Bio-inspired cryo-ink preserves red blood cell phenotype and function during nanoliter vitrification

Usage of ectoine as a cryoprotectant for cryopreservation of lactic acid bacteria

Streptococcus thermophilus, the only Streptococcus species considered "Generally Recognized Safe", has been used widely in the food industry. This bacterium is one of the most valuable industrial lactic acid bacterial species. Due to the importance of this bacterium in industrial applications, it should be stored for a long time without losing its metabolic properties. The present study aimed to investigate the cryoprotectant effect of three compatible solutes (ectoine, trehalose, and sucrose) on bacterial cells stored at different temperatures (frozen at -80 °C or freeze-dried and subsequently stored at +4, -20, and -80 °C) for three months. The bacterial cells were tested for cell viability, bile salt tolerance, and lactic acid production before and after processing. The highest cell viability, bile salt tolerance, and lactic acid production were obtained with ectoine and under frozen (storage at -80 °C) conditions. In freeze-dried and subsequently stored at various temperatures, the best preservation was obtained at -80 °C, followed by -20 °C and +4 °C. Moreover, when ectoine's preservation potential was compared to other cryoprotectants, ectoine showed the highest preservation, followed by trehalose and sucrose. Although ectoine has a variety of qualities that have been proven, in the current work, we have shown for the first time that ectoine has cryoprotectant potential in yogurt starter cultures (S. thermophilus).

Core-Shell Microfiber Encapsulation Enables Glycerol-Free Cryopreservation of RBCs with High Hematocrit

Cryopreservation of red blood cells (RBCs) provides great potential benefits for providing transfusion timely in emergencies. High concentrations of glycerol (20% or 40%) are used for RBC cryopreservation in current clinical practice, which results in cytotoxicity and osmotic injuries that must be carefully controlled. However, existing studies on the low-glycerol cryopreservation of RBCs still suffer from the bottleneck of low hematocrit levels, which require relatively large storage space and an extra concentration process before transfusion, making it inconvenient (time-consuming, and also may cause injury and sample lose) for clinical applications. To this end, we develop a novel method for the glycerol-free cryopreservation of human RBCs with a high final hematocrit by using trehalose as the sole cryoprotectant to dehydrate RBCs and using core-shell alginate hydrogel microfibers to enhance heat transfer during cryopreservation. Different from previous studies, we achieve the cryopreservation of human RBCs at high hematocrit (> 40%) with high recovery (up to 95%). Additionally, the washed RBCs post-cryopreserved are proved to maintain their morphology, mechanics, and functional properties. This may provide a nontoxic, high-efficiency, and glycerol-free approach for RBC cryopreservation, along with potential clinical transfusion benefits.

Out of Box Thinking to Tangible Science: A Benchmark History of 3D Bio-Printing in Regenerative Medicine and Tissues Engineering

Advancements and developments in the 3D bioprinting have been promising and have met the needs of organ transplantation. Current improvements in tissue engineering constructs have enhanced their applications in regenerative medicines and other medical fields. The synergistic effects of 3D bioprinting have brought technologies such as tissue engineering, microfluidics, integrated tissue organ printing, in vivo bioprinted tissue implants, artificial intelligence and machine learning approaches together. These have greatly impacted interventions in medical fields, such as medical implants, multi-organ-on-chip models, prosthetics, drug testing tissue constructs and much more. This technological leap has offered promising personalized solutions for patients with chronic diseases, and neurodegenerative disorders, and who have been in severe accidents. This review discussed the various standing printing methods, such as inkjet, extrusion, laser-assisted, digital light processing, and stereolithographic 3D bioprinter models, adopted for tissue constructs. Additionally, the properties of natural, synthetic, cell-laden, dECM-based, short peptides, nanocomposite and bioactive bioinks are briefly discussed. Sequels of several tissue-laden constructs such as skin, bone and cartilage, liver, kidney, smooth muscles, cardiac and neural tissues are briefly analyzed. Challenges, future perspectives and the impact of microfluidics in resolving the limitations in the field, along with 3D bioprinting, are discussed. Certainly, a technology gap still exists in the scaling up, industrialization and commercialization of this technology for the benefit of stakeholders.

