A comparison of fibrin sealants in relation to their in vitro and in vivo properties

Profound Properties of Protein-Rich, Platelet-Rich Plasma Matrices as Novel, Multi-Purpose Biological Platforms in Tissue Repair, Regeneration, and Wound Healing

Autologous platelet-rich plasma (PRP) preparations are prepared at the point of care. Centrifugation cellular density separation sequesters a fresh unit of blood into three main fractions: a platelet-poor plasma (PPP) fraction, a stratum rich in platelets (platelet concentrate), and variable leukocyte bioformulation and erythrocyte fractions. The employment of autologous platelet concentrates facilitates the biological potential to accelerate and support numerous cellular activities that can lead to tissue repair, tissue regeneration, wound healing, and, ultimately, functional and structural repair. Normally, after PRP preparation, the PPP fraction is discarded. One of the less well-known but equally important features of PPP is that particular growth factors (GFs) are not abundantly present in PRP, as they reside outside of the platelet alpha granules. Precisely, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF) are mainly present in the PPP fraction. In addition to their roles as angiogenesis activators, these plasma-based GFs are also known to inhibit inflammation and fibrosis, and they promote keratinocyte migration and support tissue repair and wound healing. Additionally, PPP is known for the presence of exosomes and other macrovesicles, exerting cell-cell communication and cell signaling. Newly developed ultrafiltration technologies incorporate PPP processing methods by eliminating, in a fast and efficient manner, plasma water, cytokines, molecules, and plasma proteins with a molecular mass (weight) less than the pore size of the fibers. Consequently, a viable and viscous protein concentrate of functional total proteins, like fibrinogen, albumin, and alpha-2-macroglobulin is created. Consolidating a small volume of high platelet concentrate with a small volume of highly concentrated protein-rich PPP creates a protein-rich, platelet-rich plasma (PR-PRP) biological preparation. After the activation of proteins, mainly fibrinogen, the PR-PRP matrix retains and facilitates interactions between invading resident cells, like macrophages, fibroblast, and mesenchymal stem cells (MSCs), as well as the embedded concentrated PRP cells and molecules. The administered PR-PRP biologic will ultimately undergo fibrinolysis, leading to a sustained release of concentrated cells and molecules that have been retained in the PR-PRP matrix until the matrix is dissolved. We will discuss the unique biological and tissue reparative and regenerative properties of the PR-PRP matrix.

A Novel Fibrin Matrix Derived from Platelet-Rich Plasma: Protocol and Characterization

Although fibrin matrices derived from Platelet-Rich Plasma (PRP) are widely used in regenerative medicine, they have some limitations that can hinder their application. Modifying the composition of the PRP-derived fibrin matrix may improve its properties, making it suitable for certain medical uses. Three types of fibrin matrices were obtained: a PRP-derived fibrin matrix (FM), a PRP-derived fibrin matrix with a high fibrinogen content and platelets (FM-HFP) and a PRP-derived fibrin matrix with a high fibrinogen content (FM-HF). The fibrinogen levels, biomechanical properties and cell behavior were analyzed. The presence of platelets in the FM-HFP generated an inconsistent fibrin matrix that was discarded for the rest of the analysis. The fibrinogen levels in the FM-FH were higher than those in the FM (p < 0.0001), with a concentration factor of 6.86 ± 1.81. The values of clotting and swelling achieved using the FM-HF were higher (p < 0.0001), with less clot shrinkage (p < 0.0001). The FM had a significantly higher stiffness and turned out to be the most adherent composition (p = 0.027). In terms of cell viability, the FM-HF showed less cell proliferation but higher live/dead ratio values (p < 0.01). The increased fibrinogen and platelet removal in the FM-HF improved its adhesion and other biomechanical properties without affecting cell viability.

Annulus Fibrosus Repair for Lumbar Disc Herniation: A Meta-Analysis of Clinical Outcomes From Controlled Studies

STUDY DESIGN

Meta-analysis.

OBJECTIVES

This study aimed to summarize the clinical efficacy and safety of the various annular defect repair methods that have emerged in recent years.

METHODS

A meta-analysis of randomized and non-randomized controlled trials was conducted. Articles from PubMed, Embase, and the Cochrane Library (CENTRAL) on Lumbar disc herniation treatment with annular repair published from inception to April 2, 2022 were included. We summarized the clinical efficacy and safety of annular repair techniques based on a random-effects model meta-analysis.

RESULTS

7 randomized controlled studies and 8 observational studies with a total of 2161 participants met the inclusion criteria. The pooled data analysis showed that adding the annular repair technique reduced postoperative recurrence rate, reoperation rate, and loss of intervertebral height compared with lumbar discectomy alone. Subgroup analysis based on different annular repair techniques showed that the Barricaid Annular Closure Device (ACD) was effective in preventing re-protrusion and reducing reoperation rates, while there was no significant difference between the other subgroups. The annulus fibrosus suture (AFS) did not improve the postoperative Oswestry Disability Index (ODI). No statistically significant difference was observed in the incidence of adverse events between the annular repair and control groups.

CONCLUSIONS

Lumbar discectomy combined with ACD can effectively reduce postoperative recurrence and reoperation rates in patients with LDH. AFS alone was less effective in reducing recurrence and reoperation rates and did not improve postoperative pain and function.

In situ generated hemostatic adhesives: From mechanisms of action to recent advances and applications

Conventional surgical closure techniques, such as sutures, clips, or skin closure strips, may not always provide optimal wound closure and may require invasive procedures, which can result in potential post-surgical complications. As result, there is a growing demand for innovative solutions to achieve superior wound closure and improve patient outcomes. To overcome the abovementioned issues, in situ generated hemostatic adhesives/sealants have emerged as a promising alternative, offering a targeted, controllable, and minimally invasive procedure for a wide variety of medical applications. The aim of this review is to provide a comprehensive overview of the mechanisms of action and recent advances of in situ generated hemostatic adhesives, particularly protein-based, thermoresponsive, bioinspired, and photocrosslinkable formulations, as well as the design challenges that must be addressed. Overall, this review aims to enhance a comprehensive understanding of the latest advancements of in situ generated hemostatic adhesives and their mechanisms of action, with the objective of promoting further research in this field.

A comparative high-resolution physicochemical analysis of commercially available fibrin sealants: Impact of sealant osmolality on biological performance

Fibrin sealants are well-established components of the surgical toolbox, especially in procedures that harbor a high risk of perioperative bleeding. Their widespread use as hemostats, sealants or tissue-adhesives in various surgical settings has shown that the choice of the appropriate sealant system affects the clinical outcome. While many studies have compared the hemostatic efficiency of fibrin sealants to that of other natural or synthetic sealants, there is still limited data on how subtle differences in fibrin sealant formulations relate to their biological performance. Here, we performed an in-depth physicochemical and biological characterization of the two most commonly used fibrin sealants in the US and Europe: TISSEEL™ ("FS") and VISTASEAL™/VERASEAL™ ("FS+Osm"). Our chemical analyses demonstrated differences between the two sealants, with lower fibrinogen concentrations and supraphysiological osmolality in the FS+Osm formulation. Rheological testing revealed FS clots have greater clot stiffness, which strongly correlated with network density. Ultrastructural analysis by scanning electron microscopy revealed differences between FS and FS+Osm fibrin networks, the latter characterized by a largely amorphous hydrogel structure in contrast to the physiological fibrillar network of FS. Cytocompatibility experiments with human fibroblasts seeded on FS and FS+Osm fibrin networks, or cultured in presence of sealant extracts, revealed that FS+Osm induced apoptosis, which was not observed with FS. Although differential sealant osmolality and amounts of fibrinogen, as well as the presence of Factor XIII or additives such as antifibrinolytics, may explain the mechanical and structural differences observed between the two fibrin sealants, none of these substances are known to cause apoptosis at the respective concentrations in the sealant formulation. We thus conclude that hyper osmolality in the FS+Osm formulation is the primary trigger of apoptosis-a mechanism that should be evaluated in more detail, as it may affect the cellular wound healing response in situ.

