Competitive Adsorption of a Monoclonal Antibody and Amphiphilic Polymers to the Air-Water Interface

Understanding structure and self-organization of monoclonal antibodies (mAbs) at the air-water interface is important for the stability and effectiveness of protein drug formulations used in pharmaceutical industry. This paper investigates the competitive adsorption of a mAb and the amphiphilic surfactants poloxamer 188 (P188) and polysorbate 20 (PS20), both of which are commonly used to prevent mAb surface adsorption. Firstly, it is studied whether these surfactants prevent mAb adsorption, and secondly, whether it is possible to desorb mAb molecules from the air-water interface by surfactant addition. For surface pressure and surface tension data, Langmuir film balance measurements and drop shape tensiometry were used. Infrared Reflection-Absorption Spectroscopy (IRRAS) provided information on the surface composition, including the amount of adsorbed molecules. P188 exists in different self-assembled phases depending on its surface concentration. Our experiments show that the phase state of P188 has a significant impact on mAb adsorption. The presence of P188 in the brush phase (≥ 0.3 mg/L) consistently inhibits mAb adsorption. On the contrary, addition of P188 after mAb film formation could not cause desorption of mAb. However, addition of PS20 leads to desorption of freshly formed interfacial mAb layers of up to two hours age. Interestingly, an aged mAb layer of 17 hours could not be desorbed by PS20. This suggests a time dependent reorganization of mAb at the air-water interface, which increases its resistance to desorption. These findings are discussed with respect to possible inter-molecular interactions within the interfacial film.