Ice Crystals Research Articles

Effect of Liquid Nitrogen Freezing Temperature on the Muscle Quality of Litopenaeus vannamei.

The implications of different liquid nitrogen freezing (LNF) temperatures (-35 °C, -65 °C, -95 °C, and -125 °C) on the ice crystal and muscle quality of white shrimp (Litopenaeus vannamei) were investigated in this essay. The results showed that better muscle quality was maintained after LNF treatment compared to that after air blast freezing (AF) treatment. As the freezing temperature of liquid nitrogen decrease, the freezing speed accelerated, with the freezing speed of LNF at -125 °C being the fastest. However, an excessively fast freezing speed was not conducive to maintaining the quality of shrimp. Among all the freezing treatments, LNF at -95 °C led to the lowest thawing losses and cooking losses, and the highest L* values, indicating that LNF at -95 °C could keep the water holding capacity of frozen shrimp better than that with other freezing methods. At the same time, LNF at -95 °C resulted in higher water holding capacity, and hardness values for shrimps than those with other frozen treatments (p < 0.05). In addition, the results of the water distribution of shrimps showed that treatment with a -95 °C LNF reduced the migration rate of bound and free water. Meanwhile, the microstructural pores of shrimps in the -95 °C LNF group were smaller, indicating that the ice crystals generated during -95 °C LNF were relatively smaller than those generated via other frozen treatments. In conclusion, an appropriate LNF temperature (-95 °C) was beneficial for improving the quality of frozen shrimp, and avoiding freezing breakage.

Characterization of the Spatial Distribution of the Thermodynamic Phase Within Mixed‐Phase Clouds Using Satellite Observations

AbstractModels assume that mixed‐phase clouds consist of uniformly mixed ice crystals and liquid cloud droplets when observations have shown that they consist of clusters, or “pockets,” of ice crystals and liquid cloud droplets. We characterize the spatial distribution of cloud phase over the Arctic and the Southern Ocean using active satellite observations and determine the relative importance of collocated meteorological parameters and aerosols from reanalysis to predict how uniformly mixed mixed‐phase clouds are for the first time. We performed a multi‐linear regression fit to the data set to predict the spatial distribution of the ice and liquid pockets. Contrary to what models suggest, mixed‐phase clouds are rarely perfectly homogeneous. Our results suggest that high temperatures are associated with homogeneously mixed ice and liquid pockets. We also find that a high mixing ratio of black carbon is associated with heterogeneously mixed ice and liquid pockets.

Impact of secondary ice in a frozen NaCl freeze-concentrated solution on the extent of methylene blue aggregation

Freezing and lyophilization have been utilized for decades to stabilize pharmaceutical and food products. Freezing a solution that contains dissolved salt and/or organic matter produces pure primary ice crystal grains separated by freeze-concentrated solutions (FCS). The microscopic size of the primary ice crystals depends on the cooling conditions and the concentration of the solutes. It is generally accepted that primary ice crystals size influences the rate of sublimation and also can impact physico-chemical behaviour of the species in the FCS. This article, however, presents a case where the secondary ice formed inside the FCS plays a critical role. We microscoped the structures of ice-cast FCS with an environmental scanning electron microscope and applied the aggregation-sensitive spectroscopic probe methylene blue to determine how the microstructure affects the molecular arrangement. We show that slow cooling at −50 °C produces large salt crystals with a small specific surface, resulting in a high degree of molecular aggregation within the FCS. In contrast, fast liquid nitrogen cooling yields an ultrafine structure of salt crystals having a large specific surface area and, therefore, inducing smaller aggregation. The study highlights a critical role of secondary ice in solute aggregation and introduces methylene blue as a molecular probe to investigate freezing behaviour of aqueous systems with crystalline solute.

