Synthetic poly(vinyl alcohol)–chitosan as a new type of highly efficient hemostatic sponge with blood-triggered swelling and high biocompatibility

Repairing Exposed Tendon Wounds with Absorbable Gelatin Sponges and Autologous Split-Thickness Skin Grafts: A Case Series

ABSTRACT

Conventional flap repair surgery has several drawbacks, including operational complexity, donor site damage, and high risk. In this case series, the authors explored an alternative approach for repairing exposed tendon wounds caused by trauma using absorbable gelatin sponges (AGSs) and autologous thigh skin grafts. This report presents two cases of lower-extremity skin necrosis with tendon exposure following wound debridement. The treatment approach involved early debridement, negative-pressure wound therapy, and wound irrigation with 0.9% sodium chloride. Upon achieving controlled wound infection, AGSs were applied to the exposed tendon to prevent degeneration and promote wound healing. Subsequently, areas where granulation tissue failed to cover the tendon were repaired using AGSs and 0.25-mm-thick autologous mesh skin grafts harvested from the thigh. Complete wound healing was achieved in both cases, on the 20th and 12th day after skin grafting, respectively. The proposed method proved successful in repairing exposed tendon wounds, effectively preventing infection and necrosis.

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.

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.

Quaternized chitosan/oxidized bacterial cellulose cryogels with shape recovery for noncompressible hemorrhage and wound healing

Management of noncompressible torso hemorrhage is an urgent clinical requirement, desiring biomaterials with rapid hemostasis, anti-infection and excellent resilient properties. In this research, we have prepared a highly resilient cryogel with both hemostatic and antibacterial effects by chemical crosslinking and electrostatic interaction. The network structure crosslinked by quaternized chitosan and genipin was interspersed with oxidized bacterial cellulose after lyophilization. The as-prepared cryogel can quickly return to the original volume when soaking in water or blood. The appropriately sized pores in the cryogel help to absorb blood cells and further activate coagulation, while the quaternary ammonium salt groups on quaternized chitosan inhibit bacterial infections. Both cell and animal experiments showed that the cryogel was hypotoxic and could promote the regeneration of wound tissue. This research provides a new pathway for the preparation of double crosslinking cryogels and offers effective and safe biomaterials for the emergent bleeding management of incompressible wounds.

Surface modification strategies for improved hemocompatibility of polymeric materials: a comprehensive review

Polymeric biomaterials are a widely used class of materials due to their versatile properties. However, as with all other types of materials used for biomaterials, polymers also have to interact with blood. When blood comes into contact with any foreign body, it initiates a cascade which leads to platelet activation and blood coagulation. The implant surface also has to encounter a thromboinflammatory response which makes the implant integrity vulnerable, this leads to blood coagulation on the implant and obstructs it from performing its function. Hence, the surface plays a pivotal role in the design and application of biomaterials. In particular, the surface properties of biomaterials are responsible for biocompatibility with biological systems and hemocompatibility. This review provides a report on recent advances in the field of surface modification approaches for improved hemocompatibility. We focus on the surface properties of polysaccharides, proteins, and synthetic polymers. The blood coagulation cascade has been discussed and blood - material surface interactions have also been explained. The interactions of blood proteins and cells with polymeric material surfaces have been discussed. Moreover, the benefits as well as drawbacks of blood coagulation on the implant surface for wound healing purposes have also been studied. Surface modifications implemented by other researchers to enhance as well as prevent blood coagulation have also been analyzed.

Supramolecular hydrogels for wound repair and hemostasis

The unique network characteristics and stimuli responsiveness of supramolecular hydrogels have rendered them highly advantageous in the field of wound dressings, showcasing unprecedented potential. However, there are few reports on a comprehensive review of supramolecular hydrogel dressings for wound repair and hemostasis. This review first introduces the major cross-linking methods for supramolecular hydrogels, which includes hydrogen bonding, electrostatic interactions, hydrophobic interactions, host-guest interactions, metal ligand coordination and some other interactions. Then, we review the advanced materials reported in recent years and then summarize the basic principles of each cross-linking method. Next, we classify the network structures of supramolecular hydrogels before outlining their forming process and propose their potential future directions. Furthermore, we also discuss the raw materials, structural design principles, and material characteristics used to achieve the advanced functions of supramolecular hydrogels, such as antibacterial function, tissue adhesion, substance delivery, anti-inflammatory and antioxidant functions, cell behavior regulation, angiogenesis promotion, hemostasis and other innovative functions in recent years. Finally, the existing problems as well as future development directions of the cross-linking strategy, network design, and functions in wound repair and hemostasis of supramolecular hydrogels are discussed. This review is proposed to stimulate further exploration of supramolecular hydrogels on wound repair and hemostasis by researchers in the future.

A Post-marketing Surveillance, Single-Centric Study to Evaluate the Safety and Tolerability of VELNEZ as a Space-Occupying Dressing Pack After Ear Surgery

PURPOSE

The purpose of this study was to evaluate the safety and tolerability of VELNEZ (Datt Mediproducts Pvt. Ltd., New Delhi, India) as a space-occupying dressing for controlling hemorrhage after ear surgery.

METHOD

A total of 21 patients were included in an open-label, interventional, single-arm post-marketing surveillance study to investigate the safety and efficacy of the VELNEZ ear pack. The patients were questioned for collecting data related to the subject's safety and comfort, adverse events, site assessment, and otoscopic examination from discharge day to last follow-up (eight follow-up visits) at regular intervals. The standardized questionnaires for VELNEZ tolerability (pain/pressure effect, infection, and general satisfaction) were used after ear surgery.

RESULTS

 The average hemorrhage control time was 1.08 ± 0.16 minutes. None of the subjects reported moderate pain at any of the study visits following surgery. This biodegradable ear pack had an average disintegration time of 25.4 days in the ear cavity. No postoperative adverse events or serious adverse events were observed.

CONCLUSION

VELNEZ is safe and effective as a space-occupying dressing pack after ear surgery and is well-tolerated by patients.

Antibacterial and hemostatic chitin sponge directly constructed from Pleurotus Eryngii via top-down approach

Chitin, the second most abundant polysaccharide on earth, possesses unique characteristics, including biosafety, biodegradability, and procoagulant activity, making it an attractive material for hemostasis. However, the conventional bottom-up construction of chitin-based materials is intricate and time-consuming. In this study, we have developed a top-down strategy to prepare a 3D porous chitin-based hemostatic sponge with exceptional hemostatic properties and antibacterial activity, directly from the spongy Pleurotus eryngii. The top-down method involves deproteinization, in situ quaternization, and tannin acid crosslinking. The obtained sponge has an interconnected microporous structure with high porosity (89.7 ± 3.2 %), endowing it with high water absorption (2047 ± 105 %) and rapid water-triggered shape-memory behavior (< 2 s). The sponge exhibits superior blood coagulant activity and outperforms standard medical gauze, gelatin sponge, and chitosan sponge in both topical artery and non-compressive liver puncture wound. In addition, the sponge exhibited significant antibacterial activity against both gram-positive Staphylococcus aureus and gram-negative Escherichia coli. In summary, this study provides a straightforward and practical approach for constructing an antibacterial and hemostatic chitin sponge that could be a valuable option for treating bleeding wounds.

