Multifunctional Tissue-Adhesive Cryogel Wound Dressing for Rapid Nonpressing Surface Hemorrhage and Wound Repair

Tunicate cellulose nanocrystal reinforced multifunctional hydrogel with super flexible, fatigue resistant, antifouling and self-adhesive capability for effective wound healing

Hydrogels as skin wound dressings have been extensively studied owing to their good flexibility and biocompatibility. Nevertheless, the mechanical performance, adhesive capability, antifouling and antibacterial properties of conventional hydrogels are still unsatisfactory, which hinder the application of hydrogel for cutaneous healing. Here, we developed a novel biocompatible multifunctional hydrogel with super flexible, fatigue resistant, antifouling and self-adhesive capability for effective wound healing, where naturally rigid polymers including quaternized chitosan (QCS) and Tunicate cellulose nanocrystals (TCNCs) are used as bioactive cross-linkers and reinforcers to endow the hydrogel with excellent mechanical and antibacterial property, and the synergistic contributions from the poly(acrylic acid/methacrylate anhydride dopamine/sulfobetaine methacrylate) (poly(AA/DMA/SBMA)) chains and QCS endow the hydrogel with excellent adhesive property, antioxidant, antifouling and pH-responsive sustained drug release capabilities. The optimized hydrogel exhibited high tensile strength (77.69 KPa), large tensile strain (889.9 %), large toughness (307.51KJ.m-3), high adhesive strength (35.57 KPa) and ideal compressive property. The in vivo infected full-thickness skin model demonstrated that the hydrogel with vanvomycin sustained release ability efficiently improved the granulation tissue formation, facilitating collagen deposition and reducing inflammatory expression, thus effectively accelerating wound healing. This superiorly skin-adhesive antibacterial biocompatible hydrogel appears to be a promising candidate for wound therapy.

Chitosan-based self-healing hydrogel dressing for wound healing

Skin has strong self-regenerative capacity, while severe skin defects do not heal without appropriate treatment. Therefore, in order to cover the wound sites and hasten the healing process, wound dressings are required. Hydrogels have emerged as one of the most promising candidates for wound dressings because of their hydrated and porous molecular structure. Chitosan (CS) with biocompatibility, oxygen permeability, hemostatic and antimicrobial properties is beneficial for wound treatment and it can generate self-healing hydrogels through reversible crosslinks, from dynamic covalent bonding, such as Schiff base bonds, boronate esters, and acylhydrazone bonds, to physical interactions like hydrogen bonding, electrostatic interaction, ionic bonding, metal-coordination, host-guest interactions, and hydrophobic interaction. Therefore, various chitosan-based self-healing hydrogel dressings have been prepared in recent years to cope with increasingly complex wound conditions. This review's objective is to provide comprehensive information on the self-healing mechanism of chitosan-based hydrogel wound dressings, discuss their advanced functions including antibacterial, conductive, anti-inflammatory, anti-oxidant, stimulus-responsive, hemostatic/adhesive and controlled release properties, further introduce their applications in the promotion of wound healing in two categories: acute and chronic (infected, burn and diabetic) wounds, and finally discuss the future perspective of chitosan-based self-healing hydrogel dressings for wound healing.

An injectable adhesive hydrogel for photothermal ablation and antitumor immune activation against bacteria-associated oral squamous cell carcinoma

Pathogenic bacteria are closely associated with the occurrence, development and metastasis of oral squamous cell carcinoma (OSCC). Antibacterial therapy has been considered an enhancement strategy to suppress bacteria-associated tumors and promote anti-tumor immune responses. Herein, we developed an injectable adhesive hydrogel, PNIPAM/DL@TIR, for the in situ photothermal ablation and robust stimulation of antitumor immunity against OSCC colonized by Porphyromonas gingivalis (Pg), one of the major oral pathogenic bacteria. PNIPAM/DL@TIR, composed of poly(N-isopropylacrylamide), demethylated lignin, and TAT peptide-conjugated IR820, was prepared using a simple dissolve-dry-swell solvent exchange method. Upon 808 nm laser irradiation, PNIPAM/DL@TIR exerted photothermal effects to ablate Pg-colonized OSCC and generate dual tumor and bacterial antigens. Owing to its large number of catechol groups, PNIPAM/DL@TIR efficiently captured these antigens to form an in situ antigen repository, thereby eliciting robust and durable antitumor immune responses. Proteomic analysis revealed that the captured antigens comprised both tumor neoantigens and bacterial antigens. The catechol groups endowed PNIPAM/DL@TIR with antioxidant activity, which was also conducive to stimulating antitumor immunity. Altogether, this study develops an injectable adhesive hydrogel and provides a combination strategy for treating bacteria-associated OSCC. STATEMENT OF SIGNIFICANCE: In this study, we developed an injectable adhesive hydrogel, PNIPAM/DL@TIR, for in situ photothermal ablation and robust stimulation of antitumor immunity against OSCC colonized by Porphyromonas gingivalis, one of the major oral pathogenic bacteria. PNIPAM/DL@TIR, which consists of poly(N-isopropylacrylamide), demethylated lignin, and TAT peptide-conjugated IR820 exhibited outstanding photothermal performance. Owing to the presence of catechol groups, PNIPAM/DL@TIR has good bioadhesive properties and can capture protein antigens to form in situ antigen repository, thus initiating robust and long-term antitumor immune responses. In addition, PNIPAM/DL@TIR exhibited strong antioxidant activity that is favorable for promoting antitumor immunity. In the mouse model of OSCC with bacterial infection, PNIPAM/DL@TIR not only ablated the primary tumors upon NIR laser irradiation, but also induced tumor and bacterial vaccination in situ to suppress distant tumors and lung metastasis.

Hybrid machine learning model based predictions for properties of poly(2-hydroxyethyl methacrylate)-poly(vinyl alcohol) composite cryogels embedded with bacterial cellulose

Supermacroporous composite cryogels with enhanced adjustable functionality have received extensive interest in bioseparation, tissue engineering, and drug delivery. However, the variations in their components significantly impactfinal properties. This study presents a two-step hybrid machine learning approach for predicting the properties of innovative poly(2-hydroxyethyl methacrylate)-poly(vinyl alcohol) composite cryogels embedded with bacterial cellulose (pHEMA-PVA-BC) based on their compositions. By considering the ratios of HEMA (1.0-22.0 wt%), PVA (0.2-4.0 wt%), poly(ethylene glycol) diacrylate (1.0-4.5 wt%), BC (0.1-1.5 wt%), and water (68.0-96.0 wt%) as investigational variables, overlay sampling uniform design (OSUD) was employed to construct a high-quality dataset for model development. The random forest (RF) model was used to classify the preparation conditions. Then four models of artificial neural network, RF, gradient boosted regression trees (GBRT), and XGBoost were developed to predict the basic properties of the composite cryogels. The results showed that the RF model achieved an accurate three-class classification of preparation conditions. Among the four models, the GBRT model exhibited the best predictive performance of the basic properties, with the mean absolute percentage error of 16.04 %, 0.85 %, and 2.44 % for permeability, effective porosity, and height of theoretical plate (1.0 cm/min), respectively. Characterization results of the representative pHEMA-PVA-BC composite cryogel showed an effective porosity of 81.01 %, a permeability of 1.20 × 10-12 m2, and a range of height of theoretical plate between 0.40-0.49 cm at flow velocities of 0.5-3.0 cm/min. These indicate that the pHEMA-PVA-BC cryogel was an excellent material with supermacropores, low flow resistance and high mass transfer efficiency. Furthermore, the model output demonstrates that the alteration of the proportions of PVA (0.2-3.5 wt%) and BC (0.1-1.5 wt%) components in composite cryogels resulted in significant changes in the material basic properties. This work represents an attempt to efficiently design and prepare target composite cryogels using machine learning and providing valuable insights for the efficient development of polymers.