Raman lidar-derived optical and microphysical properties of ice crystals within thin Arctic clouds during PARCS campaign

Abstract. Cloud observations in the Arctic are still rare, which requires innovative observation techniques to assess ice crystal properties. We present an original approach using the Raman lidar measurements applied to a case study in northern Scandinavia. The vertical profiles of the optical properties, the effective radius of ice crystals and ice water content (IWC) in Arctic semi-transparent clouds were assessed using quantitative ground-based lidar measurements at 355 nm performed from 13 to 26 May 2016 in Hammerfest (north of Norway, 70∘39′48′′ N, 23∘41′00′′ E). The field campaign was part of the Pollution in the ARCtic System (PARCS) project of the French Arctic Initiative. The presence of low-level semi-transparent clouds was noted on 16 and 17 May. The cloud base was located just above the atmospheric boundary layer where the 0 ∘C isotherm reached around 800 m above the mean sea level (a.m.s.l.). To ensure the best penetration of the laser beam into the cloud, we selected case studies with cloud optical thickness (COT) lower than 2 and out of supercooled liquid pockets. Lidar-derived multiple scattering coefficients were found to be close to 1 and ice crystal depolarization around 10 %, suggesting that ice crystals were small and had a rather spherical shape. Using Mie computations, we determine effective radii between ∼7 and 25 µm in the clouds for ice water contents between 1 and 8 mg m−3, respectively. The uncertainties regarding the effective radii and ice water content are on average 2 µm and 0.65 mg m−3, respectively.

Study on flow and heat transfer characteristics of salt solution ice slurry

As a phase change material, ice slurry allows the storage of thermal energy in the form of latent heat. This has great advantages in terms of reducing energy consumption and environmental protection, and is being widely used. In this study, based on the Eulerian-Eulerian CFD model and the Population Balance Model (PBM), the flow and heat transfer characteristic of salt solution ice slurry was simulation studied, which included the pressure drop, friction coefficient, volume fraction, distribution of ice crystals and local heat transfer coefficient during the flow and solidification of salt solution ice slurry in different conditions. And the experimental system is set up to verify the results of the model and analyze the variation rules of these parameters. The results showed that in salt solutions with different concentrations, when the flow rate and solid phase volume fraction increase, the pressure drop and local heat transfer coefficient of the ice slurry will increase. The surface heat transfer coefficient reached to 2.5 × 103 W m-2 K-1, 2.9 × 103 W m-2 K-1, and 3.2 × 103 W m-2 K-1 when ice crystal volume fraction was 5 %, 10 %, and 15 %, respectively. The study will contribute to understanding of the changes in basic characteristics of salt solution slurry during the flow and phase transition processes.

Experimental study of the mechanical and thermal properties of metakaolin based geopolymer stabilized soil during low temperature curing

To address the challenges associated with significant thermal disturbance and carbon emissions resulting from the conventional stabilization of frozen soil using cement, geopolymer material is used to replace cement to stabilize frozen soil. The unconfined compressive strength (UCS) of the geopolymer stabilized soil was investigated in relation to the proportions of metakaolin (MK), calcium carbide slag (CCS), curing temperature, and curing age. Microscopic analysis was conducted to unveil the stabilized mechanism. The UCS, shear strength, thermal conductivity, hydration products and microstructure of geopolymer stabilized soil and cement soil were compared in parallel. A total of 240 experiments were conducted in this study. The outcomes indicate that the optimal content of MK and CCS is 10% and 6% respectively. The UCS of samples with the optimal content after 28d of curing at 20 °C, −2 °C, and − 10 °C are 3.783 MPa, 1.164 MPa, and 0.901 MPa respectively. The primary causes of the rise in UCS of the geopolymer stabilized soil are the production of amorphous calcium silicate hydrate and calcium aluminate hydrate gel as a result of the stimulation of MK based geopolymer with CCS. The UCS of the geopolymer stabilized soil decreases with a decrease in curing temperature. In frozen conditions, the expansion of ice crystals in the soil creates voids and promotes crack growth, leading to a decrease in the efficiency of geopolymerization reactions. After 28d of curing at room temperature and low temperature, the geopolymer stabilized soil with the optimal content exhibits higher UCS, failure strain, shear strength, cohesion, and internal friction angle compared to the cement soil. At all curing temperatures and ages, the geopolymer stabilized soil has a lower thermal conductivity than the cement soil. The geopolymer stabilized soil is less susceptible to low temperature curing than cement soil, demonstrating a larger amount of hydration products and a denser microstructure, according to experimental results from XRD and SEM. The results of this work offer a theoretical foundation for using geopolymer in place of cement to stabilize soils in permafrost regions.

