Enlisting a Traditional Chinese Medicine to tune the gelation kinetics of a bioactive tissue adhesive for fast hemostasis or minimally invasive therapy

An Integrated All-Natural Conductive Supramolecular Hydrogel Wearable Biosensor with Enhanced Biocompatibility and Antibacterial Properties

Conductive hydrogels exhibit tremendous potential for wearable bioelectronics, biosensing, and health monitoring applications, yet concurrently enhancing their biocompatibility and antimicrobial properties remains a long-standing challenge. Herein, we report an all-natural conductive supramolecular hydrogel (GT5-DACD2-B) prepared via the Schiff base reaction between the biofriendly dialdehyde cyclodextrin and gelatin. The potent antibacterial agent fusidic acid (FA) is incorporated through host-guest inclusion, enabling 100% inhibition of Staphylococcus aureus proliferation. The biocompatibility of our hydrogel is bolstered with tannic acid (TA) facilitating antibacterial effects through interactions with gelatin, while borax augments conductivity. This supramolecular hydrogel not only exhibits stable conductivity and rapid response characteristics but also functions as a flexible sensor for monitoring human movement, facial expressions, and speech recognition. Innovatively integrating biocompatibility, antimicrobial activity, and conductivity into a single system, our work pioneers a paradigm for developing multifunctional biosensors with integrated antibacterial functionalities, paving the way for advanced wearable bioelectronics with enhanced safety and multifunctionality.

Swift Covalent Gelation Coupled with Robust Wet Adhesive Powder: A Novel Approach for Acute Massive Hemorrhage Control in Dynamic and High-Pressure Wound Environments

The quest for efficient hemostatic agents in emergency medicine is critical, particularly for managing massive hemorrhages in dynamic and high-pressure wound environments. Traditional self-gelling powders, while beneficial due to their ease of application and rapid action, fall short in such challenging conditions. To bridge this gap, the research introduces a novel self-gelling powder that combines ultrafast covalent gelation and robust wet adhesion, presenting a significant advancement in acute hemorrhage control. This ternary system comprises ε-polylysine (ε-PLL) and 4-arm polyethylene glycol succinyl succinate (4-arm-PEG-NHS) forming the hydrogel framework. Na2HPO4 functions as the "H+ sucker" to expedite the amidation reaction, slashing gelation time to under 10 s, crucial for immediate blood loss restriction. Moreover, PEG chains' hydrophilicity facilitates efficient absorption of interfacial blood, increasing the generated hydrogel's cross-linking density and strengthens its tissue bonding, thereby resulting in excellent mechanical and wet adhesion properties. In vitro experiments reveal the optimized formulation's exceptional tissue compliance, procoagulant activity, biocompatibility and antibacterial efficacy. In porcine models of heart injuries and arterial punctures, it outperforms commercial hemostatic agent Celox, confirming its rapid and effective hemostasis. Conclusively, this study presents a transformative approach to hemostasis, offering a reliable and potent solution for the emergency management of massive hemorrhage.

Injectable-Hydrogel-Based Tissue Sealant for Hemostasis, Bacteria Inhibition, and Pro-Angiogenesis in Organ Bleeding Wounds and Therapeutic Outcome Monitoring Via NIR-II Optical Imaging

Sudden hemorrhage stemming from internal organ wounds poses a grave and potentially fatal risk if left untreated. Injectable-hydrogel-based tissue sealants featuring multiple actions, including fit-to-shape in situ gelation, rapid hemostasis, pro-angiogenic, anti-bacterial and outcome tracking, are ideal for the management of organ trauma wounds. Herein, an injectable-hydrogel tissue sealant AN@CD-PEG&TQ which consists of four-arm 4-arm poly(ethylene glycol) (PEG-SC) succinimidyl carbonate), AN@CD nanoprobe, and two bioactive peptides (anti-microbial peptide Tet213 and pro-angiogenic peptide QK) is developed. Among them, AN@CD nanoparticles form through host/guest complexation of amino-group-containing β-cyclodextrin and adamantyl group, enabling in situ biomarker (NO)-activatable optoacoustic/NIR-II: Near-infrared second biological window fluorescent imaging. The ample ─NH2 groups on the surface of AN@CD readily engage in rapid cross-linking with succinimidyl ester groups located at the ends of four-arm PEG-SC. This cross-linking expedites the gelation process without necessitating additional initiators or cross-linking agents; thus, significantly enhancing both hydrogel's application convenience and biocompatibility. Bioactive peptides (Tet213 and QK) safeguard against possible bacterial infections, facilitate angiogenesis, and eventually, improve organ wounds healing. This hydrogel-based tissue sealant demonstrates superior therapeutic and bioimaging performance in various mouse models including liver hemorrhage, gastric perforation, and bacterial-infected skin wound mouse models, highlighting its potential as a high-performance wound sealant for organ bleeding wound management.