Tissue Sealants for Facial Rhytidectomy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: The aging face can be surgically treated with a face-lift (rhytidectomy); however, bleeding and hematoma are complications that surgeons seek to prevent. Objective: To compare the drainage volume and rate of hematoma in studies of rhytidectomy among those having tissue sealants and those without. Methods: This systematic review and meta-analysis was prospectively registered in PROSPERO (CRD42022325404). We included randomized controlled trials (RCTs) that the enrolled participants undergoing rhytidectomy and used tissue sealants as the intervention. We calculated the mean and standard deviation for the drainage volume; risk ratios (RRs) were used for hematoma incidents. Results: Seven RCTs were included. The drainage volume was significantly lower in the tissue sealant group than in the control group (mean difference [MD]: -11.01, confidence interval [95% CI]: -18.39 to -3.63, p < 0.00001). As for hematomas, the incidence was also lower in the tissue sealant group (RR: 0.29, 95% CI: 0.08-0.99, p = 0.05). Conclusion: This study suggests that tissue sealants can be effective in reducing drainage volume and hematoma in face-lift; however, autologous and homologous tissue sealants can be further compared in future RCTs.

Nanoporous and nano thickness film-forming bioactive composition for biomedical applications

Unmanageable bleeding is one of the significant causes of mortality. Attaining rapid hemostasis ensures subject survivability as a first aid during combats, road accidents, surgeries that reduce mortality. Nanoporous fibers reinforced composite scaffold (NFRCS) developed by a simple hemostatic film-forming composition (HFFC) (as a continuous phase) can trigger and intensify hemostasis. NFRCS developed was based on the dragonfly wing structure's structural design. Dragonfly wing structure consists of cross-veins and longitudinal wing veins inter-connected with wing membrane to maintain the microstructural integrity. The HFFC uniformly surface coats the fibers with nano thickness film and interconnects the randomly distributed cotton gauge (Ct) (dispersed phase), resulting in the formation of a nanoporous structure. Integrating continuous and dispersed phases reduce the product cost by ten times that of marketed products. The modified NFRCS (tampon or wrist band) can be used for various biomedical applications. The in vivo studies conclude that the developed Cp NFRCS triggers and intensifies the coagulation process at the application site. The NFRCS could regulate the microenvironment and act at the cellular level due to its nanoporous structure, which resulted in better wound healing in the excision wound model.

Optimization of Fibrin Scaffolds to Study Friction in Cultured Mesothelial Cells

To study the friction of cell monolayers avoiding damage due to stress concentration, cells can be cultured on fibrin gels, which have a structure and viscoelasticity similar to that of the extracellular matrix. In the present research, we studied different gel compositions and surface coatings in order to identify the best conditions to measure friction in vitro. We examined the adhesion and growth behavior of mesothelial cell line MET-5A on fibrin gels with different fibrinogen concentrations (15, 20, and 25 mg/mL) and with different adhesion coatings (5 μg/mL fibronectin, 10 μg/mL fibronectin, or 10 μg/mL fibronectin + 10 μg/mL collagen). We also investigated whether different substrates influenced the coefficient of friction and the ability of cells to stick to the gel during sliding. Finally, we studied the degradation rates of gels with and without cells. All substrates tested provided a suitable environment for the adherence and proliferation of mesothelial cells, and friction measurements did not cause significant cell damage or detachment. However, in gels with a lower fibrinogen concentration, cell viability was higher and cell detachment after friction measurement was lower. Fibrinolysis was negligible in all the substrates tested.

Strength and deformability of fibrin clots: Biomechanics, thermodynamics, and mechanisms of rupture

Fibrin is the major determinant of the mechanical stability and integrity of blood clots and thrombi. To explore the rupture of blood clots, emulating thrombus breakage, we stretched fibrin gels with single-edge cracks of varying size. Ultrastructural alterations of the fibrin network correlated with three regimes of stress vs. strain profiles: the weakly non-linear regime due to alignment of fibrin fibers; linear regime owing to further alignment and stretching of fibers; and the rupture regime for large deformations reaching the critical strain and stress, at which irreversible breakage of fibers ahead of the crack tip occurs. To interpret the stress-strain curves, we developed a new Fluctuating Spring model, which maps the fibrin alignment at the characteristic strain, network stretching with the Young modulus, and simultaneous cooperative rupture of coupled fibrin fibers into a theoretical framework to obtain the closed-form expressions for the strain-dependent stress profiles. Cracks render network rupture stochastic, and the free energy change for fiber deformation and rupture decreases with the crack length, making network rupture more spontaneous. By contrast, mechanical cooperativity due to the presence of inter-fiber contacts strengthens fibrin networks. The results obtained provide a fundamental understanding of blood clot breakage that underlies thrombotic embolization. STATEMENT OF SIGNIFICANCE: Fibrin, a naturally occurring biomaterial, is the major determinant of mechanical stability and integrity of blood clots and obstructive thrombi. We tested mechanically fibrin gels with single-edge cracks and followed ultrastructural alterations of the fibrin network. Rupture of fibrin gel involves initial alignment and elastic stretching of fibers followed by their eventual rupture for deformations reaching the critical level. To interpret the stress-strain curves, we developed Fluctuating Spring model, which showed that cracks render rupture of fibrin networks more spontaneous; yet, coupled fibrin fibers reinforce cracked fibrin networks. The results obtained provide fundamental understanding of blood clot breakage that underlies thrombotic embolization. Fluctuating Spring model can be applied to other protein networks with cracks and to interpret the stress-strain profiles.

Comparison of fibrin sealants in peripheral vascular surgery: A systematic review and network meta-analysis

Background

Evidence comparing fibrin sealants (FSs) in surgery are limited. This study evaluated the efficacy and safety of FSs, and manual compression in peripheral vascular surgery.

Methods

A systematic review of randomized trials was conducted in Medline, Embase, and Cochrane databases within the last 15 years. Data were available to conduct a network meta-analysis (NMA) in peripheral vascular surgery. Fibrin sealant treatment arms were further broken-down and assessed by clotting time (i.e., 2-min [2C] or 1-min [1C]). The primary efficacy outcome was the proportion of patients achieving hemostasis by 4 min (T4). Treatment-related serious and non-serious adverse events (AEs) were qualitatively assessed.

Results

Five studies (n = 693), were included in the NMA. Results predicted VISTASEAL 2C, followed by EVICEL 1C, had the highest probability of achieving T4. Compared with manual compression, significant improvements in T4 were found with VISTASEAL 2C (relative risk [RR] = 2.67, 95% CrI: 2.13–3.34), EVICEL 1C (RR = 2.58, 95% CrI: 2.04–3.23), VISTASEAL 1C (RR = 2.00, 95% CrI: 1.45–2.65), and TISSEEL 2C (RR = 1.99, 95% CrI: 1.48–2.60). TISSEEL 1C was not significantly different than manual compression (RR = 1.40, 95% CrI: 0.70–2.33). Among FSs, VISTASEAL 2C was associated with a significant improvements in T4 compared with VISTASEAL 1C (RR = 1.33, 95% CrI: 1.02–1.82), TISSEEL 2C (RR = 1.34, 95% CrI: 1.05–1.77), and TISSEEL 1C (RR = 1.90, 95% CrI: 1.18–3.74). Treatment-related serious and non-serious AE rates were typically lower than 2%.

