A mussel-inspired double-crosslinked tissue adhesive intended for internal medical use

Mussel-Inspired Sonochemical Nanocomposite Coating on Catheters for Prevention of Urinary Infections

Catheter-associated urinary tract infections are the most common hospital-acquired infections and cause patient discomfort, increased morbidity, and prolonged stays, altogether posing a huge burden on healthcare services. Colonization occurs upon insertion, or later by ascending microbes from the rich periurethral flora, and is therefore virtually unavoidable by medical procedures. Importantly, the dwell time is a significant risk factor for bacteriuria because it gives biofilms time to develop and mature. This is why we engineer antibacterial and antibiofilm coating through ultrasound- and nanoparticle-assisted self-assembly on silicone surfaces and validate it thoroughly in vitro and in vivo. To this end, we combine bimetallic silver/gold nanoparticles, which exercise both biocidal and structural roles, with dopamine-modified gelatin in a facile and substrate-independent sonochemical coating process. The latter mussel-inspired bioadhesive potentiates the activity and durability of the coating while attenuating the intrinsic toxicity of silver. As a result, our approach effectively reduces biofilm formation in a hydrodynamic model of the human bladder and prevents bacteriuria in catheterized rabbits during a week of placement, outperforming conventional silicone catheters. These results substantiate the practical use of nanoparticle-biopolymer composites in combination with ultrasound for the antimicrobial functionalization of indwelling medical devices.

Integrating hydrogels manipulate ECM deposition after spinal cord injury for specific neural reconnections via neuronal relays

A bioinspired hydrogel composed of hyaluronic acid-graft-dopamine (HADA) and a designer peptide HGF-(RADA)4-DGDRGDS (HRR) was presented to enhance tissue integration following spinal cord injury (SCI). The HADA/HRR hydrogel manipulated the infiltration of PDGFRβ+ cells in a parallel pattern, transforming dense scars into an aligned fibrous substrate that guided axonal regrowth. Further incorporation of NT3 and curcumin promoted axonal regrowth and survival of interneurons at lesion borders, which served as relays for establishing heterogeneous axon connections in a target-specific manner. Notable improvements in motor, sensory, and bladder functions resulted in rats with complete spinal cord transection. The HADA/HRR + NT3/Cur hydrogel promoted V2a neuron accumulation in ventral spinal cord, facilitating the recovery of locomotor function. Meanwhile, the establishment of heterogeneous neural connections across the hemisected lesion of canines was documented in a target-specific manner via neuronal relays, significantly improving motor functions. Therefore, biomaterials can inspire beneficial biological activities for SCI repair.

Epidermal growth factor-loaded, dehydrated physical microgel-formed adhesive hydrogel enables integrated care of wet wounds

Integrated wound care, a sequential process of promoting wound hemostasis, sealing, and healing, is of great clinical significance. However, the wet environment of wounds poses formidable challenges for integrated care. Herein, we developed an epidermal growth factor (EGF)-loaded, dehydrated physical microgel (DPM)-formed adhesive hydrogel for the integrated care of wet wounds. The DPMs were designed using the rational combination of hygroscopicity and reversible crosslinking of physical hydrogels. Unlike regular bioadhesives, which consider interfacial water as a barrier to adhesion, DPMs utilize water to form desirable adhesive structures. The hygroscopicity allowed the DPMs to absorb interfacial water and subsequently, the interfacial adhesion was realized by the interactions between tissue and DPMs. The reversible crosslinks further enabled DPMs to integrate into hydrogels (DPM-Gels), thus achieving wet adhesion. Importantly, the water-absorbing gelation mode of DPMs enabled facile loading of biologically active EGF to promote wound healing. We demonstrated that the DPM-Gels possessed wet tissue adhesive performance, with about 40 times the wet adhesive strength of fibrin glue and about 4 times the burst pressure of human blood pressure. Upon application at the injury site, the EGF-loaded DPM-Gels sequentially promoted efficient wound hemostasis, stable sealing, and quick healing, achieving integrated care of wet wounds.

Antibacterial polylysine-containing hydrogels for hemostatic and wound healing applications: preparation methods, current advances and future perspectives

The treatment of various types of wounds such as dermal wounds, multidrug resistant bacteria-infected wounds, and chronic diabetic wounds is one of the critical challenges facing healthcare systems. Delayed wound healing can impose a remarkable burden on patients and health care professionals. In this case, given their unique three-dimensional porous structure, biocompatibility, high hydrophilicity, capability to provide a moist environment while absorbing wound exudate, permeability to both gas and oxygen, and tunable mechanical properties, hydrogels with antibacterial function are one of the most promising candidates for wound healing applications. Polylysine is a cationic polymer with the advantages of inherent antibacterial properties, biodegradability, and biocompatibility. Therefore, its utilization to engineer antibacterial hydrogels for accelerating wound healing is of great interest. In this review, we initially discuss polylysine properties, and then focus on the most recent advances in polylysine-containing hydrogels (since 2016) prepared using various chemical and physical crosslinking methods for hemostasis and wound healing applications. Finally, the challenges and future directions in the engineering of these antibacterial hydrogels for wound healing are discussed.

Coagulant Protein-Free Blood Coagulation Using Catechol-Conjugated Adhesive Chitosan/Gelatin Double Layer

Since the discovery of polyphenolic underwater adhesion in marine mussels, researchers strive to emulate this natural phenomenon in the development of adhesive hemostatic materials. In this study, bio-inspired hemostatic materials that lead to pseudo-active blood coagulation, utilizing traditionally passive polymer matrices of chitosan and gelatin are developed. The two-layer configuration, consisting of a thin, blood-clotting catechol-conjugated chitosan (CHI-C) layer and a thick, barrier-functioning gelatin (Geln) ad-layer, maximizes hemostatic capability and usability. The unique combination of coagulant protein-free condition with CHI-C showcases not only coagulopathy-independent blood clotting properties (efficacy) but also exceptional clinical potential, meeting all necessary biocompatibility evaluation (safety) without inclusion of conventional coagulation triggering proteins such as thrombin or fibrinogen. As a result, the CHI-C/Geln is approved by the Ministry of Food and Drug Safety (MFDS, Republic of Korea) as a class II medical device. Hemostatic efficacy observed in multiple animal models further demonstrates the superiority of CHI-C/Geln sponges in achieving quick hemostasis compared to standard treatments. This study not only enriches the growing body of research on mussel-inspired materials but also emphasizes the potential of biomimicry in developing advanced medical materials, contributing a promising avenue toward development of readily accessible and affordable hemostatic materials.

