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• Glomerular basement membranes are compressible ultrafilters with increased molecular selectivity with increased transmembrane pressure. • Compression effects on glomerular basement membrane sieving are mitigated by crosslinking and stiffening. • Disease-mediated changes in glomerular basement membrane mechanics may contributed to loss of glomerular size selectivity in the setting of chronic kidney disease. Proteinuria, the presence of high molecular weight proteins in the urine, is a primary indicator of chronic kidney disease. Proteinuria results from increased molecular permeability of the glomerular filtration barrier combined with saturation or defects in tubular protein reabsorption. Any solute that passes into the glomerular filtrate traverses the glomerular endothelium, the glomerular basement membrane, and the podocyte slit diaphragm. Damage to any layer of the filter has reciprocal effects on other layers to increase glomerular permeability. The GBM is thought to act as a compressible ultrafilter that has increased molecular selectivity with increased pressure due to compression that reduced the porosity of the GBM with increased pressure. In multiple forms of chronic kidney disease, crosslinking enzymes are upregulated and may act to increase GBM stiffness. Here we show that enzymatically crosslinking porcine GBM with transglutaminase increases the stiffness of the GBM and mitigates pressure-dependent reductions in molecular sieving coefficient. This was modeled mathematically using a modified membrane transport model accounting for GBM compression. Changes in the mechanical properties of the GBM may contribute to proteinuria through pressure-dependent effects on GBM porosity. [ABSTRACT FROM AUTHOR]

Idiopathic pulmonary fibrosis (IPF), for which effective treatments are limited, results in excessive and disorganized deposition of aberrant extracellular matrix (ECM). An altered ECM microenvironment is postulated to contribute to disease progression through inducing profibrotic behavior of lung fibroblasts, the main producers and regulators of ECM. Here, we examined this hypothesis in a 3D in vitro model system by growing primary human lung fibroblasts in ECM-derived hydrogels from non-fibrotic (control) or IPF lung tissue. Using this model, we compared how control and IPF lung-derived fibroblasts responded in control and fibrotic microenvironments in a combinatorial manner. Culture of fibroblasts in fibrotic hydrogels did not alter in the overall amount of collagen or glycosaminoglycans but did cause a drastic change in fiber organization compared to culture in control hydrogels. High-density collagen percentage was increased by control fibroblasts in IPF hydrogels at day 7, but decreased at day 14. In contrast, IPF fibroblasts only decreased the high-density collagen percentage at day 14, which was accompanied by enhanced fiber alignment in IPF hydrogels. Similarly, stiffness of fibrotic hydrogels was increased only by control fibroblasts by day 14 while those of control hydrogels were not altered by fibroblasts. These data highlight how the ECM-remodeling responses of fibroblasts are influenced by the origin of both the cells and the ECM. Moreover, by showing how the 3D microenvironment plays a crucial role in directing cells, our study paves the way in guiding future investigations examining fibrotic processes with respect to ECM remodeling responses of fibroblasts. In this study, we investigated the influence of the altered extracellular matrix (ECM) in Idiopathic Pulmonary Fibrosis (IPF), using a 3D in vitro model system composed of ECM-derived hydrogels from both IPF and control lungs, seeded with human IPF and control lung fibroblasts. While our results indicated that fibrotic microenvironment did not change the overall collagen or glycosaminoglycan content, it resulted in a dramatically alteration of fiber organization and mechanical properties. Control fibroblasts responded differently from IPF fibroblasts, highlighting the unique instructive role of the fibrotic ECM and the interplay with fibroblast origin. These results underscore the importance of 3D microenvironments in guiding pro-fibrotic responses, offering potential insights for future IPF therapies as well as other fibrotic diseases and cancer. [Display omitted] [ABSTRACT FROM AUTHOR]

To develop dual-functional etchants that could demineralize and stabilize dentin collagen simultaneously, and to assess the effects of these etchants on collagen crosslinking, biostability and resin bonding properties under clinically relevant conditions. Dual-functional etchants were prepared by mixing 56% glycolic acid and 17% phosphoric acid and adding 1% of theaflavins (TF) or proanthocyanidins from grape seed extract (GSE). The etchant without crosslinker was used as control. The prepared human dentin specimens were treated with the 3 etchants for 30 s and analyzed for chemical interaction using Fourier transform infrared spectroscopy and resistance of the demineralized layer to collagenase degradation using electron microscopy (EM). Resin-dentin interfacial bonding properties were evaluated after 24 h and after 10,000 thermocycling through microtensile bond strength (μTBS), nanoleakage and matrix metalloproteinases (MMPs) activity via in situ zymography. Statistical analysis was done using ANOVA and post- hoc Tuckey's test. Compared to control, TF and GSE dual-functional etchants were able to demineralize dentin, induce collagen crosslinking and protect the demineralized layer from collagenase degradation within 30 s. High resolution EM images showed better protection with TF etchant compared to GSE. There was a significant reduction in μTBS and an increase in nanoleakage and MMPs activity in control after thermocycling (p < 0.05) while these changes weren't seen in dual-functional etchants. Dual-functional etchants, especially TF containing, provide collagen protection against degradation and result in stable μTBS and less nanoleakage and MMPs activity under clinically relevant conditions. [ABSTRACT FROM AUTHOR]

It is desired to develop proton exchange membranes (PEMs) working in a wide temperature range considering the practical working condition of devices using the PEMs as the electrolyte. Herein, a novel polymer of poly (isatin biphenyl spirofluorene) (PIBS) is first synthesized and it is afterwards crosslinked by 1,3-bis(4-piperidyl) propane (P) to fabricate membranes. The membranes can work in a temperature range of −40 to 160 °C after doping with phosphoric acid (PA). The proton conductivity of the PA doped membrane reaches 4.4 × 10−3 S cm−1 at −40 °C under 80% relative humidity (RH) and 0.16 S cm−1 at 160 °C without humidifying. We demonstrate the uses of the prepared PA doped PIBS-P membranes as membrane electrolytes in single fuel cells within 100–160 °C under anhydrous condition, and in water electrolytic cells within −20 to 60 °C, respectively. Crosslinked poly (isatin biphenyl spirofluorene) membranes exhibit remarkable proton conductivity of 4.4 × 10−3 S cm−1 at −40 °C and 0.16 S cm−1 at 160 °C using as the membrane electrolyte in both water electrolysis cell and fuel cell within a wide temperature range. [Display omitted] • Novel cross-linked proton exchange membranes working from −40 to 160 °C. • Reaching the highest proton conductivity of 4.4 × 10−3 S cm−1 at −40 °C and 0.16 S cm−1 at 160 °C. • Demonstration as membrane electrolytes in both water electrolysis and fuel cell. [ABSTRACT FROM AUTHOR]

The human amniotic membrane (AM), a collagen-based extracellular matrix, is routinely used for wound coverage and nerve or tendon protection. However, its limited mechanical properties and rapid biodegradability restrict its applicability. In this work, we have used several strategies to improvise the biocompatibility, mechanical and antimicrobial properties of AM. We decellularized AM using sodium deoxycholate and Triton-X 100 and crosslinked it with glutaraldehyde (GA). The crosslinked tissues were detoxified with citric acid, glycine, glutamic acid and sodium borohydride and subsequently treated with ethanol to improve anti-calcification properties. The cross-linking efficiency was determined by uniaxial tensile testing, enzymatic degradation and quantification of free amine groups. The detoxification treatment drastically reduced free aldehydes and cytotoxicity. The overall processing significantly enhanced the biomechanical and non-antigenic properties of AM and also reduced its biodegradation and bacterial adhesion ability. Thus, we demonstrate that an acellular-crosslinked-detoxified AM would be an attractive scaffold for tissue engineering and regenerative medicine applications. [Display omitted] • Efficient decellularization method was developed for amniotic membrane (AM). • Crosslinked AM improved mechanical strength and reduced the biodegradation rate. • Detoxification enhanced the biocompatibility of crosslinked AM. • The crosslinked and detoxified AM prevents bacterial adhesion. [ABSTRACT FROM AUTHOR]

Gelcasting is a kind of colloidal processing with many attractive advantages for fabricating ceramics. In this study, a new and simple gelcasting system with only two additives was investigated using Isobam (a copolymer of isobutylene and maleic anhydride) both as dispersant and monomer, and Tetraethylenepentamine (TEPA) as crosslinker. The gelation studies in solutions showed the reaction between Isobam and TEPA was an acylation reaction which was controlled by temperature and concentration. The rheological behavior and samples' properties of 50 vol% Al 2 O 3 slurries with different Isobam contents were studied. With 8 wt% of Isobam by water, the dried green bodies had relatively density of 56.3% and flexural strength of 25.7 ± 2.2 MPa. After sintering at 1530 °C for 3 h, the relatively density and flexural strength of sintered ceramics were 98.7% and 416 ± 19 MPa respectively. The SEM and macroscopic results showed that dried green bodies and sintered ceramics with homogeneous and defect–free morphology were obtained by using Isobam–TEPA system. [ABSTRACT FROM AUTHOR]

