Dual functionalized chitosan based composite hydrogel for haemostatic efficacy and adhesive property

Biocompatible hydrogels based on quaternary ammonium salts of chitosan with high antimicrobial activity as biocidal agents for disinfection

The paper reports new hydrogels based on quaternary ammonium salts of chitosan designed as biocidal products. The chitosan derivative was crosslinked with salicylaldehyde via reversible imine bonds and supramolecular self-assemble to give dynamic hydrogels which respond to environmental stimuli. The crosslinking mechanism was demonstrated by 1H NMR and FTIR spectroscopy, and X-ray diffraction and polarized light microscopy. The hydrogel nature, self-healing and thixotropy were proved by rheological investigation and visual observation, and their morphology was assessed by scanning electron microscopy. The relevant properties for application as biocidal products, such as swelling, dissolution, bioadhesiveness, antimicrobial activity and ex-vivo hemocompatibility and in vivo local toxicity and biocompatibility on experimental mice were measured and analyzed in relationship with the imination degree and the influence of each component. It was found that the hydrogels are superabsorbent, have good adhesivity to skin and various surfaces and antimicrobial activity against relevant gram-positive and gram-negative bacteria, while being hemocompatible and biocompatible. Besides, the hydrogels are easily biodegraded in soil. All these properties recommend the studied hydrogels as ecofriendly biocidal agents for living tissues and surfaces, but also open the perspectives of their use as platform for in vivo applications in tissue engineering, wound healing, or drug delivery systems.

Spray-assisted layer-by-layer deposition of quaternized chitosan/tannic acid for the construction of multifunctional bio-based nonwoven dressings

Gauze wound dressings have received considerable attention due to their cost-effectiveness, excellent mechanical properties, and widespread applications. However, their inability to actively combat microorganisms and effectively scavenge free radicals results in suboptimal wound management. In this study, a novel nonwoven-based gauze dressing coated with quaternized chitosan/tannic acid (QCS/TA), based on electrostatic interaction and hydrogen bonding, was successfully prepared using a spray-assisted layer-by-layer assembly method. The bio-based nonwoven dressing, assembled with multiple interlacing bilayers, demonstrated outstanding antimicrobial properties, eliminating 99.99 % of Staphylococcus aureus (S. aureus) and 85 % of Escherichia coli (E. coli). Compared to the pristine nonwoven dressing, the QCS/TA-coated nonwoven dressing scavenged >85 % of the surrounding radicals within 2 h. Additionally, the nonwoven dressing exhibits excellent coagulation properties. Notably, the facile spraying procedure preserved most of the softness and breathability of the nonwoven substrate. After the deposition of seven bilayers, the bending stiffness and drape coefficient increased by only 37.63 % and 3.85 %, respectively, while the air permeability and moisture permeability reached 1712 mm/s and 3683.58 g/m2/d, respectively. This bio-based nonwoven dressing, derived from safe and non-toxic ingredients, holds promise as the next generation of multifunctional gauze dressings.

Chitosan Hemostatic Dressings: Properties and Surgical Applications

Wounds caused by trauma and/or surgery represent a significant challenge in contemporary medical practice, requiring innovative approaches to promote optimal healing and reduce the risk of bleeding and complications resulting from it. In this context, chitosan, a natural polysaccharide derived from chitin, represents an ideal material for the study and application of medical devices, in the form of dressings, in wound management for pre- and/or post-operative wounds due to its ability to induce hemostasis and its high biocompatibility with biological tissues. The aim of this work was to discuss the structural characteristics, properties and application of chitosan-based hemostatic dressings in hemostatic processes resulting from pre- or post-surgical approaches.

