Design of Xylose-Based Semisynthetic Polyurethane Tissue Adhesives with Enhanced Bioactivity Properties

Thermoresponsive On-Demand Adhesion and Detachment of a Polyurethane-Urea Bioadhesive

The development of bioadhesives with strong adhesion and on-demand adhesion-detachment behavior is still critically important and challenging for facilitating painless and damage-free removal in clinical applications. In this work, for the first time, we report the easy fabrication of novel polyurethane-urea (PUU)-based bioadhesives with thermoresponsive on-demand adhesion and detachment behavior. The PUU copolymer was synthesized by a simple copolymerization of low-molecular-weight, hydrophilic, and biocompatible poly(ethylene glycol), glyceryl monolaurate (GML, a special chain extender with a long side hydrophobic alkyl group), and isophorone diisocyanate (IPDI). Here, GML was expected to not only adjust the temperature-dependent adhesion behavior but also act as an internal plasticizer. By simple adjustment of the water content, the adhesion strength of the 15 wt % water-containing PUU film toward porcine skin is as high as 55 kPa with an adhesion energy of 128 J/m2 at 37 °C. The adhesion strength dramatically decreases to only 3 kPa at 10 °C, exhibiting switching efficiency as high as 0.95. Furthermore, the present PUU-based adhesive also shows good on-demand underwater adhesion and detachment with a cell viability close to 100%. We propose that biomaterial research fields, especially novel PUU/polyurethane (PU)-based functional materials and bioadhesives, could benefit from such a novel thermoresponsive copolymer with outstanding mechanical and functional performances and an easy synthesis and scaled-up process as described in this article.

Formation of hen egg white lysozyme derived amyloid-based hydrogels using different gelation agents: A potential tool for drug delivery

Amyloids are highly stable protein fibrillar aggregates that get deposited in various parts of our body and cause detrimental diseases. But in nature, the presence of functional amyloids is also noted in bacteria that help them by forming hyphae, biofilm, protein reservoirs, signalling messengers, etc. Keeping this perspective in mind, the idea behind this research was to develop functional amyloids in the form of hydrogel and analyse its potential in the biomedical sector as a drug-delivery tool. The synthesis and characterisation of three types of amyloid-based hydrogels have been reported in this work. Hen Egg-White Lysozyme (HEWL) protein was chosen as the principal ingredient as it is extensively used as a standard protein for studying amyloidogenesis and has inherent antibacterial properties. Comparative studies of different hydrogel properties exhibited variations in the hydrogels based on compositional differences in them. Finally, a drug release assay was done on the synthesized hydrogels to explore their potential as drug delivery tools.

Bioadhesive Technology Platforms

Bioadhesives have emerged as transformative and versatile tools in healthcare, offering the ability to attach tissues with ease and minimal damage. These materials present numerous opportunities for tissue repair and biomedical device integration, creating a broad landscape of applications that have captivated clinical and scientific interest alike. However, fully unlocking their potential requires multifaceted design strategies involving optimal adhesion, suitable biological interactions, and efficient signal communication. In this Review, we delve into these pivotal aspects of bioadhesive design, highlight the latest advances in their biomedical applications, and identify potential opportunities that lie ahead for bioadhesives as multifunctional technology platforms.

Reversible fluorescent adhesives based on covalent adaptable networks with dynamic AIE crosslinking: in situ visualization of adhesion capability

A new family of reversible fluorescent adhesives based on Diels-Alder covalent adaptable networks with dynamic AIE crosslinks was developed. The accurate intrinsic correlation between the emission behavior, cross-linking state, and adhesion capability can be established, enabling the in situ visualization of adhesion capacity.