Progress in injectable hydrogels for the treatment of incompressible bleeding: an update

Uncontrollable haemorrhage from deep, noncompressible wounds remains a persistent and intractable challenge, accounting for a very high proportion of deaths in both war and disaster situations. Recently, injectable hydrogels have been increasingly studied as potential haemostatic materials, highlighting their enormous potential for the management of noncompressible haemorrhages. In this review, we summarize haemostatic mechanisms, commonly used clinical haemostatic methods, and the research progress on injectable haemostatic hydrogels. We emphasize the current status of injectable hydrogels as haemostatic materials, including their physical and chemical properties, design strategy, haemostatic mechanisms, and application in various types of wounds. We discuss the advantages and disadvantages of injectable hydrogels as haemostatic materials, as well as the opportunities and challenges involved. Finally, we propose cutting-edge research avenues to address these challenges and opportunities, including the combination of injectable hydrogels with advanced materials and innovative strategies to increase their biocompatibility and tune their degradation profile. Surface modifications for promoting cell adhesion and proliferation, as well as the delivery of growth factors or other biologics for optimal wound healing, are also suggested. We believe that this paper will inform researchers about the current status of the use of injectable haemostatic hydrogels for noncompressible haemorrhage and spark new ideas for those striving to propel this field forward.

Bioadhesives with Antimicrobial Properties

Bioadhesives with antimicrobial properties enable easier and safer treatment of wounds as compared to the traditional methods such as suturing and stapling. Composed of natural or synthetic polymers, these bioadhesives seal wounds and facilitate healing while preventing infections through the activity of locally released antimicrobial drugs, nanocomponents, or inherently antimicrobial polers. Although many different materials and strategies are employed to develop antimicrobial bioadhesives, the design of these biomaterials necessitates a prudent approach as achieving all the required properties including optimal adhesive and cohesive properties, biocompatibility, and antimicrobial activity can be challenging. Designing antimicrobial bioadhesives with tunable physical, chemical, and biological properties will shed light on the path for future advancement of bioadhesives with antimicrobial properties. In this review, the requirements and commonly used strategies for developing bioadhesives with antimicrobial properties are discussed. In particular, different methods for their synthesis and their experimental and clinical applications on a variety of organs are reviewed. Advances in the design of bioadhesives with antimicrobial properties will pave the way for a better management of wounds to increase positive clinical outcomes.

Conductive and antibacterial dual-network hydrogel for soft bioelectronics

Conductive hydrogels have shown significant potential for use in soft bioelectronics due to their unique similarities to biological tissue, including high water content, low modulus, and conductivity. However, their high water content makes them susceptible to absorbing microorganisms and promoting bacterial growth, which can trigger an immune response. Besides, the adhesion and biocompatibility of the hydrogel are not satisfactory, seriously limiting the conductive hydrogel's high-performance applications in human healthcare monitoring. Herein, the problem is addressed by introducing borax through a swelling and a semi-dehydration method into the interpenetrated network of a polyvinyl alcohol and poly(acrylic acid) hydrogel. The hydrogel exhibits both outstanding antibacterial (>99.99% toward E. coli and S. aureus) activity and high ionic conductivity, in addition to tissue-like softness, strong wet-tissue adhesion (600 J m-2 for skin), environmental stability, and excellent biocompatibility. Furthermore, the as-prepared hydrogel can serve as a biosensing conductor, showing high-quality recording and monitoring of real-time tiny yet complex muscle movements during speaking and realizing neuromodulation through low-current electronic stimulation (40 μA) of a rat's nerve. Simultaneously, the hydrogel also exhibits the capacity to accelerate wound healing. Therefore, the proposed antibacterial conductive hydrogel is a safer option for next-generation bioelectronic materials in human healthcare.

