Glyoxal Crosslinking Research Articles

Valorizing recycled paper through chitosan and glyoxal-chitosan treatments: Synergistic effects on mechanical and physical properties

The present study investigates the efficacy of chitosan and glyoxal-crosslinked chitosan (Chi-Gly) as reinforcing agents for enhancing the mechanical, physical, and functional properties of recycled paper. The research aims to evaluate the comparative performance of these two forms of chitosan in imparting strength characteristics and improved functionality to recycled paper substrates. Chitosan and Chi-Gly solutions prepared via glyoxal crosslinking were incorporated into recycled pulp suspensions at varying dosages. Laboratory handsheets were fabricated, and their properties were systematically evaluated through mechanical testing, morphological analysis, wettability measurements, and antibacterial assays. The results demonstrated significant improvements in the tensile index, burst index, and bending resistance for the chitosan and Chi-Gly treated papers, with the Chi-Gly exhibiting superior reinforcement. Notably, the Chi-Gly treated paper exhibited a higher wet tensile index and lower water absorption capacity than the control. SEM analysis revealed a denser, more cohesive fiber network facilitated by chitosan and Chi-Gly, aiding the reinforcement. The treated papers exhibited reduced hydrophobicity and pronounced antibacterial activity against E. coli (a gram-negative bacterium) and S. aureus (a gram-positive bacterium), with the Chi-Gly treatment outperforming chitosan. Notably, the treatments improved the functional properties without negatively impacting optical brightness. The findings highlight the synergistic effects of glyoxal crosslinking on chitosan’s reinforcing ability and the potential of these biopolymers as sustainable and multifunctional additives for the recycled paper industry.

Glyoxal crosslinking of electro-responsive alginate-based hydrogels: Effects on the properties

To improve the features of alginate-based hydrogels in physiological conditions, Ca2+-crosslinked semi-interpenetrated hydrogels formed by poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid and alginate (PEDOT/Alg) were subjected to a treatment with glyoxal to form a dual ionic/covalent network. The covalent network density was systematically varied by considering different glyoxalization times (tG). The content of Ca2+ was significantly higher for the untreated hydrogel than for the glyoxalized ones, while the properties of the hydrogels were found to largely depend on tG. The porosity and swelling capacity decreased with increasing tG, while the stiffness and electrical conductance retention capacity increased with tG. The potentiodynamic response of the hydrogels notably depended on the amount of conformational restraints introduced by the glyoxal, which is a very short crosslinker. Thus, the re-accommodation of the polymer chains during the cyclic potential scans became more difficult with increasing number of covalent crosslinks. This information was used to improve the performance of untreated PEDOT/Alg as electrochemical sensor of hydrogen peroxide by simply applying a tG of 5 min. Overall, the control of the properties of glyoxalized hydrogels through tG is very advantageous and can be used as an on-demand strategy to improve the performance of such materials depending on the application.

Highly Durable Antibacterial Properties of Cellulosic Fabric via β-Cyclodextrin/Essential Oils Inclusion Complex.

Essential oils (EOS), which naturally come from plants, have significant antibacterial properties against a variety of pathogens, but their high volatility and poor water solubility severely restrict their use in the textile industry. In this study, an inclusion complex based on β-cyclodextrin (β-CD)/EOS was prepared by two different simple methods: pad dry cure (method 1) and pad batch (method 2). A glyoxal crosslinking agent was used for the fixation of the inclusion complexes on the surface of the fabric. Lavender, rosemary, salvia, and lemon essential oils were applied. The structure of the β-CD/EOs inclusion complex was investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and weight gain (%), which indicated that the β-CD/EOs were successfully deposited on cellulose-based fabric. The results demonstrated that β-CD enhanced the oils' scent stability, with the advantage of exhibiting no major change in the tensile strength or permeability of cotton. Lavender oil had the highest stability scent with a value of 3.25, even after 30 days of evaluation. The antibacterial activity showed that EOS/βCD-impregnated fabrics for method 1 had an inhibition zone ranging from 33 to 23 mm, while the inhibition zone for method 2 ranged from 39 mm to 29 mm, indicating that our treatment was able to control the growth of bacteria, even after five washing cycles. This study confirmed that the EOs/βCD inclusion-complex-deposited cotton fabric might hold further promise for medical and hospital use.