Marine-derived polysaccharides and their therapeutic potential in wound healing application - A review

Polysaccharides originating from marine sources have been studied as potential material for use in wound dressings because of their desirable characteristics of biocompatibility, biodegradability, and low toxicity. Marine-derived polysaccharides used as wound dressing, provide several benefits such as promoting wound healing by providing a moist environment that facilitates cell migration and proliferation. They can also act as a barrier against external contaminants and provide a protective layer to prevent further damage to the wound. Research studies have shown that marine-derived polysaccharides can be used to develop different types of wound dressings such as hydrogels, films, and fibres. These dressings can be personalised to meet specific requirements based on the type and severity of the wound. For instance, hydrogels can be used for deep wounds to provide a moist environment, while films can be used for superficial wounds to provide a protective barrier. Additionally, these polysaccharides can be modified to improve their properties, such as enhancing their mechanical strength or increasing their ability to release bioactive molecules that can promote wound healing. Overall, marine-derived polysaccharides show great promise for developing effective and safe wound dressings for various wound types.

Antibacterial chitosan-based composite sponge with synergistic hemostatic effect for massive haemorrhage

Uncontrollable acute bleeding and wound infection pose significant challenges in emergency treatment and surgical operations. Therefore, the research and development of highly efficient antibacterial hemostatic agents are of great importance in reducing the mortality rate among patients with massive hemorrhage. In this study, we utilized hydrophobically modified chitosan (HM-CS) and gallic acid chitosan (GA-CS) to create a composite sponge (HM/GA-CS) that exhibits complementary advantages. The composite sponge combines the alkyl chain and polyphenol structure, allowing it to adsorb blood cells and plasma proteins simultaneously. This synergistic effect was confirmed through various tests, including blood cell adhesion, plasma protein barrier behavior, and in vitro hemostatic testing. Furthermore, experiments conducted on a rat liver injury model demonstrated that the composite sponge achieved rapid coagulation within 52 s, resulting in significantly lower bleeding volume compared with traditional gauze. In addition, the incorporation of GA-CS into HM-CS enhanced the antibacterial properties of the composite sponge. The antibacterial rate of the composite sponge against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) reached 100 % and 98.2 %, respectively. To evaluate its biocompatibility, the composite sponge underwent blood compatibility and cell activity tests, confirming its suitability. The HM/GA-CS sponge holds promising applications in managing cases of massive hemorrhage.

A peptide-engineered alginate aerogel with synergistic blood-absorbing and platelet-binding capabilities to rapidly stop bleeding

Polysaccharide matrix infused with hemostasis-stimulating chemistry represents a critical medical need of bleeding management. Herein, we describe the development of a polysaccharide-peptide conjugate platform, an alginate engineered with fibrinogen-derived platelet-binding peptides (APE). The alginate backbone was found to allow for multivalent grafting of the peptides. Processing APE conjugate into crosslinked aerogels promoted platelet accumulation, leading to a significant reduction in the coagulation time of whole rabbit blood and improving the stability of the formed clot. The APE aerogels also exhibited a high porosity and fluid uptake capacity (>90 in weight ratio) as well as good biocompatibility in hemostasis. Furthermore, in vivo studies conducted in rat models of tail cut and hepatic hemorrhage showed that APE aerogels reduced bleeding time by >58 % and blood loss by >61 %. The platelet-enrichment capacity of the APE construct synergized by high absorbency in its aerogel form offers a prototype for customized polysaccharide hemostats.

Advances in haemostatic sponges: Characteristics and the underlying mechanisms for rapid haemostasis

In traumatized patients, the primary cause of mortality is uncontrollable continuous bleeding and unexpected intraoperative bleeding which is likely to increase the risk of complications and surgical failure. High expansion sponges are effective clinical practice for the treatment of wound bleeding (irregular/deep/narrow) that are caused by capillaries, veins and even arterioles as they possess a high liquid absorption ratio so can absorb blood platelets easily in comparison with traditional haemostasis treatments, which involve compression, ligation, or electrical coagulation etc. When in contact with blood, haemostatic sponges can cause platelet adhesion, aggregation, and thrombosis, preventing blood from flowing out from wounds, triggering the release of coagulation factors, causing the blood to form a stable polymerized fibre protein, forming blood clots, and achieving the goal of wound bleeding control. Haemostatic sponges are found in a variety of shapes and sizes. The aim of this review is to facilitate an overview of recent research around haemostatic sponge materials, products, and technology. This paper reviews the synthesis, properties, and characteristics of haemostatic sponges, together with the haemostasis mechanisms of haemostatic sponges (composite materials), such as chitosan, cellulose, gelatin, starch, graphene oxide, hyaluronic acid, alginate, polyethylene glycol, silk fibroin, synthetic polymers silver nanoparticles, zinc oxide nanoparticles, mesoporous silica nanoparticles, and silica nanoparticles. Also, this paper reviews commercial sponges and their properties. In addition to this, we discuss various in-vitro/in-vivo approaches for the evaluation of the effect of sponges on haemostasis.

Highly absorbent bio-sponge based on carboxymethyl chitosan/poly-γ-glutamic acid/platelet-rich plasma for hemostasis and wound healing

Stopping bleeding at an early stage and promoting wound healing are of great significance for efficient wound management. In this study, a carboxymethyl chitosan (CMCS)/poly-γ-glutamic acid (γ-PGA)/platelet-rich plasma (PRP) hydrogel (CP-PRP hydrogel) was firstly prepared by crosslinking of CMCS with γ-PGA and the enzymatic coagulation of PRP. Then, the CP-PRP hydrogel was freeze-dried and transformed into a sponge (CP-PRP sponge). A series of safety experiments with cells, blood, and tissues proved the biocompatibility of the CP-PRP sponge. Importantly, the CP-PRP sponge was able to adhere and condense red blood cells, which accelerated blood clotting. Therefore, the CP-PRP sponge showed an enhanced hemostasis effect compared to SURGIFLO® Hemostatic Matrix. Moreover, in vitro and in vivo experiments showed that the sponge was able to release epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF). Thus, in a mouse model of full-thickness skin defects, the wounds of the sponge-treated mice were significantly healed within two weeks. These results proved the transforming potential of the CP-PRP sponge as a novel bioactive wound dressing.

