Evaluation of photo-crosslinked fibrinogen as a rapid and strong tissue adhesive

In situ light-activated materials for skin wound healing and repair: A narrative review

Dermal wounds are a major global health burden made worse by common comorbidities such as diabetes and infection. Appropriate wound closure relies on a highly coordinated series of cellular events, ultimately bridging tissue gaps and regenerating normal physiological structures. Wound dressings are an important component of wound care management, providing a barrier against external insults while preserving the active reparative processes underway within the wound bed. The development of wound dressings with biomaterial constituents has become an attractive design strategy due to the varied functions intrinsic in biological polymers, such as cell instructiveness, growth factor binding, antimicrobial properties, and tissue integration. Using photosensitive agents to generate crosslinked or photopolymerized dressings in situ provides an opportunity to develop dressings rapidly within the wound bed, facilitating robust adhesion to the wound bed for greater barrier protection and adaptation to irregular wound shapes. Despite the popularity of this fabrication approach, relatively few experimental wound dressings have undergone preclinical translation into animal models, limiting the overall integrity of assessing their potential as effective wound dressings. Here, we provide an up-to-date narrative review of reported photoinitiator- and wavelength-guided design strategies for in situ light activation of biomaterial dressings that have been evaluated in preclinical wound healing models.

Photocurable extracellular matrix sealant for cessation of venous hemorrhage

Hemorrhage is the second leading cause of death in patients under 46 years of age in the United States. Cessation of hemorrhage prevents hemorrhagic shock and tissue hypoxia. Controlling the bleed via direct pressure or tourniquet is often the first line of defense, but long-term care requires staples, hemostatic agents, or sealants that seal the vessel and restore blood flow. Here, we compare a new photocurable extracellular matrix sealant (pcECM) with low, medium, and high crosslink density formulations to a commercially available fibrin-based sealant, TISSEEL®. pcECM has potential uses in surgical and remote settings due to room temperature storage conditions and fast preparation time. Here, we determine if pcECM sealant can stop venous hemorrhage in a murine model, adhere to the wound site in vivo throughout the wound-healing process, and has the mechanical properties necessary for stopping hemorrhage. Adjusting pcECM crosslinking density significantly affected viscosity, swelling, burst strength, tensile strength, and elasticity of the sealant. 3-Dimensional ultrasound volume segmentations showed pcECM degrades to 17 ± 8% of its initial implant volume by day 28. Initially, local hemodynamic changes were observed, but returned close to baseline levels by day 28. Acute inflammation was observed near the puncture site in pcECM implanted mice, and we observed inflammatory markers at the 14-day explant for both sealants. pcECM and fibrin sealant successfully sealed the vessel in all cases, and consistently degraded over 14-28 days. pcECM is a durable sealant with tunable mechanical properties and possible uses in hemorrhage control and other surgical procedures.

Oral mucositis on a chip: modeling induction by chemo- and radiation treatments and recovery

Oral mucositis (OM) is a debilitating complication affecting roughly 70% of head and neck cancer patients receiving chemotherapy and/or radiation treatment. No broadly effective preventative treatment for OM exists. Therefore, anin vitromodel of cancer treatment-induced OM would aid studies into possible origins of the pathology and future drug targets to ameliorate it. In this study, we present a microfluidic oral mucosa triculture tissue construct consisting of a keratinocyte layer attached to a subepithelial fibroblast and endothelial cell-embedded collagen gel. To address the typically low stability of mucosal constructs in microfluidics, ruthenium-catalyzed photocrosslinking was implemented to strengthen the collagen gel and prevent the invasion of keratinocytes, thus maintaining tissue construct geometry and oral mucosa barrier function for over 18 d of culture. Next, the OM chip was exposed to cisplatin (day 10) and damaging radiation (day 11, ± cisplatin at day 10), mimicking damage from cancer therapy. Damage to and then recovery of the tissue layers and function were observed over days 11-18. Therefore, several important features of OM induction and resolution were modeled in microfluidic culture. The OM model on a chip allows for more sophisticated studies into mechanisms of OM and potential treatments.

