Membrane hydration correlates to cellular biophysics during freezing in mammalian cells

Cryopreservation of Immune Cells: Recent Progress and Challenges Ahead

Cryopreservation of immune cells is considered as a key enabling technology for adoptive cellular immunotherapy. However, current immune cell cryopreservation technologies face the challenges with poor biocompatibility of cryoprotection materials, low efficiency, and impaired post-thaw function, limiting their clinical translation. This review briefly introduces the adoptive cellular immunotherapy and the approved immune cell-based products, which involve T cells, natural killer cells and etc. The cryodamage mechanisms to these immune cells during cryopreservation process are described, including ice formation related mechanical and osmotic injuries, cryoprotectant induced toxic injuries, and other biochemical injuries. Meanwhile, the recent advances in the cryopreservation medium and freeze-thaw protocol for several representative immune cell type are summarized. Furthermore, the remaining challenges regarding on the cryoprotection materials, freeze-thaw protocol, and post-thaw functionality evaluation of current cryopreservation technologies are discussed. Finally, the future perspectives are proposed toward advancing highly efficient cryopreservation of immune cells.

Orthobiologic Products: Preservation Options for Orthopedic Research and Clinical Applications

The biological products used in orthopedics include musculoskeletal allografts-such as bones, tendons, ligaments, and cartilage-as well as biological therapies. Musculoskeletal allografts support the body's healing process by utilizing preserved and sterilized donor tissue. These allografts are becoming increasingly common in surgical practice, allowing patients to avoid more invasive procedures and the risks associated with donor site morbidity. Bone grafting is one of the most frequently used procedures in orthopedics and traumatology. Biologic approaches aim to improve clinical outcomes by enhancing the body's natural healing capacity and reducing inflammation. They serve as an alternative to surgical interventions. While preliminary results from animal studies and small-scale clinical trials have been promising, the field of biologics still lacks robust clinical evidence supporting their efficacy. Biological therapies include PRP (platelet-rich plasma), mesenchymal stem cells (MSCs)/stromal cells/progenitor cells, bone marrow stem/stromal cells (BMSCs), adipose stem/stromal cells/progenitor cells (ASCs), cord blood (CB), and extracellular vesicles (EVs), including exosomes. The proper preservation and storage of these cellular therapies are essential for future use. Preservation techniques include cryopreservation, vitrification, lyophilization, and the use of cryoprotective agents (CPAs). The most commonly used CPA is DMSO (dimethyl sulfoxide). The highest success rates and post-thaw viability have been achieved by preserving PRP with a rate-controlled freezer using 6% DMSO and storing other cellular treatments using a rate-controlled freezer with 5% or 10% DMSO as the CPA. Extracellular vesicles (EVs) have shown the best results when lyophilized with 50 mM or 4% trehalose to prevent aggregation and stored at room temperature.

Cryoprotective Polysaccharides with Ordered Gel Structures Induce Ice Growth Anticipation and Survival Enhancement during Cell Cryopreservation

This work cross-correlated rheological, thermodynamic, and conformational features of several natural polysaccharides to their cryoprotective performance. The basis of cryoprotection of FucoPol, pectin, and agar revealed a causal combination of (i) an emerging sol-gel transition (p = 0.014) at near-hypothermia (4 °C), (ii) noncolligative attenuated supercooling of the kinetic freezing point of water (p = 0.026) supporting ice growth anticipation, and (iii) increased conformational order (p < 0.0001), where helix-/sheet-like features boost cryoprotection. FucoPol, of highest cryoprotective performance, revealed a predominantly helical structure (α/β = 1.5) capable of forming a gel state at 4 °C and the highest degree of supercooling attenuation (TH = 6.2 °C). Ice growth anticipation with gel-like polysaccharides suggests that the gel matrix neutralizes elastic deformations and lethal cell volumetric fluctuations during freezing, thus preventing the loss of homeostasis and increasing post-thaw viability. Ultimately, structured gels capable of attenuated supercooling enable cryoprotective action at the polymer-cell interface, in addition to polymer-ice interactions. This rationale potentiates implementing alternative, biobased, noncytotoxic polymers in cryobiology.

Natural deep eutectic solvent: A promising eco-friendly food bio-inspired antifreezing

Bio-antifreezing is a green and highly effective strategy to inhibit ice nucleation. Bio-inspired antifreezing faces the severe challenges of significant toxicity and complex manufacturing procedures. Bio-inspired antifreezing natural deep eutectic solvent (Ba-NADES) could be an efficient and low or no-toxicity approach for the frozen food industry. Ba-NADES form a strong hydrogen bond network system under cold conditions, capably reducing the melting point of the system below the freezing point and effectively inhibiting ice growth. It has efficaciously alleviated freeze injury by Ba-NADES. The review highlights the current strategies of bio-inspired antifreezing, cold resistance behavior in organisms, and the existing applications of Ba-NADES. It updated information concerning their mechanisms for antifreezing. It emphasizes that the role of water on the antifreezing quality of NADES is worthy of further investigation for more extensive food applications. This work will provide a comprehensive overview of NADES antifreezing.