Recent Advances in Biodegradable and Biocompatible Synthetic Polymers Used in Skin Wound Healing

The treatment of skin wounds caused by trauma and pathophysiological disorders has been a growing healthcare challenge, posing a great economic burden worldwide. The use of appropriate wound dressings can help to facilitate the repair and healing rate of defective skin. Natural polymer biomaterials such as collagen and hyaluronic acid with excellent biocompatibility have been shown to promote wound healing and the restoration of skin. However, the low mechanical properties and fast degradation rate have limited their applications. Skin wound dressings based on biodegradable and biocompatible synthetic polymers can not only overcome the shortcomings of natural polymer biomaterials but also possess favorable properties for applications in the treatment of skin wounds. Herein, we listed several biodegradable and biocompatible synthetic polymers used as wound dressing materials, such as PVA, PCL, PLA, PLGA, PU, and PEO/PEG, focusing on their composition, fabrication techniques, and functions promoting wound healing. Additionally, the future development prospects of synthetic biodegradable polymer-based wound dressings are put forward. Our review aims to provide new insights for the further development of wound dressings using synthetic biodegradable polymers.

Interpenetrating network expansion sponge based on chitosan and plasma for ultrafast hemostasis of arterial bleeding wounds

Preventing arterial hemorrhage by intervening within the first few minutes is critical to the patient's life. Hemostatic materials have been developed over the last decades to address this issue, nevertheless these materials alone do not contribute to improve the survival effects in many extreme conditions, which is usually caused by penetrating arterial bleeding wounds that are incompressible and deep arterial bleeding with irregularly shapes. It is well known that, after calcium ion stimulation, many intriguing changes occurred in the major components of plasma, including the activation of several coagulation factors, such as the conversion of fibrinogen to fibrin, prothrombin to thrombin, and so on. Therefore, we constructed an expansion sponge with interpenetrating network based on chitosan and plasma, while various activated coagulation factors in plasma were also loaded into the pore structure of chitosan sponges. The prepared CS-PG sponge is capable of providing a simpler and more efficient method for treating high-pressure arterial bleeding wounds, which includes three steps: Rapid sealing and adhension, Thrombin catalysis and Activated autocoagulation. As the next generation bioactive materials, compared to conventional hemostatic materials, CS-PG sponge demonstrated superior hemostatic characteristics in both rabbit femoral artery damage and rat liver injury models.

Chitosan-based hemostatic sponges as new generation hemostatic materials for uncontrolled bleeding emergency: Modification, composition, and applications

The choice of hemostatic technique is a curial concern for surgery and as first-aid treatment in combat. To treat uncontrolled bleeding in complex wound environments, chitosan-based hemostatic sponges have attracted significant attention in recent years because of the excellent biocompatibility, degradability, hemostasis and antibacterial properties of chitosan and their unique sponge-like morphology for high fluid absorption rate and priority aggregation of blood cells/platelets to achieve rapid hemostasis. In this review, we provide a historical perspective on the use of chitosan hemostatic sponges as the new generation of hemostatic materials for uncontrolled bleeding emergencies in complex wounds. We summarize the modification of chitosan, review the current status of preparation protocols of chitosan sponges based on various composite systems, and highlight the recent achievements on the detailed breakdown of the existing chitosan sponges to present the relationship between their composition, physical properties, and hemostatic capacity. Finally, the future opportunities and challenges of chitosan hemostatic sponges are also proposed.

Fabrication of Fibrin/Polyvinyl Alcohol Scaffolds for Skin Tissue Engineering via Emulsion Templating

In the search for a novel and scalable skin scaffold for wound healing and tissue regeneration, we fabricated a class of fibrin/polyvinyl alcohol (PVA) scaffolds using an emulsion templating method. The fibrin/PVA scaffolds were formed by enzymatic coagulation of fibrinogen with thrombin in the presence of PVA as a bulking agent and an emulsion phase as the porogen, with glutaraldehyde as the cross-linking agent. After freeze drying, the scaffolds were characterized and evaluated for biocompatibility and efficacy of dermal reconstruction. SEM analysis showed that the formed scaffolds had interconnected porous structures (average pore size e was around 330 µm) and preserved the nano-scale fibrous architecture of the fibrin. Mechanical testing showed that the scaffolds' ultimate tensile strength was around 0.12 MPa with an elongation of around 50%. The proteolytic degradation of scaffolds could be controlled over a wide range by varying the type or degree of cross-linking and by fibrin/PVA composition. Assessment of cytocompatibility by human mesenchymal stem cell (MSC) proliferation assays shows that MSC can attach, penetrate, and proliferate into the fibrin/PVA scaffolds with an elongated and stretched morphology. The efficacy of scaffolds for tissue reconstruction was evaluated in a murine full-thickness skin excision defect model. The scaffolds were integrated and resorbed without inflammatory infiltration and, compared to control wounds, promoted deeper neodermal formation, greater collagen fiber deposition, facilitated angiogenesis, and significantly accelerated wound healing and epithelial closure. The experimental data showed that the fabricated fibrin/PVA scaffolds are promising for skin repair and skin tissue engineering.

Biomedical properties and hemostatic efficacy of polyvinyl alcohol (PVA) based hydrogel in experimental rat liver injury model

PURPOSE

Bleeding is a leading cause of mortality and morbidity in the trauma and surgery field, using effective hemostatic agents can help us reduce bleeding especially in parenchymal hemorrhage. Nowadays polyvinyl alcohol (PVA) is known as a safe candidate for wound dressing and maybe a hemostatic agent. PVA-based hydrogel is a popular biocompatible material in the biomedical field especially when it has high water absorption. In this study, we investigated the PVA hydrogel's mechanical and biological properties as well as its hemostatic potential in parenchymal bleeding.

METHODS

PVA hydrogel had made by the freeze-thawing approach, we used PVA hydrogel in comparison to standard treatment to investigate hemostatic potency. Also, we performed MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) tests to survey PVA cellular toxicity. After an acute liver injury, two groups of 12 rats were treated with PVA hydrogel or standard treatment with sterile gauze. The results including the time and volume of bleeding, and the time and survival rate of the rats were measured and compared.

RESULTS

We saw that PVA hydrogel was safe with no cellular toxicity in the MTT assay. Regarding efficacy, PVA hydrogel increased rats' survival after bleeding from 75% to 91.7%, and decreased bleeding time (p: 0.015), and bleeding volume (p: 0.03) compared to the control group.

CONCLUSION

Polyvinyl alcohol is safe. It has good biological properties with no cellular toxicity and has a significant hemostatic effect and can be regarded in control of parenchymal hemorrhage.

Inorganic-based biomaterials for rapid hemostasis and wound healing

The challenge for the treatment of severe traumas poses an urgent clinical need for the development of biomaterials to achieve rapid hemostasis and wound healing. In the past few decades, active inorganic components and their derived composites have become potential clinical products owing to their excellent performances in the process of hemorrhage control and tissue repair. In this review, we provide a current overview of the development of inorganic-based biomaterials used for hemostasis and wound healing. We highlight the methods and strategies for the design of inorganic-based biomaterials, including 3D printing, freeze-drying, electrospinning and vacuum filtration. Importantly, inorganic-based biomaterials for rapid hemostasis and wound healing are presented, and we divide them into several categories according to different chemistry and forms and further discuss their properties, therapeutic mechanisms and applications. Finally, the conclusions and future prospects are suggested for the development of novel inorganic-based biomaterials in the field of rapid hemostasis and wound healing.

