Structure-property of crosslinked chitosan/silica composite films modified by genipin and glutaraldehyde under alkaline conditions

Enhancing the porosity of chitosan sponges with CBD by adding antimicrobial violacein

Given the growing interest in non-toxic materials with good anti-inflammatory and antimicrobial mechanical properties, this work focuses on preparing chitosan sponges with violacein and cannabis oil crosslinked with dialdehyde chitosan. The sponge was tested for its physicochemical and biological properties, presenting a high swelling rate, good thermal stability, and satisfactory mechanical properties. The obtained sponge's water vapor transmission rate was 2101 g/m2/day and is within the recommended values for ideal wound dressings. Notably, adding violacein favorably affected the material's porosity, which is essential for dressing materials. In addition, studies have shown that the designed material interacts with human serum albumin and exhibits good antioxidant and anti-inflammatory properties. The antibacterial properties of the prepared biomaterial were assessed using the Microtox test against A. fisherii (Gram-negative bacterium) and S. aureus (Gram-positive bacterium). The investigated material provides potential therapeutic benefits due to the synergistic action of chitosan, violacein, and cannabis oil so that it could be used as a dressing material. The natural origin of the substances could provide an attractive and sustainable alternative to traditional commercially available dressings.

Natural polysaccharides and proteins-based films for potential food packaging and mulch applications: A review

Conventional nondegradable packaging and mulch films, after reaching the end of their use, become a major source of waste and are primarily disposed of in landfills. Accumulation of non-degradable film residues in the soil leads to diminished soil fertility, reduced crop yield, and can potentially affect humans. Application of degradable films is still limited due to the high cost, poor mechanical, and gas barrier properties of current biobased synthetic polymers. In this respect, natural polysaccharides and proteins can offer potential solutions. Having versatile functional groups, three-dimensional network structures, biodegradability, ease of processing, and the potential for surface modifications make polysaccharides and proteins excellent candidates for quality films. Besides, their low-cost availability as industrial waste/byproducts makes them cost-effective alternatives. This review paper covers the performance properties, cost assessment, and in-depth analysis of macromolecular structures of some natural polysaccharides and proteins-based films that have great potential for packaging and mulch applications. Proper dissolution of biopolymers to improve molecular interactions and entanglement, and establishment of crosslinkages to form an ordered and cohesive polymeric structure can help to obtain films with good properties. Simple aqueous-based film formulation techniques and utilization of waste/byproducts can stimulate the adoption of affordable biobased films on a large-scale.

Fabrication of jamun seed starch/tamarind kernel xyloglucan bio-nanocomposite films incorporated with chitosan nanoparticles and their application on sapota (Manilkara zapota) fruits

The present work develops bio-nanocomposite packaging films by valorizing agricultural byproducts jamun seed starch (JaSS) and tamarind kernel xyloglucan (XG), and adding varying concentrations of chitosan nanoparticles (ChNPs). The blending of JaSS and XG promotes a dense polymer network in the composite films with enhanced packaging attributes. However, ChNPs incorporation significantly reduced the viscosity and dynamic moduli of the JaSS/XG film-forming solutions. The FTIR and XRD results reveal improved intermolecular interactions and crystallinity. The DSC and TGA thermograms showed improved thermal stability in the ChNP-loaded JaSS/XG films. The addition of 3 % w/w ChNPs significantly enhanced the tensile strength (20.42 MPa), elastic modulus (0.8 GPa), and contact angle (89°), along with reduced water vapor transmission rate (13.26 g/h.m2) of the JaSS/XG films. The films exhibited strong antimicrobial activity against Bacillus cereus and Escherichia coli. More interestingly, the JaSS/XG/ChNPs coating on the sapota fruits retarded the weight loss and color change up to 12 days of storage. Overall, the JaSS/XG/ChNP bio-nanocomposites are promising packaging materials.

Antibiofilm Activity of Eugenol-Loaded Chitosan Coatings against Common Medical-Device-Contaminating Bacteria

The formation of pathogenic biofilms on medical devices is a major public health concern accounting for over 65% of healthcare-associated infections and causing high infection morbidity, mortality, and a great burden to patients and the healthcare system due to its resistance to treatment. In this study, we developed a chitosan-based antimicrobial coating with embedded mesoporous silica nanoparticles (MSNs) to load and deliver eugenol, an essential oil component, to inhibit the biofilm formation of common bacteria in medical-device-related infections. The eugenol-loaded MSNs were dispersed in a chitosan solution, which was then cross-linked with glutaraldehyde and drop-casted to obtain coatings. The MSNs and coatings were characterized by dynamic light scattering, Brunauer-Emmett-Teller analysis, attenuated-total-reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, 3D optical profilometry, and scanning electron microscopy. The release behavior of eugenol-loaded MSNs and coatings and the antibiofilm and antimicrobial activity of the coatings against adherent Staphylococcus aureus, methicillin-resistant S. aureus, and Pseudomonas aeruginosa were investigated. Eugenol was released from the MSNs and coatings in aqueous conditions in a controlled manner with an initial low release, followed by a peak release, a decrease, and a plateau. While the chitosan coatings alone or with unloaded MSNs demonstrated limited antimicrobial effects and still supported biofilm formation after 24 h, the coating containing eugenol not only reduced biofilm formation but also killed the majority of the attached bacteria. It also showed biocompatibility in indirect contact with NIH/3T3 fibroblasts and a high percentage of live cells in direct contact. However, further investigations into cell proliferation in direct contact are recommended. The findings indicated that the chitosan-based coating with eugenol-loaded MSNs could be developed into an effective strategy to inhibit biofilm formation on medical devices.