Enhancing the properties of soy protein isolate and dialdehyde starch films for food packaging applications through tannic acid crosslinking

The utilization of naturally derived biodegradable polymers, including proteins, polysaccharides, and polyphenols, holds significant promise in addressing environmental concerns and reducing reliance on nonrenewable resources. This study aimed to develop films with enhanced UV resistance and antibacterial capabilities by covalently cross-linking soy protein isolate (SPI) with dialdehyde starch (DAS) through the incorporation of tannic acid (TA). The covalent crosslinking of TA with DAS and SPI was shown to establish a stable chemical cross-linking network. The tensile strength of the resulting SPI/DAS/15TA film exhibited a remarkable increase of 208.27 % compared to SPI alone and 52.99 % compared to SPI/DAS film. Notably, the UV absorption range of SPI/DAS/10TA films extended from 200 nm to 389 nm. This augmentation can be attributed to the oxidation of TA's phenolic hydroxyl groups to quinone under alkaline conditions, which then facilitated cross-linking with the SPI chain via Michael addition and Schiff base reactions. Furthermore, the film demonstrated robust antibacterial properties due to the incorporation of TA. Collectively, the observed properties highlight the significant potential of the SPI/DAS/10TA film for applications in food packaging, where its enhanced mechanical strength, UV resistance, and antibacterial characteristics can contribute to improved product preservation and safety.

Recent Advances in the Degradability and Applications of Tissue Adhesives Based on Biodegradable Polymers

In clinical practice, tissue adhesives have emerged as an alternative tool for wound treatments due to their advantages in ease of use, rapid application, less pain, and minimal tissue damage. Since most tissue adhesives are designed for internal use or wound treatments, the biodegradation of adhesives is important. To endow tissue adhesives with biodegradability, in the past few decades, various biodegradable polymers, either natural polymers (such as chitosan, hyaluronic acid, gelatin, chondroitin sulfate, starch, sodium alginate, glucans, pectin, functional proteins, and peptides) or synthetic polymers (such as poly(lactic acid), polyurethanes, polycaprolactone, and poly(lactic-co-glycolic acid)), have been utilized to develop novel biodegradable tissue adhesives. Incorporated biodegradable polymers are degraded in vivo with time under specific conditions, leading to the destruction of the structure and the further degradation of tissue adhesives. In this review, we first summarize the strategies of utilizing biodegradable polymers to develop tissue adhesives. Furthermore, we provide a symmetric overview of the biodegradable polymers used for tissue adhesives, with a specific focus on the degradability and applications of these tissue adhesives. Additionally, the challenges and perspectives of biodegradable polymer-based tissue adhesives are discussed. We expect that this review can provide new inspirations for the design of novel biodegradable tissue adhesives for biomedical applications.

Ultrafast gelling bioadhesive based on blood plasma and gelatin for wound closure and healing

Tissue adhesives offer a plethora of advantages in achieving efficient wound closure over conventional sutures and staples. Such materials are of great value, especially in cases where suturing could potentially damage tissues or compromise blood flow or in cases of hard-to-reach areas. Besides providing wound closure, the tissue adhesives must also facilitate wound healing. Previously, plasma-based tissue adhesives and similar bioinspired strategies have been utilized to aid in wound healing. Still, their application is constrained by factors such as high cost, diminished biocompatibility, prolonged gelation times, inadequate swelling, quick resorption, as well as short-term and inconsistent efficacy. To address these limitations, we report the development of a highly biocompatible and ultrafast-gelling tissue adhesive hydrogels. Freeze-dried platelet-rich plasma, heat-denatured freeze-dried platelet-poor plasma, and gelatin were utilized as the base matrix. Gelation was initiated by adding tetrakis hydroxymethyl phosphonium chloride. The fabricated gels displayed rapid gelation (3-4 s), low swelling, increased proliferation, and migration against L929 cells and had porcine skin tissue adhesion strength similar to that of plasma-based commercial glue (Tisseel®).

Multifunctional polypeptide-based hydrogel bio-adhesives with pro-healing activities and their working principles

Wound healing is a complex physiological process involving hemostasis, inflammation, proliferation, and tissue remodeling. Therefore, there is an urgent need for suitable wound dressings for effective and systematical wound management. Polypeptide-based hydrogel bio-adhesives offer unique advantages and are ideal candidates. However, comprehensive reviews on polypeptide-based hydrogel bio-adhesives for wound healing are still lacking. In this review, the physiological mechanisms and evaluation parameters of wound healing were first described in detail. Then, the working principles of hydrogel bio-adhesives were summarized. Recent advances made in multifunctional polypeptide-based hydrogel bio-adhesives involving gelatin, silk fibroin, fibrin, keratin, poly-γ-glutamic acid, ɛ-poly-lysine, serum albumin, and elastin with pro-healing activities in wound healing and tissue repair were reviewed. Finally, the current status, challenges, developments, and future trends of polypeptide-based hydrogel bio-adhesives were discussed, hoping that further developments would be stimulated to meet the growing needs of their clinical applications.

3D Bioprinting-Based Dopamine-Coupled Flexible Material for Nasal Cartilage Repair

INTRODUCTION

Since 3D printing can be used to design implants according to the specific conditions of patients, it has become an emerging technology in tissue engineering and regenerative medicine. How to improve the mechanical, elastic and adhesion properties of 3D-printed photocrosslinked hydrogels is the focus of cartilage tissue repair and reconstruction research.

MATERIALS AND METHODS

We established a strategy for toughening hydrogels by mixing GelMA-DOPA (GD), which is prepared by coupling dopamine (DA) with GelMA, with HAMA, bacterial cellulose (BC) to produce composite hydrogels (HB-GD). HB-GD hydrogel scaffolds were characterized in vitro by scanning electron microscopy (SEM), Young's modulus, swelling property and rheological property tests. And biocompatibility and chondrogenic ability were tested by live/dead staining, DNA quantitative analysis and immunofluorescence staining. Combined with 3D bioprinting technology, mouse chondrocytes (ADTC5) were added to form a biological chain to construct an in vitro model, and the feasibility of the model for nasal cartilage regeneration was verified by cytology evaluation.

RESULTS

With the increase of GD concentration, the toughness of the composite hydrogel increased (47.0 ± 2.7 kPa (HB-5GD)-158 ± 3.2 kPa (HB-20GD)), and it had excellent swelling properties, rheological properties and printing properties. The HB-GD composite hydrogel promoted the proliferation and differentiation of ATDC5. Cells in 3D printed scaffolds had higher survival rates (> 95%) and better protein expression than the encapsulated cultures.

CONCLUSION

The HB-10GD hydrogel can be made into a porous scaffold with precise shape, good internal pore structure, high mechanical strength and good swelling rate through extrusion 3D printing.

