Thermomechanical responses facilitating survival mechanisms in pronounced supercooled insects.

Cryopreservation can keep the bioactivity of biological specimens in long-term storage, but it is hard to retain the structural integrity due to serious thermomechanical stress during cooling and warming procedures, especially for complex living organisms. Few studies have reported on the thermomechanical stress of biological specimens in a pre-freezing supercooled state, which is a widespread phenomenon in slow-rate freezing cryopreservation. Here, we develop a thermomechanical coupling model to study transient thermal and mechanical fields of supercooled biological specimens experiencing freezing procedures. The results show that cryoprotectant accumulation in insects causes pronounced supercooled phenomena with severe deformation and thermomechanical stress in the initial state of phase transition. However, the loss of freezable water induced that final deformation and stress decrease, which is beneficial to organism survival after freezing. This numerical method is proved to be a guideline for optimizing slow-rate freezing cryopreservation protocols efficiently and economically. These results reveal survival mechanisms of insects with supercooled phenomena after freezing and assist researchers in exploring more valuable cryopreservation methods for biological specimens.

Cellulose Nanocrystals Facilitate Needle-like Ice Crystal Growth and Modulate Molecular Targeted Ice Crystal Nucleation.

Ice nucleators are of crucial and important implications in various fields including chemistry, climate, agriculture, and cryobiology. However, the complicated extract and biocompatibility of ice nucleators remain unresolved, and the mechanism of ice nucleation remains largely unknown. Herein, we show that natural nanocrystalline cellulose materials possess special properties to enhance ice nucleation and facilitate needle-like ice crystal growth. We reveal the molecular level mechanism that the efficient exposure of cellulose hydroxyl groups on (-110) surface leads to faster nucleation of water. We further design chitosan-decorated cellulose nanocrystals to accomplish molecular cryoablation in CD 44 high-expression cells; the cell viability shows more than ∼10 times decrease compared to cryoablation alone and does not show evident systematic toxicity. Collectively, our findings also offer improved knowledge in molecular level ice nucleation, which may benefit multiple research communities and disciplines.

Natural cryoprotectants combinations of l-proline and trehalose for red blood cells cryopreservation.

Cryopreservation of red blood cells (RBCs) holds great potential benefits for supplying transfusion timely in emergencies. Currently, glycerol is the main cryoprotectant permitted in clinical therapy for RBCs cryopreservation, but its broad application is limited by the toxicity and complex deglycerolization process. Successful cryopreservation of RBCs using more effective materials should be studied to reduce freezing damage, increase biocompatibility, and save processing time. Herein, a simple protocol using natural cryoprotectants combinations of l-proline and trehalose attains a low degree of hemolysis (11.2 ±â€¯2.73%) after thawing compared to glycerol. Furthermore, the morphology of RBCs and the activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase maintain well. Further mechanism study shows that l-proline plays an important role in decreasing the freezing points and inhibiting the growth of ice crystal by permeating into cells during the freezing process. While trehalose works as an inhibitor of ice growth in the freezing process and ice recrystallization in the thawing process. This simple l-proline & trehalose combinations protocol is a promising method to replace current time-consuming and labor-intensive cryopreservation methods of RBCs.

Bioinspired materials and technology for advanced cryopreservation.

Cryopreservation can help to meet the demand for biosamples of high medical value. However, it remains difficult to effectively cryopreserve some sensitive cells, tissues, and reproductive organs. A coordinated effort from the perspective of the whole frozen biological system is necessary to advance cryopreservation technology. Animals that survive in cold temperatures, such as hibernators and cold-tolerant insects, offer excellent natural models. Their anti-cold strategies, such as programmed suppression of metabolism and the synthesis of cryoprotectants (CPAs), warrant systematic study. Furthermore, the discovery and synthesis of metabolism-regulating and cryoprotective biomaterials, combined with biotechnological breakthroughs, can also promote the development of cryopreservation. Further advances in the quality and duration of biosample storage inspired by nature will promote the application of cryopreserved biosamples in clinical therapy.

Liquid Helium Enhanced Vitrification Efficiency of Human Bone-Derived Mesenchymal Stem Cells and Human Embryonic Stem Cells.

Stem cells have the capacity to self-renew and differentiate to specialized cells, which are usually sensitive to cryopreservation. Therefore, the cell survival rate of stem cells using common cryopreservation protocol is generally not ideal. High cooling rates are crucial for decreasing the usage of cryoprotectants (CPAs) and promoting the successful vitrification of stem cells. In this study, we adopted liquid helium (LHe) instead of liquid nitrogen (LN2) as the cryogen to achieve high cooling rates for vitrifying stem cells with high viability and complete functions. A numerical model was established to simulate the cooling processes of vitrifying specimens by immersing them in LHe and LN2. The calculated results revealed higher cooling rates when plunging specimens into LHe than into LN2. The high viability of human bone-derived mesenchymal stem cells (hBMSCs) and human embryonic stem cells (hESCs) after vitrifying into LHe also shows the superiority of LHe as the cryogen. Furthermore, considerable cell viability was achieved by vitrification in LHe, even when decreasing the concentrations of CPAs. Additionally, post-vitrification, the cells still maintained high attachment and proliferation efficiency, normal stemness, and multipotential differentiation both for hBMSCs and hESCs. LHe is prospective to be employed as a universal cryogen for vitrification which has a great potential for widespread applications, including bioengineering and clinical medicine.