[Display omitted] The ability to reverse engineer the silkworm fiber has led to tremendous advancements in the field of silk materials over the last several decades, with silk fibroin materials applied to biomedical, food, and high technology industries. This progress is largely due to the ability to process silk into a regenerated silk fibroin solution that can be engineered into a variety of material formats and stabilized by the reintroduction of the non-covalent native β-sheet protein structure. The next revolution in silk materials involves stabilizing silk fibroin through covalent crosslinking and plasticization. These approaches have transformed silk into a material that is not only strong, but also elastic and flexible, making it compatible with modern fabrication approaches. This has significantly broadened silk material fabrication strategies to include photolithography, digital light processing, and extrusion-based 3D printing. As a result, silk can now be used in a range of applications including ocular prostheses, bio-adhesives, tissue engineering matrices, green biodegradable LEDs and batteries, on-skin and implantable sensors, and bioplastics. In this review, we discuss the evolution of crosslinking in silk materials, focusing on covalent tyrosine- and methacrylate-based crosslinks, and on the structural changes and crosslinking brough about by plasticizing silk using glycerol and calcium ions. We describe how advances in silk crosslinking led to the development of unique materials, paving the way for new fabrication approaches and applications across multiple industries, ushering in a new era of silk materials. [ABSTRACT FROM AUTHOR]

Chitosan microspheres are used in the biotechnological, biomedical, and enzyme immobilization fields. This study synthesized lysozyme-chitosan microspheres by crosslinking and covalent attachment. The synthesis conditions were adjusted, and spherical particles content lysozyme were obtained and characterized by Scanning electron microscopy (SEM) and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Activity and stability assays were conducted to determine the immobilization method's influence, and the kinetics parameters were calculated. The enzymatic activity recovery yields of 65.8% and 20.0% were obtained for crosslinking and covalent attachment, respectively. Surface lysozyme-chitosan microspheres' enzymatic activity was obtained by covalent attachment. By the crosslinking method, surface and into particle enzyme activity were observed. The functionalization of cotton fabric was achieved, and the impregnation slightly modified cotton fabric properties such as resistance and permeability. Finding antimicrobial properties against bacteria S. aureus and P. aeruginosa , with a growth of 49.12% and 65.31%, respectively, were obtained. [Display omitted] • Crosslinking and covalent attachment methods to lysozyme immobilization was used. • Micro-size spherical particles of lysozyme and chitosan were obtained. • Cotton fabric was functionalized, strength and permeability were not affected. • Antimicrobial activity in S. aureus and P. aeruginosa was shown. [ABSTRACT FROM AUTHOR]

Cation-associated cytotoxicity limits the systemic administration of RNA delivery in vivo , demanding the development of non-cationic nanosystems. In this study, cation-free polymer-siRNA nanocapsules with disulfide-crosslinked interlayer, namely T-SS(-), were prepared via the following steps: 1) complexation of siRNA with a cationic block polymer cRGD-poly(ethylene glycol)- b -poly[(2-aminoethanethiol)aspartamide]- b -poly{ N' -[ N -(2-aminoethyl)-2-ethylimino-1-aminomethyl]aspartamide}, abbreviated as cRGD-PEG-PAsp(MEA)-PAsp(C=N-DETA), 2) interlayer crosslinking via disulfide bond in pH 7.4 solution, and 3) removal of cationic DETA pendant at pH 5.0 via breakage of imide bond. The cationic-free nanocapsules with siRNA cores not only showed great performance (such as efficient siRNA encapsulation, high stability in serum, cancer cell targeting via cRGD modification, and GSH-triggered siRNA release), but also achieved tumor-targeted gene silencing in vivo. Moreover, the nanocapsules loaded with siRNA against polo-like kinase 1 (siRNA-PLK1) significantly inhibited tumor growth without showing cation-associated toxicity side effects and remarkably improved the survival rate of PC-3 tumor-bearing mice. The cation-free nanocapsules could potentially serve as a safe and effective platform for siRNA delivery. Cation-associated toxicity limits the clinical translation of cationic carriers for siRNA delivery. Recently, several non-cationic carriers, such as siRNA micelles, DNA-based nanogels, and bottlebrush-architectured poly(ethylene glycol), have been developed to deliver siRNA. However, in these designs, siRNA as a hydrophilic macromolecule was attached to the nanoparticle surface instead of being encapsulated. Thus, it was easily degraded by serum nuclease and often induced immunogenicity. Herein, we demonstrate a new type of cation-free siRNA-cored polymeric nanocapsules. The developed nanocapsules not only showed capacities including efficient siRNA encapsulation, high stability in serum, and cancer cell targeting via cRGD modification, but also achieved an efficient tumor-targeted gene silencing in vivo. Importantly, unlike cationic carriers, the nanocapsules exhibited no cation-associated side effects. [Display omitted] [ABSTRACT FROM AUTHOR]

The primary source of strength in menisci, tendons, and ligaments are hierarchical collagen fibers; however, these fibers are not regenerated after injury nor in engineered replacements, resulting in limited repair options. Collagen strength is reliant on fiber alignment, density, diameter, and crosslinking. Recently, we developed a culture system which guides cells in high-density collagen gels to develop native-like hierarchically organized collagen fibers, which match native fiber alignment and diameters by 6 weeks. However, tensile moduli plateau at 1MPa, suggesting crosslinking may be lacking. Collagen crosslinking is regulated by lysyl oxidase (LOX) which forms immature crosslinks that condense into mature trivalent crosslinks. Trivalent crosslinks are thought to be the primarily source of strength in fibers, but it's not well understood how they form. The objective of this study was to evaluate the effect of exogenous LOX in our culture system at different stages of hierarchical fiber formation to produce stronger replacements and to better understand factors affecting crosslink maturation. We found treatment with LOX isoform LOXL2 did not restrict hierarchical fiber formation, with constructs still forming aligned collagen fibrils by 2 weeks, larger fibers by 4 weeks, and early fascicles by 6 weeks. However, LOXL2 treatment did significantly increase mature pyridinium (PYD) crosslink accumulation and tissue mechanics, with timing of LOXL2 supplementation during fiber formation having a significant effect. Overall, we found one week of LOXL2 supplementation at 4 weeks produced constructs with native-like fiber organization, increased PYD accumulation, and increased mechanics, ultimately matching the tensile modulus of immature bovine menisci. Collagen fibers are the primary source of strength and function in connective tissues throughout the body, however it remains a challenge to develop these fibers in engineered replacements, greatly reducing treatment options. Here we demonstrate lysyl oxidase like 2 (LOXL2) can be used to significantly improve the mechanics of tissue engineered constructs, but timing of application is important and will most likely depend on degree of collagen organization or maturation. Currently there is limited understanding of how collagen crosslinking is regulated, and this system is a promising platform to further investigate cellular regulation of LOX crosslinking. Understanding the mechanism that regulates LOX production and activity is needed to ultimately regenerate functional repair or replacements for connective tissues throughout the body. [Display omitted] [ABSTRACT FROM AUTHOR]

Valvular heart disease is a major threat to human health and transcatheter heart valve replacement (THVR) has emerged as the primary treatment option for severe heart valve disease. Bioprosthetic heart valves (BHVs) with superior hemodynamic performance and compressibility have become the first choice for THVR, and more BHVs have been requested for clinical use in recent years. However, several drawbacks remain for the commercial BHVs cross-linked by glutaraldehyde, including calcification, thrombin, poor biocompatibility and difficulty in endothelialization, which would further reduce the BHVs' lifetime. This study developed a dual-functional non-glutaraldehyde crosslinking reagent OX-VI, which can provide BHV materials with reactive double bonds (C C) for further bio-function modification in addition to the crosslinking function. BHV material PBAF@OX-PP was developed from OX-VI treated porcine pericardium (PP) after the polymerization with 4-vinylbenzene boronic acid and the subsequent modification of poly (vinyl alcohol) and fucoidan. Based on the functional anti-coagulation and endothelialization strategy and dual-functional crosslinking reagent, PBAF@OX-PP has better anti-coagulation and anti-calcification properties, higher biocompatibility, and improved endothelial cells proliferation when compared to Glut-treated PP, as well as the satisfactory mechanical properties and enhanced resistance effect to enzymatic degradation, making it a promising candidate in the clinical application of BHVs. Transcatheter heart valve replacement (THVR) has become the main solution for severe valvular heart disease. However, bioprosthetic heart valves (BHVs) used in THVR exhibit fatal drawbacks such as calcification, thrombin and difficulty for endothelialization, which are due to the glutaraldehyde crosslinking, resulting in a limited lifetime to 10-15 years. A new non-glutaraldehyde cross-linker OX-VI has been designed, which can not only show great crosslinking ability but also offer the BHVs with reactive double bonds (C C) for further bio-function modification. Based on the dual-functional crosslinking reagent OX-VI, a versatile modification strategy was developed and the BHV material (PBAF@OX-PP) has been developed and shows significantly enhanced anticoagulant, anti-calcification and endothelialization properties, making it a promising candidate in the clinical application of BHVs. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of sustainable and biodegradable composites has gained increasing attention in recent years. Effective interaction and adhesion between polymers and fillers are crucial. In this study, the effect of different aspect ratios of cellulose nanocrystals (CNCs) and their hybrid within a crosslinked poly (vinyl alcohol) (PVA) nanocomposite has been investigated to develop biodegradable materials. The physicochemical, thermal, and mechanical properties of the specimens have been studied. SEM images indicate that the addition of CNC reduced the porosity of the films. The XPS results confirmed the significant formation of covalent bonds for all composites except those reinforced with wood-CNC, which showed a lower amount of crosslinking and C C formation. EDS maps reveals that the dispersity of the CNCs could be different depending on the aspect ratio of the CNCs. Results from the solubility in water (SW) tests indicated that the use of hybrid-CNC in a crosslinked system decreased the SW significantly. The crosslinking and addition of CNC to the PVA composite led to improved mechanical properties. Elongation at break (EB) decreased significantly for the crosslinked hybrid-CNC nanocomposite. Overall, the results of this study indicate that the aspect ratio of CNCs as fillers in nanocomposites may contribute to their physicochemical, mechanical, and thermal properties for the development of biodegradable materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Enhancing the electrochemical performance while maintaining excellent mechanical properties of carbon nanofiber-based flexible electrodes remains a significant challenge, which blocks their potential application in advanced energy storage and conversion. Herein, taking advantage of the thermal stability difference between polyacrylonitrile and polypyrrolidone, we report a simple strategy to fabricate N-doped porous carbon nanofiber membranes with inter-fiber cross-linked structures via eccentric coaxial electrospinning combined with carbonization processes. During carbonization processes, the obstacles of large contact resistance are removed and sufficient contacts among electrospun nanofibers are formed, endowing the carbon nanofiber membranes with outstanding electrical conductivity (25.4 S cm−1) and flexibility in various forms. Further, NiCo 2 O 4 nanoneedles are in-situ decorated onto the prepared carbon nanofiber membranes to construct hybrid electrodes for improving capacitance. The hybrid electrodes (NiCo 2 O 4 @NPCNFs) achieve a competitive specific capacitance (capacity) of 1474.2 F g−1 (245.4 mAh g−1) at the current density of 0.5 A g−1, as well as good rate performance (78.0% capacitance retention at a current density of 10 A g−1). In addition, the assembled asymmetric supercapacitors exhibit a high energy density of 53.0 Wh kg−1. This study paves a promising way toward carbon nanofiber-based electrodes for application in energy storage systems. [Display omitted] • According to the different thermal stabilities of the polymers, cross-linked electrospun carbon nanofibers are prepared. • Design eccentric core-shell nanofibers to facilitate the outflow of the melting core to form abundant crosslinking points. • The novel carbon nanofiber membranes render robust flexibility and high electrical conductivity. • The assembled flexible supercapacitor can supply power stably and continuously even under severe bending states. [ABSTRACT FROM AUTHOR]

