Surface-Adaptive and On-Demand Antibacterial Sponge for Synergistic Rapid Hemostasis and Wound Disinfection

A facile way to fabricate a thrombin immobilized composite sponge with dual hemostatic effects for acute hemorrhage control

Uncontrolled bleeding and excessive blood loss stand as the leading causes of death in complex surgeries, civilian traumas, and military operations. Sponges have been used for developing efficiency hemostats, but most commonly used hemostatic sponges possess only one single coagulation mechanism or lack inherent blood clotting ability. Herein, we proposed simple yet innovative approaches for creating novel hemostatic composite sponges with dual hemostatic effects. Bacterial cellulose (BC) was first introduced into polyvinyl alcohol (PVA) matrix to develop a BC/PVA (CP) sponge featuring a unique cellulose-embedded porous network structure and desirable properties. Subsequently, thrombin was immobilized on CP through an easy method that combines physical adsorption and covalent binding to fabricate thrombin-carrying CP (TCP) composite sponges. The resulting composites boasted a highly porous structure, outstanding liquid-absorption capacity, low hemolysis rate, and superior biocompatibility. In vitro clotting tests revealed that TCP displayed potent coagulation capabilities, a rapid blood absorption rate, and the ability to stimulate and activate blood components along with the coagulation cascade. In vivo hemostatic assessments further confirmed that TCP offered high hemostatic efficiency and multifaceted hemostatic effects, making it suitable for the management of acute and severe bleeding.

Enhanced specific surface area and mechanical property of silk nanofibers aerogel for potential hemostasis applications

Biopolymer aerogel is a new type of material with potential applications in the biomedical field. Silk fibroin is of particular interest as a raw material with good biocompatibility and degradable. However, the low mechanical strength and small specific surface area of silk fibroin aerogels limit its further development. Herein, a fast water absorption, highly specific surface area and mechanically strong of aerogels were prepared using low crystal silk fibroin nanofibers (SNF), sol-gel process, solvent exchange and supercritical carbon dioxide (CO2) drying method. The resulting Aero-Sc displayed highly specific surface area (251 m2/g), porosity (97.6 %) and water absorption capacity (1200 %). Furthermore, with rapid water absorption and stronger erythrocyte adhesion, the Aero-Sc showed highly effective hemostasis in vitro. In vivo, animal experiments on rat liver hemorrhage model confirmed that SNF aerogels have a less blood loss (312 ± 29 mg) and faster hemostatic time (92 ± 13 s) than commercially gelatin sponge (p < 0.05). The unique properties of silk fibroin nanofibers aerogel developed in this study has great potential to be a safe and effective hemostatic medical device.

Preparation and Biochemical Activity of Copper-Coated Cellulose Nonwoven Fabric via Magnetron Sputtering and Alginate-Calcium Ion Complexation

Alginate-based materials have gained significant recognition in the medical industry due to their favorable biochemical properties. As a continuation of our previous studies, we have introduced a new composite consisting of cellulose nonwoven fabric charged with a metallic copper core (CNW-Cu0) covered with a calcium alginate (ALG-Ca2+) layer. The preparation process for these materials involved three main steps: coating the cellulose nonwoven fabric with copper via magnetron sputtering (CNW → CNW-Cu0), subsequent deposition with sodium alginate (CNW-Cu0 → CNW-Cu0/ALG-Na+), followed by cross-linking the alginate chains with calcium ions (CNW-Cu0/ALG-Na+ → CNW-Cu0/ALG-Ca2+). The primary objective of the work was to supply these composites with such biological attributes as antibacterial and hemostatic activity. Namely, equipping the antibacterial materials (copper action on representative Gram-positive and Gram-negative bacteria and fungal strains) with induction of blood plasma clotting processes (activated partial thromboplastin time (aPTT) and prothrombin time (PT)). We determined the effect of CNW-Cu0/ALG-Ca2+ materials on the viability of Peripheral blood mononuclear (PBM) cells. Moreover, we studied the interactions of CNW-Cu0/ALG-Ca2+ materials with DNA using the relaxation plasmid assay. However, results showed CNW-Cu0/ALG-Ca2+'s cytotoxic properties against PBM cells in a time-dependent manner. Furthermore, the CNW-Cu0/ALG-Ca2+ composite exhibited the potential to interact directly with DNA. The results demonstrated that the CNW-Cu0/ALG-Ca2+ composites synthesized show promising potential for wound dressing applications.