NO LEVEL ASSIGNED

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Bioinspired adhesive hydrogel based on serotonin-modified gelatin and oxidized hyaluronic acid for rapid hemostasis and wound healing

A hybrid hydrogel system (GSOHA) consisting of serotonin-grafted gelatin and oxidized hyaluronic acid (OHA) was developed in this study to efficiently control bleeding and prevent bacterial infections during surgery and trauma. The study results showed that the incorporation of serotonin successfully produced hydrogels with rapid hemostatic, antibacterial, and antioxidant properties. The GSOHA hydrogel exhibited considerably stronger tissue adhesion (15.55 ± 0.36 kPa) to porcine skin than the commercial fibrin glue (1.09 ± 0.04 kPa). In addition, the hydrogel could rapidly absorb blood cells and stimulate cell conjugation with serotonin addition. In vitro experiments using endothelial cells and erythrocytes demonstrated the excellent biocompatibility and hemocompatibility of the hydrogel. Most importantly, the GSOHA hydrogel accelerated the wound healing process in a full-thickness skin defect mice model, and the histological staining results demonstrated that GSOHA significantly promoted collagen deposition and vascularization. In conclusion, this study demonstrated the significant potential of the GSOHA hydrogel as an adhesive dressing for rapid hemostasis and wound healing.

Recent Development and Applications of Polydopamine in Tissue Repair and Regeneration Biomaterials

The various tissue damages are a severe problem to human health. The limited human tissue regenerate ability requires suitable biomaterials to help damage tissue repair and regeneration. Therefore, many researchers devoted themselves to exploring biomaterials suitable for tissue repair and regeneration. Polydopamine (PDA) as a natural and multifunctional material which is inspired by mussel has been widely applied in different biomaterials. The excellent properties of PDA, such as strong adhesion, photothermal and high drug-loaded capacity, seem to be born for tissue repair and regeneration. Furthermore, PDA combined with different materials can exert unexpected effects. Thus, to inspire researchers, this review summarizes the recent and representative development of PDA biomaterials in tissue repair and regeneration. This article focuses on why apply PDA in these biomaterials and what PDA can do in different tissue injuries.

Adhesivity-tuned bioactive gelatin/gellan hybrid gels drive efficient wound healing

Gelatin-based hydrogels have been widely used for wound healing applications. However, increase in ligand density and reduction in pore size with increasing gelatin concentration may delay wound healing by limiting cell infiltration. In this study, we address this shortcoming by combining gelatin with gellan-which is super hydrophilic and non-adhesive to cells. We show that UV crosslinked hybrid gels composed of methacrylated gelatin (GelMA) and methacrylated gellan gum (mGG), possess considerably larger pores and improved mechanical properties compared to GelMA gels. Reduced spreading and reduced formation of focal adhesions on hybrid gels combined with lower contractility and faster detachment upon trypsin-induced de-adhesion suggests that hybrid gels are less adhesive than GelMA gels. Gradual release of fibroblast growth factor (FGF) and silver nanoparticles (AgNPs) incorporated in hybrid gels not only boosts cell migration, but also confers anti-bacterial activity against gram-positive and gram-negative bacteria at concentrations nontoxic to cells. Full thickness wound healing in Wistar rats revealed increased granulation tissue formation in hybrid gels, fastest epithelialization and highest collagen deposition in rats treated with FGF entrapped hybrid gels. Together, our results demonstrate how adhesive tuning and incorporation of bioactive factors can be synergistically combined for achieving complete wound healing.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Injectable Nanoengineered Adhesive Hydrogel for Treating Enterocutaneous Fistulas

Enterocutaneous fistula (ECF) is a severe medical condition where an abnormal connection forms between the gastrointestinal tract and skin. ECFs are, in most cases, a result of surgical complications such as missed enterotomies or anastomotic leaks. The constant leakage of enteric and fecal contents from the fistula site leads to skin breakdown and increases the risk of infection. Despite advances in surgical techniques and postoperative management, ECF accounts for significant mortality rates, estimated between 15-20%, and causes debilitating morbidity. Therefore, there is a critical need for a simple and effective method to seal and heal ECF. Injectable hydrogels with combined properties of robust mechanical properties and cell infiltration/proliferation have the potential to block and heal ECF. Herein, we report the development of an injectable nanoengineered adhesive hydrogel (INAH) composed of a synthetic nanosilicate (Laponite®) and a gelatin-dopamine conjugate for treating ECF. The hydrogel undergoes fast cross-linking using a co-injection method, resulting in a matrix with improved mechanical and adhesive properties. INAH demonstrates appreciable blood clotting abilities and is cytocompatible with fibroblasts. The adhesive properties of the hydrogel are demonstrated in ex vivo adhesion models with skin and arteries, where the volume stability in the hydrated internal environment facilitates maintaining strong adhesion. In vivo assessments reveal that the INAH is biocompatible, supporting cell infiltration and extracellular matrix deposition while not forming fibrotic tissue. These findings suggest that this INAH holds promising translational potential for sealing and healing ECF.

Carboxymethyl chitosan dopamine conjugates: Synthesis and evaluation for intranasal anti Parkinson therapy

With respect to the Parkinson's disease (PD), herein, we aimed at synthetizing and characterizing two novel macromolecular conjugates where dopamine (DA) was linked to N,O-carboxymethyl chitosan or O-carboxymethyl chitosan, being both conjugates obtained from an organic solvent free synthetic procedure. They were characterized by FT-IR, 1H NMR spectroscopies, whereas thermal analysis (including Differential Scanning Calorimetry and Thermal Gravimetric Analysis) revealed good stability of the two conjugates after exposure at temperatures close to 300 °C. Release studies in simulated nasal fluid elucidated that a faster release occurred since O-carboxymethyl chitosan-DA conjugate maybe due to the less steric hindrance exerted by the polymeric moiety. The CMCS-DA conjugates prepared in aqueous medium may self-assembly to form polymeric micelles and/or may form polymeric nanoparticles. TEM and Photon correlation spectroscopy lent support for polymeric nanoparticle formation. Moreover, such CMCS-DA conjugates showed antioxidant activity, as demonstrated by DPPH radical scavenging assay. Finally, cytocompatibility studies with neuroblastoma SH-SY5Y cells showed no cytotoxicity of both conjugates, whereas their uptake increased from 2.5 to 24 h and demonstrated in 40-66 % of cells.

