Adhesive and sealant interfaces for general surgery applications

Osteoclasts degrade fibrinogen scaffolds and induce mesenchymal stem/stromal osteogenic differentiation

Fibrinogen (Fg) is a pro-inflammatory protein with pro-healing properties. Previous work showed that fibrinogen 3D scaffolds (Fg-3D) promote bone regeneration, but the cellular players were not identified. Osteoclasts are bone resorbing cells that promote bone remodeling in close crosstalk with osteoblasts. Herein, the capacity of osteoclasts differentiated on Fg-3D to degrade the scaffolds and promote osteoblast differentiation was evaluated in vitro. Fg-3D scaffolds were prepared by freeze-drying and osteoclasts were differentiated from primary human peripheral blood monocytes. Results obtained showed osteoclasts expressing the enzymes cathepsin K and tartrate resistant acid phosphatase colonizing Fg-3D scaffolds. Osteoclasts were able to significantly degrade Fg-3D, reducing the scaffold's area, and increasing D-dimer concentration, a Fg degradation product, in their culture media. Osteoclast conditioned media from the first week of differentiation promoted significantly stronger human primary mesenchymal stem/stromal cell (MSC) osteogenic differentiation, evaluated by alkaline phosphatase activity. Moreover, week 1 osteoclast conditioned media promoted earlier MSC osteogenic differentiation, than chemical osteogenesis inductors. TGF-β1 was found increased in osteoclast conditioned media from week 1, when compared to week 3 of differentiation. Taken together, our results suggest that osteoclasts are able to differentiate and degrade Fg-3D, producing factors like TGF-β1 that promote MSC osteogenic differentiation.

Adhesive Cements That Bond Soft Tissue Ex Vivo

The aim of the present study was to evaluate the soft tissue bond strength of a newly developed, monomeric, biomimetic, tissue adhesive called phosphoserine modified cement (PMC). Two types of PMCs were evaluated using lap shear strength (LSS) testing, on porcine skin: a calcium metasilicate (CS1), and alpha tricalcium phosphate (αTCP) PMC. CS1 PCM bonded strongly to skin, reaching a peak LSS of 84, 132, and 154 KPa after curing for 0.5, 1.5, and 4 h, respectively. Cyanoacrylate and fibrin glues reached an LSS of 207 kPa and 33 kPa, respectively. αTCP PMCs reached a final LSS of ≈110 kPa. In soft tissues, stronger bond strengths were obtained with αTCP PMCs containing large amounts of amino acid (70-90 mol%), in contrast to prior studies in calcified tissues (30-50 mol%). When αTCP particle size was reduced by wet milling, and for CS1 PMCs, the strongest bonding was obtained with mole ratios of 30-50% phosphoserine. While PM-CPCs behave like stiff ceramics after setting, they bond to soft tissues, and warrant further investigation as tissue adhesives, particularly at the interface between hard and soft tissues.

Bioadhesive functional hydrogels: Controlled release of catechol species with antioxidant and antiinflammatory behavior

Chronic wounds are particularly difficult to heal and constitute an important global health care problem. Some key factors that make chronic wounds challenging to heal are attributed to the incessant release of free radicals, which activate the inflammatory system and impair the repair of the wound. Intrinsic characteristics of hydrogels are beneficial for wound healing, but the effective control of free radical levels in the wound and subsequent inflammation is still a challenge. Catechol, the key molecule responsible for the mechanism of adhesion of mussels, has been proven to be an excellent radical scavenger and anti-inflammatory agent. Our approach in this work lies in the preparation of a hybrid system combining the beneficial properties of hydrogels and catechol for its application as a bioactive wound dressing to assist in the treatment of chronic wounds. The hydrogel backbone is obtained through a self-covalent crosslinking between chitosan (Ch) and oxidized hyaluronic acid (HAox) in the presence of a synthetic catechol terpolymer, which is subsequently coordinated to Fe to obtain an interpenetrated polymer network (IPN). The structural analysis, catechol release profiles, in vitro biological behavior and in vivo performance of the IPN are analyzed and compared with the semi-IPN (without Fe) and the Ch/HAox crosslinked hydrogels as controls. Catechol-containing hydrogels present high tissue adhesion strength under wet conditions, support growth, migration and proliferation of hBMSCs, protect cells against oxidative stress damage induce by ROS, and promote down-regulation of the pro-inflammatory cytokine IL-1β. Furthermore, in vivo experiments reveal their biocompatibility and stability, and histological studies indicate normal inflammatory responses and faster vascularization, highlighting the performance of the IPN system. The novel IPN design also allows for the in situ controlled and sustained delivery of catechol. Therefore, the developed IPN is a suitable ECM-mimic platform with high cell affinity and bioactive functionalities that, together with the controlled catechol release, will enhance the tissue regeneration process and has a great potential for its application as wound dressing.

