scholarly journals Conjoined-network rendered stiff and tough hydrogels from biogenic molecules

2019 ◽  
Vol 5 (2) ◽  
pp. eaau3442 ◽  
Author(s):  
Liju Xu ◽  
Chen Wang ◽  
Yang Cui ◽  
Ailing Li ◽  
Yan Qiao ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Compressive Modulus ◽  
Cross Linking ◽  
General Strategy ◽  
Soft Or ◽  
Double Network ◽  
Dissipation Mechanism ◽  
New Strategy ◽  
Biological Sources ◽  
Network Approaches

Hydrogels from biological sources are expected as potential structural biomaterials, but most of them are either soft or fragile. Here, a new strategy was developed to construct hydrogels that were both stiff and tough via the formation of the conjoined-network, which was distinct from improving homogeneity or incorporating energy dissipation mechanisms (double-network) approaches. Conjoined-network hydrogels stand for a class of hydrogels consisting of two or more networks that are connected by sharing interconnection points to collaborate and featured as follows: (i) All the composed networks had a similar or equal energy dissipation mechanism, and (ii) these networks were intertwined to effectively distribute stress in the whole system. As a specific example, a biogenic conjoined-network hydrogel was prepared by electrostatically cross-linking the chitosan-gelatin composite with multivalent sodium phytate. The combination of high compressive modulus and toughness was realized at the same time in the chitosan-gelatin-phytate system. Moreover, these physical hydrogels exhibited extraordinary self-recovery and fatigue resistance ability. Our results provide a general strategy for the design of biocompatible stiff and tough conjoined-network hydrogels due to a variety of potential cross-linking mechanisms available (e.g., electrostatic attraction, host-guest interaction, and hydrogen bonding).

Biodegradable Polyurethanes Cross-Linked by Multifunctional Compounds

2017 ◽  
Vol 14 (6) ◽  
pp. 778-784 ◽  
Author(s):  
Joanna Brzeska
Keyword(s):  
Polymer Structure ◽  
Cross Linking ◽  
Plant Oils ◽  
Lignocellulosic Materials ◽  
Soft Or ◽  
Native State ◽  
Synthetic Compounds ◽  
Multifunctional Compounds ◽  
Hard Segments ◽  
Synthetic Origin

Background: Cross-linking structure of polyurethanes determines no degradability of these materials. However, introducing the hydrolysable substrates (of natural or synthetic origin) into the cross-linked polyurethanes structure makes them biodegradable. Moreover compounds (such as polycaprolactone triol, glycerin, lysine triisocyanate, etc.) that are used for polyurethane cross-linking are degraded in non-toxic products. All these kinds of compounds can be introduced into soft or hard segments via urethane bonds. Objective: The review focuses on kind of multifunctional polyols and isocyanates, and low molecular crosslinkers used for cross-linked polyurethanes obtaining. These compounds are natural substrates (in the native state or after modification) or are synthetic compounds with degradable linkages. They belong to polyesters, plant oils, proteins, saccharides, and others (e.g. lignocellulosic materials), and they are synthesized chemically or via biosynthesis by algae, plants, microorganisms, and by animals. Conclusion: Incorporation of degradable groups (such as ester moieties) into the polymer structure, and using of substrates with the structure known and metabolized by microorganisms for soft or hard segments building, facilitate degradation of cross-linked polyurethanes.