Naturally derived highly resilient and adhesive hydrogels with application as surgical adhesive

The inadequacy of conventional surgical techniques for wound closure and repair in soft and resilient tissues may lead to poor healing outcomes such as local tissue fibrosis and contracture. Therefore, the development of adhesive and resilient hydrogels that can adhere firmly to irregular and dynamic wound interfaces and provide a "tension-free proximity" environment for tissue regeneration has become extremely important. Herein, we describe an integrated modeling-experiment-application strategy for engineering a promising hydrogel-based bioadhesive based on recombinant human collagen (RHC) and catechol-modified hyaluronic acid (HA-Cat). Molecular modeling and simulations were used to verify and explore the hypothesis that RHC and HA-Cat can form an assembly complex through physical interactions. The complex was synergistically crosslinked via a catechol/o-quinone coupling reaction and a carbodiimide coupling reactions, resulting in superior hydrogels with strong adhesion and resilience properties. The application of this bioadhesive to tissue adhesion and wound sealing in vivo was successfully demonstrated, with an optimum collagen index, epidermal thickness, and lowest scar width. Furthermore, subcutaneous implantation demonstrated that the bioadhesive exhibited good biocompatibility and degradability. This newly developed hydrogel may be a highly promising surgical adhesive for medical applications, including wound closure and repair.

Development of artificial bone graft via in vitro endochondral ossification (ECO) strategy for bone repair

Endochondral ossification (ECO) is a form of bone formation whereby the newly deposited bone replaces the cartilage template. A decellularized artificial cartilage graft (dLhCG), which is composed of hyaline cartilage matrixes, has been developed in our previous study. Herein, the osteogenesis of bone marrow-derived MSCs in the dLhCG through chondrogenic differentiation, chondrocyte hypertrophy, and subsequent transdifferentiation induction has been investigated by simulating the physiological processes of ECO for repairing critical-sized bone defects. The MSCs were recellularized into dLhCGs and subsequently allowed to undergo a 14-day proliferation period (mrLhCG). Following this, the mrLhCG constructs were subjected to two distinct differentiation induction protocols to achieve osteogenic differentiation: chondrogenic medium followed by chondrocytes culture medium with a high concentration of fetal bovine serum (CGCC group) and canonical osteogenesis inducing medium (OI group). The formation of a newly developed artificial bone graft, ossified dLhCG (OsLhCG), as well as its capability of aiding bone defect reconstruction were characterized by in vitro and in vivo trials, such as mRNA sequencing, quantitative real-time PCR (qPCR), immunohistochemistry, the greater omentum implantation in nude mice, and repair for the critical-sized femoral defects in rats. The results reveal that the differentiation induction of MSCs in the CGCC group can realize in vitro ECO through chondrogenic differentiation, hypertrophy, and transdifferentiation, while the MSCs in the OI group, as expected, realize ossification through direct osteogenic differentiation. The angiogenesis and osteogenesis of OsLhCG were proved by being implanted into the greater omentum of nude mice. Besides, the OsLhCG exhibits the capability to achieve the repair of critical-size femoral defects.

Injectable hydrogels: An emerging therapeutic strategy for cartilage regeneration

The impairment of articular cartilage due to traumatic incidents or osteoarthritis has posed significant challenges for healthcare practitioners, researchers, and individuals suffering from these conditions. Due to the absence of an approved treatment strategy for the complete restoration of cartilage defects to their native state, the tissue condition often deteriorates over time, leading to osteoarthritic (OA). However, recent advancements in the field of regenerative medicine have unveiled promising prospects through the utilization of injectable hydrogels. This versatile class of biomaterials, characterized by their ability to emulate the characteristics of native articular cartilage, offers the distinct advantage of minimally invasive administration directly to the site of damage. These hydrogels can also serve as ideal delivery vehicles for a diverse range of bioactive agents, including growth factors, anti-inflammatory drugs, steroids, and cells. The controlled release of such biologically active molecules from hydrogel scaffolds can accelerate cartilage healing, stimulate chondrogenesis, and modulate the inflammatory microenvironment to halt osteoarthritic progression. The present review aims to describe the methods used to design injectable hydrogels, expound upon their applications as delivery vehicles of biologically active molecules, and provide an update on recent advances in leveraging these delivery systems to foster articular cartilage regeneration.

Benzeneboronic-alginate/quaternized chitosan-catechol powder with rapid self-gelation, wet adhesion, biodegradation and antibacterial activity for non-compressible hemorrhage control

Although hemostatic powders have excellent adaptability for irregular and inaccessible wounds, their hemostasis for continuous bleeding or bleeding wounds of non-compressible organs remains a critical challenge. Herein, a series of benzeneboronic acid-modified sodium alginate/catechol-modified quaternized chitosan (SA-BA/QCS-C, SBQCC) powders is developed by borate ester crosslinking for non-compressible hemorrhage control. SBQCC powders possess remarkable tissue adhesion, rapid self-gelation, good cytocompatibility and antibacterial activity against S. aureus and E. coil. The blood coagulation assays show that SBQCC powders display excellent blood clotting ability due to the synergistic effect of SA-BA and QCS-C. The SBQCC2 powder with the SA-BA to QCS-C mass ratio of 5 to 3 has the greatest effect on the blood-clotting rate. Upon depositing SBQCC2 powder to bleeding wounds of rabbit liver, the powder can absorb a large amount of blood and form a stable hydrogel physical barrier at the bleeding wounds in situ to achieve non-pressing rapid hemostasis. The SBQCC2 powder also has good biocompatibility and can be degraded in vivo. Altogether, the SBQCC powders can be a promising candidate for rapid hemostasis, and these findings may provide a new perspective for improving the hemostatic efficiency of the hemostatic powder in biomedical fields.

Injectable, pore-forming, self-healing, and adhesive hyaluronan hydrogels for soft tissue engineering applications

Most existing injectable hydrogels are non-porous, thereby lacking a microporous structure to promote cell ingrowth. Also, most hydrogels do not effectively adhere to the host tissue. The present study describes an injectable double network hydrogel formed by combining two hyaluronic acid (HA) derivatives, namely dopamine grafted HA (DAHA) and methacrylated HA (HAMA). These constituents instantly form a physically crosslinked network through Fe3+-dopamine coordination, and confer fast gelation, pore formation, and self-healing properties to the hydrogel. Photocroslinked upon UV exposure, HAMA forms a chemically crosslinked network, thereby improving mechanical and degradation properties. The adhesive properties of this hydrogel are attributed to the presence of dopamine groups, inspired by mussel creatures. Proper modification of HA chains was confirmed by NMR spectroscopy. The physical, mechanical, rheological, and biological properties of the new hydrogels were quantified in wet laboratory conditions. The results revealed that the DAHA/HAMA hydrogel rapidly forms a self-healing microporous adhesive scaffold with a 26.9 µm pore size, 29.4 kPa compressive modulus, and 12.8 kPa adhesion strength in under 6 s. These findings suggest that the new hydrogel is a promising candidate for in situ repair of soft tissues, particularly mechanically dynamic ones such as the vocal folds, cartilage, and dermis.