Versatile Injectable Carboxymethyl Chitosan Hydrogel for Immediate Hemostasis, Robust Tissue Adhesion Barrier, and Antibacterial Applications

Iatrogenic ulcers resulting from endoscopic submucosal dissection surgery remain a significant clinical concern due to the risk of uncontrolled bleeding. Herein, we have developed an injectable shear-thinning hydrogel cross-linked through electrostatic interactions and hydrogen bonding. The hydrogel underwent comprehensive characterization, focusing on rheological behavior, injectability, microstructure, film-forming capability, adhesion, swelling behavior, degradation kinetics, antibacterial efficacy, hemostatic performance, and biocompatibility. The incorporation of poly(vinyl alcohol) notably enhanced the internal structural stability and injection pressure, while the Laponite content influenced self-healing ability, modulus, and viscosity. Additionally, the hydrogel exhibited pH sensitivity, appropriate degradation, and swelling rates and displayed favorable film-forming and adhesion properties. Notably, it demonstrated excellent resistance against Escherichia coli and Staphylococcus aureus, highlighting its potential to create an optimal wound environment. In vivo studies further confirmed the hydrogel's exceptional hemostatic performance, positioning it as an optimal material for endoscopic submucosal dissection (ESD) surgery. Moreover, cell experiments and hemolysis tests revealed high biocompatibility, supporting their potential to facilitate the healing of iatrogenic ulcers post-ESD surgery. In conclusion, our hydrogels hold great promise as endoscopic treatment materials for ESD-induced ulcers given their outstanding properties.

Deep Eutectic Solvents-based Ionogels with Ultrafast Gelation and High Adhesion in Harsh Environments

Adhesive materials have recently drawn intensive attention due to their excellent sealing ability, thereby stimulating advances in materials science and industrial usage. However, reported adhesives usually exhibit weak adhesion strength, require high pressure for strong bonding, and display severe adhesion deterioration in various harsh environments. In this work, instead of water or organic solvents, a deep eutectic solution (DES) was used as the medium for photopolymerization of zwitterionic and polarized monomers, thus generating a novel ionogel with tunable mechanical properties. Multiple hydrogen bonds and electrostatic interactions between DES and monomers facilitated ultrafast gelation and instant bonding without any external pressure, which was rarely reported previously. Furthermore, high adhesion in different harsh environments (e.g., water, acidic and basic buffers, and saline solutions) and onto hydrophilic (e.g., glass and tissues) and hydrophobic (e.g., polymethyl methacrylate, polystyrene, and polypropylene) adherends was demonstrated. Also, high stretchability of the ionogel at extreme temperatures (-80 and 80 °C) indicated its widespread applications. Furthermore, the biocompatible ionogel showed high burst pressure onto stomach and intestine tissues to prevent liquid leakage, highlighting its potential as an adhesive patch. This ionogel provides unprecedented opportunities in the fields of packaging industry, marine engineering, medical adhesives, and electronic assembly.

Tissue adhesives for wound closure

Tissue adhesives have raised much attention from scientists in recent years. They have been extensively utilized in various medical fields, such as wound closure, due to the advantages of being simple, time-saving, and avoiding the problems and complications associated with surgical sutures. Besides, the tissue adhesives can absorb wound exudates and promote tissue repair. The rapid evolution in the field of tissue adhesives has resulted in the development of various adhesives with excellent mechanical properties and superior functions. However, many challenges still restrict their use in numerous clinical applications. In this paper, we present an up-to-date review of tissue adhesives for wound closure. We mainly discussed the fundamental design requirements for the adhesives, the fabrication of tissue adhesives, and the application of tissue adhesives on skin healing, corneal patch, and gastrointestinal tissues. We then highlighted the current challenges and unmet needs and delineated potential new clinical development directions for future adhesives. The progress in tissue adhesives will provide novel approaches for wound management and has the potential to supply effective treatments for a variety of medical applications.

