Tannic acid/CaII anchored on the surface of chitin nanofiber sponge by layer-by-layer deposition: Integrating effective antibacterial and hemostatic performance

Smart design in biopolymer-based hemostatic sponges: From hemostasis to multiple functions

Uncontrolled hemorrhage remains the leading cause of death in clinical and emergency care, posing a major threat to human life. To achieve effective bleeding control, many hemostatic materials have emerged. Among them, nature-derived biopolymers occupy an important position due to the excellent inherent biocompatibility, biodegradability and bioactivity. Additionally, sponges have been widely used in clinical and daily life because of their rapid blood absorption. Therefore, we provide the overview focusing on the latest advances and smart designs of biopolymer-based hemostatic sponge. Starting from the component, the applications of polysaccharide and polypeptide in hemostasis are systematically introduced, and the unique bioactivities such as antibacterial, antioxidant and immunomodulation are also concerned. From the perspective of sponge structure, different preparation processes can obtain unique physical properties and structures, which will affect the material properties such as hemostasis, antibacterial and tissue repair. Notably, as development frontier, the multi-functions of hemostatic materials is summarized, mainly including enhanced coagulation, antibacterial, avoiding tumor recurrence, promoting tissue repair, and hemorrhage monitoring. Finally, the challenges facing the development of biopolymer-based hemostatic sponges are emphasized, and future directions for in vivo biosafety, emerging materials, multiple application scenarios and translational research are proposed.

Chitin/Chitosan Nanofibers Toward a Sustainable Future: From Hierarchical Structural Regulation to Functionalization Applications

Owing to its multiple fascinating properties of renewability, biodegradability, biocompatibility, and antibacterial activity, chitin is expected to become a green cornerstone of next-generation functional materials. Chitin nanofibers, as building blocks, form multiscale hierarchical structures spanning nano- and macrolevels in living organisms, which pave the way for sophisticated functions. Therefore, from a biomimetic perspective, exploiting chitin nanofibers for use in multifunctional, high-performance materials is a promising approach. Here, we first summarize the latest advances in the multiscale hierarchical structure assembly mode of chitin and its derivative nanofibers, including top-down exfoliation and bottom-up synthesis. Subsequently, we emphasize the environmental impacts of these methods, which are crucial for whether chitin nanofibers can truly contribute to a more eco-friendly era. Furthermore, the latest progress of chitin nanofibers in environmental and medical applications is also discussed. Finally, the potential challenges and tailored solutions of chitin nanofibers are further proposed, covering raw material, structure, function, manufacturing, policies, etc.

Chitosan/starch based unoxidized tannic acid modified microparticles for rapid hemostasis with broad spectrum antibacterial activity

The development of a rapid hemostat through a facile method with co-existing antibacterial activity and minimum erythrocyte lysis property stands as a major requirement in the field of hemostasis. Herein, a series of novel microparticle hemostats were synthesized using chitosan, different hydrothermally-treated starches, and cross-linked with tannic acid (TA) simultaneously in an unoxidized environment via ionotropic gelation method. Hemostats' comparative functional properties, such as adjustable antibacterial and erythrocyte compatibility upon various starch additions were evaluated. The in vivo hemostatic study revealed that the developed hemostats for mouse liver laceration and rat tail amputation had clotting times (13 s and 38 s, respectively) and blood loss (51 mg and 62 mg, respectively) similar to those of Celox™. The erythrocyte adhesion test suggested that erythrocyte distortion can be lowered by modifying the antibacterial hemostats with different starches. The broad-spectrum antibacterial efficacy of the hemostats remained intact against S. aureus (>90 %), E. coli (>80 %), and P. mirabilis bacteria upon starch modification. They also demonstrated high hemocompatibility (<3 % hemolysis ratio), moderate cell viability (>81 %), in vivo biodegradation, and angiogenesis indicating adequate biocompatibility and wound healing. The developed hemostats hold significant promise to be employed as rapid hemostatic agents for preventing major bleeding and bacterial infection in emergencies.

