Diffusion-Capture Model
Time dynamics of molecule capture on a sensor surface is essentially a two step process: transport of the target molecules to the sensor surface and the subsequent conjugation with the receptor molecules. The diffusion - Capture (D-C) model is widely used to describe this process. The model assumes that the molecule transport is diffusion-limited and the target-receptor conjugation is treated as a first-order chemical reaction. The model equations are:
Eq. (1a) represents the diffusion of target molecules to the sensor surface where D and ρ are the diffusion coefficient and concentration of target biomolecules (analyte) in solution, respectively. Eq. (1b) represents the capture of biomolecules by the receptors on sensor surface, where N is the density of conjugated receptors, N0 is the total density of receptors on the sensor surface, kF and kR are the capture and dissociation constants, and ρs is the concentration of target analyte particles at the sensor surface.