Easing Ion-Exchange Chromatography
Why salt-tolerant resins make for “happier” biomolecules with better binding.
Romain Dabre |
sponsored by Tosoh
Process chromatography is one of the main components of downstream processing. One of the most commonly-used chromatography techniques for the purification of recombinant biomolecules is ion-exchange chromatography. It is, for example, the preferred step after protein A capture for the intermediate purification of antibodies and antibody constructs. Ion-exchange chromatography uses the ionic charges on the surface of the proteins to bind and elute, and requires specific buffer conditions. Often, a desalting or dilution step is required to ensure proper binding of the target to the ion exchanger.
The introduction of salt-tolerant ion-exchange chromatography resins has been appreciated by the industry. Salt tolerant means that the binding of biomolecules will work at higher salt concentrations than on traditional ion exchange. Normally in ion-exchange chromatography, you bind the biomolecule on the column and elute your target by increasing the salt concentration. Typically, that means the feedstock needs to be salt-free before going onto the chromatography steps, adding time and money to the process. With salt-tolerant ion-exchange chromatography resins, you can work with a higher salt concentration for binding, allowing for more straight-forward processes with less steps and/or less dilution while maximizing productivity through high dynamic binding capacity (DBC). For example, the salt-tolerant cation exchanger Toyopearl Sulfate-650F exhibits DBCs up to 120 g/L at salt concentrations as high as 0.3 mol/L. Another example of the unique performances of these resins is the capacity of the salt-tolerant anion exchanger Toyopearl NH2-750F to remove mAb-aggreagtes along with viruses, endotoxins, DNA and HCP, paving the way for reducing the number of steps in antibody purification.
It is also important to point out that biomolecules are natural structures – and when existing in humans or plants there is always the presence of salt. Being without salt, as required in conventional ion-exchange chromatography, goes against the laws of nature, and some proteins do not like these conditions. In this way, salt-tolerant ion-exchange chromatography has a huge advantage. Although they have only been on the market a few years, our salt-tolerant resins are already being used in phase III pre-commercial manufacturing steps. In some ways, it is remarkable how these resins have made it to this stage so quickly – but there’s a simple reason for the rapid uptake: they solve previously intractable problems. And I would say that they are perfect for newer antibody formats coming through pipelines.
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