Biodegradable chitin nanofiber-alginate dialdehyde hydrogel: An injectable, self-healing scaffold for anti-tumor drug delivery

Injectable hydrogels fabricated from natural polymers have attracted increasing attentions for their potential in biomedical application owing to the biocompatibility and biodegradability. A new class of natural polymer based self-healing hydrogel is constructed through dynamic covalent bonds. The injectable self-healing hydrogels are fabricated by introducing alginate aldehyde to form Schiff base bonds with the chitin nanofibers. These hydrogels demonstrate excellent self-healing properties, injectability, and pH-responsive sol-gel transition behaviors. As a result, they can serve as carriers to allow an effective encapsulation of doxorubicin (DOX) for drug delivery. Furthermore, these hydrogels exhibit excellent biocompatibility and degradability in vitro and in vivo. The sustained release of DOX from the hydrogels effectively suppresses tumor growth in animal models without causing significant systemic toxicity, suggesting their potential application in anti-tumor therapies.

Recent research advances in polysaccharide-based hemostatic materials: A review

Massive bleeding resulting from civil and martial accidents can often lead to shock or even death, highlighting the critical need for the development of rapid and efficient hemostatic materials. While various types of hemostatic materials are currently utilized in clinical practice, they often come with limitations such as poor biocompatibility, toxicity, and biodegradability. Polysaccharides, such as alginate (AG), chitosan (CS), cellulose, starch, hyaluronic acid (HA), and dextran, have exhibit excellent biocompatibility and in vivo biodegradability. Their degradation products are non-toxic to surrounding tissues and can be absorbed by the body. As a result, polysaccharides have been extensively utilized in the development of hemostatic materials and have gained significant attention in the field of in vivo hemostasis. This review offers an overview of the different forms, hemostatic mechanisms, and specific applications of polysaccharides. Additionally, it discusses the future opportunities and challenges associated with polysaccharide-based hemostats.

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.

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 Biodegradable, Adhesive, and Stretchable Hydrogel and Potential Applications for Allergic Rhinitis and Epistaxis

Bioadhesive hydrogels have attracted considerable attention as innovative materials in medical interventions and human-machine interface engineering. Despite significant advances in their application, it remains critical to develop adhesive hydrogels that meet the requirements for biocompatibility, biodegradability, long-term strong adhesion, and efficient drug delivery vehicles in moist conditions. A biocompatible, biodegradable, soft, and stretchable hydrogel made from a combination of a biopolymer (unmodified natural gelatin) and stretchable biodegradable poly(ethylene glycol) diacrylate is proposed to achieve durable and tough adhesion and explore its use for convenient and effective intranasal hemostasis and drug administration. Desirable hemostasis efficacy and enhanced therapeutic outcomes for allergic rhinitis are accomplished. Biodegradation enables the spontaneous removal of materials without causing secondary damage and minimizes medical waste. Preliminary trials on human subjects provide an essential foundation for practical applications. This work elucidates material strategies for biodegradable adhesive hydrogels, which are critical to achieving robust material interfaces and advanced drug delivery platforms for novel clinical treatments.

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.

Abundant tannic acid modified gelatin/sodium alginate biocomposite hydrogels with high toughness, antifreezing, antioxidant and antibacterial properties

The acidity of high tannic acid (TA) content solution can destroy the structure of protein, such as gelatin (G). This causes a big challenge to introduce abundant TA into the G-based hydrogels. Here, the G-based hydrogel system with abundant TA as hydrogen bonds provider was constructed by a "protective film" strategy. The protective film around the composite hydrogel was first formed by the chelation of sodium alginate (SA) and Ca2+. Subsequently, abundant TA and Ca2+ were successively introduced into the hydrogel system by immersing method. This strategy effectively protected the structure of the designed hydrogel. After treatment with 0.3 w/v TA and 0.06 w/v Ca2+ solutions, the tensile modulus, elongation at break and toughness of G/SA hydrogel increased about 4-, 2-, and 6-fold, respectively. Besides, G/SA-TA/Ca2+ hydrogels exhibited good water retention, anti-freezing, antioxidant, antibacterial properties and low hemolysis ratio. Cell experiments showed that G/SA-TA/Ca2+ hydrogels possessed good biocompatibility and could promote cell migration. Therefore, G/SA-TA/Ca2+ hydrogels are expected to be used in the field of biomedical engineering. The strategy proposed in this work also provides a new idea for improving the properties of other protein-based hydrogels.