Thundercloud structures detected and analyzed based on coherent Doppler wind lidar

Abstract. The studies of intracloud discharges may shed light on the microphysical structure of thunderclouds, as both the magnitude and the sign of charge separation due to graupel collides with ice crystals within the strong updrafts are influenced by the surrounding environment. Here, a compact all-fiber coherent Doppler wind lidar (CDWL) working at the 1.5 µm wavelength is applied for probing the dynamics and microphysics structure of thunderstorms. Thanks to the precise spectrum measurement, multi-component spectra signals of thunderstorms can be analyzed by the CDWL. The spectrum width, skewness, and Doppler velocity of CDWL is used to separate and identify the particle composition and polarity. In the experiment, the thundercloud properties are detected by the CDWL, 10.6 cm Doppler weather radar (DWR), and Advanced Geosynchronous Radiation Imager (AGRI) onboard Fengyun-4 satellites. In particular, the spectrum width and skewness of the thundercloud below the 0 ∘C isotherm are increased, and when a cloud-ground lightning occurs, there is additional graupel with a velocity greater than 5 m s−1. It indicates that this region is a melting layer, and lightning activity changes the motion characteristics of graupel, affecting the charge structure of the whole thundercloud. In general, our findings provide details on the velocity, phase, and composition of particles in the outside updraft region of the thunderstorm. The identification and analysis of graupel is particularly important. It is proved that the precise spectrum of CDWL is a promising indicator for studying the charge structure of thunderstorms.

Technical examination of cryonics

Cryonics is the preservation of the human body in low temperatures with the hope of reviving it in the future. This comprehensive article navigates through the three stages of cryonics: Preparation, Stasis, and Revival. In the Preparation phase, from the deployment of standby teams upon legal death announcement to cryoprotectant perfusion, which replaces bodily fluids with solutions to minimize freezing damage. Vitrification is an innovative technique, countering ice crystallization and reducing the dependence on precise optimal cooling rates. The cryoprotective agents, permeable and nonpermeable, are required to assist vitrification. As a result, it is important to take into account the toxicity of cryoprotective agents. Stasis, the immersion in liquid nitrogen, secures long-term preservation. Cryostats and Dewars serve as the guardians of cryonics temperatures, maintaining a stable environment. Revival, the final stage, is determined by precise rewarming and cell repair. Nanotechnology might be applied to the warming and repairing procedures. Understanding cell volume dynamics and harnessing nanotechnologys potential increases the possibility of successful revival. This article aims to provide an examination of Cryonics.

Effectiveness of glycerol, DMSO and trehalose in the process of cryopreservation of drone semen from the species apis mellifera

Cryopreservation of economically important or endangered animal species is becoming an increasingly popular practice in the field of reproductive biotechnologies. The mass extinction of honey bee (Apis Mellifera) colonies in the last decade requires the use of new chemical components in cryopreservation media for the storage of male gametes. A number of studies demonstrate conflicting data regarding the success rate and cytotoxicity of glycerol and dimethyl sulfoxide and to a lesser extent Trehalose. Dimethyl sulfoxide is an organosulfur compound with low cryotoxicity which transforms into solids below room temperature and this property makes it suitable for cryoprotectant. The kosmotropic properties of glycerol allow it to create hydrogen bonds with water molecules, making it difficult to form intracellular ice crystals in the cryoprotective media. Due to its high-water retaining properties Trehalose can be used as cryoprotectant, but its effectiveness has not yet been thoroughly researched in relation to the cryopreservation of bee drone spermatozoa. The research aims to compare the effectiveness of each of the specified cryoprotectants regarding the preservation of spermatozoa from Apiss Mellifera drones.