Polysaccharides, proteins, and synthetic polymers based multimodal hydrogels for various biomedical applications: A review

Nature-derived or biologically encouraged hydrogels have attracted considerable interest in numerous biomedical applications owing to their multidimensional utility and effectiveness. The internal architecture of a hydrogel network, the chemistry of the raw materials involved, interaction across the interface of counter ions, and the ability to mimic the extracellular matrix (ECM) govern the clinical efficacy of the designed hydrogels. This review focuses on the mechanistic viewpoint of different biologically driven/inspired biomacromolecules that encourages the architectural development of hydrogel networks. In addition, the advantage of hydrogels by mimicking the ECM and the significance of the raw material selection as an indicator of bioinertness is deeply elaborated in the review. Furthermore, the article reviews and describes the application of polysaccharides, proteins, and synthetic polymer-based multimodal hydrogels inspired by or derived from nature in different biomedical areas. The review discusses the challenges and opportunities in biomaterials along with future prospects in terms of their applications in biodevices or functional components for human health issues. This review provides information on the strategy and inspiration from nature that can be used to develop a link between multimodal hydrogels as the main frame and its utility in biomedical applications as the primary target.

Polymer nanomaterials for use as adjuvant surgical tools

Materials employed in the treatment of conditions encountered in surgical and clinical practice frequently face barriers in translation to application. Shortcomings can be generalized through their reduced mechanical stability, difficulty in handling, and inability to conform or adhere to complex tissue surfaces. To overcome an amalgam of challenges, research has sought the utilization of polymer-derived nanomaterials deposited in various fashions and formulations to improve the application and outcomes of surgical and clinical interventions. Clinically prevalent applications include topical wound dressings, tissue adhesives, surgical sealants, hemostats, and adhesion barriers, all of which have displayed the potential to act as superior alternatives to current materials used in surgical procedures. In this review, emphasis will be placed not only on applications, but also on various design strategies employed in fabrication. This review is designed to provide a broad and thought-provoking understanding of nanomaterials as adjuvant tools for the assisted treatment of pathologies prevalent in surgery. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Poly-Catecholic Functionalization of Biomolecules for Rapid Gelation, Robust Injectable Bioadhesion, and Near-Infrared Responsiveness

Mussel-inspired catechol-functionalization of degradable natural biomaterials has garnered significant interest as an approach to achieve bioadhesion for sutureless wound closure. However, conjugation capacity in standard coupling reactions, such as carbodiimide chemistry, is limited by low yield and lack of abundant conjugation sites. Here, a simple oxidative polymerization step before conjugation of catechol-carrying molecules (i.e., 3,4-dihydroxy-l-phenylalanine, l-DOPA) as a potential approach to amplify catechol function in bioadhesion of natural gelatin biomaterials is proposed. Solutions of gelatin modified with poly(l-DOPA) moieties (GelDOPA) are characterized by faster physical gelation and increased viscosity, providing better wound control on double-curved tissue surfaces compared to those of l-DOPA-conjugated gelatin. Physical hydrogels treated topically with low concentrations of NaIO4 solutions are crosslinked on-demand via through-thickness diffusion. Poly(l-DOPA) conjugates enhance crosslinking density compared to l-DOPA conjugated gelatin, resulting in lower swelling and enhanced cohesion in physiological conditions. Together with cohesion, more robust bioadhesion at body temperature is achieved by poly(l-DOPA) conjugates, exceeding those of commercial sealants. Further, poly(l-DOPA) motifs introduced photothermal responsiveness via near-infrared (NIR) irradiation for controlled drug release and potential applications in photothermal therapy. The above functionalities, along with antibacterial activity, render the proposed approach an effective biomaterial design strategy for wound closure applications.

Progress of tissue adhesives based on proteins and synthetic polymers

In recent years, polymer-based tissue adhesives (TAs) have been developed as an alternative to sutures to close and seal incisions or wounds owing to their ease of use, rapid application time, low cost, and minimal tissue damage. Although significant research is being conducted to develop new TAs with improved performances using different strategies, the applications of TAs are limited by several factors, such as weak adhesion strength and poor mechanical properties. Therefore, the next-generation advanced TAs with biomimetic and multifunctional properties should be developed. Herein, we review the requirements, adhesive performances, characteristics, adhesive mechanisms, applications, commercial products, and advantages and disadvantages of proteins- and synthetic polymer-based TAs. Furthermore, future perspectives in the field of TA-based research have been discussed.

Utilizing Robust Design to Optimize Composite Bioadhesive for Promoting Dermal Wound Repair

Catechol-modified bioadhesives generate hydrogen peroxide (H2O2) during the process of curing. A robust design experiment was utilized to tune the H2O2 release profile and adhesive performance of a catechol-modified polyethylene glycol (PEG) containing silica particles (SiP). An L9 orthogonal array was used to determine the relative contributions of four factors (the PEG architecture, PEG concentration, phosphate-buffered saline (PBS) concentration, and SiP concentration) at three factor levels to the performance of the composite adhesive. The PEG architecture and SiP wt% contributed the most to the variation in the results associated with the H2O2 release profile, as both factors affected the crosslinking of the adhesive matrix and SiP actively degraded the H2O2. The predicted values from this robust design experiment were used to select the adhesive formulations that released 40-80 µM of H2O2 and evaluate their ability to promote wound healing in a full-thickness murine dermal wound model. The treatment with the composite adhesive drastically increased the rate of the wound healing when compared to the untreated controls, while minimizing the epidermal hyperplasia. The release of H2O2 from the catechol and soluble silica from the SiP contributed to the recruitment of keratinocytes to the wound site and effectively promoted the wound healing.

Gelatin hydrogel reinforced with mussel-inspired polydopamine-functionalized nanohydroxyapatite for bone regeneration

Developing high-strength hydrogels with biocompatibility and bone conductibility is still desirable for bone regeneration. The nanohydroxyapatite (nHA) was incorporated into a dopamine-modified gelatin (Gel-DA) hydrogel system to create a highly biomimetic native bone tissue microenvironment. In addition, to further increase the cross-linking density between nHA and Gel-DA, nHA was functionalized by mussel-inspired polydopamine (PDA). Compared with nHA, adding polydopamine functionalized nHA (PHA) increased the compressive strength of Gel-Da hydrogel from 449.54 ± 180.32 kPa to 611.18 ± 211.86 kPa without affecting its microstructure. Besides, the gelation time of Gel-DA hydrogels with PHA incorporation (GD-PHA) was controllable from 49.47 ± 7.93 to 88.11 ± 31.18 s, contributing to its injectable ability in clinical applications. In addition, the abundant phenolic hydroxyl group of PHA was beneficial to the cell adhesion and proliferation of Gel-DA hydrogels, leading to the excellent biocompatibility of Gel-PHA hydrogels. Notably, the GD-PHA hydrogels could accelerate the bone repair efficiency in the rat model of the femoral defect. In conclusion, our results suggest the Gel-PHA hydrogel with osteoconductivity, biocompatibility, and enhanced mechanical properties is a potential bone repair material.