Photochemical stability of chitosan films doped with cannabis oil

The effect of UV radiation from three different sources on chitosan (CS) films containing the addition of 10% by weight of cannabis oil was investigated. Cannabis oil (CBD) alone exposed to UV is unstable, but its photostability significantly increases in the chitosan matrix. The course of photochemical reactions, studied by FTIR spectroscopy, is slow and inefficient in chitosan with CBD, even under high-energy UV sources. The research also included chitosan films with CBD cross-linked with dialdehyde starch (DAS). Using AFM microscopy and contact angle measurements, the morphology and surface properties of prepared chitosan films with CBD were investigated, respectively. It was found that CBD embedded in CS is characterized by the best photostability under the influence of an LED emitting long-wave radiation. Using a monochromatic and polychromatic UV lamp (HPK and UV-C) emitting high-energy radiation, gradual degradation accompanied by oxidation was observed, both in the CS chains and in the CBD additive. Additionally, changes in surface properties are observed during UV irradiation. It was concluded that CS protects CBD against photodegradation, and a further improvement in photochemical stability is achieved after system cross-linking with DAS.

The cross-linking ability of dialdo-galactose in food processing condition

Cross-linking is a popular strategy to tailor the mechanical profile of foods and materials. Dialdo-galactose (DAG) is a hetero-sugar bearing two aldehyde groups that could potentially cross-link amino-group rich systems. In this study, we proved even in undesirable Maillard reaction condition, DAG is a very reactive Maillard substrate that could effectively cross-link all the tested foods, enhance their mechanical strength, and generate brown pigments during cross-linking. In particular, DAG treated sea cucumber exhibited good stability against heat-induced deterioration. In addition, DAG treated collagen sausage casing was more elastic and flexible then glutaraldehyde (GA) treated ones. DAG also outperformed GA in generating stronger chitosan hydrogels with higher G', and the DAG cross-linked chitosan film was more robust against acid-catalyzed decompositions. These results have not only confirmed DAG's cross-linking ability in food processing condition, but also provided useful information for the development of new food cross-linking agents based on oxidized saccharides.

Reactive oxygen species-responsive hydrophobic crosslinked chitosan films based on triple-function crosslinkers

Chitosan is widely used in reactive oxygen species (ROS)-responsive films but remains great challenges owing to its weak mechanical strength and strong hydrophilicity. Herein, we synthesized novel hydrophobic crosslinked CS films with ROS-responsive properties and excellent physicochemical properties. A novel crosslinker, 2-((10-carboxydecyl)thio)succinic acid, with long-chain alkanes, three carboxyl groups, and sulfhydryl groups was synthesized and then used to produce thioether-containing crosslinked CS membranes. The results suggested that crosslinking could significantly increase the tensile strength of the film from 15.67 MPa to 24.32 MPa. The compact structure of crosslinked chitosan film improved the hydrophobicity and degradability, reduced the thermal stability and swelling rates, exhibited excellent non- cytotoxicity. The in vitro release studies revealed that crosslinked chitosan films could displayed the highest flux about 1.40 mg/ (cm2 h) and significant NR fluorescence change over 80 %. Collectively, our results demonstrate the applicability of these films as ROS-responsive drug delivery systems.

The Relationship Between the Cross-Linker on Chitosan-Coated Magnetic Nanoparticles and the Properties of Immobilized Papain

The immobilized enzymes' properties can be affected by cross-linkers on the surface of supports. To study how cross-linkers alter enzymes function, chitosan-coated magnetic nanoparticles (CMNPs) with immobilized papain were prepared using glutaraldehyde and or genipin, and then, the properties of the nanoparticles and the immobilized enzymes were assessed. The Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), and X-Ray Diffraction (XRD) results showed that the CMNPs were prepared and papain molecules were immobilized on CMNPs by glutaraldehyde (CMNP-Glu-Papain) or by genipin (CMNP-Gen-Papain). Also, the results associated with enzymes activity indicated that the immobilization by glutaraldehyde and genipin increased the pH optimum of papain from 7 to 7.5 and 9, respectively. The kinetic results indicated that the immobilization by genipin slightly affects the enzyme affinity to the substrate. The stability results showed that CMNP-Gen-Papain has more thermal stability than CMNP-Glu-Papain and papain immobilization on CMNPs by genipin leads to stabilization of the enzyme in the presence of polar solvents, probably due to the more hydroxyl groups on CMNPs activated by genipin. In conclusion, this study suggests that there is a relationship between the types of cross-linker on the surface of supports, and the mechanism of action, kinetic parameters, and the stability of immobilized papain.

Adsorption of methyl orange by porous membranes prepared from deep eutectic supramolecular polymer-modified chitosan

The fabrication of an adsorbent with excellent performance has been a focus of attention because of the toxicity, mutagenicity and carcinogenicity of methyl orange (MO)-containing wastewater discharged from the textile, tannery and pharmaceutical industries. In this study, chitosan (CS) membranes were modified with a deep eutectic supramolecular polymer (DESP), and adsorbent membranes with porous structures were prepared with polyethylene glycol (PEG). Microstructural characterization of the CS-DESP-PEG composite membranes with FT-IR, XRD and SEM showed that the membranes had amorphous crystalline structures and that hydrogen bonding interactions weakened the crystallinity and formed loose porous structures. Optimization of the chitosan to β-cyclodextrin ratio, pH, PEG proportion, MO concentration and adsorbent dose significantly improved the adsorption efficiencies of the membranes. The adsorption behaviours of the membranes were fit with pseudo-second-order adsorption kinetics and the Freundlich adsorption isotherm model. Regeneration experiments showed that the membranes were reusable multiple times and maintained good adsorption capacities.

Preparation of chitosan/Enoki mushroom foot polysaccharide composite cling film and its application in blueberry preservation

In this study, the composite cling film was prepared by solution casting method using chitosan and golden mushroom foot polysaccharide as substrates, and the structure and physicochemical indexes of the composite cling film were characterized by Fourier infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The results showed that compared with single chitosan film, the composite cling film has better mechanical properties and antioxidant properties, and the barrier of UV light and water vapor is also stronger. Due to its high nutritional value, blueberry has a short shelf life due to its thin skin and poor storage resistance. Therefore, in this study, blueberry was used as the object of freshness preservation, and the single chitosan film group and the uncovered group were used as controls, and the weight loss, total bacterial colony, decay rate, respiration intensity, malondialdehyde content, hardness, soluble solids, titratable acid, anthocyanin content, and VC content of blueberry were used as freshness preservation indexes for experiments. The comprehensive results showed that the freshness preservation effect of the composite film group was significantly higher than that of the control group, with better antibacterial properties, antioxidant properties, etc., which could effectively delay fruit decay and deterioration, thus prolonging the shelf life, and thus the chitosan/Enoki mushroom foot polysaccharide composite preservation film has a high potential as a new freshness preservation material for blueberry.