Solid-liquid phase equilibrium and thermodynamic model of ternary system (NH4+ //SO42−, H2PO4−–H2O) from 313.15 to 343.15 K

A tremendous amount of wastewater containing ammonium salts, mainly NH4H2PO4 and (NH4)2SO4, has been produced in the production of cathode material of lithium iron phosphate (LFP). However, as an important basis for salt separation, the solid–liquid phase equilibrium (SLPE) of these two salts has been investigated by few studies. In this study, SLPE of the ternary system (NH4+ //SO42−, H2PO4−–H2O) from 313.15 K to 343.15 K at 101.2 kPa were investigated by isothermal dissolution method, and the corresponding physicochemical properties (density, viscosity, and pH) of saturated solution were measured. The phase diagram is composed of one invariant point, two univariant curves, and two single-salt crystallization fields for NH4H2PO4 and (NH4)2SO4. Comparing the phase diagrams from 263.15 K to 343.15 K, it is obvious that two single-salt crystallization fields shrink with increasing temperature. And the area reduction of NH4H2PO4 in two salts is more significant. When the temperature drops below 268.15 K, the ice crystallization field would appear. Neither single-salt solid solution, hydrous salt nor double salt was found in the whole temperature range. Furthermore, Pitzer model was successfully applied to describe the SLPE of the ternary system at temperatures from 273.15 K to 343.15 K. The lacking Pitzer-model parameters of mixed electrolytes (θSO4-H2PO4 and ψNH4-SO4-H2PO4) were calculated, and the temperature coefficients of model parameters and dissolution equilibrium constant were obtained. The importance of this study is that it supplies basic data and theoretical references for the separation and resource utilization of two ammonium salts from wastewater in the LFP batteries industry.

Confining He Atoms in Diverse Ice-Phases: Examining the Stability of He Hydrate Crystals through DFT Approaches.

In the realm of solid water hydrostructures, helium atoms have a tendency to occupy the interstitial spaces formed within the crystal lattice of ice structures. The primary objective of this study is to examine the stability of various ice crystals when influenced by the presence of He atoms. Presenting a first attempt at a detailed computational description of the whole energy components (guest-water, water-water, guest-guest) in the complete crystal unit cells contributes to enhancing the knowledge available about these relatively unexplored helium-water systems, which could potentially benefit future experiments. For this purpose, two different ice structures were considered: the previously established He@ice II system, and the predicted (but currently nonexistent) He@ice XVII system. One of the main features of these He-filled structures is the stability conferred by the weak van der Waals dispersion forces that occur between the host lattice and the guest atoms, in addition to the hydrogen bonds established among the water molecules. Hence, it is crucial to accurately describe these interactions. Therefore, the first part of this research is devoted examining the performance and accuracy of various semi-local and non-local DFT/DFT-D functionals, in comparison with previous experimental and/or high-level computational data. Once the best-performing DFT functional has been identified, the stability of these empty and He-filled structures, including different number of He atoms within the lattices, is analysed in terms of their structural (lattice deformation), mechanical (pressure compression effects) and energetic properties (binding and saturation energies). In this manner, the potential formation of these structures under zero temperature and pressure conditions can be evaluated, while their maximum storage capacity is also determined. The obtained results reveal that, despite the weak underlying interactions, the He encapsulation has a rather notable effect on both lattice parameters and energetics, and therefore, the guest-host interactions are far from being negligible. Besides, both ice crystals are predicted to remain stable when filled with He atoms, with ice XVII exhibiting a higher capacity for accommodating a larger number of guest atoms within its interstitial spaces.