Oxygen-releasing hydrogels promote burn healing under hypoxic conditions

Hypoxic nonhealing wounds are a common complication in chronic patients, and chronic hypoxia is the main reason for delayed wound healing, so local wound oxygenation may be an effective way to address this problem. Here, we proposed a system consisting of oxygen-releasing microsphere (GC) and self-healing hydrogel (QGO). QGO/GC hydrogel could promote survival, migration and tube formation of human umbilical vein endothelial cells under hypoxic conditions. Moreover, QGO/GC hydrogels exhibited biocompatibility in vitro and in vivo. The hypoxic mouse burn model further confirmed that QGO/GC hydrogel could promote tissue repair by reducing inflammation (TNF-α and IL-1β), increasing angiogenesis (CD31, VEGF and α-SMA) and collagen deposition. This study provided an effective oxygen-releasing hydrogel that could offer a simple and effective method for the clinical treatment of chronic hypoxic wounds. STATEMENT OF SIGNIFICANCE: Burn injury is caused by various exogenous factors such as friction, cold, radiations, electricity, chemicals, hot surfaces or liquids. Severe burn can damage the entire skin layer, and the healing process is delayed due to an unbalanced inflammatory response, excessive reactive oxygen species, lack of angiogenesis (insufficient nutrient and oxygen availability), and susceptibility to infection. In the present study, we proposed an oxygen-releasing hydrogel (QGO/GC). QGO/GC hydrogel could promote survival, migration, and tube formation of human umbilical vein endothelial cells under hypoxic conditions. And QGO/GC hydrogels could promote tissue repair by reducing inflammation, increasing angiogenesis and collagen deposition. This work provided an effective oxygen-releasing hydrogel for the clinical management of chronic hypoxic wounds.

Biocompatible Carboxymethyl Chitosan/GO-Based Sponge to Improve the Efficiency of Hemostasis and Wound Healing

Sponges with highly absorptive properties have been widely used in emergency hemostasis. Graphene oxide (GO) has been extensively investigated in biomedical applications and is a promising candidate for hemostatic sponges. However, GO has been demonstrated to have adverse effects on the human body. To overcome this problem, a hemostatic sponge based on modified GO and carboxymethyl chitosan (CMCS) is successfully prepared, which has excellent water absorption ability and mechanical strength. Importantly, hemostasis assays showed that the composite sponge exhibited high hemostatic efficiency, and the possible hemostatic mechanism is also discussed in this study. Moreover, the results of in vitro antibacterial tests reveal that the composite sponge also presents strong antimicrobial effects against Staphylococcus aureus and Escherichia coli. Significantly, the composited sponge used as hemostatic dressing can effectively promote cell proliferation, achieving a wound closure rate of 95% on day 12. Such a graphene-based sponge with multiple advantageous features would hold broad prospects in the hemostatic field.

Recent Advances of Chitosan Formulations in Biomedical Applications

Chitosan, a naturally abundant cationic polymer, is chemically composed of cellulose-based biopolymers derived by deacetylating chitin. It offers several attractive characteristics such as renewability, hydrophilicity, biodegradability, biocompatibility, non-toxicity, and a broad spectrum of antimicrobial activity towards gram-positive and gram-negative bacteria as well as fungi, etc., because of which it is receiving immense attention as a biopolymer for a plethora of applications including drug delivery, protective coating materials, food packaging films, wastewater treatment, and so on. Additionally, its structure carries reactive functional groups that enable several reactions and electrochemical interactions at the biomolecular level and improves the chitosan’s physicochemical properties and functionality. This review article highlights the extensive research about the properties, extraction techniques, and recent developments of chitosan-based composites for drug, gene, protein, and vaccine delivery applications. Its versatile applications in tissue engineering and wound healing are also discussed. Finally, the challenges and future perspectives for chitosan in biomedical applications are elucidated.

Photocatalytic and adsorptive performance of polyvinyl alcohol/chitosan/TiO2 composite for antibiotics removal: single- and multi-pollutant conditions

A polymer-TiO₂ macro composite (i.e., PVA-CS-TiO₂) was synthesized via chemical precipitation of PVA-CS-TiO₂ blend in alkali/solvent medium and applied for the removal of three model antibiotics (i.e., metronidazole (MNZ), ceftiofur (CEF) and tetracycline (TET)), as single compound and multi-compound conditions. The photocatalytic and adsorptive removals of antibiotics (concentrations of 0.1, 1 and 10 mg L^-1) by the composite in an UV reactor system (32 W UV-C power, 0.3 g L^-1 of composite) was assessed through kinetic models. Antibiotics adsorption followed pseudo-second-order kinetics, and the order of adsorption was MNZ > TET > CEF. On the other hand, the hydrophilic MNZ was degraded faster compared to hydrophobic CEF and TET drugs. Moreover, UV reactor system exhibited antagonistic behavior under multi-compound condition. Micro-toxicity of antibiotics was performed using bioluminescent bacterium Vibrio fischeri and EC₅₀ of CEF, TET and MNZ were found to be 18.25 mg L^-1, 173.8 mg L^-1, and 668.6 mg L^-1, respectively. However, the relative toxicity levels of PVA-CS-TiO₂ and treated effluent were well with the limits as inferred from the microtoxicity analysis. Thus, synthesized biocompatible composite exhibited structural stability, consistent performance for three photocatalytic cycles for all antibiotics at a minimal catalyst loading, easily retained using metallic tea strainer and does not exhibit microtoxicity has a scope for real-time applications.

Novel and effective hemostats based on graphene oxide-polymer aerogels: In vitro and in vivo evaluation

In this study, graphene oxide (GO)-based aerogels cross-linked with chitosan (CS), gelatin (GEL), and polyvinyl alcohol (PVA) were characterized and their hemostatic efficiencies both in vitro and in vivo were investigated and compared to commercial materials (ChitoGauze®XR and Spongostan™). All aerogels exhibited highly porous structures and a negative surface charge density favorable to their interaction with blood cells. The in vitro studies showed that all aerogels coagulated >60 % of the blood contained in their structures after 240 s of the whole-blood clotting assay, the GO-CS aerogel being the one with the highest blood clotting. All aerogels showed high hemocompatibility, with hemolytic rates <5 %, indicating their use as biomaterials. Among them, the GO-GEL aerogel exhibited the lowest hemolytic activity, due possibly to its high GEL content compared to the GO amount. According to their blood clotting activity, aerogels did not promote coagulation through extrinsic and intrinsic pathways. However, their surfaces are suitable for accelerating hemostasis by promoting alternative routes. All aerogels adhered platelets and gathered RBCs on their surfaces, and in addition the GO-CS aerogel surface also promoted the formation of filamentous fibrin networks adhered on its structure. Furthermore, in vivo evaluations revealed that all aerogels significantly shortened the hemostatic times and reduced the blood loss amounts compared both to the Spongostan™ and ChitoGauze®XR commercial materials and to the gauze sponge (control group). The hemostatic performance in vitro and in vivo of these aerogels suggests that they could be used as hemostats for controlling profuse bleedings.