Photothermal heating of titanium nitride nanomaterials for fast and uniform laser warming of cryopreserved biomaterials

Titanium nitride (TiN) is presented as an alternative plasmonic nanomaterial to the commonly used gold (Au) for its potential use in laser rewarming of cryopreserved biomaterials. The rewarming of vitrified, glass like state, cryopreserved biomaterials is a delicate process as potential ice formation leads to mechanical stress and cracking on a macroscale, and damage to cell walls and DNA on a microscale, ultimately leading to the destruction of the biomaterial. The use of plasmonic nanomaterials dispersed in cryoprotective agent solutions to rapidly convert optical radiation into heat, generally supplied by a focused laser beam, proposes a novel approach to overcome this difficulty. This study focuses on the performance of TiN nanoparticles (NPs), since they present high thermal stability and are inexpensive compared to Au. To uniformly warm up the nanomaterial solutions, a beam splitting laser system was developed to heat samples from multiple sides with equal beam energy distribution. In addition, uniform laser warming requires equal distribution of absorption and scattering properties in the nanomaterials. Preliminary results demonstrated higher absorption but less scattering in TiN NPs than Au nanorods (GNRs). This led to the development of TiN clusters, synthetized by nanoparticle agglomeration, to increase the scattering cross-section of the material. Overall, this study analyzed the heating rate, thermal efficiency, and heating uniformity of TiN NPs and clusters in comparison to GNRs at different solution concentrations. TiN NPs and clusters demonstrated higher heating rates and solution temperatures, while only clusters led to a significantly improved uniformity in heating. These results highlight a promising alternative plasmonic nanomaterial to rewarm cryopreserved biological systems in the future.

Hydrogen-Rich Water Prevents Dehydration-Induced Cellular Oxidative Stress and Cell Death in Human Skin Keratinocytes

Hypohydration is linked to increased risk of a variety of diseases and can be life-threatening, especially in elderly populations. Dehydration induces cellular damage partially through the production of reactive oxygen species (ROS) in cells, tissues and organs. Hydrogen molecules are known to convert ROS to harmless water. Therefore, theoretically hydrogen-rich water (HW) might eliminate dehydration-induced ROS and reverse its harmful effects in cells. In this in vitro study, we demonstrated that air-drying for 5 min could induce ROS generation in both nucleus and cytoplasm of human keratinocytes HaCaT as quantified by CellROX® Green/Orange reagents (Thermo Fisher Scientific, Waltham, Massachusetts, U.S.), respectively. Conversely, when the air-drying time was increased to 10 and 20 min, HaCaT cells lost the ability to produce ROS. Scanning electron microscopic (SEM) images showed that 10 min air-drying could induce severe membrane damage in HaCaT cells. PrestoBlue assay showed that, when HaCaT cells were air-dried for 20 min, cell viability was decreased to 27.6% of the control cells 48 h later. However, once HaCaT cells were pretreated with HW-prepared media, dehydration-induced intracellular ROS, cell membrane damage and cell death were significantly reduced as compared with double distilled water (DDW) under the same conditions. In conclusion, our data suggested that HW can decrease dehydration-induced harmful effects in human cells partially through its antioxidant capacity.

Multiparametric biophysical profiling of red blood cells in malaria infection

Biophysical separation promises label-free, less-invasive methods to manipulate the diverse properties of live cells, such as density, magnetic susceptibility, and morphological characteristics. However, some cellular changes are so minute that they are undetectable by current methods. We developed a multiparametric cell-separation approach to profile cells with simultaneously changing density and magnetic susceptibility. We demonstrated this approach with the natural biophysical phenomenon of Plasmodium falciparum infection, which modifies its host erythrocyte by simultaneously decreasing density and increasing magnetic susceptibility. Current approaches have used these properties separately to isolate later-stage infected cells, but not in combination. We present biophysical separation of infected erythrocytes by balancing gravitational and magnetic forces to differentiate infected cell stages, including early stages for the first time, using magnetic levitation. We quantified height distributions of erythrocyte populations-27 ring-stage synchronized samples and 35 uninfected controls-and quantified their unique biophysical signatures. This platform can thus enable multidimensional biophysical measurements on unique cell types.