A kaolin/calcium incorporated shape memory and antimicrobial chitosan-dextran based cryogel as an efficient haemostatic dressing for uncontrolled hemorrhagic wounds

Increased mortalities associated with uncontrolled and excessive bleeding is still of paramount concern in the clinics, caregivers and military medics. Herein, we designed a shape memory cryogel based on chitosan (C) and functionalized-dextran (D), incorporated with Kaolin (K) and calcium (Ca²⁺) as haemostatic agents. The developed cryogel (CDKCa) exhibits a uniform interconnected porous architecture with profound fluid absorption ability, rapid blood clotting, stable clot formation and good antibacterial activity. The CDKCa elucidates significantly less clotting time (~30 s; in-vitro) and increased aggregation and activation of platelets/red blood cells in comparison to the control groups and commercial dressings (Axiostat and QuikClot). The developed CDKCa also significantly reduced the aPTT and PT values by ~58 % and 31 % respectively, leading to the activation of intrinsic and extrinsic coagulation cascades. The CDKCa cryogel displays enhanced mechanical stability, flexibility and a good shape memory, a property quintessential to cease uncontrolled bleeding in irregular and non-compressible wounds. Further, the Kaolin and Ca²⁺ incorporated shape memory CDKCa cryogel demonstrates a rapid blood coagulation and stable clot formation in different compressible and non-compressible rat liver and femur hemorrhagic models. In summary, the endorsed results of CDKCa suggest that the design, fabrication and excellent clotting ability may attribute to high haemostatic efficiency of CDKCa dressing and have a great potential to prevent uncontrollable hemorrhages.

Euryale ferox stem-inspired anisotropic quaternized cellulose/xanthan-based antibacterial sponge with high absorbency and compressibility for noncompressible hemorrhage

Uncontrollable hemorrhage from deep noncompressible wounds remains an intractable challenge. Herein, inspired by the euryale ferox stem which is capable of transporting water and nutrient substances efficiently along longitudinally aligned channels, an anisotropic sponge with rapidly liquid absorption capacity, excellent mechanical compressibility and antibacterial property based on quaternized cellulose (QC), xanthan gum (XG) and reduced graphene oxide (rGO), was constructed. The euryale ferox stem-like structure and multiple interactions, involving hydrogen bonding, electrostatic interaction and chemical crosslinking, endowed the sponge with excellent fatigue resistance, elasticity and efficient liquid absorption capacity. In vivo rat liver injury, tail amputation and liver noncompressible hemorrhage model experiments confirmed that the sponge exhibited superior hemostatic performance than commercial gelatin sponge, attributing to the positive charge, efficient absorption capacity and rough surface of the sponge, which synergistically promoting the aggregation and activation of red blood cells and platelets as well as formation of fibrin network, leading to accelerated blood coagulation process. Besides, the sponge showed favorable cytocompatibility, hemocompatibility and antibacterial property. Overall, the bioinspired sponge had fantastic potential for controlling deep noncompressible hemorrhage and providing a new idea for designing hemostatic materials.

On the development of modular polyurethane-based bioelastomers for rapid hemostasis and wound healing

Massive hemorrhage may be detrimental to the patients, which necessitates the advent of new materials with high hemostatic efficiency and good biocompatibility. The objective of this research was to screen for the effect of the different types of bio-elastomers as hemostatic dressings. 3D loose nanofiber sponges were prepared; PU-TA/Gel showed promising potential. Polyurethane (PU) was synthesized and electrospun to afford porous sponges, which were crosslinked with glutaraldehyde (GA). FTIR and 1H-NMR evidenced the successful synthesis of PU. The prepared PU-TA/Gel sponge had the highest porosity and water absorption ratio. Besides, PU-TA/Gel sponges exhibited cytocompatibility, negligible hemolysis and the shortest clotting time. PU-TA/Gel sponge rapidly induced stable blood clots with shorter hemostasis time and less bleeding volume in a liver injury model in rats. Intriguingly, PU-TA/Gel sponges also induced good skin regeneration in a full-thickness excisional defect model as revealed by the histological analysis. These results showed that the PU-TA/Gel-based sponges may offer an alternative platform for hemostasis and wound healing.