Genome-wide analysis for nanofiber induced global gene expression profile: A study in MC3T3-E1 cells by RNA-Seq

Nanofibers are one of the attractive biomaterials that can provide unique environments to direct cell behaviors. However, how nanofiber structure affects the global gene expression of laden cells remains unclear. Herein, high-throughput mRNA sequencing (RNA-seq) is applied to analyze the transcriptome of the MC3T3-E1 cells (a model osteoblast cell line) cultured on electrospun nanofibers. The cell-adhesive poly(L-lactide) nanofibers and membranes are developed by the mussel-inspired coating of gelatin-dopamine conjugate under H₂O₂-mediated oxidation. The MC3T3-E1 cells cultured on nanofibers exhibit elongated morphology and increased proliferation compared with those on membranes. The differences in global gene expression profiles are determined by RNA-seq, in which 905 differentially expressed genes (DEGs) are identified. Significantly, the DEGs related to cytoskeleton, promotion of cell cycle progression, cell adhesion, and cell proliferation, are higher expressed in the cells on nanofibers, while the DEGs involved in cell-cycle arrest and osteoblast mineralization are up-regulated in the cells on membranes. This study elucidates the roles of nanofiber structure in affecting gene expression of laden cells at the whole transcriptome level, and it will lay the foundation for understanding nanofiber-guided cell behaviors.

Injectable spontaneous hydrogen-releasing hydrogel for long-lasting alleviation of osteoarthritis

Excessive production of reactive oxygen species (ROS) amplifies pro-inflammatory pathways and exacerbates immune responses, and is a key factor in the progression of osteoarthritis (OA). Therapeutic hydrogen gas (H₂) with antioxidative and anti-inflammatory effects, has a potential for OA alleviation, but the targeted delivery and sustained release of H₂ are still challenging. Herein, we develop an injectable calcium boride nanosheets (CBN) loaded hydrogel platform (CBN@GelDA hydrogel) as a high-payload and sustainable H₂ precursor for OA treatment. The CBN@GelDA hydrogel could maintain constant physiological pH conditions which further promotes more H₂ release than the CBN alone and lasts more than one week. The biocompatibility of this hydrogel with macrophages and chondrocytes is effectively enhanced. The experiments show that the CBN@GelDA hydrogel holds the ROS scavenging ability, reducing the expression of related inflammatory cytokines, lessening M1 macrophages but stimulating M2 phenotype, and thereby decreasing chondrocyte apoptosis, which facilitates to breaking of the vicious circle of OA progression. Furthermore, a single-time injection of the CBN@GelDA hydrogel markedly reduces joint destruction in OA rats. From what has been discussed above, this injectable spontaneous H₂-releasing hydrogel is promising for OA treatment. STATEMENT OF SIGNIFICANCE: Oxidative stress and inflammation play the key role in the occurrence and development of osteoarthritis (OA). The system of a hydrogel loaded with H₂ precursor calcium boride nanosheet (CBN), which is the first to use as an H₂ precursor, integrates superior injectable and biocompatible of hydrogel and the selection of antioxidant properties of H₂. This system can improve H₂ release behavior and achieve a single injection into the articular cavity to alleviate the progression of OA in rats. This study of the combination of a convenient long-acting injectable hydrogel and a safe therapeutic gas is of great value for improving the quality of life of clinical patients.

Preparation and characterization of mussel-inspired hydrogels based on methacrylated catechol-chitosan and dopamine methacrylamide

A novel mussel-inspired adhesive hydrogel with enhanced adhesion based on methacrylated catechol-chitosan (MCCS) and dopamine methacrylate (DMA) was prepared via photopolymerization. The structure and morphology of the MCCS/DMA adhesive hydrogel were investigated by using FTIR, NMR, XRD, TG, and SEM. The rheological and texture properties, swelling and degradation characteristics, as well as the adhesion mechanism of the hydrogels were also examined. These results revealed that the MCCS/DMA hydrogels have a dense double cross-linking network structure with porous internal microstructures, and exhibited controllable swelling and degradation properties, good thermostability, and stable rheological characteristics. Furthermore, the adhesive mechanism of MCCS/DMA hydrogel has been confirmed by the FTIR and 2D correlation FTIR spectroscopy. Additionally, the results of in vitro cytotoxicity assessment indicated that the resulting hydrogels have good cytocompatibility. Overall, the MCCS/DMA adhesive hydrogel may have potential applications in medical bioadhesives.

Development of mussel mimetic gelatin based adhesive hydrogel for wet surfaces with self-healing and reversible properties

Gelatin, being a naturally derived biomacromolecule shows good biocompatibility and biodegradability and hence turn out to be a potential biomaterial in synthesizing adhesive hydrogel. However, to achieve significant adhesive strength under wet condition and good mechanical properties, gelatin is functionalised with dopamine and acrylic acid. Here, inspired from nature, we have developed a gelatin based adhesive hydrogel for wet surfaces by incorporating dopamine into gelatin-poly(acrylic acid) chain. The synthesized hydrogel demonstrate good mechanical strength, high stretchability, reversibility, self-healing and dynamic adhesive behaviour along with long term reusability. The adhesive strength of the synthesized hydrogel to tissue surface was found to be 6.5 KPa when applied under submerged condition. Moreover, the swelling behaviour of the hydrogel reveals that hydrogel have limited swellability thereby retaining adhesive property under fully swollen state. Haemolysis results reveals the biocompatible nature of the hydrogel. Thus this hydrogel emerge to be a promising bioadhesive for application in various fields mostly in biomedical devices.

Antibacterial Collagen-Based Nanocomposite Dressings for Promoting Infected Wound Healing

Pathogenic bacterial infection is the most frequent wound complication, which has become a major clinical and healthcare challenge in wound management worldwide, leading to impaired healing processes, the risk of amputation, and even death. Here, collagen-based nanocomposite dressings (APZC) with broad-spectrum antibacterial activity are developed to promote the infected full-thickness wound healing. Short rod-like shaped ZnO NPs are synthesized and then coated with polydopamine (PDA) to obtain PDA coated ZnO NPs (PDA@ZnO NPs). Afterward, PDA@ZnO NPs are conjugated on the backbone of a collagen chain, and the obtained collagen-PDA@ZnO NPs conjugate is crosslinked by dialdehyde sodium alginate to fabricate APZC dressings. PDA@ZnO NPs show well dispersibility and are uniformly incorporated into the collagen matrix. APZC dressings have interconnected microporous structure and great physicochemical properties, besides good blood coagulation performance and well cytocompatibility. APZC dressings demonstrate long-lasting and excellently broad-spectrum antimicrobial activity, which can relieve the inflammatory reaction by killing pathogenic bacteria and induce the generation of blood vessels and the orderly deposition of collagen in the wound site, thus promoting infected full-thickness wound healing without obvious scar formation. Overall, the functionalized collagen-based nanocomposite dressings have great potential in the clinical treatment against bacteria-associated wound infection.

