Single Cross-linking Research Articles

Dual cross-linking with tannic acid and transglutaminase improves microcapsule stability and encapsulates lemon essential oil for food preservation

The microencapsulation of essential oils by complex coacervation technology has attracted considerable attention. This paper deals with the preparation of gelatin-chitosan microcapsules through dual cross-linking using transglutaminase (TGase) and tannic acid (TA). Lemon essential oil (LEO) was successfully encapsulated with 82.5 % encapsulation efficiency. Compared to single cross-linking microcapsules (TG), dual cross-linking microcapsules (TG-TA) exhibit superior thermal stability and swell stability. In vitro release studies demonstrated that TG-TA exhibited better controlled-release behavior with a longer duration of action. Meanwhile, the lipid oxidation of TG-TA was 1.45 mg MDA/kg that of control group was 2.23 mg MDA/kg which showed their excellent antioxidant effects. Moreover TG-TA have higher antibacterial rate, more inhibition zone diameters and better effect for preventing the growth of total viable count than TG and LEO. This study has theoretical implications for the use of TG-TA ideal carriers for protecting various active substances, thus facilitating their applications in food preservation.

WormCNN-Assisted Establishment and Analysis of Glycation Stress Models in C. elegans: Insights into Disease and Healthy Aging.

Glycation Stress (GS), induced by advanced glycation end-products (AGEs), significantly impacts aging processes. This study introduces a new model of GS of Caenorhabditis elegans by feeding them Escherichia coli OP50 cultured in a glucose-enriched medium, which better simulates human dietary glycation compared to previous single protein-glucose cross-linking methods. Utilizing WormCNN, a deep learning model, we assessed the health status and calculated the Healthy Aging Index (HAI) of worms with or without GS. Our results demonstrated accelerated aging in the GS group, evidenced by increased autofluorescence and altered gene expression of key aging regulators, daf-2 and daf-16. Additionally, we observed elevated pharyngeal pumping rates in AGEs-fed worms, suggesting an addictive response similar to human dietary patterns. This study highlights the profound effects of GS on worm aging and underscores the critical role of computer vision in accurately assessing health status and aiding in the establishment of disease models. The findings provide insights into glycation-induced aging and offer a comprehensive approach to studying the effects of dietary glycation on aging processes.

Hybrid MPA-CdSe quantum dots-based luminescent hydrogel: White light emission regulation and Cu2+ recognition

In this study, a novel CdSe@PEI-PVP luminescent hydrogel was constructed by using MPA-CdSe quantum dots (QDs) as a single emitter and hydrogen bond cross-linking network between highly branched polyethyleneimine (PEI) and polyvinylpyrrolidone (PVP) as a hydrogel skeleton, in which PEI also works as a passivation ligand for MPA-CdSe quantum dots. Utilizing the dual emission of MPA-CdSe quantum dots and adjusting the surface state of MPA-CdSe with PEI and Cd2+, CdSe@PEI-PVP hydrogel can emit bright white light as a whole. Furthermore, CdSe@PEI-PVP shows specific recognition for Cu2+, luminescent color changes from bright white to orange when Cu2+ is added, which enables CdSe@PEI-PVP hydrogel to serve as a fluorescent probe for ion detection. The luminescent hydrogel has great self-healing ability and reversible morphological thermal responsiveness, existing as a white luminescent hydrogel at room temperatures and transforming into a pale green luminescent solution at high temperatures.

Mechanosensitive channel MscL gating transitions coupling with constriction point shift.

The mechanosensitive channel of large conductance (MscL) acts as an "emergency release valve" that protects bacterial cells from acute hypoosmotic stress, and it serves as a paradigm for studying the mechanism underlying the transduction of mechanical forces. MscL gating is proposed to initiate with an expansion without opening, followed by subsequent pore opening via a number of intermediate substates, and ends in a full opening. However, the details of gating process are still largely unknown. Using in vivo viability assay, single channel patch clamp recording, cysteine cross-linking, and tryptophan fluorescence quenching approach, we identified and characterized MscL mutants with different occupancies of constriction region in the pore domain. The results demonstrated the shifts of constriction point along the gating pathway towards cytoplasic side from residue G26, though G22, to L19 upon gating, indicating the closed-expanded transitions coupling of the expansion of tightly packed hydrophobic constriction region to conduct the initial ion permeation in response to the membrane tension. Furthermore, these transitions were regulated by the hydrophobic and lipidic interaction with the constricting "hot spots". Our data reveal a new resolution of the transitions from the closed to the opening substate of MscL, providing insights into the gating mechanisms of MscL.