Cryopreservation of primary cultures of mammalian somatic cells in 96-well plates benefits from control of ice nucleation

Cryopreservation of mammalian cells has to date typically been conducted in cryovials, but there are applications where cryopreservation of primary cells in multiwell plates would be advantageous. However excessive supercooling in the small volumes of liquid in each well of the multiwell plates is inevitable without intervention and tends to result in high and variable cell mortality. Here, we describe a technique for cryopreservation of adhered primary bovine granulosa cells in 96-well plates by controlled rate freezing using controlled ice nucleation. Inducing ice nucleation at warm supercooled temperatures (less than 5 °C below the melting point) during cryopreservation using a manual seeding technique significantly improved post-thaw recovery from 29.6% (SD = 8.3%) where nucleation was left uncontrolled to 57.7% (9.3%) when averaged over 8 replicate cultures (p < 0.001). Detachment of thawed cells was qualitatively observed to be more prevalent in wells which did not have ice nucleation control which suggests cryopreserved cell monolayer detachment may be a consequence of deep supercooling. Using an infra-red thermography technique we showed that many aliquots of cryoprotectant solution in 96-well plates can supercool to temperatures below −20 °C when nucleation is not controlled, and also that the freezing temperatures observed are highly variable despite stringent attempts to remove contaminants acting as nucleation sites. We conclude that successful cryopreservation of cells in 96-well plates, or any small volume format, requires control of ice nucleation.

Flexible lipid nanomaterials studied by NMR spectroscopy

Advances in solid-state nuclear magnetic resonance spectroscopy inform the emergence of material properties from atomistic-level interactions in membrane lipid nanostructures.

Cryoprotectant-Free Freezing of Cells Using Liquid Marbles Filled with Hydrogel

Cryopreservation without cryoprotectant remains a significant challenge for the re-establishment of cell culture after freeze-thaw. Thus, finding an alternative and a simple cryopreservation method is necessary. Liquid marble (LM)-based digital microfluidics is a promising approach for cryoprotectant-free cryopreservation. However, the use of this platform to efficiently preserve samples with low cell density and well-controlled serum concentrations has not been investigated. We addressed this issue by embedding an agarose-containing fetal bovine serum (FBS) inside the LM. A low density of 500 cells/μL of murine 3T3 cells was selected for evaluating the postcryogenic survivability. The effects on the post-thaw cell viability of the concentration of agarose, the amount of FBS inside the agarose, and the volume of the LM were investigated systematically. This paper also presents an analysis on the changes in shape and crack size of post-thawed agarose. The results revealed that the embedded agarose gel serves as a controlled release mechanism of FBS and significantly improves cell viability. Post-thaw recovery sustains major cellular features, such as viability, cell adhesion, and morphology. The platform technology reported here opens up new possibilities to cryopreserve rare biological samples without the toxicity risk of cryoprotectants.

Effect of Ice Nucleation and Cryoprotectants during High Subzero-Preservation in Endothelialized Microchannels

Cryopreservation is of significance in areas including tissue engineering, regenerative medicine, and organ transplantation. We investigated endothelial cell attachment and membrane integrity in a microvasculature model at high subzero temperatures in the presence of extracellular ice. The results show that in the presence of heterogeneous extracellular ice formation induced by ice nucleating bacteria, endothelial cells showed improved attachment at temperature minimums of -6 °C. However, as temperatures decreased below -6 °C, endothelial cells required additional cryoprotectants. The glucose analog, 3-O-methyl-D-glucose (3-OMG), rescued cell attachment optimally at 100 mM (cells/lane was 34, as compared to 36 for controls), while 2% and 5% polyethylene glycol (PEG) were equally effective at -10 °C (88% and 86.4% intact membranes). Finally, endothelialized microchannels were stored for 72 h at -10 °C in a preservation solution consisting of the University of Wisconsin (UW) solution, Snomax, 3-OMG, PEG, glycerol, and trehalose, whereby cell attachment was not significantly different from unfrozen controls, although membrane integrity was compromised. These findings enrich our knowledge about the direct impact of extracellular ice on endothelial cells. Specifically, we show that, by controlling the ice nucleation temperature and uniformity, we can preserve cell attachment and membrane integrity. Further, we demonstrate the strength of leveraging endothelialized microchannels to fuel discoveries in cryopreservation of thick tissues and solid organs.