Conclusions

In peripheral vascular surgeries, VISTASEAL 2C and EVICEL 1C were shown to have the highest probabilities for achieving rapid hemostasis among the treatments compared. Future studies should expand networks across surgery types as data become available.

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Fibrin sealants can control perioperative bleeding, yet comparative evidence is limited.

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This network meta-analysis compared fibrin sealants and compression in peripheral vascular surgery.

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VISTASEAL and EVICEL had the highest probability of achieving hemostasis by 4 min.

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These results show differences exist between fibrin sealants in peripheral vascular surgery.

Strategies to use fibrinogen as bioink for 3D bioprinting fibrin-based soft and hard tissues

Fibrin gel has been widely used for engineering various types of tissues due to its biocompatible nature, biodegradability, and tunable mechanical and nanofibrous structural properties. Despite their promising regenerative capacity and extensive biocompatibility with various tissue types, fibrin-based biomaterials are often notoriously known as burdensome candidates for 3D biofabrication and bioprinting. The high viscosity of fibrin (crosslinked form) hinders proper ink extrusion, and its pre-polymer form, fibrinogen, is not capable of maintaining shape fidelity. To overcome these limitations and empower fibrinogen-based bioinks for fibrin biomimetics and regenerative applications, different strategies can be practiced. The aim of this review is to report the strategies that bring fabrication compatibility to these bioinks through mixing fibrinogen with printable biomaterials, using supporting bath supplemented with crosslinking agents, and crosslinking fibrin in situ. Moreover, the review discusses some of the recent advances in 3D bioprinting of biomimetic soft and hard tissues using fibrinogen-based bioinks, and highlights the impacts of these strategies on fibrin properties, its bioactivity, and the functionality of the consequent biomimetic tissue. Statement of Significance Due to its biocompatible nature, biodegradability, and tunable mechanical and nanofibrous structural properties, fibrin gel has been widely employed in tissue engineering and more recently, used as in 3D bioprinting. The fibrinogen's poor printable properties make it difficult to maintain the 3D shape of bioprinted constructs. Our work describes the strategies employed in tissue engineering to allow the 3D bioprinting of fibrinogen-based bioinks, such as the combination of fibrinogen with printable biomaterials, the in situ fibrin crosslinking, and the use of supporting bath supplemented with crosslinking agents. Further, this review discuss the application of 3D bioprinting technology to biofabricate fibrin-based soft and hard tissues for biomedical applications, and discuss current limitations and future of such in vitro models.

Rupture of blood clots: Mechanics and pathophysiology

Fibrin is the three-dimensional mechanical scaffold of protective blood clots that stop bleeding and pathological thrombi that obstruct blood vessels. Fibrin must be mechanically tough to withstand rupture, after which life-threatening pieces (thrombotic emboli) are carried downstream by blood flow. Despite multiple studies on fibrin viscoelasticity, mechanisms of fibrin rupture remain unknown. Here, we examined mechanically and structurally the strain-driven rupture of human blood plasma-derived fibrin clots where clotting was triggered with tissue factor. Toughness, i.e., resistance to rupture, quantified by the critical energy release rate (a measure of the propensity for clot embolization) of physiologically relevant fibrin gels was determined to be 7.6 ± 0.45 J/m2. Finite element (FE) simulations using fibrin material models that account for forced protein unfolding independently supported this measured toughness and showed that breaking of fibers ahead the crack at a critical stretch is the mechanism of rupture of blood clots, including thrombotic embolization.

Fibrin sealants in lumbar annuloplasty after endoscopic discectomy as a method to prevent recurrent lumbar disc herniation

Fibrin sealant as a promising agent for providing scaffold and efficient hemostasis is widely accepted in several specialties. However, the outcome of Fibrin sealants in lumbar annuloplasty after endoscopic discectomy has not been evaluated in patients with disc herniation. The goal of this study was to evaluate the efficacy, response, and probability of future recurrence rates in herniated nucleus pulposus (HNP) with the use of fibrin sealant in conjunction with endoscopic disc surgery. A total of 35 patients (28 men, 7women) were evaluated, including 18 patients who underwent endoscopic discectomy alone and 17 patients that received fibrin sealant at the site of annulus tear and endoscopic discectomy. All patients were followed through both clinical and imaging methods for an average of 10.5 months. Primary outcome measure was defined as lumbar decompression approved by imaging and symptom alleviation after endoscopic spinal discectomy with Visual Analogue Scale (VAS) score ≤ 4 (cut-off point). Median size of annular tearing was significantly lower in the endoscopic discectomy group (median, 3) (minimum, 2; maximum, 5); however, the corresponding factor in the endoscopic discectomy plus fibrin sealant group was significantly larger (median, 6) (minimum, 5; maximum, 10), with P <0.001. Only one patient in the endoscopic discectomy group had an HNP recurrence during follow-up compared to two patients in the endoscopic discectomy plus fibrin sealant group. Due to the temporary effects of fibrin sealant in preventing disc herniation and the observed recurrence rate in both the case and control groups, the results of this study suggest a role of fibrin sealants combined with endoscopic discectomy to prevent early HNP recurrence rate.

Fibrin sealants in lumbar annuloplasty after endoscopic discectomy as a method to prevent recurrent lumbar disc herniation

Fibrin sealant as a promising agent for providing scaffold and efficient hemostasis is widely accepted in several specialties. However, the outcome of Fibrin sealants in lumbar annuloplasty after endoscopic discectomy has not been evaluated in patients with disc herniation. The goal of this study was to evaluate the efficacy, response, and probability of future recurrence rates in herniated nucleus pulposus (HNP) with the use of fibrin sealant in conjunction with endoscopic disc surgery. A total of 35 patients (28 men, 7women) were evaluated, including 18 patients who underwent endoscopic discectomy alone and 17 patients that received fibrin sealant at the site of annulus tear and endoscopic discectomy. All patients were followed through both clinical and imaging methods for an average of 10.5 months. Primary outcome measure was defined as lumbar decompression approved by imaging and symptom alleviation after endoscopic spinal discectomy with Visual Analogue Scale (VAS) score ≤ 4 (cut-off point). Median size of annular tearing was significantly lower in the endoscopic discectomy group (median, 3) (minimum, 2; maximum, 5); however, the corresponding factor in the endoscopic discectomy plus fibrin sealant group was significantly larger (median, 6) (minimum, 5; maximum, 10), with P <0.001. Only one patient in the endoscopic discectomy group had an HNP recurrence during follow-up compared to two patients in the endoscopic discectomy plus fibrin sealant group. Due to the temporary effects of fibrin sealant in preventing disc herniation and the observed recurrence rate in both the case and control groups, the results of this study suggest a role of fibrin sealants combined with endoscopic discectomy to prevent early HNP recurrence rate.

Current State of Bone Adhesives-Necessities and Hurdles

The vision of gluing two bone fragments with biodegradable and biocompatible adhesives remains highly fascinating and attractive to orthopedic surgeons. Possibly shorter operation times, better stabilization, lower infection rates, and unnecessary removal make this approach very appealing. After 30 years of research in this field, the first adhesive systems are now appearing in scientific reports that may fulfill the comprehensive requirements of bioadhesives for bone. For a successful introduction into clinical application, special requirements of the musculoskeletal system, challenges in the production of a bone adhesive, as well as regulatory hurdles still need to be overcome. In this article, we will give an overview of existing synthetic polymers, biomimetic, and bio-based adhesive approaches, review the regulatory hurdles they face, and discuss perspectives of how bone adhesives could be efficiently introduced into clinical application, including legal regulations.