Interactions between Gravity Waves and Cirrus Clouds: Asymptotic Modeling of Wave-Induced Ice Nucleation

Abstract We present an asymptotic approach for the systematic investigation of the effect of gravity waves (GWs) on ice clouds formed through homogeneous nucleation. In particular, we consider high- and midfrequency GWs in the tropopause region driving the formation of ice clouds, modeled with a double-moment bulk ice microphysics scheme. The asymptotic approach allows for identifying reduced equations for self-consistent description of the ice dynamics forced by GWs including the effects of diffusional growth and nucleation of ice crystals. Further, corresponding analytical solutions for a monochromatic GW are derived under a single-parcel approximation. The results provide a simple expression for the nucleated number of ice crystals in a nucleation event. It is demonstrated that the asymptotic solutions capture the dynamics of the full ice model and accurately predict the nucleated ice crystal number. The present approach is extended to allow for superposition of GWs, as well as for variable ice crystal mean mass in the deposition. Implications of the results for an improved representation of GW variability in cirrus parameterizations are discussed.

Microstructural characterization of depth hoar and ice‐crust layers using a micro‐CT, and hypothesis of ice‐crust formation under a thunderstorm

AbstractThe microstructural features typical of depth hoar and ice‐crust layers in both blocks of snow and a firn core that were extracted at Summit, Greenland (72°35′ N, 38°25′ W) in June, 2017 have been characterized using x‐ray microcomputed tomography (micro‐CT). In the depth hoar, the density is much lower, and the porosity, pore sizes, and specific surface area (SSA) are greater than those in adjacent layers. In the ice‐crusts, the density and the particle size are greater, and the porosity, pore size, and SSA are less than those in adjacent layers. Note that the mean structure thickness in the depth hoar was greater than that in adjacent layers, but that increase was simply related to the one‐ or two‐dimension ice crystals, that is, needle‐like or plate‐like structures, being included in the measurements for depth hoar. Using related microstructural parameters derived from the micro‐CT data, we propose a model based on refreezing of pre‐melted water (PMW) droplets electrostatically‐transported by the electric field between thunderclouds and the ice sheet created by a thunderstorm that describes the processes of the ice‐crust formation (ICF). Whether the ice‐crust forms with depth hoar depends on both the kinetic energy from the PMW droplets and the latent heat liberated from the freezing of the PMW. This work is the first to build the relationship between the atmosphere and ice sheets by a thunderstorm. Finally, we provide an experimental geophysics‐based method through the ICF under laboratory conditions to learn more about the interaction between atmospheric electrodynamics and thermodynamics.

Freezing Low Numbers of Sperm

Azoospermia, a condition defined by a complete lack of sperm in the ejaculate, presents a significant reproductive challenge for many infertile men worldwide. In recent years, Microsurgical Sperm Extraction (Micro-TESE) has emerged as an innovative surgical technique, allowing clinicians to retrieve viable sperm directly from the testicular tissues of patients diagnosed with this condition. A crucial aspect of optimizing the reproductive potential of the extracted sperm lies in the subsequent preservation techniques employed. This study delves deep into one such technique, sperm vitrification. As opposed to the traditional slow freezing methods, vitrification offers a rapid-cooling approach that effectively sidesteps the formation of potentially damaging ice crystals, thereby maintaining the structural and functional integrity of the sperm. The survival rates of sperm post-thawing, when subjected to vitrification, have been found to be commendably high, with figures often exceeding 60%. This is a promising statistic, particularly when dealing with minuscule sperm quantities as retrieved in Micro-TESE. However, the importance of sperm freezing transcends azoospermic scenarios. A broader and crucial indication for sperm freezing is fertility preservation, particularly poignant for cancer patients on the brink of undergoing treatments like chemotherapy or radiation, which could jeopardize their reproductive future. For these individuals, the opportunity to freeze their sperm offers a chance to father biological offspring post-recovery. By allowing multiple in vitro fertilization (IVF) attempts without necessitating recurrent surgical interventions, sperm cryopreservation, especially using vitrification, amplifies the chances of achieving biological parenthood. This is pivotal for both azoospermic individuals and cancer patients, safeguarding their dreams of family amidst medical adversities. In conclusion, the efficacy of vitrification, especially in the context of limited sperm counts, has the potential to reshape the landscape of male infertility treatments, offering a glimmer of hope for numerous affected individuals and their partners.