Visible-Light-Mediated Modification and Manipulation of Biomacromolecules

Chemically modified biomacromolecules-i.e., proteins, nucleic acids, glycans, and lipids-have become crucial tools in chemical biology. They are extensively used not only to elucidate cellular processes but also in industrial applications, particularly in the context of biopharmaceuticals. In order to enable maximum scope for optimization, it is pivotal to have a diverse array of biomacromolecule modification methods at one's disposal. Chemistry has driven many significant advances in this area, and especially recently, numerous novel visible-light-induced photochemical approaches have emerged. In these reactions, light serves as an external source of energy, enabling access to highly reactive intermediates under exceedingly mild conditions and with exquisite spatiotemporal control. While UV-induced transformations on biomacromolecules date back decades, visible light has the unmistakable advantage of being considerably more biocompatible, and a spectrum of visible-light-driven methods is now available, chiefly for proteins and nucleic acids. This review will discuss modifications of native functional groups (FGs), including functionalization, labeling, and cross-linking techniques as well as the utility of oxidative degradation mediated by photochemically generated reactive oxygen species. Furthermore, transformations at non-native, bioorthogonal FGs on biomacromolecules will be addressed, including photoclick chemistry and DNA-encoded library synthesis as well as methods that allow manipulation of the activity of a biomacromolecule.

Bidirectional differentiation of BMSCs induced by a biomimetic procallus based on a gelatin-reduced graphene oxide reinforced hydrogel for rapid bone regeneration

Developmental engineering strategy needs the biomimetic composites that can integrate the progenitor cells, biomaterial matrices and bioactive signals to mimic the natural bone healing process for faster healing and reconstruction of segmental bone defects. We prepared the gelatin-reduced graphene oxide (GOG) and constructed the composites that mimicked the procallus by combining the GOG with the photo-crosslinked gelatin hydrogel. The biological effects of the GOG-reinforced composites could induce the bi-differentiation of bone marrow stromal cells (BMSCs) for rapid bone repair. The proper ratio of GOG in the composites regulated the composites' mechanical properties to a suitable range for the adhesion and proliferation of BMSCs. Besides, the GOG-mediated bidirectional differentiation of BMSCs, including osteogenesis and angiogenesis, could be activated through Erk1/2 and AKT pathway. The methyl vanillate (MV) delivered by GOG also contributed to the bioactive signals of the biomimetic procallus through priming the osteogenesis of BMSCs. During the repair of the calvarial defect in vivo, the initial hypoxic condition due to GOG in the composites gradually transformed into a well-vasculature robust situation with the bi-differentiation of BMSCs, which mimicked the process of bone healing resulting in the rapid bone regeneration. As an inorganic constituent, GOG reinforced the organic photo-crosslinked gelatin hydrogel to form a double-phase biomimetic procallus, which provided the porous extracellular matrix microenvironment and bioactive signals for the bi-directional differentiation of BMSCs. These show a promised application of the bio-reduced graphene oxide in biomedicine with a developmental engineering strategy.

One-Step Photoactivation of a Dual-Functionalized Bioink as Cell Carrier and Cartilage-Binding Glue for Chondral Regeneration

Cartilage defects can result in pain, disability, and osteoarthritis. Hydrogels providing a chondroregeneration-permissive environment are often mechanically weak and display poor lateral integration into the surrounding cartilage. This study develops a visible-light responsive gelatin ink with enhanced interactions with the native tissue, and potential for intraoperative bioprinting. A dual-functionalized tyramine and methacryloyl gelatin (GelMA-Tyr) is synthesized. Photo-crosslinking of both groups is triggered in a single photoexposure by cell-compatible visible light in presence of tris(2,2'-bipyridyl)dichlororuthenium(II) and sodium persulfate as initiators. Neo-cartilage formation from embedded chondroprogenitor cells is demonstrated in vitro, and the hydrogel is successfully applied as bioink for extrusion-printing. Visible light in situ crosslinking in cartilage defects results in no damage to the surrounding tissue, in contrast to the native chondrocyte death caused by UV light (365-400 nm range), commonly used in biofabrication. Tyramine-binding to proteins in native cartilage leads to a 15-fold increment in the adhesive strength of the bioglue compared to pristine GelMA. Enhanced adhesion is observed also when the ink is extruded as printable filaments into the defect. Visible-light reactive GelMA-Tyr bioinks can act as orthobiologic carriers for in situ cartilage repair, providing a permissive environment for chondrogenesis, and establishing safe lateral integration into chondral defects.

