Carbohydrate-Functionalized Nanobiosensor for Rapid Extraction of Pathogenic Bacteria Directly From Complex Liquids With Quick Detection Using Cyclic Voltammetry

Complex liquid matrices present a serious challenge to proposed nanobiosensing methods in literature. Biosensors that rapidly detect bacteria directly from complex liquid foods, at economical costs, will increase food supply security. Carbohydrate ligands are inexpensive antibody and oligonucleotide replacements for sensitive biosensor development with long-shelf life. In this pilot study, carbohydrate-functionalized magnetic nanoparticles (MNP) affixed to a “dip-stick” (MNP-strip) could extract pathogenic bacteria from various liquid foods in only 10 min, and then detect presence with an additional 10 min, for a total 20 min from microbial extraction to detection. MNP-strips captured Salmonella Enteritidis, Escherichia coli O157:H7, and Listeria monocytogenes directly from the complex matrices of homogenized egg, vitamin D milk, and apple cider, respectively. Cyclic voltammetry (CV), using a chemical mediator, significantly distinguished between MNP-strips with bacteria present and those only exposed to uncontaminated matrix (p <; 0.05). Signal differences for cell capture in complex matrices versus simple matrices were also evaluated. In simple matrices, CV normalized peak current responses (NPCR) for capture of Salmonella Enteritidis from PBS and E. coli from beef juices showed that samples (S) with cells present showed lower NPCR than negative controls (N), with S/N less than 1.0, whereas sample NPCR in complex matrices were higher than those for the negative controls, with S/N ratios greater than 1.0. When negative controls were exposed only to the matrix, linear regression indicated that NPCR was indirectly related to sodium and fat content, but directly related to protein content (p <; 0.05).