An Instant Underwater Tissue Adhesive Composed of Catechin-Chondroitin Sulfate and Cholesterol-Polyethyleneimine

Due to the safety issue and poor underwater adhesion of current commercially available bioadhesives, they are hard to apply to in vivo physiological environments and more diverse medical use conditions. In this study, a novel and facile bioadhesive for underwater medical applications are designed based on the coacervation of electrostatic interactions and hydrophobic interactions, with the introduction of catechin as a provider of catechol moieties for adhesion to surrounding tissues. The orange-colored bio-adhesive, named PcC, is generated within seconds by mixing catechin-modified chondroitin sulfate and cholesterol chloroformate-modified polyethyleneimine with agitation. In vitro mechanical measurements prove that this novel PcC bio-adhesive is superior in underwater adhesion performance when applied to cartilage. Animal experiments in a rat mastectomy model and rat cartilage graft implantation model demonstrate its potential for diverse medical purposes, such as closing surgical incisions, reducing the formation of seroma, and tissue adhesive applied in orthopedic or cartilage surgery.

High Performance Marine and Terrestrial Bioadhesives and the Biomedical Applications They Have Inspired

This study has reviewed the naturally occurring bioadhesives produced in marine and freshwater aqueous environments and in the mucinous exudates of some terrestrial animals which have remarkable properties providing adhesion under difficult environmental conditions. These bioadhesives have inspired the development of medical bioadhesives with impressive properties that provide an effective alternative to suturing surgical wounds improving closure and healing of wounds in technically demanding tissues such as the heart, lung and soft tissues like the brain and intestinal mucosa. The Gecko has developed a dry-adhesive system of exceptional performance and has inspired the development of new generation re-usable tapes applicable to many medical procedures. The silk of spider webs has been equally inspiring to structural engineers and materials scientists and has revealed innovative properties which have led to new generation technologies in photonics, phononics and micro-electronics in the development of wearable biosensors. Man made products designed to emulate the performance of these natural bioadhesive molecules are improving wound closure and healing of problematic lesions such as diabetic foot ulcers which are notoriously painful and have also found application in many other areas in biomedicine. Armed with information on the mechanistic properties of these impressive biomolecules major advances are expected in biomedicine, micro-electronics, photonics, materials science, artificial intelligence and robotics technology.

Expanding the chemical repertoire of protein-based polymers for drug-delivery applications

Expanding the chemical repertoire of natural and artificial protein-based polymers (PBPs) can enable the production of sequence-defined, yet chemically diverse, biopolymers with customized or new properties that cannot be accessed in PBPs composed of only natural amino acids. Various approaches can enable the expansion of the chemical repertoire of PBPs, including chemical and enzymatic treatments or the incorporation of unnatural amino acids. These techniques are employed to install a wide variety of chemical groups-such as bio-orthogonally reactive, cross-linkable, post-translation modifications, and environmentally responsive groups-which, in turn, can facilitate the design of customized PBP-based drug-delivery systems with modified, fine-tuned, or entirely new properties and functions. Here, we detail the existing and emerging technologies for expanding the chemical repertoire of PBPs and review several chemical groups that either demonstrate or are anticipated to show potential in the design of PBP-based drug delivery systems. Finally, we provide our perspective on the remaining challenges and future directions in this field.

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.

Sprayable Hydrogel for Instant Sealing of Vascular Anastomosis

Bleeding-related complications following vascular surgeries occur in up to half of the patients-500 000 cases annually in the United States alone. This results in additional procedures, increased mortality rate, and prolonged hospitalization, posing a burden on the healthcare system. Commercially available materials rely, in large, on forming covalent bonds between the tissue and the biomaterial to achieve adhesion. Here, it is shown that a biomaterial based on oxidized alginate and oxidized dextran together with polyamidoamine (PAMAM) dendrimer amine provides simultaneous electrostatic and covalent interactions between the biomaterial and the tissue, maximizing adhesion. This study finds that the material withstands supraphysiological pressures (≈300 mmHg) and prevents bleeding in a rabbit aortic puncture model and in a pig carotid bilateral poly(tetrafluoroethylene) graft model-achieving superior performance to commercially available materials such as Tisseel and BioGlue. Material biocompatibility is validated in comprehensive in vitro and in vivo studies in accordance with the US Food and Drug Administration (FDA) guidelines, including in vitro neutral red uptake test, subcutaneous implantation in rabbits, ames genotoxicity, and guinea pig maximization test. This material has the potential to provide with adequate seal and reduced complications following complex vascular surgeries, including hard-to-seal tissue-graft interfaces.

Design, synthesis, and characterization of a novel dual cross-linked gelatin-based bioadhesive for hard and soft tissues adhesion capability

Many surgical treatments require a suitable tissue adhesive that maintains its performance in wet conditions and can be applied simultaneously for hard and soft tissues. In the present study, a dual cross-linked tissue adhesive was synthesized by mixing the gelatin methacryloyl (Gel-MA) and gelatin-dopamine conjugate (Gel-Dopa). The setting reaction was based on a photopolymerization process in the presence of a combination of riboflavin and triethanolamine and a chemical cross-linking process attributed to the genipin as a natural cross-linker. Modified gelatin macromolecules were characterized and the best wavelength for free radical generation in the presence of riboflavin was obtained. Tissue adhesives were prepared with 30% hydrogels of Gel-MA and Gel-Dopa with different ratios in distilled water. The gelation occurred in a short time after light irradiation. The chemical, mechanical, physical, and cytotoxicity properties of the tissue adhesives were evaluated. The results showed that despite photopolymerization, chemical crosslinking with genipin played a more critical role in the setting process. Water uptake, degradation behavior, cytotoxicity, and adhesion properties of the adhesives were correlated with the ratio of the components. The SEM images showed a porous structure that could ensure the entry of cells and nutrients into the surgical area. While acceptable properties in most experiments were observed, all features were improved as the Gel-Dopa ratio increased. Also, the obtained hydrogels revealed excellent adhesive properties, particularly with bone even after wet incubation, and it was attributed to the amount of gelatin-dopamine conjugate. From the obtained results, it was concluded that a dual adhesive hydrogel based on gelatin macromolecules could be a good candidate as a tissue adhesive in wet condition.