Lipid Droplet Phase Transition in Freezing Cat Embryos and Oocytes Probed by Raman Spectroscopy

Embryo and oocyte cryopreservation is a widely used technology for cryopreservation of genetic resources. One limitation of cryopreservation is the low tolerance to freezing observed for oocytes and embryos rich in lipid droplets. We apply Raman spectroscopy to investigate freezing of lipid droplets inside cumulus-oocyte complexes, mature oocytes, and early embryos of a domestic cat. Raman spectroscopy allows one to characterize the degree of lipid unsaturation, the lipid phase transition from the liquid-like disordered to solid-like ordered state, and the triglyceride polymorphic state. For all cells examined, the average degree of lipid unsaturation is estimated as ∼1.3 (with ±20% deviation) double bonds per acyl chain. The onset of the lipid phase transition occurs in a temperature range from -10 to +4°C and does not depend on the cell type. Lipid droplets in cumulus-oocyte complexes are found to undergo abrupt lipid crystallization shifted in temperature from the ordering of the lipid conformational state. In the case of mature oocytes and early embryos obtained in vitro, the lipid crystallization is broadened. In the frozen state, lipid droplets inside cumulus-oocyte complexes have a higher content of triglyceride polymorphic β and β' phases than estimated for mature oocytes and early embryos. For the first time, to our knowledge, the temperature evolution of the phase state of lipid droplets is examined. Raman spectroscopy is proved to be a promising tool for in situ monitoring of the lipid phase state in a single embryo/oocyte during its freezing.

Insights on Cryopreserved Sheep Fibroblasts by Cryomicroscopy and Gene Expression Analysis

Cryopreservation includes a set of techniques aimed at storing biological samples and preserving their biochemical and functional features without any significant alterations. This study set out to investigate the effects induced by cryopreservation on cultured sheepskin fibroblasts (CSSF) through cryomicroscopy and gene expression analysis after subsequent in vitro culture. CSSF cells were cryopreserved in a cryomicroscope (CM) or in a straw programmable freezer (SPF) using a similar thermal profile (cooling rate -5°C/min to -120°C, then -150°C/min to -196°C). CSSF volume and intracellular ice formation (IIF) were monitored by a CM, while gene expression levels were investigated by real-time polymerase chain reaction in SPF-cryopreserved cells immediately after thawing (T0) and after 24 or 48 hours (T24, T48) of post-thaw in vitro culture. No significant difference in cell viability was observed at T0 between CM and SPF samples, while both CM and SPF groups showed lower viability (p < 0.05) compared to the untreated control group. Gene expression analysis of cryopreserved CSSF 24 and 48 hours post-thawing showed a significant upregulation of the genes involved in protein folding and antioxidant mechanisms (HPS90b and SOD1), while a transient increase (p < 0.05) in the expression levels of OCT4, BCL2, and GAPDH was detected 24 hours post-thawing. Overall, our data suggest that cryostored CSSF need at least 24 hours to activate specific networks to promote cell readaptation.

Comparative atomic-scale hydration of the ceramide and phosphocholine headgroup in solution and bilayer environments

Previous studies have used neutron diffraction to elucidate the hydration of the ceramide and the phosphatidylcholine headgroup in solution. These solution studies provide bond-length resolution information on the system, but are limited to liquid samples. The work presented here investigates how the hydration of ceramide and phosphatidylcholine headgroups in a solution compares with that found in a lipid bilayer. This work shows that the hydration patterns seen in the solution samples provide valuable insight into the preferential location of hydrating water molecules in the bilayer. There are certain subtle differences in the distribution, which result from a combination of the lipid conformation and the lipid-lipid interactions within the bilayer environment. The lipid-lipid interactions in the bilayer will be dependent on the composition of the bilayer, whereas the restricted exploration of conformational space is likely to be applicable in all membrane environments. The generalized description of hydration gathered from the neutron diffraction studies thus provides good initial estimation for the hydration pattern, but this can be further refined for specific systems.

Cryopreservation of cells: FT-IR monitoring of lipid membrane at freeze-thaw cycles

In the present study, FTIR spectroscopy was used to monitor the freeze-thaw cycle of two cellular lines (HuDe and Jurkat) suspended in three different media: phosphate buffer solution (PBS); dimethylsulfoxide (DMSO)/PBS solution at 0.1 DMSO molar fraction; and CryoSure (0.1 DMSO molar fraction PBS solution+dextran 5% w/v) solution. The Trypan Blue test was also applied before freezing and after thawing each cell sample to estimate the recovery of membrane integrity after thermal treatment, and correlate this datum with spectroscopic results. By following the temperature evolution of two different spectral components (the libration and bending combination mode νc(H2O) at 2000-2500 cm(-1), and the methylene symmetric stretching vibration νsym(CH2) at about 2850 cm(-1)) in the -120÷28°C range, we evidenced the main transition of lipid membrane in connection with cell dehydration, as induced by ice formation in the extracellular medium. In particular, in DMSO/PBS and CryoSure samples we observed a transition to a more rigid state of the lipid membrane together with an increased amount of non-freezable water in the extracellular medium; these results are connected to the role of DMSO as a cryoprotective agent irrespective of the nature of cell type.