Droplet Generation, Vitrification, and Warming for Cell Cryopreservation: A Review

Cryopreservation is currently a key step in translational medicine that could provide new ideas for clinical applications in reproductive medicine, regenerative medicine, and cell therapy. With the advantages of a low concentration of cryoprotectant, fast cooling rate, and easy operation, droplet-based printing for vitrification has received wide attention in the field of cryopreservation. This review summarizes the droplet generation, vitrification, and warming method. Droplet generation techniques such as inkjet printing, microvalve printing, and acoustic printing have been applied in the field of cryopreservation. Droplet vitrification includes direct contact with liquid nitrogen vitrification and droplet solid surface vitrification. The limitations of droplet vitrification (liquid nitrogen contamination, droplet evaporation, gas film inhibition of heat transfer, frosting) and solutions are discussed. Furthermore, a comparison of the external physical field warming method with the conventional water bath method revealed that better applications can be achieved in automated rapid warming of microdroplets. The combination of droplet vitrification technology and external physical field warming technology is expected to enable high-throughput and automated cryopreservation, which has a promising future in biomedicine and regenerative medicine.

Bioactivity profiling of the extremolyte ectoine as a promising protectant and its heterologous production

Ectoine is a compatible solutes that is diffusely dispersed in bacteria and archaea. It plays a significant role as protectant against various external pressures, such as high temperature, high osmolarity, dryness and radiation, in cells. Ectoine can be utilized in cosmetics due to its properties of moisturizing and antiultraviolet. It can also be used in the pharmaceutical industry for treating various diseases. Therefore, strong protection of ectoine creates a high commercial value. Its current market value is approximately US$1000 kg-1. However, traditional ectoine production in high-salinity media causes high costs of equipment loss and wastewater treatment. There is a growing attention to reduce the salinity of the fermentation broth without sacrificing the production of ectoine. Thus, heterologous production of ectoine in nonhalophilic microorganisms may represent the new generation of the industrial production of ectoine. In this review, we summarized and discussed the biological activities of ectoine on cell and human health protection and its heterologous production.

Bioinspired Freeze-Tolerant Soft Materials: Design, Properties, and Applications

In nature, many biological organisms have developed the exceptional antifreezing ability to survive in extremely cold environments. Inspired by the freeze resistance of these organisms, researchers have devoted extensive efforts to develop advanced freeze-tolerant soft materials and explore their potential applications in diverse areas such as electronic skin, soft robotics, flexible energy, and biological science. Herein, a comprehensive overview on the recent advancement of freeze-tolerant soft materials and their emerging applications from the perspective of bioinspiration and advanced material engineering is provided. First, the mechanisms underlying the freeze tolerance of cold-enduring biological organisms are introduced. Then, engineering strategies for developing antifreezing soft materials are summarized. Thereafter, recent advances in freeze-tolerant soft materials for different technological applications such as smart sensors and actuators, energy harvesting and storage, and cryogenic medical applications are presented. Finally, future challenges and opportunities for the rapid development of bioinspired freeze-tolerant soft materials are discussed.

Recent Developments in Cell Shipping Methods

As opposed to remarkable advances in the cell therapy industry, researches reveal inexplicable difficulties associated with preserving and post-thawing cell death. Post cryopreservation apoptosis is a common occurrence that has attracted the attention of scientists to use apoptosis inhibitors. Transporting cells without compromising their survival and function is crucial for any experimental cell-based therapy. Preservation of cells allows the safe transportation of cells between distances and improves quality control testing in clinical and research applications. The vitality of transported cells is used to evaluate the efficacy of transportation strategies. For many decades, the conventional global methods of cell transfer were not only expensive but also challenging and had adverse effects. The first determination of some projects is optimizing cell survival after cryopreservation. The new generation of cryopreservation science wishes to find appropriate and alternative methods for cell transportation to ship viable cells at an ambient temperature without dry ice or in media-filled flasks. The diversity of cell therapies demands new cell shipping methodologies and cryoprotectants. In this review, we tried to summarize novel improved cryopreservation methods and alternatives to cryopreservation with safe and viable cell shipping at ambient temperature, including dry preservation, hypothermic preservation, gel-based methods, encapsulation methods, fibrin microbeads, and osmolyte solution compositions. This article is protected by copyright. All rights reserved.

