Synthesis and Properties of Hemostatic and Bacteria-Responsive in Situ Hydrogels for Emergency Treatment in Critical Situations

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.

The antibacterial and hemostatic curdlan hydrogel-loading epigallocatechin gallate for facilitating the infected wound healing

The infected wounds pose one of the major threats to human health today. To address this issue, it is necessary to develop innovative wound dressings with superior antibacterial activity and other properties. Due to its potent antibacterial, antioxidant, and immune-boosting properties, epigallocatechin gallate (EGCG) has been widely utilized. In this study, a multifunctional curdlan hydrogel loading EGCG (Cur-EGCGH3) was designed. Cur-EGCGH3 exhibited excellent physicochemical properties, good biocompatibility, hemostatic, antibacterial, and antioxidant activities. Also, ELISA data showed that Cur-EGCGH3 stimulated macrophages to secrete pro-inflammatory and pro-regenerative cytokines. Cell scratch results indicated that Cur-EGCGH3 promoted the migration of NIH3T3 and HUVECs. In vivo experiments confirmed that Cur-EGCGH3 could inhibit bacterial infection of the infected wounds, accelerate hemostasis, and promote epithelial regeneration and collagen deposition. These results demonstrated that Cur-EGCGH3 holds promise for promoting healing of the infected wounds.

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.

Functional hemostatic hydrogels: design based on procoagulant principles

Uncontrolled hemorrhage results in various complications and is currently the leading cause of death in the general population. Traditional hemostatic methods have drawbacks that may lead to ineffective hemostasis and even the risk of secondary injury. Therefore, there is an urgent need for more effective hemostatic techniques. Polymeric hemostatic materials, particularly hydrogels, are ideal due to their biocompatibility, flexibility, absorption, and versatility. Functional hemostatic hydrogels can enhance hemostasis by creating physical circumstances conducive to hemostasis or by directly interfering with the physiological processes of hemostasis. The procoagulant principles include increasing the concentration of localized hemostatic substances or establishing a physical barrier at the physical level and intervention in blood cells or the coagulation cascade at the physiological level. Moreover, synergistic hemostasis can combine these functions. However, some hydrogels are ineffective in promoting hemostasis or have a limited application scope. These defects have impeded the advancement of hemostatic hydrogels. To provide inspiration and resources for new designs, this review provides an overview of the procoagulant principles of hemostatic hydrogels. We also discuss the challenges in developing effective hemostatic hydrogels and provide viewpoints.

Preparation and antitumor study of intelligent injectable hydrogel: Carboxymethyl chitosan-aldehyde gum Arabic composite graphene oxide hydrogel

In this study, we used polyaldehyde gum Arabic (OGA) and carboxymethyl chitosan (CMCS) as a gel matrix to form an injectable self-healing hydrogel by Schiff-base bonding. Further, graphene oxide (GO) was loaded with doxorubicin (DOX) to the hydrogel, which resulted in a CMCS-OGA/GO@DOX hydrogel. We achieved a DOX drug loading capacity of 43.80 ± 1.13 %. Rheological studies showed that GO hydrogels have improved mechanical properties. The in vitro release profile showed pH responsiveness with 88.21 % DOX release at pH 5.5. Biocompatibility studies showed that the hydrogel composition had good cytocompatibility with L929 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a cell survival rate of 93.88 % within 48 h. The DOX-loaded hydrogel exhibited higher cell mortality in breast cancer cells (4 T1), with an inhibition rate of 79.4 % at 48 h. Acridine orange/ethidium bromide staining experiments on 4 T1 cells showed that when loaded with the same DOX concentration, the hydrogel significantly reduced the toxic effects on normal cells, whereas it had significant cytotoxic effects on cancer cells. This result indicates that the prepared GO hydrogel drug delivery system can serve as a novel approach for localized breast cancer treatment.

Enhanced Hemostatic and Procoagulant Efficacy of PEG/ZnO Hydrogels: A Novel Approach in Traumatic Hemorrhage Management

Managing severe bleeding, particularly in soft tissues and visceral injuries, remains a significant challenge in trauma and surgical care. Traditional hemostatic methods often fall short in wet and dynamic environments. This study addresses the critical issue of severe bleeding in soft tissues, proposing an innovative solution using a polyethylene glycol (PEG)-based hydrogel combined with zinc oxide (ZnO). The developed hydrogel forms a dual-network structure through amide bonds and metal ion chelation, resulting in enhanced mechanical properties and adhesion strength. The hydrogel, exhibiting excellent biocompatibility, is designed to release zinc ions, promoting coagulation and accelerating hemostasis. Comprehensive characterization, including gelation time, rheological properties, microstructure analysis, and swelling behavior, demonstrates the superior performance of the PEG/ZnO hydrogel compared to traditional PEG hydrogels. Mechanical tests confirm increased compression strength and adhesive properties, which are crucial for withstanding tissue dynamics. In vitro assessments reveal excellent biocompatibility and enhanced procoagulant ability attributed to ZnO. Moreover, in vivo experiments using rat liver and tail bleeding models demonstrate the remarkable hemostatic performance of the PEG/ZnO hydrogel, showcasing its potential for acute bleeding treatment in both visceral and peripheral scenarios.