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.

Design strategies for adhesive hydrogels with natural antibacterial agents as wound dressings: Status and trends

The wound healing process is usually susceptible to different bacterial infections due to the complex physiological environment, which significantly impairs wound healing. The topical application of antibiotics is not desirable for wound healing because the excessive use of antibiotics might cause bacteria to develop resistance and even the production of super bacteria, posing significant harm to human well-being. Wound dressings based on adhesive, biocompatible, and multi-functional hydrogels with natural antibacterial agents have been widely recognized as effective wound treatments. Hydrogels, which are three-dimensional (3D) polymer networks cross-linked through physical interactions or covalent bonds, are promising for topical antibacterial applications because of their excellent adhesion, antibacterial properties, and biocompatibility. To further improve the healing performance of hydrogels, various modification methods have been developed with superior biocompatibility, antibacterial activity, mechanical properties, and wound repair capabilities. This review summarizes hundreds of typical studies on various ingredients, preparation methods, antibacterial mechanisms, and internal antibacterial factors to understand adhesive hydrogels with natural antibacterial agents for wound dressings. Additionally, we provide prospects for adhesive and antibacterial hydrogels in biomedical applications and clinical research.

Bio-macromolecular design roadmap towards tough bioadhesives

Emerging sutureless wound-closure techniques have led to paradigm shifts in wound management. State-of-the-art biomaterials offer biocompatible and biodegradable platforms enabling high cohesion (toughness) and adhesion for rapid bleeding control as well as robust attachment of implantable devices. Tough bioadhesion stems from the synergistic contributions of cohesive and adhesive interactions. This Review provides a biomacromolecular design roadmap for the development of tough adhesive surgical sealants. We discuss a library of materials and methods to introduce toughness and adhesion to biomaterials. Intrinsically tough and elastic polymers are leveraged primarily by introducing strong but dynamic inter- and intramolecular interactions either through polymer chain design or using crosslink regulating additives. In addition, many efforts have been made to promote underwater adhesion via covalent/noncovalent bonds, or through micro/macro-interlock mechanisms at the tissue interfaces. The materials settings and functional additives for this purpose and the related characterization methods are reviewed. Measurements and reporting needs for fair comparisons of different materials and their properties are discussed. Finally, future directions and further research opportunities for developing tough bioadhesive surgical sealants are highlighted.

Dual-dynamic-bond cross-linked injectable hydrogel of multifunction for intervertebral disc degeneration therapy

Developing smart hydrogels with integrated and suitable properties to treat intervertebral disc degeneration (IVDD) by minimally invasive injection is of high desire in clinical application and still an ongoing challenge. In this work, an extraordinary injectable hydrogel PBNPs@OBG (Prussian blue nanoparticles@oxidized hyaluronic acid/borax/gelatin) with promising antibacterial, antioxidation, rapid gelation, and self-healing characteristics was designed via dual-dynamic-bond cross-linking among the oxidized hyaluronic acid (OHA), borax, and gelatin. The mechanical performance of the hydrogel was studied by dynamic mechanical analysis. Meanwhile, the swelling ratio and degradation level of the hydrogel was explored. Benefiting from its remarkable mechanical properties, sufficient tissue adhesiveness, and ideal shape-adaptability, the injectable PBNPs containing hydrogel was explored for IVDD therapy. Astoundingly, the as-fabricated hydrogel was able to alleviate H₂O₂-induced excessive ROS against oxidative stress trauma of nucleus pulposus, which was further revealed by theoretical calculations. Rat IVDD model was next established to estimate therapeutic effect of this PBNPs@OBG hydrogel for IVDD treatment in vivo. On the whole, combination of the smart multifunctional hydrogel and nanotechnology-mediated antioxidant therapy can serve as a fire-new general type of therapeutic strategy for IVDD and other oxidative stress-related diseases.

