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Ask the Expert: Acoustic Cell Processing

Kevin Lannon

May 15, 2019

4 Min Read

As cell and gene therapies approach commercialization, the industry is looking for scalable manufacturing solutions. Equipment providers need to design specifically for the good manufacturing practice (GMP) environment and the unique needs of cell and gene processing. On 3 April 2019, Kevin Lannon of FloDesign Sonics presented an “Ask the Expert” on one company’s solution.

In a typical cell therapy manufacturing process, steps that require washing, concentration, or buffer exchange include centrifugation, filtration, and counterflow filtration. Each has inherent concerns such as cell shear, or clogging and fouling. New technologies should address these shortcomings and maintain or improve the quality of cell products being processed.

Acoustophoresis works by generating a forward-propagating wave that bounces off a reflector, and the two resulting waves together create a standing wave that can be tuned to different strengths. Cells entering the flow path are captured by acoustics into low-energy nodes, where they form loose clusters. Once those clusters reach a certain radius (depending on cell size and fluid flow rate), gravity will cause them to settle. Users can tune the wave size to specify when cell clusters will drop out or even keep them in the acoustic field indefinitely. After turning off the system pumps and acoustics, users can pull supernatant from the top of the chamber and collect concentrated cell flurry from a drain port at the bottom.

At Phacilitate 2019, FloDesign Sonics launched its GMP-compatible acoustic-based ekko platform technology. Its three primary components are a system control unit (SCU) with a touchscreen for controlling process and acoustics; a fluid handling unit (FHU) housing pumps, valves, sensors, an integrated cooling loop, and the acoustic transducer itself; and a single-use cartridge with a completely integrated flow path. An ekko system comes with preprogrammed protocols for different cell types, concentrations, and volumes. The customizable software is 21CFR Part 11 compliant.

FloDesign Sonics has performed concentration experiments with multiple cell types. T cells were recovered from a 1-L input volume to maximize recovery in the shortest possible process time. The ekko platform achieved 96% recovery of viable cells from an initial starting solution in 68 minutes.

Experiments were also run with human pluripotent stem cells (hPSC) to manipulate aggregate percentage. The acoustic waves were tuned to hold aggregates within the field and allow single cells to pass through. After only two passes through the system, the cell solution had >98% aggregates and <2% single cells.

Other applications tested have included harvest wash, electroporation preparation, cryoprotectant addition and removal, and buffer exchange.

Can the technology be used for bioreactor cell retention? Generally we use transfer bags for such processes. But we have had multiple customers hook ekko systems directly to bioreactors. We can connect a sterile weld to a harvest or drain port.

How is the chamber cooled? An internal cooling loop circulates cooling fluid around the transducer (the primary source of heat) to maintain a constant process temperature.

What are the feed flow-rate limits? The total volumetric throughput (3 L/h) depends on the pump, but actual process throughput varies based on cell size and acoustic contrast factor. So total volumetric throughput is a physical limit rather than a processing limit.

What total volume can be processed? That also depends on cell size and volume: Larger volumes generally take longer to process. There’s no true maximum limit of volume for the system; it just depends on how long the process runs. As a general rule, we can process 1–2 L of a single-cell suspension in 60–90 minutes. Larger volumes can take hours.

Does the system differentiate which cells are collected? The acoustics can be tuned to grab cells with a specific acoustic response, generally based on size. By tuning the acoustic power, you can control the amount of time that cells and cell clusters will sit within the acoustics until they drop out.

Have you tried isolating peripheral blood mononuclear cell (PBMCs) from whole blood? We have processed an apheresis product by grabbing PBMCs and washing out the cryoprotectant from thawed frozen cells and also washed it in to freeze apheresis products. Those recoveries are part of a codevelopment with a partner.

Can we add a freezing solution after washing? Yes. In a number of studies we have mixed in cyroprotectant after a wash and concentration step.

The full presentation of this webcast can be found on the BioProcess International website at the link below. Contact Kevin Lannon ([email protected]) or visit www.fdsonics.com. ekko is a registered trademark of FloDesign Sonics.

Find the full webinar online at www.bioprocessintl.com/category/webinars.

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