Surface Activity Changes after Photoirradiation of PS80 in Citrate Buffer Containing Iron and Disulfide

Polysorbate 80 (PS80) is a commonly used surfactant for stabilizing biotherapeutics by preventing protein adsorption at the air–liquid interface. However, PS80 is susceptible to oxidative degradation during manufacturing and storage. We show here that light exposure combined with the presence of metals can result in byproduct formation and potentially decrease the surfactant’s ability to prevent protein adsorption to the air–liquid interface. PS80 formulated in citrate buffer can undergo cis/trans isomerization of unsaturated fatty acids in the presence of disulfides and iron (Prajapati et al., 2022). This work investigates novel surface activity aspects of polysorbate formulations before and after exposure to UV-A light. Polysorbate samples of different grades were formulated in citrate buffer containing iron and glutathione disulfide (GSSG; as a surrogate for peptide and protein disulfides), and a Langmuir trough was used to monitor the surface pressure during adsorption to the air–solution interface. Our results showed significant changes in the polysorbate surface activity after photoirradiation: all-oleate PS80 exhibited a 3-fold increase in the apparent critical micelle concentration (CMC), and the presence of both cis and trans fatty acids was confirmed. Also, the impact of photoirradiation on surface pressure depended on the surfactant concentration during irradiation, suggesting that the presence of micelles can alter the degradation pathway and byproduct formation.