Glass-forming property of the system diethyl sulphoxide/water and its cryoprotective action on Escherichia coli survival

• Published in: Cryobiology Vol. 49; no. 1; pp. 1 - 9
• Main Authors: Markarian, Shiraz A, Bonora, Sergio, Bagramyan, Karine A, Arakelyan, Valery B
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.08.2004
• Subjects: Calorimetry, Differential Scanning; Cryopreservation; Cryoprotective Agents - pharmacology; Diethyl sulphoxide; Differential scanning calorimetry; Dimethyl Sulfoxide - pharmacology; Escherichia coli; Escherichia coli - cytology; Escherichia coli - drug effects; Escherichia coli survival; Freezing; Glass; Glass-forming tendency; Sulfoxides - pharmacology; Thermodynamics; Water; Differential scanning calorimetry; Glass-forming tendency; Escherichia coli survival; Cryopreservation; Diethyl sulphoxide
• ISSN: 0011-2240; 1090-2392
• DOI: 10.1016/j.cryobiol.2004.04.001

In this work the thermal properties of diethyl sulphoxide (Et 2SO), as well as its cryoprotective ability are studied and related to other well-known cryoprotectant substances, like dimethyl sulphoxide (Me 2SO). We have investigated the thermal properties of Et 2SO/water systems using Differential Scanning Calorimetry at a very low heating/cooling rate (2 °C/min). Liquid/solid or glassy/crystalline transitions have been observed only for the solutions with content of Et 2SO ranging from 5 up to 40% w/w and/or greater than 85%. In the 45–75% w/w Et 2SO range we have found a noticeable glass-forming tendency and a great stability of the amorphous state to the reheating. In samples with Et 2SO content ranging from 80 to 85%, we observed a great stability of the glass forming by cooling, but a lesser stability to the subsequent reheating. The glass-forming tendency of these solutions is discussed in terms of existing competitive interactions between molecules of Et 2SO, on the one hand, and Et 2SO and water molecules, on the other hand. The results are well explainable on the basis of the model structure of water/Et 2SO solutions, deduced by Raman and infrared studies [J. Mol. Struct. 665 (2003) 285–292]. The cryoprotective ability of Et 2SO on Escherichia coli survival has been also investigated, and a comparison among Et 2SO and other widely used cryoprotectants, like Me 2SO and glycerol has been done. Survival of E. coli, determined after freezing–thawing process, was maximal at 45% w/w Et 2SO (more than 85% viability). It should be noted that at the same concentration the survival is only about 35% in the presence of Me 2SO and not more than 15% in the presence of glycerol. These features are well consisted with the glass-forming properties of Et 2SO.