Kinetics of irreversible adsorption with diffusion: Application to biomolecule immobilization

The kinetics of irreversible adsorption has been modeled numerically for cases for which the rate-limiting process is adsorption through to those for which diffusion to the surface is rate limiting. Comparison with limiting analytical models shows that even for a system under diffusion control the Ilkovic diffusion model with rate proportional to the surface coverage does not describe the kinetics adequately. The best approximate analytical models are a simple first-order model for rate-limiting adsorption and the Ilkovic model for diffusion control. The models were compared to experimental quartz crystal microbalance data for the attachment of glucose oxidase to a self-assembled monolayer. Although none of the limiting analytical models could adequately describe the adsorption behavior of this system, excellent fits to the experimental data were obtained with the numerical model for rate-limiting adsorption with heat of adsorption proportional to coverage (Frumkin adsorption kinetics). Good agreement between the model and published adsorption data was also obtained for antigen adsorption to an antibody-modified surface and for oligonucleotides hybridizing with the surface-bound complementary oligonucleotides.