Fabrication of flexible accelerated-wound-healing chitosan/dopamine-based bilayer hydrogels for strain sensors

Flexible conductive hydrogels have great potential for healthcare and human motion sensing. However, it is difficult to simultaneously achieve conductive hydrogel epidermal sensors with reliable adhesion capabilities and excellent sensing properties, as well as accelerated wound healing performance in wearable hydrogels. Here, an epidermal sensor with excellent adhesion (0.6 kPa) and tensile strain (218.0 %) properties was assembled from an easy-to-prepare bilayer antimicrobial hydrogel, which effectively accelerates wound healing, as well as for human motion sensing. The upper hydrogel layer was composed of PVA, which could effectively enhance the mechanical properties of the bilayer hydrogel. The lower hydrogel layer consisted of polyacrylamide (PAm) and chitosan-dopamine (CC-DA). PAm with good adhesion properties adhered effectively to the skin surface. CC-DA not only had adhesion properties, but also has good antibacterial effects. It inhibited the growth of bacteria, which assisted in wound healing and infection prevention. Therefore, the design of the bilayer hydrogel combined the mechanical enhancement of PVA with the adhesion properties and antimicrobial effect of PAm and CC-DA to provide better wound repair. In addition, the double-layer hydrogel with good electrical conductivity (1.65 S·m-1) could sensitively monitor the tiny electrophysiological signals emitted by the human body during exercise rehabilitation training.

Photothermal synergistic nitric oxide controlled release injectable self-healing adhesive hydrogel for biofilm eradication and wound healing

The development of injectable self-healing adhesive hydrogel dressings with excellent bactericidal activity and wound healing ability is urgently in demand for combating biofilm infections. Herein, a multifunctional hydrogel (QP/QT-MB) with near-infrared (NIR) light-activated mild photothermal/gaseous antimicrobial activity was developed based on the dynamic reversible borate bonds and hydrogen bonds crosslinking between quaternization chitosan (QCS) derivatives alternatively containing phenylboronic acid and catechol-like moieties in conjunction with the in situ encapsulation of BNN6-loaded mesoporous polydopamine (MPDA@BNN6 NPs). Given the dynamic reversible cross-linking feature, the versatile hybrid hydrogel exhibited injectability, flexibility, and rapid self-healing ability. The numerous phenylboronic acid and catechol-like moieties on the QCS backbone confer the hydrogel with specific bacterial affinity, desirable tissue adhesion, and antioxidant stress ability that enhance bactericidal activity and facilitate the regeneration of infection wounds. Under NIR irradiation, the QP/QT-MB hydrogels exhibited a desirable mild photothermal effect and NIR-activity controllable NO delivery, combined with the endogenous contact antimicrobial activity of hydrogel, contributing jointly to induce dispersal of biofilms and disruption of the bacterial plasma membranes, ultimately leading to bacteria inactivation and biofilm elimination. In vivo experiments demonstrated that the fabricated QP/QT-MB hydrogel platform was capable of inducing efficient eradication of the S. aureus biofilm in a severely infected wound model and accelerating infected wound repair by promoting collagen deposition, angiogenesis, and suppressing inflammatory responses. Additionally, the QP/QT-MB hydrogel demonstrated excellent biocompatibility in vitro and in vivo. Collectively, the hydrogel (QP/QT-MB) reveals great potential application prospects as a promising alternative in the field of biofilm-associated infection treatment.

Bacteriostatic Pickering emulsions stabilized by whey protein isolate-vanillin nanoparticles: Fabrication, characterization and stability in vitro

The purpose of this work was to prepare Pickering emulsion stabilized by bacteriostatic whey protein isolate-vanillin (WPI-Van) nanoparticles as a carrier for encapsulating vitamin E. The particle size, ζ potential, PDI were used to study the optimal preparation conditions of nanoparticles. The results showed that the optimal preparation condition was achieved at WPI/Van mass ratio of 3:1. FTIR spectra demonstrated the complexation of WPI and Van. SEM image showed spherical and slightly rough surface of nanoparticles. Inhibitory effects of nanoparticles on E. coli and S. aureus were also observed. After storage of 21 days at 4 °C, the retention rate of vitamin E in the emulsions remained 43% higher than that of unencapsulated vitamin E. Moreover, the release rate of vitamin E encapsulated in emulsions in the small intestine was 81%, indicating excellent bioaccessibility. The research can provide a new insight for production and application of antibacterial Pickering emulsions.

Rapidly in situ forming an injectable Chitosan/PEG hydrogel for intervertebral disc repair

Intervertebral disc (IVD) degeneration occurred with the increasing age or accidents has puzzled peoples in daily life. To seal IVD defect by injectable hydrogels is a promising method for slowing down IVD degeneration. Herein, we reported a rapidly in situ forming injectable chitosan/PEG hydrogel (CSMA-PEGDA-L) through integrating photo-crosslink of methacrylate chitosan (CSMA) with Schiff base reaction between CSMA and aldehyde polyethylene glycol (PEGDA). The CSMA-PEGDA-L possessed a stronger compressive strength than the photo-crosslinked CSMA-L hydrogel and Schiff-base-crosslinked CSMA-PEGDA hydrogel. This chitosan/PEG hydrogel showed low cytotoxicity from incubation experiments of nucleus pulpous cells. When implanted on the punctured IVD of rat's tail, the CSMA-PEGDA-L hydrogel could well retard the progression of IVD degeneration through physical plugging, powerfully proven by radiological and histological evaluations. This work demonstrated the strategy of in situ injectable glue may be a potential solution for prevention of IVD degeneration.

Bioinspired poly(aspartic acid) based hydrogel with ROS scavenging ability as mEGF carrier for wound repairing applications

Poly(amino acid) based self-healing hydrogels have important application in biomedications. In this research, the catechol pendant groups were imported to poly(aspartic acid) based self-healing hydrogel to improved skin adhesion and ROS scavenging performance. The poly(succinimide) (PSI) was reacted with 3,4-dihydroxyphenylalanine (DA) and then hydraziolyzed to import catechol group and hydrazide group respectively, which are responsible for mussel inspired tissue adhesion and dynamic coupling reactivity. The dopamine modified poly(aspartic hydrazide) (PDAH) was reacted with PEO90 dialdehyde (PEO90 DA) to prepare hydrogels, and the resultant hydrogel showed good biocompatibility both in vitro and in vivo. The skin adhesion strength of the mussel inspired hydrogel increased notably with enhanced radical scavenging efficiency fit for in vivo wound repairing applications. The PDAH/PEO90 DA hydrogel also showed sustained albumin release profile and the in vivo wound repairing experiment proved the mouse Epidermal Growth Factor (mEGF) loaded hydrogel as wound dressing material accelerated the wound repairing rate.