Advances in Photoreactive Tissue Adhesives Derived from Natural Polymers

To stop blood loss and accelerate wound healing, conventional wound closure techniques such as sutures and staples are currently used in the clinic. These tissue-piercing wound closure techniques have several disadvantages such as the potential for causing inflammation, infections, and scar formation. Surgical sealants and tissue adhesives can address some of the disadvantages of current sutures and staples. An ideal tissue adhesive will demonstrate strong interfacial adhesion and cohesive strength to wet tissue surfaces. Most reported studies rely on the liquid-to-solid transition of organic molecules by taking advantage of polymerization and crosslinking reactions for improving the cohesive strength of the adhesives. Crosslinking reactions triggered using light are commonly used for increasing tissue adhesive strength since the reactions can be controlled spatially and temporally, providing the on-demand curing of the adhesives with minimum misplacements. In this review, we describe the recent advances in the field of naturally derived tissue adhesives and sealants in which the adhesive and cohesive strengths are modulated using photochemical reactions.

Recent Advances in Hemostasis at the Nanoscale

Rapid and effective hemostatic materials have received wide attention not only in the battlefield but also in hospitals and clinics. Traditional hemostasis relies on materials with little designability which has many limitations. Nanohemostasis has been proposed since the use of peptides in hemostasis. Nanomaterials exhibit excellent adhesion, versatility, and designability compared to traditional materials, laying a good foundation for future hemostatic materials. This review first summarizes current hemostatic methods and materials, and then introduces several cutting-edge designs and applications of nanohemostatic materials such as polypeptide assembly, electrospinning of cyanoacrylate, and nanochitosan. Particularly, their advantages and working mechanisms are introduced. Finally, the challenges and prospects of nanohemostasis are discussed.

Recent advances in 3D printing: vascular network for tissue and organ regeneration

Over the past years, the fabrication of adequate vascular networks has remained the main challenge in engineering tissues due to technical difficulties, while the ultimate objective of tissue engineering is to create fully functional and sustainable organs and tissues to transplant in the human body. There have been a number of studies performed to overcome this limitation, and as a result, 3D printing has become an emerging technique to serve in a variety of applications in constructing vascular networks within tissues and organs. 3D printing incorporated technical approaches allow researchers to fabricate complex and systematic architecture of vascular networks and offer various selections for fabrication materials and printing techniques. In this review, we will discuss materials and strategies for 3D printed vascular networks as well as specific applications for certain vascularized tissue and organ regeneration. We will also address the current limitations of vascular tissue engineering and make suggestions for future directions research may take.

Facile and Controllable Fabrication of Protein-Only Nanoparticles through Photo-Induced Crosslinking of Albumin and Their Application as DOX Carriers