The clot thickens: Autologous and allogeneic fibrin sealants are mechanically equivalent in an ex vivo model of cartilage repair

Fibrin sealants are commonly used in cartilage repair surgeries to adhere cells or grafts into a cartilage defect. Both autologous and commercial allogeneic fibrin sealants are used in cartilage repair surgeries, yet there are no studies characterizing and comparing the mechanical properties of fibrin sealants from all-autologous sources. The objectives of this study were to investigate (i) the effect of fibrinogen and thrombin sources on failure mechanics of sealants, and (ii) how sealants affect the adhesion of particulated cartilage graft material (BioCartilage) to surrounding cartilage under physiological loading. Allogeneic thrombin and fibrinogen were purchased (Tisseel), and autologous sources were prepared from platelet-rich plasma (PRP) and platelet-poor plasma (PPP) generated from human blood. To compare failure characteristics, sealants were sandwiched between cartilage explants and pulled to failure. The effect of sealant on the adhesion of BioCartilage graft to cartilage was determined by quantifying microscale strains at the graft-cartilage interface using an in vitro cartilage defect model subjected to shear loading at physiological strains well below failure thresholds. Fibrinogen sources were not equivalent; PRP fibrinogen created sealants that were more brittle, failed at lower strains, and resulted in sustained higher strains through the graft-cartilage interface depth compared to PPP and allogeneic sources. PPP clotted slower compared to PRP, suggesting PPP may percolate deeper into the repair to provide more stability through the tissue depth. There was no difference in bulk failure properties or microscale strains at the graft-cartilage interface between the purely autologous sealant (autologous thrombin + PPP fibrinogen) and the commercial allogeneic sealant. Clinical Significance: All-autologous fibrin sealants fabricated with PPP have comparable adhesion strength as commercial allogeneic sealants in vitro, whereas PRP creates an inferior all-autologous sealant that sustains higher strains through the graft-cartilage interface depth.

A prospective, single-blind, randomized, phase III study to evaluate the safety and efficacy of Fibrin Sealant Grifols as an adjunct to hemostasis compared with manual compression in vascular surgery

OBJECTIVE

New formulations and applications of hemostatic adjuncts such as fibrin sealant (FS) to support local hemostasis and sutures continue to be developed. In a pivotal, confirmatory, controlled, prospective, single-blinded, randomized, multicenter phase III clinical trial, the efficacy and safety of FS Grifols during vascular surgeries were evaluated.

METHODS

Patients undergoing a nonemergency, open, peripheral vascular surgical procedure with moderate arterial bleeding were recruited. In an initial preliminary part of the study, all patients were treated with FS Grifols. In a subsequent primary part, patients were randomized (2:1) to FS Grifols or manual compression (MC). The primary efficacy end point was the proportion of the primary part patients achieving hemostasis by 4 minutes after the start of treatment. Cumulative proportion and time to hemostasis were secondary efficacy end points. Safety end points (in pooled preliminary and primary parts) included adverse events (AEs), vital signs, physical assessments, clinical laboratory tests, viral markers, and immunogenicity.

RESULTS

The primary efficacy end point was met by 76.1% of patients (83/109) for the FS Grifols group versus 22.8% of patients (13/57) for the MC group (P < .001). The cumulative proportion of patients at 5, 7, and 10 minutes was 80.7%, 84.4%, and 88.1%, respectively, in the FS Grifols treatment group, and 28.1%, 35.1%, and 45.6% in the MC treatment group (P < .001). The median time to hemostasis was shorter in the FS Grifols group (4 minutes vs ≥10 minutes in the MC group; P < .001). The nature of AEs reported were those expected in the study patient profile. The percentage of patients experiencing treatment-emergent AEs were similar in both the FS Grifols (pooled n = 59 + 109) and MC groups (81.0% and 77.2%, respectively), most recurrent being procedural pain (34.5% and 36.8%, respectively) and pyrexia (11.3% and 10.5%, respectively).

CONCLUSIONS

FS Grifols was superior in efficacy and similar in safety to MC as an adjunct local hemostatic agent in patients undergoing open vascular surgeries.

A Prospective, Single-Blind, Randomized, Phase III Study to Evaluate the Safety and Efficacy of Fibrin Sealant Grifols as an Adjunct to Hemostasis During Soft Tissue Open Surgery

BACKGROUND/PURPOSE

Rapid hemostasis, an essential prerequisite of good surgical practice during surgical bleeding, including soft tissue open surgery, often requires adjunctive treatment. We evaluated the safety and hemostatic effectiveness of a human plasma-derived fibrin sealant (FS Grifols) in soft tissue open surgery.

METHODS

Patients with moderate soft tissue bleeding during open, urologic, gynecologic or general surgery were studied. The trial consisted of a preliminary phase (to familiarize investigators with the technique for FS Grifols application and the intraoperative procedures required by the clinical protocol) and a primary phase: in both phases, patients were randomized 1:1 to FS Grifols or Surgicel^®. The primary efficacy endpoint, based on analysis of subjects in the primary phase of the study, was to evaluate whether FS Grifols was non-inferior to Surgicel^® in achieving hemostasis, based on the proportion of subjects in both treatment groups who achieved hemostasis at the target bleeding site (TBS) by 4 min (T₄) following the start of treatment application. Safety assessments included adverse events (AEs), vital signs, physical assessments, common clinical laboratory tests, viral markers, and immunogenicity.

RESULTS

A total of 224 subjects were randomized (primary phase): FS Grifols (N = 116), Surgicel^® (N = 108). The 95% CI at T₄ for the ratio of the proportion of patients achieving hemostasis in the two treatment groups was 1.064 (0.934, 1.213), indicating non-inferiority for FS Grifols vs. Surgicel^®. The rate of hemostasis at the TBS by T₄ in both phases of the study was higher in the FS Grifols treatment group (preliminary phase: 90.2%; primary phase: 82.8%) than in the Surgicel^® treatment group (preliminary phase: 78.8%; primary phase: 77.8%). Overall, reported AEs were as expected in surgical patients and were similar between the two treatment groups.

CONCLUSIONS

This study shows the non-inferiority in time to hemostasis of FS Grifols vs. Surgicel as an adjunct to hemostasis in patients undergoing soft tissue open surgery, and a similar rate of AEs.

Comparison of mechanical compressive properties of commercial and autologous fibrin glues for tissue engineering applications

BACKGROUND

Fibrin glues are widely used in orthopedic surgery as adhesives and hemostatic agents. We evaluated the compressive properties of selected fibrin glues in order to identify which are appropriate for tissue regeneration applications subject to compression.

METHODS

Uniaxial unconfined compression tests were performed on fibrin gels prepared from commercial and autologous products: (1) Evicel (Ethicon), (2) Tisseel (Baxter), (3) Angel (Arthrex), and (4) ProPlaz (Biorich). Cyclic loads were applied from 0 to 30% strain for 100cycles at 0.5Hz. Following cyclic testing, specimens were subjected to ramp displacement of 1% strain per second to 80% strain.

FINDINGS

Throughout cyclic loading, Evicel and Tisseel deformed (shortened) less than Angel at all but one time point, and deformed less than ProPlaz at cycles 10 and 20. The dynamic moduli, peak stress, and strain energy were significantly greater in Tisseel than all other groups. Evicel displayed significantly greater dynamic moduli, peak stress, and strain energy than Angel and ProPlaz. Following cyclic testing, Tisseel and Evicel were significantly less deformed than Angel. No specimens exhibited gross failure during ramp loading to 80% strain. Ramp loading trends mirrored those of cyclic loading.

INTERPRETATION

The tested commercial glues were significantly more resistant to compression than the autologous products. The compressive properties of Tisseel were approximately twice those of Evicel. All preparations displayed moduli multiple orders of magnitude less than that of native articular cartilage. We conclude that in knee surgeries requiring fibrin glue to undergo compression of daily activity, commercial products are preferable to autologous preparations from platelet-poor plasma, though both will deform significantly.