Ultrasound-triggered piezocatalytic composite hydrogels for promoting bacterial-infected wound healing

Wound healing has become one of the basic issues faced by the medical community because of the susceptibility of skin wounds to bacterial infection. As such, it is highly desired to design a nanocomposite hydrogel with excellent antibacterial activity to achieve high wound closure effectiveness. Here, based on ultrasound-triggered piezocatalytic therapy, a multifunctional hydrogel is designed to promote bacteria-infected wound healing. Under ultrasonic vibration, the surface of barium titanate (BaTiO3, BT) nanoparticles embedded in the hydrogel rapidly generate reactive oxygen species (ROS) owing to the established strong built-in electric field, endowing the hydrogel with superior antibacterial efficacy. This modality shows intriguing advantages over conventional photodynamic therapy, such as prominent soft tissue penetration ability and the avoidance of serious skin phototoxicity after systemic administration of photosensitizers. Moreover, the hydrogel based on N-[tris(hydroxymethyl)methyl]acrylamide (THM), N-(3-aminopropyl)methacrylamide hydrochloride (APMH) and oxidized hyaluronic acid (OHA) exhibits outstanding self-healing and bioadhesive properties able to accelerate full-thickness skin wound healing. Notably, compared with the widely reported mussel-inspired adhesive hydrogels, OHA/THM-APMH hydrogel due to the multiple hydrogen bonds from unique tri-hydroxyl structure overcomes the shortage that catechol groups are easily oxidized, giving it long-term and repeatable adhesion performance. Importantly, this hybrid hydrogel confines BT nanoparticles to wound area and locally induced piezoelectric catalysis under ultrasound to eradicate bacteria, markedly improving the therapeutic biosafety and exhibits great potential for harmless treatment of bacteria-infected tissues.

Tunicate-mimetic antibacterial hydrogel based on metal ion crosslinking and chitosan functionalization for wound healing

With the increasing prevalence of drug-resistant bacterial infections and frequent occurrences of slow wound healing, the development of novel antibacterial wound dressings has become a serious challenge. Hydrogel dressings have attracted extensive attention on wound healing due to their unique three-dimensional network structures and properties. However, it is a challenge to develop natural long-acting antibacterial hydrogels with multiple functions such as excellent cell affinity, wet adhesion and mechanical properties. Inspired by the wound healing mechanism and adhesion characteristics of tunicates, a series of biomimetic antibacterial hydrogels were prepared by utilizing pyrogallol-modified chitosan (GACS) and polyvinyl alcohol (PVA) as matrix, zinc ions (Zn²⁺) as crosslinking and antibacterial agents, and ethyl N-lauroyl l-arginate hydrochloride (LAE) as the antibacterial active ingredient. The morphology, swelling, water retention, degradability, wet adhesion, biocompatibility, mechanical and rheological properties of PVA/GACS/Zn²⁺/LAE hydrogels were evaluated. And the adhesion ability conferred by the pyrogallol structures enabled the hydrogel with enhanced antibacterial effect and hemostatic ability. Moreover, the in vivo experiments on rat models with full-thickness infected wounds confirmed that PVA/GACS/Zn²⁺/LAE hydrogels could efficiently kill bacteria, significantly improve the wound microenvironment, greatly promote fibroblast proliferation and collagen deposition and ultimately accelerate wound healing. In a word, this study provided a feasible and simple way for the development of biomimetic antibacterial hydrogel dressings applied in infected wounds, which could not only seal wounds with various shapes and provide a moist and antibacterial environment for wounds, but also have certain mechanical strength, excellent wound adhesion, good biocompatibility and hemostatic performance.

Recent progress of antibacterial hydrogels in wound dressings

Hydrogels are essential biomaterials due to their favorable biocompatibility, mechanical properties similar to human soft tissue extracellular matrix, and tissue repair properties. In skin wound repair, hydrogels with antibacterial functions are especially suitable for dressing applications, so novel antibacterial hydrogel wound dressings have attracted widespread attention, including the design of components, optimization of preparation methods, strategies to reduce bacterial resistance, etc. In this review, we discuss the fabrication of antibacterial hydrogel wound dressings and the challenges associated with the crosslinking methods and chemistry of the materials. We have investigated the advantages and limitations (antibacterial effects and antibacterial mechanisms) of different antibacterial components in the hydrogels to achieve good antibacterial properties, and the response of hydrogels to stimuli such as light, sound, and electricity to reduce bacterial resistance. Conclusively, we provide a systematic summary of antibacterial hydrogel wound dressings findings (crosslinking methods, antibacterial components, antibacterial methods) and an outlook on long-lasting antibacterial effects, a broader antibacterial spectrum, diversified hydrogel forms, and the future development prospects of the field.

Antibacterial coatings on orthopedic implants

With the aging of population and the rapid improvement of public health and medical level in recent years, people have had an increasing demand for orthopedic implants. However, premature implant failure and postoperative complications frequently occur due to implant-related infections, which not only increase the social and economic burden, but also greatly affect the patient's quality of life, finally restraining the clinical use of orthopedic implants. Antibacterial coatings, as an effective strategy to solve the above problems, have been extensively studied and motivated the development of novel strategies to optimize the implant. In this paper, a variety of antibacterial coatings recently developed for orthopedic implants were briefly reviewed, with the focus on the synergistic multi-mechanism antibacterial coatings, multi-functional antibacterial coatings, and smart antibacterial coatings that are more potential for clinical use, thereby providing theoretical references for further fabrication of novel and high-performance coatings satisfying the complex clinical needs.