Insect chitosan/pullulan/gallium photo-crosslinking hydrogels with multiple bioactivities promote MRSA-infected wound healing

Methicillin-resistant Staphylococcus aureus (MRSA) and other drug-resistant bacteria have become more common in recent years, which has made it extremely difficult to treat and heal many different kinds of wounds and caused enormous financial losses. Because of its unique "Trojan horse" function, Ga3+ has been recognized as a new possible candidate for inhibiting and eradicating drug-resistant bacteria. Furthermore, natural polysaccharide materials with outstanding biological characteristics, such as insect chitosan (CS) and pullulan (PUL), have attracted significant interest. In this study, we used quaternized-catechol chitosan (QDCS-PA), methacrylate-dialdehyde pullulan (DPUL-GMA), and gallium ion (Ga) to create a multi-crosslinked photo-enhanced hydrogel (Q-D/Ga/UV) with antimicrobial, hemostatic, self-healing, and injectable properties for promoting MRSA-infected wound healing. In vitro, the Q-D/Ga/UV hydrogels demonstrated good mechanical properties, antioxidant capabilities, biocompatibility, hemostatic properties, and antibacterial activity. The addition of gallium ions enhanced the hydrogels' mechanical properties, hemostatic capabilities, antibacterial activity, and ability to induce wound healing. Q-D/Ga/UV hydrogel significantly promoted wound contraction, collagen deposition, and angiogenesis while also suppressing inflammation in a whole-skin wound model of MRSA-infected rats. In conclusion, Q-D/Ga/UV hydrogels demonstrate significant promise for healing wounds infected with drug-resistant bacteria.

Self-healing, antioxidant, and antibacterial Bletilla striata polysaccharide-tannic acid dual dynamic crosslinked hydrogels for tissue adhesion and rapid hemostasis

Biomaterials capable of achieving effective sealing and hemostasis at moist wounds are in high demand in the clinical management of acute hemorrhage. Bletilla striata polysaccharide (BSP), a natural polysaccharide renowned for its hemostatic properties, holds promising applications in biomedical fields. In this study, a dual-dynamic-bonds crosslinked hydrogel was synthesized via a facile one-pot method utilizing poly(vinyl alcohol) (PVA)-borax as a matrix system, followed by the incorporation of BSP and tannic acid (TA). Chemical borate ester bonds formed around borax, coupled with multiple physical hydrogen bonds between BSP and other components, enhanced the mechanical properties and rapid self-healing capabilities. The catechol moieties in TA endowed the hydrogel with excellent adhesive strength of 30.2 kPa on the surface of wet tissues and facilitated easy removal without residue. Benefiting from the synergistic effect of TA and the preservation of the intrinsic properties of BSP, the hydrogel exhibited outstanding biocompatibility, antibacterial, and antioxidant properties. Moreover, it effectively halted acute bleeding within 31.3 s, resulting in blood loss of 15.6 % of that of the untreated group. As a superior hemostatic adhesive, the hydrogel in this study is poised to offer a novel solution for addressing future acute hemorrhage, wound healing, and other biomedical applications.

Recent Advances in the Degradability and Applications of Tissue Adhesives Based on Biodegradable Polymers

In clinical practice, tissue adhesives have emerged as an alternative tool for wound treatments due to their advantages in ease of use, rapid application, less pain, and minimal tissue damage. Since most tissue adhesives are designed for internal use or wound treatments, the biodegradation of adhesives is important. To endow tissue adhesives with biodegradability, in the past few decades, various biodegradable polymers, either natural polymers (such as chitosan, hyaluronic acid, gelatin, chondroitin sulfate, starch, sodium alginate, glucans, pectin, functional proteins, and peptides) or synthetic polymers (such as poly(lactic acid), polyurethanes, polycaprolactone, and poly(lactic-co-glycolic acid)), have been utilized to develop novel biodegradable tissue adhesives. Incorporated biodegradable polymers are degraded in vivo with time under specific conditions, leading to the destruction of the structure and the further degradation of tissue adhesives. In this review, we first summarize the strategies of utilizing biodegradable polymers to develop tissue adhesives. Furthermore, we provide a symmetric overview of the biodegradable polymers used for tissue adhesives, with a specific focus on the degradability and applications of these tissue adhesives. Additionally, the challenges and perspectives of biodegradable polymer-based tissue adhesives are discussed. We expect that this review can provide new inspirations for the design of novel biodegradable tissue adhesives for biomedical applications.

