Antibody properties for chemically reversible biosensor applications

A recently reported fiber-optic sensor based on a homogeneous fluorescence energy-transfer immunoassay operates in a continuous, reversible manner to quantify the anticonvulsant drug phenytoin (5,5-diphenylhydantoin). The chemical kinetics of the two simultaneous antibody-hapten (analyte) and antibody-hapten (labeled indicator) reactions in the sensor are now modeled mathematically. Simulation shows that the chemical response time is controlled by the dissociation rate constant and is independent of the association rate constant, and that an equalibrium chemical response can be achieved in minutes. The sensitivity and dynamic range of the analyte concentration which can be measured depends on the ratio of dissociation rate constants for the labeled and unlabeled hapten reactions, and on the total concentration of reactants in the sensor. The relative concentration ratios of antibody to labeled hapten has little impact on the sensitivity or dynamic range of the system, but can be optimized to provide the maximum amount of labeled hapten availble for instrumental measurement.