Baicalein loaded liposome with hyaluronic acid and Polyhexamethylene guanidine modification for anti methicillin-resistant Staphylococcus aureus infection

Targeting delivery to the infection site and good affinity of vehicle to the bacterial are two main concerns in therapy of bacterial infection, and on-demand release of drug is another important issue. In this work, a liposome drug delivery system (HA/P/BAI-lip) incorporated with baicalein and modified by PHMG and HA was prepared. Several characterizations were conducted to examine the physical properties of liposome. Then it was applied to treatments of MRSA induced dorsal subcutaneous abscess model and the thigh muscle infected model. The presence of guanidine group in HA/P/BAI-lip rendered the liposome satisfactory bacterial target ability and good pH sensitive properties. The lipase secreted by bacterial could promote the hydrolysis of soybean phosphatidylcholine (SPC) in liposome. The modification of HA in HA/P/BAI-lip could lead the drug system to the exact infected site where CD44 was abundant because of inflammation. The low pH microenvironment characteristic of bacterial infection could induce the swelling of liposome following by degradation. Taken together, baicalein could be released selectively at the infected site to exert antibacterial capacity. HA/P/BAI-lip showed impressive antibacterial ability and dramatically decrease the bacterial burden of infection site and alleviate the infiltration of inflammatory cells, facilitating the recovery of infection.

In Vitro Hemostatic Activity of Novel Fish Gelatin-Alginate Sponge (FGAS) Prototype

A hemostatic sponge prototype was successfully synthesized from fish gelatin as an alternative to mammalian gelatin; it was mixed with alginate in certain combinations, double cross-linked with calcium ions, and gamma irradiated at a dose of 20 kGy to improve the characteristics and effectiveness of its function as a local hemostatic agent. There were improvements in the physicochemical and mechanical properties, porosity index, absorption capacity, biodegradation properties, biocompatibility, and hemocompatibility of the fish gelatin-alginate sponge (FGAS) prototypes compared with the pure fish gelatin sponge. Hemostatic activity tests showed that the means for clotting time, prothrombin time, and activated partial thromboplastin time were shorter in the FGAS prototype than in the negative control, and there was no significant difference compared with the commercial gelatin sponge. The hemostatic mechanism of the FGAS prototype combined a passive mechanism as a concentrator factor and an active mechanism through the release of calcium ions as a coagulation factor in the coagulation cascade process.

A sodium alginate - silk fibroin biosponge loaded with thrombin: Effective hemostasis and wound healing

In trauma first aid, rapid hemostasis is a priority, extricating patients from hemorrhagic shock and infection risks. This paper explores novel hemostatic materials, using ion-crosslinking and freeze-drying techniques. Iterative experiments determined optimal conditions for the temperature-variable mixing-freeze-drying chemical reaction of sodium alginate (SA)/silk fibroin (SF). We used SA, SA/SF, SA/SF-TB and commercial hemostatic sponge control samples to perform hemostasis experiments on rat liver injury and femoral artery injury models, and to perform wound healing experiments on rat back full-layer skin. The results showed that the hemostatic time and blood loss of SA/SF-TB group rats (liver hemorrhage model: 397.17 ± 34.80 mg, 77.83 ± 7.41 s; Femoral artery bleeding model: 940.33 ± 41.93 mg, 96.83 ± 4.07 s) was significantly better than other experimental groups, and similar to the commercial group. The wound healing experiment showed that the new granulation tissue thickness of SA/SF-TB group was thicker (380.39 ± 28.56 μm) at day 14. In addition, the material properties and biocompatibility of sponges were characterized by cell experiments and in vivo embedding experiments. All the results showed that the SA/SF-TB hemostatic sponge prepared in this study could not only seal the wound quickly and stop bleeding, but also promote the growth of epidermal cells and fibroblasts and accelerate wound healing. This new material solves the shortcomings of traditional materials such as low stability, limited shelf life, high unit price, and has good biocompatibility, easy preparation, rapid hemostasis and other excellent properties. Therefore, this innovative hemostatic material has great prospects and potential in clinical applications.

