A new class of dual-crosslinked hydrogels comprising thermoresponsive Pluronic-F127 (coded as TIC) and the covalently-linked molecular segment (coded as NIC) forming through the Michael-type addition ...reaction of vinyl sulfone-modified dextran (Dex-VS) and thiolated-poly(ethylene glycol) was introduced. Dextrans with two different molecular weights were first modified with divinyl sulfone and then thoroughly characterized. Subsequently, the in situ-forming hydrogels with weight ratios of TIC and NIC components varied from 0/100 to 50/50 were prepared with and without chondrocytes. The stiffness of the resultant hydrogels fell in the range of 3.1 to 25.9 kPa. The physicochemical properties of the hydrogels, e.g., pore structure, degradability, and swellability, were thoroughly assessed as a function of incubation time in culture media, alongside their influence on the viability and growth of cells encapsulated in the hydrogels. Interestingly, using a higher molecular weight of Dex-VS altered the physicochemical property of hydrogel and improved cellular activity. The leaching profiles of TIC segments from the hydrogels were also investigated using fluorescently tagged Pluronic-F127. Notably, both TIC and NIC segments concurrently degraded over time. The developed biodegradable hydrogels with controlled mechanical properties had the potential to be used in cartilage tissue engineering and other regenerative medicine applications.
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•A new class of dual-crosslinked hydrogels comprising thermoresponsive Pluronic-F127 and the covalently-linked molecular segment forming through the Michael-type addition reaction of vinyl sulfone-modified dextran and thiolated-poly(ethylene glycol) was introduced.•The effect of thermoresponsive and covalently-linked molecular components and molecular weight of Dex-VS on the physicochemical properties of dual-crosslinked hydrogels was investigated.•The hydrogel stiffness drastically influenced the viability and growth of the encapsulated chondrocytes.
Amphiphilic block copolymers were synthesized by ring‐opening polymerization of ε‐caprolactone (ε‐CL) using 4‐arm poly(ethylene glycol) (4aPEG) as macroinitiator. 4aPEG and 4aPEG‐PCL copolymers were ...end functionalized by introducing acrylic groups, and characterized using NMR, GPC, FT‐IR and DSC analyses. Photo‐crosslinked hydrogels were prepared by irradiation of acrylated polymer solutions under visible light (405 nm), using lithium phenyl‐2,4,6‐trimethylbenzoy‐lphosphinate (LAP) as a photoinitiator. In situ gelation was achieved by subcutaneous injection of LAP containing copolymer solution into the abdomen of mice, followed by exposure to visible light. The hydrogels exhibit highly porous structure, high swelling up to 3300%, and excellent biocompatibility. The swelling ratio decreases with increase of poly(ɛ‐caprolactone) (PCL) block length and polymer concentration of hydrogels. Doxorubicin hydrochloride (DOX·HCl) was loaded in hydrogels by soaking dried gel in a DOX solution. The drug loading efficiency is dependent on the swelling performance, reaching a maximum of 94.3%. In vitro drug release studies showed a burst release for the first 6 h, followed by a slower release up to 82% at 28 days. The release rate decreased with increase of hydrophobic block length or polymer concentration of hydrogels. Higher anti‐cancer activity on A549 lung cancer cells was obtained for hydrogels with higher drug concentration, and shorter PCL block length. Therefore, 4aPEG‐PCL hydrogels with outstanding biocompatibility, in situ gelation and prolonged drug release could be very promising for long‐term local cancer therapy.
Flexible wearable sensors based on conductive hydrogels are attracting increasing interest. To meet the urgent demands of sustainability and eco-friendliness, biopolymer-based physically crosslinked ...hydrogels have drawn great attention. Starch has a great potential due to its renewability, biocompatibility, nontoxicity and low cost. However, poor mechanical property, low conductivity and lack of versatility are seriously limiting the applications of starch-based hydrogels in wearable sensors. Moreover, the development of starch hydrogel-based wearable sensors in harsh conditions remains a challenge. Herein, multifunctional and physical crosslinking hydrogels were developed by introducing ionic liquid (1-ethyl-3-methyl imidazolium acetate) and metal salt (AlCl3) into starch/polyvinyl alcohol double-network structure. The hydrogel exhibited excellent stretchability (567%), tensile strength (0.53 MPa), high conductivity (2.75 S·m−1), good anti-freezing, antibacterial and anti-swelling properties. A wearable sensor assembled from the starch-based hydrogel exhibited a wide working range, high sensitivity (gauge factor: 5.93) and excellent reversibility. Due to the versatility, the sensor effectively detected human motion in normal and underwater environment, and possessed a sensitive pressure and thermal response. Overall, the present work provided a promising route to develop multifunctional and “green” biopolymer-based hydrogels for wearable sensors in human health and sporting applications.