Advances in Hydrogel Adhesives for Gastrointestinal Wound Closure and Repair

Millions of individuals undergo gastrointestinal (GI) tract surgeries each year with common postoperative complications including bleeding, perforation, anastomotic leakage, and infection. Today, techniques such as suturing and stapling seal internal wounds, and electrocoagulation stops bleeding. These methods induce secondary damage to the tissue and can be technically difficult to perform depending on the wound site location. To overcome these challenges and to further advance wound closure, hydrogel adhesives are being investigated to specifically target GI tract wounds because of their atraumatic nature, fluid-tight sealing capability, favorable wound healing properties, and facile application. However, challenges remain that limit their use, such as weak underwater adhesive strength, slow gelation, and/or acidic degradation. In this review, we summarize recent advances in hydrogel adhesives to treat various GI tract wounds, with a focus on novel material designs and compositions to combat the environment-specific challenges of GI injury. We conclude with a discussion of potential opportunities from both research and clinical perspectives.

A Choline Phosphoryl-Conjugated Chitosan/Oxidized Dextran Injectable Self-Healing Hydrogel for Improved Hemostatic Efficacy

The development of injectable hydrogels with good biocompatibility, self-healing, and superior hemostatic properties is highly desirable in emergency and clinical applications. Herein, we report an in situ injectable and self-healing hemostatic hydrogel based on choline phosphoryl functionalized chitosan (CS-g-CP) and oxidized dextran (ODex). The CP groups were hypothesized to accelerate hemostasis by facilitating erythrocyte adhesion and aggregation. Our results reveal that the CS-g-CP/ODex hydrogels exhibit enhanced blood clotting and erythrocyte adhesion/aggregation capacities compared to those of the CS/ODex hydrogels. The CS-g-CP₅₀/ODex₇₅ hydrogel presents rapid gelation time, good mechanical strength and tissue adhesiveness, satisfactory bursting pressure, and favorable biocompatibility. The hemostatic ability of the CS-g-CP₅₀/ODex₇₅ hydrogel was significantly improved compared to that of the CS/ODex hydrogel and commercial fibrin sealant in the rat tail amputation and liver/spleen injury models. Our study highlights the positive and synergistic effects of CP groups on hemostasis and strongly supports the CS-g-CP₅₀/ODex₇₅ hydrogel as a promising adhesive for hemorrhage control.

Succinic Ester-Based Shape Memory Gelatin Sponge for Noncompressible Hemorrhage without Hindering Tissue Regeneration

Shape memory sponges are very promising in stopping the bleeding from noncompressible and narrow entrance wounds. However, few shape memory sponges have fast degradable properties in order to not hinder tissue healing. In this work, based on cryopolymerization, a succinic ester-based sponge (Ssponge) is fabricated using gelatin and bi-polyethylene glycol-succinimidyl succinate (Bi-PEG-SS). Compared with the commercially available gelatin sponge (Csponge), Ssponge possesses better water/blood absorption ability and higher mechanical pressure over the surrounding tissues. Moreover, in the models of massive liver hemorrhage after transection and noncompressive liver wounds by penetration, Ssponge exhibits a better hemostasis performance than Csponge. Furthermore, in a liver regeneration model, Ssponge-treated livers shows higher regeneration speed compared with Csponge, including a lower injury score, more cavity-like tissues, less fibrosis and enhanced tissue regeneration. Overall, it is shown that Ssponge, with a fast degradation behavior, is not only highly efficient in stopping bleeding but also not detrimental for tissue healing, possessing promising clinical translational potential.

Biomass-derived ultrafast cross-linked hydrogels with double dynamic bonds for hemostasis and wound healing

Developing novel hemostatic materials with accelerating wound healing functions has raised widespread attention recently. To adapt to irregular and incompressible wounds, we fabricated a series of biomass-derived ultrafast cross-linked adhesive hydrogels with adjustable gelation time and injectable properties through Schiff-base and ionic coordinate bonds among catechol-conjugated gelatin (GelDA), dialdehyde cellulose nanocrystals (DACNCs), calcium ions (Ca²⁺) and ferric iron (Fe³⁺). The fast-gelling hydrogels possess adjustable gelation time and mechanical properties by altering the contents of DACNCs and Fe³⁺. With double-dynamic-bond crosslinking, the hydrogels are endowed with the desired self-healing and injectable performance compared to gelatin-based hydrogels without DACNCs. Additionally, the hydrogels present enhanced adhesiveness, NIR responsiveness and antibacterial activity with the introduction of catechol groups and the formation of catechol-Fe complexes. Both in vitro and in vivo hemostatic assays and degradation experiments confirm that the hydrogels achieve rapid hemostasis and display fantastic biodegradability. As demonstrated by a rat full-thickness skin defect model, the hydrogels with multifunctionality remarkably accelerate the regeneration of wound tissues. Thus, the ultrafast cross-linked hydrogels are potentially valuable as hemostatic materials for wound healing applications in the biomedical field.

Carboxymethyl Chitosan/Tannic Acid Hydrogel with Antibacterial, Hemostasis, and Antioxidant Properties Promoting Skin Wound Repair

Local causes of slow wound healing include infection and wound hemorrhage. Using sodium bicarbonate as a neutralizer, a variety of carboxymethyl chitosan-tannic acid (CMC-TA) composite hydrogels solidify through hydrogen bonding in this study. The best-performing hydrogel was synthesized by altering the concentration of TA and exhibited remarkable mechanical properties and biocompatibility. Following in vitro characterization tests, the CMC-TA hydrogel exhibited remarkable antibacterial and antioxidant properties, as well as quick hemostasis capabilities. In the in vivo wound healing study, the results showed that the CMC-TA hydrogel could relieve inflammation and promote the recovery of skin incision, re-epithelialization, and collagen deposition. Overall, this multifunctional hydrogel could be an ideal wound dressing for the clinical therapy of full-thickness wounds.

