Injectable Enzyme‐Based Hydrogel Matrix with Precisely Oxidative Stress Defense for Promoting Dermal Repair of Burn Wound

Burn wound healing remains a challenging health problem worldwide due to the lack of efficient and precise therapy. Inherent oxidative stress following burn injury is importantly responsible for prolonged inflammation, fibrotic scar, and multiple organ failure. Herein, a bioinspired antioxidative defense system coupling with in situ forming hydrogel, namely, multiresponsive injectable catechol‐Fe³⁺ coordination hydrogel (MICH) matrix, is engineered to promote burn‐wound dermal repair by inhibiting tissue oxidative stress. This MICH matrix serves as the special traits of “Fe‐superoxide dismutases,” small molecular antioxidant (vitamin E), and extracellular matrix (ECM) in alleviating cellular oxidative damage, which demonstrates precise scavenging on reactive oxygen species (ROS) of different cellular locations, blocking lipid peroxidation and cell apoptosis. In in vivo burn‐wound treatment, this MICH promptly integrates with injured surrounding tissue to provide hydration microenvironment and physicochemical ECM for burn wounds. Importantly, the MICH matrix suppresses tissue ROS production, reducing the inflammatory response, prompting re‐epithelization and neoangiogenesis during wound healing. Meanwhile, the remodeling skin treated with MICH matrix demonstrates low collagen deposition and normal dermal collagen architecture. Overall, the MICH prevents burn wound progression and enhances skin regeneration, which might be a promising biomaterial for burn‐wound care and other disease therapy induced by oxidative stress.     

Overview of Polyvinyl Alcohol Nanocomposite Hydrogels for Electro‐Skin,Actuator, Supercapacitor and Fuel Cell

The properties of polyvinyl alcohol (PVA) nanocomposite hydrogels influenced by nanoparticles are reviewed. Various kinds of nanoparticles with excellent mechanical and electrical properties have been introduced into PVA hydrogel to produce stretchable and conductive PVA nanocomposite hydrogel. Understanding the mechanism between the matrix of PVA hydrogel and nanoparticles is therefore critical for the development of PVA nanocomposite hydrogels. This review focuses on the nanoparticles include carbon nanotubes, graphene oxide and metal nanoparticles, and describes the effects of nanoparticles on the mechanical and conductive properties of PVA nanocomposite hydrogels. A new promising area of soft stretchable PVA nanocomposite hydrogel is highlighted for possible applications. Finally, a brief outlook for future research is presented.     

Phospholipid Polymer Hydrogel Matrices with Dually Immobilized Cytokines for Accelerating Secretion of the Extracellular Matrix by Encapsulated Cells

Construction of 3D tissues by various types of cells with specific characteristics is an important and fundamental technology in tissue reconstruction medicine and animal‐free diagnosis system. To do so, an excellent extracellular matrix (ECM) is needed for encapsulation of cells and maintaining cell activity. Spontaneously forming hydrogel matrix is used by complexation between two water‐soluble polymers, 2‐methacryloyloxyethyl phosphorylcholine polymer bearing phenylboronic acid groups and poly(vinyl alcohol). Two cytokines for cell proliferation are immobilized in the hydrogel matrix to control the activities of the encapsulated cells. The cytokine‐immobilized hydrogel matrix can encapsulate both L929 fibroblasts and normal human dermal fibroblasts under mild condition. The physical properties of the hydrogel matrix can follow the proliferation process of the encapsulated cells. The encapsulated cells secrete ECM in the polymer hydrogel networks upon 3D culturing for 7 days. Consequently, the tissue‐mimicking ECM hybrid hydrogels are fabricated successfully.     

Structural rearrangement and stiffening of hydrophobically modified supramolecular hydrogels during thermal annealing

Dynamic crosslinks formed by thermoreversible associations provide an energy dissipation mechanism to toughen hydrogels. However, the details of the organization of these crosslinks impact the hydrogel properties through constraints on the network chain conformation. The physical crosslinks generated by hydrophobic association of the 2‐(N‐ethylperfluorooctane‐sulfonamido)ethyl methacrylate (FOSM) groups in a random copolymer of N,N‐dimethylacrylamide (DMA) and FOSM provide a simple system to investigate how the hydrogel structure (as determined from small angle neutron scattering impacts the mechanical properties of the hydrogel. The initial hydration of the copolymer at 25 °C leads to a kinetically trapped structure with large‐scale heterogeneities. Heating the hydrogel at 60 °C, which is above the glass transition temperature for the FOSM domains, allows the hydrogel structure to rearrange to reduce the density of network defects and the structural heterogeneities. That effectively increases the crosslink density of the network, which stiffens the hydrogel and decreases the swelling at equilibrium at 25 °C. The processing history determines how the hydrophobes aggregate to form the physically crosslinked network, whose structure defines the mechanical properties of these hydrogels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1036–1044     

pH reversible micelle transition of a tertiary amine-based gemini surfactant in aqueous solution