A natural polyphenol-functionalized chitosan/gelatin sponge for accelerating hemostasis and infected wound healing

Natural polymers have been particularly appealing for constructing hemostatic materials/devices, but it is still desirable to develop new natural polymer-based biomaterials with balanced hemostatic and wound-healing performance. In this work, a natural polyphenol-functionalized chitosan/gelatin sponge (PCGS) was prepared by the lyophilization of a chitosan/gelatin mixture solution (under a self-foaming condition to prepare the CGS) and subsequent chemical cross-linking with procyanidin (PC). Compared with the original CGS, PCGS exhibited an enhanced liquid-absorption ability, reduced surface charges, and similar/low hemolysis rate. Benefiting from such a liquid-absorption ability (∼4000% for whole blood and normal saline) and moderate surface charges, PCGS exhibited high in vitro hemostatic property and promising hemostatic performance in an in vivo femoral-artery-injury model. In addition, PCGS possessed higher antioxidant property and slightly decreased antibacterial ability than CGS, owing to the incorporation of PC. The feasibility of PCGS for treating infected wounds was further confirmed in an in vivo infected-tooth-extraction model, as the typical complication of intractable tooth-extraction bleeding. The present work demonstrated a facile approach for developing multifunctional hemostatic materials through the flexible management of natural polymers and polyphenols.

Fabrication and Characterization of Electrospun Poly(Caprolactone)/Tannic Acid Scaffold as an Antibacterial Wound Dressing

Antibacterial wound dressings are promising materials to treat infected skin wounds, which greatly affect the wound-healing process. In this study, tannic acid (TA), a natural antibacterial agent, was successfully loaded by electrospinning into poly(caprolactone) (PCL) fibers in a high concentration. It is suggested that the addition of TA was beneficial for producing uniform and continuous PCL nanofibers. Hydrogen bonds existed between the PCL and TA molecules based on the analysis of FTIR spectra and DSC results. The interactions and continuous network improved the mechanical properties of the scaffolds. Meanwhile, increasing the amount of TA also enhanced the hydrophilicity and water absorption capacity of the scaffold, both of which are beneficial for accelerating wound healing. Moreover, a burst release of the TA in the initial stage and a controlled, steady release behavior over time contributed to the highly antibacterial properties of the PCL/TA scaffolds. The fabrication of the composite scaffold supplies a facile, efficient, and controllable approach to address the issue of antibacterial treatment in wound dressing.

Efficient oil-water emulsion treatment via novel composite membranes fabricated by CaCO3-based biomineralization and TA-Ti(IV) coating strategy

Continuous increasing discharge of industrial oily wastewater and frequent occurrence of oil spill accidents have taken heavy tolls on global environment and human health. Organic-inorganic modifications can fabricate superhydrophilic/submerged superoleophobic membranes for efficient oil-water separation/treatment though they still suffer from complex operation, non-environmental friendliness, expensive cost or uneven distribution. Herein, a new strategy regarding tannic acid (TA)-Ti(IV) coating and CaCO₃-based biomineralization through simple inkjet printing processes was proposed to modify polyvinylidene fluoride (PVDF) membrane, endowing the membrane with high hydrophilicity (water contact angle (WCA) decreased from 86.01° to 14.94°) and underwater superoleophobicity (underwater contact angle (UOCA) > 155°). The optimized TA-Ti(IV)-CaCO₃ modified membrane possessed perfect water permeation to various oil/water emulsions (e.g., 355.7 L·m^-2·h^-1 for gasoline emulsion) under gravity with superior separation efficiency (>98.8 %), leading the way in oil/water emulsion separation performance of PVDF membranes modified with polyphenolic surfaces to our knowledge. Moreover, the modified membrane displayed rather high flux recovery after eight cycles of filtration while maintaining the original excellent separation efficiency. The modification process proposed in this study is almost independent of the nature of the substrate, and meets the demand for simple, inexpensive, rapid preparation of highly hydrophilic antifouling membranes, showing abroad application prospect for oil-water emulsion separation/treatment.

