Easing Ion-Exchange Chromatography

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.

Collaboration works

As Patrick explains, collaboration is very important to us at Tosoh, and we have contact with many companies and research institutes. Yes, we sell our products, but I like to say that our expertise is something that we offer for free! It’s very rewarding that customers see us as experts who they can ask for help when they have a problem with developing methods, or choosing the best material conditions for a specific program. One of our collaborative projects involved the Max-Planck Institute for biochemistry in Martinsried (Germany), one of the largest institutes within the Max Planck Society, and we’re proud to share their feedback: 

Leopold Urich, scientist in the group of Sabine Suppmann (Head Recombinant Protein Production), works in the Institute’s core facility – one of many service facilities devoted to supporting the scientists during their work. Among the many areas of expertise, the Institute is working in the field of “recombinant protein production” – essentially, developing strategies for protein expression and purification. As a result, all of Urich’s projects require some form of chromatography.

Urich described Tosoh’s Toyopearl Sulfate-650F and Toyopearl NH2-750F as breakthroughs for his work because ion-exchange was something the group had been struggling with. “The biggest issue has always been the binding conditions with other ion-exchange resins, meaning very low salt concentrations,” says Urich. “Most of the material we are working with simply can’t withstand such low amounts of salt. This problem has since been eliminated and, on top of that, we’re seeing some great separation results in our testing, even with simple linear gradients especially with the Toyopearl anion exchange columns.”

Tosoh has also worked with Sanofi, and generated more positive feedback. Benoit Mothes, Head of Sanofi’s Global DSP Breakthrough Technologies Skill Center, says, “The Toyopearl NH2-750F anion exchange resin is the greatest innovation from the past 10 years in the downstream processing field.” 

We are always open for collaboration with the industry. If you are interested in working with us, please email: [email protected].

Dr. Romain Dabre is Product Manager, Process Business at Tosoh Bioscience, Germany.