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Escherichia coli (E. coli) contamination in foods and water resources represents a major threat for human health and the environment. This work exploits the strong affinity of mannose-containing oligosaccharides with the fimbrial lectin of E. coli to design novel biosensors. Modified carbohydrate ligands were synthesized by introducing phenyl residues and aliphatic chains to mannose via reductive amination in order to increase both the affinity and selectivity to E. coli compared to other pathogenic bacteria. The synthesized ligands include p-thiolphenyl aminomannose (PTAM), p-carboxyphenyl aminomannose (PCAM), 1-deoxy-1-aminomannopyranoside (DAMP), glucosamine and low molecular weight chitosan bonded to mercapto undecanoic acid. The structures of the ligands were confirmed using 1H NMR and 1H, 13C, COZY NMR, and ESI/MS. The ligands were immobilized onto gold electrodes and SPR surfaces using-mercaptoundecanoic acid with glycine as deactivating agent. Two detection mechanisms were tested: (i) metal-enhanced electrochemical detection (MED) and (ii) label-free surface plasmon resonance (SPR) detection. The introduction of phenyl residues and aliphatic side groups to the mannose-containing oligosaccharides produced extremely high affinity for E. coli with detection limit of 1cfu/mL. The relative selectivity of these ligands for E. coli, Citrobacter freundii, Staphylococcus epidermidis were 100%, 2.6% and 8.6% respectively. The biosensors were validated using spinach leaves at 3.0cfu/mL. The work provides a generic biosensor for other pathogenic bacteria by enabling multivalent binding, immediate recognition for pathogens as well as inhibition of bacterial growth. [ABSTRACT FROM AUTHOR]

Structural alterations of the aglycon portions of α-mannosides influence their inhibitory potency toward type 1-fimbriated Escherichia coli. The aim of our work was to prepare and explore inhibitory properties of novel mannosylated N-aryl-substituted 3-hydroxypyridine-4-ones because they possess needed structural characteristics as possible Fim H antagonists. Hemagglutination inhibitory tests showed that the examined 3-hydroxypyridine-4-one α-mannosides exhibited better inhibitory activity than methyl α- d-mannopyranoside used as a reference compound. Molecular modeling studies revealed the specific interactions responsible for the observed binding activities toward the mannose-specific Fim H lectin. The activity depends on the substituent in p-position on the aglycon aromatic ring. [ABSTRACT FROM AUTHOR]