Nicking enzyme-assisted biosensor for Salmonella enteritidis detection based on fluorescence resonance energy transfer

•Convenience: The assay was performed within 2 h (including incubation time).•Environment friendly: We replaced the organic dyes with CNPs to fabricate molecule beacon.•Application: Our method has the potential for the detection of other molecules.

Salmonella enteritidis (S. enteritidis) outbreaks continue to occur, and have increased public awareness of this pathogen. Nicking endonuclease Nb.BbvC I is widely used for the detection of biomolecules and displays activity for specific double-stranded DNA (dsDNA). In this study, we developed a biosensor to detect S. enteritidis based on fluorescence resonance energy transfer (FRET) using nicking enzyme and carbon nanoparticles (CNPs). Because of the quenching effect of black hole quencher 1 (BHQ 1), the CNPs do not fluoresce in the reaction system. When the target bacteria are added, the nicking enzyme recognizes and cleaves the dsDNA fabricated by the interaction between probe and target. As a result, the CNPs dissociate from BHQ 1and emit strong fluorescence. Using the nicking enzyme, the fluorescence signals of the biosensor are greatly amplified. The biosensor exhibited a linear relationship with the concentration of S. enteritidis ranging from 102 to 3×103 CFU/mL in water and from 1.5×102 to 3×103 CFU/mL in milk. The present results indicate that our FRET-based detection system can be widely employed for the effective detection of pathogens.