Preparation and Application of Hemostatic Hydrogels

Hemorrhage remains a critical challenge in various medical settings, necessitating the development of advanced hemostatic materials. Hemostatic hydrogels have emerged as promising solutions to address uncontrolled bleeding due to their unique properties, including biocompatibility, tunable physical characteristics, and exceptional hemostatic capabilities. In this review, a comprehensive overview of the preparation and biomedical applications of hemostatic hydrogels is provided. Particularly, hemostatic hydrogels with various materials and forms are introduced. Additionally, the applications of hemostatic hydrogels in trauma management, surgical procedures, wound care, etc. are summarized. Finally, the limitations and future prospects of hemostatic hydrogels are discussed and evaluated. This review aims to highlight the biomedical applications of hydrogels in hemorrhage management and offer insights into the development of clinically relevant hemostatic materials.

Konjac glucomannan-based nanocomposite spray coating with antimicrobial, gas barrier, UV blocking, and antioxidation for bananas preservation

Fruit is prone to rot and deterioration due to oxidative browning and microbial infection during storage, which can cause serious economic losses and food safety problems. It is urgent to develop a multifunctional composite coating to extend the shelf life of fruits. In this work, multifunctional quaternized chitosan nanoparticles (QCs/TA NPs) with excellent antibacterial and antioxidant properties were prepared based on electrostatic interaction using tannic acid instead of conventional cross-linking agents. Meanwhile, konjac glucomannan (KGM) with high viscosity, edible and biodegradable properties was used as a dispersant to disperse and stabilize the nanoparticles, and as a film-forming agent to form a multifunctional composite coating. The composite coating exhibited excellent oxygen and water vapor barrier properties, antioxidant, antibacterial, mechanical properties, hydrophobicity, and UV shielding properties. Surprisingly, the oxygen permeability of the K-NPs-15 composite film was as low as 1.93 × 10-13 (cm3·cm)/(cm2·s·Pa). The banana spray preservation experiments proved that the K-NPs-15 composite coating could effectively prolong the shelf life of bananas. Therefore, this study provides a new idea for designing multifunctional freshness preservation coatings, which has a broad application prospect.

Cyanoremediation of heavy metals (As(v), Cd(ii), Cr(vi), Pb(ii)) by live cyanobacteria (Anabaena variabilis, and Synechocystis sp.): an eco-sustainable technology

The cyanoremediation technique for heavy metal (HM) removal from wastewater using live cyanobacteria is promising to reduce the pollution risk both for the environment and human health. In this study, two widely recognized freshwater cyanobacteria, Anabaena variabilis and Synechocystis sp., were used to explore their efficacy in HM (As(v), Cd(ii), Cr(vi), Pb(ii)) removal. The different optimum adsorption conditions were pH 8 and 7.5 for A. variabilis and Synechocystis sp., respectively, but the temperature (25 °C) and contact time (48 hours) were the same for both strains. Under these specified conditions, A. variabilis exhibited the capability to remove 25% of As(v), 78% of Cd(ii), 54% of Cr(vi), and 17% of Pb(ii), whereas Synechocystis sp. removed 77% of As(v), 57% of Cd(ii), 91% of Cr(vi), and 77% of Pb(ii) at different initial concentrations. Metal diversity interfered negatively with cyanobacterial growth, especially Cd(ii) and As(v), as measured by OD730, dry biomass, chlorophyll a, and carotenoid production for both strains. Fourier transform infrared spectrum (FT-IR) analysis revealed the existence of diverse surface binding sites for HM adsorption, stemming from proteins and polysaccharides. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) confirmed the presence of HMs on the surface of the cyanobacterial cells. Finally, the zeta potential results indicating alterations in the surface negative charges elucidated the adsorption mechanisms involved in the HM removal by both cyanobacteria. These results provided a comprehensive understanding of the HM adsorption mechanism by cyanobacteria, offering valuable theoretical insights that can be extrapolated to enhance our comprehension of the cyanoremediation mechanisms by various other cyanobacterial strains.

