Characterization and differential retention of Q beta bacteriophage virus-like particles using cyclical electrical field–flow fractionation and asymmetrical flow field–flow fractionation

Virus-like particles (VLPs) are widely used in medicine, but can be difficult to characterize and isolate from aggregates. In this research, primarily cyclical electrical field–flow fractionation (CyElFFF) coupled with multi-angle light scattering (MALS), and dynamic light scattering (DLS) detectors, was used for the first time to perform size and electrical characterization of three different types of Q beta bacteriophage virus-like particles (VLPs): a blank Q beta bacteriophage which is denoted as VLP and two conjugated ones with different peptides. The CyElFFF results were verified with transmission electron microscopy (TEM). Asymmetrical flow field–flow fractionation (AF4) coupled with MALS was also applied using conditions similar to those used in the CyElFFF experiments, and the results of the two techniques were compared to each other. Using these techniques, the size and electrophoretic characteristics of the fractionated VLPs in CyElFFF were obtained. The results indicate that CyElFFF can be used to obtain a clear distribution of electrophoretic mobilities for each type of VLP. Accordingly, CyElFFF was able to differentially retain and isolate VLPs with high surface electric charge/electrophoretic mobility from the ones with low electric charge/electrophoretic mobility. Regarding the size characterization, the size distribution of the eluted VLPs was obtained using both techniques. CyElFFF was able to identify subpopulations that did not appear in the AF4 results by generating a shoulder peak, whereas AF4 produced a single peak. Different size characteristics of the VLPs appearing in the shoulder peak and the main peak indicate that CyElFFF was able to isolate aggregated VLPs from the monomers partially. Graphical abstract