A better way to freeze stem cells and tissue

Posted on Tuesday, January 12, 2021

Ice crystals as seen through a microscope; small ice crystals on the left, and larger ice crystals on the right.

Image showing the growth of ice crystals on a microscopic scale.

They say the best technological innovations are inspired by nature, and for Dr. Robert Ben, a professor in the Department of Chemistry at uOttawa, this holds true. He and his colleague, Dr. Jason Acker at the University of Alberta, are in the process of commercializing a new, improved method for freezing stem cells and tissue samples. Ben says the idea “crystallized” after reading about teleost fish, a species that can survive in sub-zero environments because their bodies use anti-freeze proteins to inhibit the growth of ice crystals.

Ben and Acker’s company, PanTHERA CryoSolutions, manufactures ice recrystallization inhibitors, which are small organic molecules that halt ice growth in order to better preserve biological material used in the fields of cell therapy and regenerative medicine.

The company recently secured a $4 million investment from BioLife Solutions Inc. and Casdin Capital to support product development over the next 24 months, in exchange for exclusive, worldwide marketing and distribution rights to the technology for use in cell and gene therapy applications.

“We have been freezing cells and tissues for some time now, in order to develop cell therapies to treat a wide range of diseases,” says Ben, who specializes in synthetic organic and medicinal chemistry. “And we’ve been using cryoprotective agents, such as dimethyl sulfoxide or glycerol, since the 1950s to try to prevent the cells from dying in the freezing and thawing process. The problem with current cryoprotectants is that cell recovery is kind of hit and miss. We might freeze 100,000 cells, but only 25,000 will survive and be viable for research or clinical applications. That’s because up to 80 percent of the cellular damage that happens during freezing is due to the uncontrolled growth of ice. Since current cryoprotectant solutions don’t address this problem, our returns, measured in cell recovery and function, are quite dismal.”

Another benefit of their technology is that cells, tissue, organs — and potentially vaccines and other biological materials — can be kept at warmer temperatures, making it easier to store these products and ship them to remote locations.

Over the past 10 months, Ben has also been developing a new class of recrystallization inhibitors that protect and stabilize proteins, nucleotides and viruses. He and his collaborators are in the proof-of-concept phase of demonstrating that the technology can preserve COVID testing materials and RNA-based vaccines.

Researchers Jason Acker, left, and Robert Ben, right, posing in a lab

Dr. Jason Acker (left), Faculty of Medicine and Dentistry at the University of Alberta / Canadian Blood Services, and Dr. Robert Ben, Faculty of Science at the University of Ottawa. Photo credit: GlycoNet, one of the original funders of this research.

Understanding the effects of ice growth

Ice growth, or the process of ice recrystallization, is an inevitable side-effect of freezing something. Over time, and with temperature fluctuations, ice crystals become larger and larger and cause a lot of disruption in cell membranes, which in turn damages or kills the cells.

“Think of freezer burn,” says Ben. “If you’ve ever tasted ice cream after it’s been sitting in your freezer for a while — I’m sure we all have — the product looks and tastes different from when it was brand new. That’s because those ice crystals are changing the structure of that material, and along with that goes taste and everything else.”

Ben explains that the lower the temperature, the slower the recrystallization process. That’s why some therapies such as vaccines need to be stored at very cold temperatures so they can be preserved for longer. For example, the Pfizer COVID-19 vaccine must be kept at -70 degrees Celsius to keep the ice crystals from growing too large and damaging the product.

“Small ice crystals are innocuous,” he says. “They’re like grains of sand on a Caribbean beach. They’re so small that they mould to your body and you can lay comfortably on the beach for an entire day. Now, let’s say those grains of sand were replaced by gravel or pebbles. That’s a lot less comfortable. Our cryopreservation technology prevents ice crystals from growing too large for comfort.”

With modern cell therapies and regenerative medicine techniques on the rise, it has become necessary to update the way we preserve the materials that make such medical advances possible.

“Our molecules are unique because, unlike conventional cryoprotectants, they prevent all that cellular damage caused by ice. In the end, we recover more cells, they’re healthier and more functional. There is nothing else like it out there.”

The core technology was created out of an academic research collaboration between the University of Ottawa and University of Alberta that has received research funding from GlycoNet, one of the National Centres of Excellence (NCE) in Canada; Canadian Institutes of Health Research (CIHR); Natural Sciences and Engineering Research Council (NSERC) of Canada; Canadian Blood Services; the National Research Council of Canada Industrial Research Assistance Program (IRAP); and Mitacs.

Back to top