A double-network porous hydrogel based on high internal phase emulsions as a vehicle for potassium sucrose octasulfate delivery accelerates diabetic wound healing

Diabetic wounds are a difficult medical challenge. Excessive secretion of matrix metalloproteinase-9 (MMP-9) in diabetic wounds further degrades the extracellular matrix and growth factors and causes severe vascular damage, which seriously hinders diabetic wound healing. To solve these issues, a double-network porous hydrogel composed of poly (methyl methacrylate-co-acrylamide) (p(MMA-co-AM)) and polyvinyl alcohol (PVA) was constructed by the high internal phase emulsion (HIPE) technique for the delivery of potassium sucrose octasulfate (PSO), a drug that can inhibit MMPs, increase angiogenesis and improve microcirculation. The hydrogel possessed a typical polyHIPE hierarchical microstructure with interconnected porous morphologies, high porosity, high specific surface area, excellent mechanical properties and suitable swelling properties. Meanwhile, the p(MMA-co-AM)/PVA@PSO hydrogel showed high drug-loading performance and effective PSO release. In addition, both in vitro and in vivo studies showed that the p(MMA-co-AM)/PVA@PSO hydrogel had good biocompatibility and significantly accelerated diabetic wound healing by inhibiting excessive MMP-9 in diabetic wounds, increasing growth factor secretion, improving vascularization, increasing collagen deposition and promoting re-epithelialization. Therefore, this study provided a reliable therapeutic strategy for diabetic wound healing, some theoretical basis and new insights for the rational design and preparation of wound hydrogel dressings with high porosity, high drug-loading performance and excellent mechanical properties.

Chemical modification of chitosan for developing of new hemostatic materials: A review

Uncontrolled bleeding that occurs during surgery, trauma, and in combat conditions is critical and require immediate action. Chitosan is a polysaccharide, obtained from natural sources with unique biological properties. It is often used as basis for local hemostatic agents (LHA). We summarized the data on hemostatic properties of chitosan, commercially available chitosan-based products with focus in the field of chemical modification of chitosan. Various approaches are used to enhance hemostatic activity of chitosan-based materials. The approach with chemical modification of chitosan allows changing the properties of the polymer in order to obtain an active macromolecule that contributes to hemostasis. Ongoing research on the mechanism of interaction with blood components in the case of different chitosan derivatives will make it possible to identify promising directions for chemical modification to obtain an effective LHA.

Tailoring the Swelling-Shrinkable Behavior of Hydrogels for Biomedical Applications

Hydrogels with tailor-made swelling-shrinkable properties have aroused considerable interest in numerous biomedical domains. For example, as swelling is a key issue for blood and wound extrudates absorption, the transference of nutrients and metabolites, as well as drug diffusion and release, hydrogels with high swelling capacity have been widely applicated in full-thickness skin wound healing and tissue regeneration, and drug delivery. Nevertheless, in the fields of tissue adhesives and internal soft-tissue wound healing, and bioelectronics, non-swelling hydrogels play very important functions owing to their stable macroscopic dimension and physical performance in physiological environment. Moreover, the negative swelling behavior (i.e., shrinkage) of hydrogels can be exploited to drive noninvasive wound closure, and achieve resolution enhancement of hydrogel scaffolds. In addition, it can help push out the entrapped drugs, thus promote drug release. However, there still has not been a general review of the constructions and biomedical applications of hydrogels from the viewpoint of swelling-shrinkable properties. Therefore, this review summarizes the tactics employed so far in tailoring the swelling-shrinkable properties of hydrogels and their biomedical applications. And a relatively comprehensive understanding of the current progress and future challenge of the hydrogels with different swelling-shrinkable features is provided for potential clinical translations.

Synergistic Effect of Thermoresponsive and Photocuring Methacrylated Chitosan-Based Hybrid Hydrogels for Medical Applications

The thermoresponsive drug-loaded hydrogels have attracted widespread interest in the field of medical applications due to their ease of delivery to structurally complex tissue defects. However, drug-resistant infections remain a challenge, which has prompted the development of new non-antibiotic hydrogels. To this end, we prepared chitosan-methacrylate (CTSMA)/gelatin (GEL) thermoresponsive hydrogels and added natural phenolic compounds, including tannic acid, gallic acid, and pyrogallol, to improve the efficacy of hydrogels. This hybrid hydrogel imparted initial crosslinking at physiological temperature, followed by photocuring to further provide a mechanically robust structure. Rheological analysis, tensile strength, antibacterial activity against E. coli, S. aureus, P. gingivalis, and S. mutans, and L929 cytotoxicity were evaluated. The experimental results showed that the hybrid hydrogel with CTSMA/GEL ratio of 5/1 and tannic acid additive had a promising gelation temperature of about 37 °C. The presence of phenolic compounds not only significantly (p < 0.05) enhanced cell viability, but also increased the tensile strength of CTSMA/GEL hybrid hydrogels. Moreover, the hydrogel containing tannic acid revealed potent antibacterial efficacy against four microorganisms. It was concluded that the hybrid hydrogel containing tannic acid could be a potential composite material for medical applications.

