Lactate Detection in Tumor Cell Cultures Using Organic Transistor Circuits

A reference-based sensor circuit was developed by integrating two differently functionalized organic electrochemical transistor (OECTs), comprised of the well-known organic p-type semiconductor poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS), into a Wheatstone bridge layout. A calibration curve of lactate in buffer is derived from the chronopotentiometric response of the Wheatstone bridge sensor after successive additions of increasing concentrations into the wells of both OECTs. To demonstrate the sensitivity of our device, we performed a titration curve assessing the response of the device to an accumulation of lactate in cell media, collected after incubation with increasing numbers of peripheral blood mononuclear cells (PBMC) for 24 h. The OECT has proven to provide highly sensitive metabolite detection due to its high current modulation in response to a change in the gate bias while the Wheatstone bridge sensor circuit provides an inherent background subtraction, thus ensuring elimination of any interference arising from other factors. As a proof-of-concept, the lactate produced from cultures of healthy PBMC and malignant non-Hodgkin’s lymphomas was compared. An elevated lactate production was indeed monitored in the cancer cells, confirming their intrinsic enhanced glycolytic metabolic activity, even in unstimulated conditions.