A novel bioactive polyurethane with controlled degradation and L-Arg release used as strong adhesive tissue patch for hemostasis and promoting wound healing

Effective strategy of hemostasis and promoting angiogenesis are becoming increasingly urgent in modern medicine due to millions of deaths caused by tissue damage and inflammation. The tissue adhesive has been favored as an optimistic and efficient path to stop bleeding, while, current adhesive presents limitations on wound care or potential degradation safety in clinical practice. Therefore, it is of great clinical significance to construct multifunctional wound adhesive to address the issues. Based on pro-angiogenic property of l-Arginine (L-Arg), in this study, the novel tissue adhesive (G-DLPUs) constructed by L-Arg-based degradable polyurethane (DLPU) and GelMA were prepared for wound care. After systematic characterization, we found that the G-DLPUs were endowed with excellent capability in shape-adaptive adhesion. Moreover, the L-Arg released and the generation of NO during degradation were verified which would enhance wound healing. Following the in vivo biocompatibility was verified, the hemostatic effect of the damaged organ was tested using a rat liver hemorrhage model, from which reveals that the G-DLPUs can reduce liver bleeding by nearly 75% and no obvious inflammatory cells observed around the tissue. Moreover, the wound care effect was confirmed in a mouse full-thickness skin defect model, showing that the hydrogel adhesive significantly improves the thickness of newly formed dermis and enhance vascularization (CD31 staining). In summary, the G-DLPUs are promising candidate to act as multifunctional wound care adhesive for both damaged organ and trauma.

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.

Fast Curing Multifunctional Tissue Adhesives of Sericin-Based Polyurethane-Acrylates for Sternal Closure

The use of wire cerclage after sternal closure is the standard method because of its rigidity and strength. Despite this, they have many disadvantages such as tissue trauma, operator-induced failures, and the risk of infection. To avoid complications during sternotomy and promote tissue regeneration, tissue adhesives should be used in post-surgical treatment. Here, we report a highly biocompatible, biomimetic, biodegradable, antibacterial, and UV-curable polyurethane-acrylate (PU-A) tissue adhesive for sternal closure as a supportive to wire cerclage. In the study, PU-As were synthesized with variable biocompatible monomers, such as silk sericin, polyethylene glycol, dopamine, and an aliphatic isocyanate 4,4'-methylenebis(cyclohexyl isocyanate). The highest adhesion strength was found to be 4322 kPa, and the ex vivo compressive test result was determined as 715 kPa. The adhesive was determined to be highly biocompatible (on L-929 cells), biodegradable, and antibacterial (on Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus bacteria). Finally, after opening the sternum of rats, the adhesive was applied to bond the bones and cured with UV for 5 min. According to the results, there was no visible inflammation in the adhesive groups, while some animals had high inflammation in the cyanoacrylate and wire cerclage groups. These results indicate that the adhesive may be suitable for sternal fixation by preventing the disadvantages of the steel wires and promoting tissue healing.

Rational design of biodegradable thermoplastic polyurethanes for tissue repair

As a type of elastomeric polymers, non-degradable polyurethanes (PUs) have a long history of being used in clinics, whereas biodegradable PUs have been developed in recent decades, primarily for tissue repair and regeneration. Biodegradable thermoplastic (linear) PUs are soft and elastic polymeric biomaterials with high mechanical strength, which mimics the mechanical properties of soft and elastic tissues. Therefore, biodegradable thermoplastic polyurethanes are promising scaffolding materials for soft and elastic tissue repair and regeneration. Generally, PUs are synthesized by linking three types of changeable blocks: diisocyanates, diols, and chain extenders. Alternating the combination of these three blocks can finely tailor the physio-chemical properties and generate new functional PUs. These PUs have excellent processing flexibilities and can be fabricated into three-dimensional (3D) constructs using conventional and/or advanced technologies, which is a great advantage compared with cross-linked thermoset elastomers. Additionally, they can be combined with biomolecules to incorporate desired bioactivities to broaden their biomedical applications. In this review, we comprehensively summarized the synthesis, structures, and properties of biodegradable thermoplastic PUs, and introduced their multiple applications in tissue repair and regeneration. A whole picture of their design and applications along with discussions and perspectives of future directions would provide theoretical and technical supports to inspire new PU development and novel applications.

