Cooling dynamics of droplets exposed to solid surface freezing and vitrification

verfasst von: Dejia Liu, Harriëtte Oldenhof, Xing Luo, Tobias Braun, Harald Sieme, Willem F. Wolkers
Abstract: Solid surface freezing or vitrification (SSF/SSV) can be done by depositing droplets of a sample, e.g., cells in a preservation solution, onto a pre-cooled metal surface. It is used to achieve higher cooling rates and concomitant higher cryosurvival rates compared to immersion of samples into liquid nitrogen. In this study, numerical simulations of SSF/SSV were conducted by modeling the cooling dynamics of droplets of cryoprotective agent (CPA) solutions. It was assumed that deposited droplets attain a cylindrical bottom part and half-ellipsoidal shaped upper part. Material properties for heat transfer simulations including density, heat capacity and thermal conductivity were obtained from the literature and extrapolated using polynomial fitting. The impact of CPA type, i.e., glycerol (GLY) and dimethyl sulfoxide (DMSO), CPA concentration, and droplet size on the cooling dynamics was simulated at different CPA mass fractions at temperatures ranging from −196 to 25 °C. Simulations show that glycerol solutions cool faster compared to DMSO solutions, and cooling rates increase with decreasing CPA concentration. However, we note that material property data for GLY and DMSO solutions were obtained in different temperature and concentration ranges under different conditions, which complicated making an accurate comparison. Experimental studies show that samples that freeze have a delayed cooling response early on, whereas equilibration times are similar compared to samples that vitrify. Finally, as proof of concept, droplets of human red blood cells (RBCs) were cryopreserved using SSV/SSF comparing the effect of GLY and DMSO on cryopreservation outcome. At 20% (w/w), similar hemolysis rates were found for GLY and DMSO, whereas at 40%, GLY outperformed DMSO.
Organisationseinheit(en): Institut für Thermodynamik
Institut für Mehrphasenprozesse
Externe Organisation(en): NIFE- Niedersächsisches Zentrum für Biomedizintechnik, Implantatforschung und Entwicklung
Stiftung Tierärztliche Hochschule Hannover
Typ: Artikel
Journal: CRYOBIOLOGY
Band: 115
Anzahl der Seiten: 12
ISSN: 0011-2240
Publikationsdatum: 06.2024
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Allgemeine Biochemie, Genetik und Molekularbiologie, Allgemeine Agrar- und Biowissenschaften
Elektronische Version(en): https://doi.org/10.1016/j.cryobiol.2024.104879 (Zugang: Offen)

BibTeX

@article{9a8fa3ac8c42442e9ed334a83c467ec9,
title = "Cooling dynamics of droplets exposed to solid surface freezing and vitrification",
abstract = "Solid surface freezing or vitrification (SSF/SSV) can be done by depositing droplets of a sample, e.g., cells in a preservation solution, onto a pre-cooled metal surface. It is used to achieve higher cooling rates and concomitant higher cryosurvival rates compared to immersion of samples into liquid nitrogen. In this study, numerical simulations of SSF/SSV were conducted by modeling the cooling dynamics of droplets of cryoprotective agent (CPA) solutions. It was assumed that deposited droplets attain a cylindrical bottom part and half-ellipsoidal shaped upper part. Material properties for heat transfer simulations including density, heat capacity and thermal conductivity were obtained from the literature and extrapolated using polynomial fitting. The impact of CPA type, i.e., glycerol (GLY) and dimethyl sulfoxide (DMSO), CPA concentration, and droplet size on the cooling dynamics was simulated at different CPA mass fractions at temperatures ranging from −196 to 25 °C. Simulations show that glycerol solutions cool faster compared to DMSO solutions, and cooling rates increase with decreasing CPA concentration. However, we note that material property data for GLY and DMSO solutions were obtained in different temperature and concentration ranges under different conditions, which complicated making an accurate comparison. Experimental studies show that samples that freeze have a delayed cooling response early on, whereas equilibration times are similar compared to samples that vitrify. Finally, as proof of concept, droplets of human red blood cells (RBCs) were cryopreserved using SSV/SSF comparing the effect of GLY and DMSO on cryopreservation outcome. At 20% (w/w), similar hemolysis rates were found for GLY and DMSO, whereas at 40%, GLY outperformed DMSO.",
keywords = "Cryopreservation, Droplet generation, Numerical simulation, Red blood cells, Solid surface vitrification/freezing, Vitrification",
author = "Dejia Liu and Harri{\"e}tte Oldenhof and Xing Luo and Tobias Braun and Harald Sieme and Wolkers, {Willem F.}",
note = "Funding Information: The work described in this study was financially supported via grant WO1735/6–2 and SI1462/4–2 of the German Research Foundation (DFG: Deutsche Forschungsgemeinschaft), and HEMOFORCE (E/U2ED/MD010/LF551, Deutsche Bundeswehr). We kindly acknowledge the Institute for Transfusion Medicine (Hannover Medical School) for providing blood samples. ",
year = "2024",
month = jun,
doi = "10.1016/j.cryobiol.2024.104879",
language = "English",
volume = "115",
journal = "CRYOBIOLOGY",
issn = "0011-2240",
publisher = "Academic Press Inc.",
}