Determination of degree of substitution of formyl groups in polyaldehyde dextran by the hydroxylamine hydrochloride method

About the assessment of the degree of oxidation of cellulose during periodate reaction: Comparison of different characterization techniques and their discrepancies

This study focuses on the side reactions responsible for the low efficiency of the periodate-chlorite oxidation sequence of cellulose. Discrepancies are systematically observed between different commonly-used characterization methods for assessing the degree of oxidation (DO) of cellulose. Indeed, the different titration methods of the aldehyde groups found in the dialdehyde cellulose (DAC) generated by the Malaprade reaction on cellulose, do not generally fit the titration of the carboxyl groups found in the dicarboxycellulose (DCC), generated after chlorite oxidation of the DAC. Possible side reactions affecting the Malaprade and chlorite reactions, or affecting the accuracy of the titrations, are presented here and discussed. Studying periodate consumption, iodate generation, organic acids release during the reactions, fiber mass yield, sodium hydroxide consumption during the β-alkoxy-elimination reaction of DAC, 13C NMR spectra of DAC and DCC, and carboxyl titration of DCC, allowed to conclude that chlorite did not fully oxidize the aldehyde groups in the DAC, but only about one aldehyde out of two. It was found that the non-oxidized aldehydes in the DAC were hindered by hemiacetal-type linkages. This study refutes several well-established hypotheses from the literature when applied to reactions under mild conditions.

Oxidized Xanthan Gum Cross-Linked N-O Carboxymethyl Chitosan Hydrogel Promotes Spheroid Formation of Murine Fibroblast by Increasing Cell-Cell Interaction and Integrin αv Expression

Naturally derived Schiff-based hydrogels are widely fabricated for tissue engineering applications. However, limited studies have explored how the physicochemical and functional groups on polymer chains affect cell behavior in three dimensions. To address this limitation, we fabricated cytocompatible N-O carboxymethyl chitosan (NOCC) cross-linked with oxidized xanthan gum (OXG), incorporating various aldehyde (-CHO) contents (NO1, NO2, and NO3) while maintaining a constant concentration of NOCC, resulting in hydrogels with diverse viscoelastic and aldehyde content properties. The results demonstrated significant differences in storage modulus (G') and loss modulus (G″), attributed to cross-linking density through imine bonds (-C═N-). These differences influenced murine fibroblast aggregation, spheroid formation, and cell migration, proliferation, and viability over time. Both NO1 and NO2 exhibited good cell viability, with slight differences in spheroid morphology compared to those of NO3 and Matrigel samples. To further explore cell behaviors, integrin αV (CD51) expression was assessed using fluorescence-activated cell sorting (FACS) and immunofluorescence. The results aligned with prior observations, with the quantitative analysis of integrin αV expression, normalized to 4',6-diamidino-2-phenylindole (DAPI) fluorescence, revealing a notable 2.1-fold increase in fluorescence intensity for the NO2 hydrogel in comparison to NO1 (p < 0.0001). These findings indicate that the hydrogel composed of 2% (w/v) NOCC cross-linked with 2% (w/v) OXG in a 1:1 (v/v) ratio represents the optimal condition for promoting murine fibroblast growth and spheroid formation. These results provide a robust foundation for future research aimed at modulating cell behavior through precise adjustments of scaffold properties, thereby advancing the potential for translational applications from laboratory research to clinical settings.

An Enhanced Long-Term Wet Adhesion Strategy of Spatial Control the Emergence of Dual Covalent Cross-Linking for Sutureless Cornea Transplant

Corneal transplantation regeneration requires bioadhesives to perform long-term and stable adhesion functions in a wet environment. However, many current studies focus on the instantaneous or short-term adhesion persistence of bioadhesives, and ignore the evaluation of their long-term wet adhesion behaviors which is urgent for keratoplasty repair process. In view of this situation, a dual covalent cross-linking hydrogel (ASO) bioadhesive is developed. The ASO bioadhesive comprised acrylated gelatin(G-AA), thiolated gelatin(G-SH), and oxidized dextran (OD). Introduction of thiol chemistry made the emergence of ASO dual covalent cross-linking controllable by UV light irradiation. The analysis of this feature revealed an intriguing phenomenon. The ASO bioadhesive demonstrated spatially specific control over cross-linking behavior by first penetrating the tissue and then initiating cross-linking, thereby significantly enhancing its long-term wet adhesion ability. The ASO bioadhesive can maintain more than 50% adhesion after being immersed in wet environment for one month. Subsequently, ASO bioadhesive demonstrated long-term wet adhesive stability once again on corneal lamellar transplantation model through maintaining strong anchorage of corneal donor to recipient bed and promoting their integration. The unprecedented adhesive mechanism presented in this study provided innovated theoretical basis for designing bioadhesives with superior long-term wet adhesion.

Dual Functionalized Absorbable Hairy Cellulose-Based Fabric for Efficient Hemostasis and Antibacterial Property

Uncontrolled hemorrhage and subsequent infection at the injury sites are major causes of trauma-related mortality. Herein, we present a novel approach to creating a multifunctional biodegradable textile fabric with hemostatic and antibacterial properties, synthesized through chemical modification, including etherification, oxidation (aldehyde), and amination via a Schiff-based reaction between octadecyl ammonium and oxidized cellulose, followed by calcium ion cross-linking. The fabric demonstrated significant antibacterial efficay against both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria, validated through assays such as colony counting, minimum inhibitory concentration (MIC), scanning electron microscopy, and fluorescent staining using Acridine Orange and Propidium Iodide. In vitro assessments demonstrated superior performance compared to commercial alternatives in red blood cell attachment (90%), blood clotting index (6%), platelet adhesion, and clotting time (20s) (P-value < 0.001). In vivo studies using a Wistar rat liver injury model confirmed the fabric's effectiveness, reducing bleeding time (3.1 and 6.2-fold) and blood loss (1.2 and 5.48-fold) compared to available commercial hemostatic agents. Pathological, hematological, and biochemical analyses demonstrated the biocompatibility and biodegradability of our developed material with no evidence of systemic toxicity, significant localized inflammatory reactions in the liver, renal, or skin tissues, or vascular thrombosis stimulation.

ROS fueled autonomous sol-gel-sol transitions for on-demand modulation of inflammation in osteoarthritis

Osteoarthritis is the most prevalent form of arthritis, and a leading cause of pain and long-term disability. Dysregulation of redox homeostasis is a key feature in the pathological progression of osteoarthritis that amplifies the inflammatory response, aggravates synovitis and accelerates cartilage degradation. Herein, a hemin and chitosan-mediated antioxidant gel inducing ROS conversion (hc-MAGIC) was constructed to targeting oxidative stress for osteoarthritis treatment. The optimized hc-MAGIC exhibited autonomous sol-gel-sol transition properties, which enable to be administered via intra-articular injections, prolong retention in the joint cavity, and controlled modulation of inflammation in response to ROS. Notably, with extracellular ROS fueled, hc-MAGIC could address hypoxia in the osteoarthritic joint cavity through spatiotemporally controlled generation of oxygen (O2). Moreover, hc-MAGIC restored the impaired antioxidative capacity of macrophages by upregulating HO-1 on demand, resulting in suppressing excessive intracellular ROS generation. Consequently, by restoring both extracellular and intracellular redox homeostasis in osteoarthritic joints, hc-MAGIC markedly reversed the inflammatory microenvironment to support chondrogenesis, prevented cartilage degradation, and promoted cartilage repair by augmenting cartilage matrix formation. Therefore, featuring its sol-gel-sol transition properties，ROS-to-O2 conversion, and dual-mode redox regulation, hc-MAGIC offers a potent novel therapy for on-demand modulation of inflammation in osteoarthritis.

