Bioreactor Product Charge Variant Profile Assessment by the A2P2
System
To evaluate charge variant profile in a cell culture sample, the sample
must undergo affinity purification and buffer exchange to reduce the
salt content of the sample matrix before injection into an ion exchange
column. As shown in Figure 8b , the autosampler needle takes
manually collected or online samples from the vial or FTV and directs
them through an affinity capture column for cleanup. The column captures
the protein of interest, flushing the sample matrix to waste via the
FTV. The protein of interest is then eluted from the affinity capture
column and accumulates in the FTV as an affinity-purified sample. The
sample is subsequently diluted with the mobile phase of the charge
variant assay inside intermediate vials to lower the salt concentration
before injection into the analytical ion exchange column. If dilution
doesn’t sufficiently reduce the sample’s salt concentration, a desalting
column can perform a buffer exchange on the sample before injection for
analysis. However, samples that are free from cell culture medium and
meet the assay requirements for salt content require no affinity
capture/cleanup, dilution, or buffer exchange. These samples can be
directly injected into the ion exchange column for analysis.