Marine-Inspired Polymers in Medical Adhesion

Medical adhesives that are strong, easy to apply and biocompatible are promising alternatives to sutures and staples in a large variety of surgical and clinical procedures. Despite progress in the development and regulatory approval of adhesives for use in the clinic, adhesion to wet tissue remains challenging. Marine organisms have evolved a diverse set of highly effective wet adhesive approaches that have inspired the design of new medical adhesives. Here we provide an overview of selected marine animals and their chemical and physical adhesion strategies, the state of clinical translation of adhesives inspired by these organisms, and target applications where marine-inspired adhesives can have a significant impact. We will focus on medical adhesive polymers inspired by mussels, sandcastle worms, and cephalopods, emphasize the history of bioinspired medical adhesives from the peer reviewed and patent literature, and explore future directions including overlooked sources of bioinspiration and materials that exploit multiple bioinspired strategies.

Development of hyaluronan-based membranes for the healing of intestinal surgical wounds: a preliminary study

Implantable membranes based on alginate and hyaluronic acid (HA) were manufactured to obtain a rapidly resorbing pliable mesh for the in situ administration of HA to intestinal tissue. Morphological analyses of this interpenetrated matrix pointed out a homogeneous polymeric texture while degradation studies demonstrated that the material is able to dissolve in physiological solutions within few days. Biological studies in vitro showed that the membrane is biocompatible towards human dermal fibroblasts and that liquid extracts from the HA-containing membrane can stimulate wound healing. A preliminary in vivo biocompatibility study on rats showed that the membranes in direct contact with the intestine did not elicit any acute adverse reaction or immune response, while only a mild inflammatory reaction was noticed at the mesenteric or serosal region. Overall, these results appear to support the application of these polysaccharide-based materials for intestinal wound healing.

Fibrin Sealant Derived from Human Plasma as a Scaffold for Bone Grafts Associated with Photobiomodulation Therapy

Fibrin sealants derived from human blood can be used in tissue engineering to assist in the repair of bone defects. The objective of this study was to evaluate the support system formed by a xenograft fibrin sealant associated with photobiomodulation therapy of critical defects in rat calvaria. Thirty-six rats were divided into four groups: BC (n = 8), defect filled with blood clot; FSB (n = 10), filled with fibrin sealant and xenograft; BCPBMT (n = 8), blood clot and photobiomodulation; FSBPBMT (n = 10), fibrin sealant, xenograft, and photobiomodulation. The animals were killed after 14 and 42 days. In the histological and microtomographic analysis, new bone formation was observed in all groups, limited to the defect margins, and without complete wound closure. In the FSB group, bone formation increased between periods (4.3 ± 0.46 to 6.01 ± 0.32), yet with lower volume density when compared to the FSBPBMT (5.6 ± 0.45 to 10.64 ± 0.97) group. It was concluded that the support system formed by the xenograft fibrin sealant associated with the photobiomodulation therapy protocol had a positive effect on the bone repair process.

Controlled living anionic polymerization of cyanoacrylates by frustrated Lewis pair based initiators

A hydrogenated frustrated Lewis pair ([TMPH+][HB(C6F5)3 -]) promotes controlled living ionic polymerization of cyanoacrylates. Controlled growth of various homopolymeric CAs through sequential monomer addition has been achieved, in addition to CA block copolymers with controlled block sequences for the first time in the long history of these materials.

Bioinspired baroplastic glycosaminoglycan sealants for soft tissues

We describe biomimetic adhesives inspired by the marine glues fabricated by the sandcastle worm. The formation of stable polyelectrolyte complexes between poly-L-lysine (PLL) and glycosaminoglycans (GAGs) with different sulfation degree - heparin (HEP), chondroitin sulfate (CS) and hyaluronic acid (HA) - is optimized by zeta-potential titrations. These PLL/GAG complexes are transformed into compact polyelectrolyte complexes (coPECs) with controlled water contents and densities via baroplastic processing. Rotational shear tests demonstrate that coPECs containing sulfated GAGs (HEP or CS) have solid-like properties, whereas HA-based complexes form highly hydrated viscous-like networks. The adhesiveness of the generated coPECs (normalized lap shear strength) is tested in dry and wet states using polystyrene and rabbit skin, respectively. In dry state, the adhesives exhibit lap shear strengths in the order of hundreds of kPa, with coPLL/HEP and coPLL/CS being about 1.5 times stronger than coPLL/HA. In wet state, all coPECs seal rabbit skin and recover over 60% of the elongation capacity of intact skin with coPLL/HA providing the sturdiest adhesion (∼85% elongation recovery). We demonstrate that this is due to the higher water fraction that improves the bonding between the wet specimens, showcasing the potential superior mechanical recovery on injured tissues. STATEMENT OF SIGNIFICANCE: The development of medical sealants with sufficient adhesive strength in the presence of water and moist remains a huge challenge. We present glycosaminoglycans (GAGs) as biomaterials for the assembly of baroplastics with strong adhesive strength to soft tissues at physiological conditions. Baroplastics with tacky properties were generated by a mild assembly process based on polyelectrolyte complexation and compaction. These materials behave as versatile sealants: their adhesiveness can be adjusted to either dry or wet specimens because of the different sulfation degree of GAGs. These sealants were noncytotoxic towards L929 cells and allowed the damaged skin to recover a great deal of its native elasticity: they preserved the J-shaped stress/strain mechanical response that is typical of biological soft tissues.

