Programming synthetic DNA molecules for building and breaking heterostructures between TiO2 nanomaterials for photoelectrochemical bacterial detection

There is a need for rapid and field-based bacterial detection and identification platforms that do not rely on lengthy growth cultures and lab-based techniques such as mass spectroscopy and polymerase chain reaction. Electrochemical techniques have been developed for culture-free bacterial detection; however, biosensors that deliver a low enough limit-of-detection for direct water pathogen sensing remain elusive. Herein, we report a photoelectrochemical biosensor using photoactive DNAzymes for bacterial identification and photoelectrochemical signal transduction. The signal transduction is based on using DNA as a switch that makes and breaks semiconductor heterostructures between TiO2 nanomaterials for target induced-signal modulation. The developed assay, integrating molecular and photoelectrochemical switching, is able to detect Escherichia coli at a concentration of 18 CFU mL−1 and quantify it over five orders-of-magnitude in lake water without target enrichment, addition of reagents, or sample processing and can specifically identify this organism amongst five similar bacterial pathogens.