Review of lipoic acid: From a clinical therapeutic agent to various emerging biomaterials

Lipoic acid (LA), an endogenous small molecule in organisms, has been extensively used for the highly efficient clinical treatment of malignant diseases, which include diabetes, Alzheimer's disease, and cancer over the past seven decades. Tremendous progresses have been made on the use of LA in nanomedicine for the development of various biomaterials because of its unique biological properties and highly adaptable structure since the first discovery. However, there are few reviews thus far, to our knowledge, summarizing this hot subject of research of LA and its derived biomaterials. For this purpose, we present herein the first comprehensive summary on the design and development of LA and its derived materials for biomedical applications. This review first discusses the therapeutic use of LA followed by the description of synthesis and preclinical study of LA-derived-small molecules. The applications of various LA and poly (lipoic acid) (PLA)-derived-biomaterials are next summarized in detail with an emphasis on the use of LA for the design of biomaterials and the diverse properties. This review describes the development of LA from a clinical therapeutic agent to a building unit of various biomaterials field, which will promote the further discovery of new therapeutic uses of LA as therapeutic agents and facile development of LA-based derivates with greater performance for biomedical applications.

Cohesion Design-Led Tough Sealants with Controllably Dissolvable Properties

Leakage is a common complication of surgeries and injuries, causing pain and increasing the economic burden on patients. Although there are commercially available sealants for leakage prevention, few of them are entirely satisfactory due to disease transmission, high cost, and poor biocompatibility. In addition, none of them can be controllably removed for further healthcare. In this paper, by using cohesion design, a sealant based on amino-modified gelatin (AG) and bi-polyethylene glycol N-hydroxysuccinimide active ester (Bi-PEG-SS) was fabricated. To increase the bursting pressure, the cohesion strength was enhanced by increasing the cross-linking density of the sealant. To endow the sealant with controllably dissolvable properties, the smart succinic ester units were introduced into the cohesion network. Both the in vitro and in vivo experiments showed that this sealant processed high bursting pressure with efficient hemorrhage control. Moreover, no side effects were observed after 7 days of in vivo sealing, including little inflammation and fibrogenesis. These results, together with the easy availability of the raw materials, revealed that this sealant might be a promising alternative for leakage sealing.

Graphene-ophicalcite heterogeneous composite sponge for rapid hemostasis

Synergistic functionalization of interface coagulation stimulation and liquid absorption capacity is the key to improve the hemostatic efficiency of hemostats. Herein, we prepared a graphene-ophicalcite (OPH) heterogeneous composite sponge (GOCS) by using the heterogeneous gradient composite strategy. The sponge took cross-linked graphene sponge (CGS) as the main skeleton, allowing the OPH to be controllably positioned on the surface of GOCS. The heterogeneous strategy gave full play to the advantages of the material. On the one hand, GOCS had excellent liquid absorption ability, which enriched blood cells and other coagulation components at the wound interface after contacting blood. On the other hand, the OPH at the interface obviously activated platelets and rapidly triggered coagulation cascade reactions, exhibiting fast response and feedback characteristics for coagulation signals. Under the synergistic effects, the blood clotting index value of GOCS was reduced to 33.87 ± 9.97%, which was significantly lower than those of OPH (46.33 ± 16.85%) and CGS (67.53 ± 5.35%). Importantly, GOCS rapidly stopped bleeding within 51 s in the rat femoral artery model, suggesting its great potential in the field of hemostasis. Therefore, this study provides a new idea for the design and preparation of hemostatic materials via heterogeneous strategy.

Self-healing hydrogel based on polyphosphate-conjugated pectin with hemostatic property for wound healing applications

Self-healing hydrogels have important application in hemostasis and wound repairing. In this research, pectin based self-healing hydrogel was fabricated with conjugated polyphosphate for hemostatic and wound healing applications. The hydrogel formed without any stimulus and hydrogel kept its biocompatibility; at the same time, the hydrogel degraded completely by enzyme and in vivo. The polyphosphate conjugated hydrogel also showed self-healing property and sustained release performance with strong coagulation characteristic. More importantly, the in vivo experiment revealed that the polyphosphate conjugated hydrogel reduced the blood loss and hemostasis time in hemorrhage model; meanwhile, the hydrogel accelerated the wound repairing rate of the open wound by preventing bacterial invasion. Altogether, the PolyP conjugated hemostatic pectin-based hydrogel is a good candidate as wound dressing material applied in clinic or open wound repairing.

In situ forming injectable γ-poly(glutamic acid)/PEG adhesive hydrogels for hemorrhage control

Rapidly in situ forming adhesive hydrogels are promising candidates for efficient hemostasis due to their easy administration and minimal invasion. However, development of biocompatible and high-performance hemostatic hydrogels without any additional toxic agents remains a challenge. Herein, a series of novel injectable adhesive hydrogels based on N-hydroxysuccinimide (NHS) modified γ-poly(glutamic acid) (γPGA-NHS) and tetra-armed poly(ethylene glycol) amine (Tetra-PEG-NH₂) were developed. Among all samples, PGA₁₀-PEG₁₅ and PGA₁₀-PEG₂₀ hydrogels with higher PEG contents exhibited rapid gelation time (<20 s), strong mechanical strength (compression modulus up to ∼75 kPa), good adhesive properties (∼15 kPa), and satisfactory burst pressure (∼18-20 kPa). As a result, PGA₁₀-PEG₁₅ and PGA₁₀-PEG₂₀ hydrogels showed a remarkable reduction in hemostasis time and blood loss compared with gauze and fibrin glue. More importantly, the PGA₁₀-PEG₂₀ hydrogel was also successfully used to seal femoral arterial trauma. Subcutaneous implantation experiments indicated a good biocompatibility of the hydrogels in vivo. All these results strongly support that the developed PGA-PEG hydrogels could serve as promising hemostatic agents in emergency and clinical situations.

