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Isolation of Bacteria Aptamers with Non-SELEX for the Development of a Highly Sensitive Colorimetric Assay Based on Dual Signal Amplification

Mengyue Liu,Lingjun Geng,Fengjuan Zhang,Shouyi Dou,Falan Li,Zhanli Liu,Yemin Guo,Xia Sun

In this work, an aptamer against Escherichia coli is isolated via non-SELEX, which executes efficient selection by employing repetitive cycles of centrifugation-based partitioning, and the binding site of the aptamer on E. coli cell surfaces is inferred to be a membrane protein. Moreover, truncated sequence 2–17–2 with a higher affinity (Kd = 101.76 nM) is employed for highly sensitive colorimetric detection of bacteria based on the dual signal amplification strategy. When targets exist, the release of DNA 1 from the polymer activates a hybridization chain reaction (HCR) between DNA 1 and DNA 2, thereby inducing the aggregation of probe 1. Subsequently, DNA 3 dissociated from probe 1 as a linker DNA further assembles probe 2/3. In this system, two types of DNA@gold nanoparticles (AuNPs) coexist and successively aggregate AuNPs based on divergent triggering mechanisms. Under optimal conditions, the dual signal amplification strategy presents excellent sensitivity (10 CFU mL–1) and specificity, as well as the realization of real sample analysis.