Flexible Sono-Piezo Patch for Functional Sweat Gland Repair through Endogenous Microenvironmental Remodeling.

Remodeling the endogenous regenerative microenvironment in wounds is crucial for achieving scarless, functional tissue regeneration, especially the functional recovery of skin appendages such as sweat glands in burn patients. However, current approaches mostly rely on the use of exogenous materials or chemicals to stimulate cell proliferation and migration, while the remodeling of a pro-regenerative microenvironment remains challenging. Herein, we developed a flexible sono-piezo patch (fSPP) that aims to create an endogenous regenerative microenvironment to promote the repair of sweat glands in burn wounds. This patch, composed of multifunctional fibers with embedded piezoelectric nanoparticles, utilized low-intensity pulsed ultrasound (LIPUS) to activate electrical stimulation of the target tissue, resulting in enhanced pro-regenerative behaviors of niche tissues and cells, including peripheral nerves, fibroblasts, and vasculatures. We further demonstrated the effective wound healing and regeneration of functional sweat glands in burn injuries solely through such physical stimulation. This noninvasive and drug-free therapeutic approach holds significant potential for the clinical treatment of burn injuries.

Inhibition Effect of Ti3C2Tx MXene on Ice Crystals Combined with Laser-Mediated Heating Facilitates High-Performance Cryopreservation.

The phenomena of ice formation and growth are of great importance for climate science, regenerative medicine, cryobiology, and food science. Hence, how to control ice formation and growth remains a challenge in these fields and attracts great interest from widespread researchers. Herein, the ice regulation ability of the two-dimensional MXene Ti3C2Tx in both the cooling and thawing processes is explored. Molecularly speaking, the ice growth inhibition mechanism of Ti3C2Tx MXene is ascribed to the formation of hydrogen bonds between functional groups of -O-, -OH, and -F distributed on the surface of Ti3C2Tx and ice/water molecules, which was elucidated by the molecular dynamics simulation method. In the cooling process, Ti3C2Tx can decrease the supercooling degree and inhibit the sharp edge morphology of ice crystals. Moreover, taking advantage of the outstanding photothermal conversion property of Ti3C2Tx, rapid ice melting can be achieved, thus reducing the phenomena of devitrification and ice recrystallization. Based on the ice restriction performance of Ti3C2Tx mentioned above, Ti3C2Tx is applied for cryopreservation of stem-cell-laden hydrogel constructs. The results show that Ti3C2Tx can reduce cryodamage to stem cells induced by ice injury in both the cooling and thawing processes and finally increase the cell viability from 38.4% to 80.9%. In addition, Ti3C2Tx also shows synergetic antibacterial activity under laser irradiation, thus realizing sterile cryopreservation of stem cells. Overall, this work explores the ice inhibition performance of Ti3C2Tx, elucidates the physical mechanism, and further achieves application of Ti3C2Tx in the field of cell cryopreservation.

Ice Inhibition for Cryopreservation: Materials, Strategies, and Challenges.

Cryopreservation technology has developed into a fundamental and important supporting method for biomedical applications such as cell-based therapeutics, tissue engineering, assisted reproduction, and vaccine storage. The formation, growth, and recrystallization of ice crystals are the major limitations in cell/tissue/organ cryopreservation, and cause fatal cryoinjury to cryopreserved biological samples. Flourishing anti-icing materials and strategies can effectively regulate and suppress ice crystals, thus reducing ice damage and promoting cryopreservation efficiency. This review first describes the basic ice cryodamage mechanisms in the cryopreservation process. The recent development of chemical ice-inhibition molecules, including cryoprotectant, antifreeze protein, synthetic polymer, nanomaterial, and hydrogel, and their applications in cryopreservation are summarized. The advanced engineering strategies, including trehalose delivery, cell encapsulation, and bioinspired structure design for ice inhibition, are further discussed. Furthermore, external physical field technologies used for inhibiting ice crystals in both the cooling and thawing processes are systematically reviewed. Finally, the current challenges and future perspectives in the field of ice inhibition for high-efficiency cryopreservation are proposed.

Synergistic Ice Inhibition Effect Enhances Rapid Freezing Cryopreservation with Low Concentration of Cryoprotectants.

Despite recent advances in controlling ice formation and growth, it remains a challenge to design anti-icing materials in various fields from atmospheric to biological cryopreservation. Herein, tungsten diselenide (WSe2)-polyvinyl pyrrolidone (PVP) nanoparticles (NPs) are synthesized through one-step solvothermal route. The WSe2-PVP NPs show synergetic ice regulation ability both in the freezing and thawing processes. Molecularly speaking, PVP containing amides group can form hydrogen bonds with water molecules. At a macro level, the WSe2-PVP NPs show adsorption-inhibition and photothermal conversation effects to synergistically restrict ice growth. Meanwhile, WSe2-PVP NPs are for the first time used for the cryopreservation of human umbilical vein endothelial cell (HUVEC)-laden constructs based on rapid freezing with low concentrations of cryoprotectants (CPAs), the experimental results indicate that a minimal concentration (0.5 mg mL-1) of WSe2-PVP NPs can increase the viabilities of HUVECs in the constructs post cryopreservation (from 55.8% to 83.4%) and the cryopreserved constructs can also keep good condition in vivo within 7 days. Therefore, this work provides a novel strategy to synergistically suppress the formation and growth of the ice crystalsfor the cryopreservation of cells, tissues, or organs.

Residual energy in optical-field-ionized plasmas with the longitudinal motion of electrons included.

The space-charge effect on the residual energy of electrons in optical-field-ionized plasmas is studied in detail by an extended simplified model and the cloud-in-cell simulation, with the longitudinal motion of electrons included. It is found that in moderate conditions the space-charge field can influence the residual energy of electrons effectively by matching the space-charge field with laser pulse. The effect of stimulated Raman scattering on electron temperature is also investigated in detail. Finally, a comparison is made between the results and experimental data.