Thermoresponsive Gels with Embedded Starch Microspheres for Optimized Antibacterial and Hemostatic Properties

Apart from single hemostasis, antibacterial and other functionalities are also desirable for hemostatic materials to meet clinical needs. Cationic materials have attracted great interest for antibacterial/hemostatic applications, and it is still desirable to explore rational structure design to address the challenges in balanced hemostatic/antibacterial/biocompatible properties. In this work, a series of cationic microspheres (QMS) were prepared by the facile surface modification of microporous starch microspheres with a cationic tannic acid derivate, the coating contents of which were adopted for the first optimization of surface structure and property. Thermoresponsive gels with embedded QMS (F-QMS) were further prepared by mixing a neutral thermosensitive polymer and QMS for second structure/function optimization through different QMS and loading contents. In vitro and in vivo results confirmed that the coating content plays a crucial role in the hemostatic/antibacterial/biocompatible properties of QMS, but varied coating contents of QMS only lead to a classical imperfect performance of cationic materials. Inspiringly, the F-QMS-4 gel with an optimal loading content of QMS4 (with the highest coating content) achieved a superior balanced in vitro hemostatic/antibacterial/biocompatible properties, the mechanism of which was revealed as the second regulation of cell-material/protein-material interactions. Moreover, the optimal F-QMS-4 gel exhibited a high hemostatic performance in a femoral artery injury model accompanied by the easy on-demand removal for wound healing endowed by the thermoresponsive transformation. The present work offers a promising approach for the rational design and facile preparation of cationic materials with balanced hemostatic/antibacterial/biocompatible properties.

Water-Triggered Segment Orientation of Long-Lasting Anti-Biofouling Polyurethane Coatings on Biomedical Catheters via Solvent Exchange Strategy

The formation of biofilm and thrombus on medical catheters poses a significant life-threatening concern. Hydrophilic anti-biofouling coatings upon catheter surfaces with complex shapes and narrow lumens are demonstrated to have the potential in reducing complications. However, their effectiveness is constrained by poor mechanical stability and weak substrate adhesion. Herein, a novel zwitterionic polyurethane (SUPU) with strong mechanical stability and long-term anti-biofouling is developed by controlling the ratio of sulfobetaine-diol and ureido-pyrimidinone. Once immersed in water, as-synthesized zwitterionic coating (SUPU3 SE) would undergo a water-driven segment reorientation to obtain much higher durability than its direct drying one, even under various extreme treatments, including acidic solution, abrasion, ultrasonication, flushing, and shearing, in PBS at 37 °C for 14 days. Moreover, SUPU3 SE coating could achieve a 97.1% of exceptional reducing protein fouling, complete prevention of cell adhesion, and long-lasting anti-biofilm performance even after 30 days. Finally, the good anti-thrombogenic formations of SUPU3 SE coating with bacterial treatment are validated in blood circulation through an ex vivo rabbit arteriovenous shunt model. This work provides a facile approach to fabricating stable hydrophilic coating through a simple solvent exchange to reduce thrombosis and infection of biomedical catheters.

Hemostatic patch with ultra-strengthened mechanical properties for efficient adhesion to wet surfaces

Controlling traumatic bleeding from damaged internal organs while effectively sealing the wound is critical for saving the lives of patients. Existing bioadhesives suffer from blood incompatibility, insufficient adhesion to wet surfaces, weak mechanical properties, and complex application procedures. Here, we engineered a ready-to-use hemostatic bioadhesive with ultra-strengthened mechanical properties and fatigue resistance, robust adhesion to wet tissues within a few seconds of gentle pressing, deformability to accommodate physiological function and action, and the ability to stop bleeding efficiently. The engineered hydrogel, which demonstrated high elasticity (>900%) and toughness (>4600 kJ/m3), was formed by fine-tuning a series of molecular interactions and crosslinking mechanisms involving N-hydroxysuccinimide (NHS) conjugated alginate (Alg-NHS), poly (ethylene glycol) diacrylate (PEGDA), tannic acid (TA), and Fe3+ ions. Dual adhesive moieties including mussel-inspired pyrogallol/catechol and NHS synergistically enhanced wet tissue adhesion (>400 kPa in a wound closure test). In conjunction with physical sealing, the high affinity of TA/Fe3+ for blood could further augment hemostasis. The engineered bioadhesive demonstrated excellent in vitro and in vivo biocompatibility as well as improved hemostatic efficacy as compared to commercial Surgicel®. Overall, the hydrogel design strategy described herein holds great promise for overcoming existing obstacles impeding clinical translation of engineered hemostatic bioadhesives.