Effects of ultrasound treatment on the morphological characteristics, structures and emulsifying properties of genipin cross-linked myofibrillar protein

Genipin is a natural crosslinker that improves the functional properties of proteins by modifying its structures. This study aimed to investigate the effects of sonication on the emulsifying properties of different genipin concentration-induced myofibrillar protein (MP) cross-linking. The structural characteristics, solubility, emulsifying properties, and rheological properties of genipin-induced MP crosslinking without sonication (Native), sonication before crosslinking (UMP), and sonication after crosslinking (MPU) treatments were determined, and the interaction between genipin and MP were estimated by molecular docking. The results demonstrated that hydrogen bond might be the main forces for genipin binding to the MP, and 0.5 μM/mg genipin was a desirable concentration for protein cross-linking to improve MP emulsion stability. Ultrasound treatment before and after crosslinking were better than Native treatment to improve the emulsifying stability index (ESI) of MP. Among the three treatment groups at the 0.5 μM/mg genipin treatment, the MPU treatment group showed the smallest size, most uniform protein particle distribution, and the highest ESI (59.89%). Additionally, the highest α-helix (41.96%) in the MPU + G5 group may be conducive to the formation of a stable and multilayer oil-water interface. Furthermore, the free groups, solubility, and protein exposure extent of the MPU groups were higher than those of UMP and Native groups. Therefore, this work suggests that the treatment of cross-linking followed by ultrasound (MPU) could be a desirable approach for improving the emulsifying stability of MP.

Wet-spinnability and crosslinked Fiber properties of alginate/hydroxyethyl cellulose with varied proportion for potential use in tendon tissue engineering

Researchers have examined different bio-inspired materials in tissue engineering and regenerative medicine to fabricate scaffolds to address tendon regeneration requirements. We developed fibers based on alginate (Alg) and hydroxyethyl cellulose (HEC) by wet-spinning technique to mimic the fibrous sheath of ECM. Various proportions (25:75, 50:50, 75:25) of 1 % Alg and 4 % HEC were blended to this aim. Two steps of crosslinking with different concentrations of CaCl₂ (2.5 and 5 %) and glutaraldehyde (2.5 %) were used to improve physical and mechanical properties. The fibers were characterized by FTIR, SEM, swelling, degradation, and tensile tests. The in vitro proliferation, viability, and migration of tenocytes on the fibers were also evaluated. Moreover, the biocompatibility of implanted fibers was investigated in an animal model. The results showed ionic and covalent molecular interactions between the components. In addition, by properly maintaining surface morphology, fiber alignment, and swelling, lower concentrations of HEC in the blending provided good degradability and mechanical features. The mechanical strength of fibers was in the range of collagenous fibers. Increasing the crosslinking led to significantly different mechanical behaviors in terms of tensile strength and elongation at break. Because of good in vitro and in vivo biocompatibility, tenocyte proliferation, and migration, the biological macromolecular fibers could serve as desirable tendon substitutes. This study provides more practical insight into tendon tissue engineering in translational medicine.

Chitosan/glycyrrhizic acid hydrogel: Preparation, characterization, and its potential for controlled release of gallic acid

In the present work, chitosan (CHT) as a biodegradable polymer was crosslinked using various amounts of glycyrrhizic acid (GLA) as a novel crosslinking agent to prepare biocompatible hydrogels. The prepared hydrogels were used for the controlled release of gallic acid (GA) in transdermal therapy application. FTIR, XRD, and SEM were used to characterize the prepared gels. The results indicated that the carboxylic acid groups of GLA react with the amine groups of the CHT in the presence of activating coupling reagents to form covalent amide linkage between the polymer chains of CHT and construct CHT cross-linked hydrogel (CCH) network structure. The prepared CCH samples were characterized and used for the controlled release of a drug, i.e. (GA). For this purpose, the swelling kinetic, loading and encapsulation efficiency, in vitro drug release, drug release kinetics, cell viability assay, and anti-bacterial activity of the samples were evaluated. The swelling ratio of CCH samples were in the range of 455-37 % depending on the pH of environment. Swelling kinetic results showed an aggregate to the non-linear second-order kinetic model. Drug release results were fitted by kinetic models while the Korsmeyer-Peppas model was fitted better. The CCH samples exhibited high biocompatibility for 5 mg/ml hydrogel concentration. In addition, the CHT and CCH sample without the GA did not show anti-bacterial properties for 1200 and 150 μg/ml concentrations, respectively. The CCH sample containing the GA exhibited enough anti-bacterial activity on the S. aureus bacteria strain at 150 μg/ml concentration. In contrast, the CCH sample containing the GA has a light anti-bacterial effect on the E. coli bacteria strain. The calculated mesh size of hydrogel networks, drug size, and kinetics models revealed that the CCH samples could release GA based on a diffusion mechanism. In conclusion, the designed CCH samples have enough ability for controlled drug release in transdermal applications.

