Cryoprotection of red blood cells by 1,3-butanediol and 2,3-butanediol

Observing ice structure of micron-sized vapor-deposited ice with an x-ray free-electron laser

The direct observation of the structure of micrometer-sized vapor-deposited ice is performed at Pohang Accelerator Laboratory x-ray free electron laser (PAL-XFEL). The formation of micrometer-sized ice crystals and their structure is important in various fields, including atmospheric science, cryobiology, and astrophysics, but understanding the structure of micrometer-sized ice crystals remains challenging due to the lack of direct observation. Using intense x-ray diffraction from PAL-XFEL, we could observe the structure of micrometer-sized vapor-deposited ice below 150 K with a thickness of 2-50 μm grown in an ultrahigh vacuum chamber. The structure of the ice grown comprises cubic and hexagonal sequences that are randomly arranged to produce a stacking-disordered ice. We observed that ice with a high cubicity of more than 80% was transformed to partially oriented hexagonal ice when the thickness of the ice deposition grew beyond 5 μm. This suggests that precise temperature control and clean deposition conditions allow μm-thick ice films with high cubicity to be grown on hydrophilic Si3N4 membranes. The low influence of impurities could enable in situ diffraction experiments of ice nucleation and growth from interfacial layers to bulk ice.

Effect of nitrogen molecules on the growth kinetics at the interface between a (111) plane of cubic ice and water

The molecular-scale growth kinetics of ice from water in the presence of air molecules are still poorly understood, despite their importance for understanding ice particle formation in nature. In this study, a molecular dynamics simulation is conducted to elucidate the molecular-scale growth kinetics at the interface between a (111) plane of cubic ice and water in the presence of N2 molecules. Two potential models of N2 molecules with and without atomic charges are examined. For both models, N2 molecules bind stably to the interface for a period of 1 ns or longer, and the stability of the binding is higher for the charged model than for the noncharged model. Free-energy surfaces of an N2 molecule along the interface and along an ideal (111) plane surface of cubic ice suggest that for both models, the position where an N2 molecule binds stably is different at the interface and on the ideal plane surface, and the stability of the binding is much higher for the interface than for the ideal plane surface. For both models, stacking-disordered ice grows at the interface, and the formation probability of a hexagonal ice layer in the stacking-disordered ice is higher for the charged model than for the uncharged model. The formation probability for the hexagonal ice layer in the stacking-disordered ice depends not only on the stability of binding but also on the positions where N2 molecules bind on the underlying ice, and the number of N2 molecules that bind stably to the underlying ice.

Routes to cubic ice through heterogeneous nucleation

The freezing of water into ice is one of the most important processes in the physical sciences. However, it is still not understood at the molecular level. In particular, the crystallization of cubic ice ([Formula: see text])-rather than the traditional hexagonal polytype ([Formula: see text])-has become an increasingly debated topic. Although evidence for [Formula: see text] is thought to date back almost 400 y, it is only in the last year that pure [Formula: see text] has been made in the laboratory, and these processes involved high-pressure ice phases. Since this demonstrates that pure [Formula: see text] can form, the question naturally arises if [Formula: see text] can be made from liquid water. With this in mind, we have performed a high-throughput computational screening study involving molecular dynamics simulations of nucleation on over 1,100 model substrates. From these simulations, we find that 1) many different substrates can promote the formation of pristine [Formula: see text]; 2) [Formula: see text] can be selectively nucleated for even the mildest supercooling; 3) the water contact layer's resemblance to a face of ice is the key factor determining the polytype selectivity and nucleation temperature, independent of which polytype is promoted; and 4) substrate lattice match to ice is not indicative of the polytype obtained. Through this study, we have deepened understanding of the interplay of heterogeneous nucleation and ice I polytypism and suggest routes to [Formula: see text] More broadly, the substrate design methodology presented here combined with the insight gained can be used to understand and control polymorphism and stacking disorder in materials in general.