Selective De-Cross-Linking of Transformable, Double-Network Hydrogels: Preparation, Structural Conversion, and Controlled Release

2018 ◽  
Vol 10 (49) ◽  
pp. 42985-42991 ◽  
Author(s):  
Doyoung Jung ◽  
Kyoung Min Lee ◽  
Ji Young Chang ◽  
Misun Yun ◽  
Hak-Jong Choi ◽  
...  
Keyword(s):  
Controlled Release ◽  
Cross Linking ◽  
Structural Conversion ◽  
Double Network

scholarly journals Elasticity and energy dissipation in the double network hydrogel adhesive of the slug Arion subfuscus

2019 ◽  
Vol 374 (1784) ◽  
pp. 20190201 ◽  
Author(s):  
T.-M. Fung ◽  
C. Gallego Lazo ◽  
A. M. Smith
Keyword(s):  
Energy Dissipation ◽  
Time Course ◽  
Tensile Tests ◽  
Cyclic Stress ◽  
Mechanical Tests ◽  
Double Network ◽  
Ph Values ◽  
Arion Subfuscus ◽  
Synthetic Adhesives ◽  
Cross Links

The slug Arion subfuscus produces a mucus-based defensive secretion that is remarkably tough. This glue appears to be a double network hydrogel, gaining its toughness through the synergistic actions of two networks of polymers, a relatively stiff network and a relatively deformable network. The double network mechanism has great potential to guide the development of synthetic adhesives. Mechanical tests were performed to analyse key predictions of the mechanism. Stress relaxation tests and tensile tests support the presence of stable cross-links. Cyclic stress–strain tests demonstrate that the glue dissipates a great deal of energy through the failure of these cross-links as sacrificial bonds. Energy dissipation by failure of sacrificial bonds rather than viscous processes is supported by the minimal effect of the time course of the experiments on the measured properties. These sacrificial bonds appear able to reform within minutes after failure. Finally, the glue's stiffness decreases at pH values below 5.5, whereas magnesium and calcium rapidly dissociate from the glue at all pH values tested. Thus, these ions may not be the primary cross-linkers generating the glue's stiffness. This article is part of the theme issue ‘Transdisciplinary approaches to the study of adhesion and adhesives in biological systems’.

scholarly journals A general strategy exploiting m5C duplex-remodelling effect for selective detection of RNA and DNA m5C methyltransferase activity in cells

2019 ◽  
Author(s):  
Tianming Yang ◽  
Joanne J A Low ◽  
Esther C Y Woon
Keyword(s):  
Dna Methyltransferase ◽  
General Strategy ◽  
Dna Duplexes ◽  
Methyltransferase Activity ◽  
Cpg Dna ◽  
Sugar Pucker ◽  
High Profile ◽  
New Strategy ◽  
Rna And Dna ◽  
In Cells

Abstract RNA:5-methylcytosine (m5C) methyltransferases are currently the focus of intense research following a series of high-profile reports documenting their physiological links to several diseases. However, no methods exist which permit the specific analysis of RNA:m5C methyltransferases in cells. Herein, we described how a combination of biophysical studies led us to identify distinct duplex-remodelling effects of m5C on RNA and DNA duplexes. Specifically, m5C induces a C3′-endo to C2′-endo sugar-pucker switch in CpG RNA duplex but triggers a B-to-Z transformation in CpG DNA duplex. Inspired by these different ‘structural signatures’, we developed a m5C-sensitive probe which fluoresces spontaneously in response to m5C-induced sugar-pucker switch, hence useful for sensing RNA:m5C methyltransferase activity. Through the use of this probe, we achieved real-time imaging and flow cytometry analysis of NOP2/Sun RNA methyltransferase 2 (NSUN2) activity in HeLa cells. We further applied the probe to the cell-based screening of NSUN2 inhibitors. The developed strategy could also be adapted for the detection of DNA:m5C methyltransferases. This was demonstrated by the development of DNA m5C-probe which permits the screening of DNA methyltransferase 3A inhibitors. To our knowledge, this study represents not only the first examples of m5C-responsive probes, but also a new strategy for discriminating RNA and DNA m5C methyltransferase activity in cells.

scholarly journals Organic/Inorganic Superabsorbent Hydrogels Based on Xylan and Montmorillonite