A fully sustainable, flexible, and degradable lignocellulose-based composite film enabled by a bio-based polyimine vitrimer

Traditionally unsustainable and nondegradable fossil-based plastics have resulted in serious environment pollution problem. Renewable and biodegradable lignocellulose biomass is a promising raw martial for developing environmentally friendly plastic alternatives. However, lignocellulose biomass itself is non-thermoplastic crosslinking networks consisting of cellulose, lignin, and hemicellulose, resulting in a huge challenge to thermoform its into plastic alternatives. Vitrimers which own dynamic network exchange character can enable polymer materials excellent thermo-processability and recyclability. Herein, a thermoforming strategy of lignocellulose biomass was successfully developed by integrating wood powders (WPs) including natural wood powder (NWP), oxidized wood powder (OWP), and aminated wood powder (AWP) into the dynamic networks of a bio-based polyimine vitrimer (Bio-PI). The resulting WPs/Bio-PI mixtures can be easily processed into a fully sustainable lignocellulose-based composite film (LCF) by hot-pressing. The obtained LCF shows good flexibility and strength with the highest tensile strain, toughness, and tensile strength of 61 %, 365 MJ m-3, and 9 MPa, respectively. The LCF also exhibits heat-triggered re-shaping capability, ultralow water absorption ratio (<1 %), high water stability, and excellent resistance to dilute acid/alkali solutions. Moreover, the LCF can be completely chemical-degraded because of the reversible crosslinking performance of Bio-PI. Such LCF represents an environmentally friendly plastic alternative.

Hyaluronic Acid-Coated Melt Electrowritten Scaffolds Promote Myoblast Attachment, Alignment, and Differentiation

Purpose

In muscle tissues, anisotropic cell alignment is essential for optimal muscle fiber development and function. Biomaterials for muscle tissue engineering must guide cellular alignment while supporting cell proliferation and myogenic differentiation.

Methods

Here, we describe the fabrication of a tissue-engineered construct consisting of a scaffold of aligned poly(ε-caprolactone) (PCL) microfibers coated in a dynamic covalent hydrazone crosslinked hyaluronic acid (HA) hydrogel to support myoblast attachment, alignment, and differentiation. Norbornene modification of HA further enabled functionalization with fibronectin-derived arginine-glycine-aspartic acid (RGD) peptide. Scaffolds were fabricated using melt electrowriting (MEW), a three-dimensional (3D)-printing technique that uses stabilization of fluid columns to produce precisely aligned polymeric microfibers. We evaluated scaffolds with fiber diameters of 10 μm, 20 μm, and 30 μm of non-coated, HA-coated, and HA-RGD-coated MEW scaffolds through immunocytochemistry and creatine kinase activity assays.

Results

HA-coated and HA-RGD-coated scaffolds showed increased cellular attachment of C2C12 mouse skeletal myoblasts on all fiber diameters compared to non-coated scaffolds, with HA-RGD-coated scaffolds demonstrating the highest cell attachment. All scaffolds supported cellular alignment along the fibers. Cells differentiated on scaffolds showed anisotropic alignment with increased myotube formation on HA-RGD-coated scaffolds as seen by myosin heavy chain (MHC) staining. Highest creatine kinase (CK) activity on day 5 signified the successful differentiation of C2C12 cells into mature myotubes.

Conclusion

This unique combination of tunable biophysical and biochemical cues enables the creation of a biomimetic tissue engineered scaffold, providing a platform for new therapeutic approaches for muscle regeneration.

Versatile conductive hydrogel orchestrating neuro-immune microenvironment for rapid diabetic wound healing through peripheral nerve regeneration

Diabetic wound (DW), notorious for prolonged healing processes due to the unregulated immune response, neuropathy, and persistent infection, poses a significant challenge to clinical management. Current strategies for treating DW primarily focus on alleviating the inflammatory milieu or promoting angiogenesis, while limited attention has been given to modulating the neuro-immune microenvironment. Thus, we present an electrically conductive hydrogel dressing and identify its neurogenesis influence in a nerve injury animal model initially by encouraging the proliferation and migration of Schwann cells. Further, endowed with the synergizing effect of near-infrared responsive release of curcumin and nature-inspired artificial heterogeneous melanin nanoparticles, it can harmonize the immune microenvironment by restoring the macrophage phenotype and scavenging excessive reactive oxygen species. This in-situ formed hydrogel also exhibits mild photothermal therapy antibacterial efficacy. In the infected DW model, this hydrogel effectively supports nerve regeneration and mitigates the immune microenvironment, thereby expediting the healing progress. The versatile hydrogel exhibits significant therapeutic potential for application in DW healing through fine-tuning the neuro-immune microenvironment.

Dextran stabilised hematite: a sustainable anode in aqueous electrolytes

During the last decades, the use of innovative hybrid materials in energy storage devices has led to notable advances in the field. However, further enhancement of their electrochemical performance faces significant challenges nowadays, imposed by the materials used in the electrodes and the electrolyte. Such problems include the high solubility of both the organic and the inorganic anode components in the electrolyte as well as the limited intrinsic electronic conductivity and substantial volume variation of the materials during cycling. The present work focuses on the fabrication of novel and sustainable anode electrodes for use in energy storage devices, utilizing cross-linked oxidized dextran (Ox-Dex) as the binder and hematite (α-Fe2O3) cubes as the active component. The ion diffusion mechanism within the anode electrode materials, as well as their cycling stability, were studied via cyclic voltammetry measurements, using Li+, Zn2+ and Al3+ aqueous electrolytes. The hybrid iron oxide electrodes exhibited the highest electrochemical performance in the Al2(SO4)3 electrolyte (3000 mA g-1), followed by ZnSO4 (2000 mA g-1) and Li2SO4 (800 mA g-1). The differences in the performance of the anodes for the three investigated electrolytes were attributed to the ionic radii of Li+, Zn2+ and Al3+, which affect the rate of ion diffusion within the material lattice exhibiting the highest diffusion coefficient of 4.64 × 10-9 cm2 s-1 in Al3+. Notably, the hybrid anodes demonstrated superior cycling performance (with the lowest variance percentage of 1.3% for hybrid compared to 38.1% for the bare in the presence of Zn2+), underlining the pivotal role of the natural binder. This was attributed to hydrogen bonding interactions, which increase the contact points between the inorganic and polymeric components, resulting in a more uniform network structure. Additionally, the cross-linking of Ox-Dex promotes stability and tolerance to the volume expansion of the electrodes. These results underscore the immense potential of the proposed hybrid electrodes in the field of energy storage.

Mussel-inspired modified regenerated cellulose as tissue adhesive and antibacterial gauze: A promising approach for rapid hemostasis in non-compressible hemorrhage

Uncontrollable hemorrhage leads to high mortality rates; thus, engineering effective hemostatic materials is crucial for rapid hemostasis. Developing hemostatic materials for rapid coagulation, antibacterial activity, and easy removal without compromising clot integrity remains a challenge. Herein, a multifunctional hemostatic gauze was engineered by modifying regenerated cellulose textile through multiple sequential chemical reactions, including carboxymethylation, crosslinking with CaCl2/ZnCl2 solution, oxidation, and polymerization with dopamine. Provided gauze demonstrated remarkable wet-tissue adhesion (890 kPa) that physically sealing the area to prevent blood loss. The engineered gauze exhibits excellent antibacterial activity (against S. aureus and E. coli) and enhanced hemostatic ability (clotting time (20S), attachment of red blood cells (∼93 %) and platelets (∼80 %)). The complete hemostasis and stable clot formation without secondary bleeding were achieved by synthesized gauze in 20s, 50s, and 100s for the rat and rabbit liver, and rat femoral artery injury models, respectively. That was significantly faster hemostasis (4-14-fold reduction in time) and lower blood loss (3-fold reduction) compared to the commercial hemostatic textiles (p < 0.001). Biochemical, hematological, and pathological examinations revealed no evidence of systemic and local inflammation or toxic effects in the rat organs. The engineered hemostatic gauze exhibits outstanding characteristics of a hemostatic material for clinical applications.

A biomimetic injectable chitosan/alginate hydrogel biocopmosites encapsulating selenium- folic acid nanoparticles for regeneration of spinal cord injury: An in vitro study

Spinal cord injury (SCI) poses significant challenges to regenerative medicine due to its limited self-repair capabilities. In this study, we engineered a biomimetic injectable hydrogel using modified chitosan and alginate biopolymers encapsulating selenium-folic acid nanoparticles (Se-FA NPs) to facilitate SCI regeneration. The hydrogel exhibited a unique porous structure attributed to the incorporation of nanofiber fragments, enhancing its biocompatibility and bioactivity. Through a series of in vitro evaluations, including cell viability assays, proliferation studies, gene expression analysis, we assessed the hydrogel's cytocompatibility and its potential for supporting neural cell growth. Our results demonstrate the promising efficacy of the hydrogel in providing a conducive microenvironment for neural tissue regeneration. Moreover, the sustained release of Se-FA NPs from the hydrogel system offers neuroprotective, antioxidative, and anti-inflammatory benefits crucial for SCI therapy. Overall, our biomimetic hydrogel biocomposites hold great potential as a therapeutic strategy for promoting spinal cord regeneration, highlighting their significance in advancing the field of regenerative medicine.