Tannic acid-crosslinked O-carboxymethyl chitosan hydrogels for enhanced antibacterial activity and rapid hemostasis

Bacterial infection and massive blood loss are major challenges for global public health. Herein, a series of tannic acid encapsulated O-carboxymethyl chitosan (CMC) based hydrogels were prepared using a facile approach for both hemorrhage control and effective anti-bacterium. The results indicated that the tannic acid-cosslinked CMC hydrogels had excellent mechanical property, swelling ability as well as great cytocompatibility. Comparably, with increasing tannic acid loading, the bleeding control and antibacterial performance against both E. coli and S. aureus were improved simultaneously, especially for the 5% tannic acid-cosslinked CMC hydrogel. Moreover, the prepared CMC hydrogel loading with tannic acid could induce hemocytes and platelets aggregation, promote the blood clotting and achieve bleeding control in vivo due to the interconnected fibrous web structure and the chemical activation (the phenol group of tannic acid). Thus, the resultant CMC hydrogel enabled the maintenance of high bioavailability of tannic acid and synchronization with the interconnected fibrous structure of CMC hydrogels, which was expected to be a promising candidate for robust and safe hemostatic dressings.

Highly effective sustainable membrane based cyanobacteria for uranium uptake from aqueous environment

Wastewater from industrial process of uranium ore mining contains a large amount of this radioactive pollutant. Regarding the advantages of biosorption, it was found that varieties of biomasses such as agricultural waste, algae and fungi are effective for uranium removal. However, there is limited research on cyanobacteria, therefore, cyanobacteria, Anagnostidinema amphibium (CAA) was investigated by batch method for the first time for biosorption of uranium (VI). Optimization of biosorption parameters showed that maximum removal efficiency of 92.91% was reached at pH range of 9-11 with 50 mg of cyanobacteria to 100 mg/L U(VI) initial concentration, at 25 °C within 40 min. Used biosorbent exhibited very good selectivity for U(VI) ions and reusability in IV sorption/desorption cycles. Characterization of CAA surface was performed by FTIR, EDS, EDXRF and SEM analysis and it has shown various functional groups (CONH, COOH, OH, PO alkyl group) and that it is very rich in elements such as iron, potassium and calcium. In binary systems, contained of U(VI) and selected ions, CAA exhibits very good selectivity towards U(VI) ions. Kinetic data revealed the best accordance of experimental data with the pseudo-second-order model and isotherms data agreed with Freundlich model. Thermodynamic data implied that U(VI) biosorption process by A. amphibium exhibited spontaneity and modelling of the investigated process showed that the adsorption of uranium ions occurs mainly via peptidoglycan carboxyl groups. Overall results show that these cyanobacteria with a maximum sorption capacity of 324.94 mg/g have great potential for the processing of wastewater polluted with uranium (VI).

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

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

Mussel-inspired nanocomposite hydrogel based on alginate and antimicrobial peptide for infected wound repair

Timely hemostasis, antibacterial activity, and good adhesion are essential for wound healing. Here, we report about a novel nanocomposite hydrogel with hemostatic, antibacterial, and adhesive properties constructed with a mussel-inspired strategy. Oxidized alginic acid, dopamine, and antimicrobial peptide ε-polylysine were used to prepare a nanocomposite (ODP), and then further cross-linked with acrylamide to fabricate a nanocomposite hydrogel (ODPA). ODPA hydrogel can adhere to the surface of bleeding organs and arrest bleeding within 30 s. It can also be stretched to 12 times its original length and withstand a compression strain of 40 %, and shows effective inhibition on gram-positive and gram-negative bacteria. Compared with commercial alginate sponge, ODPA hydrogel can accelerate the healing of infected full-thickness wound by reducing inflammation, promoting angiogenesis, and collagen deposition. Therefore, the nanocomposite hydrogel is expected to be a multifunctional dressing for promoting healing of infected wounds.