Bronchoscopic debulking for endobronchial malignancy: Predictors of recanalization and recurrence

Background

Central airway obstruction related to endobronchial malignancy is one of the most difficult oncological complications and requires efficient palliative intervention.

Methods

Fifty-three consecutive patients with unresectable endobronchial malignancy receiving bronchoscopic cryotherapy as palliative treatment were retrospectively reviewed. Efficiency was evaluated by the improvement of performance status (PS), and the best achievement of tumor removal was assessed as complete or partial removal.

Result

Patients’ PS after cryotherapeutic tumor removal improved from the baseline PS (P = 0.006). In multivariate logistic regression analysis, the compression part of the tumor (odds ratio [OR] 0.42; 95% confidence interval [CI] 0.23∼0.75, P = 0.004) and the thin tumor stalk (OR 87.86; 95% CI 2.31∼3337.37, P = 0.016) were independent predictors of complete tumor removal. Tumors larger than 9.3 cm, including compression and invasion parts, had the highest odds of being only partially removed (positive predictive value [PPV]: 88.2%, likelihood ratio [LR]+: 10.49); tumors smaller than 9.3 cm were likely to be completely removed (negative predictive value [NPV]: 80.6%, LR−: 0.34). After cryotherapy, re-obstruction was significantly associated with non-squamous cell carcinoma (65.7 vs. 16.7%, P = 0.001) and patients who had longer overall survival (11.7 vs. 1.5 months, P < 0.001). Odds of tumor re-obstruction increased 2.28-fold (PPV: 81.6%, LR+: 2.28) beyond two months; the odds decreased by 81% (NPV: 73.3%, LR−: 0.19) within two months.

Conclusion

Debulking of a tumor using cryotherapy is a useful palliative treatment for endobronchial obstruction secondary to a variety of malignancies.

Hydration Forces Between Lipid Bilayers: A Theoretical Overview and a Look on Methods Exploring Dehydration

Although, many biological systems fulfil their functions under the condition of excess hydration, the behaviour of bound water as well as the processes accompanying dehydration are nevertheless important to investigate. Dehydration can be a result of applied mechanical pressure, lowered humidity or cryogenic conditions. The effort required to dehydrate a lipid membrane at relatively low degree of hydration can be described by a disjoining pressure which is called hydration pressure or hydration force. This force is short-ranging (a few nm) and is usually considered to be independent of other surface forces, such as ionic or undulation forces. Different theories were developed to explain hydration forces that are usually not consistent with each other and which are also partially in conflict with experimental or numerical data.Over the last decades it has been more and more realised that one experimental method alone is not capable of providing much new insight into the world of such hydration forces. Therefore, research requires the comparison of results obtained from the different methods. This chapter thus deals with an overview on the theory of hydration forces, ranging from polarisation theory to protrusion forces, and presents a selection of experimental techniques appropriate for their characterisation, such as X-ray diffraction, atomic force microscopy and even calorimetry.

Role of cells in freezing-induced cell-fluid-matrix interactions within engineered tissues

During cryopreservation, ice forms in the extracellular space resulting in freezing-induced deformation of the tissue, which can be detrimental to the extracellular matrix (ECM) microstructure. Meanwhile, cells dehydrate through an osmotically driven process as the intracellular water is transported to the extracellular space, increasing the volume of fluid for freezing. Therefore, this study examines the effects of cellular presence on tissue deformation and investigates the significance of intracellular water transport and cell-ECM interactions in freezing-induced cell-fluid-matrix interactions. Freezing-induced deformation characteristics were examined through cell image deformetry (CID) measurements of collagenous engineered tissues embedded with different concentrations of MCF7 breast cancer cells versus microspheres as their osmotically inactive counterparts. Additionally, the development of a biophysical model relates the freezing-induced expansion of the tissue due to the cellular water transport and the extracellular freezing thermodynamics for further verification. The magnitude of the freezing-induced dilatation was found to be not affected by the cellular water transport for the cell concentrations considered; however, the deformation patterns for different cell concentrations were different suggesting that cell-matrix interactions may have an effect. It was, therefore, determined that intracellular water transport during freezing was insignificant at the current experimental cell concentrations; however, it may be significant at concentrations similar to native tissue. Finally, the cell-matrix interactions provided mechanical support on the ECM to minimize the expansion regions in the tissues during freezing.