A review of fibrin and fibrin composites for bone tissue engineering

Tissue engineering has emerged as a new treatment approach for bone repair and regeneration seeking to address limitations associated with current therapies, such as autologous bone grafting. While many bone tissue engineering approaches have traditionally focused on synthetic materials (such as polymers or hydrogels), there has been a lot of excitement surrounding the use of natural materials due to their biologically inspired properties. Fibrin is a natural scaffold formed following tissue injury that initiates hemostasis and provides the initial matrix useful for cell adhesion, migration, proliferation, and differentiation. Fibrin has captured the interest of bone tissue engineers due to its excellent biocompatibility, controllable biodegradability, and ability to deliver cells and biomolecules. Fibrin is particularly appealing because its precursors, fibrinogen, and thrombin, which can be derived from the patient's own blood, enable the fabrication of completely autologous scaffolds. In this article, we highlight the unique properties of fibrin as a scaffolding material to treat bone defects. Moreover, we emphasize its role in bone tissue engineering nanocomposites where approaches further emulate the natural nanostructured features of bone when using fibrin and other nanomaterials. We also review the preparation methods of fibrin glue and then discuss a wide range of fibrin applications in bone tissue engineering. These include the delivery of cells and/or biomolecules to a defect site, distributing cells, and/or growth factors throughout other pre-formed scaffolds and enhancing the physical as well as biological properties of other biomaterials. Thoughts on the future direction of fibrin research for bone tissue engineering are also presented. In the future, the development of fibrin precursors as recombinant proteins will solve problems associated with using multiple or single-donor fibrin glue, and the combination of nanomaterials that allow for the incorporation of biomolecules with fibrin will significantly improve the efficacy of fibrin for numerous bone tissue engineering applications.

Isolation, Characterization and Evaluation of Collagen from Jellyfish Rhopilema esculentum Kishinouye for Use in Hemostatic Applications

Hemostat has been a crucial focus since human body is unable to control massive blood loss, and collagen proves to be an effective hemostat in previous studies. In this study, collagen was isolated from the mesoglea of jellyfish Rhopilema esculentum Kishinouye and its hemostatic property was studied. The yields of acid-soluble collagen (ASC) and pepsin-soluble (PSC) were 0.12% and 0.28% respectively. The SDS-PAGE patterns indicated that the collagen extracted from jellyfish mesoglea was type I collagen. The lyophilized jellyfish collagen sponges were cross-linked with EDC and interconnected networks in the sponges were revealed by scanning electron microscope (SEM). Collagen sponges exhibited higher water absorption rates than medical gauze and EDC/NHS cross-linking method could improve the stability of the collagen sponges. Compared with medical gauze groups, the blood clotting indexes (BCIs) of collagen sponges were significantly decreased (P < 0.05) and the concentration of collagen also had an influence on the hemostatic property (P < 0.05). Collagen sponges had an improved hemostatic ability compared to the gauze control in tail amputation rat models. Hemostatic mechanism studies showed that hemocytes and platelets could adhere and aggregate on the surface of collagen sponge. All properties make jellyfish collagen sponge to be a suitable candidate used as hemostatic material and for wound healing applications.

Circumcision with Glubran(®) 2 in children: experience of Italian Center

BACKGROUND

Circumcision is one of the most common surgical procedures in the world. Despite it is known its wide prevalence for religious and medical reasons in children, it remains a controversial practice in paediatric age. To date, there is no described the gold standard technique to circumcise paediatric patients. We started to use glue for circumcision about 2 years ago. We designed this prospective study with the aim to compare two surgical techniques, which were used in our hospital to perform circumcision in children. The implication for practice was the understanding if there were differences between these approaches related to patient's and parents benefits to manage this condition and benefits for surgeon and hospital in term of saving money and time.

METHODS

This is a randomized, single-blind one-center study. It was conducted at the Department of Paediatric Surgery of Siena. Data were collected between March 2011 and December 2012. Study's population involved all patients who required circumcision. Two randomizes groups: group one which involved patients who underwent circumcision using sutures and group two, which involved patients who underwent circumcision using surgical glue (Glubran(®) 2). Two exclusion criteria were used: the redo-circumcision and the allergy or hyper-sensibility to cyanoacrylate (main component of glue).

RESULTS

We report 99 patients who underwent circumcision with Glubran(®) 2 in comparison with a group of children circumcised with sutures (vycril rapide). We measured three outcomes (operating time, postoperative pain and assessment of cosmetic), which, even if not all statistically significant, allowed us to draw any conclusions about the use of glue in circumcision.

CONCLUSIONS

Traditional circumcision is performed using a standard sleeve technique with sutures for the approximation of the skin edges. However, since some years a tissue adhesive as N-butyl-2-cyanoacrylate (NBCA) (Glubran(®) 2) is used in many centers to circumcise children. Based on our results we can conclude that, glue (Glubran(®) 2) application is an excellent alternative to circumcision in paediatric age for a faster surgery, less postoperative pain and good early cosmetic.

Concentration of fibrin and presence of plasminogen affect proliferation, fibrinolytic activity, and morphology of human fibroblasts and keratinocytes in 3D fibrin constructs

Fibrin is a hemostatic protein found in the clotting cascade. It is used in the operating room to stop bleeding and deliver cells and growth factors to heal wounds. However, formulations of clinically approved fibrin are optimized for hemostasis, and the extent to which biochemical and physical cues in fibrin mediate skin cell behavior is not fully understood nor utilized in the design of biomaterials. To determine if the concentration of fibrinogen and the presence of plasminogen affect cell behavior relevant to wound healing, we fabricated three-dimensional fibrin constructs made from 5, 10, or 20 mg/mL of clinical fibrin or plasminogen-depleted (PD) fibrin. We cultured dermal fibroblasts or epidermal keratinocytes in these constructs. Fibroblasts proliferated similarly in both types of fibrin, but keratinocytes proliferated more in low concentrations of clinical fibrin and less in PD fibrin. Clinical fibrin constructs with fibroblasts were less stiff and degraded faster than PD fibrin constructs with fibroblasts. Similarly, keratinocytes degraded clinical fibrin, but not PD fibrin. Fibroblast spreading varied with fibrin concentration in both types of fibrin. In conclusion, the concentration of fibrinogen and the presence of plasminogen affect fibroblast and keratinocyte proliferation, morphology, and fibrin degradation. Creating materials with heterogeneous regions of fibrin formulations and concentrations could be a novel strategy for controlling the phenotype of encapsulated fibroblasts and keratinocytes, and the subsequent biomechanical properties of the construct. However, other well-investigated aspects of wound healing remain to be utilized in the design of fibrin biomaterials, such as autocrine and paracrine signaling between fibroblasts, keratinocytes, and immune cells.

