Development of Flow Imaging Analysis for Subvisible Particle Characterization in Glatiramer Acetate

A comparison of background membrane imaging versus flow technologies for subvisible particle analysis of biologics

A recently developed high-throughput background membrane imaging (BMI) technique, the HORIZON, was assessed for its ability to quantify subvisible particulate (SVP) generated during protein therapeutic development. The HORIZON platform method was optimized and compared to three well-characterized SVP counting techniques: light obscuration, micro-flow imaging (MFI), and FlowCam®. A head-to-head comparison was performed for precision, linearity, SVP concentration, and morphological output of BMI compared to the other three techniques using two unique enzymes under investigation. We found that dilution requirements for BMI are protein-specific, and membrane coverage is the critical instrument parameter to monitor for dilution suitability. The precision of BMI ranked similarly to all other techniques. Analysis of the same sample dilution, run in triplicate, across all four techniques indicated the BMI technique provides SVP concentrations that are comparable with the flow imaging techniques. Morphological information from BMI was generally less practical when compared with flow microscopy. The major drawback of BMI was that the current software indiscriminately clips large particles, potentially resulting in a misrepresentation of SVP size distribution. Despite this phenomenon, the concentration and size data generated corresponds well with current flow imaging techniques while decreasing time, cost, and sample requirements for SVP quantification.

Variability in Flow-Imaging Microscopy Measurements and Considerations for Biopharmaceutical Development

Flow-imaging microscopy is widely used in the biopharmaceutical industry to characterize populations of subvisible (1-100 μm) particles due to high sensitivity and the ability to discriminate different particle morphologies. The present work provides a comprehensive assessment of the capabilities of flow-imaging microscopy by exploring the impacts of a variety of factors on the observed variability of these measurements. A novel graphical presentation is proposed to facilitate both determination of expected levels and detection of potential atypical results. Data collected across different products and container-closure systems illustrate that a substantial amount of historical experience is typically required to adequately define the expected levels of subvisible particles for any specific system. It is also shown, however, that an appropriate level of control can be demonstrated without the need to pool large numbers of containers or perform replicate measurements.