Biosensor for selective detection of E. coli in spinach using the strong affinity of derivatized mannose with fimbrial lectin

• Published in: Biosensors & bioelectronics Vol. 61; pp. 266 - 273
• Main Authors: Yazgan, Idris, Noah, Naumih M., Toure, Ousmane, Zhang, Siyi, Sadik, Omowunmi A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.11.2014; Elsevier
• Subjects: Adhesins, Escherichia coli - metabolism; Affinity; Aliphatic compounds; Bacteria; Biological and medical sciences; Biosensors; Biotechnology; Citrobacter freundii; Electrochemical Techniques - methods; Escherichia coli; Escherichia coli - isolation & purification; Escherichia coli - metabolism; Fimbriae Proteins - metabolism; FimH lectin; Fundamental and applied biological sciences. Psychology; Lectins; Ligands; Limit of Detection; Mannose - analogs & derivatives; Mannose - metabolism; Mannose-binding protein; MED; Methods. Procedures. Technologies; Nuclear magnetic resonance; Oligosaccharides; Spinacia oleracea; Spinacia oleracea - microbiology; SPR; Staphylococcus epidermidis; Surface Plasmon Resonance - methods; Various methods and equipments; FimH lectin; Mannose-binding protein; SPR; MED; Escherichia coli; Lectin; Mannose; Selectivity; Surface plasmon; Binding protein; Biosensor; Bacteria; Affinity; Detection; Enterobacteriaceae
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2014.05.008

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. •Detection of E.coli at 1cfu/mL demonstrated using derivatized ligands.•Derivatization increased both selectivity and sensitivity to E. coli.•High affinity derived from π-π interactions and aromatic side rings.•Structures of ligands confirmed using 1H NMR and 1H, 13C, COSY NMR, and ESI/MS.•Label-free MED and SPR detection demonstrated.