Novel In Situ-Cross-Linked Electrospun Gelatin/Hydroxyapatite Nonwoven Scaffolds Prove Suitable for Periodontal Tissue Engineering.

Periodontal diseases affect millions of people worldwide and can result in tooth loss. Regenerative treatment options for clinical use are thus needed. We aimed at developing new nonwoven-based scaffolds for periodontal tissue engineering. Nonwovens of 16% gelatin/5% hydroxyapatite were produced by electrospinning and in situ glyoxal cross-linking. In a subset of scaffolds, additional porosity was incorporated via extractable polyethylene glycol fibers. Cell colonization and penetration by human mesenchymal stem cells (hMSCs), periodontal ligament fibroblasts (PDLFs), or cocultures of both were visualized by scanning electron microscopy and 4′,6-diamidin-2-phenylindole (DAPI) staining. Metabolic activity was assessed via Alamar Blue® staining. Cell type and differentiation were analyzed by immunocytochemical staining of Oct4, osteopontin, and periostin. The electrospun nonwovens were efficiently populated by both hMSCs and PDLFs, while scaffolds with additional porosity harbored significantly more cells. The metabolic activity was higher for cocultures of hMSCs and PDLFs, or for PDLF-seeded scaffolds. Periostin and osteopontin expression was more pronounced in cocultures of hMSCs and PDLFs, whereas Oct4 staining was limited to hMSCs. These novel in situ-cross-linked electrospun nonwoven scaffolds allow for efficient adhesion and survival of hMSCs and PDLFs. Coordinated expression of differentiation markers was observed, which rendered this platform an interesting candidate for periodontal tissue engineering.

Effect of glyoxal concentration on the properties of corn starch/poly(vinyl alcohol)/carvacrol nanoemulsion active films

The corn starch (CS) / poly(vinyl alcohol) (PVA) / carvacrol nanoemulsion (CNE) active films were developed via a facile glyoxal cross-linking reaction. The molecular interactions within the film-forming solutions were measured by rheological property. The morphological, structure, and chemical characteristics of the active films were carried out using SEM, FTIR, and XRD. The film’s properties were measured in terms of swelling ratio, gas permeability, mechanical, optical, antioxidant and antimicrobial properties. When the concentration of glyoxal was higher than 3.0 %, the extent of cross-linking between polymeric components increased, which caused the macropolymeric network to become denser. The addition of glyoxal improved the compatibility of CS and PVA blends and induced an enhanced smoothness and rigid fracture in the structure of the films. The water-resistance and mechanical properties of the active films were enhanced with the increase of glyoxal concentration. However, the gas permeability and opacity decreased accordingly. Specially, after cross-linked, the volatilization rate of carvacrol decreased, which was beneficial to the films for enabling long-term antioxidant and antimicrobial activities. This work offers a novel method for preparing CS/PVA-based films with great ductility, strength, and water-resistance for many potential applications, such as packaging engineering and circular development areas.

Comprehensive collagen crosslinking comparison of microfluidic wet-extruded microfibers for bioactive surgical suture development

Collagen microfiber-based constructs have garnered considerable attention for ligament, tendon, and other soft tissue repairs, yet with limited clinical translation due to strength, biocompatibility, scalable manufacturing, and other challenges. Crosslinking collagen fibers improves mechanical properties; however, questions remain regarding optimal crosslinking chemistries, biocompatibility, biodegradation, long-term stability, and potential for biotextile assemble at scale, limiting their clinical usefulness. Here, we assessed over 50 different crosslinking chemistries on microfluidic wet-extruded collagen microfibers made with clinically relevant collagen to optimize collagen fibers as a biotextile yarn for suture or other medical device manufacture. The endogenous collagen crosslinker, glyoxal, provides extraordinary fiber ultimate tensile strength near 300MPa, and Young's modulus of over 3GPa while retaining 50% of the initial load-bearing capacity through 6 months as hydrated. Glyoxal crosslinked collagen fibers further proved cytocompatible and biocompatible per ISO 10993-based testing, and further elicits a predominantly M2 macrophage response. Remarkably these strong collagen fibers are amenable to industrial braiding to form strong collagen fiber sutures. Collagen microfluidic wet extrusion with glyoxal crosslinking thus progress bioengineered, strong, and stable collagen microfibers significantly towards clinical use for potentially promoting efficient healing compared to existing suture materials. Statement of SignificanceTowards improving clinical outcomes for over 1 million ligament and tendon surgeries performed annually, we report an advanced microfluidic extrusion process for type I collagen microfiber manufacturing for biological suture and other biotextile manufacturing. This manuscript reports the most extensive wet-extruded collagen fiber crosslinking compendium published to date, providing a tremendous recourse to the field. Collagen fibers made with clinical-grade collagen and crosslinked with glyoxal, exhibit tensile strength and stability that surpasses all prior reports. This is the first report demonstrating that glyoxal, a native tissue crosslinker, has the extraordinary ability to produce strong, cytocompatible, and biocompatible collagen microfibers. These collagen microfibers are ideal for advanced research and clinical use as surgical suture or other tissue-engineered medical products for sports medicine, orthopedics, and other surgical indications.