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.

Aquatic Diatoms-Inspired Universal Adhesive Coacervates Triggered by Water

Adhesives with strong underwater adhesion performance are urgently needed in diverse areas. However, designing adhesives with long-term stability to diverse materials underwater in a facile way is challenging. Here, inspired by aquatic diatoms, a series of novel biomimetic universal adhesives is reported that shows tunable performance with robust and long-lasting stable underwater adhesion to various substrates, including wet biological tissues. The versatile and robust wet-contact adhesives are pre-polymerized by N-[tris(hydroxymethyl)methyl]acrylamide, n-butyl acrylate, and methylacrylic acid in dimethyl sulfoxide and spontaneously coacervated in water triggered by solvent exchange. The synergistic interaction between hydrogen bonding and hydrophobic interaction allows the hydrogels with instant and strong adhesion to various substrate surfaces. The slowly formed covalent bonds enhance cohesion and adhesion strength in hours. The spatial and timescale-dependent adhesion mechanism endows the adhesives with strong and long-lasting stable underwater adhesion to be coupled with fault-tolerant convenient surgical operations.

An All-In-One Transient Theranostic Platform for Intelligent Management of Hemorrhage

Developing theranostic devices to detect bleeding and effectively control hemorrhage in the prehospital setting is an unmet medical need. Herein, an all-in-one theranostic platform is presented, which is constructed by sandwiching silk fibroin (SF) between two silver nanowire (AgNW) based conductive electrodes to non-enzymatically diagnose local bleeding and stop the hemorrhage at the wound site. Taking advantage of the hemostatic property of natural SF, the device is composed of a shape-memory SF sponge, facilitating blood clotting, with ≈82% reduction in hemostatic time in vitro as compared with untreated blood. Furthermore, this sandwiched platform serves as a capacitive sensor that can detect bleeding and differentiate between blood and other body fluids (i.e., serum and water) via capacitance change. In addition, the AgNW electrode endows anti-infection efficiency against Escherichia coli and Staphylococcus aureus. Also, the device shows excellent biocompatibility and gradually biodegrades in vivo with no major local or systemic inflammatory responses. More importantly, the theranostic platform presents considerable hemostatic efficacy comparable with a commercial hemostat, Dengen, in rat liver bleeding models. The theranostic platform provides an unexplored strategy for the intelligent management of hemorrhage, with the potential to significantly improve patients' well-being through the integration of diagnostic and therapeutic capabilities.

Fabrication and characterization of bioprints with Lactobacillus crispatus for vaginal application

Bacterial vaginosis (BV) is characterized by low levels of lactobacilli and overgrowth of potential pathogens in the female genital tract. Current antibiotic treatments often fail to treat BV in a sustained manner, and > 50% of women experience recurrence within 6 months post-treatment. Recently, lactobacilli have shown promise for acting as probiotics by offering health benefits in BV. However, as with other active agents, probiotics often require intensive administration schedules incurring difficult user adherence. Three-dimensional (3D)-bioprinting enables fabrication of well-defined architectures with tunable release of active agents, including live mammalian cells, offering the potential for long-acting probiotic delivery. One promising bioink, gelatin alginate has been previously shown to provide structural stability, host compatibility, viable probiotic incorporation, and cellular nutrient diffusion. This study formulates and characterizes 3D-bioprinted Lactobacillus crispatus-containing gelatin alginate scaffolds for gynecologic applications. Different weight to volume (w/v) ratios of gelatin alginate were bioprinted to determine formulations with highest printing resolution, and different crosslinking reagents were evaluated for effect on scaffold integrity via mass loss and swelling measurements. Post-print viability, sustained-release, and vaginal keratinocyte cytotoxicity assays were conducted. A 10:2 (w/v) gelatin alginate formulation was selected based on line continuity and resolution, while degradation and swelling experiments demonstrated greatest structural stability with dual genipin and calcium crosslinking, showing minimal mass loss and swelling over 28 days. 3D-bioprinted L. crispatus-containing scaffolds demonstrated sustained release and proliferation of live bacteria over 28 days, without impacting viability of vaginal epithelial cells. This study provides in vitro evidence for 3D-bioprinted scaffolds as a novel strategy to sustain probiotic delivery with the ultimate goal of restoring vaginal lactobacilli following microbiological disturbances.

