A fluorescence ELISA based on dsDNA-CuNCs for the detection of E. coli O157:H7 in milk

Abstract

Objective: This study aimed to developed a novel fluorescent enzyme-linked immunosorbent assay method for the sensitive detection of E. coli O157:H7 in milk samples. Methods: The pyrophosphate-Cu2+ coordination complex was hydrolyzed by alkaline phosphatase, and Cu2+ was released from copper nanoclusters as signal reporting probes. Key factors such as Cu2+ concentration, pyrophosphate concentration, and DNA template concentration and length were optimized. Results: Under the control of the optimized conditions, the method exhibited a good linear relationship (R2=0.980 8) with the target E. coli O157:H7 in the range of 5×104~1×108 CFU/mL. The limit of detection was 2.4×104 CFU/mL. Conclusion: The method was successfully applied to the determination of E. coli O157:H7 in samples of low-fat milk and skim milk. The average recovery was 92.2% ~ 108.5% with relative standard deviation 4.9% ~ 10.4%.

Keywords

• enzyme-linked immunosorbent assay
• copper nanocluster
• e. coli o157:h7
• detection