Desiccation kinetics and biothermodynamics of glass forming trehalose solutions in thin films

Cryopreservation: A Comprehensive Overview, Challenges, and Future Perspectives

Cryopreservation is the most prevalent method of long-term cell preservation. Effective cell cryopreservation depends on freezing, adequate storage, and correct thawing techniques. Recent advances in cryopreservation techniques minimize the cellular damage which occurs while processing samples. This article focuses on the fundamentals of cryopreservation techniques and how they can be implemented in a variety of clinical settings. The article presents a brief description of each of the standard cryopreservation procedures, such as slow freezing and vitrification. Alongside that, the membrane permeating and nonpermeating cryoprotectants are briefly discussed, along with current advancements in the field of cryopreservation and variables influencing the cryopreservation process. The diminution of cryoinjury incurred by the cell via the resuscitation process will also be highlighted. In the end application of cryopreservation techniques in many fields, with a special emphasis on stem cell preservation techniques and current advancements presented. Furthermore, the challenges while implementing cryopreservation and the futuristic scope of the fields are illustrated herein. The content of this review sheds light on various ways to enhance the output of the cell preservation process and minimize cryoinjury while improving cell revival.

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.

Collapse temperature of solutions important for lyopreservation of living cells at ambient temperature

In this study, the collapse temperature was determined using the freeze-drying microscopy (FDM) method for a variety of cell culture medium-based solutions (with 0.05-0.8 M trehalose) that are important for long-term stabilization of living cells in the dry state at ambient temperature (lyopreservation) by freeze-drying. Being consistent with what has been reported in the literature, the collapse temperature of binary water-trehalose solutions was found to be similar to the glass transition temperature (T'(g) approximately -30 degrees C) of the maximally freeze-concentrated trehalose solution (approximately 80 wt% trehalose) during the freezing step of freeze-drying, regardless of the initial concentration of trehalose. However, the effect of the initial trehalose concentration on the collapse temperature of the cell culture medium-based trehalose solutions was identified to be much more significant, particularly when the trehalose concentration is less than 0.2 M (the collapse temperature can be as low as -65 degrees C). We also determined that cell density from 1 to 10 million cells/mL and ice seeding at high subzero temperatures (-4 and -7 degrees C) have negligible impact on the solution collapse temperature. However, ice seeding does significantly affect the ice crystal morphology formed during the freezing step and therefore the drying rate. Finally, bulking agents (mannitol) could significantly affect the collapse temperature only when trehalose concentration is low (<0.2 M). However, improving the collapse temperature by using a high concentration of trehalose might be preferred to the addition of bulking agents in the solutions for freeze-drying of living cells. We further confirmed the applicability of the collapse temperature measured with small-scale (2 microL) samples using the FDM system to freeze-drying of large-scale (1 mL) samples using scanning electron microscopy (SEM) data. Taken together, the results reported in this study should provide useful guidance to the development of optimal freeze-drying protocols for lyopreservation of living cells at ambient temperature for easy maintenance and convenient wide distribution to end users, which is important to the eventual success of modern cell-based medicine.