Manuchehrabadi N, Gao Z, Zhang J, Ring HL, Shao Q, Liu F, McDermott M, Fok A, Rabin Y, Brockbank KG, Garwood M, Haynes CL, Bischof JC. Improved tissue cryopreservation using inductive heating of magnetic nanoparticles. Sci Transl Med. 2017 Mar 1;9(379). pii: eaah4586. doi: 10.1126/scitranslmed.aah4586. PubMed PMID: 28251904.
Cryopreservation has been around for ages, but while it is effective for very small tissue samples such as sperm and ova, scientists have mostly come up dry in attempting cryopreservation of entire organs. The problem is that unless rewarming occurs exactly right, ice crystals destroy everything. One part of “exactly right” is that the rewarming must be uniform, with the avoidance of “hot spots.” In the present study, the authors infused tissue test samples of porcine heart valves and carotid blood vessels with a cryoprotectant (VS55) mixed with silicon-coated iron oxide nanoparticles and cooled everything with liquid nitrogen. To achieve uniform thawing, the tissue was subsequently placed inside a special electromagnetic coil producing an alternating magnetic field that heated up the tissue rapidly and uniformly as a result of the electromagnetic effect (“eddy current heating”) on the nanoparticles. After thawing and a nanoparticle washout process, studies of the thawed tissue showed no signs of damage. Noted the authors: “The nanowarmed artery smooth muscle cells in the media showed well-defined normal nuclear morphology and structure. In contrast, the [control sample] slowly warmed devitrified tissues appeared disrupted, presumably by ice crystals, with shrunken nuclei and condensed chromatin, presumably due to osmotic dehydration during extracellular ice formation.”
While the implications of this development for organ transplantation are obviously significant, the authors emphasize that much more work needs to be done before the procedure becomes part of routine transplant protocols, noting that in future studies nanowarming might “be applied to larger tissues and organs up to volumes of 1 liter and possibly beyond” but that “these larger volumes will require introduction of the nanoparticles directly into the tissue by perfusion to distribute the heat generation sufficiently."
Cryopreservation has been around for ages, but while it is effective for very small tissue samples such as sperm and ova, scientists have mostly come up dry in attempting cryopreservation of entire organs. The problem is that unless rewarming occurs exactly right, ice crystals destroy everything. One part of “exactly right” is that the rewarming must be uniform, with the avoidance of “hot spots.” In the present study, the authors infused tissue test samples of porcine heart valves and carotid blood vessels with a cryoprotectant (VS55) mixed with silicon-coated iron oxide nanoparticles and cooled everything with liquid nitrogen. To achieve uniform thawing, the tissue was subsequently placed inside a special electromagnetic coil producing an alternating magnetic field that heated up the tissue rapidly and uniformly as a result of the electromagnetic effect (“eddy current heating”) on the nanoparticles. After thawing and a nanoparticle washout process, studies of the thawed tissue showed no signs of damage. Noted the authors: “The nanowarmed artery smooth muscle cells in the media showed well-defined normal nuclear morphology and structure. In contrast, the [control sample] slowly warmed devitrified tissues appeared disrupted, presumably by ice crystals, with shrunken nuclei and condensed chromatin, presumably due to osmotic dehydration during extracellular ice formation.”
While the implications of this development for organ transplantation are obviously significant, the authors emphasize that much more work needs to be done before the procedure becomes part of routine transplant protocols, noting that in future studies nanowarming might “be applied to larger tissues and organs up to volumes of 1 liter and possibly beyond” but that “these larger volumes will require introduction of the nanoparticles directly into the tissue by perfusion to distribute the heat generation sufficiently."