Mussel-inspired multifunctional hydrogel dressing with hemostasis, hypoglycemic, photothermal antibacterial properties on diabetic wounds

To meticulously establish an efficient photothermal multifunctional hydrogel dressing is a prospective strategy for the treatment of diabetic chronic wounds. Herein, glucose oxidase (GOx) was added to polydopamine/acrylamide (PDA/AM) hydrogels to reduce hyperglycemia to a normal level (3.9-6.1 mmol L^-1) and enhance compressive properties (55 kPa) and adhesive properties (32.69 kPa), which are capable of hemostasis in the wound. Then, MnO₂ nanoparticles were encapsulated into a polydopamine/acrylamide (PDA/AM) hydrogel, endowing it with excellent antibacterial properties (E. coli and S. aureus were 97.87% and 99.99%) under the irradiation of 808 nm NIR; meanwhile, the biofilm was eliminated completely. Besides, O₂ was generated (18 mg mL^-1) by the decomposition of H₂O₂ under the catalysis of MnO₂, which could accelerate the formation of angiogenesis and promote the crawling and proliferation of cells. Furthermore, the diabetic wound in vivo treated with the PDA/AM/GOx/MnO₂ hydrogel had a less inflammatory response and faster healing speed, which was completely healed in 14 days. Therefore, the multifunctional hydrogels with the capability of high compressible, hemostasis, antibacterial, hyperglycemia manipulation, and O₂ generation, demonstrate promise in diabetic chronic wound dressing.

Cohesion mechanisms for bioadhesives

Due to the nature of non-invasive wound closure, the ability to close different forms of leaks, and the potential to immobilize various devices, bioadhesives are altering clinical practices. As one of the vital factors, bioadhesives' strength is determined by adhesion and cohesion mechanisms. As well as being essential for adhesion strength, the cohesion mechanism also influences their bulk functions and the way the adhesives can be applied. Although there are many published reports on various adhesion mechanisms, cohesion mechanisms have rarely been addressed. In this review, we have summarized the most used cohesion mechanisms. Furthermore, the relationship of cohesion strategies and adhesion strategies has been discussed, including employing the same functional groups harnessed for adhesion, using combinational approaches, and exploiting different strategies for cohesion mechanism. By providing a comprehensive insight into cohesion strategies, the paper has been integrated to offer a roadmap to facilitate the commercialization of bioadhesives.

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Bioadhesive are altering clinical practices.

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Bioadhesives for medical applications needs different cohesion strategies.

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Better understanding of cohesion mechanism can design suitable bioadhesives.

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.

Poly(aspartic acid) based self-healing hydrogel with blood coagulation characteristic for rapid hemostasis and wound healing applications

External hemorrhage, caused by insufficient hemostasis or surgical failure, could leads to shock or even tissue necrosis as the results of excessive blood loss. Furthermore, delayed coagulation, chronic inflammation, bacterial infection and slow cell proliferation are also major challenges to effective wound repairing. In this study, a novel hemostatic hydrogel was prepared by cross-linking inorganic polyphosphate (PolyP) conjugated poly(aspartic acid) hydrazide (PAHP) and PEO₉₀ dialdehyde (PEO₉₀ DA). Based on the dynamic characteristics of the acylhydrazone bond, the hydrogel could repair its cracks when broken under external forces. At the same time, the hydrogel showed outstanding biocompatibility and tissue adhesion with remarkable hemostatic performance. The New Zealand rabbit ear artery used as a in vivo hemostasis model and the results showed the PAHP hydrogel could stop bleeding of traumatic wound and reduce blood loss significantly. Meanwhile, the PAHP hydrogel presented intrinsic antibacterial activity, thus could inhibit the bacterial infection. In addition, the hydrogel loaded with mouse epidermal growth factor (mEGF) accelerated the wound repair rate and promoted the regeneration of fresh tissue in the mouse full thickness skin defect model. Altogether, the PAHP hydrogels exhibits great potential in the biomedical application, especially in wound dressing materials and tissue repairing.

Stimuli-Responsive Antibacterial Materials: Molecular Structures, Design Principles, and Biomedical Applications

Infections are regarded as the most severe complication associated with human health, which are urgent to be solved. Stimuli-responsive materials are appealing therapeutic platforms for antibacterial treatments, which provide great potential for accurate theranostics. In this review, the advantages, the response mechanisms, and the key design principles of stimuli-responsive antibacterial materials are highlighted. The biomedical applications, the current challenges, and future directions of stimuli-responsive antibacterial materials are also discussed. First, the categories of stimuli-responsive antibacterial materials are comprehensively itemized based on different sources of stimuli, including external physical environmental stimuli (e.g., temperature, light, electricity, salt, etc.) and bacterial metabolites stimuli (e.g., acid, enzyme, redox, etc.). Second, structural characteristics, design principles, and biomedical applications of the responsive materials are discussed, and the underlying interrelationships are revealed. The molecular structures and design principles are closely related to the sources of stimuli. Finally, the challenging issues of stimuli-responsive materials are proposed. This review will provide scientific guidance to promote the clinical applications of stimuli-responsive antibacterial materials.

Catalyst-Free Click Chemistry for Engineering Chondroitin Sulfate-Multiarmed PEG Hydrogels for Skin Tissue Engineering

The quest for an ideal biomaterial perfectly matching the microenvironment of the surrounding tissues and cells is an endless challenge within biomedical research, in addition to integrating this with a facile and sustainable technology for its preparation. Engineering hydrogels through click chemistry would promote the sustainable invention of tailor-made hydrogels. Herein, we disclose a versatile and facile catalyst-free click chemistry for the generation of an innovative hydrogel by combining chondroitin sulfate (CS) and polyethylene glycol (PEG). Various multi-armed PEG-Norbornene (A-PEG-N) with different molecular sizes were investigated to generate crosslinked copolymers with tunable rheological and mechanical properties. The crosslinked and mechanically stable porous hydrogels could be generated by simply mixing the two clickable Tetrazine-CS (TCS) and A-PEG-N components, generating a self-standing hydrogel within minutes. The leading candidate (TCS-8A-PEG-N (40 kD)), based on the mechanical and biocompatibility results, was further employed as a scaffold to improve wound closure and blood flow in vivo. The hydrogel demonstrated not only enhanced blood perfusion and an increased number of blood vessels, but also desirable fibrous matrix orientation and normal collagen deposition. Taken together, these results demonstrate the potential of the hydrogel to improve wound repair and hold promise for in situ skin tissue engineering applications.