Fibrin-genipin adhesive hydrogel for annulus fibrosus repair: performance evaluation with large animal organ culture, in situ biomechanics, and in vivo degradation tests

Annulus fibrosus (AF) defects from annular tears, herniation, and discectomy procedures are associated with painful conditions and accelerated intervertebral disc (IVD) degeneration. Currently, no effective treatments exist to repair AF damage, restore IVD biomechanics and promote tissue regeneration. An injectable fibrin-genipin adhesive hydrogel (Fib-Gen) was evaluated for its performance repairing large AF defects in a bovine caudal IVD model using ex vivo organ culture and biomechanical testing of motion segments, and for its in vivo longevity and biocompatibility in a rat model by subcutaneous implantation. Fib-Gen sealed AF defects, prevented IVD height loss, and remained well-integrated with native AF tissue following approximately 14,000 cycles of compression in 6-day organ culture experiments. Fib-Gen repair also retained high viability of native AF cells near the repair site, reduced nitric oxide released to the media, and showed evidence of AF cell migration into the gel. Biomechanically, Fib-Gen fully restored compressive stiffness to intact levels validating organ culture findings. However, only partial restoration of tensile and torsional stiffness was obtained, suggesting opportunities to enhance this formulation. Subcutaneous implantation results, when compared with the literature, suggested Fib-Gen exhibited similar biocompatibility behaviour to fibrin alone but degraded much more slowly. We conclude that injectable Fib-Gen successfully sealed large AF defects, promoted functional restoration with improved motion segment biomechanics, and served as a biocompatible adhesive biomaterial that had greatly enhanced in vivo longevity compared to fibrin. Fib-Gen offers promise for AF repairs that may prevent painful conditions and accelerated degeneration of the IVD, and warrants further material development and evaluation.

Comparison of commercial fibrin sealants in facelift surgery: a prospective study

Background

The aim of this study was to compare the effects of two types of fibrin glue in patients undergoing facelift surgery.

Methods

A prospective, controlled “right-left side” study was carried out in 20 patients. The two fibrin sealants used were Quixil® and Tissucol®. The two sealants were used at the same time, ie, one on one side of the face and the other on the contralateral side. Comparisons were made with regard to rates of hematoma and seroma, degree of induration, edema, ecchymosis, pain levels, and patient satisfaction.

Results

The results were almost equivalent. The only exception was a significant (40 mL) hematoma in a patient treated with Quixil. Bleeding was most likely due to a sudden rise in blood pressure during the immediate postoperative period. However, it must be emphasized that, while Tissucol actually seals the undermined area, thus virtually eliminating the dead space, Quixil acts differently, in that its effectiveness in preventing hematoma is linked mainly to its hemostatic effect.

Conclusion

The two fibrin sealants used were nearly identical with regard to patient safety and quality of the result. Nevertheless, it is noted that, while Tissucol has both hemostatic and “gluing” effects, Quixil is mainly effective in securing hemostasis.

A totally recombinant human fibrin sealant

BACKGROUND

Applications of plasma-derived human fibrin sealants (pdhFS) have been limited because of cost, limited supply of pathogen-screened plasma, the need for bioengineering improvements, and regulatory issues associated with federal approval. We describe a totally recombinant human fibrin sealant (rhFS), which may engender an abundant, safe, and cost-effective supply of efficacious fibrin sealant.

MATERIALS AND METHODS

A first-generation rhFS made from recombinant human fibrinogen (rhFI; produced in the milk of transgenic cows), activated recombinant human factor XIII (rhFXIIIa; produced in yeast), and recombinant human thrombin (rhFIIa; purchased, made in animal cell culture) was formulated using thromboelastography (TEG). The hemostatic efficacy of rhFS versus commercial pdhFS was compared in a nonlethal porcine hepatic wedge excision model.

RESULTS

The maximal clot strength of rhFS measured in vitro by TEG was not statistically different than that of pdhFS. TEG analysis also showed that the rhFS gained strength more quickly as reflected by a steeper α angle; however, the rhFS achieved this clot strength with a 5-fold lower factor I content than the pdhFS. When these fibrin sealants were studied in a porcine hepatic wedge excision model, the hemostatic scores of the rhFS were equivalent or better than that of the pdhFS.

CONCLUSIONS

The bioengineered rhFS had equivalent or better hemostatic efficacy than the pdhFS in a nonlethal hemorrhage model, despite the factor I concentration in the rhFS being about one-fifth that in the pdhFS. Because the rhFS is amenable to large-scale production, the rhFS has the potential to be more economical and abundant than the pdhFS, while having a decreased risk of blood-borne pathogen transmission.

Management of bleeding in the terminally ill patient

Clinically significant bleeding occurs in approximately 6%-10% of patients in the palliative-care setting. Bleeding can range from persistent and small in quantity (but enough to interfere with a patient's quality of life), to catastrophic bleeding that ultimately leads to the rapid demise of the patient. Uncontrolled bleeding can be very distressing for staff, patients and families. Advanced planning is necessary in all bleeding circumstances. This session will review the types of cancer associated with bleeding, as well as management options for these situations. Emphasis will be placed on aspects of communication with families.

Enhancing osteoconductivity of fibrin gels with apatite-coated polymer microspheres

Fibrin gels are a promising material for use in promoting bone repair and regeneration due to their ease of implant formation, tailorability, biocompatibility, and degradation by natural processes. However, these materials lack necessary osteoconductivity to nucleate calcium, integrate with surrounding bone, and promote bone formation. Polymeric substrata formed from poly(lactide-co-glycolide) (PLG) are widely used in bone tissue engineering. A carbonated apatite layer of bone-like mineral can be successfully grown on the surface of PLG microspheres after a multiday incubation process in modified simulated body fluid. Such coatings improve the osteoconductivity of the polymer, provide nucleation sites for cell-secreted calcium, and enhance the potential osseointegration with host tissue. We examined the capacity of mineralized polymeric microspheres suspended within fibrin hydrogels to enhance the osteoconductivity of fibrin gels and increase the osteogenic potential of these materials. The inclusion of microparticles, both nonmineralized and mineralized, reduced the capacity of mesenchymal stem cells (MSCs) to contract the gel. When cultured in osteogenic media, we detected a near linear increase in both calcium and phosphate incorporation in gels containing mineralized microspheres and entrapped MSCs. The osteoconductivity of acellular fibrin gels with mineralized and nonmineralized microspheres was assessed in a rodent calvarial bone defect over 12 weeks. Compared to untreated rodent calvarial bone defects, we detected significant increases in early vascularization when treated with fibrin gels, with greater vascularization, on average, occurring with gels containing microspheres. We detected a trend for increased bone mineral density in gels containing mineralized microspheres after 12 weeks. These findings demonstrate that the osteoconductivity of fibrin gels can be increased by inclusion of mineralized microspheres, but additional signals may be required to rapidly accelerate bone repair.

Tissue-regenerating functions of coagulation factor XIII

The protransglutaminase factor XIII (FXIII) has recently attracted attention within the field of tissue regeneration, as it has been found that FXIII significantly influences wound healing by exerting a multitude of functions. It supports hemostasis by enhancing platelet adhesion to damaged endothelium, and by its cross-linking activity it stabilizes the formed fibrin clot. Furthermore, FXIII limits bacterial dissemination from the wound and incorporates macromolecules of importance for cellular infiltration, supporting cell migration and survival. FXIII-mediated complex formation of the vascular endothelial growth factor receptor 2 and αV β3 integrin is important for angiogenesis, supporting the formation of granulation tissue. Chronic inflammatory conditions involving bleeding and activation of the coagulation cascade have been shown to lead to reduced FXIII levels in plasma. Of particular importance for this review is the fact that patients suffering from inflammatory bowel disease (IBD) have reduced FXIII antigen levels and activity. Furthermore, these patients show impaired mucosal healing, which supports the inflammatory state of the disease. This review summarizes the role of FXIII in the healing of wounds, and briefly summarizes the previous use of FXIII in clinical settings. Moreover, it addresses the potential role for FXIII as a therapeutic agent in the healing of persistent wounds during chronic conditions, with an emphasis on IBD.

Tensile strength of biological fibrin sealants: a comparative study

BACKGROUND

Fibrin sealants are commonly used in liver surgery, although their effectiveness in routine clinical practice remains controversial. Individual sealant characteristics are based on hemostatic effects and adhesion properties that can be experimentally measured using the 'rat skin test' or the 'pig skin test'. This study used a more relevant and realistic experimental canine model to compare the differences in the adhesive properties of four fibrin sealants in hepatectomy: Tisseel/Tissucol, Tachosil, Quixil, and Beriplast.