To develop and assess new dosage forms for the alternative to existing oral medication for peripheral neuropathy, a hydrogel film in the skin patch formation containing tramadol hydrochloride (TRA), a water-soluble drug used as an analgesic, was prepared and evaluated. A hydrogel film composed of 20%(w/w) hydroxypropyl methylcellulose (HPMC) irradiated with electron beams had high transparency and elasticity similar to commercially available wound dressings and soft tissues, suggesting that it is a suitable substrate for TRA. The inclusion of TRA was enabled by immersing the HPMC hydrogel film in TRA aqueous solution. The release and skin permeation of TRA from TRA-containing hydrogel films differed depending on the electron beam dose. Moreover, the analgesic effects in mice were confirmed in a dose-dependent manner. This study demonstrated the usefulness of a hydrogel film containing TRA as a new dosage form alternative to the existing oral medication for peripheral neuropathy. [Display omitted] [ABSTRACT FROM AUTHOR]

Silk sericin is a class of protein biopolymers produced by silkworms. Increasing attention has been paid to silk sericin for biomedical applications in the last decade, not only because of its excellent biocompatibility and biodegradability but also due to the pharmacological activities stemming from its unique amino acid compositions. In this review, the biological properties of silk sericin, including curing specific diseases and promoting tissue regeneration, as well as underlying mechanisms are summarized. We consider the antioxidant activity of silk sericin as a fundamental property, which could account for partial biological activities, despite the exact mechanisms of silk sericin's effect remaining unknown. Based on the reactive groups on silk sericin, approaches of bottom-up fabrication of silk sericin-based biomaterials are highlighted, including non-covalent interactions and chemical reactions (reduction, crosslinking, bioconjugation, and polymerization). We then briefly present the cutting-edge advances of silk sericin-based biomaterials applied in tissue engineering and drug delivery. The challenges of silk sericin-based biomaterials are proposed. With more bioactivities and underlying mechanisms of silk sericin uncovered, it is going to boost the therapeutic potential of silk sericin-based biomaterials. [Display omitted] • Silk sericin is not only a biocompatible building block of materials but also a bioactive therapeutic. • The pharmacological activities of silk sericin and its possible mechanisms are summarized. • The bottom-up approaches to developing silk sericin-based biomaterials are summarized. • The applications and limitations of silk sericin-based biomaterials are reviewed. [ABSTRACT FROM AUTHOR]

The structural and functional properties of collagen are modulated by the presence of intramolecular and intermolecular crosslinks. Advanced Glycation End-products (AGEs) can produce intermolecular crosslinks by bonding the free amino groups of neighbouring proteins. In this research, the following hypothesis is explored: The accumulation of AGEs in collagen decreases its proteolytic degradation rates while increasing its stiffness. Fluorescence Lifetime Imaging (FLIM) and Fourier-transform infrared spectroscopy (FTIR) detect biochemical changes in collagen scaffolds during the glycation process. The accumulation of AGEs increases exponentially in the collagen scaffolds as a function of Methylglyoxal (MGO) concentration by performing autofluorescence measurement and competitive ELISA. Glycated scaffolds absorb water at a much higher rate confirming the direct affinity between AGEs and interstitial water within collagen fibrils. In addition, the topology of collagen fibrils as observed by Atomic Force Microscopy (AFM) is a lot more defined following glycation. The elastic modulus of collagen fibrils decreases as a function of glycation, whereas the elastic modulus of collagen scaffolds increases. Finally, the enzymatic degradation of collagen by bacterial collagenase shows a sigmoidal pattern with a much slower degradation rate in the glycated scaffolds. This study identifies unique variations in the properties of collagen following the accumulation of AGEs. In humans, Advanced Glycation End-products (AGEs) are naturally produced as a result of aging process. There is an evident lack of knowledge in the basic science literature explaining the biomechanical impact of AGE-mediated crosslinks on the functional and structural properties of collagen at both the nanoscale (single fibrils) and mesoscale (bundles of fibrils). This research, demonstrates how it is possible to harness this natural phenomenon in vitro to enhance the properties of engineered collagen fibrils and scaffolds. This study identifies unique variations in the properties of collagen at nanoscale and mesoscale following accumulation of AGEs. In their approach, they investigate the unique properties conferred to collagen, namely enhanced water sorption, differential elastic modulus, and finally sigmoidal proteolytic degradation behavior. [Display omitted] [ABSTRACT FROM AUTHOR]

Flexible stab-proof membrane is a promising form of anti-stabbing material. The polyvinyl alcohol (PVA), which has good chemical stability, membrane-forming property and degradability, is an ideal choice for preparing membrane materials. However, the mechanical properties of pure PVA membranes are limited, and crosslinking is an effective method to improve the mechanical properties of PVA membrane materials. In present research, tannic acid (TA) and sodium borate (SB) additives were selected as crosslinking agents to prepare PVA composite membranes, and different mass ratios were set to explore the effects of the types and amounts of crosslinking agents on the mechanical properties of the PVA composite materials, especially the stab-proof properties. The principle of the cross-linking was investigated by FTIR and XRD tests, the thermal properties of the composite membranes were investigated by TG and XRD, and the mechanical properties of the composite membranes were comprehensively compared by tensile and puncture test. The results show that the puncture resistance of PVA-SB composite membranes and PVA-TA composite membranes reached the best when the mass ratio is 15:1 and 25:1, respectively, which is 75.76 % and 79.15 % higher than that of pure PVA composite membrane. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to the increased presence of hydrophilic groups in waterborne polyurethane (WPU) coatings, consequently leading to compromised corrosion resistance and reduced service life. To solve the problem, a series of waterborne polyurethanes were synthesized via internal emulsification using dicyclohexylmethane diisocyanate (HMDI) and polytetrahydrofuran ether diol (PTMG) as the primary raw materials. The triethanolamine (TEOA) was used as a crosslinking agent and corrosion inhibitor, while N- (β-aminoethyl) -γ-aminopropyl trimethyl-(ethyl) oxy-silane (KH-792) was introduced as a coupling agent to establish a system with a dual crosslinking structure. The crosslinking degree of the double network structure can be adjusted by changing the amount of KH-792. Then the influence of KH-792 content on the performance of SWPU dispersions and film were studied. The research shows that the waterborne polyurethane with a KH-792 content of 3 wt% exhibits exceptional mechanical strength, reaching 34.64 MPa, with only 3.32 % water absorption and an adhesion strength of 2.64 MPa. Furthermore, it exhibited a high impedance modulus (2976.4 Ω/cm2) at low frequencies. Therefore, this compound holds promising potential for application in anti-corrosion coatings field. • The successful preparation of WPU with a double crosslinking network was achieved. • The WPU molecular chain was modified by incorporating varying amounts of the silane coupling agent KH-792. • The WPU film exhibits excellent mechanical properties and demonstrates high water resistance. • The prepared WPU film exhibits excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

