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Salmonella can cause serious foodborne diseases, which is a major concern for global public health. The sensitive and fast analysis of Salmonella is of importance for food safety. Herein, we developed a fluorescence sensing array based on photonic crystals (PCs) and recombinase-aided amplification (RAA) for high-throughput and high-sensitive analysis of Salmonella in foods. In this assay, RAA was employed for powerful amplification of the target DNA of Salmonella , and the generated dsDNA amplicon was embedded with nucleic acid dye SYBR Green I (SGI), emitting fluorescence. Furthermore, the fluorescence signal was physically enhanced by PCs array; meanwhile, the high-throughput and sensitive detection was realized by microplate reader. Because of the isothermal reaction and lyophilized regent of RAA, the proposed array possessed gentle operation and stable amplification performance. Besides, a small volume of loading samples with 2 μL was required on the PCs array for powerful fluorescence enhancement. Due to the synergistic signal amplification effect of RAA and photonic crystals, a low limit of detection (LOD) of 10 CFU/mL was achieved. Besides, the proposed array exhibited excellent performance with 100% accuracy in 20 spiked food samples. Therefore, the proposed method with the advantages of sensitivity and high throughput showed great application potential. • A fluorescent biosensor based on RAA and PCs was engineered for sensitive detection of Salmonella. • RAA with SYBR Green I has rapid, isothermal and cheap features without need of complex instruments. • PC array was employed to achieve rapid, simultaneous and high-throughput detection. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 isolation from cold-chain food products confirms the possibility of outbreaks through cold-chain food products. RNA extraction combined with RT-PCR is the primary method currently utilized for the detection of SARS-CoV-2. However, the requirement of hours of analytical time and the high price of RT-PCR hinder its worldwide implementation in food supervision. Here, we report a fluorescence biosensor for detection of SARS-CoV-2 N protein. The fluorescence biosensor was fabricated by aptamer-based conformational entropy-driven circuit where molecular beacon strands were labeled with graphitic carbon nitrides quantum dots@Zn-metal-organic framework (g-CNQDs@Zn-MOF) and Dabcyl. The detection of the N protein was achieved via swabbing followed by competitive assay using a fixed amount of N-48 aptamers in the analytical system. A fluorescence emission spectrum was employed for the detection. The detection limit of our fluorescence biosensor was 1.0 pg/mL for SARS-CoV-2 N protein, indicating very excellent sensitivity. The fluorescence biosensor did not exhibit significant cross-reactivity with other N proteins. Finally, the biosensor was successfully applied for the detection of SARS-CoV-2 N protein in actual cold-chain food products showing same excellent accuracy as RT-PCR method. Thus, our fluorescence biosensor is a promising analytical tool for rapid and sensitive detection of SARS-CoV-2 N protein. • An aptamer-based sensor could detect of SARS-CoV-2 in food products within 30 min. • Conformational entropy-driven circuit was designed for signal amplification. • g-CNQDs@Zn-MOF was utilized to improve stability and reproducibility of biosensor. • This strategy unlocks a route for the development of sensitive analytical tools. [ABSTRACT FROM AUTHOR]