Feasibility study of oxidized naringin as a novel crosslinking agent for crosslinking decellularized porcine Achilles tendon and its potential application for anterior cruciate ligament repair

Naringin (Nar), a natural flavanone glycoside, has been shown to possess a variety of biological activities, including anti-inflammatory, anti-apoptotic, bone formation, and so forth. In this study, Nar was oxidized by sodium periodate and the oxidized naringin (ONar) was used as a novel biological crosslinking agent. In addition, ONar-fixed porcine decellularized Achilles tendon (DAT) was developed to substitute anterior cruciate ligament (ACL) for researching a novel ACL replacement material. The ONar with a 24 h oxidation time had appropriate aldehyde group content, almost no cytotoxicity, and a good crosslinking effect. The critical characteristics and cytocompatibility of ONar-fixed DAT were also investigated. The results demonstrated that 1% ONar-fixed DAT exhibited good resistance to enzymatic degradation and thermal stability as well as suitable mechanical strength. Moreover, 1% ONar-fixed specimens exhibited excellent L929 fibroblasts-cytocompatibility and MC3T3-E1-cytocompatibility. They also promoted the secretion of hepatocyte growth factor (HGF) and basic fibroblast growth factor (bFGF) from fibroblasts and bone morphogenetic protein-2 (BMP-2) from osteoblasts. And they also showed the good anti-inflammatory properties in vivo experiments. Our data provided an experimental basis for ONar as a new cross-linking reagent in chemical modification of DAT and ONar-fixed DAT for ACL repair.

Promotion of the genipin crosslinked chitosan-fiber hydrogel loaded with sustained release of clemastine fumarate in diabetic wound repair

Diabetic skin disorders are lingering and refractory clinical diseases. In this study, a genipin-crosslinked porous chitosan fiber (CSF) hydrogel was fabricated to achieve rapid wound healing. By embedding clemastine fumarate (CF) in the CSF hydrogel pores, we synthesised a CSF/CF hydrogel for the treatment of diabetic wounds. The microstructure, chemical elements, spectral variation, mechanical properties, swelling ratios, degradability, and toxicity of the CSF/CF hydrogels were studied. Compared with the typical CS power hydrogel, the porous CSF hydrogel crosslinked with genipin possesses a stable structure and improved physicochemical properties. Moreover, CF was slowly released from the CSF hydrogel. Molecular simulation also showed that CF was evenly embedded inside the cavity formed by the novel CSF hydrogel. The results suggested that CF can resist damage from high glucose levels and promote proliferation, tube formation, and migration of endothelial cells (ECs) and fibroblasts. The CSF/CF hydrogel promoted wound healing in a rat model. Mechanistically, the beneficial effect of CF on wound healing may be related to activation of the MEK/ERK and PI3K/Akt signalling pathways. In conclusion, genipin-crosslinked CSF/CF hydrogel can accelerate wound healing and may be an effective therapeutic method for treating diabetic skin lesions.

Characterization of four thermogelled egg yolk varieties based on moisture and protein content

There are obvious differences between egg yolks of different varieties. Additionally, boiled eggs, which are widely liked and consumed globally, are nutrient rich. However, they absorb water in the esophagus during swallowing, and this result in an uncomfortable sensation. Here, we determined the moisture content and distribution as well as the protein contents and properties of 4 varieties of thermogelled egg yolks. Among the varieties, Green Shelled thermogelled egg yolk showed the highest protein content and solubility. Additionally, the ionic, hydrogen, and disulfide bonds corresponding to Rhode Island Red thermogelled egg yolk samples were the weakest, while the hydrophobic interaction force corresponding to the Hetian Dahei (HD) egg yolk samples was the weakest. Further, the distribution of the moisture contents of the 4 varieties was significantly different (P < 0.05). HD egg yolk showed the highest moisture content, and its bound and immobile moisture contents were significantly higher than those of the other 3 varieties. Egg yolk moisture content also affected free amino acid content, which was the highest for HD egg yolk. Therefore, owing to its high moisture content, HD egg yolk was conducive for chewing and swallowing and given its high free amino acid content, it also had a more suitable taste and flavor. The results of this study provide a theoretical basis for the application of egg yolks in food processing.

Binary Hydrogels: Induction Methods and Recent Application Progress as Food Matrices for Bioactive Compounds Delivery-A Bibliometric Review

Food hydrogels are biopolymeric materials made from food-grade biopolymers with gelling properties (proteins and polysaccharides) and a 3D network capable of incorporating large amounts of water. They have sparked considerable interest because of their potential and broad application range in the biomedical and pharmaceutical sectors. However, hydrogel research in the field of food science is still limited. This knowledge gap provides numerous opportunities for implementing their unique properties, such as high water-holding capacity, moderated texture, compatibility with other substances, cell biocompatibility, biodegradability, and high resemblance to living tissues, for the development of novel, functional food matrices. For that reason, this article includes a bibliometric analysis characterizing research trends in food protein-polysaccharide hydrogels (over the last ten years). Additionally, it characterizes the most recent developments in hydrogel induction methods and the most recent application progress of hydrogels as food matrices as carriers for the targeted delivery of bioactive compounds. Finally, this article provides a future perspective on the need to evaluate the feasibility of using plant-based proteins and polysaccharides to develop food matrices that protect nutrients, including bioactive substances, throughout processing, storage, and digestion until they reach the specific targeted area of the digestive system.

Multi-crosslinked network chitosan films containing caffeic acid and Fe3+ with high anti-oxidation and anti-UV abilities

In this study, caffeic acid (CA) and Fe³⁺ were added to chitosan solution to prepare chitosan/caffeic acid/Fe³⁺ (CCAF) composite films. CA was used to introduce covalent bonds and hydrogen bonds. Fe³⁺ was used to introduce metal coordination bonds which combined with hydrogen bond and covalent bonds to form a multi-crosslinked system to enhance the tensile strength (TS), improve the antioxidant properties and UV resistance performance. The results showed that the TS of chitosan/caffeic acid (CCA) film with the addition of 0.3 mmol CA was increased by 36.6 % compared with pure chitosan film. The TS of the CCAF film increased from 42.6 MPa to 73.9 MPa with an increase of 73.5 %. The free radical scavenging rate of CCA film and CCAF film, in comparison to pure chitosan film, were improved by 155.7 % and 148.24 %, respectively. The UV resistance property of the CCAF solution was tested at 365 nm and the results showed that the UV barrier rate reached 99.99 %. The water vapor transmission (WVT) and water vapor permeability (WVP) of CCAF film both showed a 25.71 % reduction compared to that of the chitosan film. Besides, the composite film also showed excellent antibacterial properties, which provided the possibility for more applications.