Injectable Adhesive Hydrogels for Soft tissue Reconstruction: A Materials Chemistry Perspective

Injectable bioadhesives offer several advantages over conventional staples and sutures in surgery to seal and close incisions or wounds. Despite the growing research in recent years few injectable bioadhesives are available for clinical use. This review summarizes the key chemical features that enable the development and improvements in the use of polymeric injectable hydrogels as bioadhesives or sealants, their design requirements, the gelation mechanism, synthesis routes, and the role of adhesion mechanisms and strategies in different biomedical applications. It is envisaged that developing a deep understanding of the underlying materials chemistry principles will enable researchers to effectively translate bioadhesive technologies into clinically-relevant products.

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.

Force-reversible chemical reaction at ambient temperature for designing toughened dynamic covalent polymer networks

Force-reversible C-N bonds, resulting from the click chemistry reaction between triazolinedione (TAD) and indole derivatives, offer exciting opportunities for molecular-level engineering to design materials that respond to mechanical loads. Here, we displayed that TAD-indole adducts, acting as crosslink points in dry-state covalently crosslinked polymers, enable materials to display reversible stress-responsiveness in real time already at ambient temperature. Whereas the exergonic TAD-indole reaction results in the formation of bench-stable adducts, they were shown to dissociate at ambient temperature when embedded in a polymer network and subjected to a stretching force to recover the original products. Moreover, the nascent TAD moiety can spontaneously and immediately be recombined after dissociation with an indole reaction partners at ambient temperature, thus allowing for the adjustment of the polymer segment conformation and the maintenance of the network integrity by force-reversible behaviors. Overall, our strategy represents a general method to create toughened covalently crosslinked polymer materials with simultaneous enhancement of mechanical strength and ductility, which is quite challenging to achieve by conventional chemical methods.

Weak force-activated covalent bonds as crosslink points can increase mechanical strength and ductility in polymers but the bonds, once broken, cannot be reformed in real time under ambient conditions leading to irreversible damage. Here, the authors demonstrate that triazolinedione (TAD)-indole adducts acting as crosslink points enable materials to display already at ambient temperature reversible stress-responsiveness in real time.

Metal Ion-Directed Functional Metal-Phenolic Materials

Metal ions are ubiquitous in nature and play significant roles in assembling functional materials in fields spanning chemistry, biology, and materials science. Metal-phenolic materials are assembled from phenolic components in the presence of metal ions through the formation of metal-organic complexes. Alkali, alkali-earth, transition, and noble metal ions as well as metalloids interacting with phenolic building blocks have been widely exploited to generate diverse hybrid materials. Despite extensive studies on the synthesis of metal-phenolic materials, a comprehensive summary of how metal ions guide the assembly of phenolic compounds is lacking. A fundamental understanding of the roles of metal ions in metal-phenolic materials engineering will facilitate the assembly of materials with specific and functional properties. In this review, we focus on the diversity and function of metal ions in metal-phenolic material engineering and emerging applications. Specifically, we discuss the range of underlying interactions, including (i) cation-π, (ii) coordination, (iii) redox, and (iv) dynamic covalent interactions, and highlight the wide range of material properties resulting from these interactions. Applications (e.g., biological, catalytic, and environmental) and perspectives of metal-phenolic materials are also highlighted.

Rapid fabrication of bionic pyrogallol-based self-adhesive hydrogel with mechanically tunable, self-healing, antibacterial, wound healing, and hemostatic properties

Hydrogels are functional materials that are similar to human skin and have received much attention in recent years for biomedical applications. However, the preparation of nontoxic, highly adhesive, and antimicrobial hydrogels in an efficient way remains a great challenge. Inspired by adhesive mussel foot proteins (mfps) which consist of abundant catecholic amino acids and lysine (Lys) residues, gallic acid-modified ε-poly-L-lysine (EPL/GA) was synthesized, and an active functional monomer (AA-EPL/GA) was then created through a reaction with acrylic acid (AA). The polymerization of AA-EPL/GA occurred rapidly (30-160 s) under blue light (λ = 405 nm) irradiation to produce a biomimetic PAA-EPL/GA hydrogel under mild conditions. The biomimetic pyrogallol-Lys distribution endowed the PAA-EPL/GA hydrogels with superior adhesion in humid environments (with an adhesive strength of 50.02 kPa toward wet porcine skin) and tunable mechanical and self-healing properties. Additionally, the PAA-EPL/GA hydrogels exhibited outstanding antibacterial ability due to the inherent characteristics of GA and EPL. In a mouse model, PAA-EPL/GA adhered firmly around the wound tissues. Photographs of the wound and the histological results demonstrated the ability of the hydrogel to promote wound healing, control wound infection, and suppress scar formation. Moreover, the hydrogel had a good hemostatic effect on liver bleeding. Our results highlighted the promising application potential of GA-based hydrogels, which were easily, harmlessly, and efficiently fabricated by blue light irradiation.

Shape-Recoverable Hyaluronic Acid-Waterborne Polyurethane Hybrid Cryogel Accelerates Hemostasis and Wound Healing

Wound dressings that promote quick hemostasis and are highly efficient in healing wounds are urgently needed to meet the increase in clinical demands worldwide. Herein, a dihydrazide-modified waterborne biodegradable polyurethane emulsion (PU-ADH) and oxidized hyaluronic acid (OHA) were autonomously cross-linked to form a hybrid hyaluronic acid-polyurethane (HA-PU) cryogel by hydrazone bonding at -20 °C. Through its specific macroporous structure (which is approximately 220 μm) constructed by aggregated PU-ADH particles and long-chain OHA, a dried cryogel can have a dramatically compressed volume (1/7 of its original volume) with stable fixation, and it can swell rapidly by absorbing water or blood to approximately 22 and 16 times its dried weight, respectively, in a few minutes. This instantaneous shape-recovering ability favors fast hemostasis in minimally invasive surgery. Moreover, this cryogel is superior to gauze, has excellent biocompatibility, and quickly coagulates blood (in approximately 2 min) by activating the endogenous coagulation system. Comparably, an injectable HA-PU hydrogel with the same components as the HA-PU cryogel was prepared at room temperature, and it exhibited good self-healing properties. An in vivo evaluation of a rat liver hemostasis model and rat skin defect model revealed that the cryogel in fast hemostasis has great potential and superior wound-healing abilities, decreases immune inflammation, and promotes the regeneration of angiogenesis and hair follicles. Consequently, this work proposes a versatile method for constructing biodegradable hybrid cryogels via autonomous cross-linking between synthesized polymer emulsions and natural polymers. The hybrid cryogels demonstrated great potential for applications as high-performance wound dressings.