Nanofibrous hemostatic materials: Structural design, fabrication methods, and hemostatic mechanisms

Development of rapid and effective hemostatic materials has always been the focus of research in the healthcare field. Nanofibrous materials which recapitulate the delicate nano-topography feature of fibrin fibers produced during natural hemostatic process, offer large length-to-diameter ratio and surface area, tunable porous structure, and precise control in architecture, showing great potential for staunching bleeding. Here we present a comprehensive review of advances in nanofibrous hemostatic materials, focusing on the following three important parts: structural design, fabrication methods, and hemostatic mechanisms. This review begins with an introduction to the physiological hemostatic mechanism and current commercial hemostatic agents. Then, it focuses on recent progress in electrospun nanofibrous hemostatic materials in terms of composition and structure control, surface modification, and in-situ deposition. The article emphasizes the development of three-dimensional (3D) electrospun nanofibrous materials and their emerging evolution for improving hemostatic function. Next, it discusses the fabrication of self-assembling peptide or protein-mimetic peptide nanofibers, co-assembling supramolecular nanofibers, as well as other nanofibrous hemostatic agents. Further, the article highlights the external and intracavitary hemostatic management based on various nanofiber aggregates. In the end, this review concludes with the current challenges and future perspectives of nanofibrous hemostatic materials. STATEMENT OF SIGNIFICANCE: This article reviews recent advances in nanofibrous hemostatic materials including fabrication methods, composition and structural control, performance improvement, and hemostatic mechanisms. A variety of methods including electrospinning, self-assembly, grinding and refining, template synthesis, and chemical vapor deposition, have been developed to prepare nanofibrous materials. These methods provide robustness in control of the nanofiber architecture in the forms of hydrogels, two-dimensional (2D) membranes, 3D sponges, or composites, showing promising potential in the external and intracavitary hemostasis and wound healing applications. This review will be of great interest to the broad readers in the field of hemostatic materials and multifunctional biomaterials.

Silk Fibroin/Tannin/ZnO Nanocomposite Hydrogel with Hemostatic Activities

The inevitable bleeding and infections caused by disasters and accidents are the main causes of death owing to extrinsic trauma. Hemostatic agents are often used to quickly suppress bleeding and infection, and they can solve this problem in a short time. Silk fibroin (SF) has poor processibility in water, owing to incomplete solubility therein. In this study, aiming to overcome this disadvantage, a modified silk fibroin (SF-BGE), easily soluble in water, was prepared by introducing butyl glycidyl ether (BGE) into its side chain. Subsequently, a small amount of tannic acid (TA) was introduced to prepare an SF-BGE /TA solution, and ZnO nanoparticles (NPs) were added to the solution to form the coordination bonds between the ZnO and TA, leading to an SF-based nanocomposite hydrogel. A structural characterization of the SF-BGE, SF-BGE/TA, SF-BGE/TA/ZnO, and the coordination bonds between ZnO/TA was observed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and the phase change was observed by rheological measurements. The pore formation of the SF-BGE/TA/ZnO hydrogel and dispersibility of ZnO were verified through energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The cytocompatible and hemostatic performances of the SF-BGE/TA/ZnO NPs composite hydrogels were evaluated, and the hydrogels showed superior hemostatic and cytocompatible activities. Therefore, the SF-based nanocomposite hydrogel is considered as a promising material for hemostasis.