Principles of Ice-Free Cryopreservation by Vitrification

Vitrification is an alternative to cryopreservation by freezing that enables hydrated living cells to be cooled to cryogenic temperatures in the absence of ice. Vitrification simplifies and frequently improves cryopreservation because it eliminates mechanical injury from ice, eliminates the need to find optimal cooling and warming rates, eliminates the importance of differing optimal cooling and warming rates for cells in mixed cell type populations, eliminates the need to find a frequently imperfect compromise between solution effects injury and intracellular ice formation, and can enable chilling injury to be "outrun" by using rapid cooling without a risk of intracellular ice formation. On the other hand, vitrification requires much higher concentrations of cryoprotectants than cryopreservation by freezing, which introduces greater risks of both osmotic damage and cryoprotectant toxicity. Fortunately, a large number of remedies for the latter problem have been discovered over the past 35 years, and osmotic damage can in most cases be eliminated or adequately controlled by paying careful attention to cryoprotectant introduction and washout techniques. Vitrification therefore has the potential to enable the superior and convenient cryopreservation of a wide range of biological systems (including molecules, cells, tissues, organs, and even some whole organisms), and it is also increasingly recognized as a successful strategy for surviving harsh environmental conditions in nature. But the potential of vitrification is sometimes limited by an insufficient understanding of the complex physical and biological principles involved, and therefore a better understanding may not only help to improve present outcomes but may also point the way to new strategies that may be yet more successful in the future. This chapter accordingly describes the basic principles of vitrification and indicates the broad potential biological relevance of this alternative method of cryopreservation.

Solvation Structure of 1,3-Butanediol in Aqueous Binary Solvents with Acetonitrile, 1,4-Dioxane, and Dimethyl Sulfoxide Studied by IR, NMR, and Molecular Dynamics Simulation

The solvation structure of 1,3-butanediol (1,3-BD) in aqueous binary solvents of acetonitrile (AN), 1,4-dioxane (DIO), and dimethyl sulfoxide (DMSO) at various mole fractions of organic solvent x_OS has been clarified by means of infrared (IR) and ¹H and ¹³C NMR. The change in the wavenumber of O-H stretching vibration of 1,3-BD in the three systems suggested that water molecules which are initially hydrogen-bonded with the 1,3-BD hydroxyl groups in the water solvent (x_OS = 0) are more significantly replaced by organic solvent molecules in the order of DMSO ≫ DIO > AN. This agrees with the order of the electron donicities of the organic solvents. The ¹H and ¹³C chemical shifts of 1,3-BD also revealed the most remarkable replacement of water molecules on the hydroxyl groups by DMSO. In contrast to the DMSO system, the O-H vibration band of 1,3-BD in the AN and DIO systems suggested the formation of the intramolecular hydrogen bond between the two hydroxyl groups of 1,3-BD above x_OS = ∼0.9. To further evaluate the intramolecular hydrogen bonding of 1,3-BD in AN-water binary solvents, molecular dynamics (MD) simulations and NMR experiments for spin-lattice relaxation times T₁ and ¹H-¹H nuclear Overhauser effect (NOE) were conducted on 1,3-BD in the AN system. These results showed the intramolecular hydrogen bond within 1,3-BD in the AN-water binary solvents in the high AN mole fraction range of x_AN > 0.9. Especially, the pair correlation functions g(r) of the OH-O interactions of 1,3-BD obtained from the MD simulations indicated that the intramolecular hydrogen bond remarkably increases in the AN solvent as the x_AN rises to the unity.

Cryoprotectant Toxicity: Facts, Issues, and Questions

High levels of penetrating cryoprotectants (CPAs) can eliminate ice formation during cryopreservation of cells, tissues, and organs to cryogenic temperatures. But CPAs become increasingly toxic as concentration increases. Many strategies have been attempted to overcome the problem of eliminating ice while minimizing toxicity, such as attempting to optimize cooling and warming rates, or attempting to optimize time of adding individual CPAs during cooling. Because strategies currently used are not adequate, CPA toxicity remains the greatest obstacle to cryopreservation. CPA toxicity stands in the way of cryogenic cryopreservation of human organs, a procedure that has the potential to save many lives. This review attempts to describe what is known about CPA toxicity, theories of CPA toxicity, and strategies to reduce CPA toxicity. Critical analysis and suggestions are also included.

Structure of ice crystallized from supercooled water

The freezing of water to ice is fundamentally important to fields as diverse as cloud formation to cryopreservation. At ambient conditions, ice is considered to exist in two crystalline forms: stable hexagonal ice and metastable cubic ice. Using X-ray diffraction data and Monte Carlo simulations, we show that ice that crystallizes homogeneously from supercooled water is neither of these phases. The resulting ice is disordered in one dimension and therefore possesses neither cubic nor hexagonal symmetry and is instead composed of randomly stacked layers of cubic and hexagonal sequences. We refer to this ice as stacking-disordered ice I. Stacking disorder and stacking faults have been reported earlier for metastable ice I, but only for ice crystallizing in mesopores and in samples recrystallized from high-pressure ice phases rather than in water droplets. Review of the literature reveals that almost all ice that has been identified as cubic ice in previous diffraction studies and generated in a variety of ways was most likely stacking-disordered ice I with varying degrees of stacking disorder. These findings highlight the need to reevaluate the physical and thermodynamic properties of this metastable ice as a function of the nature and extent of stacking disorder using well-characterized samples.

