Flow-Cell Sensor for Bacteria Detection Using Gate-Modified Organic Electrochemical Transistor

Organic electrochemical transistors (OECT) have been previously demonstrated in the sensing of cells and metabolic products. In this study, we report a novel approach on the universal detection of bacterial contamination in home-liquid-goods through the utilization of a microfluidic flow-cell that has been integrated with OECT technology. The flow-cell device has been developed for the purpose of detecting minimal concentration (~10³ CFU/ml) of several bacterium types (<i>Escherichia coli</i>, <i>Pseudomonas fluorescens and Staphylococcus aureus</i>) in various commercial household liquid product blends (cf. Air Febreze, Tide, Old Spice bodywash). This process can be completed in a testing period of one hour or less and does not require amplification or a designated binding agent. The flow-cell configuration uses a microporous filter membrane (Au coated PETE, 0.2 µm pore diameter) designed to concentrate the bacteria within the chamber. The membrane also functions as a gate electrode for the operation of OECT. The presence of bacteria on the gate filter membrane leads to an increase in the total effective gate voltage (<i>V_eff</i>), which in turn causes a decrease in the OECT source-drain channel current (<i>I_DS</i>). Based on the shift of <i>I_DS</i>, the OECT provides good discrimination between bacteria and sterile solutions (0.4 mA difference). The OECT transconductance (<i>g_m</i>) exhibits a maximum value at different levels of <i>V_GS</i> for sterile and bacteria solutions. g_m shifts to positive value at lower gate operating voltage due to bacteria attachment on Au gate. The flow-cell filtration and OECT gate sensing approach has the capability to identify a diverse range of bacteria, encompassing both gram-positive and gram-negative strains, across multiple testing media.This approach exhibits potential for biosensing systems that will enable real-time monitoring at the production line.