Biodegradable polyaspartamide-g-C18 /DOPA/GLY-NEO nano-adhesives for wound closure/healing with antimicrobial activity

This study was focused on the development of biodegradable nano-adhesives with efficient sealing and antibiotic effects for wound healing. Biodegradable polyaspartamide (PASPAM) was grafted with several functional groups to implement diverse roles-octadecylamine (C₁₈ ) for nano-aggregate formation, dopamine (DOPA) for adhesive function, neomycin (NEO) for inhibition of bacterial infection. Specifically, NEO was conjugated to PASPAM with a pH-sensitive glycine (GLY) linker for targeted delivery on the acidic wound site. About 60% of the drug was ramteleased at pH 6.0, while about 22% was released at pH 7.4, showing the faster drug release pattern of nano-adhesives in the acidic environment. The C₁₈ /DOPA/GLY-NEO-g-PASPAM nano-adhesives showed the bacterial viability higher than 70% at pH 7.4, but about 40% at pH 6.0. The wound breaking strength of the polymer-treated skin was much higher than that of the bare skin. According to the in vivo wound healing test using a mouse model, C₁₈ /DOPA/GLY-NEO-g-PASPAM nano-adhesives showed much faster healing performance than sutures. From those results, C₁₈ /DOPA/GLY-NEO-g-PASPAM nano-adhesives are expected to be utilized as effective adhesives that promote the wound healing with inhibition of bacterial infection.

Lignocellulosic Materials for the Production of Biofuels, Biochemicals and Biomaterials and Applications of Lignocellulose-Based Polyurethanes: A Review

The present review is devoted to the description of the state-of-the-art techniques and procedures concerning treatments and modifications of lignocellulosic materials in order to use them as precursors for biomaterials, biochemicals and biofuels, with particular focus on lignin and lignin-based products. Four different main pretreatment types are outlined, i.e., thermal, mechanical, chemical and biological, with special emphasis on the biological action of fungi and bacteria. Therefore, by selecting a determined type of fungi or bacteria, some of the fractions may remain unaltered, while others may be decomposed. In this sense, the possibilities to obtain different final products are massive, depending on the type of microorganism and the biomass selected. Biofuels, biochemicals and biomaterials derived from lignocellulose are extensively described, covering those obtained from the lignocellulose as a whole, but also from the main biopolymers that comprise its structure, i.e., cellulose, hemicellulose and lignin. In addition, special attention has been paid to the formulation of bio-polyurethanes from lignocellulosic materials, focusing more specifically on their applications in the lubricant, adhesive and cushioning material fields. High-performance alternatives to petroleum-derived products have been reported, such as adhesives that substantially exceed the adhesion performance of those commercially available in different surfaces, lubricating greases with tribological behaviour superior to those in lithium and calcium soap and elastomers with excellent static and dynamic performance.

Photocrosslinkable gelatin/collagen based bioinspired polyurethane-acrylate bone adhesives with biocompatibility and biodegradability

Hard or soft tissue adhesives have been presented as a promising candidate to replace traditional wound closure methods. However, there are mechanical strength problems in biological adhesives and biocompatibility problems in synthetic-based adhesives. At this point, we aimed to remove all these disadvantages and produce a single adhesive that contains all the necessary features and acrylate functionalized UV-curable polyurethane formulations were produced with high crosslink density, high adhesion strength, biocompatibility and injectable property for easy application as potential biomedical adhesives. Aliphatic isophorone diisocyanate (IPDI) was used as the isocyanate source and β-cyclodextrin was used for host-guest relationship with gentamicin by crosslinking. Proteins (gelatin (GEL), collagen (COL)) and PEGs of various molecular weight ranges (P200, P400, P600) were selected as the polyol backbone for polyurethane synthesis due to their multiple biological activities such as biocompatibility, biodegradability, biomimetic property. Several techniques have been used to characterize the structural, thermal, morphological, and various other physicochemical properties of the adhesive formulations. Besides, the possibility of its use as a hard tissue adhesive was investigated by evaluating the tissue adhesion strength in vitro and ex vivo via a universal testing analyzer in tensile mode. Corresponding adhesive formulations were evaluated by in vitro and in vivo techniques for biocompatibility. The best adhesion strength results were obtained as 3821.0 ± 214.9, and 3722.2 ± 486.8 kPa, for IPDI-COL-P200 and IPDI-GEL-P200, respectively. Good antibacterial activity capability toward Escherichia coli Pseudomonas aeruginosa, and Staphylococcus aureus were confirmed using disc diffusion method. Moreover, cell viability assay demonstrated that the formulations have no significant cytotoxicity on the L929 fibroblast cells. Most importantly, we finally performed the in vivo biodegradability and in vivo biocompatibility evaluations of the adhesive formulations on rat model. Considering their excellent cell/tissue viability, fast curable, strong adhesion, high antibacterial character, and injectability, these adhesive formulations have significant potential for tissue engineering applications.