Injectable Self-Healing First-Aid Tissue Adhesives with Outstanding Hemostatic and Antibacterial Performances for Trauma Emergency Care

Soft-tissue trauma emergency caused by natural disasters and traffic accidents is highly prevalent, which can result in massive bleeding, pathogen infection, and even death. Although numerous tissue adhesives can bind to tissue surfaces and cover wounds, most of them still have several deficiencies, including long gelation time, poor adhesive strength, and anti-infection, making them inappropriate for use as first-aid bandages. Herein, injectable and self-healing four-arm-PEG-CHO/polyethyleneimine (PEI) tissue adhesives as liquid first-aid supplies are developed via the dynamic Schiff base reaction for trauma emergency. It is found that the prepared hydrogel adhesives exhibit short and controlled gelation time (9∼88 s), strong adhesive strength, and excellent antibacterial ability. Their hemostatic and antimicrobial performances can be tailored by the mass ratio of four-arm-PEG-CHO/PEI. Moreover, in vitro biological assays display that the developed tissue adhesives possess satisfactory cyto/hemocompatibility. Importantly, in vivo the designed adhesives show fast hemostatic capacity and excellent anti-infection as compared to commercial Prontosan gel. Thus, this work indicates that the four-arm-PEG-CHO/PEI first-aid tissue adhesives display great potential for wound emergency management.

Natural Scaffolds Used for Liver Regeneration: A Narrative Update

Annually chronic liver diseases cause two million death worldwide. Although liver transplantation (LT) is still considered the best therapeutic option, the limited number of donated livers and lifelong side effects of LT has led researchers to seek alternative therapies. Tissue engineering (TE) as a promising method is considered for liver repair and regeneration. TE uses natural or synthetic scaffolds, functional somatic cells, multipotent stem cells, and growth factors to develop new organs. Biological scaffolds are notable in TE because of their capacity to mimic extracellular matrices, biodegradability, and biocompatibility. Moreover, natural scaffolds are classified based on their source and function in three separate groups. Hemostat-based scaffolds as the first group were reviewed for their application in coagulation in liver injury or surgery. Furthermore, recent studies showed improvement in the function of biological hydrogels in liver regeneration and vascularity. In addition, different applications of natural scaffolds were discussed and compared with synthetic scaffolds. Finally, we focused on the efforts to improve the performance of decellularized extracellular matrixes for liver implantation.

Lysozyme Amyloid Fibril-Integrated PEG Injectable Hydrogel Adhesive with Improved Antiswelling and Antibacterial Capabilities

Hydrogels with inherent antibacterial activities have been attracting increasing attention, particularly for biomedical applications. Biology provides a range of materials and mechanisms to meet diverse requirements for bacterial combating. Lysozyme after fibrillation (LZMF) has a much superior antibacterial ability than globular native lysozyme due to its decreased positive charges and increased hydrophobic β-sheet component. Here, we propose to design a poly(ethylene glycol) (PEG) cross-linked LZMF composite antibacterial hydrogel by utilizing the nucleophilic substitution reaction between LZMF and N-hydroxysuccinimide end groups on four-arm PEG-NHS. The generated PEG-LZMF hydrogel is bacteria-resistant both in vitro and in vivo as expected and has good biocompatibility. Moreover, the volume expansion of PEG can be significantly inhibited due to the presence of hydrophobic lysozyme amyloid fibrils. In addition, the relatively fast cross-linking reaction can make PEG-LZMF both injectable and shape-compatible. The simultaneous reaction with tissue-exposed -NH₂ or -SH also confers a tissue-adhesive ability. We envision that this hydrophobic lysozyme amyloid fibril-integrated PEG composite hydrogel can effectively adhere/protect open wounds and internal incisions and suppress pathogen infection through a biomimetic antibacterial mechanism. Considering the simple fabrication process, this multifunctional PEG-LZMF antibacterial hydrogel is promising for clinical transformation.

Efficient, biosafe and tissue adhesive hemostatic cotton gauze with controlled balance of hydrophilicity and hydrophobicity

Cotton gauze is a widely used topical hemostatic material for bleeding control, but its high blood absorption capacity tends to cause extra blood loss. Therefore, development of rapid hemostatic cotton gauze with less blood loss is of great significance. Here, we develop an efficient hemostatic cotton gauze whose surface is slightly modified with a catechol compound which features a flexible long hydrophobic alkyl chain terminated with a catechol group. Its hemostatic performance in animal injuries is superior to standard cotton gauze and Combat GauzeTM. Its biosafety is similar to cotton gauze and rebleeding hardly occurs when the gauze is removed. Here, we show its hemostatic capability is attributable to the rapid formation of big and thick primary erythrocyte clots, due to its effective controlling of blood movement through blocking effect from tissue adhesion by catechol, blood wicking in cotton, and the hydrophobic effect from long alkyl chains.

Hemostatic biomaterials to halt non-compressible hemorrhage

Non-compressible hemorrhage is an unmet clinical challenge, which occurs in inaccessible sites in the body where compression cannot be applied to stop bleeding. Current treatments reliant on blood transfusion are...