Plant-Based Shape Memory Cryogel for Hemorrhage Control

The escalating global demand for sustainable manufacturing, motivated by concerns over energy conservation and carbon footprints, encounters challenges due to insufficient renewable materials and arduous fabrication procedures to fulfill specific requirements in medical and healthcare systems. Here, biosafe pollen cryogel is engineered as effective hemostats without additional harmful crosslinkers to treat deep noncompressible wounds. A straightforward and low-energy approach is involved in forming stable macroporous cryogel, benefiting from the unique micro-hierarchical structures and chemical components of non-allergenic plant pollen. It is demonstrated that the pollen cryogel exhibits rapid water/blood-triggered shape-memory properties within 2 s. Owing to their inherent nano/micro hierarchical structure and abundant chemical functional groups on the pollen surface, the pollen cryogel shows effective hemostatic performance in a mouse liver penetration model, which is easily removed after usage. Overall, the self-crosslinking pollen cryogel in this work pioneers a framework of potential clinical applications for the first-hand treatment on deep noncompressible wounds.

Additive-free Absorbable Keratin Sponge With Procoagulant Activity for Noncompressible Hemostasis

The development of a natural, additive-free, absorbable sponge with procoagulant activity for noncompressible hemostasis remains a challenging task. In this study, we extracted high molecular weight keratin (HK) from human hair and transformed it into a hemostatic sponge with a well-interconnected pore structure using a foaming technique, freeze-drying, and oxidation cross-linking. By controlling the cross-linking degree, the resulting sponge demonstrated excellent liquid absorption ability, shape recovery characteristics, and robust mechanical properties. The HK10 sponge exhibited rapid liquid absorption, expanding up to 600% within 5 s. Moreover, the HK sponge showed superior platelet activation and blood cell adhesion capabilities. In SD rat liver defect models, the sponges demonstrated excellent hemostatic performance by sealing the wound and expediting coagulation, reducing the hemostatic time from 825 to 297 s. Furthermore, HK sponges have excellent biosafety, positioning them as a promising absorbable sponge with the potential for the treatment of noncompressible hemostasis.

Silicone Bioadhesive with Shear-Stiffening Effect: Rate-Responsive Adhesion Behavior and Wound Dressing Application

Stimuli-responsive adhesives with on-demand adhesion capabilities are highly advantageous for facilitating wound healing. However, the triggering conditions of stimuli-responsive adhesives are cumbersome, even though some of them are detrimental to the adhesive and adjacent natural tissues. Herein, a novel stimuli-responsive adhesive called shear-stiffening adhesive (SSA) has been created by constructing a poly(diborosiloxane)-based silicone network for the first time, and SSA exhibits a rate-responsive adhesion behavior. Furthermore, we introduced bactericidal factors (PVP-I) into SSA and applied it as a wound dressing to promote the healing of infected wounds. Impressively, the wound dressing not only has excellent biocompatibility and long-term antibacterial properties but also performs well in accelerating wound healing. Therefore, this study provides a new strategy for the synthesis of intelligent adhesives with force rate response, which simplifies the triggering conditions by the force rate. Thus, SSA has great potential to be applied in wound management as an intelligent bioadhesive with on-demand adhesion performance.

Neutrophil extracellular traps-inspired DNA hydrogel for wound hemostatic adjuvant

Severe traumatic bleeding may lead to extremely high mortality rates, and early intervention to stop bleeding plays as a critical role in saving lives. However, rapid hemostasis in deep non-compressible trauma using a highly water-absorbent hydrogel, combined with strong tissue adhesion and bionic procoagulant mechanism, remains a challenge. In this study, a DNA hydrogel (DNAgel) network composed of natural nucleic acids with rapid water absorption, high swelling and instant tissue adhesion is reported, like a band-aid to physically stop bleeding. The excellent swelling behavior and robust mechanical performance, meanwhile, enable the DNAgel band-aid to fill the defect cavity and exert pressure on the bleeding vessels, thereby achieving compression hemostasis for deep tissue bleeding sites. The neutrophil extracellular traps (NETs)-inspired DNAgel network also acts as an artificial DNA scaffold for erythrocytes to adhere and aggregate, and activates platelets, promoting coagulation cascade in a bionic way. The DNAgel achieves lower blood loss than commercial gelatin sponge (GS) in male rat trauma models. In vivo evaluation in a full-thickness skin incision model also demonstrates the ability of DNAgel for promoting wound healing. Overall, the DNAgel band-aid with great hemostatic capacity is a promising candidate for rapid hemostasis and wound healing.

An adhesion-switchable hydrogel dressing for painless dressing removal without secondary damage

Hydrogels with strong adhesion to wet tissues are considered promising for wound dressings. However, the clinical application of adhesive hydrogel dressing remains a challenge due to the issues of secondary damage during dressing changes. Herein, we fabricated an adhesion-switchable hydrogel formed with poly(acrylamide)-co-poly(N-isopropyl acrylamide), quaternary ammonium chitosan and tannic acid. This hydrogel forms instant and robust adhesion to the skin at body temperature. However, as the temperature rises above the lower critical solution temperature (LCST), the hydrogel loses its adhesion towards the wound area due to the temperature-dependent volume phase transition of the copolymer, occurring around 45 °C. Consequently, the designed hydrogel can be easily detached from adhered tissues upon demand, providing a facile and effective method for painless dressing changes without secondary damage. This hydrogel holds great promise for long-term application in wound dressings.

Advances of biological macromolecules hemostatic materials: A review

Achieving hemostasis is a necessary intervention to rapidly and effectively control bleeding. Conventional hemostatic materials currently used in clinical practice may aggravate the damage at the bleeding site due to factors such as poor adhesion and poor adaptation. Compared to most traditional hemostatic materials, polymer-based hemostatic materials have better biocompatibility and offer several advantages. They provide a more effective method of stopping bleeding and avoiding additional damage to the body in case of excessive blood loss. Various hemostatic materials with greater functionality have been developed in recent years for different organs using diverse design strategies. This article reviews the latest advances in the development of polymeric hemostatic materials. We introduce the coagulation cascade reaction after bleeding and then discuss the hemostatic mechanisms and advantages and disadvantages of various polymer materials, including natural, synthetic, and composite polymer hemostatic materials. We further focus on the design strategies, properties, and characterization of hemostatic materials, along with their applications in different organs. Finally, challenges and prospects for the application of hemostatic polymeric materials are summarized and discussed. We believe that this review can provide a reference for related research on hemostatic materials, contributing to the further development of polymer hemostatic materials.

Chitosan catechol-tannic acid composite hydrogel and cryogel with antimicrobial and hemostatic properties

Hydrogels containing catechol group have received attention in the biomedical field due to their robust adhesive/cohesive capabilities, biocompatibility, and hemostatic abilities. Catechol-functionalized chitosan holds promise for preparing self-assembly hydrogels. However, issues of inefficient gelation and instability still persist in these hydrogels. In the current study, we synthesized chitosan catechol (CC) of high catechol substitution (∼28 %) and combined CC with tannic acid (TA, which also contains catechol) to form self-healing CC-TA hydrogels. The catechol-enriched CC-TA composite hydrogels showed rapid gelation and mechanical reinforcement (shear modulus ∼110 Pa). In situ coherent small-angle X-ray scattering (SAXS) coupled with rheometry revealed a morphological feature of mesoscale clusters (∼20 nm) within CC-TA hydrogel. The clusters underwent dynamic destruction under large-amplitude oscillatory shear, corresponding with the strain-dependent and self-healing behavior of the CC-TA hydrogel. The composite hydrogel had osmotic-responsive and notable adhesive properties. Meanwhile, CC-TA composite cryogel prepared simply through freeze-thawing procedures exhibited distinctive macroporous structure (∼200 μm), high water swelling ratio (∼7000 %), and favorable compressive modulus (∼8 kPa). The sponge-like cryogel was fabricated into swabs, demonstrating hemostatic capacity. The CC-TA composites, in both hydrogel and cryogel forms, possessed ROS scavenging ability, antimicrobial activity, and cell compatibility with potentials in biological applications.

