A Syringe-Based DNAzyme Sensor for Bacterial Detection

We present a simple approach for bacterial detection that uses a bead-bound RNA-cleaving DNAzyme (RcD) and a syringe. The RcD used in this study, F-EC1, is fluorescently labelled and can be specifically activated by a protein target released specifically by E. coli. Upon immobilization on agarose beads, the kinetic behaviour of F-EC1 remains similar to that in solution. The F-EC1-agarose system was able to detect as few as 1,000 CFUs of E. coli and retained high recognition specificity. A syringe-based biosensor was subsequently designed, where F-EC1-bearing agarose beads were loaded onto a filter-containing column. Upon incubation with an E. coli containing reaction mixture, the cleavage fragment released from the beads was filtered onto a nitrocellulose paper to be detected. The sensor was used to achieve the detection of E. coli in water, milk, and apple juice. This method is cost-effective, simple to use, and can be adapted to other ligand-responsive RNA-cleaving DNAzymes.