A novel PCR-free and label-free cloth-based DNA sensor for sensitive and rapid detection of Escherichia coli

Background: As is known to all, pathogenic bacteria have a serious impact on human health. The development of sensitive, simple, rapid and low-cost bacterial detection method is necessary. Nowadays, some conventional methods (such as plate count, polymerase chain reaction (PCR) and immunological techniques) can not meet the above needs. This work was aimed at providing a new method for addressing these unmet needs.Result: This study proposed a novel PCR-free and label-free DNA sensor based on multiple linear hybridization chain reaction (ML-HCR) and cloth-based closed bipolar electrochemiluminescence for sensitive and rapid detection of Escherichia coli (E. coli). The target DNA can be obtained from the E. coli genomic DNA by using the restriction enzyme instead of PCR. The auxiliary probe-triggered ML-HCR is carried out with continuous hy-bridization of two hairpin DNA, and as a result the double stranded DNA is formed to provide a large number of binding sites for Ru(bpy)32+. The whole detection is PCR-free and label-free, and thus the detection procedure is easier and faster. Under optimized conditions, the linear detection range was from 102 to 107 CFU/mL, and the detection limit was low to 38 CFU/mL. In addition, the proposed DNA sensor has an acceptable selectivity, stability and reproducibility, and is successfully applied to detect E. coli in milk samples with the recoveries from 96.24% to 105.98%.Significance: The proposed DNA sensor has broad application prospects in the fields of bacterial detection and gene diagnose. Further, this method has potential to be extended for establishing miniaturized, integrated, and automated detection system.

Automated summary

A novel PCR-free and label-free DNA sensor based on multiple linear hybridization chain reaction (ML-HCR) and cloth-based closed bipolar electrochemiluminescence was proposed for sensitive and rapid detection of Escherichia coli (E. coli). The sensor showed a linear detection range from 102 to 107 CFU/mL with a low detection limit of 38 CFU/mL. It also demonstrated acceptable selectivity, stability, and reproducibility, and was successfully applied to detect E. coli in milk samples with high recoveries.