MATERIALS AND METHODS

A partial hepatectomy was performed in beagle dogs under general anesthesia to obtain liver cross-sections. Fibrin sealants were allocated to dog livers using a Youden square design. The tensile strength measurement was performed using a traction system to measure the rupture stress point of a small wooden cylinder bonded to the liver cross-section.

RESULTS

Significantly greater adhesion properties were observed with Tisseel/Tissucol compared with Quixil or Beriplast (P = 0.002 and 0.001, respectively). Similarly, Tachosil demonstrated significantly greater adhesive properties compared with Beriplast (P = 0.009) or Quixil (P = 0.014). No significant differences were observed between Tisseel/Tissucol and Tachosil or between Beriplast and Quixil.

CONCLUSIONS

The results of this comparative study demonstrate that different fibrin sealants exhibit different adhesive properties. Tisseel/Tissucol and Tachosil provided greatest adhesion to liver cross-section in our canine model of hepatectomy. These results may enable the optimal choice of fibrin sealants for this procedure in clinical practice.

Fibrin sealant (evicel® [quixil®/crosseal™]): a review of its use as supportive treatment for haemostasis in surgery

Evicel® is a fibrin sealant consisting of two components, human clottable protein (predominantly human fibrinogen) and human thrombin. It is indicated as supportive treatment in patients undergoing surgery when control of bleeding by standard surgical techniques is ineffective or impractical. Evicel® is a new formulation of the previously available fibrin sealant Quixil® (in the EU) or Crosseal™ (in the US). Evicel® differs from Quixil®/Crosseal™ in that its fibrinogen component does not contain the antifibrinolytic agent tranexamic acid, which is potentially neurotoxic, resulting in Quixil®/Crosseal™ being contraindicated for use in neurosurgery. The removal of tranexamic acid did not affect the haemostatic efficacy or longevity of Evicel® fibrin clots and allowed the sealant to be granted an expanded indication. Evicel® and Quixil®/Crosseal™ are easy to use and, since they do not contain synthetic or bovine aprotinin, have a reduced potential for hypersensitivity reactions. This article reviews the pharmacological properties, clinical efficacy and tolerability of Evicel® and its previous formulation as supportive treatment for haemostasis in surgery. In clinical studies, Evicel® and Quixil®/Crosseal™ were generally well tolerated and effective haemostatic agents for adjunctive use in various types of surgeries when conventional methods were impractical or ineffective in controlling bleeding. Two pivotal, randomized studies showed that Evicel® was significantly more effective than manual compression in patients undergoing vascular surgery, and significantly more effective than Surgicel® in patients undergoing retroperitoneal or intra-abdominal surgery, as assessed by the proportion of patients achieving haemostasis. In another similarly designed pivotal study in patients undergoing liver resection, Crosseal™ was significantly more effective than standard haemostatic agents (e.g. Surgicel®), as assessed by the mean time to haemostasis. The incidences of treatment-emergent adverse events in these studies were generally similar between the Evicel® or Crosseal™ groups and the comparator groups. Quixil® was also generally well tolerated and an effective haemostatic agent in endonasal surgeries, and tonsillectomies and/or adenoidectomies, with some benefit of treatment with Evicel® or Quixil® also observed in orthopaedic surgeries. Although additional comparative studies with other haemostatic agents would help to definitively position Evicel® with respect to these agents, current evidence suggests that Evicel® is useful in surgeries for improving haemostasis where standard surgical techniques are insufficient.

Determination of porcine fibrinogen in rat and dog plasma after intraperitoneal injection of a porcine-derived fibrin glue by fluorescein-labeled assay method: Comparison with isotope-labeled assay method

A sensitive and specific fluorescein isothiocyanate (FITC) label coupled with size-exclusion high-performance liquid chromatography-fluorescence detection (SE-HPLC-FLD) method was developed and validated for the estimation of the pharmacokinetic profiles of porcine fibrinogen after intraperitoneal injection of a porcine-derived fibrin glue (FG) to SD rats and beagle dogs with three single doses. Porcine fibrinogen, the major composition of the FG, was labeled with FITC. The FG containing FITC-labeled porcine fibrinogen was intraperitoneally administered to SD rats at three single dosages (100, 200, 400mg/kg of porcine fibrinogen), and the collected plasma was then detected by SE-HPLC-FLD method. The present technique was compared to the previously introduced isotope-labeled assay method for the pharmacokinetic studies in SD rats. The pharmacokinetic studies in SD rats showed that the correlation coefficient between the FITC-labeled assay and (125)I-labeled assay methods was r(2)=0.989. Thus, this FITC-labeled assay method performed well and demonstrated high concordance with the previous (125)I-labeled assay method, suggesting that FITC-labeled assay could substitute the (125)I-labeled assay as a method of choice for quantification in beagle dogs. Then the plasma levels of porcine fibrinogen in beagle dogs were studied by the FITC-labeled assay method with three single doses (15, 30, 60mg/kg of porcine fibrinogen). The method validation showed that the FITC label coupled with SE-HPLC-FLD method was suitable for the quantification of porcine fibrinogen in plasma samples with satisfactory linear (r(2)>0.999), precision (<12%), accuracy (95.5-104.9%) and recovery (>88%). The results showed linear disposition of porcine fibrinogen at the examined dosage range in SD rats or beagle dogs.

Percutaneous interventions in the coagulopathic patient

Interventional procedures in patients with coagulopathies carry a perceived risk of increased bleeding and complications. Acquired and inherited deficiencies of blood-clotting factors, thrombocytopenia and platelet dysfunction, and effect of anticoagulation are common problems encountered by practicing clinical interventional radiologists. In this article we review common coagulopathies, available data on percutaneous procedures in coagulopathic patients, and recommendations for periprocedure treatment.

Supplementation of fibrin gels with sodium chloride enhances physical properties and ensuing osteogenic response

Modifying the relative concentrations of fibrinogen and thrombin can control the physical properties of fibrin gels, while the viability of associated cells has been linked to the gel's final network structure. It was hypothesized that increasing the gel ionic strength during fabrication through supplementation with sodium chloride (NaCl) would provide an improved approach for tailoring the physical properties of fibrin gels and maintaining the viability and osteogenic potential of entrapped cells. Fibrin gels were formed by mixing fibrinogen, thrombin and calcium chloride with varying masses of NaCl (0-4.40% w/v), and the osteogenic potential of entrapped human mesenchymal stem cells (MSC) was examined over 14 days. Physical properties including gelation time, compressive modulus and fiber diameter were dependent upon NaCl content, with gels containing 2.60% NaCl possessing compressive moduli threefold higher than gels without NaCl. Alkaline phosphatase activity was highest for MSC entrapped in gels containing 2.15-2.60% NaCl after 14 days, and all gels exhibited increased calcium incorporation over the culture period. These data confirm that varying the salt concentration of the pre-gel solution can modulate the material properties of fibrin constructs without additional fibrinogen or thrombin, thereby offering a new approach for generating improved cell transplantation vehicles for use in bone tissue regeneration.