Study on Mechanical and Thermal Performance of Building Energy-saving Wall with Insulation Materials

Sodium alginate and natural fiber were used as modifiers to prepare sodium alginate natural fiber type biological composites. The mechanical properties were characterized by universal testing machine, and the thermal properties were analyzed by conductivity, The effects of wood fiber and straw fiber content on the comprehensive properties of biological composite materials were evaluated by relevant instruments, and the feasibility of biological composite materials as building energy-saving wall insulation materials was evaluated. The results show that the flexural strength, compressive strength and elastic modulus of the composites increase with the increase of wood fiber content. When the wood fiber content is 100%, the mechanical properties of the sample are the best, the flexural strength is 0.573 MPa, and the compressive strength is 1.410 MPa. The results showed that wood fiber and sodium alginate binder were closely combined and had good wettability. The thermal conductivity of biological composite is 0.078-0.089w / (m · K), which means it has good thermal insula tion performance and can be used as thermal insulation material for building energy-saving wall. The results show that the properties of the composite can be improved by adding a higher proportion of wood fiber and a certain amount of glyoxal crosslinking agent.

Glyoxal cross-linking of solubilized extracellular matrix to produce highly porous, elastic, and chondro-permissive scaffolds for orthopedic tissue engineering.

Extracellular matrix (ECM)-derived implants hold great promise for tissue repair, but new strategies are required to produce efficiently decellularized scaffolds with the necessary porosity and mechanical properties to facilitate regeneration. In this study, we demonstrate that it is possible to produce highly porous, elastic, articular cartilage (AC) ECM-derived scaffolds that are efficiently decellularized, nonimmunogenic, and chondro-permissive. Pepsin solubilized porcine AC was cross-linked with glyoxal, lyophilized and then subjected to dehydrothermal treatment. The resulting scaffolds were predominantly collagenous in nature, with the majority of sulphated glycosaminoglycan (sGAG) and DNA removed during scaffold fabrication. Four scaffold variants were produced to examine the effect of both ECM (10 or 20 mg/mL) and glyoxal (5 or 10 mM) concentration on the mechanical and biological properties of the resulting construct. When seeded with human infrapatellar fat pad-derived stromal cells, the scaffolds with the lowest concentration of both ECM and glyoxal were found to promote the development of a more hyaline-like cartilage tissue, as evident by increased sGAG and type II collagen deposition. Furthermore, when cultured in the presence of human macrophages, it was found that these ECM-derived scaffolds did not induce the production of key proinflammatory cytokines, which is critical to success of an implantable biomaterial. Together these findings demonstrate that the novel combination of solubilized AC ECM and glyoxal crosslinking can be used to produce highly porous scaffolds that are sufficiently decellularized, highly elastic, chondro-permissive and do not illicit a detrimental immune response when cultured in the presence of human macrophages.

