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. 2021 Jan 5;7(1):183–199. doi: 10.1021/acscentsci.0c01405

Figure 2.

Figure 2

Spike ferritin nanoparticles can be expressed in mammalian cell culture and purified to homogeneity. (A) Scheme for expressing and purifying spike ferritin nanoparticle antigens in mammalian cells. Spike ferritin particle subunits are encoded in a single plasmid that is transfected into the Expi293F suspension human cell line. Expi293F cells are harvested, and culture supernatant is buffer exchanged and purified via anion exchange chromatography. Protein-containing fractions are identified via Western blot, pooled, and purified by size-exclusion chromatography (SRT SEC-1000). Purified nanoparticles are assessed using biophysical characterization methods including SDS-PAGE, analytical size-exclusion chromatography, and BLI follow by in vivo characterization of the immune responses elicited in mice. (B) SEC-MALS UV A280 (left) and light scattering signals (right) from analysis of spike-based ferritin antigens using an SRT SEC-1000 size-exclusion column. A single prominent peak in both the UV and light-scattering traces confirms that spike ferritin nanoparticle preparations are homogeneous and do not aggregate.