Smartphone-assisted portable colorimetric detection of Salmonella based on a dual signal amplification mediated nanozyme cascade aptasensor

Salmonella is a major foodborne pathogen that poses a serious threat to global public health and economic stability. Timely and reliable detection of Salmonella is essential for the effective prevention of foodborne diseases. Herein, a novel ultrasensitive smartphone-based colorimetric aptasensor for Salmonella was reported, leveraging both the strong signal amplification capability of cascade signal amplification technology and the high efficiency of Zr@Cys-Cu dual-enzyme catalysis (with phosphatase-like and laccase-like activities). The exponential amplification (EXPAR) could be specific triggered by Salmonella to form single-stranded target DNA, which further initiated the catalytic hairpin reaction (CHA), leading to the coupling of Fe 3 O 4 and Zr@Cys-Cu. After magnetic separation, the collected Fe 3 O 4 -Zr@Cys-Cu was used for colorimetric detection, and the final colorimetric signal was processed by a smartphone. The Fe 3 O 4 -Zr@Cys-Cu aptasensor demonstrated excellent sensitivity and specificity in detecting Salmonella , with a linear range of 3 × 10°-3 × 10 5 CFU/mL and a detection limit of 3 × 10 0 CFU/mL. The entire detection process can be completed within 2 h. The system demonstrates the ability to detect analytes in complex sample matrices. Coupled with the portability of smartphones, this aptasensor emerges as a powerful tool for point-of-care testing (POCT), holding broad application potential.