Magnetic liquid metal loaded nano-in-micro spheres as fully flexible theranostic agents for SMART embolization.

Transcatheter arterial chemoembolization (TACE) has become one of the preferred choices for advanced liver cancer patients. Current clinically used microsphere embolic agents, such as PVA, gelatin, and alginate microspheres, have limited therapeutic efficacy and lack the function of real-time imaging. In this work, we fabricated magnetic liquid metal nanoparticle (Fe@EGaIn NP) loaded calcium alginate (CA) microspheres (denoted as Fe@EGaIn/CA microspheres), which integrate CT/MR dual-modality imaging and photothermal/photodynamic functions of the Fe@EGaIn NP core, as well as embolization and drug-loading functions of CA microspheres. Namely, such nano-in-micro spheres can be used as fully flexible theranostic agents to achieve smart-chemoembolization. It has been confirmed by in vitro and in vivo experiments that Fe@EGaIn/CA microspheres have advantageous morphology, favorable biocompatibility, splendid versatility, and advanced embolic efficacy. Benefiting from these properties, excellent therapeutic efficiency was achieved with a tumor growth-inhibiting value of 100% in tumor-bearing rabbits. As a novel microsphere embolic agent with promising therapeutic efficacy and diagnostic capability, Fe@EGaIn/CA microspheres have shown potential applications in clinical transcatheter arterial chemoembolization. And the preparation strategy presented here provides a generalized paradigm for achieving multifunctional and fully flexible theranostics.

Soft liquid metal nanoparticles achieve reduced crystal nucleation and ultrarapid rewarming for human bone marrow stromal cell and blood vessel cryopreservation.

High warming rates during cryopreservation are crucial and essential for successful vitrification. However, realizing a faster warming rate in low-concentration cryoprotective agents appears to be challenging for conventional warming process through convective heat transfer. Herein, we developed a liquid metal (LM) nanosystem that can act as a spatial source to significantly enhance the warming rates with near-infrared laser irradiation during the warming process. The synthetic Pluronic F127-liquid metal nanoparticles (PLM NPs) displayed multiple performances with uniform particle size, superior photothermal conversion efficiency (52%), repeatable photothermal stability, and low cytotoxicity. Particularly, it is more difficult for the liquid PLM NPs with less surface free energy to form crystal nucleation than other solid NPs such as gold and Fe3O4, which is beneficial for the cooling process during cryopreservation. The viability of human bone marrow-derived mesenchymal stem cells postcryopreservation reached 78±3%, which is threefold higher than that obtained by the conventional warming method (25±6%). Additionally, the cells postcryopreservation maintained their normal attachment, proliferation, surface marker expression, and intact multilineage differentiation properties. Moreover, the results of mouse tails including blood vessel cryopreservation showed a relatively improved intact structure when using PLM NP rewarming compared with the results of conventional warming. The new LM nanosystem provides a universal platform for cryopreservation that is expected to have potential for widespread applications including bioengineering, cell-based medicine, and clinical translation. STATEMENT OF SIGNIFICANCE: In this study, we fabricated soft liquid metal nanoparticles with high photothermal conversion efficiency, repeatable photothermal stability, and low cytotoxicity. Particularly, soft liquid metal nanoparticles with less surface free energy and suppression effects of ice formation were first introduced to mediate cryopreservation. Superior ice-crystallization inhibition is achieved as a result of less crystal nucleation and ultrarapid rewarming during the freezing and warming processes of cryopreservation, respectively. Collectively, cryopreservation of human bone marrow stromal cells (HBMSCs) and mouse tails including blood vessels can be successfully performed using this new nanoplatform, showing great potential in the application of soft nanoparticles in cryopreservation.

Coloration of Liquid-Metal Soft Robots: From Silver-White to Iridescent.

Gallium-based room-temperature liquid metals are becoming increasingly attractive and outstanding candidates for designing soft robots because of their remarkable electrical conductivity, superior flexibility, excellent stability, and low toxicity. However, the color of liquid metals is limited to shiny silver-white with high reflectivity, which is not helpful for camouflage, like that found in natural soft animals such as cephalopods. Herein, a biomimetic chromatic liquid-metal soft robot with tunable structural colors is reported. Colors ranging from white to gold and black appear on the surface of liquid metal when placed on a graphite substrate and mixed with Al foil in an electrolyte solution. A stable liquid-metal functional material with a rainbow-like appearance is realized under the regulation of an electric field. Further composition and structure characterization reveals that it is a nanoscale Ga2O3 film that displays the multicolor characteristic. The nanostructural film indicates that light scattering of Ga2O3 occurs when the liquid metal is on the graphite surface, and thin-film interference triggers iridescence when the liquid metals are subjected to electrolysis, respectively. These results provide a route to create kaleidoscopic and colorful liquid metals, which are expected to have diverse applications, especially in reinforcing soft robot design with intelligent camouflage function.