A strong, hydrostable lignocellulose-based film based on dual cross-linking networks

Green and sustainable biomass materials based on wood processing residues show considerable application potential as substitutes to petroleum-based plastics. However, due to the chemical and structural characteristics of cellulose fibers resulting in their natural hydrophilicity, it is difficult for a single cross-linking network to impart multiple excellent properties to bio-based materials. Here, with wood lignification enhancement inspiration, a high-performance bio-based plastics based on 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized lignocellulose (TOLC) is successfully fabricated by a dual-crosslinking strategy of sodium lignosulfonate (LS) and epichlorohydrin (ECH) modification, and their characterizations were done in terms of SEM, FTIR, XPS, XRD, TG, contact angle and tensile properties. The physical sacrificial bonding between TOLC and LS, in conjunction with the covalent cross-linking network among the TOLC-LS matrix and ECH, contributed to the exceptional tensile strength (383.43 ± 1.57 MPa) and elastic modulus (15.20 ± 0.66 GPa) of the prepared TOLC-LS/ECH film. Furthermore, the maximum weight loss peak of TOLC-LS/ECH III film is observed at 348 °C, higher than TOLC film, which shows exceptional thermal stability. After immersing in water for 24 h, the water absorption rate of TOLC-LS/ECH III film is only 59.72 % of TOLC film, exhibiting increased water resistance. Remarkably, the resulted bio-mass plastics show superior biodegradability with a weight loss of 33.67 % after 30 days in outdoor conditions, while the tensile strength remained 81 % of the original after 6 months in appropriate indoor environments, showing excellent mechanical stability. Compared with most sustainable bio-based plastics, the obtained film shows combination of low production cost, high mechanical properties, and glorious thermal stability, which can effectively expand its application potential in mulch, daily packaging, and so on. This strategy will pave the way for developing sustainable bio-based plastics with low cost, high-performance, and outstanding processing.

A high wet strength and toughness soy-based adhesive prepared by single cross-linking

Soy-based adhesives are considered to be a substitute for toxic petroleum-based adhesives in wood industry because of its environmentally-friendly property. However, their application range is limited by the lack of high wet bond strength and high toughness. While it is possible to impart these properties to soy-based adhesives by adding a variety of corresponding modifiers, it is difficult to do so by adding a single modifier. In this work, a multifunctional cross-linking agent dodecanedioic acid diglycidyl ester (DADE) with high reactivity, toughening, and hydrophobic effects was synthesized and incorporated into soy-based adhesive to ameliorate the bonding performance of the adhesives. The reaction process between DADE and protein was confirmed by instrumental analyses. Results revealed that the introduction of 4% DADE increased the wet bond strength of the soy protein adhesive by 140% to 1.57 MPa, whereas the wet bond strength (1.11 MPa) of soybean meal adhesive containing 4% DADE was comparable to that of MUF resin. The micrographs of the fracture surface and the force-distance curves of the shear strength test showed that the toughness of the adhesives was significantly improved by DADE. These improvements were attributed to the long hydrophobic aliphatic chains and highly reactive groups from DADE. This modification method avoided using large amounts of chemical additives. This work may provide an efficient and low-consumption method for producing bio-based adhesives with excellent bonding properties.

Nanocomposite Hydrogels in Regenerative Medicine: Applications and Challenges.

