Wound Dressing Hydrogel of Enteromorpha prolifera Polysaccharide-Polyacrylamide Composite: A Facile Transformation of Marine Blooming into Biomedical Material

Mechanically enhanced chitosan hydrogels based on micellar cross-linking for wound hemostasis

Excessive blood loss caused by severe trauma is often life-threatening, so a kind of hemostatic material with superior performance is urgently needed to achieve rapid hemostasis of wounds. Here, we prepared CDCS/PF/PVA/Agar hydrogels by blending chitosan modified by catechol groups, PF127-NH2 micelles, PVA and agarose. The hydrogel showed adjustable swelling and degradation properties. The CDCS/PF/PVA/Agar hydrogel exhibited exceptional mechanical properties with an elastic modulus of 351.4 kPa after four freeze-thaw cycles, surpassing traditional polysaccharide hydrogels by 7-20 fold. Its tissue adhesion strength reached 16.24 kPa in air and 11.23 kPa under wet conditions, enabled by catechol-mediated covalent bonding and amino group interactions. In vivo experiments demonstrated rapid hemostasis within 170 s in mouse liver injury models, reducing blood loss by 75.4 % compared to untreated controls. This study provides a robust strategy for designing polysaccharide hydrogels integrating mechanical resilience, rapid hemostasis, antibacterial activity, and biosafety, offering significant potential for clinical wound management.

Fabrication of Janus-adhesion Multifunctional Hydrogel Based on β-cyclodextrin for Wound Dressing

Conventional wound dressings frequently face challenges of insufficient mechanical strength, inadequate adhesion, irregular drug release, and contamination from adherence to extraneous surfaces. These issues can lead to wound contamination and the risk of secondary injuries. In this work, a robust, thermoresponsive wound dressing is developed based on pH/thermal-responsive supramolecular hydrogels, synthesized by integrating N-isopropyl acrylamide, carboxymethyl cellulose, and β-cyclodextrin-grafted poly(acrylic acid). The novel finding is that the hydrogel exhibits a Janus-like adhesion, wherein it adheres stably to the wound while losing adhesion to external environments resulting in reduced accumulation of impurities. The prepared hydrogels can self-heal at low temperatures. It has antioxidant properties and excellent biocompatibility that can continuously and stably release active medicines. In vivo experiments in a rat model of full-thickness skin wounds show that the hydrogels positively accelerate wound healing. The unique physicochemical properties and biological interactions of this multifunctional supramolecular hydrogel provide a promise for advancing wound management by modulating tissue adhesion.

A review of polysaccharide-based hydrogels: From structural modification to biomedical applications

Hydrogels prepared from natural polysaccharide possess excellent biocompatibility and adjustable physical properties similar to those of natural extracellular matrices, and have thus been extensively utilized in the biomedical field. However, natural polysaccharide hydrogels have limited applications owing to their performance deficiencies. For instance, poor mechanical properties restrict their application in tissue engineering, while instability hinders their adaptation to complex and dynamic physiological environments. The chemical modification of polysaccharides and their combination with other matrix materials, such as proteins, synthetic polymers, and inorganic materials, to form hybrid hydrogels have been utilized to enhance the properties of polysaccharide-based hydrogels for diverse applications. This paper reviews comprehensively and systematically the methods of natural polysaccharide modification and describes in detail the various types of polysaccharide-based hydrogels. Additionally, the applications of these hydrogels in drug delivery, wound dressings, tissue engineering and biosensing are summarized. Finally, the challenges and future directions for the application of polysaccharide-based hydrogels are envisioned to provide a reference for the design of novel multifunctional hydrogels.

Development of Mn3O4 nanoparticles and Justicia adhatoda extract incorporated Carboxymethyl cellulose/Carbopol hydrogels: Rheological and in vitro bioactivity for sustained drug delivery system

Hydrogels are widely recognized as promising drug delivery matrices, yet their utility is often limited by challenges such as burst drug release, poor bioavailability, and insufficient mechanical properties. This study aims to overcome these limitations by developing hybrid carboxymethylcellulose (CMC)/Carbopol hydrogels loaded with Mn3O4 nanoparticles and Justicia adhatoda extract, ensuring sustained drug release and enhanced mechanical performance. The synergistic integration of Mn3O4 nanoparticles and Carbopol significantly improved the mechanical strength, reflected by an increase in yield stress from 58 Pa to 76 Pa, and enhanced the thermal stability of the hydrogels, as confirmed by comprehensive rheological analyses. Drug release studies demonstrated controlled, sustained release behavior, following Korsemeyer Peppas model kinetics, effectively minimizing the burst release phenomenon and improving bioavailability. Furthermore, the hydrogels exhibited antioxidant activity (95 ± 0.6 %), substantial biofilm inhibition, and significant anticancer potential, as evidenced by a reduction in skin cancer cell viability to 22.38 ± 0.7 %. These multifunctional properties make the CMC/Carbopol-based hydrogels a promising platform for advanced drug delivery systems, addressing critical challenges while achieving superior therapeutic efficacy.

Functional Wound Dressing Based on Natural Compounds from Traditional Chinese Medicines─Magnolol for Accelerating Wound Healing

Traditional petroleum-based foam dressings offer limitations due to poor biocompatibility, long preparation cycle, and serious environmental pollution. In addition, free small molecules of incomplete polymers and residual toxic cross-linkers pose a threat to the health of patients and hinder the rapid repair of wounds. Recently, natural compounds extracted from plants have gained a lot of interest in the field of wound repair due to their good biocompatibility, biodegradability, and therapeutic effects. In this study, we successfully prepared magnolol-based porous foams by a simple one-pot method using magnolol herbal exhibiting good mechanical properties, hydrophobicity, and biocompatibility, and meets the requirements of wound dressings. The Janus composite dressing was prepared using a magnolol-based porous foam as the inner layer, PVA nonwoven fabric as the middle layer, and polyacrylate as the outer layer. The three-layer structure of magnolol-based porous foam/PVA nonwoven fabric/polyacrylate (MPF/PVA/PAAS) has the capacity to realize unidirectional diversion and rapid water locking of liquid. In vivo experimental data showed that MPF/PVA/PAAS dressing significantly promoted collagen deposition and angiogenesis, and could shorten the wound healing cycle from 14 days to 10 days, significantly accelerating the wound healing process compared to traditional wound dressings. Hence, magnolol-based foam dressings show great application potential in the field of wound treatment.