Design of biopolymer-based hemostatic material: Starting from molecular structures and forms

Uncontrolled bleeding remains as a leading cause of death in surgical, traumatic, and emergency situations. Management of the hemorrhage and development of hemostatic materials are paramount for patient survival. Owing to their inherent biocompatibility, biodegradability and bioactivity, biopolymers such as polysaccharides and polypeptides have been extensively researched and become a focus for the development of next-generation hemostatic materials. The construction of novel hemostatic materials requires in-depth understanding of the physiological hemostatic process, fundamental hemostatic mechanisms, and the effects of material chemistry/physics. Herein, we have recapitulated the common hemostatic strategies and development status of biopolymer-based hemostatic materials. Furthermore, the hemostatic mechanisms of various molecular structures (components and chemical modifications) are summarized from a microscopic perspective, and the design based on them are introduced. From a macroscopic perspective, the design of various forms of hemostatic materials, e.g., powder, sponge, hydrogel and gauze, is summarized and compared, which may provide an enlightenment for the optimization of hemostat design. It has also highlighted current challenges to the development of biopolymer-based hemostatic materials and proposed future directions in chemistry design, advanced form and clinical application.

Mussel-inspired polysaccharide-based sponges for hemostasis and bacteria infected wound healing

Effective bleeding control and wound protecting from infection play critical roles in the tissue healing process. However, local hemostats are not involved in the whole healing processes to promote the final healing efficiency. Here, a multi-functional mussel-inspired polysaccharide-based sponge with hemostatic, antibacterial and adhesive properties was fabricated via cryopolymerization of oxidized dextran (OD), carboxymethyl chitosan (CC) and polydopamine nanoparticles (PDA-NPs), followed by lyophilization. Combining with the adsorbed thrombin, the sponges yielded a considerably lower amount of blood than the commercially available hemostatic dressings. Benefiting from the high photo-thermal transition efficiency of PDA-NPs, the sponges exhibited excellent antibacterial activity to both gram positive and negative bacteria. Owing to the rapid hemostatic activity and effective infection resistance, the sponges illustrated the significantly acceleratory wound healing efficiency compared with the control group. The thrombin-loaded OD/CC-PDA polysaccharide-based sponge has great potential for future clinical use as wound dressing.

Injectable adhesive self-healing biocompatible hydrogel for haemostasis, wound healing, and postoperative tissue adhesion prevention in nephron-sparing surgery

Nephron-sparing surgery is a well-established treatment in patients with T1a renal cell carcinoma; however, the complex suturing process prolongs warm ischaemia time, affects the preservation of normal renal parenchymal function, and causes avoidable postoperative tissue adhesion complications, including chronic abdominal pain, intestinal obstruction, and female infertility. Hence, the design of multifunctional biomaterials with haemostasis, postoperative wound management, and postoperative tissue adhesion prevention properties for nephron-sparing surgeries is urgently needed. In this study, a series of injectable adhesive multifunctional biocompatible hydrogels were designed based on the free-radical polymerisation of monomers acryloyl-6-aminocaproic acid (AA) and N-acryloyl 2-glycine (NAG), and the ionic coordination between Ca²⁺ and the abundant carboxyl groups in AA and NAG. AA/NAG/Ca (AA, NAG, and Ca refer to acryloyl-6-aminocaproic acid, N-acryloyl 2-glycine and calcium chloride, respectively) hydrogel exhibited good mechanical properties, swelling and adhesion properties, flexibility, in vitro blood-clotting ability, and cytocompatibility. In vivo experiments on liver injury models and rat/rabbit nephron-sparing surgery models elucidated that the AA/NAG/Ca hydrogel had haemostasis performance and wound healing properties that led to short bleeding time, reduced bleeding volume, and well-organised nephron structures. An abdomen-caecum adhesion model indicated that the AA/NAG/Ca hydrogel showed excellent anti-adhesion properties. In summary, this multifunctional hydrogel exhibited potential for improving haemostasis and wound management in nephron-sparing surgeries, showing potential for clinical application. STATEMENT OF SIGNIFICANCE: Extended warm ischemia time during nephron sparing surgery negatively affected postoperative renal function due to the need for hemostasis at the wound with abundant blood supply, and postoperative wound healing and additional adhesions caused by the surgical procedure deserve attention. Based on the efficient and stable adhesion properties of hydrogels and the ability to promote wound healing. Herein, a series of adhesive self-healing biocompatible hydrogels were prepared based on free-radical polymerization of acryloyl-6-aminocaproic acid (AA) and N-acryloyl 2-glycine (NAG) and the ionic coordination between Ca²⁺ with the abundant carboxyl groups in AA and NAG. AA/NAG/Ca hydrogel showed hemostasis property in nephron sparing surgery model, promote kidney wound healing, and could perform anti-postoperative adhesion efficacy in an abdomen-caecum adhesion model.