Regenerative medicine is a highly regarded multidisciplinary field that aims to transform the future of clinical medicine through curative strategies rather than palliative therapies. As an emerging field, the development of regenerative medicine cannot be achieved without multifunctional biomaterials. Among the various bioscaffold materials, hydrogels are one of the materials of interest in bioengineering and medical research because of their similarity to the natural extracellular matrix and good biocompatibility. However, conventional hydrogels have simple internal structures and single cross-linking modes, which require improvement in a single function and structural stability. Introducing multifunctional nanomaterials into 3D hydrogel networks physically or chemically avoids their disadvantages. Nanomaterials (NMs) are materials in the size range of 1-100nm with distinct physical and chemical properties that differ from that of the macroscopic size and enable hydrogels to exhibit multifunctionality. Although regenerative medicine and hydrogels have been well researched in their respective fields, the connection between nanocomposite hydrogels (NCHs) and regenerative medicine has not been elaborated. Therefore, this review briefly describes the preparation and design requirements of NCHs and discusses their applications and challenges in regenerative medicine, hoping to clarify the relationship between the two.

Breaking down the HAUS: Molecular insights into branching microtubule nucleation.

Accurate segregation of chromosomes during mitosis depends on the correct assembly of the mitotic spindle, a bipolar structure composed mainly of microtubules. The augmin complex, or homologous to augmin subunits (HAUS) complex, is an eight-subunit protein complex required for building robust mitotic spindles in metazoa. Augmin increases microtubule density within the spindle by recruiting the γ-tubulin ring complex (γ-TuRC) to pre-existing microtubules and nucleating branching microtubules in a manner that maintains spindle polarity. Here, we elucidate the molecular architecture of augmin by single particle cryo-electron microscopy (cryo-EM), computational methods, and crosslinking mass spectrometry (CLMS). Augmin's highly flexible structure contains a V-shaped head and a filamentous tail, with the head existing in either extended or contracted conformational states. Our work highlights how cryo-EM, complemented by computational advances and CLMS, can elucidate the structure of a challenging protein complex. We demonstrate how this approach has provided novel insights into the function of augmin in mediating microtubule branching nucleation.

A double crosslinking MXene/cellulose nanofiber layered film for improving mechanical properties and stable electromagnetic interference shielding performance

With the discovery of the two-dimensional (2D) MXene, it shows a great application potential in the field of electromagnetic interference (EMI) shielding, but the mechanical brittleness and easy oxidation of MXene limit its wide application. For this reason, a double crosslinking strategy is provided to solve the above problems in a nacre-like “brick-mortar” layered MXene/cellulose nanofiber (MXene/CNF) film. Typically, the film was firstly suffered by dopamine modification, then was further reinforced by secondary Ca2+ bridging, so as to obtain excellent mechanical properties and antioxidative EMI shielding performance. Comparing with the single crosslinking, the double crosslinking strategy reveals a higher efficiency in improving the mechanical property. The mechanical strength and toughness of the double crosslinking MXene/CNF film can increase to 142.2 MPa and 9.48 MJ/m3, respectively. More importantly, while achieving good mechanical properties, the MXene composite film still holds a very stable EMI shielding performance of more than 44.6 dB when suffering from the oxidation treatment of high-temperature annealing, showing excellent anti-oxidation ability and environment tolerance. Therefore, this work provides a universal but effective double crosslinking strategy to solve the mechanical brittleness and easy oxidation of MXene-based composites, thus showing a huge potential in flexible EMI shielding applications.

FORMULATION AND EVALUATION OF POLYMERIC MICROSPHERES USING BOX–BEHNKEN DESIGN

Objectives: The purpose of this research work was to formulate and systemically evaluate in vitro performances of polymeric microspheres of nifedipine. Methods: Nifedipine microspheres containing two polymers, poloxamer 407 and carbopol 934, were prepared by single emulsion cross-linking technique. Glutaraldehyde was selected as the cross-linking agent. A Box–Behnken design was employed to study the effect of independent variables, polymer concentration (X1), stirring speed (X2), and glutaraldehyde concentration (X3) on the dependent variables particle size, drug entrapment efficiency, and flow properties of microspheres. Results: Results of preliminary trials indicate that the polymer concentration, glutaraldehyde concentration, and stirring speed affected various characteristics of microspheres. The formulated Microspheres were discrete, spherical, and free flowing. The optimized batch exhibited with the narrow particle size of 75 μm, good flow properties, and drug entrapment efficiency of 96%. Conclusion: The polymeric microspheres of nifedipine with excellent flowability and good entrapment efficiency were successfully developed. These can be useful in improving patient compliance and bioavailability of nifedipine.