Modulating chain conformations of polyvinyl alcohol through low cost and nontoxic glyoxal crosslinker: Application in high performance organic transistors

Abstract High leakage current and presence of numerous polar hydroxyl groups have often appeared as severe performance obstacles for polyvinyl alcohol (PVA) on its application in organic field effect transistor devices. Herein, we report a facile, yet efficient functionalization and chain structure modification technique to enhance its efficacy as a gate insulating layer. In this work, we have used glyoxal as a cross-linking agent of PVA to modulate its chain conformation and performed a detailed analysis to explore the role of glyoxal crosslinking on the electrical and structural properties of PVA. Applying various amount of glyoxal solution we have properly optimized the dose of the crosslinker to be used in the crosslinking reaction so that minimum amount of leakage can be achieved. Substantial improvement in the insulation properties as well as surface characteristics was observed after the structural modification of the polymer. Correspondingly, organic FETs were fabricated using crosslinked PVA to gauge the effect of crosslinking on the device performance of the transistors. Post-crosslinking improvements in the polymer bulk and surface characteristics were clearly emulated in the device performance parameters. Field-effect mobility as high as 5.4 cm2/V-s and 1.7 cm2/V-s were achieved employing crosslinked PVA as gate dielectric layer in Dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) and pentacene based devices, respectively. Thus, our study illustrates the viability of crosslinking PVA using glyoxal and hence, can catalyze the limited use of PVA in electronic applications.

More sustainable energy storage: lignin based electrodes with glyoxal crosslinking

Crosslinking lignin on high surface area active carbon using glyoxal as a green crosslinker leads to truly sustainable electrodes with improved performance.

Development and characterization of tripolymeric and bipolymeric composite films using glyoxal as a potent crosslinker for biomedical application

For various biomedical applications, biopolymeric films are often crosslinked using chemical crosslinker such as glutaraldehyde, which is considered as a toxic chemical. In this report, we have prepared and characterized biopolymeric films using different combinations of chitosan, CMC, alginate and PVA using glyoxal as the crosslinker. The prepared films were subjected to various physico-chemical and mechanical characterizations such as swelling index, surface pH, surface morphology analysis using SEM, interact ion study using XRD, flexibility study using tensile testing and hardness testing. Glyoxal crosslinking resulted in variation of physico-chemical and mechanical alteration of the chitosan-PVA films while it had the negligible effect on the CAP film. Further, the hardness of the films demonstrated a decrease in value in the crosslinked films as compared to non-crosslinked films. We have interpreted that glyoxal is a potential crosslinker for chitosan-based composite polymers while in this case, it did not show any significant effect on CMC and alginate based composite structures. Therefore, using this type of films would be the cheap, safe and new alternative in drug delivery and other biomedical applications.

Fabrication and characterization of biodegradable composites based on microfibrillated cellulose and polyvinyl alcohol

Microfibrillated cellulose (MFC) based thin membrane-like fully biodegradable composites were produced by blending MFC suspension with polyvinyl alcohol (PVA). Desired MFC content in the composites could be easily obtained by varying the PVA solution concentration. Chemical crosslinking of PVA was carried out using glyoxal to increase the mechanical and thermal properties of the composites as well as to make the PVA partially water-insoluble. Examination of composite surfaces and fracture topographies indicated that the MFC fibrils were well bonded to PVA and uniformly distributed. Infrared spectroscopy showed that acetal linkages could be formed in the MFC–PVA composites by a glyoxal crosslinking reaction. Sol–gel and swelling results indicated that crosslinking reaction made PVA partially insoluble and reduced its swelling ability. The MFC–PVA composites had excellent tensile properties which were further enhanced by crosslinking. Thermogravimetric analysis (TGA) showed higher thermal stability for MFC–PVA composites compared to PVA. The crosslinked MFC–PVA composites showed even higher thermal stability. Differential scanning calorimetry (DSC) indicated that crosslinking increased the glass transition temperature and reduced melting temperature and crystallinity of PVA in MFC–PVA composites. Results also indicated that nano- and micro-fibrils in MFC inhibit the crystallization of PVA. These composites could be good candidates for replacing today’s traditional non-biodegradable plastics.

Effects of glyoxal cross-linking on baked starch foam

Abstract Starch trays and plates were prepared from native corn starch and corn starch cross-linked with glyoxal at different concentrations (0.126, 0.269, 0.271, 0.468 g/kg) using a foam baking process. The effect of cross-linking on baking parameters, including density, colour, water absorption, and tensile and flexural properties, was determined. Also, the morphologies of the trays were examined using a scanning electron microscope. Cross-linking considerably reduced the baking time, density and water absorption of the trays. Trays made from starch cross-linked with 0.126 and 0.269 g/kg glyoxal presented the best properties, with a homogenous microstructure and smooth surface quality. These trays had the lowest density (0.27 g/cm 3 ) and had approximately 53% reduction in water absorption. Moreover, both the tensile and flexural strain of these foams was significantly higher than other foams.