Hydrogel Microencapsulation Enhances Cryopreservation of Red Blood Cells with Trehalose

Cryopreservation of red blood cells (RBCs) plays a vital role in preserving rare blood and serologic testing, which is essential for clinical transfusion medicine. The main difficulties of the current cryopreservation technique are the high glycerol concentration and the tedious deglycerolization procedure after thawing. In this study, we explored a microencapsulation method for cryopreservation. RBC-hydrogel microcapsules with a diameter of approximately 2.184 ± 0.061 mm were generated by an electrostatic spraying device. Then, 0.7 M trehalose was used as a cryoprotective agent (CPA), and microcapsules were adhered to a stainless steel grid for liquid nitrogen freezing. The results show that compared with the RBCs frozen by cryovials, the recovery of RBCs after microencapsulation is significantly improved, up to a maximum of more than 85%. Additionally, the washing process can be completed using only 0.9% NaCl. After washing, the RBCs maintained their morphology and adenosine 5'-triphosphate (ATP) levels and met clinical transfusion standards. The microencapsulation method provides a promising, referenceable, and more practical strategy for future clinical transfusion medicine.

Cryopreservation of NK and T Cells Without DMSO for Adoptive Cell-Based Immunotherapy

Dimethylsufoxide (DMSO) being universally used as a cryoprotectant in clinical adoptive cell-therapy settings to treat hematological malignancies and solid tumors is a growing concern, largely due to its broad toxicities. Its use has been associated with significant clinical side effects-cardiovascular, neurological, gastrointestinal, and allergic-in patients receiving infusions of cell-therapy products. DMSO has also been associated with altered expression of natural killer (NK) and T-cell markers and their in vivo function, not to mention difficulties in scaling up DMSO-based cryoprotectants, which introduce manufacturing challenges for autologous and allogeneic cellular therapies, including chimeric antigen receptor (CAR)-T and CAR-NK cell therapies. Interest in developing alternatives to DMSO has resulted in the evaluation of a variety of sugars, proteins, polymers, amino acids, and other small molecules and osmolytes as well as modalities to efficiently enable cellular uptake of these cryoprotectants. However, the DMSO-free cryopreservation of NK and T cells remains difficult. They represent heterogeneous cell populations that are sensitive to freezing and thawing. As a result, clinical use of cryopreserved cell-therapy products has not moved past the use of DMSO. Here, we present the state of the art in the development and use of cryopreservation options that do not contain DMSO toward clinical solutions to enable the global deployment of safer adoptively transferred cell-based therapies.

Strong Hydration Ability of Silk Fibroin Suppresses Formation and Recrystallization of Ice Crystals During Cryopreservation

The cryopreservation (CP) of cell/tissue is indispensable in medical science. However, the formation of ice during cooling and ice recrystallization/growth in time of thawing present significant risk of cell/tissue damage upon analysis of CP process. Herein, the natural and biocompatible silk fibroin (SF) with regular hydrophobic and hydrophilic domains, were first employed as a cryoprotectant (CPA), to the CP of human bone-derived mesenchymal stem cells (hBMSCs), which has been routinely cyropreserved for cell-based therapies. Addtion of SF can regulate the formation of ice crystals during cooling process because of its strong hydration ability in the comparation to the cryopreservation medium (CM) without SF. Moreover, the devitrification-induced recrystallization/growth of ice during the thawing process is suppressed. Most importantly, the addition of 10 mg mL^-1 SF can achieve 81.28% cell viability of cryopreserved hBMSCs as similar as those with the addition of 180 mg mL^-1 Ficoll 70 (commercial CPA), and the functions of the cryopreserved hBMSCs are maintained as good as that of the fresh ones. This work is not only significant for meeting the ever-increasing demand of cell therapy, but also trailblazing for designing materials in controlling ice formation and growth during the CP of other cells and tissues.