A PEG-Based Hydrogel for Effective Wound Care Management

It is extremely challenging to achieve strong adhesion in soft tissues while minimizing toxicity, tissue damage, and other side effects caused by wound sealing materials. In this study, flexible synthetic hydrogel sealants were prepared based on polyethylene glycol (PEG) materials. PEG is a synthetic material that is nontoxic and inert and, thus, suitable for use in medical products. We evaluated the in vitro biocompatibility tests of the dressings to assess cytotoxicity and irritation, sensitization, pyrogen toxicity, and systemic toxicity following the International Organization for Standardization 10993 standards and the in vivo effects of the hydrogel samples using Coloskin liquid bandages as control samples for potential in wound closure.

Ocular adhesives: Design, chemistry, crosslinking mechanisms, and applications

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.

Transected Tendon Treated with a New Fibrin Sealant Alone or Associated with Adipose-Derived Stem Cells

Tissue engineering and cell-based therapy combine techniques that create biocompatible materials for cell survival, which can improve tendon repair. This study seeks to use a new fibrin sealant (FS) derived from the venom of Crotalus durissus terrificus, a biodegradable three-dimensional scaffolding produced from animal components only, associated with adipose-derived stem cells (ASC) for application in tendons injuries, considered a common and serious orthopedic problem. Lewis rats had tendons distributed in five groups: normal (N), transected (T), transected and FS (FS) or ASC (ASC) or with FS and ASC (FS + ASC). The in vivo imaging showed higher quantification of transplanted PKH26-labeled ASC in tendons of FS + ASC compared to ASC on the 14th day after transection. A small number of Iba1 labeled macrophages carrying PKH26 signal, probably due to phagocytosis of dead ASC, were observed in tendons of transected groups. ASC up-regulated the Tenomodulin gene expression in the transection region when compared to N, T and FS groups and the expression of TIMP-2 and Scleraxis genes in relation to the N group. FS group presented a greater organization of collagen fibers, followed by FS + ASC and ASC in comparison to N. Tendons from ASC group presented higher hydroxyproline concentration in relation to N and the transected tendons of T, FS and FS + ASC had a higher amount of collagen I and tenomodulin in comparison to N group. Although no marked differences were observed in the other biomechanical parameters, T group had higher value of maximum load compared to the groups ASC and FS + ASC. In conclusion, the FS kept constant the number of transplanted ASC in the transected region until the 14th day after injury. Our data suggest this FS to be a good scaffold for treatment during tendon repair because it was the most effective one regarding tendon organization recovering, followed by the FS treatment associated with ASC and finally by the transplanted ASC on the 21st day. Further investigations in long-term time points of the tendon repair are needed to analyze if the higher tissue organization found with the FS scaffold will improve the biomechanics of the tendons.

Pre-clinical assay of the tissue integration and mechanical adhesion of several types of cyanoacrylate adhesives in the fixation of lightweight polypropylene meshes for abdominal hernia repair

INTRODUCTION

Lightweight (LW) polypropylene (PP) meshes better adapt to host tissue, causing less fibrosis and inflammatory responses than high-density meshes. Mesh fixation using tissue adhesives (TA) that replace conventional sutures may improve the process of hernia repair and tissue trauma. This preclinical study compares the behavior of different cyanoacrylate-based adhesives in the fixation of LW-PP meshes for hernia repair.

METHODS

Partial abdominal wall defects were repaired using LW-PP Optilene meshes in New Zealand rabbits. The following groups were established according to the mesh fixation method: Suture (control), Glubran 2 (n-butyl), Ifabond (n-hexyl), SafetySeal (n-butyl) and Evobond (n-octyl). At 14, 90 and 180 days after surgery, the recovered implants were examined to assess the host tissue integration, the macrophage response and the biomechanical strength.

RESULTS

All the groups showed optimal host tissue incorporation regardless of the fixation procedure. Significantly increased levels of collagen 1 and collagen 3 gene expression (p<0.001) were observed at 14 days compared to the medium- and long-term durations, where the Suture and Glubran groups showed the highest expression of collagen 1. All the adhesives increased the macrophage reaction (p<0.001) compared to sutures at all implant times. Maximal macrophage response was observed in the short-term Glubran group (p<0.01) compared to the rest of the groups. Although SafetySeal and Evobond did not reach the biomechanical resistance of sutures at 14 days, all the adhesives did reach this level in the medium- to long-term periods, providing significantly higher resistance (p<0.05).

CONCLUSIONS

All the cyanoacrylates, despite inducing a significantly increased macrophage response versus sutures, showed optimal host tissue integration and long-term mechanical behavior; thus, they might be good choices for LW-PP mesh hernia repairs.