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Shuang Zhang ◽  
Ying Guan ◽  
Gen-Que Fu ◽  
Bo-Yang Chen ◽  
Feng Peng ◽  
...  
Keyword(s):  
Compressive Modulus ◽  
Cross Linking ◽  
Swelling Properties ◽  
Ph Values ◽  
Swelling Capacity ◽  
Wide Ph Range ◽  
Grafting Copolymerization ◽  
Ph Range ◽  
Influence Of Ph ◽  
Superabsorbent Hydrogels

The unique organic/inorganic superabsorbent hydrogels based on xylan and inorganic clay montmorillonite (MMT) were prepared via grafting copolymerization of acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) withN,N-methylenebisacrylamide (MBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The effect of variables on the swelling capacity of the hydrogels, such as the weight ratios of MMT/xylan, MBA/xylan, and AMPS/AA, was systematically optimized. The results indicated that the superabsorbent hydrogels comprised a porous cross-linking structure of MMT and xylan with side chains that carry carboxylate, carboxamide, and sulfate. The hydrogels exhibit the high compressive modulus (E), about 35–55 KPa, and the compression strength of the hydrogels increased with an increment of the MMT content. The effect of various cationic salt solutions (LiCl, CaCl2, and FeCl3) on the swelling has the following order: Li+> Ca2+> Fe3+. Furthermore, the influence of pH values on swelling behaviors showed that the superabsorbent composites retained around 1000 g g−1over a wide pH range of 6.0–10.0. The xylan-based hydrogels with the high mechanical and swelling properties are promising for the applications in the biomaterials area.

scholarly journals Interfacial strength-controlled energy dissipation mechanism and optimization in impact-resistant nacreous structure

2019 ◽  
Vol 163 ◽  
pp. 107532 ◽  
Author(s):  
Kaijin Wu ◽  
Zhijun Zheng ◽  
Shuaishuai Zhang ◽  
Linghui He ◽  
Hongbin Yao ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Interfacial Strength ◽  
Energy Dissipation Mechanism ◽  
Dissipation Mechanism

scholarly journals Energy dissipative photoprotective mechanism of carotenoid spheroidene from the photoreaction center of purple bacteria Rhodobacter sphaeroides

2015 ◽  
Vol 17 (36) ◽  
pp. 23468-23480 ◽  
Author(s):  
Sundaram Arulmozhiraja ◽  
Naoki Nakatani ◽  
Akira Nakayama ◽  
Jun-ya Hasegawa
Keyword(s):  
Energy Dissipation ◽  
Rhodobacter Sphaeroides ◽  
Purple Bacteria ◽  
Minimum Energy ◽  
Intersystem Crossing ◽  
Triplet Energy ◽  
Energy Dissipation Mechanism ◽  
Dissipation Mechanism ◽  
Crossing Point

Triplet energy dissipation mechanism of a carotenoid: just bond twisting and stretching lead to minimum energy intersystem crossing point.

Thermal Effects of Cracked Piezoelectric Materials under Cycling Electric-Loading

2006 ◽  
Vol 312 ◽  
pp. 35-40 ◽  
Author(s):  
Ning Ning Du ◽  
Shou Wen Yu
Keyword(s):  
Fracture Toughness ◽  
Energy Dissipation ◽  
Temperature Rise ◽  
Open Problem ◽  
Thermal Effects ◽  
Fracture Behavior ◽  
Piezoelectric Materials ◽  
Electric Loading ◽  
Dissipation Mechanism ◽  
Piezoelectric Solids

It is still an open problem how the thermal effect influences the fracture behavior of piezoelectric materials especially under cycling electrical loading. Experimental observations have found that the fracture toughness of piezoelectric solids under electric loading may be greatly different from that under mechanical loading. A pronounced rise of temperature may be caused either by mechanical or by electric loading. In this paper, the thermal effects and energy dissipation mechanism in cracked piezoelectric materials under cyclic-electric-loading have been studied. The temperature rise is derived under the assumption of decoupling between thermal and electromechanical fields and the influences of frequency and the shape of electric wave on the temperature rise are quantitatively analyzed.

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