Dimethyl Sulfoxide-Free Cryopreservation of Human Umbilical Cord Mesenchymal Stem Cells Based on Zwitterionic Betaine and Electroporation

The effective cryopreservation of mesenchymal stem cells (MSCs) is indispensable to the operation of basic research and clinical transplantation. The prevalent protocols for MSC cryopreservation utilize dimethyl sulfoxide (DMSO), which is easily permeable and able to protect MSCs from cryo-injuries, as a primary cryoprotectant (CPA). However, its intrinsic toxicity and adverse effects on cell function remain the bottleneck of MSC cryopreservation. In this work, we cryopreserved human umbilical cord mesenchymal stem cells (UCMSCs) using zwitterionic betaine combined with electroporation without any addition of DMSO. Betaine was characterized by excellent compatibility and cryoprotective properties to depress the freezing point of pure water and balance the cellular osmotic stress. Electroporation was introduced to achieve intracellular delivery of betaine, intending to further provide comprehensive cryoprotection on UCMSCs. Compared with DMSO cryopreservation, UCMSCs recovered from the protocol we developed maintained the normal viability and functions and reduced the level of reactive oxygen species (ROS) that are harmful to cell metabolism. Moreover, the in vivo distribution of thawed UCMSCs was consistent with that of fresh cells monitored by a bioluminescence imaging (BLI) system. This work opens a new window of opportunity for DMSO-free MSC cryopreservation using zwitterionic compounds like betaine combined with electroporation.

Biophysical and rheological biomarkers of red blood cell physiology and pathophysiology

PURPOSE OF REVIEW

This review summarizes the significant biophysical and rheological aspects of red blood cell physiology and pathophysiology in relation to recent advances in microfluidic biomarker assays and emerging targeted or curative intent therapies.

RECENT FINDINGS

Alterations in red cell biophysical properties and blood rheology have been associated with numerous hematologic and circulatory disorders. Recent advances in biomarker assays enable effective assessment of these biophysical and rheological properties in normoxia or physiological hypoxia in a clinically meaningful way. There are emerging targeted or curative therapies that aim to improve red cell pathophysiology, especially in the context of inherited hemoglobin disorders, such as sickle cell disease.

SUMMARY

Red cell pathophysiology can be therapeutically targeted and the improvements in membrane and cellular biophysics and blood rheology can now be feasibly assessed via new microfluidic biomarker assays. Recent advances provide a new hope and novel treatment options for major red cell ailments, including inherited hemoglobin disorders, membrane disorders, and other pathologies of the red cell, such as malaria.

Janus Vitrification of Droplet via Cold Leidenfrost Phenomenon

Janus particles with asymmetric crystals show great importance in optoelectronics and photocatalysis, but their synthesis usually requires complicated procedures. Here, an unexpected Janus vitrification phenomenon is observed in a droplet caused by the Leidenfrost effect at a cryogenic temperature, which is commonly regarded as symmetric. The Leidenfrost phenomenon levitates the droplet when it comes in contact with liquid nitrogen causing different cooling conditions on the droplet's top and bottom surfaces. It induces asymmetric crystallization in the droplet, forming a Janus vitrified particle with an asymmetric crystallization borderline after cooling, as further evidenced by cryotransmission electron microscopy (cryo-TEM) experiments. Theoretical analysis and experimental study indicate that the position of the asymmetric crystallization borderline is determined by the droplet radius and density, and the observation window of asymmetric crystallization borderline is determined by the chemical concentration. The finding reveals the asymmetric crystallization phenomenon in droplet vitrification for the first time, and provides a new insight for creating Janus particles through the Leidenfrost phenomenon.