Development of bovine serum albumin-modified Fe3O4 embedded in porous α-ketoglutaric acid/chitosan (BSA/Fe3O4@KA/CS): A magnetically targeted hemostatic dressing for deep and irregular wounds

Severe bleeding from deep and irregular wounds poses a significant challenge in prehospital and surgical settings. To address this issue, we developed a novel chitosan-based hemostatic dressing with a magnetic targeting mechanism using Fe3O4, termed bovine serum albumin-modified Fe3O4 embedded in porous α-ketoglutaric acid/chitosan (BSA/Fe3O4@KA/CS). This dressing enhances hemostasis by magnetically guiding the agent to the wound site. In vitro, the hemostatic efficacy of BSA/Fe3O4@KA/CS is comparable to that of commercial chitosan (Celox™) and is not diminished by the modification. In vivo, BSA/Fe3O4@KA/CS demonstrated superior hemostatic performance and reduced blood loss compared to Celox™. The hemostatic mechanism of BSA/Fe3O4@KA/CS includes the concentration of solid blood components through water absorption, adherence to blood cells, and activation of the endogenous coagulation pathway. Magnetic field targeting is crucial in directing the dressing to deep hemorrhagic sites. Additionally, safety assessments have confirmed the biocompatibility and biodegradability of BSA/Fe3O4@KA/CS. In conclusion, we introduce a novel approach to modify chitosan using magnetic guidance for effective hemostasis, positioning BSA/Fe3O4@KA/CS as a promising candidate for managing various wounds.

Expansion-clotting chitosan fabrics based on unidirectional fast-absorption fibers for rapid hemorrhage control

The rapid absorption of water from the blood to concentrate erythrocytes and platelets, thus triggering quick closure, is important for hemostasis. Herein, expansion-clotting chitosan fabrics are designed and fabricated by ring spinning of polylactic acid (PLA) filaments as the core layer and highly hydrophilic carboxyethyl chitosan (CECS) fibers as the sheath layer, and subsequent knitting of obtained PLA@CECS core spun yarns. Due to the unidirectional fast-absorption capacity of CECS fibers, the chitosan fabrics can achieve erythrocytes and platelets aggregate quickly by concentrating blood, thus promoting the formation of blood clots. Furthermore, the loop structure of coils formed in the knitted fabric can help them to expand by absorbing water to close their pores, providing effective sealing for bleeding. Besides, They have enough mechanical properties, anti-penetrating ability, and good tissue-adhesion ability in wet conditions, which can form a physical barrier to resist blood pressure during hemostasis and prevent them from falling off the wound, thus enhancing hemostasis synergistically. Therefore, the fabrics exhibit superior hemostatic performance in the rabbit liver, spleen, and femoral artery puncture injury model compared to the gauze group. This chitosan fabric is a promising hemostatic material for hemorrhage control.

Fabrication and characteristics of multifunctional hydrogel dressings using dopamine modified hyaluronic acid and phenylboronic acid modified chitosan

The healing of damaged skin is a complex and dynamic process, and the multi-functional hydrogel dressings could promote skin tissue healing. This study, therefore, explored the development of a composite multifunctional hydrogel (HDCP) by incorporating the dopamine modified hyaluronic acid (HA-DA) and phenylboronic acid modified chitosan (CS-PBA) crosslinked using boric acid ester bonds. The integration of HA-DA and CS-PBA could be confirmed using the Fourier transform infrared spectrometer and 1H nuclear magnetic resonance analyses. The fabricated HDCP hydrogels exhibited porous structure, elastic solid behavior, shear-thinning, and adhesion properties. Furthermore, the HDCP hydrogels exhibited antibacterial efficacy against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Subsequently, the cytocompatibility of the HDCP hydrogels was verified through CCK-8 assay and fluorescent image analysis following co-cultivation with NIH-3T3 cells. This research presents an innovative multifunctional hydrogel that holds promise as a wound dressing for various applications within the realm of wound healing.

Synthesis and characterization of thermosensitive 2-hydroxypropyl-trimethylammonium chitin and its antibacterial sponge for noncompressible hemostasis and tissue regeneration

Noncompressible hemorrhage is a leading cause of preventable death in battlefield/civilian trauma. The development of novel injectable and biodegradable hemostatic sponges, with rapid shape recovery and excellent antibacterial activity that can control hemorrhage in noncompressible bleeding sites and promote in situ tissue regeneration is still urgently needed. In this study, thermo/pH sensitive 2-hydroxypropyl-trimethylammonium chitins (QCHs) with low degree of quaternization substitution (DS: 0.07-0.23) and high degree of acetylation (DA: 0.91-0.94) were synthesized homogeneously for the first time. Their chemical compositions including DS and DA were characterized accurately by proton NMR for the first time. High strength QCH based sponges with good water/blood absorbency, rapid shape recovery and good antibacterial activity were prepared without using any crosslinkers but only due to their thermosensitive property, since they are soluble at low temperature but insoluble at high temperature. Compared with commercial products, the QCH sponges with cationic groups had the stronger pro-coagulant ability, better hemostatic effect in normal/heparinized liver perforation and femoral artery models in rats and porcine subclavian arteriovenous resection model. Moreover, the porous structure and biodegradability of the QCH sponges could promote in situ tissue regeneration. Overall, the QCH sponges show great clinical translational potential for noncompressible hemorrhage and tissue regeneration.

Nitric oxide-releasing photocrosslinked chitosan cryogels

The highly porous morphology of chitosan cryogels, with submicrometric-sized pore cell walls, provides a large surface area which leads to fast water absorption and elevated swelling degrees. These characteristics are crucial for the applications of nitric oxide (NO) releasing biomaterials, in which the release of NO is triggered by the hydration of the material. In the present study, we report the development of chitosan cryogels (CS) with a porous structure of interconnected cells, with wall thicknesses in the range of 340-881 nm, capable of releasing NO triggered by the rapid hydration process. This property was obtained using an innovative strategy based on the functionalization of CS with two previously synthesized S-nitrosothiols: S-nitrosothioglycolic acid (TGA(SNO)) and S-nitrosomercaptosuccinic acid (MSA(SNO)). For this purpose, CS was previously methacrylated with glycidyl methacrylate and subsequently submitted to photocrosslinking and freeze-drying processes. The photocrosslinked hydrogels thus obtained were then functionalized with TGA(SNO) and MSA(SNO) in reactions mediated by carbodiimide. After functionalization, the hydrogels were frozen and freeze-dried to obtain porous S-nitrosated chitosan cryogels with high swelling capacities. Through chemiluminescence measurements, we demonstrated that CS-TGA(SNO) and CS-MSA(SNO) cryogels spontaneously release NO upon water absorption at rates of 3.34 × 10-2 nmol mg-1 min-1 and 1.27 × 10-1 nmol mg-1 min-1, respectively, opening new perspectives for the use of CS as a platform for localized NO delivery in biomedical applications.

Polyvinyl alcohol/chitosan quaternary ammonium salt composite hydrogel with directional macroporous structure for photothermal synergistic antibacterial and wound healing promotion

After skin tissue trauma, wound infections caused by bacteria posed a great threat to skin repair. However, resistance to antibiotics, the current treatment of choice for bacterial infections, greatly affected the efficiency of anti-infection and wound healing. Therefore, there has been a critical need for the development of novel antimicrobial materials and advanced therapeutic methods to aid in skin repair. In this paper, rGO-PDA@ZIF-8 nanofillers were prepared by coating graphene oxide (GO) with dopamine (DA), followed by in situ growth of zeolite imidazolate framework-8 (ZIF-8). Using polyvinyl alcohol (PVA) and chitosan quaternary ammonium salt (CS) as matrix materials, along with polyethylene glycol (PEG) as a pore-forming agent, and rGO-PDA@ZIF-8 as an antimicrobial nano-filler, we successfully prepared rGO-PDA@ZIF-8/PVA/CS composite hydrogels with a directional macroporous structure using bidirectional freezing method and phase separation technique. This hydrogel exhibited excellent mechanical properties, good solubility and water retention capabilities. In addition, the hydrogel demonstrated excellent biocompatibility. Most notably, it not only exhibited excellent bactericidal effect against E. coli and S. aureus (99.1 % and 99.0 %, respectively) under the synergistic effect of intrinsic antibacterial activity and photothermal antibacterial, but also exhibited the ability to promote wound healing, making it a promising candidate for wound healing applications.

