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Title:
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27 MHz constant field dielectric warming of kidneys cryopreserved by vitrification
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Author: |
B.G. Wowk, J. Phan, R. Pagotan, E. Galvez, G.M. Fahy
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Citation: |
Cryobiology 115 (2024) 104893 (doi.org/10.1016/j.cryobiol.2024.104893)
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Abstract: |
Organs cryopreserved by vitrification are exposed to the lowest possible concentration of cryoprotectants for the
least time necessary to successfully avoid ice formation. Faster cooling and warming rates enable lower concentrations
and perfusion times, reducing toxicity. Since warming rates necessary to avoid ice formation during
recovery from vitrification are typically faster than cooling rates necessary for vitrification, warming speed is a
major determining factor for successful vitrification. Dielectric warming uses an oscillating electric field to
directly heat water and cryoprotectant molecules inside organs to achieve warming that’s faster and more
uniform than can be achieved by heat conduction from the organ surface. This work studied 27 MHz dielectric
warming of rabbit kidneys perfused with M22 vitrification solution. The 27 MHz frequency was chosen because
its long wavelength and penetration depth are suitable for human organs, because it had an anticipated favorable
temperature of maximum dielectric absorption in M22, and because it’s an allocated frequency for industrial and
amateur use with inexpensive amplifiers available. Previously vitrified kidneys were warmed from .. 100 .C by
placement in a 27 MHz electric field formed between parallel capacitor plates in a resonant circuit. Power was
varied during warming to maintain constant electric field amplitude between the plates. Maximum power absorption
occurred near .. 70 .C, with a peak warming rate near 150 .C/min in 50 mL total volume with
approximately 500 W power. After some optimization, it was possible to warm ~13 g vitrified kidneys with
unprecedentedly little injury from medullary ice formation and a favorable serum creatinine trend after transplant.
Distinct behaviors of power absorption and system tuning observed as a function of temperature during
warming are promising for non-invasive thermometry and future automated control of the warming process at
even faster rates with user-defined temperature dependence.
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Article Link |
https://doi.org/10.1016/j.cryobiol.2024.104893
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