Solid Lipid-Polymer Hybrid Nanoparticles by In Situ Conjugation for Oral Delivery of Astaxanthin

Solid lipid-polymer hybrid nanoparticles (SLPN) are nanocarriers made from a combination of polymers and lipids, integrating the advantages of biocompatible lipid-based nanoparticles and gastrointestinal (GI)-stable polymeric nanoparticles. In this study, a novel preparation strategy was proposed to fabricate GI-stable SLPN through in situ conjugation between oxidized dextran and bovine serum albumin. Effects of molecular weight of dextran (20, 40, 75, and 150 kDa), conjugation temperature (65 °C, 75 °C, and 85 °C), and time (30, 60, 120 min) on the particulate characteristics and stability were comprehensively investigated and optimized. As heating temperature increased from 65 °C to 75 °C, the particle size of SLPN increased from 139 to 180 nm with narrow size distribution, but when the temperature reached 85 °C severe aggregation was observed after 60 min. SLPN prepared with 40 kDa oxidized dextran under 85 °C/30 min heating condition exhibited excellent GI stability with no significant changes in particle size and PDI after incubation in simulated GI fluids. The prepared SLPN were then used to encapsulate astaxanthin, a lipophilic bioactive compound, studied as a model nutrient. After encapsulation in SLPN, antioxidant activity of astaxanthin was dramatically enhanced in aqueous condition and a sustained release was achieved in simulated GI fluids. Therefore, the SLPN developed in this study are a promising oral delivery system for lipophilic compounds, such as astaxanthin.

The interplay between silk fibroin's structure and its adhesive properties

Bombyx mori-derived silk fibroin (SF) is a well-characterized protein employed in numerous biomedical applications. Structurally, SF consists of a heavy chain (HC) and a light chain (LC), connected via a single disulfide bond. The HC sequence is organized into 12 crystalline domains interspersed with amorphous regions that can transition between random coil/alpha helix and beta-sheet configurations, giving silk its hallmark properties. SF has been reported to have adhesive properties and shows promise for development of medical adhesives; however, the mechanism of these interactions and the interplay between SF's structure and adhesion is not understood. In this context, the effects of physical parameters (i.e., concentration, temperature, pH, ionic strength) and protein structural changes on adhesion were investigated in this study. Our results suggest that amino acid side chains that have functionalities capable of coordinate (dative) bond or hydrogen bond formation (such as those of serine and tyrosine), might be important determinants in SF's adhesion to a given substrate. Additionally, the data suggest that fibroin amino acids involved in beta-sheet formation are also important in the protein's adhesion to substrates.

Bioactive and Bioadhesive Catechol Conjugated Polymers for Tissue Regeneration

The effective treatment of chronic wounds constitutes one of the most common worldwide healthcare problem due to the presence of high levels of proteases, free radicals and exudates in the wound, which constantly activate the inflammatory system, avoiding tissue regeneration. In this study, we describe a multifunctional bioactive and resorbable membrane with in-built antioxidant agent catechol for the continuous quenching of free radicals as well as to control inflammatory response, helping to promote the wound-healing process. This natural polyphenol (catechol) is the key molecule responsible for the mechanism of adhesion of mussels providing also the functionalized polymer with bioadhesion in the moist environment of the human body. To reach that goal, synthesized statistical copolymers of N-vinylcaprolactam (V) and 2-hydroxyethyl methacrylate (H) have been conjugated with catechol bearing hydrocaffeic acid (HCA) molecules with high yields. The system has demonstrated good biocompatibility, a sustained antioxidant response, an anti-inflammatory effect, an ultraviolet (UV) screen, and bioadhesion to porcine skin, all of these been key features in the wound-healing process. Therefore, these novel mussel-inspired materials have an enormous potential for application and can act very positively, favoring and promoting the healing effect in chronic wounds.

Bioadhesives for internal medical applications: A review

Bioadhesives such as tissue adhesives, hemostatic agents, and tissue sealants have gained increasing popularity in different areas of clinical operations during the last three decades. Bioadhesives can be categorized into internal and external ones according to their application conditions. External bioadhesives are generally applied in topical medications such as wound closure and epidermal grafting. Internal bioadhesives are mainly used in intracorporal conditions with direct contact to internal environment including tissues, organs and body fluids, such as chronic organ leak repair and bleeding complication reduction. This review focuses on internal bioadhesives that, in contrast with external bioadhesives, emphasize much more on biocompatibility and adhesive ability to wet surfaces rather than on gluing time and intensity. The crosslinking mechanisms of present internal bioadhesives can be generally classified as follows: 1) chemical conjugation between reactive groups; 2) free radical polymerization by light or redox initiation; 3) biological or biochemical coupling with specificity; and 4) biomimetic adhesion inspired from natural phenomena. In this review, bioadhesive products of each class are summarized and discussed by comparing their designs, features, and applications as well as their prospects for future development.

STATEMENT OF SIGNIFICANCE

Despite the emergence of numerous novel bioadhesive formulations in recent years, thus far, the classification of internal and external bioadhesives has not been well defined and universally acknowledged. Many of the formulations have been proposed for treatment of several diseases even though they are not applicable for such conditions. This is because of the lack of a systematic standard or evaluation protocol during the development of a new adhesive product. In this review, the definition of internal and external bioadhesives is given for the first time, and with a focus on internal bioadhesives, the criteria of an ideal internal bioadhesive are adequately discussed; this is followed by the review of recently developed internal bioadhesives based on different gluing mechanisms.