Wet adhesive hydrogels based on niobium carbide for experimental research of oral mucosal impairment

Oral mucosal impairment is a prevalent oral disease that frequently causes pain for patients. Conventional treatments have limited effectiveness and can cause adverse reactions. Furthermore, the moist and dynamic nature of the oral mucosal environment makes persistent adherence of conventional materials challenging, which can affect treatment efficacy. In this study, we investigated the potential of a NbC/TA-GelMA hydrogel system, where niobium carbide (NbC) and tannic acid (TA) were added to gelatin methacryloyl (GelMA), for repairing oral mucosal impairment. The wet adhesion properties of NbC/TA-GelMA hydrogels were confirmed by the inclusion of TA with a catechol-rich group. In addition, the photothermal effect of NbC/TA-GelMA hydrogel under near-infrared light, synergizing with TA, provided sustained antibacterial action. Furthermore, the NbC/TA-GelMA hydrogel effectively healed damaged oral mucosa of rats.

Injectable Bioadhesive Photocrosslinkable Hydrogels with Sustained Release of Kartogenin to Promote Chondrogenic Differentiation and Partial-Thickness Cartilage Defects Repair

Partial-thickness cartilage defect (PTCD) is a common and formidable clinical challenge without effective therapeutic approaches. The inherent anti-adhesive characteristics of the extracellular matrix within cartilage pose a significant impediment to the integration of cells or biomaterials with the native cartilage during cartilage repair. Here, an injectable photocrosslinked bioadhesive hydrogel, consisting of gelatin methacryloyl (GM), acryloyl-6-aminocaproic acid-g-N-hydroxysuccinimide (AN), and poly(lactic-co-glycolic acid) microspheres loaded with kartogenin (KGN) (abbreviated as GM/AN/KGN hydrogel), is designed to enhance interfacial integration and repair of PTCD. After injected in situ at the irregular defect, a stable and robust hydrogel network is rapidly formed by ultraviolet irradiation, and it can be quickly and tightly adhered to native cartilage through amide bonds. The hydrogel exhibits good adhesion strength up to 27.25 ± 1.22 kPa by lap shear strength experiments. The GM/AN/KGN hydrogel demonstrates good adhesion, low swelling, resistance to fatigue, biocompatibility, and chondrogenesis properties in vitro. A rat model with PTCD exhibits restoration of a smoother surface, stable seamless integration, and abundant aggrecan and type II collagen production. The injectable stable adhesive hydrogel with long-term chondrogenic differentiation capacity shows great potential to facilitate repair of PTCD.

Enteromorpha Prolifera Polysaccharide-Derived Injectable Hydrogel for Fast Intraoperative Hemostasis and Accelerated Postsurgical Wound Healing Following Tumor Resection

Intraoperative bleeding and delayed postsurgical wound healing caused by persistent inflammation can increase the risk of tumor recurrence after surgical resection. To address these issues, Enteromorpha prolifera polysaccharide (PEP) with intrinsic potentials for hemostasis and wound healing, is chemically modified into aldehyde-PEP and hydrazine-PEP. Thereby, an injectable double-network hydrogel (OPAB) is developed via forming dual dynamic bonding of acylhydrazone bonds between the decorated aldehyde and hydrazine groups and hydrogen bonds between hydroxyl groups between boric acid and PEP skeletons. The OPAB exhibits controllable shape-adaptive gelation (35.0 s), suitable mechanical properties, nonstimulating self-healing (60 s), good wet tissue adhesion (30.9 kPa), and pH-responsive biodegradability. For in vivo models, owing to these properties, OPAB can achieve rapid hemostasis within 30 s for the liver hemorrhage, and readily loading of curcumin nanoparticles to remarkably accelerate surgical wound closure by alleviating inflammation, re-epithelialization, granulation tissue formation, and collagen deposition. Overall, this multifunctional injectable hydrogel is a promising material that facilitates simultaneous intraoperative hemorrhage and postsurgical wound repair, holding significant potential in the clinical managements of bleeding and surgical wounds for tumor resection.

Platelet rich fibrin and simvastatin-loaded pectin-based 3D printed-electrospun bilayer scaffold for skin tissue regeneration

Designing multifunctional wound dressings is a prerequisite to prevent infection and stimulate healing. In this study, a bilayer scaffold (BS) with a top layer (TL) comprising 3D printed pectin/polyacrylic acid/platelet rich fibrin hydrogel (Pec/PAA/PRF) and a bottom nanofibrous layer (NL) containing Pec/PAA/simvastatin (SIM) was produced. The biodegradable and biocompatible polymers Pec and PAA were cross-linked to form hydrogels via Ca2+ activation through galacturonate linkage and chelation, respectively. PRF as an autologous growth factor (GF) source and SIM together augmented angiogenesis and neovascularization. Because of 3D printing, the BS possessed a uniform distribution of PRF in TL and an average fiber diameter of 96.71 ± 18.14 nm was obtained in NL. The Young's modulus of BS was recorded as 6.02 ± 0.31 MPa and its elongation at break was measured as 30.16 ± 2.70 %. The wound dressing gradually released growth factors over 7 days of investigation. Furthermore, the BS significantly outperformed other groups in increasing cell viability and in vivo wound closure rate (95.80 ± 3.47 % after 14 days). Wounds covered with BS healed faster with more collagen deposition and re-epithelialization. The results demonstrate that the BS can be a potential remedy for skin tissue regeneration.

What else should hemostatic materials do beyond hemostasis: A review

Massive blood loss due to injury is the leading cause of prehospital deaths in disasters and emergencies. Hemostatic materials are used to realize rapid hemostasis and protect patients from death. Researchers have designed and developed a variety of hemostatic materials. However, in addition to their hemostatic effect, hemostatic materials must be endowed with additional functions to meet the practical application requirements in different scenarios. Here, strategies for modifications of hemostatic materials for use in different application scenarios are listed: effective positioning at the site of deep and narrow wounds to stop bleeding, resistance to high blood pressure and wound movement to maintain wound formation, rapid and easy removal from the wound without affecting further treatment after hemostasis is completed, and continued function when retained in the wound as a dressing (such as antibacterial, antiadhesion, tissue repair, etc.). The problems encountered in the practical use of hemostatic materials and the strategies and progress of researchers will be further discussed in this review. We hope to provide valuable references for the design of more comprehensive and practical hemostatic materials.

MXene-based polysaccharide aerogel with multifunctional enduring antimicrobial effects for infected wound healing

Wound infection is a predominant etiological factor contributing to delayed wound healing in open wounds. Hence, it holds paramount clinical significance to devise wound dressings endowed with superior antibacterial properties. In this study, a Schiff base-crosslinked aerogel comprising sodium alginate oxide (OSA), carboxymethyl chitosan (CMCS), and Nb2C@Ag/PDA (NAP) was developed. The resultant OSA/CMCS-Nb2C@Ag/PDA (OC/NAP) composite aerogel exhibited commendable attributes including exceptional swelling characteristics, porosity, biocompatibility, and sustained antimicrobial efficacy. In vitro antimicrobial assays unequivocally demonstrated that the OC/NAP composite aerogel maintained nearly 100 % inhibition of Staphylococcus aureus and Escherichia coli under an 808 nm laser even after 25 h. Crucially, the outcomes of in vivo infected wound healing experiments demonstrated that the wound healing rate of the OC/NAP composite aerogel group reached approximately 100 % within a span of 14 days, which was significantly greater than that of the blank control group. In vitro and in vivo hemostatic experiments also revealed that the composite aerogel had excellent hemostatic properties. The results of this study demonstrate the remarkable potential of OC/NAP aerogel as a multifunctional clinical wound dressing, especially for infected wounds.