Robust 3D-Printable, Injectable, and Adhesive Hydrogels with Stepwise-Triggered Dual Reversible/Irreversible Covalent Linkages for Wound Healing

The development of 3D-printable and injectable biocompatible hydrogels with robust mechanical and adhesive properties useful for biomedical applications remains a great challenge. Herein, stepwise-triggered dual reversible/irreversible covalent linkages are engineered between two functionalized polymers, glycidyl methacrylate-modified polyvinyl alcohol (PVA-GMA) and oxidized sodium alginate tailed with 3-aminophenylboronic acid (OSA-PBA), allowing the availability of PVA-GMA/OSA-PBA (PGOP) hydrogels with versatile properties and functions. The PGOP hydrogels have excellent injectability, processability, mechanical strength (39.5 ± 2.3 kPa), self-healing, elasticity and toughness (80% compressive strain at 84.5 kPa stress), bioadhesion (34.2 ± 2.7 kPa adhesive strength to fresh pig skin, vs 7.3-15.38 kPa for commercial fibrin glue adhesives), degradability, antibacterial property, and biocompatibility (265% cell survival with fibroblasts co-culture for 5 d). With these merits, PGOP pregel and hydrogels can be applied as 3D-printing glue and construct materials to produce diverse 3D hierarchical architectures with high shape fidelity, good mechanical properties, and active materials-laden capacity. The mouse liver hemorrhage model and the full-thickness skin defect model demonstrate that PGOP hydrogels have excellent hemostatic ability and accelerated wound healing capacity. Therefore, this work provides 3D-printable and injectable glue and hydrogel adhesives with favorable mechanical strength useful for various biomedical applications such as tissue engineering and wound healing.

Instantaneous Self-Healing Chitosan Hydrogels with Enhanced Drug Leakage Resistance for Infected Stretchable Wounds Healing

Self-healing hydrogels are intelligent wound dressings to repair structural damage caused by limb movement, demonstrating advantages in stretchable wound management. Chitosan is widely used in the preparation of hydrogels due to the biocompatibility and biodegradability. However, the self-healing efficiency and mechanical strength of chitosan hydrogels are not ideal. To address the issues, three self-healing hydrogels: the single schiff base network hydrogels (OH), the double schiff-base bond network hydrogel (OHD), and borate ester bond/schiff base bond (OHPB) are designed. The self-healing time of OHPB is only 0.7 s measured by real-time electrochemical test, while the self-healing time of OH and OHD is 3.5 h and 1.5 h. Furthermore, OHPB hydrogel exhibits the desirable mechanical strength and tissue adhesion. Following the destruction-repair process, CIP and exosome loaded OHPB (ec⊂OHPB) hydrogel displays approximate 100% drug leakage resistance to achieve long-term antibacterial, cells migration promotion and M2 polarization. ec⊂OHPB hydrogel significantly accelerates infected stretchable wounds healing by relieving inflammation, facilitating angiogenesis and collagen deposition, promoting epidermal remodeling. Consequently, OHPB hydrogel with instantaneous self-healing property and enhanced drug leakage resistance performance makes it possible to broaden the application prospects of chitosan hydrogel dressings.

Electrostatically Enhanced Biomimetic Asymmetric Hydrogel with a Dung Beetle-Inspired Pattern for Internal Trauma Sealing

Herein, a biologically asymmetric adhesion-patterned hydrogel induced by the dung beetle surface was proposed for internal trauma sealing. The electrostatic interaction-enhanced dual networks endowed the hydrogel patch with superior mechanical performance, thus achieving a favorable sealing ability. Poly(acrylic acid) (pAA), chitooligosaccharide (COS), and gelatin were used as the composition of our hydrogel system. Concurrently, the bionic raised structure enabled a significant adhesion drop effect. The surface waviness function, fitted to the curved bumps, showed the design direction of the patterned bumps, which was indicative of subsequent research. Also, the microparticle deposition method could exert a synergistic effect with the patterned surface, which together contributed to the asymmetry of the adhesive hydrogel patch. Following simulation experiments such as in vitro bursting tests, we conducted a rat gastric trauma model to validate the application potential of this bionic asymmetric patterned patch. The asymmetric adhesion hydrogel patch had an excellent sealing effect, antiadhesive properties, and operability and was expected to have a promising application prospect, providing a strategy for the design of subsequent in vivo trauma-sealing biomaterials.

Efficient degradation of the polysaccharide extracted from Enteromorpha prolifera by using a novel polysaccharide lyase family 28 enzyme with high activity

The polysaccharides originated from Enteromorpha species exhibited versatile physiological activities and great potential in food and medicine industries. The oligosaccharides, which prepared from polysaccharide by enzymatic hydrolysis, retained the excellent activity as polysaccharide, and then revealed better solubility, bioavailability and effectiveness. However, there are few reports on Enteromorpha polysaccharide (EP)-degrading enzymes for efficient degradation of EP and high-valued utilization of Enteromorpha biomass. Herein, a novel EP-degrading enzyme, EPD1, was identified and heterologously expressed. It could efficiently hydrolyze the EP with high activity (985.755 U/mg) and exhibited optimal activity at 50 °C and a pH of 10.0. The Km value of EPD1 was 7.5512 mg·mL-1 and the Vmax value was 4.9109 μmol·min-1·mL-1. Furthermore, EPD1 demonstrated cold adaptation as evidenced by minimal activity loss following incubation at temperatures below 30 °C for 1 h. HPLC and ESI-MS analysis revealed that EPD1 could produce disaccharides, trisaccharides and tetrasaccharides as the final degradation products from EPs. In conclusion, a novel EP-degrading enzyme with high activity and excellent performance was identified and it can expand the database of EP-degrading enzymes and provide the possibility to make full use of EPs.

Influence of Electrostatic Interactions on the Self-Assembly of Charged Peptides

Peptides can be designed to self-assemble into predefined supramolecular nanostructures, which are then employed as biomaterials in a range of applications, including tissue engineering, drug delivery, and vaccination. However, current self-assembling peptide (SAP) hydrogels exhibit inadequate self-healing capacities and necessitate the use of sophisticated printing apparatus, rendering them unsuitable for 3D printing under physiological conditions. Here, we report a precisely designed charged peptide, Z5, with the object of investigating the impact of electrostatic interactions on the self-assembly and the rheological properties of the resulting hydrogels. This peptide displays salt-triggered self-assembly resulting in the formation of a nanofiber network with a high β-sheet content. The peptide self-assembly and the hydrogel properties can be modified according to the ionic environment. It is noteworthy that the Z5 hydrogel in normal saline (NS) shows exceptional self-healing properties, demonstrating the ability to recover its initial strength in seconds after the removal of shear force, thus rendering it an acceptable material for printing. In contrast, the strong salt shielding effect and the ionic cross-linking of Z5 hydrogels in PBS result in the bundling of peptide nanofibers, which impedes the recovery of the initial strength post-destruction. Furthermore, incorporating materials with varied charging properties into Z5 hydrogels can alter the electrostatic interactions among peptide nanofibers, further modulating the rheological properties and the printability of SAP hydrogels.

Pullulan fermented by Aureobasidium melanogenum TZ-FC3 for the preparation of self-healing, adhesive, injectable and antibacterial pullulan/PVA/borax hydrogel

Natural polymer hydrogels, such as pullulan-based hydrogels, offer significant advantages over synthetic materials due to their thermal stability, film-forming capacity, solubility, adhesiveness, and antioxidant properties. In this study, the strain Aureobasidium melanogenum TZ-FC3, which produces a high level of pullulan, was successfully isolated from the mangrove ecosystems of Guangdong Province, China. 66.01 ± 1.10 g/L pullulan without melanin was produced by the TZ-FC3 strain within 120 h at flask level. Pullulan fermented by A. melanogenum TZ-FC3 was added to enhance the hydrogen bond network within the pullulan/PVA/borax hydrogels (P-2, P-3 and P-4 hydrogels) to improve mechanical strength and crosslinking density of PVA/borax hydrogel (P-1 hydrogel). Compared to the P-1 hydrogel, the P-2 hydrogel exhibited a 65.4 % increase in tensile strain, a remarkable 694.03 % increase in tensile strength and improved the degree of internal crosslinking. Additionally, the pullulan/PVA/borax hydrogels demonstrated excellent self-healing properties, adhesion, injectability, and antibacterial activity. The preparation process of pullulan/PVA/borax hydrogels is straightforward and effective, suggesting broad industrial applicability and underscoring their potential as next-generation materials for advanced healthcare solutions.