•A high-flexible and ultra-conductive starch-based physical hydrogel was prepared.•Ionic liquid and melt salt synergistically increased the properties of the hydrogel.•The hydrogel possessed excellent anti-freezing and antibacterial properties.•A wearable sensor had sensitive responses to human motions, strain and temperature.•An anti-swelling and underwater wearable sensor was constructed successfully.
3-Nitro-1, 2, 4-triazole-5-one (NTO) is an important insensitive explosive. The discharge of NTO wastewater not only pollutes the environment but also causes the economic loss of the valuable ...explosive. Currently, the NTO wastewater in industrial production is often treated with activated carbon adsorbents. There are no green, efficient and specific adsorption materials for the NTO treatment yet. In the present work, polymer materials suitable for NTO adsorption were screened by molecular dynamics simulation. With the optimized materials, a carrageenan/chitosan/calcium ion physically cross-linked double network hydrogel (KC/CTS/Ca2+ PCDNH) was successfully prepared by the semi-soluble-acidified sol-gel conversion method. The structure and NTO adsorption performance of the hydrogel were investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The NTO adsorption kinetics, isotherm, and thermodynamics were further studied to understand the adsorption behavior and mechanism. In addition, the adsorbed NTO was successfully released and recovered by soaking the hydrogel in NaOH solution. Our work has provided an environmentally friendly and targeted preparation method of NTO adsorbent materials for NTO wastewater treatment.
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•A targeted preparation method of the adsorbent for energy-containing wastewater was studied.•A novel eco-friendly physically-crosslinked double-network hydrogel was prepared.•The hydrogel showed excellent adsorption capacities for NTO.•The adsorption of NTO by PCDNH is mainly controlled by physical adsorption.•The NTO can be released and recycled from the adsorbed hydrogel.
Supramolecular hydrogels held together by non-covalent interactions such as electrostatics, hydrogen bonding, and hydrophobic forces are among the most promising soft material platforms for modern ...biomedical applications. By virtue of their inherent reversibility and dynamism, they respond well to environmental stimuli and biochemical cues and can dissipate mechanical energy effectively. These important features are well suited for cell culture, tissue engineering, on-demand controlled release of therapeutics, tissue adhesion, and molecular sensing and as artificial gel substitutes in organs (e.g., vitreous humour and synovial fluids), which are not easily achieved by permanently cross-linked covalent hydrogels. Consequently, supramolecular hydrogels have grown in popularity and have witnessed rapid development for biomedical applications in recent years. Through the numerous applications and exciting advances during the last five years discussed in this mini-review, we highlight how the supramolecular interactions enabling gel formation also translates to their bulk material properties and resulting biomedical applications. Owing to their versatility and ease of ‘bottom-up’ engineering from the molecular level, supramolecular hydrogels are poised to offer a wide range of biomedical solutions to modern societal problems, including but not limited to wound healing, development of artificial tissues, cell therapies, and anticancer treatment. Keywords: Physically-crosslinked hydrogels, Hydrophobic interactions, Hydrogen bonding, Ionic interactions, Inclusion complexes
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•S-protected thiolated HA was synthesized by carbodiimide-mediated reaction.•S-protected HA showed enhanced cohesion upon addition of N-acetyl cysteine (NAC).•Due to addition of NAC, ...viscosity of S-protected thiolated HA increased 20-fold.•Cells encapsulated into scaffolds proliferated uniformly in polysaccharide matrix.
The purpose of this study was to synthesize S-protected thiolated hyaluronic acid (HA) and to evaluate its potential for 3D cell culture scaffold. S-protected thiolated HA was synthesized by the covalent attachment of N-acetyl-S-((3-((2,5-dioxopyrrolidin-1-yl)oxy)-3-oxopropyl)thio)cysteine hydrazide ligand to the HA. Hydrogels were characterized for texture, swelling behavior and rheological properties. Furthermore, the potential of S-protected thiolated HA hydrogels as a scaffold for tissue engineering was evaluated by cell proliferation studies with Caco-2 and NIH 3T3 cells. It showed enhanced cohesion upon addition of N-acetyl cysteine (NAC). Dynamic viscosity of S-protected thiolated HA hydrogel was increased up to 19.5-fold by addition of NAC and 10.1-fold after mixing with mucus. Furthermore, Caco-2 and NIH 3T3 cells encapsulated into hydrogels proliferated in-vitro. As this novel S-protected thiolated HA is stable towards oxidation and forms highly cohesive gels when getting into contact with endogenous thiols due to disulfide-crosslinking, it is a promising tool for 3D cell culture scaffold.