Biofabricating Functional Soft Matter Using Protein Engineering to Enable Enzymatic Assembly

Biology often provides the inspiration for functional soft matter, but biology can do more: it can provide the raw materials and mechanisms for hierarchical assembly. Biology uses polymers to perform various functions, and biologically derived polymers can serve as sustainable, self-assembling, and high-performance materials platforms for life-science applications. Biology employs enzymes for site-specific reactions that are used to both disassemble and assemble biopolymers both to and from component parts. By exploiting protein engineering methodologies, proteins can be modified to make them more susceptible to biology's native enzymatic activities. They can be engineered with fusion tags that provide (short sequences of amino acids at the C- and/or N- termini) that provide the accessible residues for the assembling enzymes to recognize and react with. This "biobased" fabrication not only allows biology's nanoscale components (i.e., proteins) to be engineered, but also provides the means to organize these components into the hierarchical structures that are prevalent in life.

Mussel-Inspired Biomaterials for Cell and Tissue Engineering

In designing biomaterial for regenerative medicine or tissue engineering, there are a variety of issues to consider including biocompatibility, biochemical reactivity, and cellular interaction etc. Mussel-inspired biomaterials have received much attention because of its appealing features including strong adhesiveness on moist surfaces, enhancement of cell adhesion, immobilization of bioactive molecules and its amenability to post-functionalization via catechol chemistry. In this review chapter, we give a brief introduction on the basic principles of mussel-inspired polydopamine coating, catechol conjugation, and discuss how their features play a vital role in biomedical application. Special emphasis is placed on tissue engineering and regenerative applications. We aspire to give readers of this book a comprehensive insight into mussel-inspired biomaterials that can facilitate them make significant contributions in this promising field.

Engineering a highly elastic human protein-based sealant for surgical applications

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.

A highly adhesive and naturally derived sealant

Conventional surgical techniques to seal and repair defects in highly stressed elastic tissues are insufficient. Therefore, this study aimed to engineer an inexpensive, highly adhesive, biocompatible, and biodegradable sealant based on a modified and naturally derived biopolymer, gelatin methacryloyl (GelMA). We tuned the degree of gelatin modification, prepolymer concentration, photoinitiator concentration, and crosslinking conditions to optimize the physical properties and adhesion of the photocrosslinked GelMA sealants. Following ASTM standard tests that target wound closure strength, shear resistance, and burst pressure, GelMA sealant was shown to exhibit adhesive properties that were superior to clinically used fibrin- and poly(ethylene glycol)-based glues. Chronic in vivo experiments in small as well as translational large animal models proved GelMA to effectively seal large lung leakages without the need for sutures or staples, presenting improved performance as compared to fibrin glue, poly(ethylene glycol) glue and sutures only. Furthermore, high biocompatibility of GelMA sealant was observed, as evidenced by a low inflammatory host response and fast in vivo degradation while allowing for adequate wound healing at the same time. Combining these results with the low costs, ease of synthesis and application of the material, GelMA sealant is envisioned to be commercialized not only as a sealant to stop air leakages, but also as a biocompatible and biodegradable hydrogel to support lung tissue regeneration.

The effect of adhesives on inflammatory immune-markers during renal injury healing

Renal injury is common in abdominal trauma. Adhesives and sealants can be used to repair and preserve damaged organs. We describe the effect of three biomaterial treatments (TachoSil, GelitaSpon, and Adhflex) on injured renal tissue. Renal traumatic injuries were experimentally induced in male Wistar rats (n = 90) using a punch. Animals were divided into five groups: (1) sham noninjured (n = 3) and punch injury groups; (2) nontreated (n = 6); (3) TachoSil (n = 27); (4) GelitaSpon (n = 27); and (5) Adhflex (n = 27). Wound healing was evaluated 2, 6, and 18 days postinjury by inflammatory cytokines response, histopathological evolution of lesions, inflammatory reaction markers (CD68), and vascular neoformation (CD31). The TachoSil group showed the least inflammatory reaction among the three treated groups, which showed similarly low inflammatory reaction 18 days postinjury. Ciliary neurotrophic factor, soluble intercellular adhesion molecule-1, L-selectin, thymus chemokine, and TIMP metallopeptidase inhibitor 1 expression peaked between 2 and 6 days postinjury. TachoSil promoted the highest cytokine expression. The Adhflex group had the highest CD31 inflammatory immune-marker levels at 2 and 6 days postinjury, but there was a similar decrease in CD31 levels in all three groups at 18 days postinjury. The results show that all three sealant treatments induced a normal healing process with the typical pattern of proinflammatory cytokine and immune-marker expression. Each tested sealant substance could be suitable treatment for renal lacerations. The findings of this study indicate that Adhflex^® elastic cyanoacrylate does not induce an adverse inflammatory reaction, and therefore, could be considered as one of the first-line treatments for renal injuries. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1444-1455, 2018.