Microcluster colloidosomes for hemostat delivery into complex wounds: A platform inspired by the attack action of torpedoes

Complex yet lethal wounds with uncontrollable bleeding hinder conventional hemostats from clotting blood at the source or deep sites of injury vasculature, thereby causing massive blood loss and significantly increased mortality. Inspired by the attack action of torpedoes, we synthesized microcluster (MC) colloidosomes equipped with magnetic-mediated navigation and "blast" systems to deliver hemostats into the cavity of vase-type wounds. CaCO₃/Fe₂O₃ (CF) microparticles functionalized with Arg-Gly-Asp (RGD) modified polyelectrolyte multilayers were co-assembled with oppositely charged zwitterionic carbon dots (CDs) to form MC colloidosomes, which were loaded with thrombin and protonated tranexamic acid (TXA-NH₃ ⁺). The composite microparticles moved against blood flow under magnetic mediation and simultaneously disassembled for the burst release of thrombin stimulated by TXA-NH₃ ⁺. The CO₂ bubbles generated during disassembly produced a "blast" that propelled thrombin into the wound cavity. Severe bleeding in a vase-type hemorrhage model in the rabbit liver was rapidly controlled within ∼60 s. Furthermore, in vivo subcutaneous muscle and liver implantation models demonstrated excellent biodegradability of MC colloidosomes. This study is the first to propose a novel strategy based on the principle of torpedoes for transporting hemostats into vase-type wounds to achieve rapid hemostasis, creating a new paradigm for combating trauma treatment.

Design of nanoconstructs that exhibit enhanced hemostatic efficiency and bioabsorbability

Hemorrhage is a prime cause of death in civilian and military traumatic injuries, whereby a significant proportion of death and complications occur prior to paramedic arrival and hospital resuscitation. Hence, it is crucial to develop hemostatic materials that are able to be applied by simple processes and allow control over bleeding by inducing rapid hemostasis, non-invasively, until subjects receive necessary medical care. This tutorial review discusses recent advances in synthesis and fabrication of degradable hemostatic nanomaterials and nanocomposites. Control of assembly and fine-tuning of composition of absorbable (i.e., degradable) hemostatic supramolecular structures and nanoconstructs have afforded the development of smart devices and scaffolds capable of efficiently controlling bleeding while degrading over time, thereby reducing surgical operation times and hospitalization duration. The nanoconstructs that are highlighted have demonstrated hemostatic efficiency pre-clinically in animal models, while also sharing characteristics of degradability, bioabsorbability and presence of nano-assemblies within their compositions.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Optimization of Chitin Nanofiber Preparation by Ball Milling as Filler for Composite Resin

Chitin nanofiber is a nanomaterial produced by pulverizing chitin, the main component of crab shells. Since it has excellent mechanical properties, it is expected to be used as a reinforcing material to strengthen materials. Chitin was mechanically ground in water using a ball mill to prepare nanofibers. The ball size, total ball weight, and milling time were varied, and the resulting water dispersion and the cast film were analyzed to optimize the conditions for efficient preparation. The length and width of the nanofibers were also measured by SEM and AFM observations. The size of the balls affected the level of grinding and the intensity of impact energy on the chitin. The most efficient crushing was achieved when the diameter was 1 mm. The total ball weight directly affects the milling frequency, and milling proceeds as the total weight increases. However, if too many balls occupy the container, the grinding efficiency decreases. Therefore, a total ball weight of 300 g was optimal. Regarding the milling time, the chitin becomes finer depending on the increase of that time. However, after a specific time, the shape did not change much. Therefore, a milling time of approximately 150 min was appropriate.

Hemostatic Performance of ɑ-Chitin/gelatin Composite Sponges with Directional Pore Structure

Biomedical materials with effective hemostatic properties are in great demand in clinical and battlefield application for severe hemorrhage control. In this study, nearly amorphous chitin is obtained by treating α-chitin with superfine grinding, and the solubility of chitin in hexafluoro-2-propanol (HFIP) is significantly increased. Chitin and gelatin mixtures are prepared by adding different amount of gelatin to the 8mg ml^-1 chitin solution. In the presence water (non-solvent), the mixtures are gelled as HFIP is replaced by water, and chitin/gelatin composite sponges with directional pore structure are prepared by directional freeze drying of the hydrogel. The structure, porosity, liquid absorbing capacity, biodegradability, and hemostatic properties of the sponges with different ratios of gelatin are investigated. The results show that the sponge with the mass ratio of chitin/gelatin of 1:1 is potential hemostatic material with high absorbing capacity, hemocompatibility, and the best hemostatic performance. The in vivo study demonstrates that hemostatic time of the composite sponge (73 s) is much shorter than of that of gauze (193 s), chitin sponge (132s) as well as gelatin sponge (116 s) in rat femoral artery injury model. This article is protected by copyright. All rights reserved.