Tannic acid: a versatile polyphenol for design of biomedical hydrogels

Tannic acid (TA), a natural polyphenol, is a hydrolysable amphiphilic tannin derivative of gallic acid with several galloyl groups in its structure. Tannic acid interacts with various organic, inorganic, hydrophilic, and hydrophobic materials such as proteins and polysaccharides via hydrogen bonding, electrostatic, coordinative bonding, and hydrophobic interactions. Tannic acid has been studied for various biomedical applications as a natural crosslinker with anti-inflammatory, antibacterial, and anticancer activities. In this review, we focus on TA-based hydrogels for biomaterials engineering to help biomaterials scientists and engineers better realize TA's potential in the design and fabrication of novel hydrogel biomaterials. The interactions of TA with various natural or synthetic compounds are deliberated, discussing parameters that affect TA-material interactions thus providing a fundamental set of criteria for utilizing TA in hydrogels for tissue healing and regeneration. The review also discusses the merits and demerits of using TA in developing hydrogels either through direct incorporation in the hydrogel formulation or indirectly via immersing the final product in a TA solution. In general, TA is a natural bioactive molecule with diverse potential for engineering biomedical hydrogels.

Chitosan: Sources, Processing and Modification Techniques

Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (M_w) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications.

Polyphenol-based hydrogels: Pyramid evolution from crosslinked structures to biomedical applications and the reverse design

As a kind of nature-derived bioactive materials, polyphenol-based hydrogels possess many unique and outstanding properties such as adhesion, toughness, and self-healing due to their specific crosslinking structures, which have been widely used in biomedical fields including wound healing, antitumor, treatment of motor system injury, digestive system disease, oculopathy, and bioelectronics. In this review, starting with the classification of common polyphenol-based hydrogels, the pyramid evolution process of polyphenol-based hydrogels from crosslinking structures to derived properties and then to biomedical applications is elaborated, as well as the efficient reverse design considerations of polyphenol-based hydrogel systems are proposed. Finally, the existing problems and development prospects of these hydrogel materials are discussed. It is hoped that the unique perspective of the review can promote further innovation and breakthroughs of polyphenol-based hydrogels in the future.

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Polyphenol-based hydrogels combine advantages of polyphenols with common hydrogels.

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Cognition of such hydrogels underwent from structures to properties to applications.

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Various crosslinked structures of such hydrogels can derive outstanding properties.

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Such hydrogels can be widely used in biomedicine due to the outstanding properties.

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Reverse design thought from applications to properties to structures is promising.

Adsorption of uranium by chitosan/Chlorella pyrenoidosa composite adsorbent bearing phosphate ligand

In order to remove and recover uranium from acidic uranium-bearing wastewater in uranium mining and metallurgy. Herein, a novel chitosan/Chlorella pyrenoidosa composite adsorbent bearing phosphate ligand (CSP/CP) was designed and synthesized, demonstrating a high uranium adsorption capacity at a pH of 5 and excellent selectivity in an aqueous solution with eight coexisting ions. The CSP/CP exhibits a maximum adsorption capacity (1393.338 mg g^-1) and selectivity (Su = 80.53%) for uranium, which is higher than many reported adsorbents. Mechanism analysis shows that the surface of CSP/CP is rich in hydroxyl, amino, phosphate and carboxyl groups, resulting in an excellent three-dimensional structure with active sites for high-performance uranium adsorption; U(VI) is selectively bound via ion exchanges with -COOH and -OH and through surface complexation with NH₂ and PO. Furthermore, by desorption with 0.1 M Na₂CO₃ + 2% H₂O₂ at 318 K, CSP/CP can be recycled more than five times. It provides a new scientific basis for the preparation of high selectivity composite adsorbent by chitosan.