Adhesives that rely on a curing mechanism struggle to function in underwater environments due to detrimental interactions with water. One strategy to overcome this involves protecting sensitive components in mechanically responsive microcapsules. In this way, a two-part adhesive can be achieved via a single mixture, applied as one would apply a pressure sensitive adhesive. This work focused on improving polyurea microcapsule shell integrity, specifically focusing on the effect of additional thermal processing. The improved microcapsule shells displayed limited payload leakage with only an 8 % loss in pot life compared to the base isocyanate resin alone. A mixture of optimized microcapsules and isocyanate resin was evaluated against a wide range of substrates and conditions, including dry and wet environments. When microcapsules were intentionally ruptured to release the catalyst and crosslinker payload, the microcapsule-isocyanate mixture had improved adhesive strength (506 %) compared to the base isocyanate resin without microcapsules. [Display omitted] [ABSTRACT FROM AUTHOR]

Both high-cycle fatigue life and fatigue crack propagation resistance of human cortical bone allograft are radiation dose-dependent between 0 and 25 kGy such that higher doses exhibit progressively shorter lifetimes. Recently, we have shown that collagen chain fragmentation and stable crosslink accumulation may contribute to the radiation dose-dependent loss in fatigue crack propagation resistance of human cortical bone. To our knowledge, the influence of these mechanisms on high-cycle fatigue life of cortical bone have not been established. Sequential irradiation has also been shown to mitigate the loss of fatigue life of tendons, however, whether this mitigates losses in fatigue life of cortical bone has not been explored. Our objectives were to evaluate the influence of radiation-induced collagen chain fragmentation and crosslinking on the high-cycle fatigue life of cortical bone in the dose range of 0–15 kGy, and to evaluate the capability of sequential irradiation at 15 kGy to mitigate the loss of high-cycle fatigue life and radiation-induced collagen damage. High-cycle fatigue life specimens from four male donor femoral pairs were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and 15 kGy sequentially irradiated) and subjected to high-cycle fatigue life testing with a custom rotating-bending apparatus at a cyclic stress of 35 MPa. Following fatigue testing, collagen was isolated from fatigue specimens, and collagen chain fragmentation and crosslink accumulation were quantified using SDS-PAGE and a fluorometric assay, respectively. Both collagen chain fragmentation (p = 0.006) and non-enzymatic crosslinking (p < 0.001) influenced high-cycle fatigue life, which decreased with increasing radiation dose from 0 to 15 kGy (p = 0.016). Sequential irradiation at 15 kGy did not offer any mitigation in high-cycle fatigue life (p = 0.93), collagen chain fragmentation (p = 0.99), or non-enzymatic crosslinking (p ≥ 0.10) compared to a single radiation dose of 15 kGy. Taken together with our previous findings on the influence of collagen damage on fatigue crack propagation resistance, collagen chain fragmentation and crosslink accumulation both contribute to radiation-induced losses in notched and unnotched fatigue life of cortical bone. To maximize the functional lifetime of radiation sterilized structural cortical bone allografts, pathways other than sequential radiation should be explored to mitigate collagen matrix damage. [Display omitted] • Collagen chain fragmentation negatively affects cortical bone fatigue life. • Collagen non-enzymatic crosslinking negatively affects cortical bone fatigue life. • Sequential irradiation does not preserve fatigue life of irradiated cortical bone. • Fatigue life of cortical bone is radiation dose-dependent from 0 to 15 kGy. [ABSTRACT FROM AUTHOR]

In this contribution, we reported a new approach to crosslink linear polyurethane (PU) with dynamic boronic ester bonds. First, a linear PU was synthesized, which carries a plethora of 1,3-diol structural units. Second, two structurally similar diboronic acids were designed and synthesized, which contained amino and amido groups, respectively. Thereafter, the crosslinking between the linear PU and the diboronic acids was carried out via the generation of boronic ester bonds. Thanks to the crosslinking, the PU networks significantly displayed improved thermomechanical properties, contingent on types of crosslinkers. More importantly, the excellent reprocessing and shape memory properties were imparted to the PU networks, which were implemented by dynamic boronic ester bonds between 1,3-diol moieties of the linear PU and boronic acids of the crosslinkers. The dynamic exchange of boronic ester bonds is responsible for the reprocessing properties. For the shape memory properties, the PU networks featured the reprogramming behavior of original shapes via the dynamic exchange of boronic ester bonds. More importantly, the shape memory properties were also dependent on types of diphenylboronic acids, which was reflected with the difference in dynamicity of boronic ester bonds. For the PU networks with amino-containing crosslinker, the boronic ester bonds featured the B–N coordination. As a result, the boronic ester bonds had the increased dynamicity, which significantly affected the reprocessing properties. [Display omitted] • A linear polyurethane (PU) carrying a 1,3-diol structural units was synthesized. • The linear PU was crosslinked with two types of diphenylboronic acids. • It was demonstrated that B–N coordination was generated with diphenyl boronic acid bearing amino groups. • Generation of B–N coordination significantly affected the thermomechanical, shape memory and reprocessing properties of PU networks. [ABSTRACT FROM AUTHOR]

[Display omitted] • Scalable synthesis of l -Fmoc-NleSme-OH for peptide synthesis. • NleS+me2 and NleSe+me2 peptides were readily prepared. • Selenonium peptides are active to bind and crosslink methyllysine readers. Lysine methylation readers are an important class of proteins that bind site-specifically methylated proteins for downstream regulation. Chemical probes that crosslink lysine methylation readers are highly desired to investigate the proteins from cellular samples. We recently reported NleS+me2 (norleucine-ε-dimethylsulfonium) as dimethyllysine mimic selectively crosslinks corresponding methyllysine readers. Although the sulfonium tools exhibited great promise, the synthetic availability may limit broad applications. In order to incorporate the unnatural amino acid, l -Fmoc-NleSme-OH (Fmoc: fluorenyl methoxycarbonyl) was synthesized as an important building block for solid-phase peptide synthesis (SPPS) in the previous synthetic route. It took six steps with resolution of racemic mixture and radical mediated thiol-ene reaction. As a result, the synthesis was not scalable with only 4.4 % overall yield. Here we report a much-improved synthesis method so that diverse NleS+me2 peptides could be readily prepared. In addition, the new method enables preparation of selenonium peptides for methyllysine reader crosslinking. We thus believe this synthetic method will be widely used to prepare sulfonium and selenonium probes for site-selective crosslinking. [ABSTRACT FROM AUTHOR]

EPR spectra and DFT calculations was used to reveal the hindering mechanism of polydopamine on vulcanization, the results showed that the bond dissociation energy of polydopamine was lower than rubber matrix, so it prioritizes reacting with benzoyl peroxide, resulting in the conversion of active free radicals into stable free radicals, thus hindering the vulcanization of rubber. [Display omitted] • Dopamine affects the curing of silicone rubber by trapping free radicals when benzoyl peroxide is used as curing agent. • Electron paramagnetic resonance and reaction products showed that dopamine converted active free radicals into stable free radicals. • DFT calculations showed that benzoyl peroxide was more inclined to snatch hydrogen atoms from dopamine than from the rubber matrix, which led to the depletion of benzoyl peroxide and inadequate curing. Antioxidants are usually used to improve the anti-aging properties of rubber, however, which will hinder the vulcanization of rubber. It is great significance to reveal the hindrance mechanism for the preparation of high performance composites. There, a series of silica and dopamine modified silica filled silicone rubber compound were prepared, with benzoyl peroxide (BPO) as vulcanizator. The results show that, dopamine would inhibit the crosslinking of BPO, resulting in the decrease of the crosslinking density and the mechanical properties. Based on the vulcanization mechanism of BPO, it is speculated that dopamine hinders vulcanization by providing H atoms to consume BPO. The reaction product benzoic acid (BA) was detected on the surface, which was confirmed by mass spectrometry, 1H NMR, FT-IR, and XPS, which confirms the conjecture. EPR and DFT analysis further explained the hindrance mechanism of polydopamine (PDA) on vulcanization, which indicates that BPO preferentially abstract hydrogen from PDA rather than rubber, due to the low bond dissociation energy of PDA. This leads to the consumption of BPO, and reduces the concentration of free radicals used for vulcanization, resulting in insufficient crosslinking. Understanding the reaction mechanism of dopamine and BPO is of great significance for screening antioxidants for peroxide crosslinking system. [ABSTRACT FROM AUTHOR]