Protein-based nanoparticles, as an alternative to conventional polymer-based nanoparticles, offer great advantages in biomedical applications owing to their functional and biocompatible characteristics. However, the route of fabrication towards protein-based nanoparticles faces substantial challenges, including limitations in size control and unavoidable usage of toxic crosslinkers or organic solvents, which may raise safety concerns related to products and their degradation components. In the present study, a photo-induced crosslinking approach was developed to prepare stable, size-controlled protein-only nanoparticles. The facile one-step reaction irradiated by visible light enables the formation of monodispersed bovine serum albumin nanoparticles (BSA NPs) within several minutes through a tyrosine photo-redox reaction, requiring no cross-linking agents. The size of the BSA NPs could be precisely manipulated (from 20 to 100 nm) by controlling the duration time of illumination. The resultant BSA NPs exhibited spherical morphology, and the α-helix structure in BSA was preserved. Further study demonstrated that the 35 nm doxorubicin (DOX)-loaded BSA NPs achieved a drug loading content of 6.3%, encapsulation efficiency of 70.7%, and a controlled release profile with responsivity to both pH and reducing conditions. Importantly, the in vitro drug delivery experiment demonstrated efficient cellular internalizations of the DOX-loaded BSA NPs and inhibitory activities on MCF-7 and HeLa cells. This method shows the promise of being a platform for the green synthesis of protein-only nanoparticles for biomedical applications.

Matrix crosslinking enhances macrophage adhesion, migration, and inflammatory activation

Macrophages are versatile cells of the innate immune system that can adopt a variety of functional phenotypes depending on signals in their environment. In previous work, we found that culture of macrophages on fibrin, the provisional extracellular matrix protein, inhibits their inflammatory activation when compared to cells cultured on polystyrene surfaces. Here, we sought to investigate the role of matrix stiffness in the regulation of macrophage activity by manipulating the mechanical properties of fibrin. We utilize a photo-initiated crosslinking method to introduce dityrosine crosslinks to a fibrin gel and confirm an increase in gel stiffness through active microrheology. We observe that matrix crosslinking elicits distinct changes in macrophage morphology, integrin expression, migration, and inflammatory activation. Macrophages cultured on a stiffer substrate exhibit greater cell spreading and expression of αM integrin. Furthermore, macrophages cultured on crosslinked fibrin exhibit increased motility. Finally, culture of macrophages on photo-crosslinked fibrin enhances their inflammatory activation compared to unmodified fibrin, suggesting that matrix crosslinking regulates the functional activation of macrophages. These findings provide insight into how the physical properties of the extracellular matrix might control macrophage behavior during inflammation and wound healing.

Elastic sealants for surgical applications

Sealants have emerged as promising candidates for replacing sutures and staples to prevent air and liquid leakages during and after the surgeries. Their physical properties and adhesion strength to seal the wound area without limiting the tissue movement and function are key factors in their successful implementation in clinical practice. In this contribution, the advances in the development of elastic sealants formed from synthetic and natural materials are critically reviewed and their shortcomings are pointed out. In addition, we highlight the applications in which elasticity of the sealant is critical and outline the limitations of the currently available sealants. This review will provide insights for the development of novel bioadhesives with advanced functionality for surgical applications.

Fibrin-based biomaterials: modulation of macroscopic properties through rational design at the molecular level

Fibrinogen is one of the primary components of the coagulation cascade and rapidly forms an insoluble matrix following tissue injury. In addition to its important role in hemostasis, fibrin acts as a scaffold for tissue repair and provides important cues for directing cell phenotype following injury. Because of these properties and the ease of polymerization of the material, fibrin has been widely utilized as a biomaterial for over a century. Modifying the macroscopic properties of fibrin, such as elasticity and porosity, has been somewhat elusive until recently, yet with a molecular-level rational design approach it can now be somewhat easily modified through alterations of molecular interactions key to the protein's polymerization process. This review outlines the biochemistry of fibrin and discusses methods for modification of molecular interactions and their application to fibrin based biomaterials.

Hemostatic strategies for traumatic and surgical bleeding

Wide interest in new hemostatic approaches has stemmed from unmet needs in the hospital and on the battlefield. Many current commercial hemostatic agents fail to fulfill the design requirements of safety, efficacy, cost, and storage. Academic focus has led to the improvement of existing strategies as well as new developments. This review will identify and discuss the three major classes of hemostatic approaches: biologically derived materials, synthetically derived materials, and intravenously administered hemostatic agents. The general class is first discussed, then specific approaches discussed in detail, including the hemostatic mechanisms and the advancement of the method. As hemostatic strategies evolve and synthetic-biologic interactions are more fully understood, current clinical methodologies will be replaced.