Physiologically Inspired Mucin Coated Escherichia coli Nissle 1917 Enhances Biotherapy by Regulating the Pathological Microenvironment to Improve Intestinal Colonization

The delivery of probiotics to the microbiota is a promising method to prevent and treat diseases. However, oral probiotics will suffer from gastrointestinal insults, especially the pathological microenvironment of inflammatory diseases such as reactive oxygen species (ROS) and the exhausted mucus layer, which can limit their survival and colonization in the intestinal tract. Inspired by the fact that probiotics colonized and grew in the mucus layer under physiological conditions, we developed a strategy for a super probiotic (EcN@TA-Ca²⁺@Mucin) coated with tannic acid and mucin via layer-by-layer technology. We demonstrated that mucin endows probiotics with superior resistance to the harsh environment of the gastrointestinal tract and with strong adhesiveness to the intestine through its interaction with mucus, which enhanced colonization and growth of probiotics in the mucus layer without removing the coating. Moreover, EcN@TA-Ca²⁺@Mucin can distinctly down-regulate inflammation with ROS scavenging and reduce the side effects of bacterial translocation in inflammatory bowel diseases, increasing the abundance and diversity of the gut microflora. We envision that it is a powerful platform to improve the colonization of probiotics by regulating the pathological microenvironment, which is expected to provide an important perspective for applying the intestinal colonization of probiotics to treat a variety of diseases.

Biomaterials for Hemostasis

Uncontrolled bleeding is a major problem in trauma and emergency medicine. While materials for trauma applications would certainly find utility in traditional surgical settings, the unique environment of emergency medicine introduces additional design considerations, including the need for materials that are easily deployed in austere environments. Ideally, these materials would be available off the shelf, could be easily transported, and would be able to be stored at room temperature for some amount of time. Both natural and synthetic materials have been explored for the development of hemostatic materials. This review article provides an overview of classes of materials used for topical hemostats and newer developments in the area of injectable hemostats for use in emergency medicine. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A New Calcium(II)-Based Substitute for Enrofloxacin with Improved Medicinal Potential

Enrofloxacin (EFX) reacting with Ca(II) afforded a new complex, [Ca(EFX)₂(H₂O)₄] (EFX-Ca), which was structurally characterized both in solid and solution chemistry. E. coli and S. typhi were tested to be the most sensitive strains for EFX-Ca. The LD₅₀ value of EFX-Ca in mice was 7736 mg/kg, implying the coordination of EFX to Ca(II) effectively reduced its acute toxicity. EFX-Ca also decreased the plasma-binding rate and enhanced the drug distribution in rats along with longer elimination half-life. EFX-Ca also showed similar low in vivo acute toxicity and higher anti-inflammation induced by H₂O₂ or CuSO₄ in zebrafish, with reactive oxygen species (ROS)-related elimination. The therapeutic effects of EFX-Ca on two types (AA and 817) of E. coli-infected broilers were also better than those of EFX, with cure rates of 78% and 88%, respectively. EFX-Ca showed promise as a bio-safe metal-based veterinary drug with good efficacy and lower toxicity.