Molecular architecture of the augmin complex

Accurate segregation of chromosomes during mitosis depends on the correct assembly of the mitotic spindle, a bipolar structure composed mainly of microtubules. The augmin complex, or homologous to augmin subunits (HAUS) complex, is an eight-subunit protein complex required for building robust mitotic spindles in metazoa. Augmin increases microtubule density within the spindle by recruiting the γ-tubulin ring complex (γ-TuRC) to pre-existing microtubules and nucleating branching microtubules. Here, we elucidate the molecular architecture of augmin by single particle cryo-electron microscopy (cryo-EM), computational methods, and crosslinking mass spectrometry (CLMS). Augmin’s highly flexible structure contains a V-shaped head and a filamentous tail, with the head existing in either extended or contracted conformational states. Our work highlights how cryo-EM, complemented by computational advances and CLMS, can elucidate the structure of a challenging protein complex and provides insights into the function of augmin in mediating microtubule branching nucleation.

Enzymatic modification of Fish Gelatin and Beet Pectin using Horseradish peroxidase

The Fish Gelatin (FG), a good alternative for unhealthy and limited socio-cultural mammalian gelatin appears to possess endogenous structural limitations. The goal of this work was to use enzymatic crosslinking to modify cold-water Fish Gelatin (FG) with Beet Pectin. Reaction conditions were optimized by a single factorial experiment and covalent crosslinking was measured by ultraviolet (UV)-Vis spectroscopy at 340 nm to indicate Horseradish Peroxidase (HRP) catalyzes Beet Pectin (BP). At 50 °C for 4 h, the highest weight ratio of heterologous adducts between FG-BP was 1:3, with HRP and Hydrogen peroxide (H2O2) of 2 µg/mL and 0.067%, (v/v), respectively. Intermolecular cross-linking was found between treated samples using ATR-FTIR and Sodium Dodecyl Sulphur and Polyacrylamide Gel Electrophoresis (SDS-PAGE). The heterologous product, control FG, and BP as well as a mixture of untreated FG-BP had a β-sheet of 41.14%, 39.65%, 39.9%, and 40.0%, respectively. The maximum reduction in elution was obtained in heterogeneous FG-BP complex. Furthermore, a schematic mechanism for Cold-water Fish Gelatin and Beet Pectin was proposed. Overall, peroxidase crosslinked BP was able to modify cold-water Fish Gelatin. The use of Horseradish peroxidase on Fish Gelatin could provide a practical way of building the FG-BP complex as a basis for understanding the FG functionalities comprehensively.

Mechanically strong, thermal-insulated, and ultralow dielectric polyimide aerogels with adjustable crosslinking methods

Polyimide (PI) aerogels can exhibit controllable physical and chemical properties by changing the type of dianhydride and diamine monomers. However, few works aim to reveal the effects of monomer hybridization and crosslinking methods on the properties of polyimide aerogels. In this work, we studied the effects of single and double crosslinking methods on the density, microstructure and properties of PI aerogels. The results showed that different crosslinking methods could cause completely opposite variation trends of shrinkage and density. The single crosslinking PI aerogels possess large shrinkage of 23.8% and high thermal conductivity of 59.9 mW/(m·K). However, with the same formula, the PI aerogels prepared by the double crosslinking method possess smaller shrinkage of 12.3% and lower thermal conductivity of 28.7 mW/(m·K). The dielectric constant of the double crosslinking PI aerogels shows a lower dielectric constant of 1.10 compared to the single crosslinking PI aerogel of 1.34 when containing the same content of 6FDA. The addition of 6FDA can also increase the 5% thermal decomposition temperature of PI aerogels from 445.5 °C to 460 °C. The as-prepared double-crosslinking PI aerogels present superior properties of lightweight, low dielectric constant and dielectric loss, low thermal conductivity and high temperature resistance, which provides a new way for adjusting the performance of PI aerogels. • PI aerogels prepared by the double crosslinking method possess low shrinkage (12.3%) and thermal conductivity (28.7mW/(m·K)). • The dielectric constant of double crosslinking PI aerogels shows low dielectric constant of 1.10. • The addition of 6FDA can also increase the 5% thermal decomposition temperature of PI aerogels from 445.5 °C to 460 °C.