Permanganate release from silica-based hollow mesoporous coagulant combined with UV for spatiotemporal enrichment and degradation of diclofenac sodium

In this work, the novel hollow mesoporous coagulant was prepared by chitosan-polydopamine coating and permanganate loading into silica nanoparticles for investigating the simultaneous enrichment and degradation of diclofenac sodium (DCFS) combined with ultraviolet irradiation. The enrichment kinetic of DCFS was explained well with pseudo-second-order model, indicating the exist of hydrogen bonding. Based on the correlation coefficients, the enriched isotherms were fitted by models which accorded with the BET > Freundlich > Langmuir sequence. The result showed that, in addition to the coagulant and DCFS, there were aromatic stackings among DCFS molecules. Due to both effects of which, the DCFS enrichment could be realized significantly in the range of pH 4.0-9.0. It was degraded at the copresence of ultraviolet and permanganate released from coagulant in acidic aqueous medium. The release mechanism was simulated through Korsmayer-Peppas model, implying case-II transport and Fickian diffusion. Additionally, Mn (V) and •OH radicals were vital in the DCFS degradation process. The coagulant could be reloaded at least ten times and that from each cycle was used directly for DCFS removal for six times without rinse process, which provided a potential application in environmental remediation.

Preparation and characterization of antibacterial and anti-inflammatory hyaluronic acid-chitosan-dexamethasone hydrogels for peri-implantitis repair

Numerous treatment methods for peri-implantitis have been widely used including oral cleaning, traditional metal scraping means, or local antibiotic application. However, to continuously release antibacterial and anti-inflammatory drug in location in situ for effective peri-implantitis repair is still challenging. Herein, an anti-inflammatory drug dexamethasone (DE)-incorporated hyaluronic acid (HA)-chitosan (CT) composite hydrogels system was developed to repair peri-implantitis. The physicochemical characterization and biocompatibility of the hydrogel were evaluated in vitro. The in vivo hydrogels degradation and peri-implantitis repair were assessed in mice. The results showed that the prepared multifunctional hydrogels achieved sustained release, with an equilibrium swelling of 18, and promoted the growth against NIH-3T3 fibroblast cells. The in vitro antibacterial tests showed HA-CT-DE hydrogels can inhibit methicillin-resistant Staphylococcus aureus and Escherichia coli. It down-regulated the expression levels of inflammation factor IL-1β, IL-6 and, TNF-α in peri-implantitis. The prepared HA-CT-DE composite hydrogels with integrated function is promising for the treatment of peri-implantitis.

Recent advances on polymeric hydrogels as wound dressings

Severe hemorrhage is a leading cause of high mortality in critical situations like disaster, accidents, and warfare. The resulting wounds could induce severe physical and psychological trauma to patients and also bring an immense socio-economic burden. Hence, rapid hemostasis and wound healing techniques have become critical initiatives for life-saving treatment. Although traditional methods relying on bandages and gauzes are effective in controlling hemorrhage, they suffer from several limitations: nonbiodegradability, being susceptible to infection, being unsuitable for the irregular wound, secondary tissue damage, and being almost ineffective for wound healing. Owing to the merits of high porosity, good biocompatibility, tunable physicochemical properties, and being beneficial for wound healing, hydrogels with excellent performance have drawn intensive attention and numerous novel effective hydrogel dressings have been widely developed. In this Review, after introducing some commonly used strategies for the synthesis of hydrogels, the most recent progress on polymer-based hydrogels as wound dressings is discussed. Particularly, their hemostasis, antibacterial, and biodegradation properties are introduced. Finally, challenges and future perspectives about the development of hydrogels for wound dressings are outlined.

Vasoconstrictor and coagulation activator entrapped chitosan based composite hydrogel for rapid bleeding control

Chitosan (Cs) as a hemostatic agent has been in use to control hemorrage. Composite hydrogel formed by entrapment of vasoconstrictor-potassium aluminium sulfate (0.25 %PA) and coagulation activator-calcium chloride (0.25 %Ca) into Cs (2 %) hydrogel would enhance the hemostatic property of Cs. In this work, the prepared composite hydrogel was injectable, shear thinning, cyto and hemocompatible. The 2 %Cs-0.25 %PA-0.25 %Ca composite hydrogel caused rapid blood clotting by accelerating RBC/platelet aggregation and activation of the coagulation cascade. Further, in vivo studies on rat liver and femoral artery hemorrage model showed the efficiency of 2 %Cs-0.25 %PA-0.25 %Ca composite hydrogel to achieve hemostasis in a shorter time (20 ± 10 s, 105 ± 31 s) than commercial hemostatic agents-Fibrin sealant (77 ± 26 s, 204 ± 58 s) and Floseal (76 ± 15 s, 218 ± 46 s). In in vivo toxicological study, composite hydrogel showed material retention even after 8 weeks post-surgery, therefore excess hydrogel should be irrigated from site of application. This prepared composite hydrogel based hemostatic agent has potential application in low pressure bleeding sites.