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.

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.

Rapidly Self-Deactivating and Injectable Succinyl Ester-Based Bioadhesives for Postoperative Antiadhesion

Postoperative adhesion not only causes severe complications for patients but also increases their economic burden. Injectable bioadhesives with adhesiveness to tissues can cover irregular wounds and stay stable in situ, which is a promising barrier for antiadhesion. However, the potential tissue adhesion caused by bioadhesives' indiscriminate adhesiveness between normal and wounded tissue is still a problem. Herein, by using poly(ethylene glycol) succinimidyl succinate (PEG-SS) and gelatin, a succinyl ester-based bioadhesive (SEgel) was fabricated with self-deactivating properties for postoperative antiadhesion. Because N-hydroxysuccinimide esters (NHS-esters) were used as the adhesive group, the bioadhesives' side in contact with the tissue built covalent anchors quickly to maintain the stability, but the superficial layer facing outward withstood fast hydrolysis and then lost its adhesion within minutes, avoiding the indiscriminate adhesiveness. In addition, because of the specific degradation behavior of succinyl ester, the SEgel with proper in vivo retention was achieved without the worry of causing foreign body reactions and unexpected tissue adhesion. Both the cecum-sidewall adhesion and hepatic adhesion models showed that the SEgel markedly reduced the severity of tissue adhesion. These results, together with the ease of the preparation process and well-proven biocompatibility of raw materials, revealed that the SEgel might be a promising solution for postoperative antiadhesion.

Tunable Biomaterials for Myocardial Tissue Regeneration: Promising New Strategies for Advanced Biointerface Control and Improved Therapeutic Outcomes

Following myocardial infarction (MI) and the natural healing process, the cardiac mechanostructure changes significantly leading to reduced contractile ability and putting additional pressure on the heart muscle thereby increasing the...

A Bioinspired Hemostatic Powder Derived from the Skin Secretion of Andrias davidianus for Rapid Hemostasis and Intraoral Wound Healing

High-performance hemostasis has become increasingly essential in treating various traumas. However, available topical hemostats still have various drawbacks and side-effects. Herein, hemostatic powders derived from the skin secretion of Andrias davidianus (SSAD) with controllable particle size are prepared using feasible frozen-ball milling following lyophilization for hemorrhage-control. Scanning electron microscopy, rheometry, and Brunauer-Emmett-Teller test are used to characterize the coagulation-promoting surface topography, rheological properties, and porous structure of the SSAD particles. The blood-coagulation assays showed that the SSAD powders can induce blood-absorption in a particle size-dependent manner. Particle sizes of the SSAD powders larger than 200 µm and smaller than 800 µm greatly affect the blood-clotting rate. Associated with the thromboelastography (TEG) and amino acid/protein composition analyses, the accessibility and diffusion of blood are mainly dependent on the wettability, adhesivity, and clotting factors of the SSAD particles. Rapid hemostasis in vivo further involves three hemorrhage models (liver, femoral artery, and tail) as well as an oral wound model, which suggest favorable hemostatic and simultaneous regenerative effects of the SSAD hemostatic powder. Considering its degradability and good biocompatibility, SSAD can be an optimal candidate for a new class of inexpensive, natural, and promising hemostatic and wound-dressing agent.

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.

A paintable ophthalmic adhesive with customizable properties based on symmetrical/asymmetrical cross-linking

In situ and efficient incision sealing for ophthalmic surgery remains unresolved. Current commercially available gel adhesives often suffer from unsuitable gelation time, difficulty in micro-delivery, and mismatched degradation period, leading to difficulties for application in ocular tissue areas. Herein, a novel hydrogel adhesive was developed based on the simultaneous crosslinking of poly(lysine) (PLL) and lysine (Lys) with an end-modified active ester multi-arm polyethylene glycol (PEG) via the amidation reaction, where the residual terminal active ester of PEG can also bond to amino groups on tissue to provide strong adhesion. Due to the different molecular structures around their amino groups, PLL and Lys can crosslink with 4-arm-PEG-NHS (active ester) respectively, to form symmetrical and asymmetrical crosslinking networks, which exhibit various mechanical properties. Therefore, just by adjusting PLL/Lys ratios, the PEG-PLL-Lys hydrogel can easily possess a suitable gelation time, appropriate mechanical properties and matched degradation rate. As a result, a paintable, readily accessible and biocompatible ophthalmic tissue adhesive (sealant) is prepared for sealing ocular tissue incision. Considering the simple strategy and outstanding performance, the PEG-PLL-Lys hydrogel is promising for clinical transformation.

