Bioinspired Super-Strong Aqueous Synthetic Tissue Adhesives

Injectable Tissue Adhesive Microgel Composite Containing Antifibrotic Drug for Vocal Fold Scarring

Vocal fold (VF) scarring, a complex problem in laryngology, results from injury and inflammation of the layered architecture of the VFs. The resultant voice hoarseness, for which successful therapeutic options are currently limited, affects the patient's quality of life. A promising strategy to reverse this disorder is the use of antifibrotic drugs. The present study proposes a novel microbead-embedded injectable hydrogel that can sustain the release of the anti-fibrotic drug pirfenidone (PFD) for vocal fold scarring. Microbeads were developed using sodium alginate and gelatin, which were further embedded into a biomimetic and tissue adhesive gellan gum (GG) hydrogel. The microbead-embedded hydrogel exhibited improved injectability, viscoelasticity, tissue adhesiveness, degradability, and swelling compared to the hydrogel without beads. Additionally, the bead-embedded hydrogel could sustain the release of the PFD for a week. In vitro studies showed that the drug-loaded hydrogel could reduce the migration and proliferation of fibroblast cells in a dose-dependent manner. In summary, this study demonstrates the potential of a PFD-loaded injectable hydrogel with enhanced viscoelastic and tissue-adhesive properties for vocal fold scarring applications.

Nature-Inspired Gelatin-Based Adhesive Hydrogel: A Rapid and User-Friendly Solution for Hemostatic Applications

Conventional hemostatic agents face challenges in achieving rapid hemostasis and effective tissue repair due to limited hemostatic scenarios, suboptimal efficacy, and inadequate adhesion to wet tissues. Drawing inspiration from nature-sourced materials, a gelatin-based adhesive hydrogel (AOT)  is designed, easily prepared and quick to form, driven by Schiff base and multiple hydrogen bonds for applications in arterial and liver bleeding models. AOT exhibits exceptional adhesion to wet tissues (48.67 ± 0.16 kPa) and displays superior hemostatic properties with reduced blood loss and hemostatic time compared to other hydrogels and conventional hemostatic materials. Moreover, AOT exhibits good biocompatibility and biodegradability. In summary, this easily prepared adhesive hydrogel has the potential to supplant traditional hemostatic agents, offering a novel approach to achieve swift sealing of hemostasis and facilitate wound healing and repair in broader application scenarios, owing to its unique advantages.

Tissue-adhesive, stretchable and compressible physical double-crosslinked microgel-integrated hydrogels for dynamic wound care

Integrated wound care through sequentially promoting hemostasis, sealing, and healing holds great promise in clinical practice. However, it remains challenging for regular bioadhesives to achieve integrated care of dynamic wounds due to the difficulties in adapting to dynamic mechanical and wet wound environments. Herein, we reported a type of dehydrated, physical double crosslinked microgels (DPDMs) which were capable of in situ forming highly stretchable, compressible and tissue-adhesive hydrogels for integrated care of dynamic wounds. The DPDMs were designed by the rational integration of the reversible crosslinks and double crosslinks into micronized gels. The reversible physical crosslinks enabled the DPDMs to integrate together, and the double crosslinked characteristics further strengthen the formed macroscopical networks (DPDM-Gels). We demonstrated that the DPDM-Gels simultaneously possess outstanding tensile (∼940 kJ/m3) and compressive (∼270 kJ/m3) toughness, commercial bioadhesives-comparable tissue-adhesive strength, together with stable performance under hundreds of deformations. In vivo results further revealed that the DPDM-Gels could effectively stop bleeding in various bleeding models, even in an actual dynamic environment, and enable the integrated care of dynamic skin wounds. On the basis of the remarkable mechanical and appropriate adhesive properties, together with impressive integrated care capacities, the DPDM-Gels may provide a new approach for the smart care of dynamic wounds. STATEMENT OF SIGNIFICANCE: Integrated care of dynamic wounds holds great significance in clinical practice. However, the dynamic and wet wound environments pose great challenges for existing hydrogels to achieve it. This work developed robust adhesive hydrogels for integrated care of dynamic wounds by designing dehydrated, physical double crosslinked microgels (DPDMs). The reversible and double crosslinks enabled DPDMs to integrate into macroscopic hydrogels with high mechanical properties, appropriate adhesive strength and stable performance under hundreds of external deformations. Upon application at the injury site, DPDM-Gels efficiently stopped bleeding, even in an actual dynamic environment and showed effectiveness in integrated care of dynamic wounds. With the fascinating properties, DPDMs may become an effective tool for smart wound care.