Borrowing the Features of Biopolymers for Emerging Wound Healing Dressings: A Review

Wound dressing design is a dynamic and rapidly growing field of the medical wound-care market worldwide. Advances in technology have resulted in the development of a wide range of wound dressings that treat different types of wounds by targeting the four phases of healing. The ideal wound dressing should perform rapid healing; preserve the body’s water content; be oxygen permeable, non-adherent on the wound and hypoallergenic; and provide a barrier against external contaminants—at a reasonable cost and with minimal inconvenience to the patient. Therefore, choosing the best dressing should be based on what the wound needs and what the dressing does to achieve complete regeneration and restoration of the skin’s structure and function. Biopolymers, such as alginate (ALG), chitosan (Cs), collagen (Col), hyaluronic acid (HA) and silk fibroin (SF), are extensively used in wound management due to their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body. However, most of the formulations based on biopolymers still show various issues; thus, strategies to combine them with molecular biology approaches represent the future of wound healing. Therefore, this article provides an overview of biopolymers’ roles in wound physiology as a perspective on the development of a new generation of enhanced, naturally inspired, smart wound dressings based on blood products, stem cells and growth factors.

Engineered Hemostatic Biomaterials for Sealing Wounds

Hemostatic biomaterials show great promise in wound control for the treatment of uncontrolled bleeding associated with damaged tissues, traumatic wounds, and surgical incisions. A surge of interest has been directed at boosting hemostatic properties of bioactive materials via mechanisms triggering the coagulation cascade. A wide variety of biocompatible and biodegradable materials has been applied to the design of hemostatic platforms for rapid blood coagulation. Recent trends in the design of hemostatic agents emphasize chemical conjugation of charged moieties to biomacromolecules, physical incorporation of blood-coagulating agents in biomaterials systems, and superabsorbing materials in either dry (foams) or wet (hydrogel) states. In addition, tough bioadhesives are emerging for efficient and physical sealing of incisions. In this Review, we highlight the biomacromolecular design approaches adopted to develop hemostatic bioactive materials. We discuss the mechanistic pathways of hemostasis along with the current standard experimental procedures for characterization of the hemostasis efficacy. Finally, we discuss the potential for clinical translation of hemostatic technologies, future trends, and research opportunities for the development of next-generation surgical materials with hemostatic properties for wound management.

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.

Antimicrobial Peptides and Macromolecules for Combating Microbial Infections: From Agents to Interfaces

Bacterial resistance caused by the overuse of antibiotics and the shelter of biofilms has evolved into a global health crisis, which drives researchers to continuously explore antimicrobial molecules and strategies to fight against drug-resistant bacteria and biofilm-associated infections. Cationic antimicrobial peptides (AMPs) are considered to be a category of potential alternative for antibiotics owing to their excellent bactericidal potency and lesser likelihood of inducing drug resistance through their distinctive antimicrobial mechanisms. In this review, the hitherto reported plentiful action modes of AMPs are systematically classified into 15 types and three categories (membrane destructive, nondestructive membrane disturbance, and intracellular targeting mechanisms). Besides natural AMPs, cationic polypeptides, synthetic polymers, and biopolymers enable to achieve tunable antimicrobial properties by optimizing their structures. Subsequently, the applications of these cationic antimicrobial agents at the biointerface as contact-active surface coatings and multifunctional wound dressings are also emphasized here. At last, we provide our perspectives on the development of clinically significant cationic antimicrobials and related challenges in the translation of these materials.

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.

