Performance of affinity biosensors with competitive displacement mechanism

A mathematical model was developed for affinity biosensors where the detection principle is based on competitive displacement of a protein from an immobilized ligand. Two competing binding reactions between analyte and protein molecules in the bulk liquid phase, and immobilized ligand and protein molecules in the solid phase, were assumed to be in equilibrium. Theoretical calibration curves relating the signal generated, which is the total protein concentration detected in the bulk liquid phase, to the analyte concentration were calculated from this model. The simulated results indicated several important variables to consider when constructing the biosensor. The amount of responsive protein and immobilized ligand initially loaded and the relative binding strength of both the analyte and the ligand toward the protein will influence the biosensor's performance. Experiments have been carried out to verify this model, using bovine rennin as the protein, pepstatin‐agarose as the immobilized ligand, and pepstatin as the analyte. The experimental data agreed reasonably well with the simulated results from the model. This mathematical model seemed to be sufficient for describing the behavior of affinity biosensors based on competitive displacement and suitable for design purposes.