Shape memory and hemostatic silk-laponite scaffold for alveolar bone regeneration after tooth extraction trauma

Persistent bleeding and the absence of alveolar bone stress following tooth loss can hinder socket healing, complicating future dental implant procedures, and potentially leading to neighboring tooth instability. Therefore, developing materials that promote alveolar bone regeneration and possess both hemostatic and osteogenic properties is crucial for preserving the extraction sites. This study introduces a silk-based laponite composite scaffold material with proficient hemostatic and osteogenic functions, and excellent shape-memory properties for efficient extraction- site filling. In vitro studies research demonstrated that the scaffold's inherent negative charge of the scaffold significantly enhanced blood coagulation and thrombin generation. Moreover, its porous structure and slightly rough inner surface promoted blood cell adhesion and, improved the hemostatic performance. Furthermore, the scaffold facilitated stem cell osteogenic differentiation by activating the TRPM7 channel through the released of magnesium ions. In vivo tests using rat models confirmed its effectiveness in promoting coagulation and mandibular regeneration. Thus, this study proposes a promising approach for post-extraction alveolar bone regenerative repair. The composite scaffold material, with its hemostatic and osteogenic capabilities and shape-memory features, can potentially enhance dental implant success and overall oral health.

Recent advances of chitosan as a hemostatic material: Hemostatic mechanism, material design and prospective application

Uncontrolled hemorrhage arising from surgery or trauma may cause morbidity and even mortality. Therefore, facilitating control of severe bleeding is imperative for health care worldwide. Among diverse hemostatic materials, chitosan (CS) is becoming the most promising material owing to its non-toxic feature, as well as inherently hemostatic performance. However, further enhancing hemostatic property of CS-based materials without compromising more beneficial functions remains a challenge. In this review, representative hemostatic mechanisms of CS-based materials are firstly discussed in detail, mostly including red blood cells (RBCs) aggregation, platelet adherence and aggregation, as well as interaction with plasma proteins. Also, various forms (involving powder/particle, sponge, hydrogel, nanofiber, and other forms) of CS-based hemostatic materials are systematically summarized, mainly focusing on their design and preparation, characteristics, and comparative analysis of various forms. In addition, varied hemostatic applications are described in detail, such as skin wound hemostasis, liver hemostasis, artery hemostasis, and heart hemostasis. Finally, current challenges and future directions of functional design of CS-based hemostatic materials in diverse hemostatic applications are proposed to inspire more intensive researches.

Progress of polysaccharide-based tissue adhesives

Recently, polymer-based tissue adhesives (TAs) have gained the attention of scientists and industries as alternatives to sutures for sealing and closing wounds or incisions because of their ease of use, low cost, minimal tissue damage, and short application time. However, poor mechanical properties and weak adhesion strength limit the application of TAs, although numerous studies have attempted to develop new TAs with enhanced performance. Therefore, next-generation TAs with improved multifunctional properties are required. In this review, we address the requirements of polymeric TAs, adhesive characteristics, adhesion strength assessment methods, adhesion mechanisms, applications, advantages and disadvantages, and commercial products of polysaccharide (PS)-based TAs, including chitosan (CS), alginate (AL), dextran (DE), and hyaluronic acid (HA). Additionally, future perspectives are discussed.

Facile Bond Exchanging Strategy for Engineering Wet Adhesion and Antioxidant/Antibacterial Thin Layer over a Dynamic Hydrogel via the Carbon Dots Derived from Tannic Acid/ε-Polylysine

Adhesive hydrogels, playing an essential role in stretchable electronics, soft robotics, tissue engineering, and so forth, upon functioning often need to adhere to various substrates in wet conditions and simultaneously exhibit antibacterial/antioxidant properties while possessing the intrinsic stretchability and elasticity of the hydrogel network intact. Therefore, simple approaches to conveniently access adhesive hydrogels with multifunctional surfaces are being pursued. Herein, a facile strategy has been proposed to construct multifunctional adhesive hydrogels via surface engineering of a multifunctional carbon dot (CD)-decorated polymeric thin layer by dynamic bond exchange. By this strategy, a double cross-linked network hydrogel of polyacrylamide (PAM) and oxidized dextran (ODA) was engineered with a unique dense layer over the Schiff base hydrogel matrix by aqueous solution immersion of PA-120, versatile CDs derived from tannic acid (TA) and ε-polylysine (PL). Without any additional agents, the PA-120 CDs with residual polyphenolic/catechol and amine moieties were incorporated into the surface structure of the hydrogel network by the combined action of the Schiff base and hydrogen bonds to form a dense surface layer that can exhibit high wet adhesive performance via the amine-polyphenol/catechol pair. The armor-like dense architecture also endowed hydrogels with considerably enhanced tensile/compression properties and excellent antioxidant/antibacterial abilities. Besides, the single-sided modified Janus hydrogel and completely surface-modified hydrogel can be flexibly developed through this approach. This strategy will provide new insights into the preparation and application of surface-modified hydrogels featuring multiple functions and tunable interfacial properties.

Electrospun nanofiber membranes for rapid liver hemostasis via N-alkylated chitosan doped chitosan/PEO

The ideal hemostatic agents should be able to stop bleeding quickly and avoid secondary bleeding caused by adhesion with blood clots during dressing change. Herein, a hydrophobic electrospun nanofiber membrane was prepared for achieving hemostasis, rationally targeting both attributes, via doping N-alkylated chitosan (N-CS) grafted with octadecyl into chitosan/polyethylene oxide (PEO). In vitro and in vivo coagulation tests showed that CPNs doped with small amounts of N-CS (CPN31) could significantly shorten hemostasis time and promote the formation of more stable and stronger blood clots. In particular, the whole blood clotting time of CPN31 (58.8 ± 2.2 s) was significantly lower than that of chitosan/PEO (CPN0) nanofiber membrane (67 ± 3.5 s) and the medical sterile gauze (86.7 ± 0.6 s). Furthermore, due to the hemophobic nature of CPNs, blood wetting of the dressing was severely limited and blood can coagulated at the site of liver injury in rats, thus reducing blood loss and allowing rapid removal of the dressing without triggering secondary hemorrhage. The CPN31 exhibited excellent hemostasis properties, easy to remove, blood compatibility, biocompatibility and promoting fibroblast proliferation properties. This hydrophobic CPNs is a promising biological adhesive for hemorrhage control.

Multifunctional alginate/polydeoxyribonucleotide hydrogels for promoting diabetic wound healing

A multifunctional alginate/PDRN hydrogel system by ionic crosslinking and the Schiff base reaction between oxidized alginate (OA) and PDRN was developed in the present study. Biocompatibility assessment of the PDRN-loaded OA hydrogels showed a significant enhancement in cell viability in human dermal fibroblast (HDF) cells. In addition, hydrogels showed migratory, anti-inflammatory, intracellular reactive oxygen species scavenging, and anti-apoptotic activities. In vivo studies using a streptozotocin-induced diabetic Wister rat model indicated that OA-4PDRN had the highest percentage of wound closure (96.1 ± 2.6 %) at day 14 compared to the control (79.0 ± 2.3 %) group. This was accompanied by up-regulation of vascular endothelial growth factor (VEGF), interleukin-10 (IL-10), and transforming growth factor-beta (TGF-β) accompanied by down-regulation of pro-inflammatory markers (IL-6, IL-1β). Following histopathological observations, PDRN-loaded OA hydrogel ensured tissue safety and induced wound healing with granular tissue formation, collagen deposition, re-epithelialization, and regeneration of blood vessels and hair follicles. The downregulation of inflammatory cytokines (CD68) and expression of angiogenesis-related cytokines (CD31) in wound sites revealed the suppression of inflammation and increased angiogenesis, ensuring skin tissue regeneration in diabetic wound healing. In conclusion, the findings suggest that PDRN-loaded OA hydrogel has enormous therapeutic potential as a diabetic wound dressing.

Recent Development and Applications of Polydopamine in Tissue Repair and Regeneration Biomaterials

The various tissue damages are a severe problem to human health. The limited human tissue regenerate ability requires suitable biomaterials to help damage tissue repair and regeneration. Therefore, many researchers devoted themselves to exploring biomaterials suitable for tissue repair and regeneration. Polydopamine (PDA) as a natural and multifunctional material which is inspired by mussel has been widely applied in different biomaterials. The excellent properties of PDA, such as strong adhesion, photothermal and high drug-loaded capacity, seem to be born for tissue repair and regeneration. Furthermore, PDA combined with different materials can exert unexpected effects. Thus, to inspire researchers, this review summarizes the recent and representative development of PDA biomaterials in tissue repair and regeneration. This article focuses on why apply PDA in these biomaterials and what PDA can do in different tissue injuries.