Polysaccharide-Based Hydrogels for Advanced Biomedical Engineering Applications

In recent years, numerous applications of hydrogels using polysaccharides have evolved, benefiting from their widespread availability, excellent biodegradability, biocompatibility, and nonpoisonous nature. These natural polymers are typically sourced from renewable materials or from manufacturing processes, contributing collaboratively to waste management and demonstrating the potential for enhanced and enduring sustainability. In the field of novel bioactive molecule carriers for biotherapeutics, natural polymers are attracting attention due to their inherent properties and adaptable chemical structures. These polymers offer versatile matrices with a range of architectures and mechanical properties, while retaining the bioactivity of incorporated biomolecules. However, conventional polysaccharide-based hydrogels suffer from inadequate mechanical toughness with large swelling properties, which prohibit their efficacy in real-world applications. This review offers insights into the latest advancements in the development of diverse polysaccharide-based hydrogels for biotherapeutic administrations, either standalone or in conjunction with other polymers or drug delivery systems, in the pharmaceutical and biomedical fields.

Water-soluble polysaccharides extracted from Enteromorpha prolifera/PVA composite film functionalized as ε-polylysine with improved mechanical and antibacterial properties

The issue of environmental protection has received sustained and widespread attention. In order to reduce environmental pollution related to traditional plastics, it is an incessant demand to design novel environment-friendly food packaging materials with excellent performance. Sulfated polysaccharide extracted from the "green tide" marine pollution Enteromorpha prolifera (SPE) has been innovatively transformed into a film-forming material for better utilization. The insufficient mechanical properties and limited functionalities, however, hinder its wide application. In this study, polyvinyl alcohol (PVA) was blended to enhance its mechanical properties and ε-polylysine (ε-PL) was incorporated to endow it with antimicrobial performance. A novel and biodegradable film composed of SPE, PVA, and ε-PL was fabricated by casting method. We further determined the physicochemical properties of composited films. Mechanical performance test revealed the tensile strength of SPE-PVA-PL films increased from 5.56 MPa to 6.65 MPa and the E% increased from 128.8 % to 246.9 % compared with that of SPE-PVA films. Antimicrobial tests showed the excellent antibacterial activity of SPE-PVA-PL films against representative microbial species, Staphylococcus aureus and Escherichia coli. The results of this study suggested that the SPE-based composite film has the potential to be used as a potential food packaging and wound dressing materials.

Effects of Enteromorpha prolifera sulfated polysaccharide and aluminium ion addition on the multifunctional property of conductive hydrogel for wearable strain sensing

Although introducing Enteromorpha prolifera sulfated polysaccharide (SPEP) enhances the mechanical properties of hydrogels significantly, little is known about the effects of polysaccharide and ion addition on morphological and physicochemical properties of conductive hydrogel. Therefore, the Poly (acrylic acid)/SPEPn/Al3+m (PAA/SPEPn/Al3+m) hydrogels with different SPEP and Al3+ addition were synthesized by simple one-pot method. The porosity, tensile strength, and swelling ration increased, while compressive strength, elongation at break, self-healing, self-adhesion properties increased first and then decreased as SPEP addition increased from 0 % to 3.80 %. The Al3+ addition increased from 0.08 % to 0.30 %, both tensile and compressive strength increased first and then decreased, while elongation at break kept increasing. Unexpectedly, both increasing SPEP and Al3+ addition reduced the electrical conductivity, while SPEP increased the gauge factor of hydrogel. The hydrogel exhibited optimal comprehensive properties when SPEP and Al3+ addition were 2.31 % and 0.24 %, respectively. The PAA/SPEP2.31%/Al3+0.24% hydrogel showed high tensile strength (107.60 kPa), elongation at break (2426.67 %), strain self-healing rate (81.87 %), adhesion strength (21.61 kPa), and conductivity (3.60 S/m). Overall, the properties of PAA/SPEPn/Al3+m hydrogels can be regulated through tailoring SPEP and Al3+ addition, which can be used as on-demand strategy to improve the performance of PAA/SPEPn/Al3+m hydrogels for each application.

Polysaccharides and oligosaccharides originated from green algae: structure, extraction, purification, activity and applications

With the proceeding of global warming and water eutrophication, the phenomenon of green tide has garnered significant societal interest. Consequently, researchers had increasingly focused on the potential applications of green algae biomass, particularly its polysaccharides. The polysaccharide serves as the primary active constituent of green algae and has demonstrated numerous advantageous biological activities, including antioxidant, antiviral, anticoagulant, hypolipidemic and immuno-modulatory activities. The favorable bioavailability and solubility of green algae oligosaccharides are attributed to their low molecular weight. So there has been a growing interest in researching green algae polysaccharides and oligosaccharides for the utilization of marine biological resources. This review summarized the extraction, purification, chemical structure, composition, biological activity, and potential applications prospect of polysaccharides and oligosaccharides derived from green algae. The review could be helpful for expanding the applications of polysaccharides and oligosaccharides of green algae.

Extraction, Characterisation and Evaluation of Antioxidant and Probiotic Growth Potential of Water-Soluble Polysaccharides from Ulva rigida Macroalgae

Ulva rigida green macroalgae contain a variety of polysaccharides. A recent study investigated the optimum concentration and yield of polysaccharide extraction from oven-dried U. rigida biomass using a water-soluble polysaccharide extraction method that adhered to safety standards. This study utilised complete factorial experiments to examine the effects of varying factors on polysaccharide extraction. Results showed a positive correlation between increased levels of all factors and higher polysaccharide extraction yield. This study also found that the main factors and their interaction had a significant impact on the extracted polysaccharides from U. rigida. The highest polysaccharide content and yield were 9.5 mg/mL and 189 mg/g, respectively. Water-soluble polysaccharides demonstrated the presence of reducing sugar (8 mg/g), phenolics (0.69 mg/g) and flavonoids (1.42 mg/g) and exhibited antioxidant properties. Results revealed that freeze-dried polysaccharide powders were primarily composed of the monosaccharide rhamnose. Preliminary results on the effect of these powders on probiotics demonstrated that supplementation of polysaccharides from U. rigida promoted viable Lactobacillus rhamnosus ATCC 53103 growth during cultivation. This discovery has the potential to revolutionise the human food industry and promote the development of functional ingredients for novel and future food products, with numerous applications in the nutraceutical and pharmaceutical industries.

