Hydrogel Adhesion by Wrinkling Films Kato, Masatoshi; Asoh, Taka‐Aki; Uyama, Hiroshi
Macromolecular rapid communications.,
December 2019, Letnik:
40, Številka:
23
Journal Article
Recenzirano
A novel adhesion control method for hydrogels utilizing swelling‐induced wrinkling gel films is developed. Structures such as flat, crease, and wrinkle at the interface of adhered gels are controlled ...by swelling ratio of gel films. The role of microstructures at the gel–gel interface is investigated by adhesive strength measurement. Aligned wrinkles are fabricated with anisotropic swelling films. The adhesive strength of hydrogels with wrinkles parallel to tensile direction is larger than that with perpendicular wrinkles. Adhered gels detach without damage to their surfaces when the wrinkle structures are disrupted by peeling of the wrinkled film. Moreover, thermoresponsive film is used to control wrinkle structures at the adhered interface by temperature. The adhered interface is stable in cold water because of the existence of wrinkles; however, they detach in hot water due to wrinkle deformation. By using wrinkle structure at adhesive interfaces, both strong adhesion and easy detachment of hydrogels are achieved.
A novel adhesion control for hydrogels utilizing swelling‐induced wrinkling gel films is developed. By using wrinkle structure at adhesive interfaces, both strong adhesion and easy detachment of hydrogels are achieved.
Single-cell analysis by means of vibrational spectroscopy combined with optical trapping is a reliable platform for unveiling cell-to-cell heterogeneities in vast populations. Although infrared (IR) ...vibrational spectroscopy provides rich molecular fingerprint information on biological samples in a label-free manner, its application with optical trapping has never been achieved due to weak gradient forces generated by the diffraction-limited focused IR beam and strong background of water absorption. Herein, we present single-cell IR vibrational analysis that incorporates mid-infrared photothermal (MIP) microscopy with optical trapping. Optically trapped single polymer particles and red blood cells (RBCs) in blood could be chemically identified owing to their IR vibrational fingerprints. This single-cell IR vibrational analysis further allowed us to probe the chemical heterogeneities of RBCs originating from the variation in the intracellular characteristics. Our demonstration paves the way for the IR vibrational analysis of single cells and chemical characterization in various fields.
Single-cell analysis by means of vibrational spectroscopy combined with optical trapping is a reliable platform for unveiling cell-to-cell heterogeneities in vast populations.
Visualizing the spatial distribution of chemical compositions in biological tissues is of great importance to study fundamental biological processes and origin of diseases. Raman microscopy, one of ...the label-free vibrational imaging techniques, has been employed for chemical characterization of tissues. However, the low sensitivity of Raman spectroscopy often requires a long acquisition time of Raman measurement or a high laser power, or both, which prevents one from investigating large-area tissues in a nondestructive manner. In this work, we demonstrated chemical imaging of heart tissues using mid-infrared photothermal (MIP) microscopy that simultaneously achieves the high sensitivity benefited from IR absorption of molecules and the high spatial resolution down to a few micrometers. We successfully visualized the distributions of different biomolecules, including proteins, phosphate-including proteins, and lipids/carbohydrates/amino acids. Further, we experimentally compared MIP microscopy with Raman microscopy to evaluate the sensitivity and photodamage to tissues. We proved that MIP microscopy is a highly sensitive technique for obtaining vibrational information of molecules in a broad fingerprint region, thereby it could be employed for biological and diagnostic applications, such as live-tissue imaging.
Graphical abstract
We developed a novel method for the fabrication of a wrinkle structure on the hydrogel surface in aqueous conditions by the electrophoretic formation of a polyion complex. The wrinkling wavelength ...was controlled by changing the electrophoresis conditions and Young's modulus of the hydrogels. It was possible to prepare the patterned and gradient wrinkle surface by modulating the electrode installation. An active wrinkle on the surface of the thermoresponsive hydrogel could be switched to a flat and wrinkle surface by changing the temperature.
Surface geometries in nature such as wrinkle structures have various functions. Attention has been paid to the fabrication method of the geometry and geometry control by external stimuli. This is ...because surface geometries as an active interface are able to contribute to the control of interactions with the external environment. In this study, aligned wrinkles were fabricated on the surface of stretched hydrogels in aqueous conditions by the electrophoretic formation of a polyion complex layer. The geometry of wrinkles was controlled by the stretching ratio and Young’s modulus of hydrogels, and hierarchical wrinkle structures were fabricated after unloading the stretched hydrogels. Therefore, it can be a new wrinkle-formation method capable of transferring the initial elastic anisotropy of the substrate material to the wrinkle structure. Creation of thermoresponsive wrinkles that can transform their geometrical configuration reversibly was achieved by fabrication of aligned wrinkles on the surface of thermoresponsive hydrogels.
While infrared spectroscopy is a powerful technique that provides molecular information such as chemical constituents and chemical structures of analytes, it suffers from low absorption cross-section ...resulting in low sensitivity and poor signal-to-noise or signal-to-background ratios. Surface-enhanced infrared absorption (SEIRA) spectroscopy, which is supported by nanometer scale structures, is a promising technology to overcome these problems in conventional infrared (IR) spectroscopy and enhances IR signals using the field enhancement properties of surface plasmon resonance. Recently resonant SEIRA technique was proposed, and signal enhancement factor was significantly improved. In this review, we present an overview of the recent progresses on resonant SEIRA technologies including nanoantenna- and metamaterial-based SEIRA, and also SEIRA techniques with nanoimaging capabilities.
