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Hydrogel patches with high toughness, stretchability, and adhesive properties are critical to healthcare applications including wound dressings and wearable devices. Gelatin methacryloyl (GelMA) provides a highly biocompatible and accessible hydrogel platform. However, low tissue adhesion and poor mechanical properties of cross-linked GelMA patches ( i.e ., brittleness and low stretchability) have been major obstacles to their application for sealing and repair of wounds. Here, we show that adding dopamine (DA) moieties in larger quantities than those of conjugated counterparts to the GelMA prepolymer solution followed by alkaline DA oxidation could result in robust mechanical and adhesive properties in GelMA-based hydrogels. In this way, cross-linked patches with ∼140% stretchability and ∼19 000 J/m 3 toughness, which correspond to ∼5.7 and ∼3.3× improvement, respectively, compared to that of GelMA controls, were obtained. The DA oxidization in the prepolymer solution was found to play an important role in activating adhesive properties of cross-linked GelMA patches (∼4.0 and ∼6.9× increase in adhesion force under tensile and shear modes, respectively) due to the presence of reactive oxidized quinone species. We further conducted a parametric study on the factors such as UV light parameters, the photoinitiator type ( i.e ., lithium phenyl-2,4,6-trimethylbenzoylphosphinate, LAP, versus 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, Irgacure 2959), and alkaline DA oxidation to tune the cross-linking density and thereby hydrogel compliance for better adhesive properties. The superior adhesion performance of the resulting hydrogel along with in vitro cytocompatibility demonstrated its potential for use in skin-attachable substrates.

Surgical sealants have been used for sealing or reconnecting ruptured tissues but often have low adhesion, inappropriate mechanical strength, cytotoxicity concerns, and poor performance in biological environments. To address these challenges, we engineered a biocompatible and highly elastic hydrogel sealant with tunable adhesion properties by photocrosslinking the recombinant human protein tropoelastin. The subcutaneous implantation of the methacryloyl-substituted tropoelastin (MeTro) sealant in rodents demonstrated low toxicity and controlled degradation. All animals survived surgical procedures with adequate blood circulation by using MeTro in an incisional model of artery sealing in rats, and animals showed normal breathing and lung function in a model of surgically induced rat lung leakage. In vivo experiments in a porcine model demonstrated complete sealing of severely leaking lung tissue in the absence of sutures or staples, with no clinical or sonographic signs of pneumothorax during 14 days of follow-up. The engineered MeTro sealant has high potential for clinical applications because of superior adhesion and mechanical properties compared to commercially available sealants, as well as opportunity for further optimization of the degradation rate to fit desired surgical applications on different tissues., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

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.

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 and 20 %, and causes debilitating morbidity. Therefore, there is a critical need for a simple and effective method to seal and heal ECFs. Injectable hydrogels with combined properties of robust mechanical properties and cell infiltration/proliferation have the potential to block and heal ECFs. 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 ECFs. 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 ECFs. This research manuscript presents a groundbreaking INAH for treating ECFs. The INAH, composed of a synthetic nanosilicate and gelatin-dopamine conjugate, offers versatile implications in tissue regeneration and localized drug delivery. Acting as a scaffold, the shear-thinning hydrogel enables easy injection, forming a stable structure that supports tissue regeneration and integrates with surrounding tissues. By incorporating bioactive cues, it guides cell behavior and promotes functional tissue regeneration. The INAH also demonstrates potential for localized drug delivery, releasing therapeutic agents over time to enhance efficacy and minimize side effects. This research showcases INAH as a promising solution for ECFs, with applications in tissue engineering and regenerative medicine, marking a significant advancement in the field. [Display omitted] [ABSTRACT FROM AUTHOR]

