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Published June 2016 | Published + Supplemental Material
Journal Article Open

A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation


An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe_3O_4, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10–100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments.

Additional Information

© 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Received 13 January 2016; Received in revised form 5 April 2016; Accepted 10 April 2016; Available online 14 April 2016. This study was supported by: (1) JSPS KAKENHI Grant Number JP26630062 from the Japan Society for the Promotion of Science, in the category "Challenging Exploratory Research 2014" to AK and HNG, (2) discretionary funds from Caltech to JLK; funding agencies did not influence the results of this work, and the authors have no conflict of interests. We thank Prof. Hideo Tsunakawa of the Tokyo Institute of Technology for the use of the Alternating-field demagnetization unit.

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