In-situ electrospinning with precise deposition of antioxidant nanofiber facial mask loaded with Enteromorpha prolifera polysaccharides

In order to fabricate a novel antioxidant nanofiber facial mask, a metal cone modified in-situ electrospinning with precise deposition was employed by utilizing Enteromorpha prolifera polysaccharides (EPPs). The metal cone could control the deposition area to achieve precise fabrication of facial mask on skin. The EPPs exhibited remarkable antioxidant ability, as evidenced by the half-maximal inhibitory concentrations (IC50) of 1.44 mg/mL and 0.74 mg/mL against DPPH and HO• free radicals, respectively. The antioxidant ability of the facial mask was improved by elevating the electrospinning voltage from 15 kV to 19 kV, due to the improved release capacity of EPPs by 7.09 %. Moreover, the facial mask demonstrated robust skin adhesion and moisture-retaining properties compared with commercial facial mask, which was benefited by the in-situ electrospinning technology. Furthermore, cytotoxicity assay, animal skin irritation test, and ocular irritation test collectively affirmed the safety of the facial mask. Thus, this research introduces a novel in situ electrospinning with precise deposition method and a natural antioxidant additive for preparing facial mask.

Bioinspired Zn-MOF doped radial porous chitosan-based sponge with antibacterial and antioxidant properties for rapid hemostasis and wound healing

Herein, a novel bioinspired radial porous zinc-based metal-organic framework (Zn-MOF) doped sodium alginate/chitosan derivatives/pullulan-based SA/PSCS/Pul/Zn-MOF (SPCP/Zn) composites sponge with excellent antioxidant and antibacterial properties was fabricated by the ice-templating method. Boric acid (BA) and Ca2+, which were respectively used as hydrogen- and ionic- bonding cross-linkers, provided strong mechanical properties for sponge matrix composed of SA, PSCS, and Pul. The obtained SPCP/Zn sponge exhibited uniform porous morphology, proper hydrophilicity, and admirable biocompatibility. In addition, the SPCP/Zn sponge achieved a sustained release of Zn2+ and gallic acid, which displayed powerful antibacterial and antioxidant activities. Importantly, the SPCP/Zn sponge exhibited shorter rapid hemostasis (20.4 ± 2.9 s) and lower blood loss (19.8 ± 4.3 mg). The SPCP/Zn sponge also showed faster wound closure ratio for the rat full-thickness skin defect model. It was revealed that SPCP/Zn sponge could significantly accelerate and enhance wound healing through downregulating inflammatory cytokines (TNF-α, IL-6) and increasing the expression of growth factors (VEGF). Due to its excellent properties, the SPCP/Zn sponge may have promising potential in wound healing applications.

Structure-activity relationships of bioactive polysaccharides extracted from macroalgae towards biomedical application: A review

Macroalgae are valuable and structurally diverse sources of bioactive compounds among marine resources. The cell walls of macroalgae are rich in polysaccharides which exhibit a wide range of biological activities, such as anticoagulant, antioxidant, antiviral, anti-inflammatory, immunomodulatory, and antitumor activities. Macroalgae polysaccharides (MPs) have been recognized as one of the most promising candidates in the biomedical field. However, the structure-activity relationships of bioactive polysaccharides extracted from macroalgae are complex and influenced by various factors. A clear understanding of these relationships is indeed critical in developing effective biomedical applications with MPs. In line with these challenges and knowledge gaps, this paper summarized the structural characteristics of marine MPs from different sources and relevant functional and bioactive properties and particularly highlighted those essential effects of the structure-bioactivity relationships presented in biomedical applications. This review not only focused on elucidating a particular action mechanism of MPs, but also intended to identify a novel or potential application of these valued compounds in the biomedical field in terms of their structural characteristics. In the last, the challenges and prospects of MPs in structure-bioactivity elucidation were further discussed and predicted, where they were emphasized on exploring modern biotechnology approaches potentially applied to expand their promising biomedical applications.

Self-healing, ultra-stretchable, and highly sensitive conductive hydrogel reinforced by sulfate polysaccharide from Enteromorpha prolifera for human motion sensing

The synthesis of multifunctional conductive hydrogel has attracted extensive attention worldwide due to their integrated properties of stretchability, self-adhesion, self-healing, and high sensitivity, while it is still a challenge. Although various kinds of polysaccharides and their derivatives are used to achieve the aforementioned objective, there are few researches about hydrogel design introducing sulfated polysaccharide from Enteromorpha prolifera (SPE), which is rich in hydroxyl, sulfate, and carboxyl groups providing amounts of reaction sites for hydrogel synthesis. Herein, conductive hydrogel (PAA-Al3+-SPE3) reinforced by SPE was designed by simple one pot hot polymerization method. This hydrogel demonstrated charming extension ratio (up to 4027.40 %), strain stress (up to 59.94 kPa), compressive strength (19.71 Mpa), and high conductivity sensibility (GF 6.76, 300 % - 700 %). Additionally, PAA-Al3+-SPE3 showed good self-healing property (repaired autonomously after 60 s) and satisfied self-adhesion (31.11 kPa) due to the reversible hydrogen bonds and metal coordination interactions. Furthermore, the PAA-Al3+-SPE3 hydrogel showed great real-time sensing performance to monitor various motions. These findings suggest the potential of PAA-Al3+-SPE3 hydrogel as an affordable and reliable conductive sensing material. Meantime, the first utilization of SPE to construct flexible wearable sensors offers new route for the high-value application of Enteromorpha prolifera.

A novel antibacterial hydrogel based on thiolated ovalbumin/gelatin with silver ions to promote wound healing in mice

Hydrogels could be used as wound dressings, but most protein-based hydrogels lack anti-bacterial effects. Here, we successfully prepared a silver ion cross-linked thiolated protein hydrogel (thiolated Ovalbumin and Gelatin, O3G7). The wound photographs showed that the healing rate (96.23 %) of hydrogel-treated mice was higher than the control group. Meanwhile, the hydrogel increased the granulation tissue's total protein content. Furthermore, it significantly increased the collagen content, consistent with the results of Masson's trichrome (MT) staining and immunohistochemical analysis of type I collagen (ColI). The results of hematoxylin and eosin (H&E) staining showed the growth and proliferation of inflammatory cells, granulation tissue, fibroblasts, blood vessels and hair follicles in acute wounds. O3G7 hydrogel had fewer inflammatory cells and more neovascularization, and hair follicle tissue and intact epidermis could be observed. The results of immunofluorescence and immunohistochemistry showed that the O3G7 group reduced the expression of tumor necrosis factor (TNF)-α (56.87 % of the control group) and upregulated the expression of transforming growth factor (TGF)-β (1.29 times of the control group). These results suggest that O3G7 hydrogel significantly affects the healing of acute wounds. This study demonstrates that hydrogels prepared from food-derived proteins will be promising and bio-safe candidates in bioengineering.