GMP cryopreservation of large volumes of cells for regenerative medicine: active control of the freezing process

Cryopreservation protocols are increasingly required in regenerative medicine applications but must deliver functional products at clinical scale and comply with Good Manufacturing Process (GMP). While GMP cryopreservation is achievable on a small scale using a Stirling cryocooler-based controlled rate freezer (CRF) (EF600), successful large-scale GMP cryopreservation is more challenging due to heat transfer issues and control of ice nucleation, both complex events that impact success. We have developed a large-scale cryocooler-based CRF (VIA Freeze) that can process larger volumes and have evaluated it using alginate-encapsulated liver cell (HepG2) spheroids (ELS). It is anticipated that ELS will comprise the cellular component of a bioartificial liver and will be required in volumes of ∼2 L for clinical use. Sample temperatures and Stirling cryocooler power consumption was recorded throughout cooling runs for both small (500 μL) and large (200 mL) volume samples. ELS recoveries were assessed using viability (FDA/PI staining with image analysis), cell number (nuclei count), and function (protein secretion), along with cryoscanning electron microscopy and freeze substitution techniques to identify possible injury mechanisms. Slow cooling profiles were successfully applied to samples in both the EF600 and the VIA Freeze, and a number of cooling and warming profiles were evaluated. An optimized cooling protocol with a nonlinear cooling profile from ice nucleation to -60°C was implemented in both the EF600 and VIA Freeze. In the VIA Freeze the nucleation of ice is detected by the control software, allowing both noninvasive detection of the nucleation event for quality control purposes and the potential to modify the cooling profile following ice nucleation in an active manner. When processing 200 mL of ELS in the VIA Freeze-viabilities at 93.4% ± 7.4%, viable cell numbers at 14.3 ± 1.7 million nuclei/mL alginate, and protein secretion at 10.5 ± 1.7 μg/mL/24 h were obtained which, compared well with control ELS (viability -98.1% ± 0.9%; viable cell numbers -18.3 ± 1.0 million nuclei/mL alginate; and protein secretion -18.7 ± 1.8 μg/mL/24 h). Large volume GMP cryopreservation of ELS is possible with good functional recovery using the VIA Freeze and may also be applied to other regenerative medicine applications.

Rationally optimized cryopreservation of multiple mouse embryonic stem cell lines: I--Comparative fundamental cryobiology of multiple mouse embryonic stem cell lines and the implications for embryonic stem cell cryopreservation protocols

The post-thaw recovery of mouse embryonic stem cells (mESCs) is often assumed to be adequate with current methods. However as this publication will show, this recovery of viable cells actually varies significantly by genetic background. Therefore there is a need to improve the efficiency and reduce the variability of current mESC cryopreservation methods. To address this need, we employed the principles of fundamental cryobiology to improve the cryopreservation protocol of four mESC lines from different genetic backgrounds (BALB/c, CBA, FVB, and 129R1 mESCs) through a comparative study characterizing the membrane permeability characteristics and membrane integrity osmotic tolerance limits of each cell line. In the companion paper, these values were used to predict optimal cryoprotectants, cooling rates, warming rates, and plunge temperatures, and then these predicted optimal protocols were validated against standard freezing protocols.

A low membrane lipid phase transition temperature is associated with a high cryotolerance of Lactobacillus delbrueckii subspecies bulgaricus CFL1

The mechanisms of cellular damage that lactic acid bacteria incur during freeze-thaw processes have not been elucidated to date. Fourier transform infrared spectroscopy was used to investigate in situ the lipid phase transition behavior of the membrane of Lactobacillus delbrueckii ssp. bulgaricus CFL1 cells during the freeze-thaw process. Our objective was to relate the lipid membrane behavior to membrane integrity losses during freezing and to cell-freezing resistance. Cells were produced by using 2 different culture media: de Man, Rogosa, and Sharpe (MRS) broth (complex medium) or mild whey-based medium (minimal medium commonly used in the dairy industry), to obtain different membrane lipid compositions corresponding to different recovery rates of cell viability and functionality after freezing. The lipid membrane behavior studied by Fourier transform infrared spectroscopy was found to be different according to the cell lipid composition and cryotolerance. Freeze-resistant cells, exhibiting a higher content of unsaturated and cyclic fatty acids, presented a lower lipid phase transition temperature (Ts) during freezing (Ts=-8°C), occurring within the same temperature range as the ice nucleation, than freeze-sensitive cells (Ts=+22°C). A subzero value of lipid phase transition allowed the maintenance of the cell membrane in a relatively fluid state during freezing, thus facilitating water flux from the cell and the concomitant volume reduction following ice formation in the extracellular medium. In addition, the lipid phase transition of freeze-resistant cells occurred within a short temperature range, which could be ascribed to a reduced number of fatty acids, representing more than 80% of the total. This short lipid phase transition could be associated with a limited phenomenon of lateral phase separation and membrane permeabilization. This work highlights that membrane phase transitions occurring during freeze-thawing play a fundamental role in the cryotolerance of Lb. delbrueckii ssp. bulgaricus CFL1 cells.

