Developing Surface-Imprinted Polymers for the Impedimetric Detection of the Foodborne Pathogens Listeria monocytogenes and Salmonella Enteritidis

We report on the development of surface-imprinted polyurethane layers (SIPs) for the selective detection of the pathogenic bacteria Salmonella Enteritidis and Listeria monocytogenes. The imprints are made with living template bacteria, and, after template removal, the layers feature ca. 106 imprints per cm2, that can bind bacterial targets from aqueous solutions. The imprinted layers are characterized by atomic-force microscopy regarding their morphology and by contact-angle measurements to determine their surface-free energy with polar and dispersive contributions. The dispersive part dominates the recognition between target bacteria and SIP layers as shown in comparison to nonimprinted polyurethane layers. To quantify bacterial concentrations, the SIP-type receptors and nonimprinted layers are combined with impedance spectroscopy, resulting in detection limits well below 102 colony forming units (CFU) mL−1 (for both Listeria and Salmonella) in buffer solution with an analytical range up to 106 CFU mL−1. Measuring bacterial concentrations takes 60 min, which is much faster than cultivation-based techniques. We compare these results with literature data on alternative biosensing techniques, address current limitations of sensor-based bacterial detection, and provide an outlook towards forthcoming developments. Furthermore, we show that one can release receptor-bound, viable bacteria from the imprinted layers by sonication, making them accessible for downstream analysis with genomic tools.