Mesenchymal Migration on Adhesive-Nonadhesive Alternate Surfaces in Macrophages.

Mesenchymal migration usually happens on adhesive substrates, while cells adopt amoeboid migration on low/nonadhesive surfaces. Protein-repelling reagents, e.g., poly(ethylene) glycol (PEG), are routinely employed to resist cell adhering and migrating. Contrary to these perceptions, this work discovers a unique locomotion of macrophages on adhesive-nonadhesive alternate substrates in vitro that they can overcome nonadhesive PEG gaps to reach adhesive regions in the mesenchymal mode. Adhering to extracellular matrix regions is a prerequisite for macrophages to perform further locomotion on the PEG regions. Podosomes are found highly enriched on the PEG region in macrophages and support their migration across the nonadhesive regions. Increasing podosome density through myosin IIA inhibition facilitates cell motility on adhesive-nonadhesive alternate substrates. Moreover, a developed cellular Potts model reproduces this mesenchymal migration. These findings together uncover a new migratory behavior on adhesive-nonadhesive alternate substrates in macrophages.

Molecular Resolution Mapping of Erythrocyte Cytoskeleton by Ultrastructure Expansion Single-Molecule Localization Microscopy.

The combination of expansion microscopy and single-molecule localization microscopy has the potential to approach the molecular resolution. However, this combination meets challenges due to the hydrogel shrinkage in the presence of imaging buffer. Here, a method of ultrastructure expansion single-molecule localization microscopy (U-ExSMLM) based on skillfully adhering the gel onto poly-l-lysine (pLL)-coated coverslip is developed to prevent lateral shrinkage of the hydrogel. U-ExSMLM is then applied to dissect the membrane cytoskeleton organization of human erythrocytes at molecular resolution. The resolved nanoscale spatial distributions of cytoskeleton proteins, including the N/C-termini of ß-spectrin, protein 4.1, and tropomodulin, show good agreement with the acknowledged model of erythrocyte cytoskeleton structure, demonstrating the reliability of U-ExSMLM. Furthermore, the concentration of pLL is adjusted to preserve the physiological biconcave morphology of erythrocytes, and it is found that the spectrin cytoskeleton in the dimple regions has lower density and larger length than that in the rim regions, which provides the direct evidence for cytoskeleton asymmetry in human erythrocytes. Therefore, the integrated method offers future opportunities to study the ultrastructure of membrane cytoskeleton at molecular resolution.

Development of a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel.

Gelatin-based bioadhesives are suitable for the treatment of wounds due to their inherent biocompatibility, lack of immunogenicity, and potential for modification. However, common limitations with such adhesives include their adhesive strength and versatility. In the present study, a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel (DNGel) was engineered using facile dual-syringe methodology. An integrative crosslinking strategy utilized the complexation of catechol-Fe3+ and NIPAAm-methacryloyl. As anticipated, the DNGel exhibited multifunctional therapeutic properties, namely temperature-sensitivity, mechanical flexibility, good adhesive strength, injectability, self-healing capability, antibacterial activity, and the capability to enable hemostasis and wound healing. The bioinspired dynamic double-network was stabilized by a number of molecular interactions between components in the DNGel, providing multifunctional therapeutic performance. In addition, comprehensive in vitro and in vivo testing confirmed that the adhesive hydrogel exhibited effective antihemorrhagic properties and accelerated wound healing by the promotion of revascularization, representing considerable potential as a next-generation multifunctional smart adhesive patch.

Skin-inspired gelatin-based flexible bio-electronic hydrogel for wound healing promotion and motion sensing.

Next generation tissue-engineered skin scaffolds promise to provide sensory restoration through electrical stimulation in addition to effectively rebuilding and repairing skin. The integration of real-time monitoring of the injury motion activities can fundamentally improve the therapeutic efficacy by providing detailed data to guide the clinical practice. Herein, a mechanically-flexible, electroactive, and self-healable hydrogels (MESGel) was engineered for the combinational function of electrically-stimulated accelerated wound healing and motion sensing. MESGel shows outstanding biocompatibility and multifunctional therapeutic properties including flexibility, self-healing characteristics, biodegradability, and bioelectroactivity. Moreover, MESGel shows its potential of being a novel flexible electronic skin sensor to record the injury motion activities. Comprehensive in vitro and in vivo experiments prove that MESGel can facilitate effective electrical stimulation, actively promoting proliferation in Chinese hamster lung epithelial cells and therefore can accelerate favorable epithelial biology during skin wound healing, demonstrating an effective therapeutic strategy for a full-thickness skin defect model and leading to new-type flexible bioelectronics.