Conformational cooling dynamics in matrix-isolated 1,3-butanediol

The complete conformational space of monomeric 1,3-butanediol has been characterized theoretically, and 73 unique stable conformers were found at the MP2/6-311++G(d,p) level. These were classified into nine families whose members share the same heavy atom backbone configurations and differ in the hydrogen atom orientations. The first and third most populated backbone families are governed by the formation of an intramolecular hydrogen bond; however, the second precludes this type of interaction and was frequently overlooked in previous studies. Its stability is determined by the relatively high entropy of its main conformers. The hydrogen bonding of four of the most important conformers was characterized by means of atoms in molecules (AIM, also known as QTAIM) and natural bond orbital (NBO) analyses. Using appropriate isodesmic reactions, hydrogen bonding energy stabilizations of 12-14 kJ mol(-1) have been found. Experimentally, monomeric molecules of 1,3-butanediol were isolated in low-temperature inert matrixes, and their infrared spectra were analyzed from the viewpoint of the conformational distribution. All the relevant transition states for the conformational interconversion reaction paths were characterized at the same level of theory to interpret the conformational cooling dynamics observed in the low-temperature matrixes. The energy barriers for rotation of the OH groups were calculated to be very low (<3 kJ mol(-1)). These barriers were overcome in the experiments at 10 K (Ar matrix), in the process of matrix deposition, and population within each family was reduced to the most stable conformers. Further increase in the substrate temperature (up to 40 K, Xe matrix) resulted in conformational cooling where the medium-height barriers (approximately 13 kJ mol(-1)) could be surmounted and all conformational population converted to the ground conformational state. Remarkably, this state turned to consist of two forms of the most stable hydrogen bonded family, which were predicted by calculations to be accidentally degenerated and were found in the annealed matrix in equal amounts. All of these experimentally observed conformational cooling processes were analyzed and supported by full agreement with the theoretical calculations.

Numerical investigations of transient heat transfer characteristics and vitrification tendencies in ultra-fast cell cooling processes

During freezing, cells are often damaged directly or indirectly by ice formation. Vitrification is an alternative approach to cryopreservation that avoids ice formation. The common method to achieve vitrification is to use relatively high concentrations of cryoprotectant agents (CPA) in combination with a relatively slow cooling rate. However, high concentrations of CPAs have potentially damaging toxic and/or osmotic effects on cells. Therefore, establishing methods to achieve vitrification with lower concentrations of CPAs through ultra-fast cooling rates would be advantageous in these aspects. These ultra-fast cooling rates can be realized by a cooling system with an ultra-high heat transfer coefficient (h) between the sample and coolant. The oscillating motion heat pipe (OHP), a novel cooling device utilizing the pressure change to excite the oscillation motion of the liquid plugs and vapor bubbles, can significantly increase h and may fulfill this aim. The current investigation was designed to numerically study the effects of different values of h on the transient heat transfer characteristics and vitrification tendencies of the cell suspension during the cooling processes in an ultra-thin straw (100 microm in diameter). The transient temperature distribution, the cooling rate and the volume ratio (x) of the ice quantity to the maximum crystallizable ice of the suspension were calculated. From these numerical results, it is concluded that the ultra-high h (>10(4) W/m2 K) obtained by OHPs could facilitate vitrification by efficiently decreasing x as well as the time to pass through the dangerous temperature region where the maximum ice formation happens. For comparison, OHPs can decrease both of the parameters to less than 20% of those from the widely used open pulled straw methods. Therefore, the OHP method will be a promising approach to improving vitrification tendencies of CPA solutions and could also decrease the required concentration of CPAs for vitrification, both of which are of great importance for the successful cryopreservation of cells by vitrification.

