Buffer exchange & sample preparation

The problem

Buffer exchange and sample concentration is part of everyday life for scientists working with antibodies and recombinant proteins. Whether it’s for sample prep, preparing for labeling or characterization, or developing formulation screening and optimization strategies for a biologic, the process is monotonous, labor-intensive, time-consuming, and prone to error.

Conventional buffer exchange methods like dialysis and centrifugal filtration suffer from inconsistency in results and are often hard to manage in larger numbers. Sample concentration is usually an additional time-consuming step. Most methods require hands-on time, taking researchers away from other critical work.

The right tools for the job

Unagi is the first benchtop buffer exchange platform that brings together all the painful, hands-on steps it takes to get a molecule moved from one buffer to another or concentrated up into a working range. Unagi uses ultrafiltration/diafiltration (UF/DF) to exchange 1 to 8 samples from a starting volume of 0.5 to 8 mL. Unagi keeps careful track of sample volumes during a run, filters samples down and knows what volumes to add back to each sample. It repeats this cycle until each sample hits the target percent exchange or concentration.

The secret sauce

Unagi uses a consumable called the Una. Each Una holds 0.5 to 8 mL of sample and Unagi handles 1-8 Unas per run. They use regenerated cellulose (10, 30, and 100 kDa MWCOs) and polyethersulfone (30 and 100 kDa MWCOs) membranes to make sure your samples stay put, don’t get absorbed, and the liquid passes right through — with ≥96% recovery.

Served up a'la carte

Big Tuna is a fully automated buffer exchange system that provides a more uniform sample handling approach and degrees of process control that you just can’t get with manual methods. Big Tuna uses a modified ultrafiltration/diafiltration (UF/DF) method to exchange and concentrate proteins from 0.1 – 200 mg/mL. Big Tuna monitors the sample volumes during the run, adds back the filtered volume and gets your samples to the right percent exchange and concentration every time.


Big Tuna uses a plate-based consumable called the Unfilter. All Unfilters use a regenerated cellulose membrane which is ideal for proteins because it minimizes non-specific binding. They come in 2 formats, 24-well (0.45 – 8 mL) or 96-well (100 – 450 µL). The Unfilter 96 is available with molecular weight cutoffs of 3, 10, 30, and 100 kDa. The Unfilter 24 has 10, 30, and 100 kDa MWCOs. So no matter what size the protein is or what volume is available, Big Tuna has the right format.


Both Unagi and Big Tuna use a UF/DF method with gentle orbital mixing that gives you consistent results without the drawbacks of dead-end ultrafiltration techniques. This matters because at high protein concentrations, the risk of aggregation goes up and proteins may gel at the membrane. Orbital mixing helps the sample flow faster and reduces the potential for aggregation.


The proof

Buffer exchange with Unagi

Whether you want to exchange 1 protein into 8 buffers, 8 different proteins into 1 buffer or anything in between, it only takes minutes to load up Unagi and it's off to the races.

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Fast formulation screening and optimization with Big Tuna

Screening for the optimal pH for your antibody is easier than ever before. It only takes 30 minutes to set up and you’ll be running your stability measurements in no time.

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Dialing in your formulation with Big Tuna

Finding the right excipients to keep your proteins happy is a challenge. Big Tuna can help you with this too. At this stage of formulation development these samples aren’t likely to run uniformly. Big Tuna has you covered by constantly monitoring the volume and flow rate so it can exchange the slowpokes without letting the speedster wells go dry. If you want to concentrate them up to dosable levels at the end, Big Tuna can do that too.

Dialing in your formulation


Buffer exchange and concentration are two of the most annoying things you have to do before you can work with your sample, even for just a handful. It takes forever, you physically have to be there and just when you think it’s done, you’re tweaking it again, even for a handful of samples. Unagi is the first completely hands-free benchtop buffer exchange solution that’s made to take this not-so-fun task off your plate — so you can be anywhere else instead of tied to your bench.

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Big Tuna

Buffer exchange and sample concentration are the time consuming, hands-on chores you must deal with before all the things you really want to do. Big Tuna is a fully automated, plate-based buffer exchange platform that uses a modified UF/DF method and gentle mixing to buffer exchange, concentrate, and clean up proteins, nucleic acids, or gene therapy vectors like AAVs and LNPs. Skip the slow and manual ways of prepping samples to free yourself up for other critical work.

Want more info?

Want to learn more about how Unagi and Big Tuna free you up from buffer exchange?