A label-free and naked-eye fluorescence turn-on assay for one-pot LAMP detection of foodborne pathogens using AuNCs-Cu2+ complex

Loop-mediated isothermal amplification (LAMP) is a rapid and sensitive approach for foodborne pathogen detection; however, a simple, user-friendly, and naked-eye readable readout method remains a challenge. Herein, we synthesized bovine serum albumin stabilized gold nanoclusters (BSA-AuNCs), which exhibit fluorescence quenching upon copper ions (Cu 2+ ) binding and fluorescence recovery in the presence of phosphate ions (PPi). Leveraging this property, we developed a label-free fluorescence turn-on assay for naked-eye LAMP detection by monitoring PPi accumulation under UV light. To mitigate potential cross-contamination risks inherent in LAMP workflows, we integrated the BSA-AuNCs-Cu 2+ complex into the reaction lid, enabling a closed, one-pot detection system. This method demonstrated high sensitivity, detecting Salmonella enterica at concentrations as low as 10 1  CFU/mL within 40 min (excluding nucleic acid extraction process). With its customizable primers and naked-eye visual detection capability, this assay offers a versatile and practical tool for rapid pathogen screening in diverse applications.