Melanin-Inspired Composite Materials: From Nanoarchitectonics to Applications

Synthetic melanin is a mimic of natural melanin analogue with intriguing properties such as metal-ion chelation, redox activity, adhesion, and broadband absorption. Melanin-inspired composite materials are formulated by assembly of melanin with other types of inorganic and organic components to target, combine, and build up the functionality, far beyond their natural capabilities. Developing efficient and universal methodologies to prepare melanin-based composite materials with unique functionality is vital for their further applications. In this review, we summarize three types of synthetic approaches, predoping, surface engineering, and physical blending, to access various melanin-inspired composite materials with distinctive structure and properties. The applications of melanin-inspired composite materials in free radical scavenging, bioimaging, antifouling, and catalytic applications are also reviewed. This review also concludes current challenges that must be addressed and research opportunities in future studies.

Double Cross-Linked Hydrogel Dressings Based on Triblock Copolymers Bearing Antifreezing, Antidrying, and Inherent Antibacterial Properties

Bacterial infections typically invade the living tissue of wounds, thereby aggravating the inflammatory response, delaying wound healing, or causing further complications. In this paper, the antibacterial hydrogel (PNVBA) with antifreezing and antidrying properties was prepared by a two-step method using N-isopropylacrylamide (NIPAM), 1-butyl-3-vinylimidazolium bromide (VBIMBr), and 3-acrylamidophenylboronic acid (AAPBA). PNVBA hydrogels exhibited a high adsorption capacity of 280 mg·g-1 for bovine serum albumin (BSA) and can adhere to the surface of different materials through ion-dipole or hydrogen-bonding interactions. Meanwhile, the PNVBA hydrogels exhibited high viscoelasticity and good adhesion after freezing at -20 °C or heating at 70 °C for 24 h with a sterilizing rate of up to 98% against multidrug-resistant (MDR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Moreover, a survival rate of up to 90% after incubation with L929 cells over 24 h was observed. Therefore, this inherent antibacterial hydrogel can be used as an excellent alternative material for wound dressings.

Multifunctional chitosan-based gel sponge with efficient antibacterial, hemostasis and strong adhesion

Developing wound dressings with solid adhesive properties that enable efficient, painless hemostasis and prevent wound infection remain a huge challenge. Herein, the tris(hydroxymethyl) methyl glycine-modified chitosan derivative (CTMG) was prepared and freeze-dried after simply adjusting the concentration of CTMG to obtain the chitosan-based gel sponge with desired multi-hollow structure, special antibacterial and biocompatibility. The adhesion strength on porcine skin was impressive up to 113 KPa, much higher than fibrin glue. It can withstand the pressure that far exceeds blood pressure. CTMG exhibits bacteriostatic abilities as demonstrated in a bacteriostatic assay, and alongside biocompatibility, as shown in cytotoxicity and hemolytic assays. Moreover, CTMG gel sponge showed hemostatic properties in both in vivo and in vitro hemostasis experiments. During an experiment on liver hemorrhage in rats, CTMG gel sponge proved to be more effective in controlling bleeding than other hemostatic sponges available on the market, indicating its promising hemostatic properties. CTMG gel sponge possesses the potential to function as a wound dressing and hemostatic material, making it suitable for various clinical applications.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

MXene-Decorated Nanofibrous Membrane with Programmed Antibacterial and Anti-Inflammatory Effects via Steering NF-κB Pathway for Infectious Cutaneous Regeneration

Although antibiotic is still the main choice for antibacteria both in hospital and community, phototherapy has become a possibly one of the alternative approaches in the treatment of microbe-associated infections nowadays because of its considerable potential in effective eradication of pathogenic bacteria. However, overwhelming reactive oxygen species (ROS) generated from phototherapy inevitably provoke an inflammatory response, complicating the healing process. To address this outstanding issue, a MXene-decorated nanofibrious is devised that not only yield localized heat but also elevate ROS levels under near-infrared laser exposure ascribed to the synergistic photothermal/photodynamic effect, for potent bacterial inactivation. After being further loaded with aspirin, the nanofibrous membranes exhibit benign cytocompatibility, boosting cell growth and suppressing the (nuclear factor kappa-B ( NF-κB) signaling pathways through RNA sequencing analysis, indicating an excellent anti-inflammatory effect. Interestingly, in vivo investigations also corroborate that the nanofibrous membranes accelerate infectious cutaneous regeneration by efficiently killing pathogenic bacteria, promoting collagen deposition, boosting angiogenesis, and dampening inflammatory reaction via steering NF-κB pathway. As envisaged, this work furnishes a decorated nanofibrous membrane with programmed antibacterial and anti-inflammatory effects for remedy of refractory bacteria-invaded wound regeneration.

Fabrication of Cu/ZnO-loaded chitosan hydrogel for an effective wound dressing material to advanced wound care and healing efficiency after caesarean section surgery

Wound infections and delayed complications after caesarean section surgical procedure to mothers would have a prevalence of discomfort, stress and dissatisfaction in the postpartum period. In this report, one-pot synthesis is used for the preparation of chitosan (CS)-based copper nanoparticles (nCu), which was used for the preparation of zinc oxide (ZnO) hydrogel as wound dressing materials after surgery. The antibacterial activity of (CS-nCu/ZnO) developed hydrogels was studied zone of inhibition, against gram-positive and gram-negative bacteria. The antibacterial activity of the CS-nCu/ZnO hydrogel demonstrated that nanoformulated hydrogel materials have provided excellent bactericidal action against clinically approved bacterial pathogens. The biocompatibility and in vitro wound healing potential of the developed wound closure materials were studied by MTT assay and wound scratch assay methods, respectively. The MTT assay and cell migration assay results demonstrated that CS-nCu/ZnO hydrogel material induces cell compatibility and effective cell proliferation ability. These findings suggest that the CS-nCu/ZnO hydrogel outperforms CS-ZnO in terms of wound healing and could be used as a wound closure material in caesarean section wound treatment.

Superporous soy protein isolate matrices as superabsorbent dressings for successful management of highly exuding wounds: In vitro and in vivo characterization

Soy protein isolate (SPI) has received widespread attention of the biomedical research community primarily due to its good biocompatibility, biodegradability, high availability and low cost. Herein, glutaraldehyde cross-linked microporous sponge-like SPI scaffolds were prepared using the cryogelation technique for tissue engineering applications. The prepared SPI scaffolds possess an interconnected porous structure with approximately 90% porosity and an average pore size in the range of 45-92 μm. The morphology, porosity, swelling capacity and degradation rate of the cryogels were found to be dependent on the concentration of polymer to crosslinking agent. All cryogels were found to be elastic and able to maintain physical integrity even after being compressed to one-fifth of their original length during cyclic compression analysis. These cryogels showed excellent mechanical properties, immediate water-triggered shape restoration and absorption speed. Furthermore, cryogels outperformed cotton and gauze in terms of blood clotting and blood cell adherence. The in vitro and in vivo studies demonstrated the potency of SPI scaffolds for skin tissue engineering applications. Our findings showed that crosslinking with glutaraldehyde had no detrimental effects on cell viability. In addition, an in vivo wound healing study in rats validated them as good potential wound dressing materials.

Preparation of Hydrophobic Cryogel Containing Hydroxyoxime Extractant and Its Extraction Properties of Cu(Ⅱ)

Hydrophobic cryogels with monolithic supermacropores based on poly-trimethylolpropane trimethacrylate (pTrim) containing 1-(2-Hydroxyl-5-nonyphenyl)ethanone oxime (LIX84-I) were successfully prepared by a cryo-polymerization technique using organic solvents with freezing points between room temperature and around 0 °C as solvents. The prepared cryogels were characterized in terms of macroscopic shape and porous structure. The cryogels had a monolithic supermacroporous structure and high contents of LIX84-I depending on the added amount of the extractant to the monomer solution. The amount of LIX84-I impregnated in the cryogel had a linear relationship with the added amount of LIX84-I in the monomer solution for cryo-polymerization. Cu(II) in the aqueous solution was immediately adsorbed into the cryogel containing LIX84-I.

