For removing plasmid endotoxins, which offers a better balance between recovery rate and efficiency: ion exchange or affinity chromatography?

<p>If you must choose between the two, ion exchange offers better recovery and scale-up efficiency, but its depth of endotoxin removal is inferior to that of affinity membranes. The key to balancing this lies in placing endotoxin testing at every step: measure once after crude purification, and if it has already dropped below 0.5 EU/µg, passing it through an affinity membrane will easily achieve the target.</p>

For consumables selection, for anion exchange columns, you can consider prepacked columns or membranes from Cytiva, Sartorius, and Bio-Rad; for affinity membranes, look at Mustang E, the Sartobind series, and Thermo products. When comparing, it is advisable to ask vendors to provide dynamic binding capacity, endotoxin removal validation, and reuse cycles, rather than just looking at column volume. At the 500 mL–1 L scale, using disposable small-area membranes or small prepacked columns is more flexible than buying large finished purification kits, but consumable costs are heavily influenced by brand, membrane area, and whether they are reused, so you can only have sales quote based on your batch. If the endotoxin requirement for AAV packaging is a hard specification, I suggest including LAL testing consumables in the cost; before reusing membranes, cleaning validation must be performed to avoid cross-contamination.

<p>From the perspective of chromatography principles, ion exchange columns primarily separate substances based on charge. Both supercoiled plasmids and endotoxins carry negative charges, and a single Q/DEAE column often cannot completely separate the two. This is especially true when scaling up to 500 mL–1 L of bacterial culture, where achieving consistent</p>

We set up plasmid purification in-house in our lab, starting with about 500 mL of bacterial culture. The workflow is: alkaline lysis + isopropanol precipitation + RNase digestion, then using a Capto Q or Mustang Q anion exchange prepacked column, collecting the main peak, and then passing it through a Sartobind or Mustang E endotoxin affinity membrane. With this route, supercoiled plasmid recovery can generally be maintained at 70–85%, and endotoxin detection can be below 0.05 EU/µg, but it is not fixed for every batch and needs to be fine-tuned according to plasmid size and bacterial biomass. AAV packaging plasmids are best extracted fresh; repeated freeze-thaw cycles increase the proportion of open circular forms and affect subsequent transfection. All buffers and bottles should be endotoxin-depleted in advance.