A temperature and pH dual-responsive injectable self-healing hydrogel prepared by chitosan oligosaccharide and aldehyde hyaluronic acid for promoting diabetic foot ulcer healing

Chronic wound, such as skin defect after burn, pressure ulcer, and diabetic foot ulcer is very difficult to cure. Its pathological process is often accompanied with local temperature rise, pH decrease, and other phenomena. Owing to their outstanding hydrophilic, biocompatibility, and responsive properties, hydrogels could accelerate the healing process. In this study, we chose chitosan oligosaccharide (COS) grafted with Pluronic F127 (F127-COS). Aldehyde hyaluronic acid (A-HA) oxidized by NaIO4. And added boric acid (BA) to prepare a thermosensitive and pH-responsive injectable self-healing F127-COS/A-HA/COS/BA (FCAB) hydrogel, loaded with drug deferoxamine (DFO) in order to have an accurate release and promote angiogenesis of diabetic foot ulcer. In vitro experiments had verified that the FCAB hydrogel system loaded with DFO (FCAB/D) could promote migration and angiogenesis of HUVEC. A diabetes rat back wound model further confirmed its role in promoting angiogenesis in wound repair process. The results showed that the FCAB/D hydrogel exhibited unique physicochemical properties, excellent biocompatibility, and significantly enhanced therapeutic effects for diabetic foot ulcer.

Surprising Nanomechanical and Conformational Transition of Neutral Polyacrylamide in Monovalent Saline Solutions

Polyacrylamide (PAM) is one of the most important water-soluble polymers that has been extensively applied in water treatment, drug delivery, and flexible electronic devices. The basic properties, e.g., microstructure, nanomechanics, and solubility, are deeply involved in the performance of PAM materials. Current research has paid more attention to the development and expansion of the macroscopic properties of PAM materials, and the study of the mechanism involved with the roles of water and ions on the properties of PAM is insufficient, especially for the behaviors of neutral amide side groups. In this study, single molecule force spectroscopy was combined with molecular dynamic (MD) simulations, atomic force microscope imaging, and dynamic light scattering to investigate the effects of monovalent ions on the nanomechanics and molecular conformations of neutral PAM (NPAM). These results show that the single-molecule elasticity and conformation of NPAM exhibit huge variation in different monovalent salt solutions. NPAM adopts an extended conformation in aqueous solutions of strong hydrated ion (acetate), while transforms into a collapse globule in the existence of weakly hydrated ion (SCN-). It is believed that the competition between intramolecular and intermolecular weak interactions plays a key role to adjust the molecular conformation and elasticity of NPAM. The competition can be largely influenced by the type of monovalent ions through hydration or a chaotropic effect. Methods utilized in this study provide a means to better understand the Hofmeister effect of ions on other macromolecules containing amide groups at the single-molecule level.

One-Pot Preparation of Skin-Inspired Multifunctional Hybrid Hydrogel with Robust Wound Healing Capacity

Bioinspired hydrogels have demonstrated multiple superiorities over traditional wound dressings for wound healing applications. However, the fabrication of bioinspired hydrogel-based wound dressings with desired functionalities always requires multiple successive steps, time-consuming processes, and/or sophisticated protocols, plaguing their clinical applications. Here, a facile one-pot strategy is developed to prepare a skin-inspired multifunctional hydrogel within 30 min by incorporating elastin (an essential functional component of the dermal extracellular matrix), tannic acid, and chitosan into the covalently cross-linked poly(acrylamide) network through noncovalent interactions. The resulting hydrogel exhibits a Young's modulus (ca. 36 kPa) comparable to that of human skin, a high elongation-at-break (ca. 1550%), a satisfactory tensile strength (ca. 61 kPa), and excellent elastic self-restorability, enabling the hydrogel to synchronously and conformally deform with human skin when used as wound dressings. Importantly, the hydrogel displays a self-adhesive property to skin tissues with an appropriate bonding strength (ca. 55 kPa measured on intact porcine skin), endowing the hydrogel with the ability to rapidly self-adhere to intact human skin, sealing the wound surface and also easily being removed without residue left or trauma caused to the skin. The hydrogel also possesses remarkable antibacterial activity, antioxidant capability, and hemocompatibility. All of these collective beneficial properties enable the hydrogel to significantly accelerate the wound healing process, outperforming the commercial wound dressings.

Photodynamic Alginate Zn-MOF Thermosensitive Hydrogel for Accelerated Healing of Infected Wounds

Antibiotic resistance reduces the effectiveness of infected wound healing, and it is necessary to develop a new strategy to promote infected wound healing without using antibiotics. Here, we develop a Chlorin e6 (Ce6)-loaded zinc-metal-organic framework (MOF) thermosensitive hydrogel (Ce6@MOF-Gel) based on alginate and poly(propylene glycol) 407, which enhances antibacterial effects and promotes infected wound healing by a novel strategy of combining zinc-MOF with photodynamic therapy (PDT). Zinc-MOF can realize acid-responsive release of Ce6 and improve antibacterial performance without drug resistance by destroying the integrity of bacterial cell membranes and enhancing the production of bacterial reactive oxygen species (ROS). Additionally, Ce6@MOF-Gel enhances the stability, solubility, and photodynamic properties of Ce6. More importantly, Ce6@MOF-Gel reduces inflammation and promotes collagen deposition and re-epithelialization to facilitate infected wound healing. Collectively, the photodynamic MOF-based hydrogel provides a new, efficient, and safe way for accelerated healing of infected wounds.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Nanomedicine hybrid and catechol functionalized chitosan as pH-responsive multi-function hydrogel to efficiently promote infection wound healing

The complicated wound repair process caused by microbial infection is still a clinical problem due to antibiotic resistance. Therefore it is necessary to employ the incorporating bioactive molecules in the dressing to solve this problem. Herein, a multifunctional nanocomposite hydrogel (CS-HCA-Icps) with the pathological pH-responsive drug release has been developed to promote the infection-impaired wound healing. CS-HCA-Icps nanocomposite hydrogel composed of catechol-grafted chitosan (CS-HCA) and a curcumin-Fe³⁺ coordination nanoparticles (Icps, CurFe³⁺) exhibits the favorable activities in free radical scavenging, anti-bacterial and anti-inflammatory. The favorable biocompatibility is also demonstrated both in vitro and in vivo experiments. These demonstrate the promoting efficacy of hydrogel in wound healing. In this study, Chitosan (CS) shows excellent biocompatibility and antibacterial properties for tissue repair. After functional modification with HCA, the catechol groups are beneficial to improve antioxidant capacity for wound repair, Moreover, Icps nanomedicine are able to enhance the loaded Cur release in response to the pathological acidic microenvironment at the inflammatory stage of wounds. Thus, the pathological pH-responsive hydrogel integrating anti-bacterial, antioxidant, and anti-inflammatory functions may represent a promising strategy for safe and efficient wound healing, in particular for potential clinical use.