Culture-Delivery Live Probiotics Dressing for Accelerated Infected Wound Healing

Probiotic therapy in infected wound healing is hindered by its low viability and colonization efficiency during treatments. Developing dressings that maintain metabolic activity and prevent the potential leakage of probiotics is imperative. Herein, a culture-delivery live probiotics hydrogel dressing is designed and synthesized, formed by gelatin modified with norbornene (GelNB) and sulfhydryl (GelSH), distributing Lactobacillus reuteri (L. reuteri)-laden alginate microspheres (AlgMPs). GelNB-GelSH hydrogel (GelNBSH) incorporating AlgMPs embedding L. reuteri (GelNBSH-L) possesses bioprintability and efficient polymerization that can maintain the activity of L. reuteri in situ, promote its proliferation, and limit its leakage. Thereby, GelNBSH-L achieved a sustainable antimicrobial effect against both S. aureus and E. coli (>90%). Above all, the results show that GelNBSH-L could ensure propitious viability and efficient antibacterial properties of probiotics, effectively inhibit the further development of bacterial infectious wounds and shorten the repair cycle, aiding in ameliorating future clinical probiotic biotherapy.

Injectable and photothermal antibacterial bacterial cellulose cryogel for rapid hemostasis and repair of irregular and deep skin wounds

For irregular and deep skin wounds, it's difficult for wound dressing to reach the injured site to achieve rapid hemostasis and provide wound protection. Bacterial cellulose (BC) has high strength and natural three-dimensional pore structure, which endows it shape recovery ability after absorbing blood when injected to the wound. Therefore, in the study, an injectable aldehyde bacterial cellulose/polydopamine (DBC/PDA) photothermal cryogel was prepared by oxidation polymerization method for hemostasis and repair of irregular and deep skin wounds. BC was oxidized by NaIO4 to form DBC and dopamine (DA) was introduced into DBC by reacting with the aldehyde group in DBC through Schiff base reaction. Under oxidation effect of NaIO4 and with freezing condition, water crystallization led to local aggregation of DA and DBC, and at the same time DA was oxidized to PDA and polymerized with DA on DBC. After the melting process, the porous cryogel was obtained. The introduction of PDA enhances the photothermal properties of DBC/PDA cryogel. DBC/PDA cryogel can kill most bacteria and provide wound protection under near-infrared light. In vitro and in vivo hemostatic tests show that the DBC/PDA cryogel can quickly absorb blood and stop bleeding. Combined with its good injectable, DBC/PDA cryogel can provide rapid hemostatic and protection in the face of irregular and deep skin wounds.

Injectable Antiswelling and High-Strength Bioactive Hydrogels with a Wet Adhesion and Rapid Gelling Process to Promote Sutureless Wound Closure and Scar-free Repair of Infectious Wounds

Developing injectable antiswelling and high-strength bioactive hydrogels with wet tissue adhesiveness and a rapid gelling process to meet the requirements for rapid hemostasis, sutureless wound closure, and scar-free repair of infected skin wounds continues to have ongoing challenges. Herein, injectable, antibacterial, and antioxidant hydrogel adhesives based on poly(citric acid-co-polyethylene glycol)-g-dopamine and amino-terminated Pluronic F127 (APF) micelles loaded with astragaloside IV (AS) are prepared. The H2O2/horseradish peroxidase (HRP) system is used to cause cross-linking of the hydrogel network through oxidative coupling between catechol groups and chemical cross-linking between the catechol group and the amino group. The hydrogels exhibit a rapid gelling process, high mechanical strength, an antiswelling effect, good antioxidant property, H2O2 release behavior, and degradability. In addition, the hydrogels present good wet tissue adhesiveness, high bursting pressure, excellent antibacterial activity, long-term sustained release of AS, and good biocompatibility. The hydrogels perform good hemostasis on mouse liver, rat liver, and rabbit femoral vein bleeding models and achieve much better closure and healing of skin incisions than biomedical glue and surgical sutures. Furthermore, the hydrogel dressing significantly improved the scar-free repair of MRSA-infected full thickness skin defect wounds by modulating inflammation, regulating the ratio of collagen I/III, and improving the vascularization and granulation tissue formation. Thus, AS-loaded hydrogels show huge potential as multifunctional dressings for in vivo hemostasis, sutureless wound closure, and scar-free repair of infected skin wounds.

Wool keratin/zeolitic imidazolate framework-8 composite shape memory sponge with synergistic hemostatic performance for rapid hemorrhage control

Uncontrollable hemorrhage and subsequent wound infection pose severe threats to life, especially in the case of deep, non-compressible, massive bleeding. Here, a wool keratin/zeolitic imidazolate framework-8 (WK/ZIF-8) composite shape memory sponge is prepared by incorporating ZIF-8 nanoparticles into wool keratin. The combination of keratin and ZIF-8 particles not only reduces the effect of ZIF-8 particles on cell viability but also bolsters the mechanical properties of the keratin sponge and endows it with antibacterial efficacy. Due to the synergistic effect of the excellent hemostatic performance of keratin and Zn2+ release from ZIF-8 nanoparticles, the porous structure suitable for blood cell adhesion and the shape recovery ability of sponges, the WK/ZIF-8 composite sponge exhibits superior hemostatic performance to commercial medical sponges in SD rat and rabbit hemorrhage models. In addition, in vitro and in vivo antibacterial experiments demonstrate the anti-infection activity of the composite sponge. Overall, the WK/ZIF-8 composite sponge provides a promising approach to rapidly control bleeding and promote wound healing.

The Antimicrobial, Hemostatic, and Anti-Adhesion Effects of a Peptide Hydrogel Constructed by the All-d-Enantiomer of Antimicrobial Peptide Jelleine-1

Peptide hydrogels are believed to be potential biomaterials with wide application in the biomedical field because of their good biocompatibility, injectability, and 3D printability. Most of the previously reported polypeptide hydrogels are composed of l-peptides, while the hydrogels formed by self-assembly of d-peptides are rarely reported. Herein, a peptide hydrogel constructed by D-J-1, which is the all-d-enantiomer of antimicrobial peptide Jelleine-1 (J-1) is reported. Field emission scanning electron microscope (FE-SEM) and rheologic study are performed to characterize the hydrogel. Antimicrobial, hemostatic, and anti-adhesion studies are carried out to evaluate its biofunction. The results show that D-J-1 hydrogel is formed by self-assembly and cross-linking driven by hydrogen bonding, hydrophobic interaction, and π-π stacking force of aromatic ring in the structure of D-J-1. It exhibits promising antimicrobial activity, hemostatic activity, and anti-adhesion efficiency in a rat sidewall defect-cecum abrasion model. In addition, it also exhibits good biocompatibility. Notably, D-J-1 hydrogel shows improved in vitro and in vivo stability when compared with its l-enantiomer J-1 hydrogel. Therefore, the present study will provide new insight into the application of d-peptide hydrogel, and provides a new peptide hydrogel with antibacterial, hemostatic, and anti-adhesion efficacy for clinical use.

Double-Layer Hydrogel with Glucose-Activated Two-Stage ROS Regulating Properties for Programmed Diabetic Wound Healing

Slow healing of wounds induces great pain in diabetic patients. However, developing new approaches to promote diabetic wound healing is still one of the toughest challenges in the medical field. Here, we constructed a new double-layer hydrogel to effectively regulate reactive oxygen species (ROS) on the wound and promote diabetic wound healing. The inner layer contains glucose oxidase (Gox), ferrocene-modified quaternary ammonium chitosan (Fc-QCs), and poly(β-cyclodextrin) (Pβ-CD), which is used to generate hydroxyl radicals (•OH) for antibacterial in the early stage of wound healing and collapses gradually. The outer layer is composed of gelatin and dopamine. In the later stage of wound healing, the outer layer contacts the skin, which is beneficial for ROS clearance on the wound. Antibacterial, ROS scavenging, and wound healing experiments have shown that the double-layer hydrogel possesses two-stage ROS regulating properties for programmed diabetic wound healing. In conclusion, it will be one of the most potential dressings for treating diabetic wounds in the future.

