The effect of nutrient broth media on PEDOT:PSS gated OECTs for whole-cell bacteria detection

Abstract

The organic electrochemical transistor (OECT) is a device of much interest in biological sensing applications, including the detection of various cell types and electrolytes. In order to study cell behavior these devices are often operated in a cell culture media. While OECT operation in various salt solutions is well documented the effects of nutrient media are rarely addressed. We have investigated the effect of the complex nutrient broths commonly used in cell culturing on the OECT operation. Here we report on the effects of using lysogeny broth (LB) and yeast/triptone (YT) nutrient broths as operating media on PEDOT:PSS based planar OECTs. OECT devices were characterized in both nutrient broths and equivalent salt solutions to determine the effects that proteins and yeast extracts have on current on/off ratio, transconductance, and gate voltage at peak transconductance. We have found that the OECT peak transconductance (∼2.4 mS) was not affected by operation in broth media. However, a shift of −250 mV in effective gate voltage was observed. This resulted in a reduction in the gate voltage for peak transconductance from ∼0.7 V for a pure electrolyte solution to 0.3 V for operation in both broth solutions. A doubling in the ratio of operating current (at peak transconductance) to initial current from ∼0.2–0.3 to ∼0.5–0.6 was observed for both broth media. To demonstrate application as a biosensor in nutrient media, the OECT was used to characterize and detect the bacterium Pseudomonas fluorescens, achieving a limit of detection of ∼880 CFU/mL while operating in LB broth.