Liquid Copolymers as Biodegradable Surgical Sealant

Surgical sealants are widely used to prevent seepage of fluids and liquids, promote hemostasis, and close incisions. Despite the remarkable progress the field of biomaterials has undergone, the clinical uses of surgical sealants are limited because of their short persistence time in vivo, toxicity, and high production costs. Here, the development of two complementary neat (solvent-free) prepolymers, PEG₄ -PLGA-NHS and PEG₄ -NH₂ , that harden upon mixing to yield an elastic biodegradable sealant is presented. The mechanical and rheological properties and cross-linking rate can be controlled by varying the ratio between the two prepolymers. The tested sealants show a longer persistence time compared with fibrin glue, minimal cytotoxicity in vitro, and excellent biocompatibility in vivo. The neat, multiarmed approach demonstrated here improves the mechanical and biocompatibility properties and provides a promising tissue sealant solution for wound closure in future surgical procedures.

Marine polysaccharide-based composite hydrogels containing fucoidan: Preparation, physicochemical characterization, and biocompatible evaluation

Marine polysaccharide-based hydrogels have drawn much attention for diversified biomedical applications owing to their excellent (bio)physicochemical properties. In the present work, a series of marine polysaccharide-based hydrogels composed of chitosan, alginate, or fucoidan are prepared via a facile chemical cross-linking approach in an alkali/urea aqueous system. The prepared hydrogels possess tunable microporous architecture, swelling, and biodegradable properties by changing the components and proportions of marine polysaccharides. Importantly, the developed hydrogels are mechanically robust and the maximum compressive stress is up to 28.37 ± 4.63 kPa. Furthermore, the composite hydrogels exhibit excellent cytocompatibility, blood compatibility, and histocompatibility. When implanted subcutaneously in rats, the hydrogels containing fucoidan inhibit the inflammatory response of surrounding tissue. Thus, the designed composite hydrogels are promising bio-scaffolds in biomedical applications.

A tough, adhesive, self-healable, and antibacterial plant-inspired hydrogel based on pyrogallol-borax dynamic cross-linking

Multifunctional hydrogels that integrate stretchability, adhesion, self-healing, and antibacterial properties may find use in a variety of fields including electronic skin, wound dressings, and wearable devices; however, traditional hydrogels often exhibit short-term adhesiveness, poor mechanical properties, and a lack of antibacterial activity. Herein, a plant-inspired polyacrylamide-soybean protein isolate-pyrogallol/borax (PAM-SPI-P/B) hydrogel has been developed using a facile green method based on dynamic coordination cross-linking between pyrogallol (PG) and borax. The PG-borax dynamic bonds adjusted the network structure of the hydrogels to provide greater structural integrity to the PAM-SPI double network. This hydrogel possessed a high mechanical strength (large elongation up to 760% and compressive strength up to 1.25 MPa at 80% strain), low swelling ratio, and self-healing properties. Inspired by natural polyphenols that contain adhesive molecules, the addition of pyrogallol provided the hydrogel excellent adhesion to various hydrophilic and hydrophobic substrates. And with the inhibition of pyrogallol autoxidation due to the borax protection, the hydrogel showed repeatable and durable adhesion over 20 cycles. The obtained hydrogels also exhibited good antibacterial activities against Escherichia coli and Staphylococcus aureus because they were based on pyrogallol and borax, which have antibacterial properties. Accordingly, we envision that the PAM-SPI-P/B hydrogels have great potential for use in biomimetic tissues and biosensors.