Development of QCM immunosensor to detect bacteria causing food poisoning
S-R Hong, D. Hur, S. Hong
Kangnung Natioanl University, KR
Keywords: QCM, immunosensor, food poisoning, staphylococcus, yersinia, listeria, salmonella
Abstract:A QCM immunosensor was developed to detect four main pathogenic bacteria causing food poisoning, staphylococcus, yersinia, listeria, and salmonella, using specific antibodies. Antibodies were immobilised on sensor chip with right direction without using protein A or G for a convenient regeneration procedure. MUA was used to construct a self assembled monolayer on quartz surface and the carboxyl residues were activated using EDC/NHS followed by reaction with carbohydrazine to produce hydrazide chip. Unreacted carboxyl residues were blocked by ethanolamine to prevent binding of antibody to the carboxyl residues. Antibody immobilised on hydrazide after oxidation to exposure aldehyde group in Fc region of IgG, resulting that the reactive portion of antibody, i.e. Fab, can be exposed and is able to bind to the antigen freely. Immuno sensor chip was produced for each of four bacteria and tested dose response as well as specificity. In the dose response test, the frequency was changed in dose dependent manner for all bacteria at doses between 1000 and 50 g of bacterial cells. However, the shift patterns were not the same in all bacteria tested in this study. It was observed that injection of salmonella and staphylococcus cells increased frequency in dose dependent manner while yersinia and listeria cells decrease frequency following their injection. Specificity of the sensor chip was studied by testing the affinity between tested bacteria and showed no significantly high affinity to each other. It was also demonstrated that the prepared sensor chip was stable enough to withstand repeated surface regeneration with 0.2 M Tris-glycine and 1 % DMSO, pH 2.3.