Sensitive fluorescence ELISA with streptavidin scaffolded DNA tetrads for the detection of Escherichia coli O157:H7

Abstract

ABSTRACT: Escherichia coli O157:H7 poses a threat to humans. Traditional ELISA is not a sensitive method for the detection of E. coli O157:H7. Here, an efficient method was designed for improving the load capacity of alkaline phosphatase (ALP) with streptavidin scaffolded DNA tetrad (SS-DNAt). With more ALP, more ascorbic acid 2-phosphate was catalyzed to ascorbic acid that was used to synthesize fluorescence poly adenine-thymine–templated copper nanoclusters. Based on SS-DNAt, fluorescence ELISA was successfully proposed for improving the sensitivity for detection of E. coli O157:H7 in milk samples. The method showed a linear range of 104 to 106 cfu/mL. The limit of detection of fluorescence ELISA was 3.75 × 103 cfu/mL and 6.16-fold better than that of traditional ELISA. The recovery of the fluorescence ELISA was 86.7 to 93.6% with the coefficient of variation of 5.6 to 10.5% in milk. This method could be used to detect hazardous material in food.

Keywords

• enzyme-linked immunosorbent assay
• streptavidin scaffolded DNA tetrad
• copper nanoclusters
• Escherichia coli O157:H7