Cryopreservation and quality control of mouse embryonic feeder cells

Stem cell research is a highly promising and rapidly progressing field inside regenerative medicine. Embryonic stem cells (ESCs), reprogrammed "induced pluripotent" cells (iPS), or lately protein induced pluripotent cells (piPS) share one inevitable factor: mouse embryonic feeder cells (MEFs), which are commonly used for ESC long term culture procedures and colony regeneration. These MEFs originate from different mouse strains, are inactivated by different methods and are differently cryopreserved. Incomprehensibly, there are to date no established quality control parameters for MEFs to insure consistency of ESC experiments and culture. Hence, in this work, we developed a bench-top quality control for embryonic feeder cells. According to our findings, MEFs should be inactivated by irradiation (30Gy) and cryopreserved with optimal 10% DMSO at 1K/min freezing velocity. Thawed cells should be free of mycoplasma and should have above 85 ± 13.1% viability. Values for the metabolic activity should be above 150 ± 10.5% and for the combined gene expression of selected marker genes above 225 ± 43.8% compared to non-irradiated, cryopreserved controls. Cells matching these criteria can be utilized for at least 12 days for ESC culture without detaching from the culture dish or disruption of the cell layer.

Thermostability of biological systems: fundamentals, challenges, and quantification

This review examines the fundamentals and challenges in engineering/understanding the thermostability of biological systems over a wide temperature range (from the cryogenic to hyperthermic regimen). Applications of the bio-thermostability engineering to either destroy unwanted or stabilize useful biologicals for the treatment of diseases in modern medicine are first introduced. Studies on the biological responses to cryogenic and hyperthermic temperatures for the various applications are reviewed to understand the mechanism of thermal (both cryo and hyperthermic) injury and its quantification at the molecular, cellular and tissue/organ levels. Methods for quantifying the thermophysical processes of the various applications are then summarized accounting for the effect of blood perfusion, metabolism, water transport across cell plasma membrane, and phase transition (both equilibrium and non-equilibrium such as ice formation and glass transition) of water. The review concludes with a summary of the status quo and future perspectives in engineering the thermostability of biological systems.

Membrane Stability during Biopreservation of Blood Cells

SUMMARY: Storage methods, which can be taken into consideration for red blood cells and platelets, include liquid storage, cryopreservation and freeze-drying. Red blood cells can be hypothermically stored at refrigerated temperatures, whereas platelets are chilling sensitive and therefore cannot be stored at temperatures below 20 °C. Here we give an overview of available cryopreservation and freeze-drying procedures for blood cells and discuss the effects of these procedures on cells, particularly on cellular membranes. Cryopreservation and freeze-drying may result in chemical and structural modifications of cellular membranes. Membranes undergo phase and permeability changes during freezing and drying. Cryo- and lyoprotective agents prevent membrane damage by different mechanisms. Cryoprotective agents are preferentially excluded from membrane surfaces. They decrease the activation energy for water transport during freezing and control the rate of cellular dehydration. Lyoprotectants are thought to stabilize membranes during drying by forming direct hydrogen bonding interactions with phospholipid head groups. In addition, lyoprotectants can form a glassy state at room temperature. Recently liposomes have been investigated to stabilize blood cells during freezing and freeze-drying. Liposomes modify the composition of cellular membranes by lipid and cholesterol transfer, which can stabilize or destabilize the low temperature response of cells.

Membrane permeability parameters for freezing of stallion sperm as determined by Fourier transform infrared spectroscopy

Cellular membranes are one of the primary sites of injury during freezing and thawing for cryopreservation of cells. Fourier transform infrared spectroscopy (FTIR) was used to monitor membrane phase behavior and ice formation during freezing of stallion sperm. At high subzero ice nucleation temperatures which result in cellular dehydration, membranes undergo a profound transition to a highly ordered gel phase. By contrast, low subzero nucleation temperatures, that are likely to result in intracellular ice formation, leave membrane lipids in a relatively hydrated fluid state. The extent of freezing-induced membrane dehydration was found to be dependent on the ice nucleation temperature, and showed Arrhenius behavior. The presence of glycerol did not prevent the freezing-induced membrane phase transition, but membrane dehydration occurred more gradual and over a wider temperature range. We describe a method to determine membrane hydraulic permeability parameters (E(Lp), Lpg) at subzero temperatures from membrane phase behavior data. In order to do this, it was assumed that the measured freezing-induced shift in wavenumber position of the symmetric CH(2) stretching band arising from the lipid acyl chains is proportional to cellular dehydration. Membrane permeability parameters were also determined by analyzing the H(2)O-bending and -libration combination band, which yielded higher values for both E(Lp) and Lpg as compared to lipid band analysis. These differences likely reflect differences between transport of free and membrane-bound water. FTIR allows for direct assessment of membrane properties at subzero temperatures in intact cells. The derived biophysical membrane parameters are dependent on intrinsic cell properties as well as freezing extender composition.

