Analytical techniques for detecting and characterizing protein aggregates in inhaled formulations

Pulmonary delivery of therapeutic proteins for the management of respiratory diseases has been receiving research attention, particularly after the COVID-19 pandemic. Yet its development barriers include the propensity of proteins to form aggregates, which poses a major challenge to protein stability.

This article presents a summary on protein aggregation, illustrating its significance and the challenges associated with protein drug development. It is followed by an overview of various analytical techniques—as well as some emerging techniques with promising potential—that have been used for the detection and characterization of protein aggregates in inhaled formulations. Techniques include those for visible particles: visual inspection; for subvisible particles: microscopy, light obscuration and flow imaging microscopy; and for submicronic particles: UV absorbance, dynamic light scattering, PAGE, SEC-HPLC, nanoparticle tracking analysis and mass photometry.