A Biomimetic Smart Nanoplatform as “Inflammation Scavenger” for Regenerative Therapy of Periodontal Tissue

Introduction

The functional reconstruction of periodontal tissue defects remains a clinical challenge due to excessive and prolonged host response to various endogenous and exogenous pro-inflammatory stimuli. Thus, a biomimetic nanoplatform with the capability of modulating inflammatory response in a microenvironment-responsive manner is attractive for regenerative therapy of periodontal tissue.

Methods

Herein, a facile and green design of engineered bone graft materials was developed by integrating a biomimetic apatite nanocomposite with a smart-release coating, which could realize inflammatory modulation by “on-demand” delivery of the anti-inflammatory agent through a pH-sensing mechanism.

Results

In vitro and in vivo experiments demonstrated that this biocompatible nanoplatform could facilitate the clearance of reactive oxygen species in human periodontal ligament stem cells under inflammatory conditions via inhibiting the production of endogenous proinflammatory mediators, in turn contributing to the enhanced healing efficacy of periodontal tissue. Moreover, this system exhibited effective antimicrobial activity against common pathogenic bacteria in the oral cavity, which is beneficial for the elimination of exogenous pro-inflammatory factors from bacterial infection during healing of periodontal tissue.

Conclusion

The proposed strategy provides a versatile apatite nanocomposite as a promising “inflammation scavenger” and propels the development of intelligent bone graft materials for periodontal and orthopedic applications.

Non-Supported and PET-Supported Chitosan Membranes for Pervaporation: Production, Characterization, and Performance

The objective of this study was to develop non-supported and PET-supported chitosan membranes that were cross-linked with glutaraldehyde, then evaluate their physical-chemical, morphological, and mechanical properties, and evaluate their performance in the separation of ethanol/water and limonene/linalool synthetic mixtures by hydrophilic and target-organophilic pervaporation, respectively. The presence of a PET layer did not affect most of the physical-chemical parameters of the membranes, but the mechanical properties were enhanced, especially the Young modulus (76 MPa to 398 MPa), tensile strength (16 MPa to 27 MPa), and elongation at break (7% to 26%), rendering the supported membrane more resistant. Regarding the pervaporation tests, no permeate was obtained in target-organophilic pervaporation tests, regardless of membrane type. The support layer influenced the hydrophilic pervaporation parameters of the supported membrane, especially in reducing transmembrane flux (0.397 kg∙m-2∙h-1 to 0.121 kg∙m-2∙h-1) and increasing membrane selectivity (611 to 1974). However, the pervaporation separation index has not differed between membranes (228 for the non-supported and 218 for the PET-supported membrane), indicating that, overall, both membranes had a similar performance. Thus, the applicability of each membrane is linked to specific applications that require a more resistant membrane, greater transmembrane fluxes, and higher selectivity.

Hybrid Graphenene Oxide/Cellulose Nanofillers to Enhance Mechanical and Barrier Properties of Chitosan-Based Composites

Chitosan-based hybrid nanocomposites, containing cellulose nanocrystals (CNCs), graphene oxide (GO), and borate as crosslinking agents, were successfully prepared by solution-casting technique. The synergistic effect of the two fillers, and the role of the cross-linker, in enhancing the structural and functional properties of the chitosan polymer, was investigated. XPS results confirm the chemical interaction between borate ions and hydroxyl groups of chitosan, GO, and CNCs. The morphological characterization shows that the GO sheets are oriented along the casting surface, whereas the CNC particles are homogenously distributed in the sample. Results of tensile tests reveal that the presence of graphene oxide enhances the elastic modulus, tensile strength, elongation at break, and toughness of chitosan, while cellulose and borate induce an increase in the elastic modulus and stress at the yield point. In particular, the borate-crosslinked chitosan-based sample containing 0.5 wt% of GO and 0.5 wt% of CNCs shows an elongation at a break value of 30.2% and a toughness value of 988 J*m⁻³ which are improved by 124% and 216%, respectively, compared with the pristine chitosan. Moreover, the water permeability results show that the presence of graphene oxide slightly increases the water barrier properties, whereas the borate and cellulose nanocrystals significantly reduce the water vapor permeability of the polymer by about 50%. Thus, by modulating the content of the two reinforcing fillers, it is possible to obtain chitosan-based nanocomposites with enhanced mechanical and water barrier properties which can be potentially used in various applications such as food and electronic packaging.

Dialdehyde Starch Nanocrystals as a Novel Cross-Linker for Biomaterials Able to Interact with Human Serum Proteins

In recent years, new cross-linkers from renewable resources have been sought to replace toxic synthetic compounds of this type. One of the most popular synthetic cross-linking agents used for biomedical applications is glutaraldehyde. However, the unreacted cross-linker can be released from the materials and cause cytotoxic effects. In the present work, dialdehyde starch nanocrystals (NDASs) were obtained from this polysaccharide nanocrystal form as an alternative to commonly used cross-linking agents. Then, 5-15% NDASs were used for chemical cross-linking of native chitosan (CS), gelatin (Gel), and a mixture of these two biopolymers (CS-Gel) via Schiff base reaction. The obtained materials, forming thin films, were characterized by ATR-FTIR, SEM, and XRD analysis. Thermal and mechanical properties were determined by TGA analysis and tensile testing. Moreover, all cross-linked biopolymers were also characterized by hydrophilic character, swelling ability, and protein absorption. The toxicity of obtained materials was tested using the Microtox test. Dialdehyde starch nanocrystals appear as a beneficial plant-derived cross-linking agent that allows obtaining cross-linked biopolymer materials with properties desirable for biomedical applications.

Phosphorylation modification on functional and structural properties of fish gelatin: The effects of phosphate contents

The gel, rheological and structural properties of fish gelatin (FG) were investigated through phosphorylation with different ratios of sodium pyrophosphate (TSPP) (FG:TSPP = 40:0, 40:1, 40:2, 40:4, and 40:6). It showed that phosphorylation modification significantly increased gel strength, textural properties, emulsification, and emulsification stability of FG. The surface hydrophobicity and intrinsic fluorescence of phosphorylated FG were also significantly increased. Rheological results revealed that the apparent viscosity, melt/gel points, and gel strength of FG were increased by phosphorylation with TSPP, but shortened the gelation time. Low field nuclear magnetic resonance (LF-NMR) showed that phosphorylation reduced mobility of water in FG. FTIR results indicated that phosphorylation increased the β-sheet/β-turn contents but reduced the random coil contents. This study might provide a new guideline for the exploration of TSPP phosphorylation increased the functional properties of FG.