Thermal properties of ethylene glycol aqueous solutions

Preventing ice crystallization by transforming liquids into an amorphous state, vitrification can be considered as the most suitable technique allowing complex tissues, and organs cryopreservation. This process requires the use of rapid cooling rates in the presence of cryoprotective solutions highly concentrated in antifreeze compounds, such as polyalcohols. Many of them have already been intensively studied. Their glass forming tendency and the stability of their amorphous state would make vitrification a reality if their biological toxicity did not reduce their usable concentrations often below the concentrations necessary to vitrify organs under achievable thermal conditions. Fortunately, it has been shown that mixtures of cryoprotectants tend to reduce the global toxicity of cryoprotective solutions and various efficient combinations have been proposed containing ethanediol. This work reports on the thermal properties of aqueous solutions with 40, 43, 45, 48, and 50% (w/w) of this compound measured by differential scanning calorimetry. The glass forming tendency and the stability of the amorphous state are evaluated as a function of concentration. They are given by the critical cooling rates v(ccr)above which ice crystallization is avoided, and the critical warming rates v(cwr) necessary to prevent ice crystallization in the supercooled liquid state during rewarming. Those critical rates are calculated using the same semi-empirical model as previously. This work shows a strong decrease of averaged critical cooling and warming rates when ethanediol concentration increases, V(ccr) and V(cwr) = 1.08 x 10 (10) K/min for 40% (w/w) whereas V(ccr) = 11 and V(cwr) = 853 K/min for 50% (w/w). Those results are compared with the corresponding properties of other dialcohols obtained by the same method. Ethylene glycol efficiency is between those of 1,2-propanediol and 1,3-propanediol.

Effects of vitrification medium composition on the survival of bovine in vitro produced embryos, following in straw-dilution, in vitro and in vivo following transfer

This study examined the effects of adding a macromolecule, polyvinylpyrrolidone (10% PVP) and a sugar (0.3 M trehalose) to vitrification solutions (VS) containing either one (40% ethylene glycol [EG], two (25% EG+25% DMSO) or three (20% EG+20% DMSO+10% 1, 3-butanediol [BD]) permeable cryoprotectants on the survival and hatching of IVP bovine embryos, following vitrification, warming and in-straw cryoprotectant dilution. Grade 1 and 2 compact morulae and blastocysts were selected on Day 7 (Day 0=IVF) of culture in SOFaaBSA and equilibrated for 10 min at room temperature in 10% EG. Following exposure, for up to 1 min at 4 degrees C, to one of the above VS (with or without PVP+trehalose), the embryos were loaded into straws and immersed in liquid nitrogen. Following warming and in-straw cryoprotectant dilution, the embryos were cultured for 48 h to assess hatching. There was no effect of VS on the survival of embryos after 24 h, however fewer compact morulae than blastocysts survived after 24 h (24% vs. 75%; P<0.001) or hatched after 48 h (15% vs. 59%; P<0.001). When blastocysts only were considered, an interaction between VS and additional PVP+trehalose was also observed (P<0.01). Hatching was reduced when they were added to 25% EG+25% DMSO (70% vs. 45%) but was not affected for either 40% EG (44 and 49%) or to 20% EG+20% DMSO+10% BD (72 and 72%). Pregnancy rates (Day 90 ultrasound) of recipients that were transferred either two non-vitrified or two vitrified (20% EG+20% DMSO+10% BD) blastocysts, did not differ (3/6 [50%] and 11/20 [55%]). However, significantly (P<0.02) fewer recipients that received compact morulae maintained pregnancy to Day 90 although this was not affected by vitrification (fresh vs. vitrified; 1/5 [20%] vs. 3/18 [17]). These data demonstrate that a VS comprising three cryoprotectants, rather than one, enables more embryos to hatch during post-thaw culture and that the survival, following direct transfer of these vitrified embryos, is not different to non-vitrified embryos.

Critical cooling rates for aqueous cryoprotectants in the presence of sugars and polysaccharides

The technique of isothermal emulsion differential scanning calorimetry was used to determine time-temperature-transformation (TTT) curves for aqueous glycerol and butane-2,3-diol in the presence of various polysaccharides and sugars. The critical cooling rate required to avoid the crystallization of ice in these solutions was then calculated from the experimental TTT curves. The polysaccharides used in this study included starch hydrolysis products and dextrans of various molecular weights. The sugars used here were sucrose, glucose, trehalose, and raffinose. The results show that the critical cooling rates of butane-2,3-diol and glycerol are reduced by varying amounts by the addition of such materials but that the reduction is not as great as is achieved by the addition of polyethylene glycol with a molecular weight of 400.

