Abstract
Understanding the structure and self-organisation of monoclonal antibodies (mAbs) at the air-water interface is crucial for the stability and efficacy of protein drug formulations. This paper investigates the competitive adsorption of mAb and two amphiphilic polymers, poloxamer 188 (P188) and polysorbate 20 (PS20), commonly used to stabilise mAb formulations. Our objective was twofold: to ascertain whether the surfactants in question are capable of preventing mAb adsorption; and to determine whether it is possible to desorb mAb molecules from the air-water interface by surfactant addition. Langmuir film balance measurements and drop shape tensiometry were used to obtain surface pressure and surface tension data. Infrared Reflection-Absorption Spectroscopy (IRRAS) provided information on the surface composition, including the amount of adsorbed molecules. The state adopted by P188 is contingent upon its surface concentration, which determines the self-assembled phases it adopts. We show that the phase state of P188 has a considerable influence on mAb adsorption. The presence of P188 in the brush phase (≥ 0.3 mg/L) consistently inhibits mAb adsorption, but addition of P188 subsequent to the formation of the mAb film does not result in mAb desorption. However, addition of PS20 results in the desorption of freshly-formed interfacial mAb layers of up to two hours' age, whereas an aged mAb layer of 17 h was unable to be desorbed by PS20. Thus there is a time-dependent reorganisation of mAb at the air-water interface, increasing resistance to desorption, which we discuss in the context of potential intermolecular interactions within the interfacial film.