Recognition of bacterial lipopolysaccharide using bacteriophage-adhesin-coated long-period gratings

In this paper we present a new type of highly sensitive label-free sensor based on long-period gratings (LPG) coated with T4 bacteriophage (phage) adhesin. The adhesin (gp37) binds Escherichia coli B (E. coli B) by recognizing its bacterial lipopolysaccharide (LPS). The LPG biofunctionalization methodology is based on coating LPG surface with nickel ions capable of gp37 histidine tag reversible binding. For the first time recombinant adhesive phage protein has been used as a receptor molecule in biosensing scheme. The specificity of LPS binding by adhesin has been tested with LPG-based device and confirmed using Western blot, Enzyme-Linked Immunosorbent Assay (ELISA) and BIACORE methods. The LPG-based sensor can measure bacterial contamination in real time and with a high accuracy. We show that T4 phage adhesin binds E. coli B LPS in its native or denatured form. The binding is highly specific and irreversible. The applied procedure allows for obtaining reusable biosensors.