Carboxymethyl Chitosan-Based Antioxidant Hydrogel Accelerates Diabetic Wound Healing

Diabetic wound healing is hampered due to oxidative stress, exacerbated inflammation, and impaired angiogenesis in the wounds. A pH-sensitive antioxidant hydrogel based on carboxymethyl chitosan (CMCS), oligoprocyanidins (OPC), and oxide dextran (Oxd) is prepared to accelerate diabetic wound healing. The hydrogel network is formed via imine and hydrogen bonding interactions in the presence of hydroxyl, amino, and aldehyde groups, and deferoxamine (DFO) is incorporated into the hydrogel. The hydrogel shows pH-triggered drug release, a good antioxidant, and anti-inflammatory properties, and can promote tube formation and cell migration in vitro. Moreover, the hydrogel can accelerate wound healing in streptozotocin (STZ)-induced diabetic mice by regulating the inflammation environment with up-regulation of anti-inflammatory factors (IL-4 and IL-10) and down-regulation of pro-inflammatory factors (TNF-α and IL-6), and promoting angiogenesis with up-regulation of HIF-1α, VEGF, and CD31. Thus, the pH-sensitive antioxidant hydrogel provides a promising therapeutic strategy for diabetic wound healing.

Melt processing of chemically modified cellulosic fibres with only water as plasticiser: Effects of moisture content and processing temperature

To replace petroleum-derived polymers with cellulose fibres, it is desirable to have the option of melt processing. However, upon heating, cellulose degradation typically starts before the material reaches its softening temperature. Alternatives to plastics should also, ideally, be recyclable via existing recycling streams. Here, we address the problem of melt processing cellulose as fibres while preserving recyclability. Native cellulose fibres were partially modified to dialcohol cellulose to impart thermoplastic characteristics. We demonstrate melt processing of these modified fibres with only water as plasticiser. Processability was investigated at selected processing temperatures and initial moisture content by monitoring the axial force of the extruder screws as a rheological indicator. The effects on molecular structure, fibre morphology and material properties were characterised by NMR spectroscopy, microscopy, tensile testing, fibre morphology analysis and X-ray diffraction. When comparing the melt-processed extrudate with handsheets, the already exceptional ductility was further increased. Moderate losses in tensile strength and stiffness were observed and are attributable to a loss of crystallinity and fibre shortening. This is the first report of strong and durable extrudates using cellulosic fibres as the only feedstock. Finally, the potential for recycling the processed material with unmodified fibres by paper recycling procedures was demonstrated.

Preparation and characterization of PEG-Dex macromolecular schiff base particles and their application on the stabilization of water-in-water emulsion

In this study, polyethylene glycol (PEG) and dextran (Dex) were chemically modified to obtain amino-functionalized PEG (PEG-(NH2)2) and oxidized dextran (ODex). They were subsequently reacted via -NH2 and -CHO groups to synthesize a macromolecular Schiff base particle. The structures, morphologies, and thermal properties of the macromolecular Schiff base particle were characterized using Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetry analysis (TGA). The macromolecular Schiff base particle was then employed as a stabilizer to stabilize Dex/PEG water-in-water (W/W) emulsions, and the effects of stabilizer composition, concentration, and dextran oxidation degree on emulsion phase separation and microstructure were investigated. The results from the laser particle size analyzer indicate that the macromolecular Schiff base stabilizers have particle sizes ranging from 100 to 200 nm and exhibit an interpenetrating network structure, as observed in SEM images. A decrease in emulsion droplet size was observed with increasing mass ratio of PEG-(NH2)2 to ODex, ODex oxidation degree, and stabilizer concentration. Rheological analysis showed that the viscosity of W/W emulsions decreased with increasing shear rate. Contact angle measurements indicated that the macromolecular Schiff base stabilizers preferentially interacted with the continuous phase of PEG, thereby promoting emulsion stability.

Injectable Nanocomposite Hydrogel with Synergistic Biofilm Eradication and Enhanced Re-epithelialization for Accelerated Diabetic Wound Healing

Diabetic wounds remain a critical clinical challenge due to their harsh microenvironment, which impairs cellular function, hinders re-epithelialization and tissue remodeling, and slows healing. Injectable nanocomposite hydrogel dressings offer a promising strategy for diabetic wound repair. In this study, we developed an injectable nanocomposite hydrogel dressing (HDL@W379) using LAP@W379 nanoparticles and an injectable hyaluronic acid-based hydrogel (HA-ADH-ODEX). This dressing provided a sustained, pH-responsive release of W379 antimicrobial peptides, effectively regulating the wound microenvironment to enhance healing. The HDL@W379 hydrogel featured multifunctional properties, including mechanical stability, injectability, self-healing, biocompatibility, and tissue adhesion. In vitro, the HDL@W379 hydrogel achieved synergistic biofilm elimination and subsequent activation of basal cell migration and endothelial cell tube formation. Pathway analysis indicated that the HDL@W379 hydrogel enhances basal cell migration through MEK/ERK pathway activation. In methicillin-resistant Staphylococcus aureus (MRSA)-infected diabetic wounds, the HDL@W379 hydrogel accelerated wound healing by inhibiting bacterial proliferation and promoting re-epithelialization, regenerating the granulation tissue, enhancing collagen deposition, and facilitating angiogenesis. Overall, this strategy of biofilm elimination and basal cell activation to continuously regulate the diabetic wound microenvironment offers an innovative approach to treating chronic wounds.

Chitosan/dextran-based organohydrogel delivers EZH2 inhibitor to epigenetically reprogram chemo/immuno-resistance in unresectable metastatic melanoma

Melanoma either intrinsically possesses resistance or rapidly acquires resistance to anti-tumor therapy, which often leads to local recurrence or distant metastasis after resection. In this study, we found histone 3 lysine 27 (H3K27) demethylated by an inhibitor of histone methyltransferase EZH2 could epigenetically reverse the resistance to chemo-drug paclitaxel (PTX), or enhance the efficacy of immune checkpoint inhibitor anti-TIGIT via downregulating TIGIT ligand CD155. Next, to address the complexity in the combination of multiple bioactive molecules with distinct therapeutic properties, we developed a polysaccharides-based organohydrogel (OHG) configured with a heterogenous network. Therein, hydroxypropyl chitosan (HPC)-stabilized emulsions for hydrophobic drug entrapment were crosslinked with oxidized dextran (Odex) to form a hydrophilic gel matrix to facilitate antibody accommodation, which demonstrated a tunable sustained release profile by optimizing emulsion/gel volume ratios. As results, local injection of OHG loaded with EZH2 inhibitor UNC1999, PTX and anti-TIGIT did not only synergistically enhance the cytotoxicity of PTX, but also reprogrammed the immune resistance via bi-directionally blocking TIGIT/CD155 axis, leading to the recruitment of cytotoxic effector cells into tumor and conferring a systemic immune memory to prevent lung metastasis. Hence, this polysaccharides-based OHG represents a potential in-situ epigenetic-, chemo- and immunotherapy platform to treat unresectable metastatic melanoma.

Powdered Medical Adhesive with Long Lasting Adhesion in Water Environment

Medical adhesives have been used under surgical conditions. However, it is always a big challenge to maintain long-term adhesion in a water environment. Besides, it usually takes a long time to complete the adhesion, and the operation might be complicated. In this study, tannic acid and gelatin solution under acidic conditions were mixed, flocculated, lyophilized, and crushed; thus, a powdered medical adhesive (POWDER) was prepared with long-lasting adhesion in a water environment, convenience, and low price. Tannic acid bound gelatin and maintained adhesive force primarily through hydrogen bonding and reacted with amino sulfhydryl and other amino acid residues after oxidation into aldehyde, exhibiting excellent underwater adhesion. Oxidized dextran (ODex) powder rich in an aldehyde group was introduced to provide covalent binding in the adhesive. In vitro and in vivo studies showed that POWDER could quickly adhere to various tissues in the water environment. In vitro skin adhesion experiments demonstrated that it could achieve effective adhesion in a water environment for up to 60 days. Its blood compatibility, low cytotoxicity, and biodegradability were also verified. The POWDER developed in this study is of great significance for patients who need rapid wound treatments.

