New magnetic nanoparticles can safely rewarm tissues for transplants

In organ transplantation, time is of the utmost importance as organs’ quality degrades rapidly during transportation.

Researchers at the University of California, Riverside, have developed a new technique that could extend the lifespan of human tissues for transplantation.

They call this technique nanowarming, which uses magnetic nanoparticles to rewarm the tissues.

Nanowarming using magnetic nanoparticles

Prior to transplantation, the organ is extracted from the donor and must be stored in an extremely cold environment for transportation. This low temperature decreases metabolic activity and lowers the organ’s oxygen demand.

However, the existing procedures aren’t fully safe for organs. One difficulty is organ damage caused by premature warming during transportation.

While methods have been developed to rapidly freeze organs without the risk of ice crystal formation, ice crystals can still form during the thawing process.

In this new development, the researchers have developed a method to rapidly and evenly thaw frozen tissues. This technique may reduce the risk of damage caused by ice crystal formation.

Nanowarming uses magnetic nanoparticles and magnetic fields to thaw frozen tissues.

“Magnetic nanoparticles with extremely small size and high dispersity are co-loaded into tissue with cryoprotective agents (CPAs). In contrast to traditional convective heating from external regions of tissue, nanowarming is achieved through the nanoparticle’s heat generation from the internal space of tissue, realizing much more uniform and faster heating,” Yadong Yin, who led this study, told Interesting Engineering (IE).

Two-stage nanowarming technique

As per the press release , the team created magnetic nanoparticles like tiny bar magnets.

During the testing, the cultured cells or animal tissues were put in a solution of magnetic nanoparticles and a cryoprotectant, followed by freezing with liquid nitrogen.

These nanoparticles generated heat when exposed to alternating magnetic fields. Interestingly, this heat quickly thawed animal tissues preserved at -238 degrees Fahrenheit (-150 degrees Celsius).

“Specifically, heat generation is induced by hysteresis loss, in which the magnetic energy of an external alternating magnetic field is transformed into heat in magnetic nanoparticles. Enhanced heating rate and uniformity can prevent the phase change of CPAs so that water molecules would not have enough time to pack together and form damaging ice crystals,” Yin explained.

Particularly, the researchers developed a two-stage nanowarming technique to safely and evenly thaw frozen tissues. In the first stage, an alternating magnetic field rapidly heats the tissue. In the second stage, a static magnetic field is applied to slow down the heating process in areas with higher nanoparticle concentrations.

“There are still many obstacles before nanowarming can be used for organ cryopreservation. Before practical applications in organ transplantation , we must ensure the nanorods can be easily introduced into and removed from organs,” Yin noted.

Moreover, the team aims to decrease the size of nanorods while preserving their high aspect ratios.

By using magnetic nanoparticles, experts can precisely control the rate of thawing, minimizing the risk of tissue damage. The precise control of tissue rewarming may help in long-term organ cryopreservation.

The findings were reported in the journal Nano Letters.