An Organic Electrochemical Transistor to Monitor Salmonella Growth in Real‐Time

Abstract

Organic electrochemical transistors (OECTs) are used in research and diagnostic applications due to their facile manufacture, scalability, and biocompatibility. In these devices, the source–drain current upon gate voltage application depends on ion concentration in the electrolyte. This study investigates whether an OECT can be employed to monitor bacterial growth since it is known that the concentration of charged species increases in bacterial cultures during growth. A poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate‐based single‐well OECT, compatible with long‐term incubation of bacterial cultures, is fabricated. It is shown that the growth of Salmonella alters the transfer characteristics of the device and demonstrates how it can be applied to monitor growth in real‐time by recording the source–drain current at gate voltage +0.5 V. The signal can also be measured in filtrates of bacterial cultures, devoid of bacterial cells. This suggests that the signal originates from charged metabolic products. Bacterial biofilm formation does not alter the device response. This proof‐of‐principle study presents OECT recordings as an alternative to optical methods, allowing bacterial growth to be monitored in transparent and opaque media alike. By measuring metabolic products rather than bacterial cell multiplication, insight into the stationary phase and other nondividing states may be obtained in the future.

Pulse electrochemical synaptic transistor for supersensitive and ultrafast biosensors

“…The real‐time transient current flowing in the source‐drain loop ( i DS ) responding to pH variations is recorded in Figure 3F. Under the premise of no water splitting, a higher | V D | is beneficial for enhancing the | I DS |, and the V G ( g m *) is commonly used as the operating point to get the best signal amplification 13–15 . Based on such a guideline, the as‐prepared ECT‐based pH sensors are expected to be most sensitive to H + concentration when V D and V G are set at −0.6 and 0.30 V, respectively (Figure 3C).…”

“…Under the premise of no water splitting, a higher jV D j is beneficial for enhancing the jI DS j, and the V G (g m *) is commonly used as the operating point to get the best signal amplification. [13][14][15] Based on such a guideline, the asprepared ECT-based pH sensors are expected to be most sensitive to H + concentration when V D and V G are set at À0.6 and 0.30 V, respectively (Figure 3C). However, our experimental result shows that the most sensitive response occurs at V G = 0 V (i.e., V G,i , where the transconductance curves intersect each other), which is different from the conventional fait accompli selection criteria of the working point.…”

“…In practical applications, ECT‐based pH sensors usually operate in the potentiostatic mode. Setting V G at V G ( g m *) is commonly accepted as an optimal scheme because it can fully utilize ECTs' signal amplification capabilities and improve the as‐prepared sensors' sensitivity 13–15 . However, as the analyte concentration varies, the V G ( g m *) disperses in a wide range instead of a fixed value 16,17 .…”

“…Setting V G at V G (g m *) is commonly accepted as an optimal scheme because it can fully utilize ECTs' signal amplification capabilities and improve the as-prepared sensors' sensitivity. [13][14][15] However, as the analyte concentration varies, the V G (g m *) disperses in a wide range instead of a fixed value. 16,17 The g m * shifts accordingly with the variation of analyte concentrations.…”

Fluorescent optotracers for bacterial and biofilm detection and diagnostics

“…An electrochemical sensor based on the conductive polymer PEDOT:PSS has been developed in order to enable direct detection of bacterially secreted redox-active compounds [ 58 ]. Further development of a transistor-based design with a PEDOT:PSS channel generated a possibility to achieve bacterial sensing during growth in real-time, as redox active species were produced by bacteria [ 59 ].…”