Electropolymerised molecularly imprinted polymers for the heat-transfer based detection of microorganisms: A proof-of-concept study using yeast

In this contribution, molecularly imprinted polymers (MIPs) were electropolymerised onto screen-printed carbon electrodes (SPCEs) to develop specific sensors for thermal detection of yeast. A laboratory yeast strain free of interferents was used to optimise the polymerisation procedure, whereas yeast in a complex mixture (yeast for baking) was employed to produce the final sensors and demonstrate proof-of-application. Two different electropolymerisation methods were employed, cyclic voltammetry and chronoamperometry respectively; the electrochemical methodology allows for controlled deposition and the ability to tailor the polymer surface to the required application. Infrared spectroscopy and scanning electron microscopy confirmed that the methods led to different structures; with cyclic voltammetry a high surface area was achieved, whereas for chronoamperometry a dense film was formed. Subsequently, these functionalised electrodes were inserted into a home-made thermal device that can measure the selective binding of yeast cells to the MIP layer via monitoring the thermal resistance (R ) at the solid–liquid interface. The results of the measurements showed that MIP-functionalised electrodes produced, according to both methods, a significant response in thermal signal for the MIP-functionalised electrode, which was not the case for the reference Non-Imprinted Polymer (NIP)-functionalised electrode. This demonstrated that thermal analysis can be employed for the detection of yeast, even in a complex sample such as food. To our knowledge, this is the first report of MIPs electropolymerised onto screen-printed electrodes for the thermal detection of fungi. The proposed approach enables the fast production of low-cost electrodes using a simple manufacturing procedure compatible with a portable device, implying high commercial potential. In the future, this could be adapted to a broad range of microorganisms including bacteria. t