Trehalose in Biomedical Cryopreservation-Properties, Mechanisms, Delivery Methods, Applications, Benefits, and Problems

Molecular simulation on the interaction between trehalose and asymmetric lipid bilayer mimicking the membrane of human red blood cells

Trehalose is widely acknowledged for its ability to stabilize plasma membranes during dehydration. However, the exact mechanism by which trehalose interacts with lipid bilayers remains presently unclear. In this study, we conducted atomistic molecular dynamic simulations on asymmetric model bilayers that mimic the membrane of human red blood cells at various trehalose and water contents. We considered three different hydration levels mimicking the full hydration to desiccation scenarios. Results indicate that the asymmetric distribution of lipids did not significantly influence the computed structural characteristics at full and low hydration. At dehydration, however, the order parameter obtained from the symmetric bilayer is significantly higher compared to those obtained from asymmetric ones. Analysis of hydrogen bonds revealed that the protective ability of trehalose is well described by the water replacement hypothesis at full and low hydration, while at dehydration other interaction mechanisms associated with trehalose exclusion from the bilayer may involve. In addition, we found that trehalose exclusion is not attributed to sugar saturation but rather to the reduction in hydration levels. It can be concluded that the protective effect of trehalose is not only related to the hydration level of the bilayer, but also closely tied to the asymmetric distribution of lipids within each leaflet.

Microplate-Based Cryopreservation of Adherent-Cultured Human Cell Lines Using Amino Acids and Proteins

With the progression of regenerative medicine and cell therapy, the importance of cryopreservation techniques for cultured cells continues to rise. Traditional cryoprotectants, such as dimethyl sulfoxide and glycerol, are effective in cryopreserving suspended cells, but they do not demonstrate sufficient efficacy for two-dimensional (2D)-cultured cells. In the past decade, small molecules and polymers have been studied as cryoprotectants. Some L-amino acids have been reported to be natural and biocompatible cryoprotectants. However, the cryoprotective effects of D-amino acids have not been investigated for such organized cells. In the present study, the cryoprotective effects of D- and L-amino acids and previously reported cryoprotectants were assessed using HepG2 cells cultured on a microplate without suspending the cells. d-Proline had the highest cryoprotective effect on 2D-cultured cells. The composition of the cell-freezing solution and freezing conditions were then optimized. The d-proline-containing cell-freezing solution also effectively worked for other cell lines. To minimize the amount of animal-derived components, fetal bovine serum in the cell freezing solution was substituted with bovine serum albumin and StemFit (a commercial supplement for stem cell induction). Further investigations on the mechanism of cryopreservation suggested that d-proline protected enzymes essential for cell survival from freeze-induced damage. In conclusion, an effective and xeno-free cell-freezing solution was produced using d-proline combined with dimethyl sulfoxide and StemFit for 2D-cultured cells.

On the universality of viscosity in supersaturated binary aqueous sugar solutions: Cryopreservation by vitrification

Nowadays, the physical nature of supersaturated binary aqueous sugar solutions in the vicinity of the glass transition represents a very important issue due to their biological applications in cryopreservation of cells and tissues, food science and stabilization and storage of nano genetic drugs. We present the construction of the Supplemented Phase Diagram and the non-equilibrium nature of the undersaturated-supersaturated kinetic transition. The description of its thermodynamic nature is achieved through the study of behavior of their viscosity as temperature is lowered and concentration increased. In this work, we find a universal character for the viscosities of several sugar water solutions.

Lyophilization for bacteria preservation: a promising approach for Yersinia pestis strains from an unique collection in Brazil (Fiocruz-CYP)

Yersinia pestis, the causative agent of plague, is a highly virulent bacterium that poses a significant threat to human health. Preserving this bacterium in a viable state is crucial for research and diagnostic purposes. This paper presents and evaluates a simple lyophilization protocol for the long-term storage of Y. pestis strains from Fiocruz-CYP, aiming to explore its impact on viability and long-term stability, while replacing the currently used methodologies. The lyophilization tests were conducted using the non-virulent Y. pestis strain EV76, subjected to the lyophilization process under vacuum conditions. Viability assessment was performed to evaluate the effects of lyophilization and storage conditions on Y. pestis under multiple temperature conditions (- 80 °C, - 20 °C, 4-8 °C and room temperature). The lyophilization protocol employed in this study consistently demonstrated its efficacy in maintaining high viability rates for Y. pestis samples in a up to one year follow-up. The storage temperature that consistently exhibited the highest recovery rates was - 80 °C, followed by - 20 °C and 4-8 °C. Microscopic analysis of the post-lyophilized cultures revealed preserved morphological features, consistent with viable bacteria. The high viability rates observed in the preserved samples indicate the successful preservation of Y. pestis using this protocol. Overall, the presented lyophilization protocol provides a valuable tool for the long-term storage of Y. pestis, offering stability, viability, and functionality. By refining the currently used methods of lyophilization, this protocol can improve long-term preservation for Y. pestis strains collections, facilitating research efforts, diagnostic procedures, and the development of preventive and therapeutic strategies against plague.