[Display omitted] • DLP offers a platform to control preceramic polymer crosslinking and ceramic yield in polymer-derived ceramics. • A correlation between pre-pyrolysis crosslinking density and post-pyrolysis ceramic yield is established. • Ceramic yield is enhanced from 64% to over 86%, even with the addition of volatile elements through rational design. • A one-pot DLP crosslinking of polycarbosilane and polycarbosiloxane epitomizes preceramic polymer hybridization strategy. • The findings contribute to sustainable preceramic polymers and organic-inorganic materials processing. Control of preceramic polymer crosslinking for UV-curable processing is essential for fine 3D printing with high ceramic conversion for sustainable polymer-derived ceramics (PDC) engineering. While various factors influencing ceramic yield have been studied, the systematic exploration of the relationship between crosslinking and ceramic yield, especially when crosslinking increases volatile elements, remains open for further investigation. This study addresses this gap by utilizing vat photopolymerization (VP) additive manufacturing (AM) as a versatile platform for controlling preceramic crosslinking and ceramic yield. By rationally designing and tuning the photochemical crosslinking through digital light processing (DLP), we demonstrate that the ceramic yield can be enhanced from 64% to over 86%, even with added volatile elements. We reveal that the post-pyrolysis ceramic yield can be closely correlated with the pre-pyrolysis crosslinking of the preceramic network represented by its stiffness. This correlation thereby suggests a fast, energy-efficient, non-destructive methodology to predict and improve ceramic yield. Combined with these findings, our one-pot thiol-ene hybridization of polycarbosilane and polycarbosiloxane via DLP offers an exemplary method to generate hybrid preceramic polymers with tailored material properties toward target applications, and potentially even higher ceramic yields. This study thus contributes to achieving better resource- and energy-efficient preceramic polymer and PDC processing routes toward sustainable, advanced organic–inorganic materials manufacturing. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is regarded as a promising next-generation high-performance separation membrane material. However, the flexiblility of single-layer GO nanosheets usually results in membrane with poor stability under practical conditions. In this study, we present a facile strategy to rapidly convert single-layer nanosheet GO membranes into supra-nanosheet GO (sGO) membranes with a loose rigid structure by a confined gelling and crosslinking process. The optimized sGO membrane exhibits remarkable water permeance and retention capability. With additional tailor-made nanopores, the water permeance of the sGO membrane could reach 52.0 LMH/bar, representing 10-fold increase compared to pristine GO membrane. Furtheermore, this membrane demonstrates excellent pressure stability and unique elasticity, enhancing its lorg-term operational reliability and reversible recovery. Hence, this innovative strategy provides a platform for the facily construction of highly stable 2D membranes with enhanced water transport channels. A novel supra-nanosheet GO (sGO) membrane with a unique loose rigid structure was developed utilizing a strategy termed as 'confined gelling and crosslinking induced membrane rigidityʼ. This sGO structure, composed of GO nanosheets, can be easily obtained by in situ crosslinking single-layer GO nanosheets under a confined gelling state. The innovative strategy resulted in the membrane (X-sGO) showing excellent antibiotic desalting performance and compressive stability, with the flux of the membrane reaching 52.0 LMH/bar, which was 10-fold higher than that of the pristine GO membrane. As a result, this approach offers a platform for the facile construction of highly loose rigid 2D membranes. [Display omitted] • A novel supra-nanosheet GO membrane with unique loose rigid structure by a confined gelling and crosslinking induced strategy. • The mechanical feature of GO based membranes were measured with Nanoindentation, approving our design. • The loose NF membrane exhibits superior water flux and high antibiotic/salt selectivity. [ABSTRACT FROM AUTHOR]

In the quest for greener and more efficient energy storage solutions, the exploration and utilization of renewable raw materials is essential. In this context, cellulose-derived separators play a central role in enhancing the performance of green energy storage devices. However, these often exhibit disadvantageous porosity and limited wet strength. Here, we demonstrate a facile approach to tailor thickness (ca. 40 μm), air permeability (0.1–200 cm3 s−1), and mechanical properties of separators by integration of up to 50 wt% microfibrillated cellulose (MFC) into paper sheets. While the MFC enhanced the formation of dense networks, these separators show a poor dimensional stability (folding and creasing) concomitant with a low strength under wet conditions, crucial for assembly and operation. Crosslinking with 1,2,3,4-butanetetracarboxylic acid (BTCA) however, led to an increase in wet strength by up to 6700 % while ensuring dimensional stability. The electrochemical performance, evaluated by impedance spectroscopy and galvanostatic cycling (7500 repetitions) showed comparable results as commercially available glass and polypropylene separators in terms of ion diffusion, charge-discharge rate performance, Ohmic loss and capacitance retention %. The approach demonstrates that disadvantages of paper-based separators in terms of dimensional stability and wet strength can be overcome by a paper technological approach using crosslinking strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

Fish gelatin-agar edible films have potential for sustainable food packaging, but their limitations particularly water sensitivity require improvement. In this research, the effects of radiation from gamma rays at rates ranging from 0 to 40 kGy on the films' mechanical characteristics, microstructure, color, opacity, and water resistance were examined. Overall, gamma irradiation at doses of up to 30 kGy substantially improved the water resistance of the gelatin-agar film, as demonstrated by decreased water solubility, water absorption, and film vapor permeability. This could be due to crosslinking within the biopolymer network. However, at doses of 40 kGy, potential chain scission in the film's polymeric structure might occur, which counteracts further improvement and consequently starts degrading its water resistance. Similarly, the improvement of film's tensile strength and modulus of elasticity peaked at an optimal dose of 30 kGy, and then decreased at higher doses, while the film's elongation at break remained unaffected. FTIR and SEM analysis supported changes in functional group and structural morphology in these observations. Although irradiation caused some yellowing, an optimal dose range (at around 20–30 kGy) was identified to achieve improved functionality without degrading film integrity. These findings highlight the potential of gamma irradiation as a viable technique for modifying fish gelatin-agar films for enhanced performance in food packaging applications. • Gamma irradiation (up to 30 kGy) significantly improved fish gelatin-agar film's water resistance. • Improved tensile strength & elasticity observed at 30 kGy, suggesting optimal crosslinking within the film. • Higher irradiation (40 kGy) led to decreased film performance, indicating potential chain scission. • FTIR & SEM analysis supported structural changes influencing film properties. • Optimal irradiation dose (20–30 kGy) achieved improved function without compromising film integrity. [ABSTRACT FROM AUTHOR]

Bioprinted hydrogels are extensively studied to provide an artificial matrix for 3D cell culture. The success of bioprinting hydrogels relies on fine-tuning their rheology and composition to achieve shear-thinning behavior. However, a challenge arises from the limited viscoelastic and stiffness range accessible from a single hydrogel formulation. Nevertheless, hydrogel mechanical properties are recognized as essential cues influencing cell phenotype, migration, and differentiation. Thus, it is crucial to develop a system to easily modulate bioprinted hydrogels' mechanical behaviors. In this work, we modulated the viscoelastic properties and stiffness of bioprinted hydrogels composed of fibrinogen, alginate, and gelatin by tuning the crosslinking bath solution. Various concentrations of calcium ionically crosslinked alginate, while transglutaminase crosslinked gelatin. Subsequently, we characterized the mechanical behavior of our bioprinted hydrogels from the nanoscale to the macroscale. This approach enabled the production of diverse bioprinted constructs, either with similar elastic behavior but different elastic moduli or with similar elastic moduli but different viscoelastic behavior from the same hydrogel formulation. Culturing fibroblasts in the hydrogels for 33 days revealed a preference for cell growth and matrix secretion in the viscoelastic hydrogels. This work demonstrates the suitability of the method to decouple the effects of material mechanical from biochemical composition cues on 3D cultured cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Few studies have been conducted on the relationship between the crosslinking ability of dialdehyde polysaccharides (DPs) with different structures and the structure and properties of hydrogels. Herein, the effects of dialdehyde sodium alginate (DSA), dialdehyde guar gum (DGG), and dialdehyde dextran (DDE) as crosslinking agents for gelatin (GE)-based hydrogels were comparatively studied. First, the structure and aldehyde content of DPs were evaluated. Subsequently, the structure, crosslinking degree, and physicochemical properties of GE/DP hydrogels were characterized. Compared with pure GE hydrogels, GE/DP hydrogels had higher thermal stability and mechanical properties. Moreover, the aldehyde content of DPs was ordered as follows: DSA < DGG < DDE. The higher crosslinking degree of the hydrogels formed by DPs with a higher aldehyde content resulted in smaller hydrogel pores, higher mechanical strength, and a lower equilibrium swelling rate. These observations provide a theoretical basis for selecting crosslinking candidates for hydrogel-specific applications. [Display omitted] • Dialdehyde polysaccharides (DPs) are novel green crosslinking agents. • Gelatin/DP hydrogels were crosslinked via the Schiff base reaction. • Aldehyde content of DP was regulated by varying the structure of polysaccharide. • Degree of hydrogels crosslinking depended on the aldehyde content of the DPs. • The hydrogels exhibited excellent mechanical, rheological, and swelling properties. [ABSTRACT FROM AUTHOR]

Stereocomplex crystal (SC) in poly(l -lactide) (PLLA)/poly(d -lactide) (PDLA) can significantly improve the heat resistance and mechanical performance of poly(lactic acid). In this work, a selective degradation method is developed to etch the PLLA/PDLA blend using proteinase K, and a two-phase co-continuous structure is observed directly using scanning electron microscope. Meanwhile, the evolution of the microphase morphology, inter-chain interaction, chains orientation, and crystallization of un-crosslinked and crosslinked blends during solid-state stretching, as well as the formation of SC during heating/annealing are comprehensively investigated. Results showed that the phase separation in the stretched blend could be drastically restricted by crosslinking; during stretching a blue-shift of 2995 cm−1 band shows up for both crosslinked and un-crosslinked blends as a result of the dipole-dipole coupling interaction between CH 3 and CH 3 , while the hydrogen bond interaction between CH 3 and C O is absent; only mesophase or homocrystal (HC) is formed in the stretching temperature range of 60∼105 °C; the critical strain for HC formation is advanced and the orientation of chains is enhanced by crosslinking under the same stretching condition. In the last, benefiting from the greatly reduced microphase size (namely enlarged interfacial area between PLLA and PDLA) and enhanced chains orientation, the crystallization rate of SC is accelerated during annealing, and the ultimate crystallinity of SC is elevated in the crosslinked blend. [Display omitted] • A method for direct observation of phase morphology in PLLA/PDLA is proposed by using proteinase K selective degradation. • Crosslinking could restrict the phase separation under both static condition and combined thermal/stretching field. • Crosslinking restricted phase separation and solid-state stretching induced orientation could promote the formation of SC. [ABSTRACT FROM AUTHOR]