Adhesive coatings based on melanin-like nanoparticles for surgical membranes

Adhesive coatings for implantable biomaterials can be designed to prevent material displacement from the site of implant. In this paper, a strategy based on the use of melanin-like nanoparticles (MNPs) for the development of adhesive coatings for polysaccharidic membranes was devised. MNPs were synthesized in vitro and characterized in terms of dimensions and surface potential, as a function of pH and ionic strength. The in vitro biocompatibility of MNPs was investigated on fibroblast cells, while the antimicrobial properties of MNPs in suspension were evaluated on E. coli and S. aureus cultures. The manufacturing of the adhesive coatings was carried out by spreading MNPs over the surface of polysaccharidic membranes; the adhesive properties of the nano-engineered coating to the target tissue (intestinal serosa) were studied in simulated physiological conditions. Overall, this study opens for novel approaches in the design of naturally inspired nanostructured adhesive systems.

A hydrogel sealant for the treatment of severe hepatic and aortic trauma with a dissolution feature for post-emergent care

On-demand dissolvable hydrogel sealant reduces blood loss significantly in in vivo animal models of non-compressible hemorrhage.

Development of contact-killing non-leaching antimicrobial guanidyl-functionalized polymers via click chemistry

A new contact-killing and non-leaching antimicrobial polymer was prepared by a robust, efficient and orthogonal click-chemistry.

Quantitative 3D Time Lapse Imaging of Muscle Progenitors in Skeletal Muscle of Live Mice

For non-optically clear mammalian tissues, it is now possible to use multi-photon microscopy to penetrate deep into the tissue and obtain detailed single cell images in a live animal, i.e., intravital imaging. This technique is in principle applicable to any fluorescently marked cell, and we have employed it to observe stem cells during the regenerative process. Stem cell-mediated skeletal muscle regeneration in the mouse model has been classically studied at specific time points by sacrificing the animal and harvesting the muscle tissue for downstream analyses. A method for direct visualization of muscle stem cells to gain real-time information over a long period in a live mammal has been lacking. Here we describe a step-by-step protocol adapted from Webster et al. (2016) to quantitatively measure the behaviors of fluorescently labeled (GFP, EYFP) muscle stem and progenitor cells during homeostasis as well as following muscle injury.

The efficiency and safety of fibrin sealant for reducing blood loss in primary total hip arthroplasty: A systematic review and meta-analysis

OBJECTIVE

Total hip arthroplasty (THA) is associated with substantial blood loss. The objective of present systematic review and meta-analysis is to provide evidence from randomized controlled trials (RCTs) on the efficiency and safety of administration of fibrin sealant (FS) for reducing blood loss in patients undergoing primary THA.

METHODS

Potential relevant studies were identified from electronic databases including Medline, PubMed, Embase, ScienceDirect, web of science and Cochrane Library. Gray academic studies were also identified from the reference list of included studies. There was no language restriction. Pooling of data was carried out by using RevMan 5.1.

RESULTS

Six randomized controlled trials (RCTs) met the inclusion criteria. Current meta-analysis indicated that there were significant differences in terms of total blood loss (MD = -153.77, 95% CI: -287.21 to -20.34, P = 0.02), postoperative hemoglobin level (MD = -0.25, 95% CI: -0.46 to -0.05, P = 0.02) and transfusion rate (RD = -0.12, 95% CI: -0.22 to -0.03, P = 0.01) between groups. No significant differences were found regarding the incidence of deep venous thrombosis (DVT) (RD = 0.00, 95% CI: -0.01to 0.01, P = 0.51) or other side effects.

CONCLUSION

Administration of fibrin sealant in total hip arthroplasty may reduce total blood loss, postoperative hemoglobin decline and transfusion requirements. Moreover, no adverse effect was related to FS. Due to the limited quality of the evidence currently available, higher quality RCTs are required.

An in vitro study of fibrin sealant as a carrier system for recombinant human bone morphogenetic protein (rhBMP)-9 for bone tissue engineering

In the craniofacial bone field, fibrin sealants are used as coagulant and adhesive tools to stabilize grafts during surgery. Despite this, their exact role in osteogenesis is poorly characterized. In the present study, we aimed to characterize the osteogenic potential of TISSEEL fibrin sealant and used its technology to incorporate growth factors within its matrix. We focused on recombinant human bone morphogenetic protein (rhBMP)-9, which has previously been characterized as one of the strongest osteogenetic inducers in the BMP family. TISSEEL displayed an excellent ability to retain rhBMP9, which was gradually released over a 10-day period. Although TISSEEL decreased bone stromal ST2 cell attachment at 8 h, it displayed normal cell proliferation at 1, 3, and 5 days when compared to tissue culture plastic. Interestingly, TISSEEL had little influence on osteoblast differentiation; however its combination with rhBMP9 significantly increased ALP activity at 7 days, Alizarin Red staining at 14 days, and mRNA levels of osteoblast differentiation markers ALP, bone sialoprotein, and osteocalcin. In summary, although fibrin sealants were shown to have little influence on osteogenesis, their combination with bone-inducing growth factors such as rhBMP9 may serve as an attractive carrier/scaffold for future bone regenerative strategies. Future animal studies are now necessary.