Spider-Web and Ant-Tentacle Doubly Bio-Inspired Multifunctional Self-Powered Electronic Skin with Hierarchical Nanostructure.

For the practical applications of wearable electronic skin (e-skin), the multifunctional, self-powered, biodegradable, biocompatible, and breathable materials are needed to be assessed and tailored simultaneously. Integration of these features in flexible e-skin is highly desirable; however, it is challenging to construct an e-skin to meet the requirements of practical applications. Herein, a bio-inspired multifunctional e-skin with a multilayer nanostructure based on spider web and ant tentacle is constructed, which can collect biological energy through a triboelectric nanogenerator for the simultaneous detection of pressure, humidity, and temperature. Owing to the poly(vinyl alcohol)/poly(vinylidene fluoride) nanofibers spider web structure, internal bead-chain structure, and the collagen aggregate nanofibers based positive friction material, e-skin exhibits the highest pressure sensitivity (0.48 V kPa-1 ) and high detection range (0-135 kPa). Synchronously, the nanofibers imitating the antennae of ants provide e-skin with short response and recovery time (16 and 25 s, respectively) to a wide humidity range (25-85% RH). The e-skin is demonstrated to exhibit temperature coefficient of resistance (TCR = 0.0075 °C-1 ) in a range of the surrounding temperature (27-55 °C). Moreover, the natural collagen aggregate and the all-nanofibers structure ensure the biodegradability, biocompatibility, and breathability of the e-skin, showing great promise for practicability.

Feasibility Study of Gelatin Preparation from the Bioinspired Collagen Aggregates by a "Two-step" Facile Degradation Method.

Gelatin is the putative research hotspot of natural products, but gelatin prepared by traditional alkali methods has seriously affected its applications due to the worryingly low molecular weight and poor gel strength. Herein, we took the lead to extract the distinct gelatin from a kind of bioinspired collagen aggregate (CA) by a two-step controlled degradation method. Structural analysis suggested that the CA better preserves the natural aggregated structure of nature collagen (typical D-periodic cross-striated pattern). Compared with the gelatin gelatinized by the conventional alkali method (G-Al) and commercial gelatin (CG), the gelatin (G-CA) from CA had a wide molecular weight distribution range, high transparency, high viscosity, and strong gel strength as expected. Meanwhile, the G-CA film exhibited better mechanical performance and thermostability than CG and G-Al films, and water vapor permeability was also higher in the G-CA film, whereas water solubility was higher in the CG and G-Al films. Thus, the G-CA film is more conducive to the use of food packaging or edible films, exhibiting more potential market application prospects. Notably, G-CA based on CA from waste hide offal provides a way to reuse leather waste resources and further realize green and clean production in leather industry.

Thermoresponsive Hemostatic Hydrogel with a Biomimetic Nanostructure Constructed from Aggregated Collagen Nanofibers.

Uncontrollable bleeding poses considerable fatality risks by large-volume blood losses. Current emergency antibleeding handlings including either compression with gauze or "passive" blood transfusion are thus far from ideal, while most recently developed hemostatic agents still share common limitations without considering the subsequent tissue repairing and antibacterial activity after treatment. Herein, we introduce a novel bioinspired aggregated collagen nanofiber-based biocompatible and efficient hemostatic hydrogel material (TS-Gel-Ag-col) prepared by the integration of multifunctional compounds of muco-mimetic poloxamer, polyvinylpyrrolidone, and dencichine/chitosan dialdehyde synergistic crosslinked aggregated collagen nanofibers decorated with silver nanoparticles. Comprehensive material characterization and in vitro and in vivo studies of TS-Gel-Ag-col demonstrate that these materials possess effective antihemorrhagic and antibacterial wound protection effects. Moreover, TS-Gel-Ag-col can facilitate the tissue repairing of skin wounds by promoting revascularization. TS-Gel-Ag-col holds great promise for next-generation collagen-based absorbable hemostatic materials and for the development of smart artificial skins.