Oxidized dextran crosslinked polysaccharide/protein/polydopamine composite cryogels with multiple hemostatic efficacies for noncompressible hemorrhage and wound healing

Noncompressible hemorrhage caused by gunshots and sharp objects leads to higher trauma mortality, and cryogels have great potential in controlling noncompressible hemorrhage applications owing to their shape-memory properties. However, the use of non-toxic crosslinkers to prepare cryogels for noncompressible hemorrhage remains a challenge. In this study, a series of cryogels were prepared using oxidized dextran (ODex) as a biocompatible crosslinker, combined with the good hemostatic properties of chitosan (CS) and human-like collagen (HLC), and polydopamine nanoparticles (PDA-NPs) were also introduced to strengthen the shape recovery speed of the cryogels and further enhance their hemostatic performance. The CS/HLC/ODex/PDA-NPs (CHOP) cryogels presented a highly interconnected macroporous structure, powerful water/blood absorption capacity, robust mechanical performance, and rapid water/blood-triggered shape recovery. In vitro coagulation and coagulation mechanism tests showed that CHOP exhibited strong procoagulant ability, high adhesion to blood cells and fibrinogen, and the capacity to activate platelets and intrinsic pathways. In vivo hemostatic tests indicated that CHOP could effectively shorten the bleeding time and reduce the bleeding volume of liver incision bleeding and liver noncompressible hemorrhage. Meanwhile, CHOP exhibited good biocompatibility and biodegradability, and could promote wound healing. These results suggest that CHOP cryogels will be a promising hemostatic dressing.

Dual-Driven Hemostats Featured with Puncturing Erythrocytes for Severe Bleeding in Complex Wounds

Achieving rapid hemostasis in complex and deep wounds with secluded hemorrhagic sites is still a challenge because of the difficulty in delivering hemostats to these sites. In this study, a Janus particle, SEC-Fe@CaT with dual-driven forces, bubble-driving, and magnetic field– (MF–) mediated driving, was prepared via in situ loading of Fe₃O₄ on a sunflower sporopollenin exine capsule (SEC), and followed by growth of flower-shaped CaCO₃ clusters. The bubble-driving forces enabled SEC-Fe@CaT to self-diffuse in the blood to eliminate agglomeration, and the MF-mediated driving force facilitated the SEC-Fe@CaT countercurrent against blood to access deep bleeding sites in the wounds. During the movement in blood flow, the meteor hammer-like SEC from SEC-Fe@CaT can puncture red blood cells (RBCs) to release procoagulants, thus promoting activation of platelet and rapid hemostasis. Animal tests suggested that SEC-Fe@CaT stopped bleeding in as short as 30 and 45 s in femoral artery and liver hemorrhage models, respectively. In contrast, the similar commercial product Celox™ required approximately 70 s to stop the bleeding in both bleeding modes. This study demonstrates a new hemostat platform for rapid hemostasis in deep and complex wounds. It was the first attempt integrating geometric structure of sunflower pollen with dual-driven movement in hemostasis.

Nanoporous and nano thickness film-forming bioactive composition for biomedical applications

Unmanageable bleeding is one of the significant causes of mortality. Attaining rapid hemostasis ensures subject survivability as a first aid during combats, road accidents, surgeries that reduce mortality. Nanoporous fibers reinforced composite scaffold (NFRCS) developed by a simple hemostatic film-forming composition (HFFC) (as a continuous phase) can trigger and intensify hemostasis. NFRCS developed was based on the dragonfly wing structure's structural design. Dragonfly wing structure consists of cross-veins and longitudinal wing veins inter-connected with wing membrane to maintain the microstructural integrity. The HFFC uniformly surface coats the fibers with nano thickness film and interconnects the randomly distributed cotton gauge (Ct) (dispersed phase), resulting in the formation of a nanoporous structure. Integrating continuous and dispersed phases reduce the product cost by ten times that of marketed products. The modified NFRCS (tampon or wrist band) can be used for various biomedical applications. The in vivo studies conclude that the developed Cp NFRCS triggers and intensifies the coagulation process at the application site. The NFRCS could regulate the microenvironment and act at the cellular level due to its nanoporous structure, which resulted in better wound healing in the excision wound model.

Expandable, biodegradable, bioactive quaternized gelatin sponges for rapidly controlling incompressible hemorrhage and promoting wound healing

Designing expandable sponges with biodegradability and effective antibacterial properties are the urgent challenge for incompressible hemorrhage and wound healing. In the present investigation, based on quaternized gelatin (QG) and oxidized dextran (OD), a series of expandable sponges (ODQG) with high-water absorption capacity and robust mechanical properties were prepared. ODQG had good biodegradability in vitro and in vivo, and had inherent antibacterial activity (90% for E. coli and 99.74% for S. aureus). Due to the synergy effect of electrostatic interaction and blood concentration, ODQG could effectively attract and activate red blood cells/platelets and accelerate the coagulation process. Therefore, ODQG showed better hemostatic performance than Kuaikang® gelatin sponges and gauzes in incompressible hemorrhage model. Furthermore, ODQG could regulate inflammatory factor (TNF-α) and cytokines (TGF-β, VEGF), and greatly promote wound healing process. The biodegradable sponges with excellent antibacterial properties might have potential application prospect for incompressible hemostasis and wound healing in the future.

Silk Fibroin-Based Biomaterials for Hemostatic Applications

Hemostasis plays an essential role in all surgical procedures. Uncontrolled hemorrhage is the primary cause of death during surgeries, and effective blood loss control can significantly reduce mortality. For modern surgeons to select the right agent at the right time, they must understand the mechanisms of action, the effectiveness, and the possible adverse effects of each agent. Over the past decade, various hemostatic agents have grown intensely. These agents vary from absorbable topical hemostats, including collagen, gelatins, microfibrillar, and regenerated oxidized cellulose, to biologically active topical hemostats such as thrombin, biological adhesives, and other combined agents. Commercially available products have since expanded to include topical hemostats, surgical sealants, and adhesives. Silk is a natural protein consisting of fibroin and sericin. Silk fibroin (SF), derived from silkworm Bombyx mori, is a fibrous protein that has been used mostly in fashion textiles and surgical sutures. Additionally, SF has been widely applied as a potential biomaterial in several biomedical and biotechnological fields. Furthermore, SF has been employed as a hemostatic agent in several studies. In this review, we summarize the several morphologic forms of SF and the latest technological advances on the use of SF-based hemostatic agents.