In this work, we prepared a tertiary amide-based gemini surfactant (DSTAPA), which contained two pH-sensitive tertiary amide head groups. Then the molecule state distribution and self-assembly transition of the surfactant in aqueous solution were investigated under different pH conditions. The DSTAPA molecules were on the states of double cationic (DSTAPAH²⁺), single cationic (DSTAPAH⁺), and double tertiary amine groups (DSTAPA) under acidic, neutral, and basic conditions, respectively. With the variation of the molecule states, the sample was water-like below pH of 6.8 and immediately transformed to gel-like fluid between pH of 6.8 and 7.8, then changed to white precipitate with the further increase of pH value. Furthermore, the microstructure and regulation mechanism were investigated by rheological measurements, dynamic light scattering, and cryogenic transmission electron microscopy. The appearance and micelle transitions of the DSTAPA aqueous solution are actually owing to the spherical–worm-like micelle transition, leading to dramatic viscosity increase and hydrogel formation. This transition was completely reversible and repeated for at least three cycles. Finally, a reasonable mechanism of the transition was proposed based on the viewpoints of the molecular states and micelle structures. The DSTAPA aqueous system with pH-reversible property has a great potential application in oil and gas production.     

Fine tuning the assembly and gel behaviors of PEGylated polypeptide conjugates by the copolymerization of l‐alanine and γ‐benzyl‐l‐glutamate N‐carboxyanhydrides

Tuning the secondary structure of polypeptide is an effective strategy to modulate the assembly behaviors of polypeptide‐based copolymers. In this study, ring‐opening polymerization of l ‐alanine (Ala) and γ‐benzyl‐l ‐glutamate (BLG) N‐carboxyanhydrides was adopted using mPEG‐NH₂ as the initiator to prepare mPEG‐poly(l ‐alanine‐co‐γ‐benzyl‐l ‐glutamate) (PEAB) copolymers with various Ala to BLG ratios. ¹H NMR spectra and GPC test confirmed their well‐defined chemical structures. FT‐IR spectra indicated that at the powder state, all copolymers adopted both β‐sheet and α‐helical conformations. With the content of PBLG increased, the crystallization temperature and melting points of PEAB copolymers first rose then fell indicated by DSC curves. The self‐assembly of PEAB copolymers in dilute aqueous solution studied by DLS, TEM and circular dichroism spectra showed that PEAB copolymers self‐assembled into nanostructures with diverse morphologies and sizes due to distinct polypeptide conformations. Rheological analysis indicated that the alteration of the polypeptide composition can effectively modulate the modulus of PEAB assemblies in concentrated solutions. In all, copolymerization of two hydrophobic amino acid N‐carboxyanhydrides into the polypeptide block maybe an effective approach for modulating the assembly properties of PEGylated polypeptide. Besides, nanosilver‐encapsulated PEA or PEAB hydrogel showed promising antibacterial effect against Staphylococcus aureus and Bacillus subtillis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1512–1523     

Sol-Gel Nanometrology: Gated Sampling Can Reveal Initial Sol Formation Kinetics

This report describes a gated sampling approach for studying the initial formation of sol-gel glasses prepared from sodium silicate solution (water glass) and sulphuric acid. Previously described were how changes in particle size and subsequently how sol-gel formation dynamics can be tracked using time-resolved fluorescence anisotropy, by labeling growing silica nanoparticles with suitable fluorescence probes. One limiting factor of this approach was the 2 minute measurement time, which limits this technique for studying the initial sol formation dynamics and limits the measurement precision. Using a continuous flow system and delaying sol flow through different tubing lengths overcomes this problem and allows monitoring of the very early stages of sol formation, second by second after sol preparation, irrespective of the anisotropy measurement time. This technique was applied to studying the initial formation dynamics, within the first 30 seconds, of a 12.01% SiO₂ (w/w), pH 0.66 sol-gel, finding that silica particles of 1.5 nm mean radius are formed within 10 seconds of mixing the sol-gel.     

Peptide dendrimer-crosslinked inorganic-organic hybrid supramolecular hydrogel for efficient anti-biofouling

A novel kind of inorganic-organic hybrid supramolecular hydrogel with excellent anti-biofouling capability was developed. The hydrogel was formed via ionic interaction between the negative-charged sodium polyacrylate (SPA) entwined clay nanosheets (CNS) and positive-charged polyhedral oligomeric silsesquioxane (POSS) core-based generation one (L-Arginine) dendrimer (POSS-R).     

DNA水凝胶在生物传感中的应用和发展

脱氧核糖核酸(DNA)是一种重要的生物分子,具有许多独特的性质如:信息传递、分子识别、可编辑等。DNA水凝胶同时具有DNA分子和水凝胶材料的优势,并且可以引入其他纳米材料获得多功能杂化水凝胶。相比于传统水凝胶,DNA水凝胶具有良好的特异识别能力以及可以按需设计的性质,从而被广泛应用于生物传感领域。本文围绕DNA水凝胶的合成、响应机制以及在传感领域的应用进行综述。按照不同的合成方法可分为线性DNA链缠绕水凝胶、枝状DNA自组装水凝胶、杂合DNA水凝胶。根据传感机制的不同又可以分为包埋封装法和非包埋封装法,包埋封装发法又分为:酶的包埋释放、抗原-抗体的包埋释放、纳米材料的包埋释放。本文总结了近几年DNA水凝胶在重金属离子检测、核酸检测、葡萄糖检测、蛋白质和代谢小分子检测,以及细胞检测等热门领域的研究情况,最后对其未来的发展进行了展望。