Biomimetic sensing of Escherichia coli at the solid-liquid interface: From surface-imprinted polymer synthesis toward real sample sensing in food safety

The incorporation of imprinted polymers (IP) into sensing devices has enabled the detection of a wide range of analytes going from molecules to whole cells. Biomimetic platforms for bacteria recognition possess the potential of being a low-cost and on-site testing technology for applications in food safety, where the accurate detection of pathogens is crucial for preventing disease. This work presents the optimization of a label-free thermal IP-based sensor for the detection of E. coli, a microorganism indicator of fecal contamination in drinking water and milk. By modifying the functional monomers employed in the synthesis of imprinted polyurethanes, the production process was sped up by a factor four. The receptor layers, which exhibited enhanced imprint surface-coverage, yielded in bacteria quantification at concentrations in the range of 1000 CFU/mL, an improvement of a full order of magnitude for the thermal sensor. Benchmarking of the results was performed with a commercial impedance analyzer, demonstrating the suitability of the receptors for electrochemical analysis. Furthermore, the results presented assess the selectivity of the thermal device against S. aureus. Finally, a proof of concept of the sensor in milk as complex sample is presented for the first time, confirming that the dynamic range and sensitivity of the device will suffice to detect fecal contamination of milk samples in resource-deprived settings.