Direct Ink Writing of Biocompatible Nanocellulose and Chitosan Hydrogels for Implant Mesh Matrices

Direct ink writing via single or multihead extrusion is used to synthesize layer-by-layer (LbL) meshes comprising renewable polysaccharides. The best mechanical performance (683 ± 63 MPa modulus and 2.5 ± 0.4 MPa tensile strength) is observed for 3D printed structures with full infill density, given the role of electrostatic complexation between the oppositely charged components (chitosan and cellulose nanofibrils). The LbL structures develop an unexpectedly high wet stability that undergoes gradual weight loss at neutral and slightly acidic pH. The excellent biocompatibility and noncytotoxicity toward human monocyte/macrophages and controllable shrinkage upon solvent exchange make the cellular meshes appropriate for use as biomedical implants.

Is It an Outbreak of Health Care-Associated Infection? An Investigation of Binocular Conjunctival Congestion After Laparoscopic Cholecystectomy Was Traced to Chitosan Derivatives

Background

From May 6 to May 23, 2019, 24 (80.00%) patients who underwent laparoscopic cholecystectomy (LC) developed binocular conjunctival congestion within 4–8 h after their operation in the day ward of a teaching hospital.

Methods

Nosocomial infection prevention and control staff undertook procedural and environmental investigations, performed a case-control retrospective study (including 24 cases and 48 controls), and reviewed all lot numbers of biological material products to investigate the suspected outbreak of health care-associated infection.

Findings

Initially, an outbreak of health care-associated infection caused by bacteria was hypothesized. We first suspected the membranes that covered patients' eyes were cut using non-sterile scissors and thus contaminated, but they failed to yield bacteria. In addition, both corneal and conjunctival fluorescein staining results were negative in case-patients and isolated bacteria were ubiquitous in the environment or common skin commensals or normal flora of conjunctiva from 218 samples from day surgery and the day ward. Hence, we considered a non-infectious factor as the most likely cause of the binocular conjunctival congestion. Then, we found that case-patients were more likely than LC surgery patients without binocular conjunctival congestion to be exposed to biological materials in a retrospective case-control study. When we reviewed lot numbers, duration of use, and the number of patients who received four biological material products during LC in the day ward, we found that the BLK1821 lot of a modified chitosan medical membrance (the main ingredient is chitosan, a linear cationic polysaccharide) was used concurrently to when the case aggregation appeared. Finally, we surmised there was a correlation between this product and the outbreak of binocular conjunctival congestion. Relapse of the pseudo-outbreak has not been observed since stopping usage of the product for 6 months.

Conclusion

A cluster of binocular non-infectious conjunctival congestion diagnosed after LC proved to be a pseudo-outbreak. We should pay more attention to adverse events caused by biomaterials in hospitals.

A novel hydrogel based on Bletilla striata polysaccharide for rapid hemostasis: Synthesis, characterization and evaluation

The purpose of this study is to develop a new polysaccharide-based hydrogel. The Box-Behnken design was used to optimize the optimal synthesis conditions of the hydrogel, with the swelling parameters as indicators. The findings of rheologic tests confirm that free radical polymerization and the introduction of linear polymers improved the mechanical strength of the hydrogel. Combined with the characterization results, the gel mechanism of BSP-g-PAA/PVA DN hydrogel was proposed. The intermolecular association and entanglement increase, which effectively dissipates energy, thereby enhancing the mechanical properties of the hydrogel. In vitro blood compatibility experiments show that DN hydrogel has a low hemolysis rate and a good coagulation effect. The material is non-cytotoxic to L929 cells. The hepatic haemorrhage and mouse-tail amputation models of rats and mice were used to further evaluate the in vivo wound sealing and hemostatic properties of the hydrogel. The blood loss and hemostatic time were significantly lower than those of the control group, indicating that the hydrogel has excellent hemostatic effects. Therefore, the obtained BSP-g-PAA/PVA DN network hydrogel has good comprehensive properties and is expected to be used as a hemostatic material or a precursor of a drug carrier and a tissue engineering scaffold.

Nanocatalyst doped bacterial cellulose-based thermosensitive nanogel with biocatalytic function for antibacterial application

Reactive oxygen species (ROS) for treating bacterial infection is an alternative strategy to overcome the drawbacks such as bacterial resistance of commonly used antibiotics. Nanocatalysts have been proved highly effective in regulating intracellular ROS level due to their intrinsic enzymes-mimicking ability. Herein, we prepared a carbon-based nanozyme doped with copper atoms with peroxidase mimetic activity to catalyze the decomposition of bio-safety dosage of H₂O₂ to highly reactive OH radicals for antibacterial treatment. Furthermore, we designed the thermo-responsive nanogels consisting of bacterial cellulose nanowhiskers as the carrier of the nanozyme. The obtained nanogels displayed remarkable intelligent response to temperature change with sol-gel transition temperature of ~33 °C and in situ gel forming ability. Moreover, the nanogels exhibited excellent biocompatibility in vitro, along with remarkable antibacterial efficacy which could inactivate 6.36 log of S. aureus and 6.01 log of E. coli in 3 h, respectively. The findings provide a novel strategy for advancing the development of nanocatalysts-based responsive biomaterials for treating bacterial infections.

Engineering a naturally derived hemostatic sealant for sealing internal organs

Controlling bleeding from a raptured tissue, especially during the surgeries, is essentially important. Particularly for soft and dynamic internal organs where use of sutures, staples, or wires is limited, treatments with hemostatic adhesives have proven to be beneficial. However, major drawbacks with clinically used hemostats include lack of adhesion to wet tissue and poor mechanics. In view of these, herein, we engineered a double-crosslinked sealant which showed excellent hemostasis (comparable to existing commercial hemostat) without compromising its wet tissue adhesion. Mechanistically, the engineered hydrogel controlled the bleeding through its wound-sealing capability and inherent chemical activity. This mussel-inspired hemostatic adhesive hydrogel, named gelatin methacryloyl-catechol (GelMAC), contained covalently functionalized catechol and methacrylate moieties and showed excellent biocompatibility both in vitro and in vivo. Hemostatic property of GelMAC hydrogel was initially demonstrated with an in vitro blood clotting assay, which showed significantly reduced clotting time compared to the clinically used hemostat, Surgicel®. This was further assessed with an in vivo liver bleeding test in rats where GelMAC hydrogel closed the incision rapidly and initiated blood coagulation even faster than Surgicel®. The engineered GelMAC hydrogel-based seaalant with excellent hemostatic property and tissue adhesion can be utilized for controlling bleeding and sealing of soft internal organs.