Self-healing, antioxidant, and antibacterial Bletilla striata polysaccharide-tannic acid dual dynamic crosslinked hydrogels for tissue adhesion and rapid hemostasis

Biomaterials capable of achieving effective sealing and hemostasis at moist wounds are in high demand in the clinical management of acute hemorrhage. Bletilla striata polysaccharide (BSP), a natural polysaccharide renowned for its hemostatic properties, holds promising applications in biomedical fields. In this study, a dual-dynamic-bonds crosslinked hydrogel was synthesized via a facile one-pot method utilizing poly(vinyl alcohol) (PVA)-borax as a matrix system, followed by the incorporation of BSP and tannic acid (TA). Chemical borate ester bonds formed around borax, coupled with multiple physical hydrogen bonds between BSP and other components, enhanced the mechanical properties and rapid self-healing capabilities. The catechol moieties in TA endowed the hydrogel with excellent adhesive strength of 30.2 kPa on the surface of wet tissues and facilitated easy removal without residue. Benefiting from the synergistic effect of TA and the preservation of the intrinsic properties of BSP, the hydrogel exhibited outstanding biocompatibility, antibacterial, and antioxidant properties. Moreover, it effectively halted acute bleeding within 31.3 s, resulting in blood loss of 15.6 % of that of the untreated group. As a superior hemostatic adhesive, the hydrogel in this study is poised to offer a novel solution for addressing future acute hemorrhage, wound healing, and other biomedical applications.

Biocompatible Tough Ionogels with Reversible Supramolecular Adhesion

Cohesive and interfacial adhesion energies are difficult to balance to obtain reversible adhesives with both high mechanical strength and high adhesion strength, although various methods have been extensively investigated. Here, a biocompatible citric acid/L-(-)-carnitine (CAC)-based ionic liquid was developed as a solvent to prepare tough and high adhesion strength ionogels for reversible engineered and biological adhesives. The prepared ionogels exhibited good mechanical properties, including tensile strength (14.4 MPa), Young's modulus (48.1 MPa), toughness (115.2 MJ m-3), and high adhesion strength on the glass substrate (24.4 MPa). Furthermore, the ionogels can form mechanically matched tough adhesion at the interface of wet biological tissues (interfacial toughness about 191 J m-2) and can be detached by saline solution on demand, thus extending potential applications in various clinical scenarios such as wound adhesion and nondestructive transfer of organs.

Bioinspired Injectable Polyurethane Underwater Adhesive with Fast Bonding and Hemostatic Properties

Underwater adhesives with injectable, organic solvent-free, strong, fast adhesion, and hemostatic properties have become an urgent need in biomedical field. Herein, a novel polyurethane underwater adhesive (PUWA) inspired by mussels is developed utilizing the rapid post-cure reaction of isocyanate esterification without organic solvents. The PUWA is created through the injectable two component curing process of component A (biocompatible polyurethane prepolymer) and component B (dopamine modified lysine derivatives: chain extender-LDA and crosslinker-L3DA). The two-component adhesive cures quickly and firmly underwater, with an impressive bonding strength of 40 kPa on pork skin and excellent burst pressure of 394 mmHg. Moreover, the PUWA exhibits robust adhesion strength in hostile environments with acid, alkali and saline solutions. Combined with excellent biocompatibility and hemostatic performance, the PUWA demonstrates effectively sealing wounds and promoting healing. With the ability to bond diverse substrates rapidly and strongly, the PUWA holds significant potential for application in both biomedical and industrial fields.

Synthesis and Analysis of Novel Hyaluronic Acid-Based Dual Photocrosslinkable Tissue Adhesive: An In Vitro Study

Background Tissue adhesives are mainly used for aiding in the attachment of adjacent tissues or to nearby hard tissue surfaces. They promote the natural healing processes of the tissues, especially for less painful closure, simple application, no need for sutures following surgery, and localized drug release. This study aimed to synthesize and assess the properties of hyaluronic acid (HA)-based, dual photocrosslinkable tissue adhesive. Materials and methodology N-hydroxysuccinimide (NHS), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), HA, and polymethylmethacrylate, which served as a photoinitiator, were combined to synthesize a tissue adhesive. The prepared formulation was characterized, and its biocompatibility was assessed. Results Surface morphology, mechanical properties, and biological properties of the HA adhesive were comparable to those of conventional fibrin glue. Scanning electron microscopy (SEM) analysis showed the average size of the molecules, 10-25 mm in diameter, and also showed a smooth and nonporous surface. The specimens experienced maximum compressive stress of 0.06 ± 0.02 MPa, compressive strain of 3.07 ± 2.02, and a compressive displacement at break of 3.04 ± 1.23 mm, with a maximum force of 2.33 ± 0.07 N at break. The cytotoxicity assay results for HA and fibrin glue are almost equal. Conclusion HA-based photocrosslinkable tissue adhesive could be a potential biomaterial in various applications in the field of medicine, especially in soft tissue management.