Immobilized thrombin on X-ray radiopaque polyvinyl alcohol/chitosan embolic microspheres for precise localization and topical blood coagulation

Trans-catheter arterial embolization (TAE) plays an important role in treating various diseases. The available embolic agents lack X-ray visibility and do not prevent the reflux phenomenon, thus hindering their application for TAE therapy. Herein, we aim to develop a multifunctional embolic agent that combines the X-ray radiopacity with local procoagulant activity. The barium sulfate nanoparticles (BaSO₄ NPs) were synthesized and loaded into the polyvinyl alcohol/chitosan (PVA/CS) to prepare the radiopaque BaSO₄/PVA/CS microspheres (MS). Thereafter, thrombin was immobilized onto the BaSO₄/PVA/CS MS to obtain the thrombin@BaSO₄/PVA/CS MS. The prepared BaSO₄/PVA/CS MS were highly spherical with diameters ranging from 100 to 300 μm. In vitro CT imaging showed increased X-ray visibility of BaSO₄/PVA/CS MS with the increased content of BaSO₄ NPs in the PVA/CS MS. The biocompatibility assessments demonstrated that the MS were non-cytotoxic and possessed permissible hemolysis rate. The biofunctionalized thrombin@BaSO₄/PVA/CS MS showed improved hemostatic capacity and facilitated hemostasis in vitro. Additionally, in vivo study performed on a rabbit ear embolization model confirmed the excellent X-ray radiopaque stability of the BaSO₄/PVA/CS MS. Moreover, both the BaSO₄/PVA/CS and thrombin@BaSO₄/PVA/CS MS achieved superior embolization effects with progressive ischemic necrosis on the ear tissue and induced prominent ultrastructural changes in the endothelial cells. The findings of this study suggest that the developed MS could act as a radiopaque and hemostatic embolic agent to improve the embolization efficiency.

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Excellent in vitro and in vivo visibility of BaSO₄/PVA/CS MS.

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Excellent cytocompatibility and hemocompatibility of BaSO₄/PVA/CS MS.

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Enhanced hemostatic capacity and hemostasis of thrombin@BaSO₄/PVA/CS MS.

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Potential application of thrombin@BaSO₄/PVA/CS MS for in vivo embolization.

One-pot, self-catalyzed synthesis of self-adherent hydrogels for photo-thermal, antimicrobial wound treatment

Self-adhering hydrogels are promising materials to be employed as wound dressings, because they can be used for wound healing without the necessity of additional stitching. However, micro-organisms can easily adhere to these hydrogels as well, which usually causes wound infections. Therefore, adhesive hydrogels are often combined with antibiotics. However, this introduces a risk of drug resistance, cytotoxicity and poor cell affinity. Consequently, recently, there has been great interest in developing non-antibiotic, antibacterial adhesive hydrogels. In this article, we present a simple one-pot synthesis procedure to prepare self-adhesive hydrogels composed of poly(acrylamide) (PAM), naturally derived chitosan (CS) and tannic acid/ferric ion chelates (TA@Fe³⁺). TA@Fe³⁺ enables self-catalysis of the polymerization reaction. In addition, due to its near infrared (NIR) photothermal responsiveness, TA@Fe³⁺ allows for eliminating the bacterial activity with up to 91.6% and 94.7% effectivity against Escherichia coli and Staphylococcus aureus, respectively. Mechanical and adhesion testing shows that the hydrogels are tough as well as flexible and will adhere repeatedly to many types of biological tissues, which can be attributed to the combination of physical and chemical bonding between TA@Fe³⁺ and PAM and CS, respectively. Moreover, in vitro and in vivo tests indicate that the NIR photothermally active hydrogel can effectively prevent bacterial infection and accelerate tissue regeneration, which demonstrates that these hydrogels are promising functional materials for wound healing applications.