Crosslinking as an Efficient Tool for Decreasing Moisture Sensitivity of Biobased Nanocomposite Films

Chitosan-nanoclay bio-hybrid films were successfully crosslinked with glutaraldehyde, genipin and glyoxal. Moisture sensitivity of films decreased as a result of crosslinking which led to improved barrier properties against water vapor and oxygen. Films containing chitosan (6.6 g/m2) with genipin (3.3 g/m2) and nanoclay (6.6 g/m2) had water vapor transmission rate of 72 g × 100 µm/(m2 × 24 h) which was 34% lower as compared to pure chitosan and 30% lower as compared to chitosan/nanoclay without crosslinkers. Glyoxal induced crosslinking resulted in 92% reduction in oxygen transmission rate at 80% relative humidity as compared to pure chitosan films. Oxygen transmission through glyoxal (3.3 g/m2) treated chitosan/nanoclay film was 2.8 cm3 × 100 µm/(m2 × 24 h) which was 53% lower as compared to chitosan/nanoclay without crosslinkers. In addition, nanoclay and especially glyoxal crosslinking prevented the water vapor sorption of chitosan considerably. Crosslinking may be used as an efficient tool for enhancing the exploitability of naturally hydrophilic biopolymers towards new high-value applications, such as food packaging.

Investigations of the effects of glyoxal cross-linking on the structure and properties of chitosan fiber

The effect of glyoxal cross-linking on the structure and properties of chitosan fiber has been studied using different techniques. Swelling results showed that the cross-linking process can be described by a formula such as: S=79.24−5.05 C+0.24 C 2 ( S, swelling degree; C, glyoxal concentration). WAXD indicated that the cross-linking affects on the chitosan fibers at reducing of its crystallinity, e.g. from 34.7 to 27.2% for this case prepared fiber. Comparing to uncross-linked chitosan fiber, DSC and polarizing microscopy further indicated that the change of the crystal structure for cross-linked chitosan fiber is exactly affecting to the thermal properties. Additionally, SEM photographs showed that the cross-linking seems to play a role to smooth the surface of fiber due to the surface of original chitosan fiber observed roughly.

Glyoxal as a Non-Nitrogenous Formaldehyde-Free Durable-Press Reagent for Cotton'

Glyoxal was found to impart a high degree of wrinkle resistance and smooth drying qualities to all-cotton printcloth. Certain aluminum salts were effective catalysts, the least fabric discoloration being produced with aluminum sulfate. Addition of ethylene glycol or glycerol to the treating solutions eliminated almost all of the discoloration and increased the durable-press appearance ratings. Evidence is presented that the catalytic activity of aluminum sulfate is not explainable on the basis of generation of sulfuric acid by partial hydrolysis of the aluminum salt, and that metal ion catalysis, as well as specific catalysis by hydrogen ions, may take place in the case of glyoxal crosslinking of cellulose. Unlike formaldehyde, glyoxal monomer, dimers, and trimers have structures favorable for chelation by polyvalent metal ions, and such complexes may play a part in the crosslinking reactions. At ordinary concentrations of glyoxal, the durable-press treatments produced very large strength losses in the fabric, but the use of high glyoxal concentrations resulted in large improvements in strength retention.

Preparing and Finishing Durable-Press Cotton Fabrics1

Commercially practicable preparation and finishing techniques have been studied that can be com bined to produce improved durable-press or easy-care woven cotton fabrics, especially lightweights. Fabric mercerization combined with extensive stretching in the filling direction was highly effective in improving tensile and tear strength after subsequent finishing, especially in the filling direction. As an alternative to mercerization, liquid-ammonia treatment on commercial equipment had the addi tional benefits of greater fabric softness, better abrasion resistance, and better fabric appearance after laundering. Finishing with so-called buffered glyoxal crosslinking resins gave a consistently better balance of durable-press rating to strength than the older, less-buffered ones. Application of finish with a low wet pick-up technique resulted in better chemical efficiency and abrasion resistance than a conventional pad application.