Bagasse Cellulose Composite Superabsorbent Material with Double-Crosslinking Network Using Chemical Modified Nano-CaCO3 Reinforcing Strategy.

To improve the salt resistance of superabsorbent materials and the gel strength of superabsorbent materials after water absorption, a bagasse cellulose-based network structure composite superabsorbent (CAAMC) was prepared via graft copolymerization of acrylamide/acrylic acid (AM/AA) onto bagasse cellulose using silane coupling agent modified nano-CaCO3 (MNC) and N,N′-methylene bisacrylamide (MBA) as a double crosslinker. The acrylamide/acrylic acid was chemically crosslinked with modified nano-CaCO3 by C-N, and a stable double crosslinked (DC) network CAAMC was formed under the joint crosslinking of N,N′-methylene bisacrylamide and modified nano-CaCO3. Modified nano-CaCO3 plays a dual role of crosslinking agent and the filler, and the gel strength of composite superabsorbent is two times higher than that of N,N′-methylene bisacrylamide single crosslinking. The maximum absorbency of CAAMC reached 712 g/g for deionized water and 72 g/g for 0.9 wt% NaCl solution. The adsorption process of CAAMC was simulated by materials studio, and the maximum adsorption energy of amino and carboxyl groups for water molecules is −2.413 kJ/mol and −2.240 kJ/mol, respectively. According to the results of CAAMC soil water retention, a small amount of CAAMC can greatly improve the soil water retention effect.

Reinforcing DNA Supramolecular Hydrogel with Polymeric Multiple-Unit Linker

Reinforcing DNA Supramolecular Hydrogel with Polymeric Multiple-Unit Linker

Characteristics of Biodegradable Gelatin Methacrylate Hydrogel Designed to Improve Osteoinduction and Effect of Additional Binding of Tannic Acid on Hydrogel.

In this study, a hydrogel using single and double crosslinking was prepared using GelMA, a natural polymer, and the effect was evaluated when the double crosslinked hydrogel and tannic acid were treated. The resulting hydrogel was subjected to physicochemical property evaluation, biocompatibility evaluation, and animal testing. The free radicals generated through APS/TEMED have a scaffold form with a porous structure in the hydrogel, and have a more stable structure through photo crosslinking. The double crosslinked hydrogel had improved mechanical strength and better results in cell compatibility tests than the single crosslinked group. Moreover, in the hydrogel transplanted into the femur of a rat, the double crosslinked group showed an osteoinductive response due to the attachment of bone minerals after 4 and 8 weeks, but the single crosslinked group did not show an osteoinductive response due to rapid degradation. Treatment with a high concentration of tannic acid showed significantly improved mechanical strength through H-bonding. However, cell adhesion and proliferation were limited compared to the untreated group due to the limitation of water absorption capacity, and no osteoinduction reaction was observed. As a result, it was confirmed that the treatment of high-concentration tannic acid significantly improved mechanical strength, but it was not a suitable method for improving bone induction due to the limitation of water absorption.

Physicochemical Characterization of Pectin-Gelatin Biomaterial Formulations for 3D Bioprinting.

Developing biomaterial formulations with specific biochemical characteristics and physical properties suitable for bioprinting of 3D scaffolds is a pivotal challenge in tissue engineering. Therefore, the design of novel bioprintable formulations is a continuously evolving research field. In this work, the authors aim at expanding the library of biomaterial inks by blending two natural biopolymers: pectin and gelatin. Cytocompatible formulations are obtained by combining pectin and gelatin at different ratios and using (3-glycidyloxypropyl)trimethoxysilane (GPTMS) as single crosslinking agent. It is shown that the developed formulations are all suitable for extrusion-based 3D bioprinting. Self-supporting scaffolds with a designed macroporosity and micropores in the bioprinted struts are successfully obtained by combining extrusion-based bioprinting and freeze-drying. The presence of gelatin in these formulations allows for the modulation of porosity, of water uptake and of scaffold stiffness in respect to pure pectin scaffolds. Results demonstrate that these new biomaterial formulations, processed with this specific approach, are promising candidates for the fabrication of tissue-like scaffolds for tissue regeneration.