Marine Polysaccharides for Wound Dressings Application: An Overview

Wound dressings have become a crucial treatment for wound healing due to their convenience, low cost, and prolonged wound management. As cutting-edge biomaterials, marine polysaccharides are divided from most marine organisms. It possesses various bioactivities, which allowing them to be processed into various forms of wound dressings. Therefore, a comprehensive understanding of the application of marine polysaccharides in wound dressings is particularly important for the studies of wound therapy. In this review, we first introduce the wound healing process and describe the characteristics of modern commonly used dressings. Then, the properties of various marine polysaccharides and their application in wound dressing development are outlined. Finally, strategies for developing and enhancing marine polysaccharide wound dressings are described, and an outlook of these dressings is given. The diverse bioactivities of marine polysaccharides including antibacterial, anti-inflammatory, haemostatic properties, etc., providing excellent wound management and accelerate wound healing. Meanwhile, these biomaterials have higher biocompatibility and biodegradability compared to synthetic ones. On the other hand, marine polysaccharides can be combined with copolymers and active substances to prepare various forms of dressings. Among them, emerging types of dressings such as nanofibers, smart hydrogels and injectable hydrogels are at the research frontier of their development. Therefore, marine polysaccharides are essential materials in wound dressings fabrication and have a promising future.

Haemostatic materials for wound healing applications

Wounds are one of the most common health issues, and the cost of wound care and healing has continued to increase over the past decade. The first step in wound healing is haemostasis, and the development of haemostatic materials that aid wound healing has accelerated in the past 5 years. Numerous haemostatic materials have been fabricated, composed of different active components (including natural polymers, synthetic polymers, silicon-based materials and metal-containing materials) and in various forms (including sponges, hydrogels, nanofibres and particles). In this Review, we provide an overview of haemostatic materials in wound healing, focusing on their chemical design and operation. We describe the physiological process of haemostasis to elucidate the principles that underpin the design of haemostatic wound dressings. We also highlight the advantages and limitations of the different active components and forms of haemostatic materials. The main challenges and future directions in the development of haemostatic materials for wound healing are proposed.

Microchannelled alkylated chitosan sponge to treat noncompressible hemorrhages and facilitate wound healing

Developing an anti-infective shape-memory hemostatic sponge able to guide in situ tissue regeneration for noncompressible hemorrhages in civilian and battlefield settings remains a challenge. Here we engineer hemostatic chitosan sponges with highly interconnective microchannels by combining 3D printed microfiber leaching, freeze-drying, and superficial active modification. We demonstrate that the microchannelled alkylated chitosan sponge (MACS) exhibits the capacity for water and blood absorption, as well as rapid shape recovery. We show that compared to clinically used gauze, gelatin sponge, CELOX™, and CELOX™-gauze, the MACS provides higher pro-coagulant and hemostatic capacities in lethally normal and heparinized rat and pig liver perforation wound models. We demonstrate its anti-infective activity against S. aureus and E. coli and its promotion of liver parenchymal cell infiltration, vascularization, and tissue integration in a rat liver defect model. Overall, the MACS demonstrates promising clinical translational potential in treating lethal noncompressible hemorrhage and facilitating wound healing.

An Injectable Hybrid Gelatin Methacryloyl (GelMA)/Phenyl Isothiocyanate-Modified Gelatin (Gel-Phe) Bioadhesive for Oral/Dental Hemostasis Applications

Biomaterials are widely used for effectively controlling bleeding in oral/dental surgical procedures. Here, gelatin methacryloyl (GelMA) was synthesized by grafting methacrylic anhydride on gelatin backbone, and phenyl isothiocyanate-modified gelatin (Gel-Phe) was synthesized by conjugating different gelatin/phenyl isothiocyanate molar ratios (G/P ratios) (i.e., 1:1, 1:5, 1:10, 1:15, 1:25, 1:50, 1:100, and 1:150) with gelatin polymer chains. Afterward, we combined GelMA and Gel-Phe as an injectable and photo-crosslinkable bioadhesive. This hybrid material system combines photo-crosslinking chemistry and supramolecular interactions for the design of bioadhesives exhibiting a highly porous structure, injectability, and regulable mechanical properties. By simply regulating the G/P ratio (1:1-1:15) and UV exposure times (15-60 s), it was possible to modulate the injectability and mechanical properties of the GelMA/Gel-Phe bioadhesive. Moreover, we demonstrated that the GelMA/Gel-Phe bioadhesive showed low cytotoxicity, a highly porous network, and the phenyl-isothiourea and amine residues on Gel-Phe and GelMA polymers with synergized hemostatic properties towards fast blood absorption and rapid clotting effect. An in vitro porcine skin bleeding and an in vitro dental bleeding model confirmed that the bioadhesive could be directly extruded into the bleeding site, rapidly photo-crosslinked, and reduced blood clotting time by 45%. Moreover, the in situ crosslinked bioadhesive could be easily removed from the bleeding site after clotting, avoiding secondary wound injury. Overall, this injectable GelMA/Gel-Phe bioadhesive stands as a promising hemostatic material in oral/dental surgical procedures.

Fabrication of multifunctional mucoadhesive buccal patch for drug delivery applications

Mucoadhesive buccal patch is a promising dosage form for a successful oral drug delivery, which provides unique advantages for various applications such as treatment of periodontal disease and postdental surgery disorders. The aim of this study is to synthesize a novel multifunctional mucoadhesive buccal patch in a multilayer reservoir design for therapeutic applications. The patches were fabricated through simultaneous electrospinning of chitosan/poly(vinylalcohol) (PVA)/ibuprofen and electrospraying of phenylalanine amino acid nanotubes (PhNTs) containing metronidazole into the electrospun mats through a layer-by-layer process. An electrospun poly(caprolactone) (PCL) was used as an impermeable backing layer to protect the mucoadhesive component from tongue movement and drug loss. Buccal patches were characterized using scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) and also evaluated in terms of physicomechanical parameters such as pH, weight, thickness, tensile strength, folding endurance, and mucoadhesive properties. The swelling index of the patches was examined with respect to the PVA/chitosan ratio. The effect of genipin addition to the electrospinning solution was also studied on mucoadhesive and swelling properties. The cell viability of buccal patches was assessed by methylthiazolydiphenyl-tetrazolium bromide test on L929 fibroblast cell line. The patch with an optimal amount of mucoadhesive polymers (PVA/chitosan 80:20) and crosslinking agent (0.05 g) indicated an ideal hemostatic activity along with antibacterial properties against Streptococcus mutans bacteria. The synthesized multifunctional mucoadhesive patch with a novel composition and design has a great potential for oral therapeutic applications.

Biocompatible and antibacterial soy protein isolate/quaternized chitosan composite sponges for acute upper gastrointestinal hemostasis

Innovative biomedical applications have high requirements for biomedical materials. Herein, a series of biocompatible, antibacterial and hemostatic sponges were successfully fabricated for the treatment of acute upper gastrointestinal bleeding (AUGB). Quaternized chitosan (QC) and soy protein isolate (SPI) were chemically cross-linked to obtain porous SPI/QC sponges (named SQS-n, with n = 30, 40, 50 or 60 corresponding to the weight percentage of the QC content). The chemical composition, physical properties and biological activity of SQS-n were investigated. SQS-n could support the adhesion and proliferation of L929 cells while triggering no obvious blood toxicity. Meanwhile, SQS-n exhibited good broad-spectrum antibacterial activity against both gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). The in vivo hemostatic effect of SQS-n was evaluated using three different bleeding models. The results revealed that SQS-50 performed best in reducing blood loss and hemostatic time. The overall hemostatic effect of SQS-50 was comparable to that of a commercial gelatin sponge. The enhanced antibacterial and hemostatic activities of SQS-n were mainly attributed to the QC component. In conclusion, this work developed a QC-functionalized hemostatic sponge that is highly desirable for innovative biomedical applications, such as AUGB.