Facile fabrication of highly dispersed Pd catalyst on nanoporous chitosan and its application in environmental catalysis

With the development of society, the problem of environmental pollution is becoming increasingly serious, such as the typical pollution of nitro compounds or dyes in wastewater. An effective strategy to remove these organic pollutants is catalytic conversion, including converting them into more chemically valuable compounds. Herein, a nanoporous chitosan microsphere derived from seafood waste resources of chitin was constructed via sol-gel method, which was used as supports to successfully fabricate a highly dispersed Pd nano-catalyst (mean diameter ~ 1.8 nm) via a facile way based on its interconnected nanoporous structure and rich functional -OH/-NH₂ groups. The synthetic catalyst was applied to the hydrogenation of toxic nitro compounds, which could efficiently and selectively catalyze the conversion of nitro compounds. The catalyst was also used for the degradation of some representative dyes, which also showed good activity and stability, suggesting potential of applications in green environmental governance.

Genipin-Crosslinking Effects on Biomatrix Development for Cutaneous Wound Healing: A Concise Review

Split skin graft (SSG), a standard gold treatment for wound healing, has numerous limitations such as lack of fresh skin to be applied, tedious process, severe scarring, and keloid formation followed by higher risks of infection. Thus, there is a gap in producing polymeric scaffolds as an alternative for wound care management. Bioscaffold is the main component in tissue engineering technology that provides porous three-dimensional (3D) microarchitecture for cells to survive. Upon skin tissue reconstruction, the 3D-porous structure ensures sufficient nutrients and gaseous diffusion and cell penetration that improves cell proliferation and vascularization for tissue regeneration. Hence, it is highly considered a promising candidate for various skin wound healing applications. To date, natural-based crosslinking agents have been extensively used to tailor the physicochemical and mechanical properties of the skin biomatrix. Genipin (GNP) is preferable to other plant-based crosslinkers due to its biological activities, such as antiinflammatory and antioxidant, which are key players to boost skin wound healing. In addition, it has shown a noncytotoxic effect and is biocompatible with human skin cells. This review validated the effects of GNP in biomatrix fabrication for skin wound healing from the last 7 years of established research articles and stipulated the biomaterial development-scale point of view. Lastly, the possible role of GNP in the skin wound healing cascade is also discussed. Through the literature output, it can be concluded that GNP has the capability to increase the stability of biomatrix and maintain the skin cells viability, which will contribute in accelerating wound healing.

Magnesium hydroxide coated hollow glass microspheres/chitosan composite aerogels with excellent thermal insulation and flame retardancy

The development of an environmental-friendly thermal insulation and flame retardant material has attracted widespread attention in modern architecture. In this work, a kind of novel aerogel composites were prepared by incorporation of Mg(OH)₂ coated hollow glass microspheres (HGM) into chitosan (CSA) matrix and then cross-linking by glutaraldehyde (abbreviated as CSA-HGM-Mg(OH)₂). The as-prepared composite aerogel exhibits vertical directional channel with high porosity and excellent thermal insulation with a low thermal conductivity of 0.035 W m^-1 k^-1. Besides, it shows excellent flame retardancy with a high limit oxygen index (LOI) value up to 50.8, which is one of the highest values among the most of flame retardants reported previously. Also, a very low peak heat release rate (pHRR) of 24.12 kW m^-2 was obtained which makes the aerogel composite reaching UL-94 V-0 rating. Such results may be attributed to a synergy effect by combination of its abundantly porous structure derived from HGM to give a better thermal insulation and excellent nonflammability of CSA and Mg(OH)₂ to offer a superior flame retardancy. Taking advantages of its high mechanical strength, low cost materials, simple and scalable preparation method, CSA-HGM-Mg(OH)₂ aerogel composites may hold great potential for future thermal insulation and flame retardant applications.

Crosslinkers for polysaccharides and proteins: Synthesis conditions, mechanisms, and crosslinking efficiency, a review

Polysaccharides and proteins are important macromolecules for developing hydrogels devoted to biomedical applications. Chemical hydrogels offer chemical, mechanical, and dimensional stability than physical hydrogels due to the chemical bonds among the chains mediated by crosslinkers. There are many crosslinkers to synthesize polysaccharides and proteins based on hydrogels. In this review, we revisited the crosslinking reaction mechanisms between synthetic or natural crosslinkers and polysaccharides or proteins. The selected synthetic crosslinkers were glutaraldehyde, carbodiimide, boric acid, sodium trimetaphosphate, N,N'-methylene bisacrylamide, and polycarboxylic acid, whereas the selected natural crosslinkers included transglutaminase, tyrosinase, horseradish peroxidase, laccase, sortase A, genipin, vanillin, tannic acid, and phytic acid. No less important are the reactions involving click chemistry and the macromolecular crosslinkers for polysaccharides and proteins. Literature examples of polysaccharides or proteins crosslinked by the different strategies were presented along with the corresponding highlights. The general mechanism involved in chemical crosslinking mediated by gamma and UV radiation was discussed, with particular attention to materials commonly used in digital light processing. The evaluation of crosslinking efficiency by gravimetric measurements, rheology, and spectroscopic techniques was presented. Finally, we presented the challenges and opportunities to create safe chemical hydrogels for biomedical applications.