Cryoprotection of red blood cells by a 2,3-butanediol containing mainly the levo and dextro isomers

A 2,3-butanediol containing 96.7% (w/w) racemic mixture of the levo and dextro isomers and only 3.1% (w/w) of the meso isomer (called 2,3-butanediol 97% dl) has been used for the cryoprotection of red blood cells. The erythrocytes were cooled to -196 degrees C at rates between 2 and 3500 degrees C/min, followed by slow or rapid warming. Up to 20% (w/w) of this polyalcohol, only the classical peak of survival is observed, as with up to 20% (w/w) 1,2-propanediol or 1,3-butanediol. Twenty percent 2,3-butanediol 97% dl can protect red blood cells very efficiently. The maximum survival, of 90%, as with 20% glycerol, is a little lower than with 20% 1,2-propanediol and higher than with 20% 1,3-butanediol. Fifteen percent 2,3-butanediol protects fewer red blood cells than 15% glycerol or 1,2-propanediol, with a maximum survival of about 80%. The best cryoprotection by 30% 2,3-butanediol 97% dl is obtained at the slowest cooling and warming rates, where survival approaches 90%. After a minimum, an increase of survival is observed at the fastest cooling rates, which would correspond to complete vitrification. These rates are lower than with 30%, 1,2-propanediol or 1,3-butanediol, in agreement with the higher glass-forming tendency of 2,3-butanediol 97% dl solutions. In agreement with the remarkable physical properties of its aqueous solutions, the present experiments also suggest that 2,3-butanediol containing mainly the levo and dextro isomers could be a very useful cryoprotectant for organ cryopreservation. However, it would perhaps be better to use it in combination with other cryoprotectants, since it is a little more toxic than glycerol or 1,2-propanediol at high concentrations.

Theoretical prediction of devitrification tendency: determination of critical warming rates without using finite expansions

Previously, critical warming rates vcr above which ice did not have enough time to crystallize had been roughly evaluated for many wholly amorphous aqueous solutions. These evaluations were obtained by extrapolation of the linear variation of the devitrification temperature Td with log v, where v is the warming rate, observed experimentally between 2.5 and 80 degrees C/min. Theory also gives such a linear variation, but only using the first term of a finite expansion. The other terms can be neglected only for small variations of Td. These evaluations were sufficient for classification of the solutions, but large errors were made in vcr. A new and more accurate method of determination of the variation of Td with v is presented here. The general equation giving in our models the derivative of the quantity of ice formed versus temperature T is differentiated, instead of integrated using a finite expansion. This gives an explicit expression of v versus Td assuming that the ratio xd of the quantity of ice formed at Td to the total quantity of ice formed on warming is constant. Experimentally, xd is constant within a good approximation. Theoretical curves representing the variation of Td with v have been drawn for solutions of 35 or 45% (w/w) 1,2-propanediol in water. Td never reaches the temperature of the end of melting Tm, but as v tends toward infinity, Td tends toward an asymptotic value of 0.96Tm for 35% solute. For that solution, above about 10(3) degrees C/min, Td deviates appreciably from linearity with log v, but 1/Td remains almost linear with log v up to Td congruent to 0.95Tm. Therefore, systematic comparison of the theoretical variation of Td with v with a linear variation of 1/Td with log v has been done, varying the parameters of the equations within the entire experimental range. Similar conclusions can be given for all the solutions. Experimentally for Td = 0.95Tm, the quantity of ice crystallized is generally less than 0.1% of the solution, reaching 1% only once. Therefore, a new definition of the critical warming rate vcr has been used, corresponding to extrapolation of the linear variation of 1/T with log v up to Td = 0.95Tm. New values of vcr have been calculated for all the binary systems previously studied. The order of the solutions is almost the same, but the new values of vcr are significantly smaller than the former.

Experimental dissection of devitrification in aqueous solutions of 1,3-butanediol

Devitrification is a major problem which must be overcome for successful organ cryopreservation. Devitrification can be initiated on fracture planes and on bubbles, but the focus of attention here is on devitrification by ordinary heterogeneous and homogeneous mechanisms, which are the most relevant for organ preservation by vitrification. The purpose of the present studies was to define the devitrification process: to determine nucleation rates, ice-crystal growth rates, and the distribution of ice-crystal size and to evaluate the applicability of existing quantitative models of these processes which have successfully approximated the behavior of other aqueous systems. The present work was done using differential scanning calorimetry and cryomicroscopy. The amount of ice formed has been estimated for highly concentrated solutions. Kinetic parameters are presented here for isothermal conditions and continuous heating rate experiments. The classical theory based on the Johnson-Avrami equation has been evaluated and the results are compared with the theory of Boutron. The agreement is good for the continuous heating rate conditions, but results differ for the isothermal conditions.