Advanced Biotechnology for Cell Cryopreservation

Cell cryopreservation has evolved as an important technology required for supporting various cell-based applications, such as stem cell therapy, tissue engineering, and assisted reproduction. Recent times have witnessed an increase in the clinical demand of these applications, requiring urgent improvements in cell cryopreservation. However, cryopreservation technology suffers from the issues of low cryopreservation efficiency and cryoprotectant (CPA) toxicity. Application of advanced biotechnology tools can significantly improve post-thaw cell survival and reduce or even eliminate the use of organic solvent CPAs, thus promoting the development of cryopreservation. Herein, based on the different cryopreservation mechanisms available, we provide an overview of the applications and achievements of various biotechnology tools used in cell cryopreservation, including trehalose delivery, hydrogel-based cell encapsulation technique, droplet-based cell printing, and nanowarming, and also discuss the associated challenges and perspectives for future development.

Numerical solution of inward solidification of a dilute ternary solution towards a semi-permeable spherical cell

Modeling a cell's response to encroaching ice has informed the development of cryopreservation protocols for four decades. It has been well documented that knowledge of the cellular state as a function of media and cooling rate faciliate informed cryopreservation protocol design and explain mechanisms of damage. However, previous efforts have neglected the interaction between solutes and the encroaching ice front and their effects on the cell state. To address this, here we examine the cryobiologically relevant setting of a spherically-symmetric model of a biological cell separated by a ternary fluid mixture from an encroaching solid-liquid interface. The cell and liquid regions contain cell membrane impermeable intracellular and extracellular salts, respectively, a cell membrane permeable solute commonly used in cryopreservation protocols known as a cryoprotective agent (CPA), and water as a membrane permeable solvent. As cooling and solidification proceed the extracellular chemical environment evolves and leads to mass transport across the cell membrane. Consequently, both the solidification front and the cell membrane are free boundaries whose dynamics are coupled through transport processes in the solid, liquid and cell regions. We describe a numerical procedure to solve this coupled free-boundary problem based on a domain transformation and method of lines approach. We also investigate how the thermal and chemical states inside the cell are influenced by different cooling protocols at the external boundary. Finally, we observe that the previously unaccounted-for partial solute rejection at the advancing solid-liquid interface increases the CPA and salt concentrations in the extracellular liquid as a function of the interface speed and segregation coefficients, suggesting that previous model predictions of the cell state during cryopreservation were inaccurate.

Bulk Droplet Vitrification: An Approach to Improve Large-Scale Hepatocyte Cryopreservation Outcome

Loss of hepatocyte viability and metabolic function after cryopreservation is still a major issue. Although vitrification is a promising alternative, it has generally been proven to be unsuitable for vitrification of large cell volumes which is required for clinical applications. Here, we propose a novel bulk droplet (3-5 mm diameter) vitrification method which allows high throughput volumes (4 mL/min), while using a low preincubated CPA concentration (15% v/v) to minimize toxicity and loss of cell viability and function. We used rapid (1.25 s) osmotic dehydration to concentrate a low preincubated intracellular CPA concentration ahead of vitrification, without the need of fully equilibrating toxic CPA concentrations. We compared direct postpreservation viability, long-term viability, and metabolic function of bulk droplet vitrified, cryopreserved, and fresh hepatocytes. Simulations and cooling rate measurements confirmed an adequate concentration of the intracellular CPA concentration (up to 8.53 M) after dehydration in combination with high cooling rates (960-1320 °C/min) for successful vitrification. In comparison to cryopreserved hepatocytes, bulk droplet vitrified hepatocytes had a significantly higher viability, directly after preservation and after 1 day in culture. Moreover, bulk droplet vitrified hepatocytes had evidently better morphology and showed significantly higher metabolic activity than cryopreserved hepatocytes in long-term collagen sandwich cultures. In conclusion, we developed a novel bulk droplet vitrification method of which we validated the theoretical background and demonstrated the feasibility to use this method to vitrify large cell volumes. Moreover, we showed that this method results in improved hepatocyte viability and metabolic function as compared to cryopreservation.