Quarternized chitosan/quercetin/polyacrylamide semi-interpenetrating network hydrogel with recoverability, toughness and antibacterial properties for wound healing

Antibiotic abuse has posed enormous burdens on patients and healthcare systems. Hence, the design and development of non-antibiotic wound dressings to meet clinical demand are urgently desired. However, there remains one of the impediments to hydrogel wound dressings that integrated with good recoverability, toughness, and excellent antibacterial properties. Herein, a series of semi-interpenetrating network (semi-IPN) hydrogels with exceptional mechanical performance and remarkable antibacterial activity based on quaternized chitosan (QCS) and polyacrylamide (PAM) were developed using a one-pot method. Additionally, the antibacterial activity of semi-IPN hydrogel against S. aureus and E. coli was enhanced by integrating it with quercetin (QT). The semi-IPN hydrogels also exhibited high recoverability and toughness, outstanding liquid absorbability (the swelling ratio reached 565 ± 12 %), and a satisfying water vapor transmission rate. Moreover, the semi-IPN hydrogels presented ideal hemocompatibility and cytocompatibility. These high-elastic hydrogels are promising candidates for potential applications in wound dressing, tissue repair, chronic wound care, as well as other biomedical fields.

A UV-induced self-reinforced hydrogel based on in situ hydrophobic aggregation of strained 1,2-dithiolane rings

A novel responsive hydrogel exhibiting self-reinforcement and self-healing capacity was developed based on the hydrophobic aggregation of strained 1,2-dithiolane rings. Oligomerization of 1,2-dithiolane within hydrophobic domains under UV irradiation not only reinforced the hydrogel but also maintained its dynamic cross-linked nature by converting the intraring dynamic S-S bond to an outer one.

Bilayer hydrogel dressing with lysozyme-enhanced photothermal therapy for biofilm eradication and accelerated chronic wound repair

Biofilms are closely associated with the tough healing and dysfunctional inflammation of chronic wounds. Photothermal therapy (PTT) emerged as a suitable alternative which could destroy the structure of biofilms with local physical heat. However, the efficacy of PTT is limited because the excessive hyperthermia could damage surrounding tissues. Besides, the difficult reserve and delivery of photothermal agents makes PTT hard to eradicate biofilms as expectation. Herein, we present a GelMA-EGF/Gelatin-MPDA-LZM bilayer hydrogel dressing to perform lysozyme-enhanced PTT for biofilms eradication and a further acceleration to the repair of chronic wounds. Gelatin was used as inner layer hydrogel to reserve lysozyme (LZM) loaded mesoporous polydopamine (MPDA) (MPDA-LZM) nanoparticles, which could rapidly liquefy while temperature rising so as to achieve a bulk release of nanoparticles. MPDA-LZM nanoparticles serve as photothermal agents with antibacterial capability, could deeply penetrate and destroy biofilms. In addition, the outer layer hydrogel consisted of gelatin methacryloyl (GelMA) and epidermal growth factor (EGF) promoted wound healing and tissue regeneration. It displayed remarkable efficacy on alleviating infection and accelerating wound healing in vivo. Overall, the innovative therapeutic strategy we came up with has significant effect on biofilms eradication and shows promising application in promoting the repair of clinical chronic wounds.

Antioxidant Activities of Natural Polysaccharides and Their Derivatives for Biomedical and Medicinal Applications

Many chronic diseases such as Alzheimer's disease, diabetes, and cardiovascular diseases are closely related to in vivo oxidative stress caused by excessive reactive oxygen species (ROS). Natural polysaccharides, as a kind of biomacromolecule with good biocompatibility, have been widely used in biomedical and medicinal applications due to their superior antioxidant properties. In this review, scientometric analysis of the highly cited papers in the Web of Science (WOS) database finds that antioxidant activity is the most widely studied and popular among pharmacological effects of natural polysaccharides. The antioxidant mechanisms of natural polysaccharides mainly contain the regulation of signal transduction pathways, the activation of enzymes, and the scavenging of free radicals. We continuously discuss the antioxidant activities of natural polysaccharides and their derivatives. At the same time, we summarize their applications in the field of pharmaceutics/drug delivery, tissue engineering, and antimicrobial food additives/packaging materials. Overall, this review provides up-to-date information for the further development and application of natural polysaccharides with antioxidant activities.

Rapid In Situ Deposition of Iron-Chelated Polydopamine Coating on the Polyacrylamide Hydrogel Dressings for Combined Photothermal and Chemodynamic Therapy of Skin Wound Infection

Pathogenic bacterial infections of skin wounds have caused a significant threat to clinical treatment and human life safety. Here, we develop a bactericidal hydrogel dressing consisting of a polyacrylamide (PAM) hydrogel framework with in situ surface-deposition of iron-dopped polydopamine (FePDA). The prepared hydrogel dressing (FePDA-PAM) has a compact surface, good tensile strength, and excellent elastic recovery ability. The introduction of Fe3+ ions improve the photothermal therapy (PTT) efficiency of the PDA and endow the hydrogel dressing with chemodynamic therapy (CDT) properties. In vitro experiments show that the antibacterial effect of FePDA-PAM hydrogel on Staphylococcus aureus reach nearly 100% under the combined action of H2O2 and 808 nm near-infrared (NIR) laser, indicating an excellent combined antibacterial property of PTT and CDT. Furthermore, the FePDA-PAM + H2O2 + NIR treatment group in the in vivo antibacterial experiments displays lowest relative wound area and optimal wound healing within 5 days of treatment, thereby indicating the intensive skin wound disinfection. To summarize, the FePDA-PAM hydrogel has simple preparation and good biosafety. It may serve as a potential wound dressing for the combined PTT/CDT dual-mode antibacterial therapy.

Molecular Dynamics-Assisted Design of High Temperature-Resistant Polyacrylamide/Poloxamer Interpenetrating Network Hydrogels

Polyacrylamide has promising applications in a wide variety of fields. However, conventional polyacrylamide is prone to hydrolysis and thermal degradation under high temperature conditions, resulting in a decrease in solution viscosity with increasing temperature, which limits its practical effect. Herein, combining molecular dynamics and practical experiments, we explored a facile and fast mixing strategy to enhance the thermal stability of polyacrylamide by adding common poloxamers to form the interpenetrating network hydrogel. The blending model of three synthetic polyacrylamides (cationic, anionic, and nonionic) and poloxamers was first established, and then the interaction process between them was simulated by all-atom molecular dynamics. In the results, it was found that the hydrogen bonding between the amide groups on all polymers and the oxygen-containing groups (ether and hydroxyl groups) on poloxamers is very strong, which may be the key to improve the high temperature resistance of the hydrogel. Subsequent rheological tests also showed that poloxamers can indeed significantly improve the stability and viscosity of nonionic polyacrylamide containing only amide groups at high temperatures and can maintain a high viscosity of 3550 mPa·S at 80 °C. Transmission electron microscopy further showed that the nonionic polyacrylamide/poloxamer mixture further formed an interpenetrating network structure. In addition, the Fourier transform infrared test also proved the existence of strong hydrogen bonding between the two polymers. This work provides a useful idea for improving the properties of polyacrylamide, especially for the design of high temperature materials for physical blending.

