Novel surface plasmon resonance biosensor that uses full-length Det7 phage tail protein for rapid and selective detection of Salmonella enterica serovar Typhimurium

We report a novel surface plasmon resonance (SPR) biosensor that uses the full-length Det7 phage tail protein (Det7T) to rapidly and selectively detect Salmonella enterica serovar Typhimurium. Det7T, which was obtained using recombinant protein expression and purification in Escherichia coli, demonstrated a size of ∼75 kDa upon SDS-PAGE and was homotrimeric in its native structure. Micro-agglutination and TEM data revealed that the protein specifically bound to the host, S. Typhimurium, but not to non-host E. coli K-12 cells. The observed protein agglutination occurred over a concentration range of 1.5∼25 μg.ml−1. The Det7T proteins were immobilized on gold-coated surfaces using amine-coupling to generate a novel Det7T-functionalized SPR biosensor, wherein the specific binding of these proteins with bacteria was detected by SPR. We observed rapid detection of (∼ 20 min) and typical binding kinetics with S. Typhimurium in the range of 5 × 104-5 × 107 CFU.ml−1, but not with E. coli at any tested concentration, indicating that the sensor exhibited recognition specificity. Similar binding was observed with 10% apple juice spiked with S. Typhimurium, suggesting that this strategy could be expanded for the rapid and selective monitoring of target microorganisms in the environment.