Enhanced bioadhesivity of dopamine-functionalized polysaccharidic membranes for general surgery applications

An emerging strategy to improve adhesiveness of biomaterials in wet conditions takes inspiration from the adhesive features of marine mussel, which reside in the chemical reactivity of catechols. In this work, a catechol-bearing molecule (dopamine) was chemically grafted onto alginate to develop a polysaccharide-based membrane with improved adhesive properties. The dopamine-modified alginates were characterized by NMR, UV spectroscopy and in vitro biocompatibility. Mechanical tests and in vitro adhesion studies pointed out the effects of the grafted dopamine within the membranes. The release of HA from these resorbable membranes was shown to stimulate fibroblasts activities (in vitro). Finally, a preliminary in vivo test was performed to evaluate the adhesiveness of the membrane on porcine intestine (serosa). Overall, this functionalized membrane was shown to be biocompatible and to possess considerable adhesive properties owing to the presence of dopamine residues grafted on the alginate backbone.

STATEMENT OF SIGNIFICANCE

This article describes the development of a mussels-inspired strategy for the development of an adhesive polysaccharide-based membrane for wound healing applications. Bioadhesion was achieved by grafting dopamine moieties on the structural component on the membrane (alginate): this novel biomaterial showed improved adhesiveness to the intestinal tissue, which was demonstrated by both in vitro and in vivo studies. Overall, this study points out how this nature-inspired strategy may be successfully exploited for the development of novel engineered biomaterials with enhanced bioadhesion, thus opening for novel applications in the field of general surgery.

A Bio Polymeric Adhesive Produced by Photo Cross-Linkable Technique

The advantages of photo polymerization methods compared to thermal techniques are: rapid cure reactions, low energy demands, solvent free requirements and room temperature use. In order to form a macromer, polycaprolactone (PCL) was cross-linked via ultraviolet power with 2-isocyanatoethyl methacrylate. Different methods of characterization were carried out: estimation of swelling capacity, adhesive capacity (using aminated substrates), surface energy (by contact angle), and attenuated total reflectance Fourier transform infrared. In addition to these experiments, we carried out dynamical mechanical thermal analysis, thermogravimetry and thermorphology characterizations of PCL. Thus, it has been concluded that the prepared macromer could be transformed into membranes that were effective as a medical adhesive. The degree of cross linking has been estimated using two different techniques: swelling of the samples and photo cross linking of the samples with different periods of irradiation at relatively high UV-power (600 mW/cm²).

Sutureless closure of colonic defects with tissue adhesives: an in vivo study in the rat

BACKGROUND

Tissue adhesives (TAs) in gastrointestinal surgery are gradually gaining acceptance. Before implementation as colonic sealants, an evaluation of the sealing capability of a TA when in contact with fecal matter, as in a leaking anastomosis, is needed. In this study, we used clinically available TAs for the sutureless closure of colonic defects evaluating mechanical strength and tissue healing.

METHODS

A total of 160 rats were divided into 8 groups. Two .5-cm incisions were created, one in the proximal and another in the distal colon. Incisions were sealed with a TA: Histoacryl Flex, Bioglue, Dermabond, Tissucol, Duraseal Xact, gelatin-resorcinol-formaldehyde or Glubran 2. A control group was included in which the colonic defects were not sealed. Follow-up time was 3 or 10 days. Clinical complication rate, bursting pressure, and histopathologic analysis was included.

RESULTS

Leakage rates in the TA groups were highest for Duraseal Xact, Bioglue, and gelatin-resorcinol-formaldehyde at 3 and 10 days. The cyanoacrylates Glubran 2, Histoacryl Flex, and Omnex, and the fibrin glue Tissucol showed the lowest overall clinical complication rates while maintaining the highest bursting pressure at day 10. Histoacryl Flex exhibited significantly higher collagen formation at day 10 than the other TAs.

CONCLUSIONS

This experimental model evaluates the protective effect of a TA seal on a leaking colonic defect. We found large differences in leakage rates and inertness of the tested TAs. The cyanoacrylates Histoacryl Flex, Omnex, and Glubran 2 as well as the fibrin glue Tissucol demonstrated the lowest leakage rates and the most inert histopathologic profile while maintaining high mechanical strength.

What Is the Biological and Clinical Relevance of Fibrin?

As our knowledge of the structure and functions of fibrinogen and fibrin has increased tremendously, several key findings have given some people a superficial impression that the biological and clinical significance of these clotting proteins may be less than earlier thought. Most strikingly, studies of fibrinogen knockout mice demonstrated that many of these mice survive to weaning and beyond, suggesting that fibrin(ogen) may not be entirely necessary. Humans with afibrinogenemia also survive. Furthermore, in recent years, the major emphasis in the treatment of arterial thrombosis has been on inhibition of platelets, rather than fibrin. In contrast to the initially apparent conclusions from these results, it has become increasingly clear that fibrin is essential for hemostasis; is a key factor in thrombosis; and plays an important biological role in infection, inflammation, immunology, and wound healing. In addition, fibrinogen replacement therapy has become a preferred, major treatment for severe bleeding in trauma and surgery. Finally, fibrin is a unique biomaterial and is used as a sealant or glue, a matrix for cells, a scaffold for tissue engineering, and a carrier and/or a vector for targeted drug delivery.