Study on the ice crystals growth under pectin gels with different crosslinking strengths by modulating the degree of amidation in HG domain.

The ice crystal morphology formed under a series of amidated pectin gels with various crosslink strengths were investigated. The results showed that as the degree of amidation (DA) increased, pectin chains exhibited shorter homogalacturonan (HG) regions. Highly amidated pectin exhibited a faster gelation rate and a stronger gel micro-network via hydrogen bonds. Based on cryogenic scanning electron microscopy (cryo-SEM), smaller ice crystals were formed in frozen gel with low DA, suggesting that a weaker cross-linked gel micro-network was more effective at inhibiting crystallization. After sublimation, lyophilized gel scaffolds with high crosslink strength displayed less number of pores, high porosity, lower specific surface area, and greater mechanical strength. This study is expected to confirm that the microstructure and mechanical properties of freeze-dried pectin porous materials could be regulated by changing the crosslink strength of pectin chains, which is achieved by increasing the degree of amidation in the HG domains.

A strategy to fabricate hierarchical microporous architecture of polyimide nanofibrous aerogels with efficient electromagnetic wave absorption and thermal insulation

The aviation industry requires advanced aerogels that combine both electromagnetic wave (EM) attenuation and thermal insulation capabilities. This work involved the fabrication of Ti3C2Tx MXene/polyimide nanofibrous (PINF) aerogels through freeze-drying and thermal imidization. The hierarchical microporous architecture was formed by the interconnected primary pores induced by the removal of ice crystals and secondary pores from the PINF web. The unique highly porous 3D network of the nanofibrous aerogel provided well-matched impedance and enhanced multiple reflections and scattering of EM waves. The polar functional groups and defects on MXene induced dipole polarization, and the heterointerfaces between the PINFs and MXene enhanced the interfacial polarization. Consequently, the MXene/PINF aerogels exhibited efficient microwave absorption, showing a minimum reflection loss (RLmin) of −37.9 dB and an effective absorption bandwidth (EAB) of 3.3 GHz. Moreover, nanofibrous aerogels also exhibited low thermal conductivity and remarkable compression properties, making them suitable for utilization in complex environments.

Repeated freezing impacts buoyancy and photosynthesis of a rafting kelp species

Antarctica was once considered biologically isolated, surrounded by oceanic barriers (Fraser et al.2018). However, floating materials such as kelp rafts (Fraser et al.2018, Avila et al.2020), wood (Lewis et al.2005) and plastics (Avila et al.2020) are now known to cross these barriers and reach Antarctic shores. Such incursions might enable non-native species (either rafting species themselves or associated hitchhikers) to colonize Antarctica as the climate warms (Avila et al.2020, Fraser et al.2020), but whether these species will be able to survive and reproduce in the Antarctic is not yet known. Sea ice is a defining characteristic of Antarctic coastlines, and modelled trajectories of kelp rafts (Fraser et al.2018) cross-referenced against sea-ice observations (Parkinson 2019) suggest that collisions between rafts and seasonal sea ice occur frequently (Fig. 1a); thus, rafts are expected to be entrained in, on or under sea ice and experience multiple freeze-and-thaw cycles on their journeys to Antarctica. In addition, kelp rafts that reach the Antarctic intertidal will experience temperatures well below 0°C if exposed to the air at low tide. Freezing can cause severe disruptive stress to seaweeds, and ice crystals growing in intercellular spaces can damage cell membranes and cause cell lysis (Eggert 2012). Such damage could affect the buoyancy of kelp tissue and decrease rafting ability. Although some non-native kelp rafts recovered from Antarctic shores appeared to still be reproductively viable, with mature gametes observed in reproductive tissue (Fraser et al.2018), tissue damage caused by freezing could have widespread effects on the health, function and establishment success of a non-native species traversing the Southern Ocean.

