# A Portable Extended-Gate FET Integrated Sensing System with Low-Noise Current Readout for On-Site Detection of Escherichia coli O157:H7

## TL;DR

A portable FET-based system was developed for on-site detection of Escherichia coli O157:H7 with low-noise readout and real-time data streaming.

## Contribution

A portable, integrated EG-FET system with low-noise current readout for on-site detection of E. coli O157:H7 is presented.

## Key findings

- The system achieved linear calibration over 10⁴–10¹⁰ CFU/mL of E. coli O157:H7.
- The sensor showed 13% maximum interference from other foodborne pathogens.
- The system enables stable biasing and low-noise readout without benchtop instrumentation.

## Abstract

Field-effect transistor (FET) biosensors enable label-free and real-time electrical transduction; however, their practical deployment is often constrained by the need for bulky benchtop instrumentation to provide stable biasing, low-noise readout, and data processing. Here, we report a portable extended-gate FET (EG-FET) integrated sensing system that consolidates the sensing interface, analog front-end conditioning, embedded acquisition/control, and user-side visualization into an end-to-end prototype suitable for on-site operation. The system couples a screen-printed Au extended-gate electrode to a MOSFET and employs a low-noise signal-conditioning chain with microcontroller-based digitization and real-time data streaming to a host graphical interface. As a proof-of-concept, enterohemorrhagic Escherichia coli O157:H7 was selected as the target. A bacteria-specific immunosensing interface was constructed on the Au extended gate via covalent immobilization of monoclonal antibodies. Measurements in buffered samples produced concentration-dependent current responses, and a linear calibration was experimentally validated over 104–1010 CFU/mL. In specificity evaluation against three common foodborne pathogens (Staphylococcus aureus, Salmonella typhimurium, and Listeria monocytogenes), the sensor showed a maximum interference response of only 13% relative to the target signal (ΔI/ΔImax) with statistical significance (p < 0.001). Our work establishes a practical hardware–software architecture that mitigates reliance on benchtop instruments and provides a scalable route toward portable EG-FET sensing for rapid, point-of-need detection of foodborne pathogens and other biomarkers.