Thermodynamic and structural behaviour of equimolar POPC/CnE4 (n=8, 12, 16) mixtures by sorption gravimetry, 2H NMR spectroscopy and X-ray diffraction

The hydration behaviour of equimolar mixtures of phospholipids and nonionic surfactants with different chain length was investigated by gravimetric sorption, NMR spectroscopy and X-ray diffraction. At the most hydration degrees investigated, the incorporation of nonionic surfactants in a phospholipid bilayer leads to an increase of the hydrophilicity, which can be shown by the presence of excess hydration. The increased hydrophilicity could be explained by the excavation of additional water binding sites due to the "dilution" of the dipole field of the phospholipid bilayer. Another related contribution arises from the increase of the accessible surface area due to the increase of gauche conformers that result from the steric mismatch when surfactants are incorporated into the phospholipid matrix. (2)H NMR spectroscopy was used to determine the quadrupolar splitting representing a measure of the order state of water. The swelling behaviour could be assessed by small-angle X-ray diffraction. (31)P NMR spectroscopy was applied for the assignment of phase structures to the respective hydration range.

Frontiers in biotransport: water transport and hydration

Biotransport, by its nature, is concerned with the motions of molecules in biological systems while water remains as the most important and the most commonly studied molecule across all disciplines. In this review, we focus on biopreservation and thermal therapies from the perspective of water, exploring how its molecular motions, properties, kinetic, and thermodynamic transitions govern biotransport phenomena and enable preservation or controlled destruction of biological systems.

Frontiers in Biotransport: Water Transport and Hydration

Biotransport, by its nature, is concerned with the motions of molecules in biological systems while water remains as the most important and the most commonly studied molecule across all disciplines. In this review, we focus on biopreservation and thermal therapies from the perspective of water, exploring how its molecular motions, properties, kinetic, and thermodynamic transitions govern biotransport phenomena and enable preservation or controlled destruction of biological systems.

Cellular biophysics during freezing of rat and mouse sperm predicts post-thaw motility

Though cryopreservation of mouse sperm yields good survival and motility after thawing, cryopreservation of rat sperm remains a challenge. This study was designed to evaluate the biophysics (membrane permeability) of rat in comparison to mouse to better understand the cooling rate response that contributes to cryopreservation success or failure in these two sperm types. In order to extract subzero membrane hydraulic permeability in the presence of ice, a differential scanning calorimeter (DSC) method was used. By analyzing rat and mouse sperm frozen at 5 degrees C/min and 20 degrees C/min, heat release signatures characteristic of each sperm type were obtained and correlated to cellular dehydration. The dehydration response was then fit to a model of cellular water transport (dehydration) by adjusting cell-specific biophysical (membrane hydraulic permeability) parameters L(pg) and E(Lp). A "combined fit" (to 5 degrees C/min and 20 degrees C/min data) for rat sperm in Biggers-Whitten-Whittingham media yielded L(pg) = 0.007 microm min(-1) atm(-1) and E(Lp) = 17.8 kcal/mol, and in egg yolk cryopreservation media yielded L(pg) = 0.005 microm min(-1) atm(-1) and E(Lp) = 14.3 kcal/mol. These parameters, especially the activation energy, were found to be lower than previously published parameters for mouse sperm. In addition, the biophysical responses in mouse and rat sperm were shown to depend on the constituents of the cryopreservation media, in particular egg yolk and glycerol. Using these parameters, optimal cooling rates for cryopreservation were predicted for each sperm based on a criteria of 5%-15% normalized cell water at -30 degrees C during freezing in cryopreservation media. These predicted rates range from 53 degrees C/min to 70 degrees C/min and from 28 degrees C/min to 36 degrees C/min in rat and mouse, respectively. These predictions were validated by comparison to experimentally determined cryopreservation outcomes, in this case based on motility. Maximum motility was obtained with freezing rates between 50 degrees C/min and 80 degrees C/min for rat and at 20 degrees C/min with a sharp drop at 50 degrees C/min for mouse. In summary, DSC experiments on mouse and rat sperm yielded a difference in membrane permeability parameters in the two sperm types that, when implemented in a biophysical model of water transport, reasonably predict different optimal cooling rate outcomes for each sperm after cryopreservation.