Insight into the mechanism of pressure shift freezing on water mobility, microstructure, and rheological properties of grass carp surimi gel

This study found that using pressure shift freezing (PSF) treatment could suppress the decline in the quality of grass carp surimi gel during the conventional air freezing (CAF) process, and even improve the original properties of surimi gel. The surimi gel breaking force was about 2.5 times followed by PSF treatment (4.5 N) compared to the CAF group (1.8 N). The formation of small ice crystals in the PSF group reduced the mechanical damage to the sample structure compared to the large ice crystals formed in CAF groups. In addition, PSF treatment was found to be responsible for the change in protein and water mobility in surimi gel, which in turn positively influences the physicochemical properties of surimi gel. Industrial relevanceThe output of this study revealed the significance of PSF technology in the surimi gel processing and meat processing industry. The development of new products and the use of new resources are very important in addressing the global food crisis and resource shortages. The application of PSF technology has also laid a foundation for freshwater surimi gel products to replace seawater surimi gel products.

Preferential ice growth on grooved surface for crisscross-aligned graphene aerogel with large negative Poisson’s ratio

Ice formation on solid surfaces is a ubiquitous process in our daily life, and ice orientation plays a critical role in anti-icing/deicing, organ cryo-preservation, and material fabrication. Although previous studies have shown that surface grooves can regulate the orientation of ice crystals, whether the parallel or perpendicular alignment to the grooves is still under debate. Here, we systematically investigate ice formation and its oriented growth on grooved surfaces through both in situ observation and theoretical simulation, and discover a remarkable size effect of the grooves. With the designability of surface groove patterns, the preferential growth of ice crystals is programmed for the fabrication of a crisscross-aligned graphene aerogel with large negative Poisson’s ratio. In addition, the size effect provides guidance for the design and fabrication of solid surfaces where the effective control of ice orientation is highly desired, such as efficient deicing, long time organ cryo-preservation, and ice-templated materials.

Cryogenic enrichment of Plasmodium falciparum gametocytes from spiked whole blood

Each individual cell type typically requires a unique set of conditions for optimal cryopreservation outcome, which relates to its specific response to cryoprotective agent (CPA) toxicity, osmotic behavior and sensitivity to ice crystallization. Cryopreservation of heterogenous cell populations is therefore exceedingly difficult as it requires separate and often conflicting conditions for each cell type. Conversely, these contrasting conditions could be utilized to favor cryogenic preference of a single cell population within a heterogenous sample, leading to its enrichment by elimination of remaining cells. To establish proof-of-concept for this overall approach, a protocol was developed for the cryogenic enrichment of Plasmodium falciparum gametocytes from whole blood. To accomplish this goal, we evaluated the effects of CPAs and cooling conditions during cryopreservation of whole blood samples spiked with P. falciparum gametocytes. We identified that cooling to −80 °C at a rate of −1 °C/min in the presence of 11 % glycerol selectively favors recovery of gametocytes. This protocol eliminates 95.3 ± 1.7 % of total blood cells and recovers 43.2 ± 6.5 % of parasites, leading to a 19-fold enrichment as assessed by microscopic examination of blood smears. This protocol is tunable, where gametocyte enrichment 900-fold may be feasible, however there is an apparent tradeoff in overall parasite recovery. Although translation of this protocol for point-of-care testing for malaria presents many challenges, the overall approach of cryogenic purification may prove useful for alternative diagnostic applications.