In recent years, polymeric hydrogels have been employed to investigate cancer cell-extracellular matrix (ECM) interactions in vitro. In the context of breast cancer, cancer cells are known to degrade the ECM using matrix-metalloproteinases (MMPs) to support invasion resulting in disease progression. Polymeric hydrogels incorporating MMP-cleavable peptides have been employed to study cancer cell invasion, however, the approaches employed to incorporate these peptides often change other hydrogel properties. This underscores the need for decoupling hydrogel properties while incorporating MMP-cleavable peptides. Herein, we report structurally decoupled hyaluronic acid (HA) hydrogels formulated using varying ratios of a biologically sensitive MMP-cleavable peptide and an insensitive counterpart (Dithiothreitol (DTT) or polyethylene glycol dithiol (PEGDT)) to study MMP-mediated metastatic breast cancer cell invasion. Rheological, swelling ratio, estimated mesh size, and permeability measurements showed similar mechanical and physical properties for hydrogels crosslinked with different DTT (or PEGDT)/MMP ratios. However, their degradation rate in the presence of collagenase correlated with the ratio of MMP-cleavable peptide. Encapsulated metastatic breast cancer spheroids in HA hydrogels with MMP sensitivity exhibited increased invasiveness compared to those without MMP sensitivity after 14 days of culture. Overall, such structurally decoupled HA hydrogels provide a platform to study MMP-mediated breast cancer cell invasion in vitro. [ABSTRACT FROM AUTHOR]

Pervaporation offers unique advantages for desalination of hypersaline water using highly hydrophilic and selective membrane. Positively charged membrane is superior in repelling cations and preventing scaling through electrostatic repulsion. This study investigates the quaternization and crosslinking of block copolymer styrene-ethylene-butylene-styrene (SEBS) membrane and explores the potential of quaternized membrane for pervaporation desalination. A one-step immersion process was proposed to easily adjust the physicochemical properties of membrane using trimethylamine (TMA) and N , N , N ′, N ′-tetramethyl-1,6-hexanediamine (TMHDA) for ammonium grafting and crosslinking. Compared to the quaternization with TMA or TMHDA alone, the combination of TMA and TMHDA produces a synergistic effect, improving crosslinking efficiency and facilitating the grafting reaction. This results in high ion exchange capacity (IEC) values and a transformation of microphase separation structure with more interconnected hydrophilic domains. An ultrahigh water permeability coefficient of 0.6 × 106–1.2 × 106 Barrer and highly intrinsic salt rejection were obtained in treating 3.5–20 wt% NaCl solution. The thin film composite QEBS/nylon membranes showed a superior water flux of 116.5 kg·m−2·h−1 and salt rejection of >99.99 % in desalinating 5 wt% NaCl solution at 85 °C. Additionally, the membrane exhibited excellent long-term performance stability and resistance to acid and alkali environment, showing great potential for desalination of hypersaline water. • SEBS membrane was quaternized and crosslinked through a one-step immersion method. • The microscopic structure of membrane was adjusted by quantities of TMA and TMHDA. • The membrane shows outstanding water permeability and salt rejection in pervaporation. • The membrane has excellent performance stability and acid and alkali resistance. [ABSTRACT FROM AUTHOR]

Positively charged nanofiltration membranes offer significant advantages in separating positively charged substances. The key to developing high-performance positively charged nanofiltration membranes lies in the acquisition and modulation of positive charge during membrane preparation. This review provides a review of recent literature on the preparation and application of positively charged nanofiltration membranes. The preparation methods of positively charged nanofiltration membranes were firstly summarized, including interfacial polymerization, phase conversion, self-assembly, co-deposition, chemical cross-linking, filtration deposition, etc. In addition, the main applications of positively charged nanofiltration membranes are presented, such as magnesium‑lithium separation, lithium recovery from the spent lithium-ion batteries, heavy metal removal, nuclear wastewater decontamination, hardness ion removal, dye separation, micropollutant removal and other emerging separation areas. This review focuses on the generation and manipulation strategies of positive charges in different preparation processes. The existing challenges and future directions in this field were also discusses. The review aims to provide guidance and inspiration for the preparation and application of positively charged nanofiltration membranes. [Display omitted] • The preparation methods of positively charged nanofiltration membranes were summarized. • The main applications of positively charged nanofiltration membranes are reviewed. • This review highlights the acquisition and manipulation strategies of positive charges in different preparation processes. • The existing challenges and future directions in this field were also discusses. [ABSTRACT FROM AUTHOR]

Wound dressings play a crucial role in protecting injured tissues and promoting the healing process. Traditional fabrication of antibacterial wound dressings can be complex and may involve toxic components. In this study, we developed an innovative hydrogel film (AP:GE@OTA/Ag) composed of amidated pectin (AP), gelatin (GE), oxidized tannic acid (OTA) at varying concentrations, and in-situ reduced silver nanoparticles (AgNPs). FTIR and XRD analyses confirmed that crosslinking occurs via interactions between OTA quinone groups and free amino groups in AP and GE. TEM imaging demonstrated the well-dispersed AgNPs with an average particle size of 58.64 nm, while the TG measurements indicated the enhancement of the thermal stability compared to AP:GE films. The AP:GE@OTA/Ag films exhibited superior fluid uptake ability (90.96 % at 2 h), water retention capacity (91.69 % at 2 h), and water vapor transmission rate (1903.29 g/m2/day), alongside improved tensile strength (38 MPa). Additionally, these films showed excellent cytocompatibility and sustained potent antimicrobial activity against S. aureus and E. coli with low AgNPs loadings of 1.02 ± 0.13 μg/cm2. NIT-1 mouse insulinoma cells demonstrated robust proliferation when cultured with the prepared dressings. These films significantly accelerated wound repair in a skin excision model, indicating their potential clinical applications for wound healing. [ABSTRACT FROM AUTHOR]

Galactooligosaccharides (GOS), as mimics of human milk oligosaccharides, are important prebiotics for modulating the ecological balance of intestinal microbiota. A novel carrier-free cell immobilization method was established using genipin to cross-link Kluyveromyces lactis CGMCC 2.1494, which produced β-galactosidase, an enzyme essential for GOS synthesis. The resulting immobilized cells were characterized as stable by thermogravimetric analysis and confirmed to be crosslinked through scanning electron microscopy analysis (SEM) and Fourier transform infrared spectroscopy (FTIR). The K m and V max values of β-galactosidase in immobilized cells towards o -nitrophenyl β-D-galactoside were determined to be 3.446 mM and 2210 μmol min−1 g−1, respectively. The enzyme in the immobilized showed higher thermal and organic solvent tolerance compared to that in free cells. The immobilized cells were subsequently employed for GOS synthesis using plant-derived galactose as the substrate. The synthetic reaction conditions were optimized through both single-factor experiments and response surface methodology, resulting in a high yield of 49.1 %. Moreover, the immobilized cells showed good reusability and could be reused for at least 20 batches of GOS synthesis, with the enzyme activity remaining above 70 % at 35 °C. [Display omitted] • Natural genipin was successfully used for non-carrier cell immobilization. • The β-galactosidase of the immobilized cells showed improved biochemical property. • The immobilized cells can synthesize GOS from galactose with high yield. • The immobilized cells exhibited good reusability for GOS synthesis. [ABSTRACT FROM AUTHOR]

The inferior hydrophobicity and mechanical properties of starch-based nanofibrous films significantly restrict their practical application. In view of this, this study prepared octenylsuccinylated starch-pullulan nanofibrous films using electrospinning and glutaraldehyde (GTA) gas-phase crosslinking. After GTA crosslinking, the starch-based nanofibrous films remained white, randomly oriented, smooth, and droplet-free. As the crosslinking time increased from 0 h to 24 h, the mean fibrous diameter augmented from 157.34 nm to 238.66 nm, and the water contact angle rose from 24.30° to 52.49°. Meanwhile, their tensile strength and thermal stability grew, and the mean pore area and elongation at break abated with changes in function groups. The crosslinked starch-based nanofibrous films exhibited an enhanced adsorption capacity for alcohols, ethers, esters, hydrocarbons, and N-compounds of oyster peptides. Correlation analysis shows that the adsorption capacity of the starch-based nanofibrous films was positively correlated with mean fibrous diameter and water contact angle and negatively correlated with mean pore area. These results provide a theoretical basis for the practical application of crosslinked starch-based nanofibrous film materials in deodorization. [Display omitted] • The hydrophobicity of starch-based film improved through glutaraldehyde crosslinking. • The film shows selective adsorption of flavor compounds of oyster peptides. • The film adsorption is related to microstructure, chemical structure, hydrophobicity. [ABSTRACT FROM AUTHOR]

