Magnetoelastic Immunosensors: Amplified Mass Immunosorbent Assay for Detection of Escherichia coli O157:H7

A mass-sensitive magnetoelastic immunosensor for detection of Escherichia coli 0157:H7 is described, based on immobilization of affinity-purified antibodies attached to the surface of a micrometer-scale magnetoelastic cantilever. Alkaline phosphatase is used as a labeled enzyme to the anti-E. coli 0157:H7 antibody, amplifying the mass change associated with the antibody—antigen binding reaction by biocatalytic precipitation of 5-bromo-4-chloro3-indolyl phosphate in a pH 10.0 PBS solution. The detection limit of the biosensor is 10^2 E. coli 0157:H7 cells/mL. A linear change in the resonance frequency of the biosensor was found to E. coli 0157:H7 concentrations ranging from 10^2 to 10^6 cells/mL.