Advances in Cryopreservatives: Exploring Safer Alternatives

Cryopreservation of cells, tissues, and organs is widely used in the biomedical and research world. There are different cryopreservatives that are used for this process; however, many of them, such as DMSO, are used despite the problems they present, mainly due to the toxicity it presents to certain types of samples. The aim of this Review is to highlight the different types of substances used in the cryopreservation process. It has been shown that some of these substances are well-known, as in the case of the families of alcohols, sugars, sulfoxides, etc. However, in recent years, other compounds have appeared, such as ionic liquids, deep eutectic solvents, or certain polymers, which open the door to new cryopreservation methods and are also less toxic to frozen samples.

Establishment of a Practical Sperm Cryopreservation Pathway for the Axolotl (Ambystoma mexicanum): A Community-Level Approach to Germplasm Repository Development

The axolotl (Ambystoma mexicanum) draws great attention around the world for its importance as a biomedical research model, but housing and maintaining live animals is increasingly expensive and risky as new transgenic lines are developed. The goal of this work was to develop an initial practical pathway for sperm cryopreservation to support germplasm repository development. The present study assembled a pathway through the investigation of axolotl sperm collection by stripping, refrigerated storage in various osmotic pressures, cryopreservation in various cryoprotectants, and in vitro fertilization using thawed sperm. By the stripping of males, 25-800 µL of sperm fluid was collected at concentrations of 1.6 × 106 to 8.9 × 107 sperm/mL. Sperm remained motile for 5 d in Hanks' Balanced Salt Solution (HBSS) at osmolalities of 100-600 mOsm/kg. Sperm cryopreserved in 0.25 mL French straws at 20 °C/min in a final concentration of 5% DMFA plus 200 mM trehalose and thawed at 25 °C for 15 s resulted in 52 ± 12% total post-thaw motility. In six in vitro fertilization trials, 20% of eggs tested with thawed sperm continued to develop to stage 7-8 after 24 h, and a third of those embryos (58) hatched. This work is the first report of successful production of axolotl offspring with cryopreserved sperm, providing a general framework for pathway development to establish Ambystoma germplasm repositories for future research and applications.

Osmolytes as Cryoprotectants under Salt Stress

Cryoprotecting agent (CPA)-guided preservation is essential for effective protection of cells from cryoinjuries. However, current cryoprotecting technologies practiced to cryopreserve cells for biomedical applications are met with extreme challenges due to the associated toxicity of CPAs. Because of these limitations of present CPAs, the quest for nontoxic alternatives for useful application in cell-based biomedicines has been attracting growing interest. Toward this end, here, we investigate naturally occurring osmolytes' scope as biocompatible cryoprotectants under cold stress conditions in high-saline medium. Via a combination of the simulation and experiment on charged silica nanostructures, we render first-hand evidence that a pair of archetypal osmolytes, glycine and betaine, would act as a cryoprotectant by restoring the indigenous intersurface electrostatic interaction, which had been a priori screened due to the cold effect under salt stress. While these osmolytes' individual modes of action are sensitive to subtle chemical variation, a uniform augmentation in the extent of osmolytic activity is observed with an increase in temperature to counter the proportionately enhanced salt screening. The trend as noted in inorganic nanostructures is found to be recurrent and robustly transferable in a charged protein interface. In hindsight, our observation justifies the sufficiency of the reduced requirement of osmolytes in cells during critical cold conditions and encourages their direct usage and biomimicry for cryopreservation.

Trehalose Production Using Three Extracellular Enzymes Produced via One-Step Fermentation of an Engineered Bacillus subtilis Strain

At present, the double-enzyme catalyzed method using maltooligosyltrehalose synthase (MTSase) and maltooligosyltrehalose trehalohydrolase (MTHase) is the mainstream technology for industrial trehalose production. However, MTSase and MTHase are prepared mainly using the heterologous expression in the engineered Escherichia coli strains so far. In this study, we first proved that the addition of 3 U/g neutral pullulanase PulA could enhance the trehalose conversion rate by 2.46 times in the double-enzyme catalyzed system. Then, a CBM68 domain was used to successfully assist the secretory expression of MTSase and MTHase from Arthrobacter ramosus S34 in Bacillus subtilis SCK6. At the basis, an engineered strain B. subtilis PSH02 (amyE::pulA/pHT43-C68-ARS/pMC68-ARH), which co-expressed MTSase, MTHase, and PulA, was constructed. After the 24 h fermentation of B. subtilis PSH02, the optimum ratio of the extracellular multi-enzymes was obtained to make the highest trehalose conversion rate of 80% from 100 g/L maltodextrin. The high passage stability and multi-enzyme preservation stability made B. subtilis PSH02 an excellent industrial production strain. Moreover, trehalose production using these extracellular enzymes produced via the one-step fermentation of B. subtilis PSH02 would greatly simplify the procedure for multi-enzyme preparation and be expected to reduce production costs.