Tailor-made shape memory stents for therapeutic enzymes: A novel approach to enhance enzyme performance

Herein, our suggestion is to immobilize enzymes in-situ on absorbable shape-memory stents instead of injecting therapeutic enzymes into the blood. Chitosan (CHI)-based stents were tailored as novel support and the enzyme-immobilizing ability was elucidated using L-asparaginase (L-ASNase). For developing shape-memory stents, CHI-glycerol (GLY) solution was prepared and further blended with different ratios of polyethylene glycol (PEG), and polyvinyl alcohol (PVA). Afterward, the blends were modified by ionic crosslinking with sodium tripolyphosphate to obtain a shape-memory character. L-ASNase was included in the blends by using in-situ method before ionic crosslinking. The prepared stents, with or without L-ASNase, were comprehensively characterized by using several techniques. Collectively, immobilized L-ASNase exhibited much better performance in immobilization parameters than free one, thanks to its improved stability and reusability. For instance, CHI/GLY/PEG-3@L-ASNase retained about 70% of the initial activity after storage at 30 °C for 2 weeks, whereas the free form lost half of its initial activity. Besides, it retained 73.4% residual activity after 15 consecutive cycles. Most importantly, stent formulations exhibited ~60% activity in the bioreactor system after 4 weeks of incubation. Given the above results, shape-memory stents can be a promising candidate as a new platform for immobilization, especially in the blood circulation system.

Biobased polyurethanes for biomedical applications

Polyurethanes (PUs) are a major family of polymers displaying a wide spectrum of physico-chemical, mechanical and structural properties for a large range of fields. They have shown suitable for biomedical applications and are used in this domain since decades. The current variety of biomass available has extended the diversity of starting materials for the elaboration of new biobased macromolecular architectures, allowing the development of biobased PUs with advanced properties such as controlled biotic and abiotic degradation. In this frame, new tunable biomedical devices have been successfully designed. PU structures with precise tissue biomimicking can be obtained and are adequate for adhesion, proliferation and differentiation of many cell's types. Moreover, new smart shape-memory PUs with adjustable shape-recovery properties have demonstrated promising results for biomedical applications such as wound healing. The fossil-based starting materials substitution for biomedical implants is slowly improving, nonetheless better renewable contents need to be achieved for most PUs to obtain biobased certifications. After a presentation of some PU generalities and an understanding of a biomaterial structure-biocompatibility relationship, recent developments of biobased PUs for non-implantable devices as well as short- and long-term implants are described in detail in this review and compared to more conventional PU structures.

Enzyme Catalyzed Hydrogel as Versatile Bioadhesive for Tissue Wound Hemostasis, Bonding, and Continuous Repair

Developing a versatile bioadhesive which is biocompatible, adhesive, hemostatic, and therapeutic is of great significance to promote wound sealing and healing. Herein, an adhesive (GTT-3 hydrogel) is fabricated by catalysis of tannic acid modified gelatin (Gel-TA) with transglutaminase (TG). The hydrogen bonding, imine linking, and acyl-transfer reaction between GTT-3 hydrogel and tissue enable efficient hydrogel integration and adhesion to tissue instantly, so as to seal the wound and stop bleeding. Moreover, the intrinsic wound healing ability of gelatin and the antibacterial properties of TA provide favorable conditions for wound healing after adhesion. In vitro mechanical property testing and cell experimental results determine the elasticity, adhesion, and biocompatibility of the GTT-3 hydrogel. The wound operation in mouse models and pathological sectioning results indicate that GTT-3 adhesive obviously accelerates hemostasis, wound bonding, and healing. With the special property of instant adhesion and excellent hemostatic and therapeutic repair effects, GTT-3 hydrogel may provide a new option for surgical operation.