Ruthenium-catalyzed photo cross-linking of fibrin-based engineered tissue

Most cross-linking methods utilize chemistry or physical processes that are detrimental to cells and tissue development. Those that are not as harmful often do not provide a level of strength that ultimately meets the required application. The purpose of this work was to investigate the use of a ruthenium-sodium persulfate cross-linking system to form dityrosine in fibrin-based engineered tissue. By utilizing the tyrosine residues inherent to fibrin and cell-deposited proteins, at least 3-fold mechanical strength increases and 10-fold stiffness increases were achieved after cross-linking. This strengthening and stiffening effect was found to increase with culture duration prior to cross-linking such that physiologically relevant properties were obtained. Fibrin was not required for this effect as demonstrated by testing with collagen-based engineered tissue. Cross-linked tissues were implanted subcutaneously and shown to have minimal inflammation after 30 days, similar to non-cross-linked controls. Overall, the method employed is rapid, non-toxic, minimally inflammatory, and is capable of increasing strength and stiffness of engineered tissues to physiological levels.

Biodegradable and injectable cure-on-demand polyurethane scaffolds for regeneration of articular cartilage

This paper describes the synthesis and characterization of an injectable methacrylate functionalized urethane-based photopolymerizable prepolymer to form biodegradable hydrogels. The tetramethacrylate prepolymer was based on the reaction between two synthesized compounds, diisocyanato poly(ethylene glycol) and monohydroxy dimethacrylate poly(epsilon-caprolactone) triol. The final prepolymer was hydrated with phosphate-buffered saline (pH 7.4) to yield a biocompatible hydrogel containing up to 86% water. The methacrylate functionalized prepolymer was polymerized using blue light (450 nm) with an initiator, camphorquinone and a photosensitizer, N,N-dimethylaminoethyl methacrylate. The polymer was stable in vitro in culture media over the 28 days tested (1.9% mass loss); in the presence of lipase, around 56% mass loss occurred over the 28 days in vitro. Very little degradation occurred in vivo in rats over the same time period. The polymer was well tolerated with very little capsule formation and a moderate host tissue response. Human chondrocytes, seeded onto Cultispher-S beads, were viable in the tetramethacrylate prepolymer and remained viable during and after polymerization. Chondrocyte-bead-polymer constructs were maintained in static and spinner culture for 8 weeks. During this time, cells remained viable, proliferated and migrated from the beads through the polymer towards the edge of the polymer. New extracellular matrix (ECM) was visualized with Masson's trichrome (collagen) and Alcian blue (glycosaminoglycan) staining. Further, the composition of the ECM was typical for articular cartilage with prominent collagen type II and type VI and moderate keratin sulphate, particularly for tissue constructs cultured under dynamic conditions.

Evaluation of in situ curable biodegradable polyurethanes containing zwitterion components

Porous polyurethane networks containing covalently attached zwitterionic compounds dihydroxypolycaprolactone phosphorylcholine and 1,2-dihydroxy-N,N-dimethylamino-propane sulfonate have been prepared and characterised. Three polymers were prepared by reacting methyl 2,6-diisocyanato hexanoate functionalised D: -glucose as prepolymer A with either polycaprolactone triol alone or with addition of 10 mol% zwitterion as prepolymer B. All polymer compositions were mixed with 10 wt% hydrated gelatin beads. The cured polymers with the gelatin beads showed compression strengths that were still suitable for use in articular cartilage repair. The incorporation of zwitterions yielded more hydrophilic polymers that showed increased water absorption and increased porosity. After four months degradation in phosphate buffered saline, the polymers containing zwitterions had approximately 50% mass loss compared with 30% mass loss for that with polycaprolactone triol alone. All polymers were non-toxic in chondrocyte-based assays. Subcutaneous implantation of these polymers into rats confirmed that the polymers degraded slowly. Only a very mild inflammatory response was observed and the polymers were able to support new, well vascularised tissue formation.