Multifunctional hydrogels for wound dressings using xanthan gum and polyacrylamide

Developing advanced dressings that integrate multiple functions is one of the major challenges in current clinical wound treatment. In this study, Xanthan gum (XG) and polyacrylamide (PAAm) materials were used to prepare hydrogel dressings by one-pot method. With the combination of the PAAm network and the XG network, the PAAm-XG hydrogels showed the tensile strength of 0.36 MPa and the stretchability as large as 2078 %. The prepared PAAm-XG hydrogels had excellent water uptake efficiency with the swelling ratio of 1200 %. Besides, the developed dressings possessed outstanding biocompatibility, universal adhesion and self-healing ability. More importantly, the PAAm-XG hydrogels can be successfully loaded with Cefixime and human recombinant epidermal growth factor, and these loaded hydrogels released these bioactive molecules in sustained ways. As a result, both E. coli and S. aureus bacteria were inactivated after contacting with the Cefixime-loaded hydrogels for 24 h. Furthermore, in vivo data demonstrated that the PAAm-XG hydrogel dressings significantly accelerated the wound healing in a mouse model. All of these indicate that the multifunctional PAAm-XG hydrogels are promising candidates for wound treatment.

Enteromorpha cellulose micro-nanofibrils/poly(vinyl alcohol) based composite films with excellent hydrophilic, mechanical properties and improved thermal stability

This study presents the preparation of cellulose micro-nanofibrils (CMNFs) from Enteromorpha (EP) and the application in PVA/acetylated distarch phosphate (ADSP)/CMNFs composite films. The Micro-nano scale, hydrophilicity, and strong hydrogen bond characteristics of CMNFs prepared form EP by acid hydrolysis were confirmed through the granular statistics, XRD analysis and chemical structure analysis. With the addition of CMNFs, the ultimate tensile strength and elongation at break of composite films are increased by 42.4 % and 90.3 %. An original Weibull statistical analysis shows the impact of CMNFs' added amount on strength distribution and ultimate stress. SEM and polarizing microscope images show the CMNFs' dispersion state in that films is optimal, when their addition was to be 2 %-3 % of total dry weight of PVA/ADSP matrix， which is consistent with the results of Weibull modulus analysis. The main thermal weight-loss process of the composite film is divided into four stages, CMNFs can significantly increase the thermostability at 280 °C to 400 °C. The experiment of water contact angle and water vapor transmission rate of the composite films confirmed that CMNFs can improve films' hydrophilicity. This study provides basis for the preparation of hydrophilic CMNFs and mechanism of modification study PVA-based composites.

Casein micelles embedded composite organohydrogel as potential wound dressing

Excellent mechanical and tissue adhesive properties, long-lasting environmental suitability and reliable biocompatibility are essential factors for the hydrogels to be applied as wound dressing in the clinical fields. Based on the self-assembly micelle structures, a new type of casein micelles (CEs)/polyvinyl alcohol (PVA) GW (glycerol-water) organohydrogel was designed and synthesized by a simple one-pot method. Through a unique "load sharing" effect, the CEs which own suitable adhesion abilities and drug loading capacities simultaneously were embedded into the PVA networks by rich hydrogen bonds, so that to obtain the composite organ hydrogel with not only excellent adhesive abilities, but also enhanced mechanical properties. Benefited from the unique GW binary solvent system, the organohydrogel showed long-lasting moisture lock-in capacity and extreme temperature tolerance (in the range of --20 °C ~ 60 °C). Particularly, after loading the model antibacterial drugs (allicin) within the CEs, the as-developed CEs/PVA GW gel exhibited a prominent long-lasting (>100 h) antibacterial properties (>90%). Furthermore, the organohydrogel was confirmed with prominent biocompatibility to support fibroblast cell proliferation and migration. This work proposed a new strategy to build CEs-based gel system, which have a great potential application in terms of prevent bacterial infection, accelerate tissue proliferation and wound healing.

Investigation of construction and characterization of carboxymethyl chitosan - sodium alginate nanoparticles to stabilize Pickering emulsion hydrogels for curcumin encapsulation and accelerating wound healing

Limitations in compatibility and effectiveness in delivering bioactive compounds often make it prohibitively difficult to apply Pickering emulsions in wound dressing. In this research, we prepared Pickering emulsion composite hydrogels based on carboxymethyl chitosan - sodium alginate (CMCS-SA) nanoparticles (NPs) stabilized Pickering emulsions, poloxamer 407 (PLX), and curcumin (CUR). CMCS-SA NPs were prepared and used to stabilize Pickering emulsion. The stability of Pickering emulsion improved with the increase of the concentration of NPs, and was highly sensitive to ionic strength change. This Pickering emulsion remained stable at various temperatures. After curcumin were introduced into the emulsion, 0.6% CMCS-SA NPs Pickering emulsion showed controlled release of curcumin in vitro. The CMCS-SA-PLX-CUR hydrogels also exhibited smooth surface and dense structure. This composite hydrogels has antibacterial properties against Escherichia coli and Staphylococcus aureus. Moreover, the CMCS-SA-PLX-CUR hydrogels improved wound healing and increased expression of Ki67 and CD31. RT-qPCR results indicated that the mRNA levels of α-SMA and TGF-β1 in the CMCS-SA-PLX-CUR group were downregulated, while the mRNA levels of TGF-β3 increased. The present study suggests that the potentials of CMCS-SA-PLX-CUR hydrogels are promising in protecting bioactive components and wound care management.

Preparation of aloe polysaccharide/honey/PVA composite hydrogel: Antibacterial activity and promoting wound healing

Maintaining a moist and sterile environment is conducive to accelerating wound healing. To develop a natural wound dressing with good water retention capacity and antibacterial activity, we prepared a novel natural multifunctional hydrogel for infected wound healing, which combines the advantages of Aloe polysaccharide (AP) and honey. AP was extracted from Aloe barbadensis, and its structure was characterized by fourier transform infra-red (FT-IR) spectoscopy and nuclear magnetic resonance (NMR) spectroscopy. AP is an acetylated mannan composed of (1 → 4)β-Manp, which is acetylated at C-2, C-3 and C-6 positions. AP/Honey@PVA hydrogel was prepared by cross-linking AP, honey, PVA with borax, which has good mechanical strength and excellent biocompatibility for blood cells, NIH-3T3 cells and L929 cells. The hydrogels showed significant inhibitory effect on Staphylococcus aureus, Escherichia coli and Candida albicans, as well as accelerated the healing of infected full-thickness wound. This study reveals the structure of AP and proves that AP and honey composite hydrogel has potential application prospect in the therapy of infected wounds.

Marine Polysaccharides in Tailor- Made Drug Delivery

Abstract:

Marine sources have attracted much interest as an emerging source of biomaterials in drug delivery applications. Amongst all other marine biopolymers, polysaccharides have been the mostly investigated class of biomaterials. The low cytotoxic behavior, in combination with the newly explored health benefits of marine polysaccharides has made it one of the prime research areas in the pharmaceutical and biomedical fields. In this review, we focused on all available marine polysaccharides, including their classification based on biological sources. The applications of several marine polysaccharides in recent years for tissue-specific novel drug delivery including gastrointestinal, brain tissue, transdermal, ocular, liver, and lung have also been discussed here. The abundant availability in nature, cost-effective extraction, and purification process along with a favorable biodegradable profile will encourage researchers to continue investigating marine polysaccharides for exploring newer applications in targeting specific delivery of therapeutics.