Adhesive materials have recently drawn intensive attention due to their excellent sealing ability, 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 study, instead of water or organic solvents, a deep eutectic solvent (DES) is used as the medium for the 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 has rarely been 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 is demonstrated. Also, the high stretchability of the ionogel at extreme temperatures (−80 and 80 °C) indicates its widespread applications. Furthermore, the biocompatible ionogel shows 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 packaging industry, marine engineering, medical adhesives, and electronic assembly. [ABSTRACT FROM AUTHOR]

Surgical adhesive biomaterials have emerged as substitutes to sutures and staples in many clinical applications. Nano-enabled materials containing nanoparticles or having a distinct nanotopography have been utilized for generation of a new class of surgical materials with enhanced functionality. In this review, the state of the art in the development of conventional surgical adhesive biomaterials is critically reviewed and their shortcomings are outlined. Recent advancements in generation of nano-enabled surgical materials with their potential future applications are discussed. This review will open new avenues for the innovative development of the next generation of tissue adhesives, hemostats, and sealants with enhanced functionality for various surgical applications. [ABSTRACT FROM AUTHOR]

Abstract Closure of ocular wounds after an accident or surgery is typically performed by suturing, which is associated with numerous potential complications, including suture breakage, inflammation, secondary neovascularization, erosion to the surface and secondary infection, and astigmatism; for example, more than half of post-corneal transplant infections are due to suture related complications. Tissue adhesives provide promising substitutes for sutures in ophthalmic surgery. Ocular adhesives are not only intended to address the shortcomings of sutures, but also designed to be easy to use, and can potentially minimize post-operative complications. Herein, recent progress in the design, synthesis, and application of ocular adhesives, along with their advantages, limitations, and potential are discussed. This review covers two main classes of ocular adhesives: (1) synthetic adhesives based on cyanoacrylates, polyethylene glycol (PEG), and other synthetic polymers, and (2) adhesives based on naturally derived polymers, such as proteins and polysaccharides. In addition, different technologies to cover and protect ocular wounds such as contact bandage lenses, contact lenses coupled with novel technologies, and decellularized corneas are discussed. Continued advances in this area can help improve both patient satisfaction and clinical outcomes. [ABSTRACT FROM AUTHOR]

Purpose: Current denture adhesives often dissolve in the mouth after eating and drinking. It is important for manufacturer to figure out the mechanism of adhesive failure. Objective: Evaluating the effects of changes in oral environment conditions such as pH, temperature and salivation on the adhesion of denture adhesive product Methods: This experimental study was evaluating the effect of different pHs (2,7,10), temperatures (0, 37, 60 °C) and moisture levels (hyposalivation, normal and hypersalivation) on adhesion strength. To determine the adhesion strength, tensile bond and lap shear tests were carried out according to International Standards Organization (ISO 10873) and American Society for Testing and Materials (ASTM F2255). To prepare the sample, 0.2 g of commercial denture adhesive soaked in artificial saliva which made based on Fusayama Meyer formula for 10 minutes. At least ten samples of each three conditions (pH, temperature and moisture level) were tested and the mean and standard deviations were calculated. Results: The results indicated that the environmental conditions had a significant impact on the adhesion force of the material. In particular, the adhesion force showed a reverse relationship with temperature and, while salivation improved the adhesion force. The adhesion strength at 37 °C was approximately 3996 Pa compared to 4302 Pa at 0°C and 3177 Pa at 60 °C. The pH 10 showed significantly less adhesion in comparison to other pHs (p= 0.02 between pH7 and 10, p=0.0005 between pH 2,10). The tensile strength in acidic environment (6096 Pa) was almost twice of the value at pH 7 (3996 Pa). The hyposalivation group showed the least adhesion among all groups (2684 Pa). There was significant difference between hyposalivation, hypersalivation in comparison with the control group (p=0.001 and p=0.002 in order). Conclusion: Among different oral conditions, hyposalivation had the greatest effect on adhesion. Thus, it is expected that the adhesion strength of denture adhesives to be lower in patients with hyposalivation and higher pHs. The denture adhesive showed the highest strength in acidic condition and lowest temperature. [ABSTRACT FROM AUTHOR]