Pressure in isochoric systems containing aqueous solutions at subzero Centigrade temperatures

Abstract

ObjectivePreservation of biological materials at subzero Centigrade temperatures, cryopreservation, is important for the field of tissue engineering and organ transplantation. Our group is studying the use of isochoric (constant volume) systems of aqueous solution for cryopreservation. Previous studies measured the pressure-temperature relations in aqueous isochoric systems in the temperature range from 0°C to – 20°C. The goal of this study is to expand the pressure-temperature measurement beyond the range reported in previous publications.Materials and methodsTo expand the pressure-temperature measurements beyond the previous range, we have developed a new isochoric device capable of withstanding liquid nitrogen temperatures and pressures of up to 413 MPa. The device is instrumented with a pressure transducer than can monitor and record the pressures in the isochoric chamber in real time. Measurements were made in a temperature range from – 5°C to liquid nitrogen temperatures for various solutions of pure water and Me2SO (a chemical additive used for protection of biological materials in a frozen state and for vitrification (glass formation) of biological matter). Undissolved gaseous are is carefully removed from the system.ResultsTemperature-pressure data from – 5°C to liquid nitrogen temperature for pure water and other solutions are presented in this study. Following are examples of some, temperature-pressure values, that were measured in an isochoric system containing pure water: (- 20°C, 187 MPa); (-25°C, 216 MPa); (- 30°C, 242.3 MPa); (-180°C, 124 MPa). The data is consistent with the literature, which reports that the pressure and temperature at the triple point, between ice I, ice III and water is, - 21.993°C and 209.9 MPa, respectively. It was surprising to find that the pressure in the isochoric system increases at temperatures below the triple point and remains high to liquid nitrogen temperatures. Measurements of pressure-temperature relations in solutions of pure water and Me2SO in different concentrations show that, for concentrations in which vitrification is predicted, no increase in pressure was measured during rapid cooling to liquid nitrogen temperatures. However, ice formation either during cooling or warming to and from liquid nitrogen temperatures produced an increase in pressure.ConclusionsThe data obtained in this study can be used to aid in the design of isochoric cryopreservation protocols. The results suggest that the pressure measurement is important in the design of “constant volume” systems and can provide a simple means to gain information on the occurrence of vitrification and devitrification during cryopreservation processes of aqueous solutions in an isochoric system.

Thermo-mechanics aspects of isochoric cryopreservation: A new modeling approach and comparison with experimental data

“… Phase diagram of water in temperature and pressure ranges relevant to the current study, as compiled from [ 11 ]. Also displayed are experimental results reported in the literature [ 12 ] and modeling results developed in the current study for similar conditions. …”

“…The proposed modeling approach is first validated in equilibrium conditions against classical literature data on pure water [ 11 ]. The proposed model is then compared with experimental results reported in the literature [ 12 ]. Finally, this study is used to provide insight into isochoric cooling and rewarming of pure water in a practical three-dimensional (3D) container.…”

“…Two isochoric chambers are analyzed in this study ( Fig 2 ): (A) an isochoric chamber used in a previous experimental investigation [ 12 ] as a benchmark, and (B) an idealized cylindrical container of variable dimensions to explore case studies.…”

New Approaches to Cryopreservation of Cells, Tissues, and Organs

“…Particularly significant is the theoretical work by Szobota and Rubinsky [158], who showed that the probability for random ice nucleation decreases in an isochoric system; therefore, they predicted that the probability for vitrification will be enhanced in an isochoric system. Additionally, Ukpai et al [171] reported the thermodynamic profiles of solutions of Me 2 SO in pure water during cooling to and warming from cryogenic temperatures in an isochoric system. Subsequently, together with Rubinsky’s group, we showed that pressure measurement is important for designing and control of cryopreservation protocols in constant-volume (isochoric) systems and confirmed that any ice formation is associated with an increase in pressure, and that therefore pressure can be used as a measure for the occurrence of vitrification.…”

“…Subsequently, together with Rubinsky’s group, we showed that pressure measurement is important for designing and control of cryopreservation protocols in constant-volume (isochoric) systems and confirmed that any ice formation is associated with an increase in pressure, and that therefore pressure can be used as a measure for the occurrence of vitrification. However, when ice is not formed, the pressure in the isochoric system does not increase during cooling, and in systems that vitrify, the absence of a pressure increase can confirm vitrification, observed pressure increases during a vitrification protocol can indicate devitrification, and temporal or static pressure measurements can be used as an objective substitute for or adjunct to more subjective visual inspection methods [28, 171, 172]. A comparison with results from the literature shows that the concentration of CPAs needed for vitrification in an isochoric chamber is substantially lower than that needed for vitrification in isobaric systems at 1 atm and in hyperbaric systems at 1,000 atm.…”