Adsorption rate constants of therapeutic proteins and surfactants for material surfaces.

Adsorption of therapeutic proteins to material surfaces can be a pivotal issue in drug development, especially for low concentration products. Surfactants are used to limit adsorption losses. For each formulation component, surface adsorption is the result of a combination of its diffusion and surface adsorption rates. The latter are difficult to measure accurately because a depletion layer forms rapidly in the bulk solution above a bare surface, slowing down adsorption. Adapting flow conditions and local surface chemistry, we are able to minimize depletion limitations and measure apparent adsorption rate constants of three monoclonal antibodies, other proteins and surfactants with a hydrophobic surface. We show that surface adsorption rates scale with the molecular mass of the molecule, with polysorbates therefore showing thousand times slower rates than antibodies. Moreover, we observed that the desorption dynamic of polysorbates from a given hydrophobic surface depends on surface coverage, whereas this is not the case for Poloxamer 188. These novel contributions to surface adsorption dynamics enable a new perspective on the evaluation of drug surface compatibility and can, together with diffusion rates, be used to predict the protective potential of surfactants in given conditions.