Constructing Co-N-C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells.

Exploiting platinum-group-metal (PGM)-free electrocatalysts with remarkable activity and stability toward oxygen reduction reaction (ORR) is of significant importance to the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs). Here, a high-performance and anti-Fenton reaction cobalt-nitrogen-carbon (Co-N-C) catalyst is reported via employing double crosslinking (DC) hydrogel strategy, which consists of the chemical crosslinking between acrylic acid (AA) and acrylamide (AM) copolymerization and metal coordinated crosslinking between Co2+ and P(AA-AM) copolymer. The resultant DC hydrogel can benefit the Co2+ dispersion via chelated Co-N/O bonds and relieve metal agglomeration during the subsequent pyrolysis, resulting in the atomically dispersed Co-Nx/C active sites. By optimizing the ratio of AA/AM, the optimal P(AA-AM)(5-1)-Co-N catalyst exhibits a high content of nitrogen doping (12.36 at%) and specific surface area (1397 m2 g-1 ), significantly larger than that of the PAA-Co-N catalyst (10.59 at%/746 m2 g-1 ) derived from single crosslinking (SC) hydrogel. The electrochemical measurements reveal that P(AA-AM)(5-1)-Co-N possesses enhanced ORR activity (half-wave potential (E1/2 ) ≈0.820 V versus the reversible hydrogen electrode (RHE)) and stability (≈4 mV shift in E1/2 after 5000 potential cycles in 0.5 m H2 SO4 at 60 ºC) relative to PAA-Co-N, which is higher than most Co-N-C catalysts reported so far.

Chitosan-anthracene hydrogels as controlled stiffening networks

In this study, we report the synthesis of single and dual-crosslinked anthracene-functional chitosan-based hydrogels in the absence of toxic initiators. Single crosslinking was achieved through dimerization of anthracene, whereas dual-crosslinked hydrogel was formed through dimerization of anthracene and free radical photopolymerization of methacrylated-chitosan in the presence of non-toxic initiator riboflavin, a well-known vitamin B2. Both single and dual-crosslinked hydrogels were found to be elastic, as was determined through rheological analysis. We observed that the dual-crosslinked hydrogels exhibited higher Young's modulus than the single-crosslinked hydrogels, where the modulus for single and dual-crosslinked hydrogels were measured as 9.2 ± 1.0 kPa and 26 ± 2.8 kPa, respectively resulting in significantly high volume of cells in dual-crosslinked hydrogel (2.2 × 107 μm3) compared to single-crosslinked (4.9 × 106 μm3). Furthermore, we investigated the cytotoxicity of both hydrogels towards 3T3-J2 fibroblast cells through CellTiter-Glo assay. Finally, immunofluorescence staining was carried out to evaluate the impact of hydrogel modulus on cell morphology. This study comprehensively presents functionalization of chitosan with anthracene, uses nontoxic initiator riboflavin, modulates the degree of crosslinking through dimerization of anthracene and free radical photopolymerization, and further modulates cell behavior through the alterations of hydrogel properties.

Simultaneous Cross-Linking and Cross-Polymerization of Enzyme Responsive Polyethylene Glycol Nanogels in Confined Aqueous Droplets for Reduction of Low-Density Lipoprotein Oxidation.

A key initiating step in atherosclerosis is the accumulation and retention of apolipoprotein B complexing lipoproteins within the artery walls. In this work, we address this exact initiating mechanism of atherosclerosis, which results from the oxidation of low-density lipoproteins (oxLDL) using therapeutic nanogels. We present the development of biocompatible polyethylene glycol (PEG) cross-linked nanogels formed from a single simultaneous cross-linking and co-polymerization step in water without the requirement for an organic solvent, high temperature, or shear stress. The nanogel synthesis also incorporates in situ noncovalent electrostatically driven template polymerization around an innate anti-inflammatory and anti-oxidizing paraoxonase-1 (PON-1) enzyme payload-the release of which is triggered because of matrix metalloproteinase responsive elements instilled in the PEG cross-linker monomer. The results obtained demonstrate the potential of triggered release of the PON-1 enzyme and its efficacy against the production of ox-LDL, and therefore a reduction in macrophage foam cell and reactive oxygen species formation.