Ulva (Enteromorpha) Polysaccharides and Oligosaccharides: A Potential Functional Food Source from Green-Tide-Forming Macroalgae

The high-valued utilization of Ulva (previously known as Enteromorpha) bioresources has drawn increasing attention due to the periodic blooms of world-wide green tide. The polysaccharide is the main functional component of Ulva and exhibits various physiological activities. The Ulva oligosaccharide as the degradation product of polysaccharide not only possesses some obvious activities, but also possesses excellent solubility and bioavailability. Both Ulva polysaccharides and oligosaccharides hold promising potential in the food industry as new functional foods or food additives. Studies on Ulva polysaccharides and oligosaccharides are increasing and have been the focus of the marine bioresources field. However, the comprehensive review of this topic is still rare and do not cover the recent advances of the structure, isolation, preparation, activity and applications of Ulva polysaccharides and oligosaccharides. This review systematically summarizes and discusses the recent advances of chemical composition, extraction, purification, structure, and activity of Ulva polysaccharides as well as oligosaccharides. In addition, the potential applications as new functional food and food additives have also been considered, and these will definitely expand the applications of Ulva oligosaccharides in the food and medical fields.

Wound Microenvironment-Responsive Protein Hydrogel Drug-Loaded System with Accelerating Healing and Antibacterial Property

Growth factors play a vital role in wound healing, and novel hydrogel carriers suitable for growth factors have always been a research hotspot in the wound healthcare field. In this work, a wound microenvironment-responsive hydrogel drug-loading system was constructed by cross-linking of the internal electron-deficient polyester and bovine serum albumin (BSA) via catalyst-free amino-yne bioconjugation. The slightly acidic microenvironment of wound tissues induces the charge removal of BSA chains, thus releasing the basic fibroblast growth factor (bFGF) loaded through electrostatic action. Besides, the BSA chains in the gel network further endow their excellent biocompatibility and biodegradability, also making them more suitable for bFGF loading. The wound caring evaluation of the hydrogel in the full-thickness skin wound indicated that the protein-based hydrogel significantly promotes the proliferation and differentiation of fibroblasts, collagen accumulation, and epidermal layer stacking, thus significantly shortening the healing process. This strategy paved the way for broadening the application of the growth factors in the wound care field.

Supramolecular Adhesive Hydrogels for Tissue Engineering Applications

Tissue engineering is a promising and revolutionary strategy to treat patients who suffer the loss or failure of an organ or tissue, with the aim to restore the dysfunctional tissues and enhance life expectancy. Supramolecular adhesive hydrogels are emerging as appealing materials for tissue engineering applications owing to their favorable attributes such as tailorable structure, inherent flexibility, excellent biocompatibility, near-physiological environment, dynamic mechanical strength, and particularly attractive self-adhesiveness. In this review, the key design principles and various supramolecular strategies to construct adhesive hydrogels are comprehensively summarized. Thereafter, the recent research progress regarding their tissue engineering applications, including primarily dermal tissue repair, muscle tissue repair, bone tissue repair, neural tissue repair, vascular tissue repair, oral tissue repair, corneal tissue repair, cardiac tissue repair, fetal membrane repair, hepatic tissue repair, and gastric tissue repair, is systematically highlighted. Finally, the scientific challenges and the remaining opportunities are underlined to show a full picture of the supramolecular adhesive hydrogels. This review is expected to offer comparative views and critical insights to inspire more advanced studies on supramolecular adhesive hydrogels and pave the way for different fields even beyond tissue engineering applications.

Highly Flexible Hydrogel Dressing with Efficient Antibacterial, Antioxidative, and Wound Healing Performances

Bacterial induced wound infection is very common in real life, but the abuse of antibiotics brings a potential threat to human health. The development of non-antibiotic type antibacterial materials appears...

A bionic cellulose nanofiber-based nanocage wound dressing for NIR-triggered multiple synergistic therapy of tumors and infected wounds

Tumor recurrence and drug-resistant bacterial infection are the main reasons that wounds heal with difficulty after skin tumor treatment. The near infrared- (NIR-) and pH-responsive, bionic, cellulose nanofiber-based (CNF-based) nanocage wound dressing with biocompatibility, bioviscosity, and shape adaptability is designed for dual NIR-triggered photothermal therapy of tumor and infection-induced wound healing. The wound dressing with the intertwining three dimensional (3D) nanocage network structure is skillfully constructed using NIR-responsive cellulose nanofibers and pH-responsive cellulose nanofibers as the skeleton, which endows the dressing with a high drug-loading capacity of doxorubicin (400 mg·g^-1), and indocyanine green (25 mg·g^-1). Moreover, the NIR- and pH-responsive bionic "On/Off" switches of the dressing enable a controllable and efficient drug release onto the wound area. The dual NIR-triggered wound dressing with excellent photothermal conversion performance possesses good antibacterial properties against Escherichia coli, Staphylococcus aureus, and drug-resistant Staphylococcus aureus. It could effectively eliminate bacterial biofilms and kill A375 tumor cells. Interestingly, the bionic wound dressing with shape adaptability could adapt and treat irregular postoperative skin tumor wounds and drug-resistant bacterial infection via the synergistic therapy of photothermal, photodynamic, and chemotherapy, which provides an ideal strategy for clinical intervention.

Skin-Adaptable, Long-Lasting Moisture, and Temperature-Tolerant Hydrogel Dressings for Accelerating Burn Wound Healing without Secondary Damage

Developing multifunctional wound dressings, possessing not only skin-like mechanical properties and adaptability, long-lasting moisture, and temperature tolerance that maximally mimics the human skin but also on-demand adhesion without unnecessary bleeding and secondary damage upon peeling, is necessary but remains a challenge. Herein, a novel dual cross-linked and multifunctional hydrogel, termed PSNC hydrogel for polymerized sulfobetaine methacrylate (SBMA), N-(2-amino-2-oxyethyl)acrylamide (NAGA), and 1-carboxy-N-methyl-N-di(2-methacryloyloxy-ethyl)methanaminium inner salt (CBMAX), was fabricated as a wound dressing for burn injuries via one-pot radical polymerization in glycerine (GLY)/H₂O solvent. The dual cross-linked network of the PSNC hydrogel combined the double hydrogen bonding of N-(2-amino-2-oxyethyl)acrylamide (NAGA) with a covalently cross-linked zwitterionic network, endowing the hydrogel with skin-like mechanical properties with a high stretchability of 1613.8 ± 79.8%, a tensile strength of 77.5 ± 1.8 kPa, and a tensile modulus of 1.9 ± 0.1 kPa. Moreover, the hydrogel with well-developed adaptability can withstand skin deformation without breaking or debonding attributed to its good tissue adhesiveness and self-healing ability. Further, the utilization of the GLY/H₂O binary solvent effectively prevented the crystallization and evaporation of free water, endowing the hydrogel with not only long-lasting moisture but also excellent temperature tolerance in a wide range from -20 to 60 °C. More importantly, the PSNC hydrogel could effectively accelerate wound healing of burn injuries and could be easily removed on-demand with saline without causing secondary damage due to intense hydration. Such a novel PSNC zwitterionic hydrogel could be a promising candidate for the treatment of burn wounds and tissue regeneration.