Behaviour of the Biological Adhesives TachoSil®, GelitaSpon®, and a New Elastic Cyanoacrylate (Adhflex®) in Experimental Renal Trauma and Wound Healing

BACKGROUND

Renal injuries are relatively frequent in abdominal trauma. In some cases, adhesives and sealants can be used to repair and preserve injured organs. This paper describes the behaviour of three biomaterials - TachoSil®, GelitaSpon®, and a new elastic cyanoacrylate (CyA), Adhflex® - in standardized experimental renal injuries.

METHODS

Ninety male Wistar rats (300-350 g) were used. A Stiefel Biopsy Punch (8 mm diameter, 3 mm depth) was used to create injuries to the anterior kidney to evaluate wound healing. The animals were divided into five groups: (1) sham (n = 3); (2) control (n = 6), untreated, standard punch injury created on the anterior left kidney; (3) TachoSil® (n = 27), punch injury treated with TachoSil®; (4) GelitaSpon® (n = 27), punch injury treated with GelitaSpon®, and (5) Adhflex® (n = 27), punch injury treated with the new elastic CyA adhesive. The parameters studied were bleeding time, peritoneal adhesions, and histopathological evaluation of wound healing on days 2, 6, and 18, including measurements of the gap between wound edges, inflammatory reaction (CD68), and vascular neoformation (CD31).

RESULTS

The bleeding time was significantly shorter (27.7 ± 12.9 s) in the Adhflex® group than in the control (135.8 ± 11.6 s; p < 0.01), TachoSil® (77.5 ± 7.4 s; p < 0.05), and GelitaSpon® (82.5 ± 14.4 s; p < 0.05) groups. The incidence of intraperitoneal adhesions in the animals treated with Adhflex® was 3.6 times higher than in the non-treated group. It was also higher (p < 0.04) than in the groups treated with TachoSil® and GelitaSpon®. The time point with the largest gap between the wound edges and most abundant granulation tissue was at day 6. The largest gap after 18 days was reported for the Adhflex® adhesive. With regard to the markers CD31 and CD68, Adhflex® showed the largest areas 2 days after surgery, but no differences were found after 6 and 18 days versus the other treatments. The expression of the immunomarkers on the renal samples treated with Adhflex® was consistent with a normal healing process.

CONCLUSIONS

In this experimental model of renal injuries, the new elastic CyA (Adhflex®) resulted in the shortest bleeding time. It offers rapid sealing of the bleeding produced by renal injuries, fixation to adjacent tissues, and reduced occurrences of relapse. The evolution of the scarring is similar to other procedures. Given that traumatic renal injuries are always an emergency due to haemorrhage, Adhflex® might offer additional benefits over conventional treatment methods in human clinical practice.

Intravital Imaging Reveals Ghost Fibers as Architectural Units Guiding Myogenic Progenitors during Regeneration

How resident stem cells and their immediate progenitors rebuild tissues of pre-injury organization and size for proportional regeneration is not well understood. Using 3D, time-lapse intravital imaging for direct visualization of the muscle regeneration process in live mice, we report that extracellular matrix remnants from injured skeletal muscle fibers, "ghost fibers," govern muscle stem/progenitor cell behaviors during proportional regeneration. Stem cells were immobile and quiescent without injury whereas their activated progenitors migrated and divided after injury. Unexpectedly, divisions and migration were primarily bi-directionally oriented along the ghost fiber longitudinal axis, allowing for spreading of progenitors throughout ghost fibers. Re-orienting ghost fibers impacted myogenic progenitors' migratory paths and division planes, causing disorganization of regenerated muscle fibers. We conclude that ghost fibers are autonomous, architectural units necessary for proportional regeneration after tissue injury. This finding reinforces the need to fabricate bioengineered matrices that mimic living tissue matrices for tissue regeneration therapy.

Nanofibrous Snake Venom Hemostat

Controlling perioperative bleeding is of critical importance to minimize hemorrhaging and fatality. Patients on anticoagulant therapy such as heparin have diminished clotting potential and are at risk for hemorrhaging. Here we describe a self-assembling nanofibrous peptide hydrogel (termed SLac) that on its own can act as a physical barrier to blood loss. SLac was loaded with snake-venom derived Batroxobin (50 μg/mL) yielding a drug-loaded hydrogel (SB50). SB50 was potentiated to enhance clotting even in the presence of heparin. In vitro evaluation of fibrin and whole blood clotting helped identify appropriate concentrations for hemostasis in vivo. Batroxobin-loaded hydrogels rapidly (within 20s) stop bleeding in both normal and heparin-treated rats in a lateral liver incision model. Compared to standard of care, Gelfoam, and investigational hemostats such as Puramatrix, only SB50 showed rapid liver incision hemostasis post surgical application. This snake venom-loaded peptide hydrogel can be applied via syringe and conforms to the wound site resulting in hemostasis. This demonstrates a facile method for surgical hemostasis even in the presence of anticoagulant therapies.