Biofabrication and Characterization of Collagens with Different Hierarchical Architectures.

Herein, three categories of collagens with different hierarchical architectures, including collagen molecules (Col), collagen microfibrils (F-col), and collagen fiber bundles (Ag-col), were systematically biofabricated based on the biosynthesis pathway of natural collagen. Their macroscopic properties, that is, physicochemical and biological properties, and hierarchical structures were evaluated synthetically. The results showed that Col had a rigid rod-like fibrous triple helix structure, whereas F-col and Ag-col had the typical D-periodic cross-striated patterns with lengths of about 54 and 60 nm in the longitudinal direction, respectively. We further found that collagens with higher hierarchical structures had more superior thermal stability, mechanical properties, and biodegradability. Among all three collagens, Ag-col was the best: it had the highest bioactivity and hemostatic properties and could better promote cell adhesion, growth, and proliferation and better improve the secretion of growth factors. Overall, we have a reason to believe that collagens with a higher hierarchical structure can serve as a better alternative source of collagenous materials for further applications in biological industries.

Feasibility Study of Tissue Transglutaminase for Self-Catalytic Cross-Linking of Self-Assembled Collagen Fibril Hydrogel and Its Promising Application in Wound Healing Promotion.

Collagen-based bio-hydrogels are undoubtedly a hot spot in the development of biological dressings for wound healing promotion. Herein, glutamine transaminase (TGase), a biological nontoxic cross-linker with high specific activity and reaction rate under mild conditions, was utilized for the self-catalytic cross-linking of the regenerated collagen (COL) fibril hydrogel fabricated through a molecular self-assembly method. The results showed that the natural triple helical conformation of COL remained completely integrated after self-catalytic cross-linking TGase, which was definitively the fundamental for maintaining its superior bioactivity. It was worth noting that TGase could promote the self-assembly process of COL building blocks into a higher order D-period cross-striated structure. Also, the reconstructed TGase cross-linked COL fibrils exhibited a higher degree of interfiber entanglements with more straight and longer fibrils. Meanwhile, the thermal stability of COL was significantly improved after introducing TGase. Besides, the cytocompatibility analysis suggested that the regenerated COL fibril hydrogel showed excellent cell growth activity and proliferation ability when the dosage of TGase is less than 40 U/g. Further, animal experiments indicated that the targeted COL fibril hydrogel could significantly promote skin wound healing, exhibiting better capacity of skin tissue for regeneration than the COL hydrogel untreated as expected. Therefore, the reconstructed TGase cross-linked COL fibril hydrogel could serve as a novel soft material for wound healing promotion.

DNA Melting Analysis with Optofluidic Lasers Based on Fabry-Pérot Microcavity.

We conduct DNA high-resolution melting (HRM) analysis using optofluidic lasers based on a Fabry-Pérot microcavity. Compared to the fluorescence-based HRM, the laser-based HRM has advantages of higher emission intensity for better signal-to-noise ratio and sharper transition for better temperature resolution. In addition, the melting temperature can be lowered by optimizing the laser conditions such as external pump and cavity Q-factor. In this work, we first theoretically analyze the laser-based HRM. Then experiments are performed on three long DNA sequences as model systems, one being 99 bases and the other two being 130 bases long but with different GC contents. We show that the laser-based HRM is able to distinguish the target and the single-base mismatched DNA as long as 130 bases and with nearly 50% GC content. The dependence of laser threshold on the temperature for each DNA sample is first experimentally investigated and by optimizing the external pump, the melting temperature is reduced by more than 10 °C, compared to the fluorescence-based HRM for long DNA sequences up to 130 bases. Finally, we demonstrate an alternative method of using the laser-based HRM for rapid DNA screening that does not exist for the fluorescence-based HRM, in which laser excitation is scanned at a fixed temperature to distinguish the target and the base-mismatched DNA sequences. It is shown that the 130-bases-long DNA with nearly 50% GC content can have as much as 20% difference in the laser threshold and 40% difference in the laser output slope between the target and the single-base mismatched sequences, despite only 0.5 °C difference in their melting temperature, indicating that the laser-excitation-scanning method can also be suitable for long DNA sequences with higher GC content.