Polymeric Materials for Hemostatic Wound Healing

Hemorrhage is one of the greatest threats to life on the battlefield, accounting for 50% of total deaths. Nearly 86% of combat deaths occur within the first 30 min after wounding. While external wound injuries can be treated mostly using visual inspection, abdominal or internal hemorrhages are more challenging to treat with regular hemostatic dressings because of deep wounds and points of injury that cannot be located properly. The need to treat trauma wounds from limbs, abdomen, liver, stomach, colon, spleen, arterial, venous, and/or parenchymal hemorrhage accompanied by severe bleeding requires an immediate solution that the first responders can apply to reduce rapid exsanguinations from external wounds, including in military operations. This necessitates the development of a unique, easy-to-use, FDA-approved hemostatic treatment that can deliver the agent in less than 30 s and stop bleeding within the first 1 to 2 min at the point of injury without application of manual pressure on the wounded area.

A simple strategy for efficient preparation of networks based on poly(2-isopropenyl-2-oxazoline), poly(ethylene oxide), and selected biologically active compounds: Novel hydrogels with antibacterial properties

Novel polymer networks composed of biocompatible, hydrophilic poly(2-isopropenyl-2-oxazoline) (PiPOx), poly(ethylene oxide) (PEO), and selected biologically active compounds (cinnamic acid, benzoic acid or eugenol) were developed for potential antimicrobial applications. The applied crosslinking method, based on the addition reaction between oxazoline pendant groups and chosen reagents containing carboxyl functions, is relatively facile, free from by-products, and thus well suited for biomaterial preparation. The one-step synthesis enabled efficient network formation with high gel contents (>90%). The chemical structure of the newly synthesized networks was characterized using Fourier Transform Infrared-attenuated Total Reflection spectroscopy (FTIR-ATR) and ¹³C Magic-Angle Spinning (MAS) NMR. To evaluate the suitability for biomedical applications, swelling in water and the mechanical properties of the networks were investigated. The antimicrobial efficacy of the prepared hydrogels was tested in neutral medium both by the agar diffusion method and in the liquid culture against Gram-positive and Gram-negative strains: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Enterobacter cloaceae. All the tested hydrogels showed an antimicrobial effect in the direct contact zone. Moreover, the eugenol loaded hydrogel expressed a broader bacteriostatic effect inhibiting microorganism growth beyond the contact zone. These form-stable hydrogels with antibacterial properties may be of interest for designing materials dedicated to biomedical applications.

Polydopamine Nanosheets Doped Injectable Hydrogel with Nitric Oxide Release and Photothermal Effects for Bacterial Ablation and Wound Healing

The development of wound dressings with combined antibacterial activities and pro-healing functions has always been an intractable medical task for treating bacterial wound infection. Herein, a novel injectable hybrid hydrogel dressing is developed, which is doped with nitric oxide (NO) donor (N,N'-di-sec-butyl-N,N'-dinitroso-1,4-phenylenediamine, BNN6) loaded two-dimensional polydopamine nanosheets (PDA NS). The hydrogel matrix is in situ formed through dynamic Schiff base crosslinking between hydrazide-modified γ-polyglutamic acid (γ-PGA-ADH) and aldehyde-terminated Pluronic F127 (F127-CHO). Under 808 nm irradiation, the embedded PDA NS exhibits outstanding photothermal transform properties (56.1%) and on-demand NO release. The combination of photothermal and NO gas therapy with a synergistic antibacterial effect works on both Escherichia coli and Staphylococcus aureus in vitro. Furthermore, a full-thickness skin defect model also demonstrates that the hybrid hydrogel shows outstanding antibacterial properties and effectively accelerates the wound healing process. Overall, this study provides a facile and promising method for the fabrication of PDA NS based multifunctional hydrogel dressing for the application of infectious skin wound healing.

Chitosan-based multifunctional flexible hemostatic bio-hydrogel

Realizing the potential application of chitosan as an effective biomedical hemostatic agent has become an emerging research hotspot. However, fabricating a flexible chitosan-based hemostatic bio-hydrogel with self-adhesion feature in humid conditions and rapid hemostasis capability remains a challenge. Herein, we reported the development of chitosan-based hydrogels (DCS-PEGSH gels) with typical multilevel pore structures, which were cross-linked by 3-(3,4-dihydroxyphenyl) propionic acid-modified chitosan (DCS) and sebacic acid-terminated polyethylene glycol modified by p-hydroxybenzaldehyde (PEGSH). By precisely regulating the proportion of PEGSH, the fabricated bio-hydrogels displayed favorable cytocompatibility, suitable stretchability (∼780%), and blood absorbability (1300% ± 50%). Moreover, the strong adhesion (∼68.5 kPa) of the assembled bio-hydrogel ensured its firm adherence on pigskin and on bleeding wound in both static and dynamic humid environments without shedding, thus providing a long service life. The fabricated hydrogels exhibited shorter blood clotting time (50 s) and lower blood clotting index (BCI, 41) than the commercial chitosan sponge (288 s, BCI 65). Notably, the amount of blood loss from the liver in mice was reduced by almost 90% as compared to that for the control group. This study paves a solid way for developing a chitosan-based hydrogel with self-adhesive, self-healing, stretchability, biocompatibility, and antibacterial and antioxidant properties through molecular design and structural regulation, which will enable the biomedical application of chitosan in emergency hemostasis, particularly in joints and extremities. STATEMENT OF SIGNIFICANCE: The design and preparation of multifunctional integrated green adhesive bio-hydrogels while avoiding the use of organic solvents and toxic chemical reagents has been an emerging challenge. Herein, a flexible chitosan-based hemostatic bio-hydrogel that integrates multifunctional properties was successfully synthesized. The bio-hydrogel displayed suitable stretchability (780%) and blood absorbability (1300% ± 50%). Moreover, the strong adhesion (68.5 kPa) ensured firm adherence of the assembled hydrogel on pigskin and on the bleeding wound site in both static and dynamic humid environments without shedding, thus providing a long service life. In addition, the designed hydrogel showed good compatibility and antibacterial performance. The dynamic Schiff base endowed the bio-hydrogel with excellent self-healing performance without any external stimuli.