NIR-II Image-Guided Wound Healing in Hypoxic Diabetic Foot Ulcers: The Potential of Ergothioneine-Luteolin-Chitin Hydrogels

Hypoxic diabetic foot ulcers (HDFUs) pose a challenging chronic condition characterized by oxidative stress damage, bacterial infection, and persistent inflammation. This study introduces a novel therapeutic approach combining ergothioneine (EGT), luteolin (LUT), and quaternized chitosan oxidized dextran (QCOD) to address these challenges and facilitate wound healing in hypoxic DFUs. In vitro, assessments have validated the biosafety, antioxidant, and antimicrobial properties of the ergothioneine-luteolin-chitin (QCOD@EGT-LUT) hydrogel. Furthermore, near-infrared II (NIR-II) fluorescence image-guided the application of QCOD@EGT-LUT hydrogel in simulated HDFUs. Mechanistically, QCOD@EGT-LUT hydrogel modulates the diabetic wound microenvironment by reducing reactive oxygen species (ROS). In vivo studies demonstrated increased expression of angiogenic factors mannose receptor (CD206) and latelet endothelial cell adhesion molecule-1 (PECAM-1/CD31), coupled with decreased inflammatory factors tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6), thereby promoting diabetic wound healing through up-regulation of transforming growth factor β-1 (TGF-β1).

Biomimetic Nanozyme-Decorated Smart Hydrogel for Promoting Chronic Refractory Wound Healing

Chronic refractory wounds have become a serious threat to human health and are characterized by prolonged inflammation, recurrent bacterial infections, and elevated ROS levels. However, current therapeutic strategies usually target a unilateral healing function and are unable to tackle the complexity and sensitivity of chronic refractory wound healing. This study fabricated a biomimetic nanozyme based on rhein (Cu-rhein NSs), which effectively mimics the activity of superoxide dismutase (SOD) for scavenging various free radicals. Additionally, zinc oxide microspheres (ZnO MSs) were prepared to enhance the antibacterial activity and mechanical properties of the modified hydrogel. Cu-rhein NSs and ZnO MSs were comodified onto an extracellular matrix-mimetic dual-network smart hydrogel constructed from oxidized sodium alginate, gelatin, and borax via dynamic borate and Schiff base bonds. The smart hydrogel presented the good biocompatibility and targeted the unique acidic microenvironment with high oxidative stress of chronic refractory wounds, intelligently releasing bionic nanozymes to effectively eliminate bacteria, reduce inflammatory responses, and scavenge multiple free radicals for reducing ROS. In vivo experiments on the rat model based on diabetic infection showed that the smart hydrogel could effectively eliminate bacteria, promote vascular regeneration and collagen deposition, reduce inflammatory response, and accelerate the healing of diabetic-infected wounds (almost complete healing within 14 days). The advantages of an intelligent, biomimetic tissue regeneration cascade management strategy against diabetic infected wound healing are highlighted.

Multi-Functional Biomaterial for the Treatment and Prevention of Central Line-Associated Bloodstream Infections

Central venous catheters are among the most used medical devices in hospitals today. Despite advances in modern medicine, catheter infections remain prevalent, causing significant morbidity and mortality worldwide. Here, SteriGel is reported, which is a multifunctional hydrogel engineered to prevent and treat central line-associated bloodstream infections (CLABSI). The mechanical properties of SteriGel are optimized to ensure appropriate gelation kinetics, bio-adhesiveness, stretchability, and recoverability to promote durability upon application and to provide persistent protection against infection. In vitro assays demonstrated that SteriGel exhibits long-term antimicrobial efficacy and has bactericidal effects against highly resistant patient-derived pathogens known to be frequently associated with CLABSI. SteriGel outperformed Biopatch, which is a clinically used device for CLABSI, in ex vivo cadaver studies that simulate clinical scenarios. Furthermore, SteriGel has biocompatible, pro-healing, and anti-inflammatory properties in vitro and in a rat subcutaneous injection model, suggesting a potential synergistic effect in the prevention and treatment of CLABSI. SteriGel is a multifunctional adherent biomaterial with potent antimicrobial effects for sustained sterility while promoting healing of the catheter incision site to protect against infection.

A dialdehyde pullulan cross-linking strategy for immobilizing protamine onto silk fiber surfaces to achieve durable antibacterial function

Covalent immobilization of antibacterial peptides (APs) onto silk protein-based materials has always been a challenge due to the lack of green and efficient macromolecular cross-linkers. Here, we proposed a dialdehyde polysaccharide cross-linker oxidized from pullulan for grafting a natural AP protamine (PM) onto silk fiber surface through a simple cold pad-batch process. The oxidized pullulan (OP) was linked to silk fiber surface through Schiff reaction and used for mediated cross-linking of PM also via Schiff base linkages. This modification introduced abundant PM guanidine groups on the fiber leading to much-desired antibacterial activity, and considerable improvement in the moisture transfer properties and shade depth. FTIR, XPS, SEM studies confirmed the presence of PM and the cross-linking structure between the polysaccharide and peptides on the fiber surfaces. The antibacterial activity imparted by this process was retained even after 20 washing and 50 rubbing cycles proving versatility and durability. Further, the process did not affect other critical silk properties such as appearance, tensile strength, biological safety, etc. Immobilization of PM onto silk fibers through this novel green polysaccharide cross-linker makes silk more appealing and usable and could also enlighten the attempts of cross-linking other protein materials.

Crosslinking of gelatin Schiff base hydrogels with different structural dialdehyde polysaccharides as novel crosslinkers: Characterization and performance comparison

Few studies have been conducted on the relationship between the crosslinking ability of dialdehyde polysaccharides (DPs) with different structures and the structure and properties of hydrogels. Herein, the effects of dialdehyde sodium alginate (DSA), dialdehyde guar gum (DGG), and dialdehyde dextran (DDE) as crosslinking agents for gelatin (GE)-based hydrogels were comparatively studied. First, the structure and aldehyde content of DPs were evaluated. Subsequently, the structure, crosslinking degree, and physicochemical properties of GE/DP hydrogels were characterized. Compared with pure GE hydrogels, GE/DP hydrogels had higher thermal stability and mechanical properties. Moreover, the aldehyde content of DPs was ordered as follows: DSA < DGG < DDE. The higher crosslinking degree of the hydrogels formed by DPs with a higher aldehyde content resulted in smaller hydrogel pores, higher mechanical strength, and a lower equilibrium swelling rate. These observations provide a theoretical basis for selecting crosslinking candidates for hydrogel-specific applications.

Multifunctional injectable oxidized sodium alginate/carboxymethyl chitosan hydrogel for rapid hemostasis

Uncontrolled bleeding from incompressible or irregularly shaped wounds is a major factor in the death of people in the battlefield or surgery process. Ideal rapid hemostatic materials should have the performance of rapid hemostasis and at the same time can be applied to a variety of complex wound trauma types, in addition, excellent antimicrobial properties, adhesion, biocompatibility, degradation, and the non-toxicity of degradation products are also necessary, but there are fewer hemostatic materials that meet these requirements. Herein, we prepared an injectable hemostatic hydrogel based on the natural products sodium alginate (SA) and carboxymethyl chitosan (CMC). Oxidized sodium alginate (OSA) was prepared by the oxidation reaction of NaIO4 with SA, and OSA with aldehyde group was mixed with CMC with amino group to rapidly form an in situ injectable hemostatic hydrogel (OSA/CMC) by the Schiff base reaction. OSA/CMC hydrogel exhibited excellent antimicrobial and adhesion properties by the Schiff base reaction. In addition, OSA/CMC hydrogel directly activate the endogenous coagulation pathway through the synergistic effect of OSA, CMC to enhance the hemostatic effect. The results of in vivo hemostasis study showed that OSA/CMC hydrogel significantly accelerated hemostasis and reduced blood loss in liver hemorrhage model and tail amputation model. Therefore, OSA/CMC hydrogel is expected to be a potential material in the direction of rapid clinical hemostasis due to its good adhesion properties, antimicrobial properties, biocompatibility, blood compatibility, and efficient rapid hemostasis.