Bioinspired Preservation of Natural Killer Cells for Cancer Immunotherapy

The ability to cryopreserve natural killer (NK) cells has a significant potential in modern cancer immunotherapy. Current cryopreservation protocols cause deterioration in NK cell viability and functionality. This work reports the preservation of human cytokine-activated NK cell viability and function following cryopreservation using a cocktail of biocompatible bioinspired cryoprotectants (i.e., dextran and carboxylated ε-poly-L-lysine). Results demonstrate that the recovered NK cells after cryopreservation and rewarming maintain their viability immediately after thawing at a comparable level to control (dimethyl sulfoxide-based cryopreservation). Although, their viability drops in the first day in culture compared to controls, the cells grow back to a comparable level to controls after 1 week in culture. In addition, the anti-tumor functional activity of recovered NK cells demonstrates higher cytotoxic potency against leukemia cells compared to control. This approach presents a new direction for NK cell preservation, focusing on function and potentially enabling storage and distribution for cancer immunotherapy.

To Protect and to Preserve: Novel Preservation Strategies for Extracellular Vesicles

Extracellular vesicles (EVs)-based therapeutics are based on the premise that EVs shed by stem cells exert similar therapeutic effects and these have been proposed as an alternative to cell therapies. EV-mediated delivery is an effective and efficient system of cell-to-cell communication which can confer therapeutic benefits to their target cells. EVs have been shown to promote tissue repair and regeneration in various animal models such as, wound healing, cardiac ischemia, diabetes, lung fibrosis, kidney injury, and many others. Given the unique attributes of EVs, considerable thought must be given to the preservation, formulation and cold chain strategies in order to effectively translate exciting preclinical observations to clinical and commercial success. This review summarizes current understanding around EV preservation, challenges in maintaining EV quality, and also bioengineering advances aimed at enhancing the long-term stability of EVs.

Bioinks for 3D bioprinting: an overview

Bioprinting is an emerging technology with various applications in making functional tissue constructs to replace injured or diseased tissues. It is a relatively new approach that provides high reproducibility and precise control over the fabricated constructs in an automated manner, potentially enabling high-throughput production. During the bioprinting process, a solution of a biomaterial or a mixture of several biomaterials in the hydrogel form, usually encapsulating the desired cell types, termed the bioink, is used for creating tissue constructs. This bioink can be cross-linked or stabilized during or immediately after bioprinting to generate the final shape, structure, and architecture of the designed construct. Bioinks may be made from natural or synthetic biomaterials alone, or a combination of the two as hybrid materials. In certain cases, cell aggregates without any additional biomaterials can also be adopted for use as a bioink for bioprinting processes. An ideal bioink should possess proper mechanical, rheological, and biological properties of the target tissues, which are essential to ensure correct functionality of the bioprinted tissues and organs. In this review, we provide an in-depth discussion of the different bioinks currently employed for bioprinting, and outline some future perspectives in their further development.

Droplet based vitrification for cell aggregates: Numerical analysis

Cell aggregates represent the main format of cells existing in vivo and have been widely used as tissue and disease models in vitro. Nevertheless, the preservation of cell aggregates while maintaining their functionalities for off-the-shelf applications is still challenging. Among various preservation methods, droplet-based vitrification exhibits superior advantages for the cryopreservation of cell aggregates; however, the physical mechanisms underlying droplet-based vitrification of cell aggregate using this method remain elusive. To address this issue, we proposed a voronoi model to construct two-dimensional geometric morphologies of cell aggregates and established a coupled physical model to describe the diffusion, heat transfer and crystallization processes during vitrification. Based on these models, we performed a numerical study on the variation and distribution of cryoprotectant (CPA) concentration, temperature and crystallization in cell aggregates during droplet-based vitrification. The results show that although cell membrane is not an obvious barrier in heat transfer, it affects the diffusion of CPA remarkably as a biologic film and thus the following crystallization in cell aggregates. The effective protection of CPA during vitrification occurs during the initial stage of CPA diffusion, thus a longer CPA loading time does not necessarily lead to significant decrease in crystallization, but rather may induce more toxicity to cells.

