ADSORPTION-KINETICS OF PROTEINS ONTO SOLID-SURFACES IN THE LIMIT OF THE INTERFACIAL INTERACTION CONTROL

We have developed an experimental set-up using radiolabelled proteins for the continuous measurement, as a function of time, of the excess concentration of superficial protein at a solid/liquid interface. The experimental conditions were designed in order to minimize the coupling of the interfacial interaction with bulk diffusion, and therefore to work within the limit of the interfacial interaction control. Chemical kinetics were assumed to follow a Langmuir equation. The absorption (Ka) and desorption (Kd) rate constants have been evaluated in the case of fibrinogen and albumin adsorption, onto glass beads and synthetic hydroxyapatite powder, respectively. In order to determine these parameters, a non-linear differential equation (obtained by combining the Langmuir rate equation and a mass-balance equation) was solved by the fourth-order Runge-Kutta method. The results obtained are consistent with the hypothesis of an adsorption rate controlled by the interfacial interaction.