Fall 2019

Freezing time for organ transplantation

What if it were possible to stop time, biologically speaking, to keep living donor organs undamaged for longer?

Every day in the United States, fewer than 100 people receive organ transplants while more than 100,000 others continue to wait for the donor organs that could save their lives.

The discrepancy between organ need and availability stems from a simple yet formidable foe: time.

But what if it were possible to stop time, biologically speaking? Scientists at the University of Minnesota think it’s feasible through cryopreservation, a type of super-cold storage that keeps living organs undamaged longer.

Today when a donor organ becomes available, doctors preserve it in an ice-filled cooler at 39° F and quickly work to deliver it to a patient in need. They have only a matter of hours to find a matching recipient, transport the organ, and perform transplant surgery before the organ becomes unusable. Inevitably, many healthy organs are lost in this race against the clock.

Now the U’s John Bischof, Ph.D., holder of the Medtronic-Bakken Endowed Chair for Engineering in Medicine and Carl and Janet Kuhrmeyer Chair in Mechanical Engineering, and M Health Fairview transplant surgeon Erik Finger, M.D., Ph.D., lead a team that has successfully cryopreserved small animal tissues. 

Bischof says the technique was invented to be scalable and could be used to store human hearts, kidneys, lungs, and other organs in the future—thereby exponentially extending the amount of time donor organs are viable.

“Ultimately, thousands—even millions—of lives could be saved or improved,” he says.

Here’s how the process could work:



STEP 1 Preservation preparation
Engineers and clinicians immerse a donor organ or tissue in a solution of biocompatible antifreeze with added magnetic iron oxide nanoparticles.


STEP 2 Deep freeze
The donor organ or tissue, a liver in this scenario, is removed from the solution and cooled to below -140°C (about -220°F).


STEP 3 Long rest
These cryopreserved organs or tissues can be stored for extended periods—months, maybe years.


STEP 4 Wake-up call
When the organ or tissue is needed for a transplant, it’s zapped with high-energy radio fields, which pass harmlessly through the organ or tissue but energize the nanoparticles.


STEP 5 Rapid reheat
The energized nanoparticles act as miniature heaters, quickly and evenly rewarming the organ or tissue. Previous techniques led to uneven or sluggish warming that would cause ice to form and tissue to crack, like an ice cube fracturing when dropped in a cup of warm water, making the organ unusable.


STEP 6 Ready to roll
Once the organ or tissue is rewarmed, the nanoparticles are washed from the tissue.


STEP 7 Lifesaver
Doctors use the organ or tissue in a transplant surgery.