Blood compatibility evaluations of two-dimensional Ti3C2Txnanosheets

Two-dimensional (2D) nanomaterial Ti3C2Tx is a novel biomaterial used for medical apparatus. For its application, biosafety serves as a prerequisite for their use in vivo. So far, no research has systematically reported how Ti3C2Tx interacts with various components in the blood. In this work, we evaluated the hemocompatibility of Ti3C2Tx nanosheets which we prepared by HF etching. Effects of the concentration and size of Ti3C2Tx on the morphology and hemolysis rate of human red blood cells (RBCs), the structure and conformation of plasma proteins, the complement activation, as well as in vitro blood coagulation were studied. In general, Ti3C2Tx takes on good blood compatibility, but in the case of high concentration (>30 μg/mL) and "Small size" (about 100 nm), it led to the rupture of RBCs membrane and a higher rate of hemolysis. Meanwhile, platelets and complement were inclined to be activated with the increased concentration, accompanying the changed configuration of plasma proteins dependent on concentration. Surprisingly, the presence of Ti3C2Tx did not significantly disrupt the coagulation. In vitro cell culture, the results prove that when the Ti3C2Tx concentration is as high as 60μg/mL and still has good biological safety. By establishing a fuzzy mathematical model, it was proved that the hemocompatibility of Ti3C2Tx is more concentration-dependent than size-dependent, and the hemolysis rate is the most sensitive to the size and concentration of the Ti3C2Tx. These findings provide insight into the potential use of Ti3C2Tx as biofriendly nanocontainers for biomaterials in vivo.

Facile Polyphenol-Europium Assembly Enabled Functional Poly(l-Lactic Acid) Nanofiber Mats with Enhanced Antioxidation and Angiogenesis for Accelerated Wound Healing

Burns, trauma, surgery and chronic diabetic ulcers are the most common reasons causing skin wounds in clinic. Thus, developing a functional wound dressing has been an imperative issue. Herein, functional wound dressing (poly(l-lactic acid) PLLA-((tanic acid (TA)/europium (Eu))_n ) is fabricated through a facile polyphenol-europium ion assembly to ameliorate wound microenvironment via scavenging excessive reactive oxygen species (ROS) and promoting angiogenesis. The physicochemical characterization indicates that the multicycle assembled TA/Eu is uniformly deposited on PLLA-(TA/Eu)_n nanofiber mats surface. In vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant tests display good antioxidant ability by scavenging more than 75% ROS, and significantly increasing the antioxidant enzyme levels in vivo. Cytocompatibility experiments illustrate that PLLA-(TA/Eu)_n nanofiber mats can promote the adhesion and proliferation of human umbilical vein endothelial cells (HUVECs) and L929 cells. Meanwhile, real-time quantitative polymerase chain reaction (PCR) (RT-qPCR) and western blot assays illustrate that it can stimulate proangiogenesis by elevating the expression of angiogenesis-related genes and proteins. In vivo Sprague-Dawley (SD) rats experiments indicate that PLLA-(TA/Eu)_n nanofiber mats can significantly promote wound healing by improving both angiogenesis and antioxidant activity. Taken together, the functional PLLA-(TA/Eu)_n nanofiber mats can offer significant promise as wound dressing for accelerated wound healing.

Polyphenols: A Promising Avenue in Therapeutic Solutions for Wound Care

In chronic wounds, the regeneration process is compromised, which brings complexity to the therapeutic approaches that need to be adopted, while representing an enormous loss in the patients’ quality of life with consequent economical costs. Chronic wounds are highly prone to infection, which can ultimately lead to septicemia and morbidity. Classic therapies are increasing antibiotic resistance, which is becoming a critical problem beyond complex wounds. Therefore, it is essential to study new antimicrobial polymeric systems and compounds that can be effective alternatives to reduce infection, even at lower concentrations. The biological potential of polyphenols allows them to be an efficient alternative to commercial antibiotics, responding to the need to find new options for chronic wound care. Nonetheless, phenolic compounds may have some drawbacks when targeting wound applications, such as low stability and consequent decreased biological performance at the wound site. To overcome these limitations, polymeric-based systems have been developed as carriers of polyphenols for wound healing, improving its stability, controlling the release kinetics, and therefore increasing the performance and effectiveness. This review aims to highlight possible smart and bio-based wound dressings, providing an overview of the biological potential of polyphenolic agents as natural antimicrobial agents and strategies to stabilize and deliver them in the treatment of complex wounds. Polymer-based particulate systems are highlighted here due to their impact as carriers to increase polyphenols bioavailability at the wound site in different types of formulations.