensing platform was developed based on carbon quantum dots (CQDs) integrated with an rGO–NH₂/Fe₃O₄/AuNPs nanocomposite for the sensitive detection of V. parahaemolyticus . The proposed sensing mechanism relies on fluorescence resonance energy transfer (FRET) and catalytic signal amplification. In the absence of the target, fluorescence of CQDs is quenched due to FRET interactions with the nanocomposite platform. Upon the introduction of V. parahaemolyticus , the specific interaction induces the release of fluorescent aptamer/CQDs from the nanocomposite surface, resulting in significant fluorescence recovery. Simultaneously, the presence of the target enhances the catalytic activity of AuNPs toward the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), producing a distinct colorimetric response. The fluorescence intensity exhibited a strong linear relationship with bacterial concentration and a low limit of detection (LOD) of 3.5 CFU/mL, indicating excellent sensitivity and reproducibility. The colorimetric mode also demonstrated good linearity with an LOD of 6 CFU/mL, enabling rapid and visual detection. The dual-mode system combines the high sensitivity of fluorescence detection with the simplicity and practicality of colorimetric analysis. Overall, this strategy provides a robust, sensitive, and versatile platform for the detection of V. parahaemolyticus , with promising applications in food safety monitoring and environmental analysis.