Antimicrobial starch-based cryogels and hydrogels for dual-active food packaging applications

The present study reports on the valorisation of starch waste biomass to produce dual-active cryogels and hydrogels able to adsorb water and deliver antimicrobial substances for fresh food packaging applications. Starch hydrogels were prepared by oxidation with sodium metaperiodate in water and mild conditions, while cryogels were obtained by freeze-drying process. To explore the role of starch composition on the final properties of materials, two starches differing in amylose/amylopectin ratio, were evaluated. The prepared materials were microstructurally and morphologically characterized by FTIR and NMR spectroscopy (1D, 2D, and DOSY experiments), and SEM microscopy. To provide the materials with active properties, they were loaded with antimicrobial molecules by absorption, or by crosslinking via Schiff-base reaction. All materials demonstrated high water absorption capacity and ability to deliver volatile molecules, including diacetyl and complex mixtures like mint essential oil. The release profiles of the adsorbed molecules were determined through quantitative NMR spectroscopy over time. The antibacterial activity was successfully demonstrated against Gram-positive bacterial strains for unloaded cryogels and hydrogels, and after loading with diacetyl and essential oil. The developed materials can be regarded as part of active pads for food packaging applications capable to control moisture inside the package and inhibit microbial contamination.

Development of Phase-Separating Microfiber Network Hydrogels to Promote In Vitro Vascularization

Engineered vascularized tissues in vitro exhibit the potential for transplantation therapy and disease modeling. Despite efforts to design hydrogels as cell culture platforms for in vitro vascularization, development of vascularized tissues recapitulating the natural structures and functions remains difficult due to a poor understanding of the relationships between the matrix microstructures and tube formation of endothelial cells. Herein, we developed microfiber network hydrogels with microporous structures by controlling the liquid-liquid phase separation (LLPS) of proteins and matrix structures in hydrogels. Extracellular matrix protein gelatin was modified with hydrogen-bonding moieties and mixed with hyaluronic acid sodium salt to form microfiber network structures. Gelatin gelation and hyaluronic acid sodium salt dissolution led to the formation of a microporous microfiber network hydrogel formation. Matrix structures of hydrogels were modified by controlling LLPS that affects endothelial cell tube formation. Vascularization was improved using laminin peptides and coculturing with mesenchymal stem cells. Overall, our approach exhibits the potential to induce in vitro vascularization for regenerative medicine and disease modeling applications.

Nanofiber-reinforced self-healing polysaccharide-based hydrogel dressings for pH discoloration monitoring and treatment of infected wounds

The escalating global health concern arises from chronic wounds induced by bacterial infections, posing a significant threat to individuals. Consequently, an imperative exist for the development of hydrogel dressings to facilitate prompt wound monitoring and efficacious wound management. To this end, pH-sensitive bromothymol blue (BTB) and pH-responsive drug tetracycline hydrochloride (TH) were introduced into the polysaccharide-based hydrogel to realize the integration of wound monitoring and controlled treatment. Polysaccharide-based hydrogels were formed via a Schiff base reaction by cross-linking carboxymethyl chitosan (CMCS) on an oxidized sodium alginate (OSA) skeleton. BTB was used as a pH indicator to monitor wound infection through visual color changes visually. TH could be dynamically released through the pH response of the Schiff base bond to provide effective treatment and long-term antibacterial activity for chronically infected wounds. In addition, introducing polylactic acid nanofibers (PLA) enhanced the mechanical properties of hydrogels. The multifunctional hydrogel has excellent mechanical, self-healing, injectable, antibacterial properties and biocompatibility. Furthermore, the multifaceted hydrogel dressing under consideration exhibits noteworthy capabilities in fostering the healing process of chronically infected wounds. Consequently, the research contributes novel perspectives towards the advancement of intelligent and expeditious bacterial infection monitoring and dynamic treatment platforms.

Synthesis, characterization and stability of crosslinked chitosan-maltodextrin pH-sensitive nanogels

Polysaccharide-based nanogels offer a wide range of chemical compositions and are of great interest due to their biodegradability, biocompatibility, non-toxicity, and their ability to display pH, temperature, or enzymatic response. In this work, we synthesized monodisperse and tunable pH-sensitive nanogels by crosslinking, through reductive amination, chitosan and partially oxidized maltodextrins, by keeping the concentration of chitosan close to its overlap concentration, i.e. in the dilute and semi-dilute regime. The chitosan/maltodextrin nanogels presented sizes ranging from 63 ± 9 to 279 ± 16 nm, showed quasi-spherical and cauliflower-like morphology, reached a ζ-potential of +36 ± 2 mV and maintained a colloidal stability for up to 7 weeks. It was found that the size and surface charge of nanogels depended both on the oxidation degree of maltodextrins and chitosan concentration, as well as on its degree of acetylation and protonation, the latter tuned by pH. The pH-responsiveness of the nanogels was evidenced by an increased size, owed to swelling, and ζ-potential when pH was lowered. Finally, maltodextrin-chitosan biocompatible nanogels were assessed by cell viability assay performed using the HEK293T cell line.

Effect of sodium alginate block type on the physicochemical properties and curcumin release behavior of quaternized chitosan-oxidized sodium alginate Schiff base hydrogels

Controlling bioactive ingredients release by modulating the 3D network structure of cross-linked hydrogels is important for functional food development. Hereby, oxidized sodium alginate (OSA) with varying aldehyde contents was formed by periodate oxidation of sodium alginate (SA) with different β-d-mannuronic acid (M) and α-l-guluronic acid (G) ratios (M/G = 1:2, 1:1, and 2:1) and its structure was characterized. Moreover, hydrogels were prepared via Schiff base and electrostatic interactions between quaternized chitosan (QCS) and OSA. The properties of hydrogels such as microstructure, thermal stability, swelling and controlled release were investigated. The results showed that OSA with M/G = 1:2 had the highest content of aldehyde groups, and the hydrogel formed by it and QCS had higher thermal stability and a denser network structure with the lowest equilibrium swelling rate, which could better control the release of curcumin. Additionally, it had good self-healing and can recover rapidly after the rupture of its network structure.

Improved physicochemical properties and in vitro digestion of walnut oil microcapsules with soy protein isolate and highly oxidized konjac glucomannan as wall materials

This study investigated the effect of the oxidation degrees of oxidized konjac glucomannan (OKGM) on the encapsulation efficiency (EE), physicochemical and in vitro digestive properties of soy protein isolate (SPI)-based microcapsules walnut oil using experimental and computational approaches. Microcapsules had the highest EE when the ratio of OKGM and SPI to oil was 2.5:1. With increasing the oxidation degree of OKGM, the EE of microcapsules was increased and the hygroscopicity was decreased. Molecular dynamics simulation results showed that SPI/oil/highly OKGM had relatively low binding energy (-4.03 × 106 kJ/mol) and strong electrostatic interactions, which may contribute to a higher EE and lower hygroscopicity of microcapsules, respectively. The oxidative stability of the oil was markedly improved by SPI and OKGM, and microcapsules prepared with SPI and highly OKGM had the highest in vitro digestion. This study provided theoretical support for broadening the application of microcapsules prepared with SPI and OKGM.

Ti/Ta-based composite polysaccharide scaffolds for guided bone regeneration in total hip arthroplasty

Guided bone regeneration can play an important role in orthopedic applications. This work presents the synthesis and characterization of composite scaffolds based on polysaccharides loaded with microparticles of titanium or tantalum as novel materials proposed for composite systems with promising characteristics for guided bone regeneration. Ti/Ta composite scaffolds were synthesized using chitosan and gellan gum as organic substrates and crosslinked with oxidized dextran resulting in stable inorganic-organic composites. Physico-chemical characterization revealed a uniform distribution of metal nanoparticles within the scaffolds that showed a release of metals lower than 5 %. In vitro biological assays demonstrated that Ta composites exhibit a 2 times higher ALP activity than Ti and a higher capacity to support the full differentiation of human mesenchymal stem cells into osteoblasts. These results highlight their potential for bone regeneration applications.

Eggshell membrane powder reinforces adhesive polysaccharide hydrogels for wound repair

Multifunctional polysaccharide hydrogels with strong tissue adhesion, and antimicrobial and hemostatic properties are attractive wound healing materials. In this study, a chitosan-based hydrogel (HCS) was designed, and its properties were enhanced by incorporating oxidized eggshell membrane (OEM). Hydrogel characterization and testing results showed that the hydrogel had excellent antimicrobial properties, cytocompatibility, satisfactory adhesion properties on common substrates, and wet-state adhesion capacity. A rat liver injury model confirmed the significant hemostatic effect of the hydrogel. Finally, the ability of the hydrogel to promote wound healing was verified using rat skin wound repair experiments. Our findings indicate that HCS/OEM hydrogels with added eggshell membrane fibers have better self-healing properties, mechanical strength, adhesion, hemostatic properties, and biocompatibility than HCS hydrogels, in addition to having superior repair performance in wound repair experiments. Overall, the multifunctional polysaccharide hydrogels fabricated in this study are ideal for wound repair.