Hydrogel Encapsulation Facilitates Rapid-Cooling Cryopreservation of Stem Cell-Laden Core-Shell Microcapsules as Cell-Biomaterial Constructs

Core-shell structured stem cell microencapsulation in hydrogel has wide applications in tissue engineering, regenerative medicine, and cell-based therapies because it offers an ideal immunoisolative microenvironment for cell delivery and 3D culture. Long-term storage of such microcapsules as cell-biomaterial constructs by cryopreservation is an enabling technology for their wide distribution and ready availability for clinical transplantation. However, most of the existing studies focus on cryopreservation of single cells or cells in microcapsules without a core-shell structure (i.e., hydrogel beads). The goal of this study is to achieve cryopreservation of stem cells encapsulated in core-shell microcapsules as cell-biomaterial constructs or biocomposites. To this end, a capillary microfluidics-based core-shell alginate hydrogel encapsulation technology is developed to produce porcine adipose-derived stem cell-laden microcapsules for vitreous cryopreservation with very low concentration (2 mol L-1 ) of cell membrane penetrating cryoprotective agents (CPAs) by suppressing ice formation. This may provide a low-CPA and cost-effective approach for vitreous cryopreservation of "ready-to-use" stem cell-biomaterial constructs, facilitating their off-the-shelf availability and widespread applications.

Ectoine as a promising protective agent in humans and animals

Ectoine is a compatible water molecule-binding solute (osmoprotectant) produced by several bacterial species in response to osmotic stress and unfavourable environmental conditions. This amino acid derivative can accumulate inside cells at high concentrations without interfering with natural processes and can protect the cell against radiation or osmotic stress. This brief review presents the current state of knowledge about the effects of ectoine on animals and focuses on its practical use for enzyme stabilisation, human skin protection, anti-inflammatory treatment, inhibitory effects in neurodegenerative diseases, and other therapeutic potential in human or veterinary medicine.

Bio-inspired solute enables preservation of human oocytes using minimum volume vitrification

The ability to cryopreserve human oocytes has significant potential for fertility preservation. Current cryopreservation methods still suffer from the use of conventional cryoprotectants, such as dimethyl sulphoxide (DMSO), causing loss of viability and function. Such injuries result from the toxicity and high concentration of cryoprotectants, as well as mechanical damage of cells due to ice crystal formation during the cooling and rewarming processes. Here we report the preservation of human oocytes following vitrification using an innovative bio-inspired cryoprotectant integrated with a minimum volume vitrification approach. The results demonstrate that the recovered human oocytes maintained viability following vitrification and rewarming. Moreover, when this approach was used to vitrify mouse oocytes, the recovered oocytes preserved their viability and function following vitrification and rewarming. This bio-inspired approach substitutes DMSO, a well-known toxic cryoprotectant, with ectoine, a non-toxic naturally occurring solute. The bio-inspired vitrification approach has the potential to improve fertility preservation for women undergoing cancer treatment and endangered mammal species.

3-D Microwell Array System for Culturing Virus Infected Tumor Cells

Cancer cells have been increasingly grown in pharmaceutical research to understand tumorigenesis and develop new therapeutic drugs. Currently, cells are typically grown using two-dimensional (2-D) cell culture approaches, where the native tumor microenvironment is difficult to recapitulate. Thus, one of the main obstacles in oncology is the lack of proper infection models that recount main features present in tumors. In recent years, microtechnology-based platforms have been employed to generate three-dimensional (3-D) models that better mimic the native microenvironment in cell culture. Here, we present an innovative approach to culture Kaposi’s sarcoma-associated herpesvirus (KSHV) infected human B cells in 3-D using a microwell array system. The results demonstrate that the KSHV-infected B cells can be grown up to 15 days in a 3-D culture. Compared with 2-D, cells grown in 3-D had increased numbers of KSHV latency-associated nuclear antigen (LANA) dots, as detected by immunofluorescence microscopy, indicating a higher viral genome copy number. Cells in 3-D also demonstrated a higher rate of lytic reactivation. The 3-D microwell array system has the potential to improve 3-D cell oncology models and allow for better-controlled studies for drug discovery.

