Imprinted Polydimethylsiloxane-Graphene Oxide Composite Receptor for the Biomimetic Thermal Sensing of Escherichia coli

This work presents an imprinted polymer-based thermal biomimetic sensor for the detection of Escherichia coli. A novel and facile bacteria imprinting protocol for polydimethylsiloxane (PDMS) films was investigated, and these receptor layers were functionalized with graphene oxide (GO) in order to improve the overall sensitivity of the sensor. Upon the recognition and binding of the target to the densely imprinted polymers, a concentration-dependent measurable change in temperature was observed. The limit of detection attained for the sensor employing PDMS-GO imprints was 80 ± 10 CFU/mL, a full order lower than neat PDMS imprints (670 ± 140 CFU/mL), illustrating the beneficial effect of the dopant on the thermo-dynamical properties of the interfacial layer. A parallel benchmarking of the thermal sensor with a commercial impedance analyzer was performed in order to prove the possibility of using the developed PDMS-GO receptors with multiple readout platforms. Moreover, S. aureus, C. sakazakii and an additional E. coli strain were employed as analogue species for the assessment of the selectivity of the device. Finally, because of the potential that this biomimetic platform possesses as a low-cost, rapid, and on-site tool for monitoring E. coli contamination in food safety applications, spiked fruit juice was analyzed as a real sample. Reproducible and sensitive results fulfill the limit requirements of the applicable European microbiological regulation.