Herein, we report for the first time the incorporation of riboflavin as a bioactive additive in soy protein isolate films, along with investigating the impact of UV light treatment, thereby creating functional packaging material. Our investigation involves a comprehensive characterization of the films, including morphological, physicochemical, and mechanical properties, as well as their effectiveness as light barriers, antimicrobial potential, and biodegradation properties. The UV treatment of riboflavin/soy protein dispersions leads to the formation of films exhibiting minor water swelling and total soluble matter compared to those untreated with UV light, suggesting the development of a cross-linked network. Moreover, increased riboflavin content enhances the cross-linked network's robustness. The mechanical properties of the films exhibit a notable improvement with UV treatment and with increasing riboflavin content until a limit value, showcasing increased tensile strength and Young's modulus. Films showed homogeneous surfaces with an absence of pores and cracks and the ability to act as a barrier for oil passage. Films were assayed as a coating material for chia oil samples exposed to high-intensity UV light, showing great protection capacity. It has been demonstrated that an increase in riboflavin concentration enhances the UV light-blocking properties, making these films promising candidates for storing light-sensitive food products while preserving their nutritional quality. In addition, antibacterial action against S. aureus was determined by disk diffusion assay. Furthermore, the films exhibited relatively short disintegration times under soil burial conditions, even after chemical modification. This research contributes valuable insights to the innovative field of sustainable food packaging materials. [Display omitted] • UV treatment and riboflavin incorporation lead to improved mechanical properties. • Films exhibiting superior water resistance compared to those untreated with UV light. • Increasing riboflavin proportion enhances UV light-blocking properties of the films. • Films exhibited relatively short biodegradation times under soil burial conditions. • The prepared films are promising candidates for storing light-sensitive food products. [ABSTRACT FROM AUTHOR]

Research of the nontraditional polysaccharide gellan gum (GG) is a growing space for the development of novel drug delivery systems due to its tunable physic-mechanical properties, biocompatibility, and stability in a wide range of environments. Unfortunately, high temperature crosslinking is often required, representing a limiting factor for the incorporation of thermosensitive therapeutic agents. Here, we demonstrated that GG can be crosslinked at a low temperature (38 °C) using a simple fabrication process that utilizes trilysine as an alternative to traditional mono- or divalent ion crosslinkers. While elevated temperature mixing is still required to form a clear GG solution, crosslinking of 0.5 – 1 % GG (w/v) in the presence of trilysine (0.03 % - 0.05 % w/v) was achieved at 38 °C resulting in hydrogels with suitable working formulations to facilitate syringe loading. Low injection forces (< 20 N), and biocompatibility was evaluated with normal human dermal fibroblast (cell viability > 90 %). Frequency sweep showed a transition from purely liquid-like behavior to gel-like behavior with increased trilysine concentration. A temperature dependent behavior was lost with higher trilysine concentrations, indicating stable hydrogel formation. NMR results suggest that trilysine participates in gelation via both ionic interactions between the primary amines of trilysine and the carboxylate residues of glucuronic acid and hydrogen bonding. Released studies showed that GG hydrogels can entrap and provide sustained release of IgG in relation to the crosslinker, and antibody concentration used, with a burst release within the first 24 h (∼80 % cumulative released) followed by a sustained released for up to 5 days. Overall, findings demonstrate a promising nontoxic injectable hydrogel that requires lower crosslinking temperatures, is simple to manufacture and serves as a carrier of thermosensitive therapeutic agents. [Display omitted] • Trilysine, a peptide-based molecule, is a viable crosslinker for gellan gum, which crosslinks at 38 °C. • Potential crosslinking mechanism is ionic interaction between trilysine and gellan gum, and hydrogen bonding. • IgG release profile varied in relation to crosslinker concentration and antibody loading concentration. • These nontoxic, injectable gellan gum hydrogels can be used to deliver thermosensitive therapeutic agents. [ABSTRACT FROM AUTHOR]

To investigate the effects of salivary esterases on biostability of collagen treated by galloylated polyphenols. Human dentin was microtomed into 6-μm-thick films, which were demineralized and treated for 60 s using solutions containing 0.6% and 2% of one of the crosslinkers: tannic acid (TAC), epigallocatechin gallate (EGCG), epigallocatechin (EGC), and N-[3-dimethylaminopropyl]-N′-ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS), and for 1 h using EDC/NHS. Half of the treated and untreated (control) films were subjected to human saliva incubation. Collagen biostability was assessed via exogenous protease biodegradation by weight loss and hydroxyproline release, and endogenous MMPs by in situ zymography. The degradation products of galloylated polyphenols (TAC and EGCG) by saliva were monitored using proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). The esterase activity of saliva induced by the crosslinkers was also assessed. Collagen films treated with TAC and EGCG exhibited significantly improved biostability (p < 0.05); however, the enhanced biostability was severely reduced after saliva incubation (p < 0.001). For EDC/NHS treated collagen, saliva incubation showed negligible effect on the biostability. 1H NMR studies confirmed the esterase-catalyzed hydrolysis of the galloyl. GPC measurements showed decreased molecular weight of TAC in saliva indicating its chemical degradation. Both TAC and EGCG showed much higher esterase activity than other treatment groups. The galloyl group plays important role in collagen crosslinking, inducing higher biostability. However, galloylated polyphenols crosslinked on collagen are highly susceptible to metabolism of human saliva by salivary esterase, dramatically compromising the enhanced biostability. [ABSTRACT FROM AUTHOR]

In this work, oxidized sucrose (OS), which is a safe bio-based and non-toxic polyaldehyde, was used as a crosslinker in defibrillated bacterial cellulose (BC) sponges obtained by freeze-drying. For mimicking the proteins' crosslinking, BC was first modified with an aminosilane to partially replace the OH groups on the BC surface with more reactive amino groups. Further, the aminosilane-grafted bacterial cellulose (BCA) was crosslinked with OS in different concentrations and thermally cured. Functionalized bacterial celluloses showed a good thermal stability, comparable to that of unmodified cellulose and much improved mechanical properties. A threefold increase in the compression strength was obtained for the BCA scaffold after crosslinking and curing. This was correlated with the uniform pore structure emphasized by the micro-CT and SEM analyses. The OS-crosslinked BCA scaffolds were not cytotoxic and showed a porosity of around 80 %, which was almost 100 % open porosity. This study shows that the crosslinking of aminated BC scaffolds with OS allows the obtaining of 3D cellulose structures with good mechanical properties and high porosity, suitable for soft tissue engineering. The results recommend this new method as an innovative approach to obtaining biomaterial scaffolds that mimic the natural extracellular matrix. [ABSTRACT FROM AUTHOR]

Gelatin's versatile functionalization offers prospects of facile and effective crosslinking as well as combining with other materials (e.g., metal nanoparticles, carbonaceous, minerals, and polymeric materials exhibiting desired functional properties) to form hybrid materials of improved thermo-mechanical, physio-chemical and biological characteristics. Gelatin-based hydrogels (GHs) and (nano)composite hydrogels possess unique functional features that make them appropriate for a wide range of environmental, technical, and biomedical applications. The properties of GHs could be balanced by optimizing the hydrogel design. The current review explores the various crosslinking techniques of GHs, their properties, composite types, and ultimately their end-use applications. GH's ability to absorb a large volume of water within the gel network via hydrogen bonding is frequently used for water retention (e.g., agricultural additives), and absorbency towards targeted chemicals from the environment (e.g., as wound dressings for absorbing exudates and in water treatment for absorbing pollutants). GH's controllable porosity makes its way to be used to restrict access to chemicals entrapped within the gel phase (e.g., cell encapsulation), regulate the release of encapsulated cargoes within the GH (e.g., drug delivery, agrochemicals release). GH's soft mechanics closely resembling biological tissues, make its use in tissue engineering to deliver suitable mechanical signals to neighboring cells. This review discussed the GHs as potential materials for the creation of biosensors, drug delivery systems, antimicrobials, modified electrodes, water adsorbents, fertilizers and packaging systems, among many others. The future research outlooks are also highlighted. • Described the gelatin chemistry and choice as effective hydrogel matrix • Described the crosslinking techniques to prepare gelatin-based hydrogels • Discussed different strategies of composite hydrogels with improved properties • Overviewed gelatin hydrogels in environmental, biomedical and advanced applications • Summarized research prospects [ABSTRACT FROM AUTHOR]

Substantial evidence has demonstrated the application of fresh and decellularized human corneal lenticules from increasing myopic surgeries. Further preservation of decellularized corneal lenticules would extend its clinical application. However, whether fresh and preserved decellularized lenticules have the same effects in vivo , including refractive correction, remains unclear. Here, we made comprehensive comparisons between fresh human lenticules (FHLs) and preserved decellularized human lenticules (DHLs). Another group of decellularized lenticules was combined with crosslinking for potential keratoconus therapy. Optical transparency, biomechanical properties, and fibrillar ultrastructure were analyzed to evaluate the DHLs and crosslinked DHLs (cDHLs) in vitro. The DHLs retained high transparency and regular ultrastructure, with genetic materials mostly being eliminated. The strength of lenticules in the cDHL group was markedly increased by crosslinking. Moreover, after storage in glycerol for 3 months, the lenticules were reimplanted into rabbit corneal lamellar pockets assisted by a femtosecond laser. The rabbits were followed for another 3 months. There were no obvious rejective complications in any of the three groups. From 1 week to 3 months postoperatively, the host corneas of the FHL group remained highly transparent, while slight hazes were observed in the DHL group. However, the corneas of the cDHL group displayed opacity throughout the 3-month postoperative period. Furthermore, all the lenticules could effectively induce corneal steepening and refractive changes. Taken together, our data indicated that FHLs are ideal inlay products, whereas preserved DHLs could be an alternative for intrastromal lamellar keratoplasty. Our study provides new insights into the clinical application of human lenticule recycling. Currently, substantial evidence has demonstrated the application of fresh and decellularized human corneal lenticules from increasing myopic surgeries. Further preservation of decellularized lenticules would extend its clinical application. However, whether fresh and preserved decellularized lenticules have the same effects in vivo , including refractive correction, remains unclear. Herein, we decellularized human lenticules with or without mechanically strengthened crosslinking. After storage in glycerol for 3 months, the lenticules were reimplanted into rabbit corneas. Comprehensive comparisons were performed among fresh human lenticules (FHLs), decellularized human lenticules (DHLs) and crosslinked DHLs. Our study indicated that FHLs are ideal inlay products, whereas preserved DHLs could be an alternative for intrastromal lamellar keratoplasty. Our study provides new insights into the clinical application of human lenticule recycling. [Display omitted] [ABSTRACT FROM AUTHOR]

