An Interlaboratory Comparison on the Characterization of a Sub-micrometer Polydisperse Particle Dispersion.

The measurement of polydisperse protein aggregates and particles in biotherapeutics remains a challenge, especially for particles with diameters of ≈ 1 µm and below (sub-micrometer). This paper describes an interlaboratory comparison with the goal of assessing the measurement variability for the characterization of a sub-micrometer polydisperse particle dispersion composed of five sub-populations of poly(methyl methacrylate) (PMMA) and silica beads. The study included 20 participating laboratories from industry, academia, and government, and a variety of state-of-the-art particle-counting instruments. The received datasets were organized by instrument class to enable comparison of intralaboratory and interlaboratory performance. The main findings included high variability between datasets from different laboratories, with coefficients of variation from 13 % to 189 %. Intralaboratory variability was, on average, 37 % of the interlaboratory variability for an instrument class and particle sub-population. Drop-offs at either end of the size range and poor agreement on maximum counts of particle sub-populations were noted. The mean distributions from an instrument class, however, showed the size-coverage range for that class. The study shows that a polydisperse sample can be used to assess performance capabilities of an instrument set-up (including hardware, software, and user settings) and provides guidance for the development of polydisperse reference materials.

Critical Evaluation of Microfluidic Resistive Pulse Sensing for Quantification and Sizing of Nanometer- and Micrometer-Sized Particles in Biopharmaceutical Products.

The objective was to evaluate performance, strengths, and limitations of the microfluidic resistive pulse sensing (MRPS) technique for the characterization of particles in the size range from about 50 to 2000 nm. MRPS, resonant mass measurement (RMM), nanoparticle tracking analysis (NTA) and dynamic light scattering were compared for the analysis of nanometer-sized polystyrene (PS) beads, liposomes, bacteria, and protein aggregates. An electrical conductivity of at least 3 mS/cm (equivalent to 25 mM NaCl) was determined as a key requirement for reliable analysis with MRPS. Particle size distributions of PS beads determined by MRPS, NTA, and RMM correlated well. However, counting precision varied significantly among the techniques and was best for RMM followed by MRPS and NTA. As determined by measuring single and mixed PS bead populations, MRPS showed the highest peak resolution for sizing. RMM and MRPS were superior over dynamic light scattering and NTA for the characterization of stressed protein samples. Finally, MRPS proved to be the only analytical technique able to characterize both bacteria and liposomes. In conclusion, MRPS is an orthogonal technique alongside other established techniques for a comprehensive analysis of a samples particle size distribution and particle concentration.