Silk fibroin hydrogel adhesive enables sealed-tight reconstruction of meniscus tears

Despite orientationally variant tears of the meniscus, suture repair is the current clinical gold treatment. However, inaccessible tears in company with re-tears susceptibility remain unresolved. To extend meniscal repair tools from the perspective of adhesion and regeneration, we design a dual functional biologic-released bioadhesive (S-PIL10) comprised of methacrylated silk fibroin crosslinked with phenylboronic acid-ionic liquid loading with growth factor TGF-β1, which integrates chemo-mechanical restoration with inner meniscal regeneration. Supramolecular interactions of β-sheets and hydrogen bonds richened by phenylboronic acid-ionic liquid (PIL) result in enhanced wet adhesion, swelling resistance, and anti-fatigue capabilities, compared to neat silk fibroin gel. Besides, elimination of reactive oxygen species (ROS) by S-PIL10 further fortifies localized meniscus tear repair by affecting inflammatory microenvironment with dynamic borate ester bonds, and S-PIL10 continuously releases TGF-β1 for cell recruitment and bridging of defect edge. In vivo rabbit models functionally evidence the seamless and dense reconstruction of torn meniscus, verifying that the concept of meniscus adhesive is feasible and providing a promising revolutionary strategy for preclinical research to repair meniscus tears.

Robust aortic media adhesion using hydrophobically modified Alaska pollock gelatin-based adhesive for aortic dissections

Type-A aortic dissection is an acute injury involving the delamination of the aorta at the parts of the aortic media. Aldehyde crosslinker-containing glues have been used to adhere to the media of the dissected aorta before joining an artificial graft. These glues effectively adhere to the aortic media; however, they show low biocompatibility due to the release of aldehyde compounds. In this study, we report innovative adhesives based on hydrophobically modified Alaska pollock gelatin (hm-ApGltn) with different alkyl or cholesteryl (Chol) groups that adhere to the media of the dissected aorta by combining hm-ApGltns with a biocompatible crosslinker, pentaerythritol poly(ethylene glycol) ether tetrasuccinimidyl glutarate. The modification of alkyl or Chol groups contributed to enhanced adhesion strength between porcine aortic media. The adhesion strength increased with increasing modification ratios of alkyl groups from propanoyl to dodecanoyl groups and then decreased at a modification ratio of ~20 mol %. Porcine aortic media adhered using 7.5Chol-ApGltn adhesive showed stretchability even when expanded and shrunk vertically by 25% at least five times. Hm-ApGltn adhesives subcutaneously injected into the backs of mice showed no severe inflammation and were degraded during the implantation period. These results indicated that hm-ApGltn adhesives have potential applications in type-A aortic dissection.

Tunable backbone-degradable robust tissue adhesives via in situ radical ring-opening polymerization

Adhesives with both robust adhesion and tunable degradability are clinically and ecologically vital, but their fabrication remains a formidable challenge. Here we propose an in situ radical ring-opening polymerization (rROP) strategy to design a backbone-degradable robust adhesive (BDRA) in physiological environment. The hydrophobic cyclic ketene acetal and hydrophilic acrylate monomer mixture of the BDRA precursor allows it to effectively wet and penetrate substrates, subsequently forming a deep covalently interpenetrating network with a degradable backbone via redox-initiated in situ rROP. The resulting BDRAs show good adhesion strength on diverse materials and tissues (e.g., wet bone >16 MPa, and porcine skin >150 kPa), higher than that of commercial cyanoacrylate superglue (~4 MPa and 56 kPa). Moreover, the BDRAs have enhanced tunable degradability, mechanical modulus (100 kPa-10 GPa) and setting time (seconds-hours), and have good biocompatibility in vitro and in vivo. This family of BDRAs expands the scope of medical adhesive applications and offers an easy and environmentally friendly approach for engineering.

Silk Fibroin-Based Tough Hydrogels with Strong Underwater Adhesion for Fast Hemostasis and Wound Sealing

Rapid and strong adhesion of hydrogel adhesives is required for instant wound closure and hemostasis. However, in situ hydrogel formation and sufficient adhesion at target tissue sites in biological environments are severely compromised by the presence of blood and body fluids. In this work, an underwater adhesive hydrogel (named SHCa) is fabricated with rapid in situ gelation, enhanced mechanical toughness, and robust underwater adhesion. The SHCa can undergo rapid UV irradiation-induced gelation under water within 5 s and adhere firmly to underwater surfaces for 6 months. The synergistic effects of crystalline β-sheet structures and dynamic energy-dissipating mechanisms enhance the mechanical toughness and cohesion, supporting the balance between adhesion and cohesion in wet environments. Importantly, the SHCa can achieve rapid in situ gelation and robust underwater adhesion at various tissue surfaces in highly dynamic fluid environments, substantially outperforming the commercially available tissue adhesives. The lap shear adhesion strength and wound closure strength of SHCa on blood-covered substrates are 7.24 and 12.68 times higher than those of cyanoacrylate glue, respectively. Its fast hemostasis and wound sealing performance are further demonstrated in in vivo animal models. The proposed hydrogel with strong underwater adhesion provides an effective tool for fast wound closure and hemostasis.