Cell Compatibility of Fibrin Sealants: In Vitro Study with Cells Involved in Soft Tissue Repair

Fibrin sealants can be used to support tissue regeneration or as vehicles for delivery of cells in tissue engineering. Differences in the composition of fibrin sealants, however, could determine the success of such applications. The results presented in this article show clear differences between Fibrin sealant A (FS A) clots and Fibrin sealant B (FS B) clots with respect to their compatibility with primary human cells involved in soft tissue repair. FS A clots, which are characterized by a physiological coarse fibrin structure, promoted attachment, spreading, and proliferation of keratinocytes, fibroblasts, and endothelial cells. In contrast, FS B clots displaying a fine to medium clot structure failed to support spreading of all three cell types. Adhesion of keratinocytes was decreased on FS B clots compared to FS A clots after 3 h incubation, whereas number of attached fibroblasts and endothelial cells was initially comparable between the two fibrin sealants. However, all three cell types proliferated on FS A clots but no sustained proliferation was detected on FS B clots. We further demonstrate that the observed differences between FS A and B clots are partly based upon 1 M sodium chloride extractable constituents, like thrombin, and partly on nonextractable constituents or the fibrin structure. In conclusion, our in vitro results demonstrate that FS A clots serve as a provisional matrix that encourages adhesion and growth of keratinocytes, fibroblasts, and endothelial cells. Therefore, FS A seems to be well suited for applications in tissue engineering.

Glubran2 surgical glue: in vitro evaluation of adhesive and mechanical properties

BACKGROUND

In surgical and endoscopic procedures, tissue adhesives are commonly used as reinforcement of sutures or as bonding and hemostatic agents. Fibrin glues do not guarantee adequate properties for many clinical applications; on the contrary, cyanoacrylate glues guarantee high bonding strength between biologic tissues. The aim of this study was to provide evidence regarding adhesive and strength properties of a widely used cyanoacrylate glue, Glubran2, GEM s.r.l., Viareggio, Italy. Comparative tests were also carried out on a commercial fibrin glue.

MATERIAL AND METHODS

Glubran2 is a modified n-butyl-2-cyanoacrylate glue approved for internal and external use, in Europe. The glue, on contact with living tissues polymerizes rapidly, generating a film that guarantees firm adherence of tissues. In this study, adhesive properties on biologic substrates, both of Glubran2 and of fibrin glue, were investigated according to American Society for Testing and Materials (ASTM) standards, while their strength, after polymerization on an inert substrate, was investigated according to Deutsches Institut Für Normung (DIN) standards.

RESULTS

All tests evidenced a strong bonding capability of Glubran2 on biologic tissues and high tensile strength of polymerized film; high breaking strength of polymerized glue was highlighted by tensile tests.

CONCLUSION

The present study fills the gap concerning Glubran2 adhesive and tensile properties. All tests showed the intrinsic tensile strength of polymerized Glubran2 and its capability to realize a higher-resistance bonding among biologic tissues, in comparison with fibrin glue, giving strong indication of its usefulness in surgical and endoscopic practice, especially in a wet environment.

Advantages of fibrin glue spray in laparoscopic liver biopsies

Fibrin glue has been shown to be a highly effective adjuvant in surgical repair. We present the case of a 14-year-old boy, who was operated on a right side abdominal neuroblastoma at the age of 4 years. The regular follow-up examinations later on were uneventful; however after 10 years, focal lesions were observed on the surface of the liver, which were confirmed by computer tomograms. To rule out further malignancy and histologically investigate the lesions, laparoscopic biopsy of the affected sites of the liver was performed. After obtaining the biopsy samples, the sites were sealed with fibrin glue using the special laparoscopic spray applicator head. The spray technique of sealing liver biopsy sites was found to be more effective and economical than the traditional technique of fibrin glue application. The advantages of spray application for parenchymatous organ intervention in the laparoscopic setting have been elaborated.

Evolution of fibrinogen-coated collagen patch for use as a topical hemostatic agent

Human fibrinogen and thrombin have been combined and coated onto a collagen patch for use as a topical hemostatic agent. These agents have now been used for many years to induce rapid hemostasis and tissue sealing after various indications including thoracic-, plastic-, pediatric-, liver-, and minimally invasive surgery. The only ready-to-use fibrinogen-coated collagen patch at this moment, the third-generation surgical patch (SP-3), contains no bovine aprotinin (antifibrinolytic protein) in contrast to its precursor SP-2, and is thus devoid of bovine-derived components. In vitro studies have shown equal bioequivalence between SP-2 and SP-3. Various experiments in animal models under normal, stressful, and hyperfibrinolytic conditions showed that SP-3 has comparable tissue sealing properties and also outperformed fibrin sealants alone in some studies. The results from these pre-clinical bridging studies showed that aprotinin is not essential for the therapeutic efficacy of SP-3. In conclusion, SP-3 has evolved into a rapid, ready-to-use adjunct to primary measures for tissue sealing and hemostasis, suitable in cardiovascular-, thoracic-, neuro-, spleen-, kidney-, and liver-surgery.

Development of a reinforced porcine elastin composite vascular scaffold

Elastin, a principal structural component of native arteries, has distinct biological and mechanical advantages when used as a biomaterial; however, its low ultimate tensile strength has limited its use as an arterial conduit. We have developed a scaffold, consisting of a purified elastin tubular conduit strengthened with fibrin bonded layers of acellular small intestinal submucosa (aSIS) for potential use as a small diameter vascular graft. The addition of aSIS increased the ultimate tensile strength of the elastin conduits nine-fold. Burst pressures for the elastin composite vascular scaffold (1,396 +/- 309 mmHg) were significantly higher than pure elastin conduits (162 +/- 36 mmHg) and comparable to native saphenous veins. The average suture pullout strength of the elastin composite vascular scaffolds was 14.612 +/- 3.677 N, significantly higher than the pure elastin conduit (0.402 +/- 0.098 N), but comparable to native porcine carotid arteries (13.994 +/- 4.344 N). Cyclic circumferential strain testing indicated that the composite scaffolds were capable of withstanding physiological loading conditions for at least 83 h. Implantation of the elastin composites as carotid interposition grafts in swine demonstrated its superiority to clinically acceptable ePTFE with significantly longer average patency times of 5.23 h compared to 4.15 h. We have developed a biologically based elastin scaffold with suitable mechanical properties and low thrombogenicity for in vivo implantation, and with the potential for cellular repopulation and host integration reestablishing an appropriate elastic artery.

New method to prepare autologous fibrin glue on demand

Fibrin-based sealants are commonly employed to arrest bleeding after surgery. Usually, fibrinogen obtained from pooled human plasma is used to prepare sealants, with attendant risk of blood-borne infections. Availability of autologous fibrinogen would eliminate this risk. To prepare autologous fibrin sealant, fibrinogen was precipitated from human plasma using protamine. Under optimal conditions (10-mg/mL protamine and 22 degrees C), 96 +/- 4% of clottable fibrinogen was recovered by a simple and inexpensive technique. Nearly 50% of the plasma factor XIII was also recovered with the fibrinogen. Using bovine thrombin, the fibrinogen was clotted (1) in a specially designed mold to measure tensile strength and (2) in a lap joint between 2 aortic vessel strips to measure adhesion strength. Tensile and adhesion strengths increased with increasing fibrinogen concentration, and they were increased by the addition of calcium chloride. The addition of aprotinin and -aminocaproic acid to the fibrinogen concentrate before clotting had no effect on the mechanical properties of the clots. After adding thrombin to sealant containing 15-mg/mL fibrinogen, maximum tensile strength was achieved in 1-5 min, and maximum adhesion strength was reached in 5-15 min. For the sealant with 30-60-mg/mL fibrinogen and added calcium, the tensile strength was equivalent to that of the commercial fibrin sealant Tisseel. The adhesion strength of sealant with 30-60-mg/mL fibrinogen exceeded the adhesive strength of Tisseel under identical conditions. Autologous fibrin sealant is an attractive alternative to commercial sealants. It can be readily prepared from 5-mL plasma or more and exhibits mechanical properties equivalent to those of the leading commercial sealant.