Intracellular infection-responsive macrophage-targeted nanoparticles for synergistic antibiotic immunotherapy of bacterial infection

Intracellular bacteria are considered to play a key role in the failure of bacterial infection therapy and increase of antibiotic resistance. Nanotechnology-based drug delivery carriers have been receiving increasing attention for improving the intracellular antibacterial activity of antibiotics, but are accompanied by disadvantages such as complex preparation procedures, lack of active targeting, and monotherapy, necessitating further design improvements. Herein, nanoparticles targeting bacteria-infected macrophages are fabricated to eliminate intracellular bacterial infections via antibiotic release and upregulation of intracellular reactive oxygen species (ROS) levels and proinflammatory responses. These nanoparticles were formed through the reaction of the amino group on selenocystamine dihydrochloride and the aldehyde group on oxidized dextran (ox-Dex), which encapsulates vancomycin (Van) through hydrophobic interactions. These nanoparticles could undergo targeted uptake by macrophages via endocytosis and respond to the bacteria-infected intracellular microenvironment (ROS and glutathione (GSH)) for controlled release of antibiotics. Furthermore, these nanoparticles could consume intracellular GSH and promote a significant increase in the level of ROS in macrophages, subsequently up-regulating the proinflammatory response to reinforce antibacterial activity. These nanoparticles can accelerate bacteria-infected wound healing. In this work, nanoparticles were fabricated for bacteria-infected macrophage-targeted and microenvironment-responsive antibiotic delivery, cellular ROS generation, and proinflammatory up-regulation activity to eliminate intracellular bacteria, which opens up a new possibility for multifunctional drug delivery against intracellular infection.

Engineering peptide-modified alginate-based bioinks with cell-adhesive properties for biofabrication

Alginate (ALG) and its oxidised form alginate-dialdehyde (ADA) are highly attractive materials for hydrogels used in 3D bioprinting as well as drop-on-demand (DoD) approaches. However, both polymers need to be modified using cell-adhesive peptide sequences, to obtain bioinks exhibiting promising cell-material interactions. Our study explores the modification of ALG- and ADA-based bioinks with the adhesive peptides YIGSR (derived from laminin), RRETEWA (derived from fibronectin) and IKVAV (derived from laminin) for 3D bioprinting. Two coupling methods, carbodiimide and Schiff base reactions, were employed to modify the polymers with peptides. Analytical techniques, including FTIR and NMR were used to assess the chemical composition, revealing challenges in confirming the presence of peptides. The modified bioinks exhibited decreased stability, viscosity, and stiffness, particularly-ADA-based bioinks in contrast to ALG. Sterile hydrogel capsules or droplets were produced using a manual manufacturing process and DoD printing. NIH/3T3 cell spreading analysis showed enhanced cell spreading in carbodiimide-modified ADA, Schiff base-modified ADA, and PEG-Mal-modified ADA. The carbodiimide coupling of peptides worked for ADA, however the same was not observed for ALG. Finally, a novel mixture of all used peptides was evaluated regarding synergistic effects on cell spreading which was found to be effective, showing higher aspect ratios compared to the single peptide coupled hydrogels in all cases. The study suggests potential applications of these modified bioinks in 3D bioprinting approaches and highlights the importance of peptide selection as well as their combination for improved cell-material interactions.

Chitosan-Oxidized Pullulan Hydrogels Loaded with Essential Clove Oil: Synthesis, Characterization, Antioxidant and Antimicrobial Properties

Emulsion hydrogels are promising materials for encapsulating and stabilizing high amounts of hydrophobic essential oils in hydrophilic matrices. In this work, clove oil-loaded hydrogels (CS/OP-C) are synthesized by combining covalent and physical cross-linking approaches. First, clove oil (CO) was emulsified and stabilized in a chitosan (CS) solution, which was further hardened by Schiff base covalent cross-linking with oxidized pullulan (OP). Second, the hydrogels were subjected to freeze-thaw cycles and, as a result, the clove oil was stabilized in physically cross-linked polymeric walls. Moreover, due to cryogelation, the obtained hydrogels exhibited sponge-like porous interconnected morphology (160-250 µm). By varying the clove oil content in the starting emulsion and the degree of cross-linking, the hydrogels displayed a high water retention capacity (swelling ratios between 1300 and 2000%), excellent elastic properties with fast shape recovery (20 s) after 70% compression, and controlled in vitro clove oil release in simulated skin conditions for 360 h. Furthermore, the prepared clove oil-loaded hydrogels had a strong scavenging activity of 83% and antibacterial and antifungal properties, showing a bacteriostatic effect after 48 and 72 h against S. aureus and E. coli. Our results recommend the new clove oil-embedded emulsion hydrogels as promising future materials for application as wound dressings.

Solid Wood Modification toward Anisotropic Elastic and Insulative Foam-Like Materials

The methods used to date to produce compressible wood foam by top-down approaches generally involve the removal of lignin and hemicelluloses. Herein, we introduce a route to convert solid wood into a super elastic and insulative foam-like material. The process uses sequential oxidation and reduction with partial removal of lignin but high hemicellulose retention (process yield of 72.8%), revealing fibril nanostructures from the wood's cell walls. The elasticity of the material is shown to result from a lamellar structure, which provides reversible shape recovery along the transverse direction at compression strains of up to 60% with no significant axial deformation. The compressibility is readily modulated by the oxidation degree, which changes the crystallinity and mobility of the solid phase around the lumina. The performance of the highly resilient foam-like material is also ascribed to the amorphization of cellulosic fibrils, confirmed by experimental and computational (molecular dynamics) methods that highlight the role of secondary interactions. The foam-like wood is optionally hydrophobized by chemical vapor deposition of short-chained organosilanes, which also provides flame retardancy. Overall, we introduce a foam-like material derived from wood based on multifunctional nanostructures (anisotropically compressible, thermally insulative, hydrophobic, and flame retardant) that are relevant to cushioning, protection, and packaging.

Statistical optimization of hydrazone-crosslinked hyaluronic acid hydrogels for protein delivery

Hydrazone-crosslinked hydrogels are attractive protein delivery vehicles for regenerative medicine. However, each regenerative medicine application requires unique hydrogel properties to achieve an ideal outcome. The properties of a hydrogel can be impacted by numerous factors involved in its fabrication. We used design of experiments (DoE) statistical modeling to efficiently optimize the physicochemical properties of a hyaluronic acid (HA) hydrazone-crosslinked hydrogel for protein delivery for bone regeneration. We modified HA with either adipic acid dihydrazide (HA-ADH) or aldehyde (HA-Ox) functional groups and used DoE to evaluate the interactions of three input variables, the molecular weight of HA (40 or 100 kDa), the concentration of HA-ADH (1-3% w/v), and the concentration of HA-Ox (1-3% w/v), on three output responses, gelation time, compressive modulus, and hydrogel stability over time. We identified 100 kDa HA-ADH3.00HA-Ox2.33 as an optimal hydrogel that met all of our design criteria, including displaying a gelation time of 3.7 minutes, compressive modulus of 62.1 Pa, and minimal mass change over 28 days. For protein delivery, we conjugated affinity proteins called affibodies that were specific to the osteogenic protein bone morphogenetic protein-2 (BMP-2) to HA hydrogels and demonstrated that our platform could control the release of BMP-2 over 28 days. Ultimately, our approach demonstrates the utility of DoE for optimizing hydrazone-crosslinked HA hydrogels for protein delivery.

Luminescent lanthanide-containing gelatin/polydextran/laponite nanocomposite double-network hydrogels for processing and sensing applications

Lanthanide-containing nanomaterials have gained significant popularity for their utilization in polymeric networks, enabling the creation of luminescent nanocomposites for advanced applications. In this study, we developed a new type of lanthanide-containing nanocomposite hydrogels by incorporating terbium-containing laponite (Tb3+@Lap) into the networks of polyethyleneimine-modified gelatin/polydextran aldehyde (PG/PDA) through dynamic bonds. The structures and properties of the Tb3+@Lap-containing nanocomposite double-network (ncDN) hydrogels were comprehensively investigated in comparison with the DN hydrogels with a pure polymeric network and the Lap-containing ncDN hydrogels. The PG/PDA/Tb3+@Lap ncDN hydrogels with multiple dynamic bonds (i.e., imine bonds, coordination bonds, hydrogen bonds, and electrostatic interactions) exhibited remarkable characteristics of shear-thinning and self-healing, making them suitable for the construction of hydrogel scaffolds on a macroscale using fabrication techniques such as electrospinning and 3D printing. Moreover, the PG/PDA/Tb3+@Lap ncDN hydrogels have been demonstrated to act as sensitive and selective luminescent sensors for detecting copper ions. Taken together, a versatile lanthanide-containing ncDN hydrogel platform capable of dynamic features is developed for processing and sensing applications.