An injectable, dual crosslinkable hybrid pectin methacrylate (PECMA)/gelatin methacryloyl (GelMA) hydrogel for skin hemostasis applications

Biomaterials for effective hemorrhage control are urgently needed in clinics as uncontrolled bleeding is associated with high mortality. Herein, we developed an injectable and in situ photo-crosslinkable hybrid hemostatic hydrogel by combining pectin methacrylate (PECMA) and gelatin methacryloyl (GelMA). This modular material system combines ionic- and photo-crosslinking chemistries to design interpenetrating networks (IPN) exhibiting tunable rheology, highly porous structure, and controllable swelling and mechanical properties. By simply changing the calcium (0-15 mM) and polymer (1.5-7%) content used for the sequential crosslinking of hydrogels via calcium gelation and UV-photopolymerization, it was possible to precisely modulate the injectability, degradation, and swelling ratio. Moreover, it is demonstrated that PECMA/GelMA hydrogels present good cytocompatibility and uniquely synergize the hemostatic properties of calcium ions on PECMA, the amine residues on GelMA, and the highly porous network toward rapid blood absorption and fast coagulation effect. An in vitro porcine skin bleeding model confirmed that the hydrogel could be directly injected into the wound and rapidly photo-crosslinked, circumventing the bleeding and decreasing the coagulation time by 39%. Importantly, the crosslinked hydrogel could be easily removed to prevent secondary wound injury. Overall, this injectable hybrid PECMA/GelMA hydrogel stands as a promising hemostatic material.

Bioscaffolds embedded with regulatory modules for cell growth and tissue formation: A review

The demand for artificial organs has greatly increased because of various aging-associated diseases and the wide need for organ transplants. A recent trend in tissue engineering is the precise reconstruction of tissues by the growth of cells adhering to bioscaffolds, which are three-dimensional (3D) structures that guide tissue and organ formation. Bioscaffolds used to fabricate bionic tissues should be able to not only guide cell growth but also regulate cell behaviors. Common regulation methods include biophysical and biochemical stimulations. Biophysical stimulation cues include matrix hardness, external stress and strain, surface topology, and electromagnetic field and concentration, whereas biochemical stimulation cues include growth factors, proteins, kinases, and magnetic nanoparticles. This review discusses bioink preparation, 3D bioprinting (including extrusion-based, inkjet, and ultraviolet-assisted 3D bioprinting), and regulation of cell behaviors. In particular, it provides an overview of state-of-the-art methods and devices for regulating cell growth and tissue formation and the effects of biophysical and biochemical stimulations on cell behaviors. In addition, the fabrication of bioscaffolds embedded with regulatory modules for biomimetic tissue preparation is explained. Finally, challenges in cell growth regulation and future research directions are presented.

A physicochemical double cross-linked multifunctional hydrogel for dynamic burn wound healing: shape adaptability, injectable self-healing property and enhanced adhesion

Burn wounds are one of the most destructive skin traumas that cause more than 180000 deaths each year. Patients with large, irregular burn wounds suffer from slow healing. Dynamic burn wounds have special requirements for hydrogel dressing due to their high frequency movement. To focus on dynamic burn wounds, we designed a novel double cross-linked hydrogel prepared by Schiff base and catechol-Fe³⁺ chelation bond. The unique double cross-linked structure of the hydrogel resulted in better physicochemical properties and enhanced efficacy. The enhanced physicochemical properties, such as faster gelation time (52 ± 2 s), stronger mechanical property (535 kPa of G'), enhanced adhesive strength (19.3 kPa) and better self-healing property, made the hydrogel suitable for dynamic wounds. The excellent shape adaptability (97.1 ± 1.3% of recovery) made the hydrogel suitable for wounds with irregular shapes. The hydrogel exhibited not only biodegradability during the wound healing process but also superior inherent antibacterial activity (100% killing ratio) and hemostatic property. The results showed that the hydrogel shortened the healing time of burn wounds to 13 days, and accelerated the reconstruction of skin structure and function. This double cross-linked multifunctional hydrogel is a promising candidate as a dynamic burn wound dressing.

Polysaccharides-modified chitosan as improved and rapid hemostasis foam sponges

Serial hemostatic sponges consisting of polysaccharides-modified chitosan foam sponges were prepared by Schiff base crosslinking reaction between the deacetylated chitosan and oxidized dialdehyde cellulose. Such composite foam sponges were characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy to confirm their morphology and compositions. Then the coagulation process was evaluated in vitro by thrombus elasticity meters. Furthermore, the hemostasis experiments on mouse tail vein and rabbit femoral artery were also performed in vivo. The results strongly indicated that such synergistic cellulose-modified chitosan foam sponges showed comprehensively excellent water-absorbing quality, improved mechanical performance, low hemolysis rates, benign cytotoxicity, good resilience ability after repeated compression, and superior hemostasis capability both in vitro and in vivo. Furthermore, the hemostatic mechanism is via adhering/activating the red blood cell/platelet to form robust blood clots through the endogenous coagulation pathway, which serves as a good candidate for emergency trauma treatment in daily civilian and military hemostasis.

By Endowing Polyglutamic Acid/Polylysine Composite Hydrogel with Super Intrinsic Characteristics to Enhance its Wound Repair Potential

In this study, multifunctional porous composite hydrogels are prepared via composite technology and using poly(glutamic acid) and (polylysine) as precursors, casein as foaming agent, and calcium ions as coagulant. The results show that the as-prepared hydrogels have high porosity and water absorbency, and good mechanical, inherent antibacterial, and bioadhesive properties. The results show such high water absorption, bioadhesion, and porosity of the as-prepared hydrogel can effectively concentrate blood components and seal wounds better. The release of calcium ions in the as-prepared hydrogels can activate coagulation factors. Both factors can play an important role in hemostasis. The excellent hydroscopicity, moisture retention, adhesion, and inherent antibacterial properties of the as-prepared hydrogel can create a moist, sterile, and closed microenvironment for the wound healing. The experimental results of a deep skin defect model have verified its good effect of promoting wound repair. These inherent excellent properties can endow the as-prepared hydrogel with a wide range of application values.

Fabricating poly(vinyl alcohol)/gelatin composite sponges with high absorbency and water-triggered expansion for noncompressible hemorrhage and wound healing

Composite sponges obtained from PVA and gelatin were synthesized by thiol–ene chemistry and used for controlling noncompressible hemorrhage.