Benzeneboronic-alginate/quaternized chitosan-catechol powder with rapid self-gelation, wet adhesion, biodegradation and antibacterial activity for non-compressible hemorrhage control

Although hemostatic powders have excellent adaptability for irregular and inaccessible wounds, their hemostasis for continuous bleeding or bleeding wounds of non-compressible organs remains a critical challenge. Herein, a series of benzeneboronic acid-modified sodium alginate/catechol-modified quaternized chitosan (SA-BA/QCS-C, SBQCC) powders is developed by borate ester crosslinking for non-compressible hemorrhage control. SBQCC powders possess remarkable tissue adhesion, rapid self-gelation, good cytocompatibility and antibacterial activity against S. aureus and E. coil. The blood coagulation assays show that SBQCC powders display excellent blood clotting ability due to the synergistic effect of SA-BA and QCS-C. The SBQCC2 powder with the SA-BA to QCS-C mass ratio of 5 to 3 has the greatest effect on the blood-clotting rate. Upon depositing SBQCC2 powder to bleeding wounds of rabbit liver, the powder can absorb a large amount of blood and form a stable hydrogel physical barrier at the bleeding wounds in situ to achieve non-pressing rapid hemostasis. The SBQCC2 powder also has good biocompatibility and can be degraded in vivo. Altogether, the SBQCC powders can be a promising candidate for rapid hemostasis, and these findings may provide a new perspective for improving the hemostatic efficiency of the hemostatic powder in biomedical fields.

Sea Cucumber-Inspired Aerogel for Ultrafast Hemostasis of Open Fracture

The symptomatic management of hemorrhagic shock complicated by open fractures is a great challenge, because it is also complicated by complex wound bleeding, bacterial infection, and bone defects. Inspired by the water absorption and cross-sectional microstructure of sea cucumbers, in this study, a new sea cucumber-like aerogel (GCG) is proposed. Its aligned porous structure and composition can stop bleeding rapidly and effectively with a blood clotting index of 3.73 ± 1.8%. More importantly, the data of in vivo hemostasis test in an amputating rat tail hemostatic model (15.69 ± 2.45 s, 26.95 ± 8.43 mg) and liver puncture bleeding model (23.77 ± 2.68 s, 36.22 ± 16.92 mg) also indicate the excellent hemostatic performance of GCG. In addition, GCG also shows a significant inhibitory effect on S. aureus and E. coli, which can prevent the occurrence of postoperative osteomyelitis. Not only that, after filling in the bone defect, it is shown that this GCG aerogel completely degrades eight weeks after surgery and induces new bone ingrowth, achieving functional regeneration after hemostasis of an open fracture defect. Generally, because of its combination of hemostatic, antibacterial, and osteogenic activities, this new aerogel is a promising option for open fractures treatment.

Tannic acid-Fe3+ dual catalysis induced rapid polymerization of injectable poly(lysine) hydrogel for infected wound healing

Infected wounds are difficult to heal because they are vulnerable to bacterial attacks, inflammatory responses, and oxidative stress. To promote the healing of infected wounds, we developed an injectable dual-network hydrogel TFAEP (TA-Fe, APS, EPL-GMA, PVA) based on ε-poly-l-lysine-graft-glycidyl methacrylate (EPL-GMA), polyvinyl alcohol (PVA), and tannic acid-iron (TA-Fe). TA-Fe formed a stable redox pair, which acted as a dual-autocatalytic system to activate ammonium persulfate, generate free radicals, and subsequently induce EPL-GMA polymerization. Then PVA formed hydrogen bonds with TA molecules. Here, TA-Fe not only simulated peroxidase to convert H2O2 into hydroxyl radicals (OH), but also exhibited good near-infrared photothermal conversion efficiency, which all endowed the hydrogel with excellent antibacterial ability. In addition, the hydrogel could remove excessive reactive oxygen species and reactive nitrogen species, alleviating oxidative stress and reducing inflammation response due to the presence of TA molecules. Moreover, the hydrogel showed good injectability and tissue adhesion, ensuring the close adhesion of the hydrogel to the wound and achieving the maximum function. In vivo experiments demonstrated that the hydrogel promoted infected wound healing by accelerating epidermal regeneration, promoting angiogenesis and collagen deposition, and facilitating the expression of anti-inflammatory factors.

Biological Macromolecule Hydrogel Based on Recombinant Type I Collagen/Chitosan Scaffold to Accelerate Full-Thickness Healing of Skin Wounds

The development of biological macromolecule hydrogel dressings with fatigue resistance, sufficient mechanical strength, and versatility in clinical treatment is critical for accelerating full-thickness healing of skin wounds. Therefore, in this study, multifunctional, biological macromolecule hydrogels based on a recombinant type I collagen/chitosan scaffold incorporated with a metal-polyphenol structure were fabricated to accelerate wound healing. The resulting biological macromolecule hydrogel possesses sufficient mechanical strength, fatigue resistance, and healing properties, including antibacterial, antioxygenic, self-healing, vascularization, hemostatic, and adhesive abilities. Chitosan and recombinant type I collagen formed the scaffold network, which was the first covalent crosslinking network of the hydrogel. The second physical crosslinking network comprised the coordination of a metal-polyphenol structure, i.e., Cu2+ with the catechol group of dopamine methacrylamide (DMA) and stacking of DMA benzene rings. Double-crosslinked networks are interspersed and intertwined in the hydrogel to reduce the mechanical strength and increase its fatigue resistance, making it more suitable for clinical applications. Moreover, the biological macromolecule hydrogel can continuously release Cu2+, which provides strong antibacterial and vascularization properties. An in vivo full-thickness skin defect model confirmed that multifunctional, biological macromolecule hydrogels based on a recombinant type I collagen/chitosan scaffold incorporated with a metal-polyphenol structure can facilitate the formation of granulation tissue and collagen deposition for a short period to promote wound healing. This study highlights that this biological macromolecule hydrogel is a promising acute wound-healing dressing for biomedical applications.

Double-crosslinked PNIPAM-based hydrogel dressings with adjustable adhesion and contractility

Rapid post-wound closure is necessary to avoid wound infection and promote scar-free healing when skin trauma occurs. In this study, new types of hydrogel dressings with adjustable contractility were fabricated based on N-isopropyl acrylamide/sodium alginate/graphene oxide (P/SA/GO). Then, the chitosan (CS) solution was used as a bridging polymer to achieve tissue adhesion to the hydrogel. The results show that the hydrogel based on poly(N-isopropyl acrylamide) (PNIPAM) not only has the ability to self-shrink but also can adjust the rate of shrinkage through near-infrared thermal stimulation. At the same time, high adhesion strength (7.86 ± 1.22 kPa) between the tissue and the dressing is achieved through the introduction of bridging polymers (CS), and the coating area of the bridging polymer can be adjusted to achieve regional adhesion. The mouse total skin defects experiments have shown that sutures-free wound closure in the early stages of wound healing could be obtained by adjusting the material temperature. Besides, the dressings can promote scar-free wound healing by reducing inflammatory cell infiltration and collagen deposition. These results indicate that double-crosslinked PNIPAM-based hydrogel dressings with adjustable adhesion and contractility proposed in this study provide a candidate material for achieving trackless wound healing.

Polymer nanomaterials for use as adjuvant surgical tools

Materials employed in the treatment of conditions encountered in surgical and clinical practice frequently face barriers in translation to application. Shortcomings can be generalized through their reduced mechanical stability, difficulty in handling, and inability to conform or adhere to complex tissue surfaces. To overcome an amalgam of challenges, research has sought the utilization of polymer-derived nanomaterials deposited in various fashions and formulations to improve the application and outcomes of surgical and clinical interventions. Clinically prevalent applications include topical wound dressings, tissue adhesives, surgical sealants, hemostats, and adhesion barriers, all of which have displayed the potential to act as superior alternatives to current materials used in surgical procedures. In this review, emphasis will be placed not only on applications, but also on various design strategies employed in fabrication. This review is designed to provide a broad and thought-provoking understanding of nanomaterials as adjuvant tools for the assisted treatment of pathologies prevalent in surgery. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.