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Chemical characterization of polymeric samples, such as blend polymers is a fundamental analytical approach for advancement of polymer science and polymer technologies. Vibrational ...imaging is a promising technique to analyze chemical compositions of materials in a wide range of fields. Raman scattering and infrared (IR) absorption reflect complementary molecular vibrations; therefore, Raman and IR imaging provide rich information of the spatial distributions of chemical compositions of samples, revealing their complicated chemical structures. However, the discrepancy of spatial resolution in Raman and conventional IR imaging makes it difficult to merge these techniques. In the present study, we performed chemical characterization of polymeric samples using Raman and IR imaging enabled by mid-infrared photothermal (MIP) microscopy. The chemical compositions of blend polymer films were visualized based on both Raman scattering and IR absorption with the spatial resolution of the sub-micrometer scale. We found that the varying contrasts in Raman and MIP imaging enabled the investigation of averaged and surface-sensitive compositions of polymer blends. Raman and MIP imaging holds a promise of unique applications in a wide range of current research fields, such as polymers, two-dimensional materials, and biology.
The formation of photosynthetic microbial biofilms comprising multispecies biomolecules, such as extracellular polymeric substances (EPSs), and microbial cells play pivotal roles in maintaining or ...stimulating their biological functions. Although there are numerous studies on photosynthetic microbial biofilms, the spatial distribution of EPS components that are vital for microbial biofilm formation, such as exopolysaccharides and proteins, is not well understood. Visualization of photosynthetic microbial biofilms requires label-free methods, because labelling EPSs results in structural changes or aggregation. Raman spectroscopy is useful for label-free visualization of biofilm constituents based on chemical contrast. However, interference resulting from the bright autofluorescence of photosynthetic molecules and the low detection efficiency of Raman scattering make visualization a challenge. Herein, we visualized photosynthetic microbial biofilms in a label-free manner using a super-resolution optical infrared absorption imaging technique, called mid-infrared photothermal (MIP) microscopy. By leveraging the advantages of MIP microscopy, such as its sub-micrometer spatial resolution, autofluorescence-free features, and high detection sensitivity, the distribution of cyanobacteria and their extracellular polysaccharides in the biofilm matrix were successfully visualized. This showed that cyanobacterial cells were aligned along acidic/sulfated polysaccharides in the extracellular environment. Furthermore, spectroscopic analyses elucidated that during formation of biofilms, sulfated polysaccharides initially form linear structures followed by entrapment of cyanobacterial cells. The present study provides the foundation for further studies on the formation, structure, and biological functions of microbial biofilms.
Photosynthetic microbial biofilms were studied using mid-infrared photothermal (MIP) microscopy in a label-free manner. The distribution of cyanobacterial cells and their extracellular polysaccharides in the biofilm matrix were successfully visualized.
The pluripotent state of embryonic stem (ES) cells is controlled by a network of specific transcription factors. Recent studies also suggested the significant contribution of mitochondria on the ...regulation of pluripotent stem cells. However, the molecules involved in these regulations are still unknown.
In this study, we found that prohibitin 2 (PHB2), a pleiotrophic factor mainly localized in mitochondria, is a crucial regulatory factor for the homeostasis and differentiation of ES cells. PHB2 was highly expressed in undifferentiated mouse ES cells, and the expression was decreased during the differentiation of ES cells. Knockdown of PHB2 induced significant apoptosis in pluripotent ES cells, whereas enhanced expression of PHB2 contributed to the proliferation of ES cells. However, enhanced expression of PHB2 strongly inhibited ES cell differentiation into neuronal and endodermal cells. Interestingly, only PHB2 with intact mitochondrial targeting signal showed these specific effects on ES cells. Moreover, overexpression of PHB2 enhanced the processing of a dynamin-like GTPase (OPA1) that regulates mitochondrial fusion and cristae remodeling, which could induce partial dysfunction of mitochondria.
Our results suggest that PHB2 is a crucial mitochondrial regulator for homeostasis and lineage-specific differentiation of ES cells.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Somatic cell reprogramming proceeds through a series of events to generate induced pluripotent stem cells (iPSCs). The early stage of reprogramming of mouse embryonic fibroblasts is characterized by ...rapid cell proliferation and morphological changes, which are accompanied by downregulation of mesenchyme-associated genes. However, the functional relevance of their downregulation to reprogramming remains poorly defined. In this study, we have screened transcriptional regulators that are downregulated immediately upon reprogramming, presumably through direct targeting by reprogramming factors. To test if these transcriptional regulators impact reprogramming when expressed continuously, we generated an expression vector that harbors human cytomegalovirus upstream open reading frame 2 (uORF2), which reduces translation to minimize the detrimental effect of an expressed protein. Screening of transcriptional regulators with this expression vector revealed that downregulation of (odd-skipped related 2 Osr2) is crucial for efficient reprogramming. Using a cell-based model for epithelial-mesenchymal transition (EMT), we show that Osr2 is a novel EMT regulator that acts through induction of transforming growth factor-β (TGF-β) signaling. During reprogramming, Osr2 downregulation not only diminishes TGF-β signaling but also allows activation of Wnt signaling, thus promoting mesenchymal-epithelial transition (MET) toward acquisition of pluripotency. Our results illuminate the functional significance of Osr2 downregulation in erasing the mesenchymal phenotype at an early stage of somatic cell reprogramming.
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