Review of electrospun hydrogel nanofiber system: Synthesis,Properties and Applications

Hydrogel-based nanofibers or vice versa are a relatively new class of nanomaterials, in which hydrogels are structured in nanofibrous form. Structure and size of the material directly governs its functionality, therefore, in hydrogel science, the nanofibrous form of hydrogels enables its usage in targeted applications. Hydrogel nanofiber system combines the desirable properties of both hydrogel and nanofiber like flexibility, soft consistency, elasticity, and biocompatibility due to high water content, large surface area to volume ratio, low density, small pore size and interconnected pores, high stiffness, tensile strength, and surface functionality. Swelling behavior is a critical property of hydrogels that is significantly increased in hydrogel nanofibers due to their small size. Electrospinning is the most popular method to fabricate “hydrogel nanofibers,” while other processes like self-assembly, solution blowing and template synthesis also exist. Merging the characteristics of both hydrogels and nanofibers in one system allows applications in drug delivery, tissue engineering, actuation, wound dressing, photoluminescence, light-addressable potentiometric sensor (LAPS), waterproof breathable membranes, and enzymatic immobilization. Treatment of wastewater, detection, and adsorption of metal ions are also emerging applications. In this review paper, we intend to summarize in detail about electrospun “hydrogel nanofiber” in relation to its synthesis, properties, and applications.     

TGFβ-1 Induced Cross-Linking of the Extracellular Matrix of Primary Human Dermal Fibroblasts

Excessive cross-linking is a major factor in the resistance to the remodelling of the extracellular matrix (ECM) during fibrotic progression. The role of TGFβ signalling in impairing ECM remodelling has been demonstrated in various fibrotic models. We hypothesised that increased ECM cross-linking by TGFβ contributes to skin fibrosis in Systemic Sclerosis (SSc). Proteomics was used to identify cross-linking enzymes in the ECM of primary human dermal fibroblasts, and to compare their levels following treatment with TGFβ-1. A significant upregulation and enrichment of lysyl-oxidase-like 1, 2 and 4 and transglutaminase 2 were found. Western blotting confirmed the upregulation of lysyl hydroxylase 2 in the ECM. Increased transglutaminase activity in TGFβ-1 treated ECM was revealed from a cell-based assay. We employed a mass spectrometry-based method to identify alterations in the ECM cross-linking pattern caused by TGFβ-1. Cross-linking sites were identified in collagens I and V, fibrinogen and fibronectin. One cross-linking site in fibrinogen alpha was found only in TGFβ-treated samples. In conclusion, we have mapped novel cross-links between ECM proteins and demonstrated that activation of TGFβ signalling in cultured dermal fibroblasts upregulates multiple cross-linking enzymes in the ECM.     

High biorenewable content acrylate photocurable resins for DLP 3D printing

Green chemistry and green engineering concepts have been combined to develop novel sustainable polymeric materials. Solvent free photocurable acrylate resins with biorenewable carbon content of 75%–82% suitable for application in DLP 3D printing technology were composed by commercially available bio-based materials, acrylated epoxidized soybean oil (AESO), isobornyl methacrylate (IBOMA), methacrylic ester (ME), tetrahydrofurfuryl acrylate (THFA), and tetrahydrofurfuryl methacrylate (THFMA). They demonstrated high printing accuracy and good adhesion between layers. The monitoring of photocross-linking kinetics of high biorenewable content acrylate photoresins by the real-time photorheometry and analysis of their rheological parameters was carried out. Synthesized polymers exhibited high yield of insoluble fraction and thermal decomposition temperature at the weight loss of 10% above 300°C. Polymers AESO/IBOMA and AESO/THFMA showed the highest values of tensile modulus and tensile strength. Biodegradability of the synthesized polymers AESO/ME, AESO/THFA, and AESO/THFMA was investigated by measuring oxygen consumption in a closed respirometer. Such AESO-based polymers can be a competitive solution to replace petroleum-derived polymeric materials in additive manufacturing and reduce the environmental impact.     

交联改性对敷料用壳聚糖/聚氧化乙烯纳米纤维膜性能的影响

为改善壳聚糖基纳米纤维膜的耐水性和结构稳定性,对静电纺丝制得的壳聚糖/聚氧化乙烯(PEO)纳米纤维膜进行戊二醛交联改性,研究不同交联时间下纳米纤维膜在模拟人体缓冲液中微观形态结构、化学结构和结晶结构的变化,并对交联后纤维膜的耐水性和力学性能进行表征。结果表明:壳聚糖基纳米纤维膜经戊二醛交联处理后,在缓冲液中浸泡24 h纤维形态的稳定性得到明显改善,且随着交联时间的增加,纤维膜在缓冲液中的吸水率逐渐增加,溶失率逐渐降低;交联改性改变了壳聚糖大分子固有的结晶结构,使纤维膜的初始模量提高,力学强度随交联时间的增加先增加后降低。     

Improvement of gel properties of mackerel mince by phlorotannin extracts from sporophyll of Undaria pinnatifidai and UVA induced cross-linking