Corneal collagen crosslinking (CXL) is a commonly used minimally invasive surgical technique to prevent the progression of corneal ectasias, such as keratoconus. Unfortunately, riboflavin/UV-A light-based CXL procedures have not been successfully applied to all patients, and result in frequent complications, such as corneal haze and endothelial damage. We propose a new method for corneal crosslinking by using a Ruthenium (Ru) based water-soluble photoinitiator and visible light (430 nm). Tris(bipyridine)ruthenium(II) ([R u (bpy) 3 ]2+) and sodium persulfate (SPS) mixture covalently crosslinks free tyrosine, histidine, and lysine groups under visible light (400–450 nm), which prevents UV-A light-induced cytotoxicity in an efficient and time saving collagen crosslinking procedure. In this study, we investigated the effects of the Ru/visible blue light procedure on the viability and toxicity of human corneal epithelium, limbal, and stromal cells. Then bovine corneas crosslinked with ruthenium mixture and visible light were characterized, and their biomechanical properties were compared with the customized riboflavin/UV-A crosslinking approach in the clinics. Crosslinked corneas with a ruthenium-based CXL approach showed significantly higher young's modulus compared to riboflavin/UV-A light-based method applied to corneas. In addition, crosslinked corneas with both methods were characterized to evaluate the hydrodynamic behavior, optical transparency, and enzymatic resistance. In all biomechanical, biochemical, and optical tests used here, corneas that were crosslinked with ruthenium-based approach demonstrated better results than that of corneas crosslinked with riboflavin/ UV-A. This study is promising to be translated into a non-surgical therapy for all ectatic corneal pathologies as a result of mild conditions introduced here with visible light exposure and a nontoxic ruthenium-based photoinitiator to the cornea. Keratoconus, one of the most frequent corneal diseases, could be treated with riboflavin and ultraviolet light-based photo-crosslinking application to the cornea of the patients. Unfortunately, this method has irreversible side effects and cannot be applied to all keratoconus patients. In this study, we exploited the photoactivation behavior of an organoruthenium compound to achieve corneal crosslinking. Ruthenium-based organic complex under visible light demonstrated significantly better biocompatibility and superior biomechanical results than riboflavin and ultraviolet light application. This study promises to translate into a new fast, efficient non-surgical therapy option for all ectatic corneal pathologies. [Display omitted] [ABSTRACT FROM AUTHOR]

Extracellular matrix (ECM) is a dynamic network of proteins, proteoglycans and glycosaminoglycans, providing structure to the tissue and biochemical and biomechanical instructions to the resident cells. In fibrosis, the composition and the organization of the ECM are altered, and these changes influence cellular behaviour. Biochemical (i. e. protein composition) and biomechanical changes in ECM take place simultaneously in vivo. Investigating these changes individually in vitro to examine their (patho)physiological effects has been difficult. In this study, we generated an in vitro model to reflect the altered mechanics of a fibrotic microenvironment through applying fibre crosslinking via ruthenium/sodium persulfate crosslinking on native lung ECM-derived hydrogels. Crosslinking of the hydrogels without changing the biochemical composition of the ECM resulted in increased stiffness and decreased viscoelastic stress relaxation. The altered stress relaxation behaviour was explained using a generalized Maxwell model. Fibre analysis of the hydrogels showed that crosslinked hydrogels had a higher percentage of matrix with a high density and a shorter average fibre length. Fibroblasts seeded on ruthenium-crosslinked lung ECM-derived hydrogels showed myofibroblastic differentiation with a loss of spindle-like morphology together with greater α-smooth muscle actin (α-SMA) expression, increased nuclear area and circularity without any decrease in the viability, compared with the fibroblasts seeded on the native lung-derived ECM hydrogels. In summary, ruthenium crosslinking of native ECM-derived hydrogels provides an exciting opportunity to alter the biomechanical properties of the ECM-derived hydrogels while maintaining the protein composition of the ECM to study the influence of mechanics during fibrotic lung diseases. Fibrotic lung disease is characterized by changes in composition and excessive deposition of extracellular matrix (ECM). ECM fibre structure also changes due to crosslinking, which results in mechanical changes. Separating the changes in composition and mechanical properties has been difficult to date. In this study, we developed an in vitro model that allows alteration of the mechanical changes alone by applying fibre crosslinking in native lung ECM-derived hydrogels. Characterisations of the crosslinked hydrogels indicated the model mimicked mechanical properties of fibrotic lung tissue and reflected altered fibre organisation. This ECM-based fibrosis model provides a method to preserve the native protein composition while altering the mechanical properties providing an important tool, not only for lung but also other organ fibrosis. [Display omitted] [ABSTRACT FROM AUTHOR]

Gelatin (G) cross-linked with oxidized pectin (OP) was studied as a potential scaffold material for tissue engineering. The effect of oxidation on the chemical properties of pectin was investigated by determining the carbonyl and carboxyl amounts. The OP treatment led to a significant decrease of all values (Mn, Mw, [η] and Rh) determined by size exclusion chromatography (SEC) coupled on line with multiangle light scattering and viscometer detectors. Cross-linking parameters were elucidated by FTIR and TNBS assay. In general, the degree of crosslinking increased with the oxidation of pectin. It was found that the presence of the crosslinking agents caused a reduction in swelling and in the gelatin release which was determined by the BCA kit assay. From the hemolysis test, the membrane of red blood cells was not disrupted by the contact of films and the rate of release of hemoglobin was lower than 5%. The coagulation properties were evaluated by the dynamic blood clotting test. The G/OP hydrogels manifested a good activity of wound healing in the albino rats' model. Moreover, the films did not produce any unwilling symptoms. So, it was concluded that studied films have the potentiality to be used as wound healing biomaterials. • The oxidation of pectin is reported. • Crosslinking of oxidized pectin to gelatin is established. • The application of oxidized pectin for Wound healing is discussed. [ABSTRACT FROM AUTHOR]

Jellyfish collagen, a structural protein with limited functionality, can be hydrolyzed to produce jellyfish gelatin, a unique and versatile hydrocolloid. This study is the first to investigate the effects of strategic adjustments to the properties of hydrolyzed, demineralized jellyfish gelatin powder (HDJGP) gels. Understanding how these gels resist or do not resist change from modification is crucial in creating tailored/desirable properties for food applications. The HDJGP gels were modified by crosslinking with pomegranate peel polyphenol powder, and adjusting pH, solids concentration, and maturation temperatures. From these tests, the HDJGP gels produced a wide array of Bloom strengths ranging from 4 to 120 g. Dynamic rheological tests revealed that HDJGP gels with higher Bloom values also had improved resistance to deformation. The improved HDJGP gels showed yield and flow points above 175 and 1400 Pa, respectively, and melting temperatures between 17.8 and 19.5 °C. Additionally, HDJGP gels exhibited Herschel-Bulkley behavior, showing high yield stress and consistency index values. This study demonstrates how jellyfish gelatin can be successfully modified to create gels with a wide array of characteristics, including various strengths as well as mechanical and viscoelastic properties. Overall, in-depth investigations of jellyfish gelatin properties are pivotal to building visibility in the marketplace. Jellyfish gelatin has a great potential in a variety of applications such as foods, biomaterials, cosmetics, medicine, and more. [Display omitted] • The Bloom and rheological properties of jellyfish gelatin was assessed. • Jellyfish gelatin can be modified to produce a wide array of tailored gels. • Crosslinking with pomegranate peel polyphenols increased the gelatin's gel strength. • Hydrolyzed jellyfish collagen behaved as a Herschel-Bulkley fluid. • Jellyfish gelatin's unique properties have potential in a variety of applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • HRP-free silk-HA hybrid hydrogels were fabricated using the Fenton reaction. • Higher HA concentrations increased random coil content and decreased β-sheet content. • Homogeneous hydrogel networks with enhanced optical transparency were achieved. • This strategy provides a basis for HRP-free protein/polymer-based hydrogel scaffolds. • These hydrogels have potential applications in tissue engineering and biosensors. Herein, HRP-free silk-HA hybrid hydrogels are generated using the Fenton reaction. The findings reveal that a higher HA concentration, at an appropriate crosslinking density, increases the random coil content while decreasing the β -sheet content by reducing the interactions of Fe3+ ions with silk fibroin. This facilitates the formation of homogeneous hydrogel networks with enhanced optical transparency. The crosslinking strategies presented here offer a basis for the fabrication of hybrid hydrogel scaffolds based on proteins or polymers having phenolic hydroxyl moieties, without the use of HRP-catalyzed reactions, for a broad range of biomedical applications. [ABSTRACT FROM AUTHOR]