Kinetics of Periodate-Mediated Oxidation of Cellulose

The oxidation of cellulose to dialdehyde cellulose (DAC) is a process that has received increased interest during recent years. Herein, kinetic modeling of the reaction with sodium periodate as an oxidizing agent was performed to quantify rate-limiting steps and overall kinetics of the cellulose oxidation reaction. Considering a pseudo-first-order reaction, a general rate expression was derived to elucidate the impact of pH, periodate concentration, and temperature on the oxidation of cellulose and concurrent formation of cellulose degradation products. Experimental concentration profiles were utilized to determine the rate constants for the formation of DAC (k1), degradation constant of cellulose (k2), and degradation of DAC (k3), confirming that the oxidation follows a pseudo-first-order reaction. Notably, the increase in temperature has a more pronounced effect on k1 compared to the influence of IO4- concentration. In contrast, k2 and k3 display minimal changes in response to IO4- concentration but increase significantly with increasing temperature. The kinetic model developed may help with understanding the rate-limiting steps and overall kinetics of the cellulose oxidation reaction, providing valuable information for optimizing the process toward a faster reaction with higher yield of the target product.

Novel Injectable, Self-Healing, Long-Effective Bacteriostatic, and Healed-Promoting Hydrogel Wound Dressing and Controlled Drug Delivery Mechanisms

Multivalent ion cross-linking has been used to form hydrogels between sodium alginate (SA) and hyaluronic acid (HA) in previous studies. However, more stable and robust covalent cross-linking is rarely reported. Herein, we present a facile approach to fabricate a SA and HA hydrogel for wound dressings with injectable, good biocompatibility, and high ductility. HA was first reacted with ethylenediamine to graft an amino group. Then, it was cross-linked with oxidized SA with dialdehyde to form hydrogel networks. The dressing can effectively promote cell migration and wound healing. To increase the antibacterial property of the dressing, we successfully loaded tetracycline hydrochloride into the hydrogel as a model drug. The drug can be released slowly in the alkaline environment of chronic wounds, and the hydrogel releases drugs again in the more acidic environment with wound healing, achieving a long-term antibacterial effect. In addition, one-dimensional partial differential equations based on Fickian diffusion with time-varying diffusion coefficients and hydrogel thicknesses were used to model the entire complex drug release process and to predict drug release.

Mucoadhesive and thermosensitive Bletilla striata polysaccharide/chitosan hydrogel loaded nanoparticles for rectal drug delivery in ulcerative colitis

Ulcerative colitis (UC) is a chronic disease with diffuse mucosal inflammation limited to the colon. A topical drug delivery system that could be facilely performed and efficiently retained at colon are attractive for clinical ulcerative colitis treatment. Herein, a novel platform for rectal administration of thermosensitive hydrogel co-loaded with nanoparticles to treat ulcerative colitis was developed. Thiolated-hyaluronic acid was synthesized, and prepared nanoparticles with zein and Puerarin. And the Bletilla striata polysaccharide with colonic mucosa repair effect was oxidized, and mixed with chitosan and β-sodium glycerophosphate to prepare thermosensitive hydrogel. Thermosensitive hydrogels were combined with nanoparticles to investigate their mucosal adhesion, retention, and permeability, as well as their therapeutic effects on ulcerative colitis. Thiolated-hyaluronic acid nanoparticles had good stability, and could be quickly converted into hydrogel at body temperature when combined with thermosensitive hydrogel. The nanoparticles-loaded thermosensitive hydrogel also was excellent at mucosal penetration, enhancing the retention time of drugs in colon, and effectively controlling drug release. In vivo ulcerative colitis treatment revealed that the nanoparticles-loaded hydrogel significantly repaired the colonic mucosa and inhibit colonic inflammation. Therefore, the thermosensitive hydrogel co-loaded nanoparticles will have a promising application in effective treatment of ulcerative colitis by topical administration.

A hyaluronic acid / chitosan composite functionalized hydrogel based on enzyme-catalyzed and Schiff base reaction for promoting wound healing

The healing of full-thickness skin defect has been a clinical challenge. Hydrogels with multiple functions inspired by extracellular matrix are expected to be used as wound dressing. In this paper, dopamine-grafted oxidized hyaluronic acid was blended with quaternary ammonium chitosan to form a composite functionalized hydrogel by enzyme-catalyzed cross-linking and Schiff base reaction. The hydrogel has convenient preparation, good biocompatibility, antibacterial and antioxidant, high adhesion and self-healing properties. The results in vivo show that the hydrogel can effectively close the wound and accelerate the speed of wound healing by up-regulating the expression of angiogenic protein and promoting the distribution of collagen deposition more uniform and regular. It is expected that this composite functionalized hydrogel dressing has great potential in wound regeneration.

Di-aldehyde tunicate cellulose nanocrystal (D-tCNC) aerogels for drug delivery: Effect of D-tCNC composition on aerogel structure and release properties

Aerogels as drug carriers have the characteristics of a large specific surface area, high porosity and an elastic skeleton structure. Compared with traditional drug carriers, the use of aerogels as drug carriers can avoid the complexity of drug delivery and improve the efficiency of drug loading. In this work, the oxidation of tunicate cellulose nanocrystals (tCNCs) with NaIO4 was used to prepare di-aldehyde tunicate cellulose nanocrystals (D-tCNCs). Tetracycline (TC) was used as a drug model and pH-responsive drug-loaded aerogels were prepared by the Schiff base reaction between TC and the aldehyde group on D-tCNCs. The chemical structure, crystallinity, morphology, compression properties, porosity, swelling rate and drug loading properties were investigated by FT-IR, XRD, SEM and universal testing machines. The results showed that the porosity and equilibrium swelling ratio of the D-tCNC-TC aerogels were 95.87 % and 17.52 g/g, respectively. The stress of the D-tCNC-TC aerogel at 15 % compression was 0.07 MPa. Moreover, the analysis of drug-loaded aerogels indicated that the drug loading and encapsulation rates of D-tCNC-TC aerogels were 16.86 % and 78.75 %, respectively. In in vitro release experiments, the cumulative release rate of drug-loaded aerogel at pH = 1.2 and pH = 7.4 was 87.5 % and 79.3 %, respectively. These results indicated that D-tCNC-TC aerogels have good drug loading capacity and are pH-responsive in the pH range of 1.2 to 7.4. The prepared D-tCNC-TC aerogels are expected to be applied in drug delivery systems.

Collagen-based scaffolds with high wet-state cyclic compressibility for potential oral application

Soft tissue substitutes have been developed to treat gingival recessions to avoid a second surgical site. However, products of pure collagen for clinical application lack their original mechanical strengths and tend to degrade fast in vivo. In this study, a collagen-based scaffold crosslinked with oxidized sodium alginate (OSA-Col) was developed to promote mechanical properties. Compared with commercial products collagen matrix (CM) and collagen sponge (CS), OSA-Col scaffolds presented higher wet-state cyclic compressibility, early anti-degradation ability, similar hemocompatibility and cytocompatibility. Furthermore, in the subcutaneous implantation experiment, OSA2-Col3 scaffolds showed better anti-degradation performance than CS scaffolds and superior neovascularization than CM scaffolds. These results demonstrated that OSA2-Col3 scaffolds had potential as a new soft tissue substitute for the treatment of gingival recessions.

Fibrillar Hydrogel Based on Cellulose Nanocrystals Crosslinked via Diels-Alder Reaction: Preparation and pH-Sensitive Release of Benzocaine

A fibrillar hydrogel was obtained by covalent crosslinking via Diels-Alder reaction of two types of cellulose nanocrystals (CNCs) with furan and maleimide groups. Gelation has been studied at various ratios of components and temperatures in the range from 20 to 60 °C. It was shown that the rheological properties of the hydrogel can be optimized by varying the concentration and ratio of components. Due to the rigid structure of the CNCs, the hydrogel could be formed at a concentration of at least 5 wt%; however, it almost does not swell either in water with pH 5 or 7 or in the HBSS buffer. The introduction of aldehyde groups into the CNCs allows for the conjugation of physiologically active molecules containing primary amino groups due to the formation of imine bonds. Here, we used benzocaine as a model drug for conjugation with CNC hydrogel. The resulting drug-conjugated hydrogel demonstrated the stability of formulation at pH 7 and a pH-sensitive release of benzocaine due to the accelerated hydrolytic cleavage of the imine bond at pH < 7. The developed drug-conjugated hydrogel is promising as wound dressings for local anesthesia.

