Assembly of adaptive engineering aptamers for Escherichia coli and their application in all-in-one rapid detection

Multivalent engineering aptamers (multi-Apts) adaptive and specific to whole Escherichia coli (E. coli: CMCC 44102) cells based on hybridization chain reaction (HCR) were constructed for the first time. The dissociation constant (K_d) value for these multi-Apts was 48 nM, demonstrating a higher affinity than that of monovalent aptamers (mono-Apts) (K_d = 102 nM). Furthermore, the reaction equilibrium of multi-Apts was achieved within 20 min, with a reaction rate twice that of mono-Apts. To validate the exceptional performance of these multi-Apts, they were employed as recognition elements in conjunction with gold nanoparticles (AuNPs) colorimetric assays for the all-in-one rapid detection of E. coli. This method exhibited a linear detection range from 1 × 10² to 1 × 10⁷ CFU mL⁻¹, achieving a limit of detection (LOD) as low as 19 CFU mL⁻¹. The recovery of this method in tap water and milk were 85.7% to 101% and 81.8% to 98.2%, respectively. The results indicated that this method not only provided a wide detection range but also exhibited high sensitivity and accuracy. Additionally, this study demonstrated that multi-Apts possessed greater application potential in the detection of macromolecular substances such as bacteria. In short, this work provided a novel approach for rapid and all-in-one detection of E. coli in food.