A smart window, which can easily adjust light transmittance, can provide barrier functions, such as improvement in energy efficiency, glare prevention, and privacy protection. However, a smart window ...that can selectively provide real-time information and display various colorful characters and images at a desired location has not been developed. In this study, a novel smart window capable of real-time information conversion is developed by advancing the light transmittance control of the existing smart windows. A transparent and flexible window display is fabricated by synthesizing poly(N-isopropylacrylamide) (pNIPAM)–N,N-methylenebisacrylamide-crosslinked hydrogels (NBcH) and near-infrared (NIR) absorption-heating films sandwiched between two plastic substrates. When the NIR laser irradiates the window display panel surface, the temperature rises rapidly, as the NIR absorption-heating film absorbs the NIR wavelength. The generated heat is transferred to pNIPAM in contact with the NIR absorption-heating film, and an image forms in real time. In addition, if the NIR laser and projector simultaneously irradiate the window display panel surface, various colorful images can be displayed. The smart window for real-time information provision proposed in this study acts like a glass curtain that can selectively make a desired location transparent or opaque by controlling the transmittance of light and acts as a display that can present various colorful characters and images in real time. Therefore, it is expected to be highly convenient for users.
Broader applications of polymer hydrogels are largely constrained by their poor mechanical performance. Here, we report our strategy of achieving ultrahigh mechanical strength, toughness, and ...self-healing properties simultaneously in a hybrid dual crosslinked polyacrylic acid (PAAc) hydrogel. The hybrid PAAc hydrogel was fabricated in a one-pot reaction with two types of crosslinking points, i.e. the primary chemical cross-linkers that create covalent cross-linking among PAA chains and the secondary physical cross-linkers Fe3+ that introduce ionic coordinates between Fe3+ and −COO− groups. The resulting hybrid PAA hydrogel was subsequently subject to a simple saline solution soaking to become highly mechanically robust as a result of chain entanglement within the network. Favorable mechanical properties possessed by such hybrid hydrogels included high tensile strength (ca. 1.794 MPa), large elongation at break (ca. 13.209 times), and excellent work of extension (ca. 11.475 MJ m−3). In addition, the hydrogels exhibited self-healing properties because of their inter-chain interactions at ambient conditions (tensile strength can recover approximately 30% of the initial after self-healing for 48 h from a cut-off state). This work demonstrates a simple and promising strategy of preparation of novel ductile and doughty hydrogels through dual crosslinking and saline solution soaking.
The gel molecular chain is completely entangled by the induction of salt solution, which greatly improves the mechanical properties of the gels. Display omitted
•A hybrid dual crosslinked polyacrylic acid hydrogel was facilely prepared in one-pot.•The hydrogel exhibited excellent mechanical properties.•The hydrogel exhibited good self-healing properties.•The mechanism of hydrogel failure/destruction can be explained by a “double-network hydrogel sacrificial bond theory”.
A novel reusable, plastic-free, and stable cooling medium, Jelly Ice Cubes (JIC), is developed based on crosslinked gelatin hydrogels for sustainable temperature control. A novel process involving a ...rapid-freezing-slow-thawing treatment and a subsequent photo-crosslinking reaction induced by menadione sodium bisulfite, a newly discovered photosensitizer, is able to effectively consolidate a three-dimensional (3-D) hydrogel network to survive repeated application freeze–thaw cycles (AFTCs). This study reveals the mechanisms and evidence of the synergistic effects of the physical and chemical crosslinking reactions. The results experimentally prove that the rapid-freezing-slow-thawing treatment induces the generation of gelatin microcrystalline domains, refines the protein polymeric network, and reduces the intervening distance for subsequent photo-crosslinking sites. The refined hydrogel 3-D network is consolidated by the photo-crosslinking reaction occurring at the intersectional areas of the gelatin microcrystalline domains. The proposed crosslinking approach yields JICs with superior mechanical properties, robustness, and consistent water content, even after repeated AFTCs, all the while retaining cooling efficiency and biodegradability. The proposed crosslinked hydrogel structure is potentially applicable to engineering other hydrogel materials, offering sustainble and biodegradable solutions with enhanced resilience against phase changes.
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