The effects of phlorotannin extracts (PTE) (from sporophyll of Undaria pinnatifida) added at different concentration (0, 1.6, 8, and 40 mg/g protein) with and without ultraviolet A (UVA) irradiation treatment on gel properties of mackerel (Scomberomorus niphonius) mince (MM) were investigated. The results indicated that both the breaking force and water-holding capacity (WHC) of the MM gel increased with addition of PTE, and the highest breaking force and WHC were observed with 40 mg/g PTE under UVA irradiation. Low-field nuclear magnetic resonance revealed that free water significantly decreased in this PTE-MM gel as well. UVA irradiation treatment led to reduction of total sulfhydryls and free amines in the PTE-MM gel, indicating more cross-linking between proteins. Electrophoresis results indicated that myosin heavy chains were aggregated in the UVA-treated PTE-MM gel. The microstructure of the UVA-treated PTE-MM gel showed that protein formed more evenly distributed cross-linked structures and was more compact than the untreated control gel. As a conclusion, PTE addition with UVA irradiation is shown to improve gelling properties of mackerel mince.     

Functional chemical modification of a porcine acellular dermal matrix with a modified naturally derived polysaccharide crosslinker

Antibacterial and physicochemical properties are generally considered important features of the porcine acellular dermal matrix (pADM). Oxidized 2-hydroxypropyltrimethyl ammonium chloride chitosan (OHTCC) was applied to crosslink with pADM at dosages of 1, 2, 4, 8, and 16%. The properties of the crosslinked pADM (OHTCC-pADM) were evaluated. DSC and TG analysis suggested that crosslinking could promote the thermal stability, the highest T_d, and T_max of OHTCC-pADM (8%) was 80 °C and 325 °C, which has been improved by 15 °C and 13 °C, respectively. While FTIR and AFM tests indicated that the structure integrity of collagen could still be maintained. SEM tests demonstrated the sustained three-dimensional architecture of OHTCC-pADM with appropriate porosity. Moreover, OHTCC-pADM exhibited improved ability to resist collagenase degradation, the degradation rate of 4%-, 8%-OHTCC-pADM was <50%. The tensile strength of OHTCC-pADM proved to be superior compared to pADM. Furthermore, 8%-OHTCC-pADM exhibited nearly 90% antibacterial activity against Escherichia coli, and Staphylococcus aureus. In addition, the results of the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazoliumbromide study showed that the cytocompatibility of OHTCC-pADM decreased with the increasing the amount of OHTCC, but all relative proliferation rates were above 80%. In conclusion, our study revealed that OHTCC stabilized and functionalized pADM while preserving good cytocompatibility. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47633.     

High-performance molecular-separation ceramic membranes derived from oxidative cross-linked polytitanocarbosilane

Polytitanocarbosilane (TiPCS)-derived ceramic membranes were fabricated using a pre-ceramic polymer. Special attention was focused on a process of thermal-oxidative curing that was used to induce cross-linking and the effect of this process on the ceramic yield, thermal stability, oxidation resistance, and microstructure of TiPCS. The cross-linked TiPCS powders showed a ceramic yield and thermal stability that were higher than that from the non-cross-linked version. In addition, the cross-linked TiPCS with uniform micropores showed higher levels of N₂ and CO₂ adsorption capacity, BET surface area, and micropore volume than the non-cross-linked versions, and the cross-linking process enhanced the stability of the pore structure at high temperature. The cross-linked TiPCS membranes showed high H₂ permeance (1.49 × 10⁻⁶ mol/(m² s Pa)) with sub-nanopores (H₂/SF₆ selectivity: 12 000, H₂/N₂: 10), and in addition higher oxidation resistance than their non-cross-linked counterparts. Furthermore, the influence of the concentration of the TiPCS precursor coating solution was optimized and the hydrothermal stability of the membranes at high temperatures was also evaluated. The optimized membrane demonstrated great performance for the pervaporation removal of methanol in binary azeotropic systems of either MeOH/butyl acetate or MeOH/toluene, and it also showed high hydrothermal stability with excellent dehumidification performance under high temperatures.     

Bactericidal effect of cationic hydrogels prepared from hydrophilic polymers

This study investigated whether hydrogels comprising hydrophilic cationic polymers have similar bactericidal effects. Bacteria were seeded on hydrogels and agar and their viability was assessed with time. Cationic hydrogels displayed bactericidal effects upon long-term bacterial contact. Furthermore, we assessed the areal density of cationic monomer unit of the cationic hydrogels, water content, and the initial elastic modulus. We examined correlations between each factor and bacterial death ratios; consequently, the bacterial death ratios were strongly correlated with the areal density of cationic hydrogel monomers. Elastic energy (W_el) generated at the cytomembrane ion-binding region and the cationic hydrogel and the cytomembrane interfacial energy (W_f) were estimated; consequently, W_el exceeded W_f at higher contact areas. The cationic hydrogel may extract cytomembranes with a reasonable adsorption area. Therefore, cationic hydrogels may be used as probes for ultrasonic echo to sterilize medical equipment.