Hemostatic and Tissue Regeneration Performance of Novel Electrospun Chitosan-Based Materials

The application of chitosan (Ch) as a promising biopolymer with hemostatic properties and high biocompatibility is limited due to its prolonged degradation time, which, in turn, slows the repair process. In the present research, we aimed to develop new technologies to reduce the biodegradation time of Ch-based materials for hemostatic application. This study was undertaken to assess the biocompatibility and hemostatic and tissue-regeneration performance of Ch-PEO-copolymer prepared by electrospinning technique. Chitosan electrospinning membranes (ChEsM) were made from Ch and polyethylene oxide (PEO) powders for rich high-porous material with sufficient hemostatic parameters. The structure, porosity, density, antibacterial properties, in vitro degradation and biocompatibility of ChEsM were evaluated and compared to the conventional Ch sponge (ChSp). In addition, the hemostatic and bioactive performance of both materials were examined in vivo, using the liver-bleeding model in rats. A penetrating punch biopsy of the left liver lobe was performed to simulate bleeding from a non-compressible irregular wound. Appropriately shaped ChSp or ChEsM were applied to tissue lesions. Electrospinning allows us to produce high-porous membranes with relevant ChSp degradation and swelling properties. Both materials demonstrated high biocompatibility and hemostatic effectiveness in vitro. However, the antibacterial properties of ChEsM were not as good when compared to the ChSp. In vivo studies confirmed superior ChEsM biocompatibility and sufficient hemostatic performance, with tight interplay with host cells and tissues. The in vivo model showed a higher biodegradation rate of ChEsM and advanced liver repair.

A novel alginate/gelatin sponge combined with curcumin-loaded electrospun fibers for postoperative rapid hemostasis and prevention of tumor recurrence

Surgical resection of the tumor remains the preferred treatment for most solid tumors at an early stage, but surgical treatment often leads to massive bleeding and residual tumor cells. Therefore, a novel alginate/gelatin sponge combined with curcumin-loaded electrospun fibers (CFAGS) for rapid hemostasis and prevention of tumor recurrence was prepared by using an electrospinning and interpenetrating polymer network (IPN) strategy. The present results show that alginate/gelatin sponge display excellent hemostatic properties and possess more advantages than commercial gelatin hemostasis sponge. More importantly, CFAGS could control the release of curcumin, inducing curcumin to accumulate at the surgical site of the tumor, thereby inhibiting local tumor recurrence in the subcutaneous postoperative recurrence model. In addition, the sponge was safe to implant in the body and did not cause toxicity to normal tissues and organs. This approach represents a new strategy to implant a dual functional sponge at the postoperative site as an adjuvant to the surgical treatment of cancer.

An injectable serotonin–chondroitin sulfate hydrogel for bio-inspired hemostatic adhesives with high wound healing capability

An injectable hydrogel inspired by platelet clotting mediators is developed based on natural components of the human body including serotonin and chondroitin sulfate, which exhibits improved hemostatic performance and wound healing capability.

A robust poly(N-acryloyl-2-glycine)-based sponge for rapid hemostasis

The development of a hemostatic sponge that can be used for treating both arterial hemorrhage and non-compressible bleeding remains a challenge. In this work, we propose the fabrication of a robust hemostatic sponge by a hydrogen bond strengthening and in situ bubble expanding strategy in thermo-initiation polymerization. A thickening agent, carboxymethyl cellulose (CMC), is incorporated into a hydrogen bonding N-acryloyl-2-glycine (ACG) monomer and an initiator, and vortexing generates air bubbles in the viscous liquid. Heating initiates fast polymerization, and meanwhile aids in expanding of bubbles, which results in the fixation of bubbles throughout the network, and the formation of porous hydrogels. Further lyophilization of the foaming hydrogels leads to the final generation of PACG/CMC sponges with robust compressive strengths due to the hydrogen bonding interactions of PACG. PACG/CMC sponges are shown to demonstrate a tunable liquid absorption ability, in vitro hemostatic ability, better hemocompatibility and cytocompatibility. In a rat liver injury model and a femoral artery injury model, the PACG/CMC sponge can significantly reduce the bleeding time and blood loss compared with gauze and commercial gelatin sponge because of the high blood absorption ability and effective concentration of blood coagulation factors. This PACG sponge holds promising potential as a hemostatic agent applicable in an emergency.