A portable, battery-powered photoelectrochemical aptasesor for field environment monitoring of E. coli O157:H7

Escherichia coli O157:H7 (E. coli O157:H7) is typically associated with food- and water-borne outbreaks, thus making continuous monitoring essential. Photoelectrochemical (PEC) detection, which harvests the unique photo-to-electric property of photoactive species, has emerged as an exciting tool for bioanalysis. However, the current attempts are mostly carried out in lab, and less explored in field. Here, a simple PEC aptasensor for E. coli O157:H7 was designed and optimized (LOD: 200 cfu/mL). To promote its field application, a portable PEC analyzer was further constructed with a miniaturized LED (3 V, 3 W) for excitation and a USB-type electrochemical workstation for detection. Meanwhile, a re-chargeable power bank (5 V, 20,000 mAh, originally used for cell phone charging) was explored to power the LED through a self-designed electrical circuit. In this manner, the PEC analyzer could work continuously for more than 12 h. To facilitate transportation or the portable PEC analyzer, all components were mounted into a suitcase (size: 42 × 34 × 17 cm3; wight: ∼3.5 kg). To validate the applicability of the portable PEC analyzer, on-site detection of E. coli O157:H7 in an in-land river was carried out (> 8 h), demonstrating the bright potential of the portable PEC analyzer for field environmental monitoring.