Multi-crosslinked hydrogels with instant self-healing and tissue adhesive properties for biomedical applications

Due to the defects like long gelling time, inferior mechanical properties and weak adhesion, in-situ forming hydrogels are still restricted in biomedical applications like viscera rupture and targeted therapy. To address these problems, a new kind of multi-crosslinked hydrogel (G-OKG-DA) consisting of gelatin, oxidized konjac glucomannan (OKG), and dopamine (DA) is proposed in this study. The resulting hybrid hydrogel is endowed with a short gelling time (about 3 min) and injectable capacity. According to the mechanical and adhesive tests, G-OKG-DA hydrogel shows a robust tensile strength of 23.94 kPa, as well as a higher adhesive strength (around 150 kPa) than commercial fibrin glue. In addition, an instant self-healing behavior of G-OKG-DA hydrogel can be found, which is attributed to multi-crosslinking reactions including Schiff-base dynamic covalent bonds between OKG and gelatin, oxidative polymerization of DA, and catechol-mediated chemistry like Michael addition and DA-quinone coupling. Importantly, the multi-crosslinked hydrogel will not compromise its hemocompatibility and cytocompatibility in vitro, suggesting potential applications in biomedical fields as tissue adhesive and implants. This article is protected by copyright. All rights reserved.

Double noncovalent network chitosan/hyperbranched polyethylenimine/Fe3+ films with high toughness and good antibacterial activity

The application of pure chitosan films is significantly limited due to their poor mechanical properties. In this study, a novel type of chitosan/hyperbranched polyethylenimine (CHP) and chitosan/hyperbranched polyethylenimine/Fe³⁺ (CHPF) films with high toughness and good antibacterial activity were prepared through a noncovalent crosslinking method. From the tensile test results, the strain and toughness of the CHP film increased by 798.1% and 292.3%, respectively, compared with pure chitosan film, after the addition of 20% hyperbranched polyethylenimine (HPEI). The addition of trace metal iron ions (3 mg) forms a metal coordination bond with the amine group on HPEI, as well as the hydroxyl group and amine group on chitosan, and develops a double noncovalent bond network structure with hydrogen bonding, which further enhances the mechanical tensile strength of the chitosan-based film, with an increase of 48.4%. Interestingly, HPEI and Fe³⁺ can be used as switches to increase and decrease the fluorescence property of chitosan, respectively. Furthermore, the CHP and CHPF films showed good antibacterial activity against S. aureus and E. coli.

Double noncovalent network chitosan/hyperbranched polyethylenimine/Fe³⁺ films.

Removal of difenoconazole and nitenpyram by composite calcium alginate beads during apple juice clarification

A novel genipin crosslinked calcium alginate/chitosan/polydopamine composite beads (g-Alg/CS/PDA) was synthesized for the removal of residual difenoconazole and nitenpyram during the clarification of apple juice. The composite beads with low potential health risks for all of the main materials were natural, green and biocompatible. Since g-Alg/CS/PDA can both clarify and adsorb, pesticide residues could be removed during the clarification of juice without additional steps. The g-Alg/CS/PDA beads were characterized, and the adsorption parameters, including the pesticide residue levels, adsorption time, pH, ionic strength, fructose concentration and adsorbent dose, were optimized. The adsorption data were fitted to the Freundlich isotherm model (R² = 0.9604, 0.9625) and the pseudo-second-order kinetic model (R² = 0.9993, 0.9999). The results indicated that the adsorption behavior of beads was heterogeneous. Moreover, the rate was controlled by several factors. The adsorption mechanism of two pesticides was also discussed. Hydrophobic and π-π conjugation interactions played a dominant role for the adsorption of difenoconazole, while hydrogen bonding and electrostatic interactions were the main factors for nitenpyram.

Characterisation of Rapid In Situ Forming Gelipin Hydrogel for Future Use in Irregular Deep Cutaneous Wound Healing

The irregular deep chronic wound is a grand challenge to be healed due to multiple factors including slow angiogenesis that causing regenerated tissue failure. The narrow gap of deep wounds could hinder and slow down normal wound healing. Thus, the current study aimed to develop a polymerised genipin-crosslinked gelatin (gelipin) hydrogel (GNP_GH) as a potential biodegradable filler for the abovementioned limitations. Briefly, GNP_GH bioscaffolds have been developed successfully within three-minute polymerisation at room temperature (22-24 °C). The physicochemical and biocompatibility of GNP_GH bioscaffolds were respectively evaluated. Amongst GNP_GH groups, the 0.1%GNP_GH10% displayed the highest injectability (97.3 ± 0.6%). Meanwhile, the 0.5%GNP_GH15% degraded within more than two weeks with optimum swelling capacity (108.83 ± 15.7%) and higher mechanical strength (22.6 ± 3.9 kPa) than non-crosslinked gelatin hydrogel 15% (NC_GH15%). Furthermore, 0.1%GNP_GH15% offered higher porosity (>80%) and lower wettability (48.7 ± 0.3) than NC_GH15%. Surface and cross-section SEM photographs displayed an interconnected porous structure for all GNP_GH groups. The EDX spectra and maps represented no major changes after GNP modification. Moreover, no toxicity effect of GNP_GH against dermal fibroblasts was shown during the biocompatibility test. In conclusion, the abovementioned findings indicated that gelipin has excellent physicochemical properties and acceptable biocompatibility as an acellular rapid treatment for future use in irregular deep cutaneous wounds.

Reversibility of the gel, rheological, and structural properties of alcohol pretreated fish gelatin: Effect of alcohol types

The reversibility of gel property of alcohol (methanol, ethanol)-pretreated fish gelatin (FG) were investigated through removing alcohol solutions by freeze drying. Results showed that the gel strength and the hardness of FG could be retained (1%, 40%) or even improved (1% methanol) using low or high concentration alcohol solutions, while decreased in medium concentration alcohol solutions. Compared with untreated FG, rheology results showed that, all alcohol solutions pretreated FG had lower apparent viscosity, while higher alcohol solutions pretreated ones decreased the gel and melt points and shorten the gelation time. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis showed that methanol pretreated FG had the higher α contents than those of ethanol pretreated. Circular dichroism spectra results indicated that β-sheet could be decreased after removing ethanol solutions, whereas the β-sheet increased after removing the methanol solutions. Moreover, low field nuclear magnetic resonance relaxation test showed that pretreated FG had lower transverse relaxation times of internal water (T₂₁ and T₂₂ ) compared to that of the untreated FG. Overall, FG still retains higher gel properties after removing the low or high alcohol concentrations.