High-Strength Hydrogel Attachment through Nanofibrous Reinforcement

The repair of a cartilage lesion with a hydrogel requires a method for long-term fixation of the hydrogel in the defect site. Attachment of a hydrogel to a base that allows for integration with bone can enable long-term fixation of the hydrogel, but current methods of forming bonds to hydrogels have less than a tenth of the shear strength of the osteochondral junction. This communication describes a new method, nanofiber-enhanced sticking (NEST), for bonding a hydrogel to a base with an adhesive shear strength three times larger than the state-of-the-art. An example of NEST is described in which a nanofibrous bacterial cellulose sheet is bonded to a porous base with a hydroxyapatite-forming cement followed by infiltration of the nanofibrous sheet with hydrogel-forming polymeric materials. This approach creates a mineralized nanofiber bond that mimics the structure of the osteochondral junction, in which collagen nanofibers extend from cartilage into a mineralized region that anchors cartilage to bone.

Tissue Adhesives: From Research to Clinical Translation

Sutures, staples, clips and skin closure strips are used as the gold standard to close wounds after an injury. In spite of being the present standard of care, the utilization of these conventional methods is precarious amid complicated and sensitive surgeries such as vascular anastomosis, ocular surgeries, nerve repair, or due to the high-risk components included. Tissue adhesives function as an interface to connect the surfaces of wound edges and prevent them from separation. They are fluid or semi-fluid mixtures that can be easily used to seal any wound of any morphology - uniform or irregular. As such, they provide alternatives to new and novel platforms for wound closure methods. In this review, we offer a background on the improvement of distinctive tissue adhesives focusing on the chemistry of some of these products that have been a commercial success from the clinical application perspective. This review is aimed to provide a guide toward innovation of tissue bioadhesive materials and their associated biomedical applications.

Designing a castor oil-based polyurethane as bioadhesive

Based on the stealth behavior of castor oil and poly(ethylene glycol), we selected a polyurethane system to obtain an ideal surgical adhesive. The polyurethane adhesives with varying concentrations of castor oil were investigated by Fourier transform infrared spectrometer, differential scanning calorimetry, scanning electron microscopy, goniometer, and universal testing machine. Curing results show that a 7-min to 25-min room temperature curing can be achieved, providing one possibility of shortening the surgery time. In vitro biodegradation test demonstrates that a certain proportion of the polyurethane film will be hydrolyzed in a foregone manner after a period of time (7 weeks). The adhesion strengths of these adhesives show a strong bonding between pieces of tissue, which makes them qualified for application in a moist environment.

Amyloid-Based Injectable Hydrogel Derived from Hydrolyzed Hen Egg White Lysozyme

Injectable hydrogels based on synthetic peptides have shown great promise in many biomedical applications. Yet, the high cost generally associated with synthetic peptides hinders the practical use of such peptide-based injectable hydrogel. To overcome this drawback, here, we propose to use the peptides from hydrolyzed low-cost natural protein as an economical and convenient peptide source to prepare an injectable hydrogel. We demonstrate the effectiveness of this alternative strategy using hen egg white lysozyme (HEWL) as an example. We used the peptide fragments from hydrolyzed HEWL as the gelator, and the magnesium ion as the performance enhancer to prepare the injectable hydrogel. We showed that the hydrogel is an amyloid gel as it was formed by a dense network of amyloid fibrils. We also showed that the hydrogel possesses a thixotropic property and displays a low cytotoxicity. The hydrolysis extent of HEWL was found to be a critical factor that influences the performance of the hydrogel. A fluorescence assay based on 8-anilinonaphthalene-1-sulfonic acid was proposed as a mean to precisely and conveniently control the hydrolysis extent of HEWL to enable the best injectability performance. At last, using doxorubicin as a model compound, we explored the potential of this amyloid-based hydrogel as an injectable drug carrier.