Label-free flow cytometry analysis of subvisible aggregates in liquid IgG1 antibody formulations.

The objective of this study was to characterize and quantify label-free subvisible antibody particles in different formulations based on their size and physical properties by flow cytometry. Protein subvisible particles were prepared under various stress conditions and analyzed by applying different analytical techniques [light obscuration (LO), microflow imaging (MFI), and flow cytometry (FACS)] for the detection of aggregates. The capability of the FACS method to detect and count subvisible particles was evaluated and benchmarked against conventional techniques. FACS can analyze particles down to 500 nm reducing the gap between size-exclusion chromatography and LO. The applied methods of FACS, LO, and MFI displayed a proportional correlation between the total particle counts, however, FACS can provide additional information on the structural characteristics of such aggregated particles.