Effect of Washing Treatment on the Textural Properties and Bioactivity of Silica/Chitosan/TCP Xerogels for Bone Regeneration

Silica/biopolymer hydrogel-based materials constitute very attractive platforms for various emerging biomedical applications, particularly for bone repair. The incorporation of calcium phosphates in the hybrid network allows for designing implants with interesting biological properties. Here, we introduce a synthesis procedure for obtaining silica–chitosan (CS)–tricalcium phosphate (TCP) xerogels, with CS nominal content varying from 4 to 40 wt.% and 10 to 20 wt.% TCP. Samples were obtained using the sol-gel process assisted with ultrasound probe, and the influence of ethanol or water as washing solvents on surface area, micro- and mesopore volume, and average pore size were examined in order to optimize their textural properties. Three washing solutions with different soaking conditions were tested: 1 or 7 days in absolute ethanol and 30 days in distilled water, resulting in E1, E7, and W30 washing series, respectively. Soaked samples were eventually dried by evaporative drying at air ambient pressure, and the formation of interpenetrated hybrid structures was suggested by Fourier transformed infrared (FTIR) spectroscopy. In addition the impact that both washing solvent and TCP content have on the biodegradation, in vitro bioactivity and osteoconduction of xerogels were explored. It was found that calcium and phosphate-containing ethanol-washed xerogels presented in vitro release of calcium (2–12 mg/L) and silicon ions (~60–75 mg/L) after one week of soaking in phosphate-buffered saline (PBS), as revealed by inductive coupled plasma (ICP) spectroscopy analysis. However, only the release of silicon was detected for water-washed samples. Besides, all the samples exhibited in vitro bioactivity in simulated body fluid (SBF), as well as enhanced in vitro cell growth and also significant focal adhesion development and maturation.

Sustainable, Highly Efficient and Superhydrophobic Fluorinated Silica Functionalized Chitosan Aerogel for Gravity-Driven Oil/Water Separation

A superhydrophobic fluorinated silica functionalized chitosan (F-CS) aerogel is constructed and fabricated by a simple and sustainable method in this study in order to achieve highly efficient gravity-driven oil/water separation performance. The fluorinated silica functionalization invests the pristine hydrophilic chitosan (CS) aerogel with promising superhydrophobicity with a water contact angle of 151.9°. This novel F-CS aerogel possesses three-dimensional structure with high porosity as well as good chemical stability and mechanical compression property. Moreover, it also shows striking self-cleaning performance and great oil adsorption capacity. Most importantly, the as-prepared aerogels exhibits fast and efficient separation of oil/water mixture by the gravity driven process with high separation efficiency. These great performances render the prepared F-CS aerogel a good candidate for oil/water separation in practical industrial application.

Advances in carbohydrate-based polymers for the design of suture materials: A review

Suture materials constitute one of the largest biomedical material groups with a huge global market of $ 1.3 billion annually and employment in over 12 million procedures per year. Suture materials have radically evolved over the years, from basic strips of linen to more advanced synthetic polymer sutures. Yet, the journey to the ideal suture material is far from over and we now stand on the brink of a new era of improved suture materials with greater safety and efficacy. This next step in the evolutionary timeline of suture materials, involves the use of natural, carbohydrate polymers that have, until recent years, never before been considered for suture material applications. This review exposes the latest and most important advancements in suture material development while digging deep into how natural, carbohydrate polymers can serve to advance this field.

Genipin-cross-linked hydrogels based on biomaterials for drug delivery: a review

Genipin is a naturally occurring nontoxic cross-linker, which has been widely used for drug delivery due to its excellent biocompatibility, admirable biodegradability and stable cross-linked attributes. These advantages led to its extensive application in the fabrication of hydrogels for drug delivery. This review describes the physicochemical characteristics and pharmacological activities of genipin and attempts to elucidate the detailed mechanisms of the cross-linking reaction between genipin and biomaterials. The current article entails a general review of the different biomaterials cross-linked by genipin: chitosan and its derivatives, collagen, gelatin, etc. The genipin-cross-linked hydrogels for various pharmaceutical applications, including ocular drug delivery, buccal drug delivery, oral drug delivery, anti-inflammatory drug delivery, and antibiotic and antifungal drug delivery, are reported. Finally, the future research directions and challenges of genipin-cross-linked hydrogels for pharmaceutical applications are also discussed in this review.

Effects of gellan gum and inulin on mixed-gel properties and molecular structure of gelatin

Gellan gum (GG) is often added to gelatin (GL) to improve the gel property. GG-based or inulin (IL)-based hydrogels were developed. Rigid and brittle gels or smooth and delicate gels were prepared with GG and IL, respectively. This study aimed to explore the properties and interaction mechanisms of the mixed-gel system containing GL, GG, and IL, in which different ratios of GG-IL (0.4%) (10:0, 8:2, 6:4, 5:5, 4:6, 2:8, and 0:10) were added to GL (6%). Texture profiles, rheological properties, water mobility, intermolecular forces, circular dichroism (CD) spectra, and microstructures were analyzed. The results showed that addition of GG-IL could improve the hardness, chewiness, and cohesiveness of mixed-gel, besides maintaining appropriate springiness. Water mobility of the mixed-gel decreased while viscoelasticity increased upon the addition GG. At GG:IL = 2:8, the melting temperature of mixed-gel was far higher than that of GL gel itself. The GL-GG-IL gel showed decrease in nonspecific bonding and increase in hydrogen bonding compared with the GL gel. CD spectra indicated the promotion of GL unfolding by GG, hence suggesting the binding of GG to GL; binding ability was better at GG:IL >5:5. Cryo-SEM provided evidence for the formation of cross-linked network within GL-GG-IL. Overall, we concluded that addition of GG-IL to GL system would be most suitable for improving the properties of mixed-gel. This finding may be potentially applicable in the further development of gel food products, such as meat jellies and gummy jellies.