Tri-Component Hydrogel as Template for Nanocrystalline Hydroxyapatite Deposition Using Alternate Soaking Method for Bone Tissue Engineering Applications

Composite hydrogels containing apatite-like particles can act as scaffolds for osteoblast proliferation, with applications in bone tissue engineering. In this respect, porous biocompatible hydrogels were obtained from chitosan, oxidized pullulan, and PVA in different ratios. The stability of the hydrogels was ensured both by covalent bonds between aldehyde groups of oxidized pullulan and free amino groups of chitosan, and by physical bonds formed during freeze-thaw cycles and lyophilization. The deposition of calcium phosphates was performed by alternate soaking of the porous hydrogels into solutions with calcium and phosphate ions, assuring a basic pH required for hydroxyapatite formation. The mineralized hydrogels were characterized using FTIR spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, showing that inorganic particles containing between 80 and 92% hydroxyapatite were deposited in a high amount on the pore walls of the polymeric matrix. The composition of the organic matrix influenced the crystallization of calcium phosphates and the mechanical properties of the composite hydrogels. In vitro biological tests showed that mineralized hydrogels support the proliferation of MG-63 osteoblast-like cells to a greater extent compared to pristine hydrogels.

Acylhydrazone-derived whole pectin-based hydrogel as an injectable drug delivery system

Injectable hydrogel-based drug delivery systems have attracted more and more attention due to their sustained-release performance, biocompatibility, and 3D network. The present study showed whole pectin-based hydrogel as an injectable drug delivery system, which was developed from oxidized pectin (OP) and diacylhydrazine adipate-functionalized pectin (Pec-ADH) via acylhydrazone linkage. The as-prepared hydrogels were characterized by 1H NMR, FT-IR, and SEM techniques. The equilibrium swelling ratio of obtained hydrogel (i.e., sample gel 5) was up to 4306.65 % in the distilled water, which was higher than that in PBS with different pH values. Increasing the pH of the swelling media, the swelling ratio of all hydrogels decreased significantly. The results that involved the swelling properties indicated the salt- and pH-responsiveness of the as-prepared hydrogels. The drug release study presented that 5-FU can be persistently released for more than 12 h without sudden release. Moreover, the whole pectin-based hydrogel presented high cytocompatibility toward L929 cell lines, and the drug delivery system showed a high inhibitory effect on MCF-7 cell lines. All these results manifested that the acylhydrazone-derived whole pectin-based hydrogel was an excellent candidate for injectable drug delivery systems.

Direct ink writing of multifunctional nanocellulose and allyl-modified gelatin biomaterial inks for the fabrication of mechanically and functionally graded constructs

Recreating the intricate mechanical and functional gradients found in natural tissues through additive manufacturing poses significant challenges, including the need for precise control over time and space and the availability of versatile biomaterial inks. In this proof-of-concept study, we developed a new biomaterial ink for direct ink writing, allowing the creation of 3D structures with tailorable functional and mechanical gradients. Our ink formulation combined multifunctional cellulose nanofibrils (CNFs), allyl-functionalized gelatin (0.8-2.0 wt%), and polyethylene glycol dithiol (3.0-7.5 wt%). The CNF served as a rheology modifier, whereas a concentration of 1.8 w/v % in the inks was chosen for optimal printability and shape fidelity. In addition, CNFs were functionalized with azido groups, enabling the spatial distribution of functional moieties within a 3D structure. These functional groups were further modified using a spontaneous click chemistry reaction. Through additive manufacturing and a readily available static mixer, we successfully demonstrated the fabrication of mechanical gradients - ranging from 3 to 6 kPa in indentation strength - and functional gradients. Additionally, we introduced dual gradients by combining gradient printing with an anisotropic photocrosslinking step. The developed biomaterial ink opens up possibilities for printing intricate multigradient structures, resembling the complex hierarchical organization seen in living tissues.

Gelatin-Based Hybrid Hydrogel Scaffolds: Toward Physicochemical Liver Mimicry

There exists a clear need to develop novel materials that could serve liver tissue engineering purposes. Those materials need to be researched for the development of bioengineered liver tissue as an alternative to donor livers, as well as for materials that could be applied for scaffolds to develop an in vitro model for drug-induced liver injury (DILI) detection . In this paper, the hydrogels oxidized dextran-gelatin (Dexox-Gel) and norbornene-modified dextran-thiolated gelatin (DexNB-GelSH) were developed, and their feasibility toward processing via indirect 3D-printing was investigated with the aim to develop hydrogel scaffolds that physicochemically mimic native liver tissue. Furthermore, their in vitro biocompatibility was assessed using preliminary biological tests using HepG2 cells. Both materials were thoroughly physicochemically characterized and benchmarked to the methacrylated gelatin (GelMA) reference material. Due to inferior properties, Dexox-gel was not further processed into 3D-hydrogel scaffolds. This research revealed that DexNB-GelSH exhibited physicochemical properties that were in excellent agreement with the properties of natural liver tissue in contrast to GelMA. In combination with an equally good biological evaluation of DexNB-GelSH in comparison with GelMA based on an MTS proliferation assay and an albumin quantification assay, DexNB-GelSH can be considered promising in the field of liver tissue engineering.

Fabrication of triple-crosslinked gelatin/alginate hydrogels for controlled release applications

Hydrogels have been demonstrated as smart drug carriers to recognize the tumor microenvironment for cancer treatment, where the dynamic crosslinks in the hydrogel network contribute to the stimuli-responsive features but also result in poor stability and weak mechanical property of the hydrogels. Here, phenylboronic acid-grafted polyethyleneimine (PBA-PEI)-modified gelatin (PPG) was synthesized to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds, and then calcium ions (Ca2+) were added to introduce the third calcium-carboxylate crosslinking in the network to form the triple-crosslinked PPG/ADA-Ca2+ hydrogels. Given the three types of dynamic bonds in the network, PPG/ADA-Ca2+ hydrogels possessed a self-healing manner, stimuli-responsiveness, and better mechanical properties compared to single- or double-crosslinked hydrogels. The controlled release capability of PPG/ADA-Ca2+ hydrogels was also demonstrated, showing the encapsulated molecules can be rapidly released from the hydrogel network in the presence of hydrogen peroxide while the release rate can be slowed down at acidic pH. Furthermore, PPG/ADA-Ca2+ hydrogels presented selected cytotoxicity and drug delivery to cancer cells due to the regulated degradation by the cellular microenvironment. Taken together, PPG/ADA-Ca2+ hydrogels have been demonstrated as promising biomaterials with multiple desirable properties and dynamic features to perform controlled molecule release for biomedical applications.

An additive-free multifunctional β-glucan-peptide hydrogel participates in the whole process of bacterial-infected wound healing

Bacterial infections and excessive inflammation can impede the healing of wounds. Hydrogels have emerged as a promising approach for dressing bacterial-infected injuries. However, some antibacterial hydrogels are complex, costly, and even require assistance with other instruments such as light, making them unsuitable for routine outdoor injuries. Here, we developed an in-situ generating hydrogel via hybridizing oxidized β-D-glucan with antimicrobial peptide C8G2 through the Schiff base reaction. This hydrogel is easily accessible and actively contributes to the whole healing process of bacterial-infected wounds, demonstrating remarkable antibacterial activity and biological compatibility. The pH-sensitive reversible imine bond enables the hydrogel to self-heal and sustainably release the antibacterial peptide, thereby improving its bioavailability and reducing toxicity. Meanwhile, the immunoregulating β-D-glucan inhibits the release of inflammatory factors while promoting the release of anti-inflammatory factors. In methicillin-resistant Staphylococcus aureus (MRSA)-infected full-thickness skin wound models, the hybrid hydrogel showed superior antibacterial and anti-inflammatory activity, enhanced the M2 macrophage polarization, expedited wound closure, and regenerated epidermis tissue. These features make this hydrogel an appealing wound dressing for treating multi-drug-resistant bacteria-infected wounds.