High-Throughput Non-Contact Vitrification of Cell-Laden Droplets Based on Cell Printing

Cryopreservation is the most promising way for long-term storage of biological samples e.g., single cells and cellular structures. Among various cryopreservation methods, vitrification is advantageous by employing high cooling rate to avoid the formation of harmful ice crystals in cells. Most existing vitrification methods adopt direct contact of cells with liquid nitrogen to obtain high cooling rates, which however causes the potential contamination and difficult cell collection. To address these limitations, we developed a non-contact vitrification device based on an ultra-thin freezing film to achieve high cooling/warming rate and avoid direct contact between cells and liquid nitrogen. A high-throughput cell printer was employed to rapidly generate uniform cell-laden microdroplets into the device, where the microdroplets were hung on one side of the film and then vitrified by pouring the liquid nitrogen onto the other side via boiling heat transfer. Through theoretical and experimental studies on vitrification processes, we demonstrated that our device offers a high cooling/warming rate for vitrification of the NIH 3T3 cells and human adipose-derived stem cells (hASCs) with maintained cell viability and differentiation potential. This non-contact vitrification device provides a novel and effective way to cryopreserve cells at high throughput and avoid the contamination and collection problems.

Engineering cancer microenvironments for in vitro 3-D tumor models

The natural microenvironment of tumors is composed of extracellular matrix (ECM), blood vasculature, and supporting stromal cells. The physical characteristics of ECM as well as the cellular components play a vital role in controlling cancer cell proliferation, apoptosis, metabolism, and differentiation. To mimic the tumor microenvironment outside the human body for drug testing, two-dimensional (2-D) and murine tumor models are routinely used. Although these conventional approaches are employed in preclinical studies, they still present challenges. For example, murine tumor models are expensive and difficult to adopt for routine drug screening. On the other hand, 2-D in vitro models are simple to perform, but they do not recapitulate natural tumor microenvironment, because they do not capture important three-dimensional (3-D) cell-cell, cell-matrix signaling pathways, and multi-cellular heterogeneous components of the tumor microenvironment such as stromal and immune cells. The three-dimensional (3-D) in vitro tumor models aim to closely mimic cancer microenvironments and have emerged as an alternative to routinely used methods for drug screening. Herein, we review recent advances in 3-D tumor model generation and highlight directions for future applications in drug testing.

Deformation of a single mouse oocyte in a constricted microfluidic channel

Single oocyte manipulation in microfluidic channels via precisely controlled flow is critical in microfluidic-based in vitro fertilization. Such systems can potentially minimize the number of transfer steps among containers for rinsing as often performed during conventional in vitro fertilization and can standardize protocols by minimizing manual handling steps. To study shape deformation of oocytes under shear flow and its subsequent impact on their spindle structure is essential for designing microfluidics for in vitro fertilization. Here, we developed a simple yet powerful approach to (i) trap a single oocyte and induce its deformation through a constricted microfluidic channel, (ii) quantify oocyte deformation in real-time using a conventional microscope, and (iii) retrieve the oocyte from the microfluidic device to evaluate changes in their spindle structures. We found that oocytes can be significantly deformed under high flow rates, e.g., 10 μl/min in a constricted channel with a width and height of 50 and 150 μm, respectively. Oocyte spindles can be severely damaged, as shown here by immunocytochemistry staining of the microtubules and chromosomes. The present approach can be useful to investigate underlying mechanisms of oocyte deformation exposed to well-controlled shear stresses in microfluidic channels, which enables a broad range of applications for reproductive medicine.