Fibrin sealants in surgical practice: An overview

Elastic sealants for surgical applications

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

Albumin removal from human fibrinogen preparations for manufacturing human fibrin-based biomaterials

Commercially available two component human fibrin sealants are commonly used to manufacture human fibrin-based biomaterials. However, this method is costly and allows little room for further tuning of the biomaterial. Human fibrinogen solutions offer a more cost-effective and versatile alternative to manufacture human fibrin-based biomaterials. Yet, human fibrinogen is highly unstable and contains certain impurities like human albumin. Within the context of biomaterials and tissue engineering we offer a simple yet novel solution based on classical biochemical techniques to significantly reduce albumin in human fibrinogen solutions. This method can be used for various tissue engineering and biomedical applications as an initial step in the manufacturing of human fibrin-based biomaterials to optimise their regenerative application.

Assessment of stem cell carriers for tendon tissue engineering in pre-clinical models

Tendon injuries are prevalent and problematic, especially among young and otherwise healthy individuals. The inherently slow innate healing process combined with the inevitable scar tissue formation compromise functional recovery, imposing the need for the development of therapeutic strategies. The limited number of low activity/reparative capacity tendon-resident cells has directed substantial research efforts towards the exploration of the therapeutic potential of various stem cells in tendon injuries and pathophysiologies. Severe injuries require the use of a stem cell carrier to enable cell localisation at the defect site. The present study describes advancements that injectable carriers, tissue grafts, anisotropically orientated biomaterials, and cell-sheets have achieved in preclinical models as stem cell carriers for tendon repair.

Efficacy and safety of aluminum chloride in controlling external hemorrhage: an animal model study

Background:

Despite all the progress in surgical science, bleeding caused by traffic accidents is still one of the challenges surgeons face in saving patients’ lives. Therefore, introducing an effective method to control external bleeding is an important research priority.

Objectives:

This study aimed to compare the hemostatic effect of aluminum chloride versus simple suturing in controlling external bleeding.

Materials and Methods:

This experimental study was conducted in Kashan, Iran. In this study, 60 male Wistar rats were randomly allocated into six groups. An incision, two centimeters (cm) long and half a cm deep, was made on each rat’s shaved back skin and the hemostatic time was measured once using aluminum chloride with different concentrations (5%, 10%, 15%, 25%, and 50%) and then using the control method (controlling hemorrhage by simple suturing). The skin tissue was assessed for pathological changes.

Results:

The hemostatic time of aluminum chloride 50%, 25%, 15%, 10% and 5% were 8.20 ± 0.919, 14.10 ± 1.37, 21.20 ± 1.31, 30.80 ± 1.68 and 42.00 ± 4.19 seconds, respectively. Also, the mean hemostasis time in the control group (suture) was 84.00 ± 4.05 seconds. The hemostatic times of different concentrations of aluminum chloride were significantly less than that of the control group. There was a statistically significant difference between every two hemostatic time. The pathologic examination showed the highest frequency of low-grade inflammation based on the defined pathological grading.

Conclusions:

The aluminum chloride method needs less time to control external hemorrhage compared to the control method (controlling external hemorrhage by simple suturing). Aluminum chloride is an effective agent in controlling external hemorrhage in an animal model.

Fibrin gel as an injectable biodegradable scaffold and cell carrier for tissue engineering

Due to the increasing needs for organ transplantation and a universal shortage of donated tissues, tissue engineering emerges as a useful approach to engineer functional tissues. Although different synthetic materials have been used to fabricate tissue engineering scaffolds, they have many limitations such as the biocompatibility concerns, the inability to support cell attachment, and undesirable degradation rate. Fibrin gel, a biopolymeric material, provides numerous advantages over synthetic materials in functioning as a tissue engineering scaffold and a cell carrier. Fibrin gel exhibits excellent biocompatibility, promotes cell attachment, and can degrade in a controllable manner. Additionally, fibrin gel mimics the natural blood-clotting process and self-assembles into a polymer network. The ability for fibrin to cure in situ has been exploited to develop injectable scaffolds for the repair of damaged cardiac and cartilage tissues. Additionally, fibrin gel has been utilized as a cell carrier to protect cells from the forces during the application and cell delivery processes while enhancing the cell viability and tissue regeneration. Here, we review the recent advancement in developing fibrin-based biomaterials for the development of injectable tissue engineering scaffold and cell carriers.

Investigating the effect of zinc chloride to control external bleeding in rats

Background:

Despite all progresses in surgical science, bleeding caused by traffic accidents is still a challenge for surgeons to save patients’ lives. Therefore, introducing an effective method to control external bleeding is an important research priority.

Objectives:

This study aimed to compare haemostatic effect of zinc chloride and simple suturing to control external bleeding.

Materials and Methods:

In this animal model study, 60 male Wistar rats were used. An incision (two cm in length and half a cm in depth) was made on shaved back of rats. The hemostasis time was measured once using zinc chloride with different concentrations (5%, 10%, 15%, 25%, and 50%) and then using simple suturing. Skin tissue was assessed for pathological changes. Due to abnormal distribution of variables in Kolmogorov-Smirnov test, the data was analyzed using Kruskal-Wallis test Mann-Whitney U tests.

Results:

In all the groups, complete hemostasis occurred. Hemostasis times of different concentrations of zinc chloride were significantly less than that of the control group (P < 0.001).

Conclusions:

Zinc chloride was effective to control external bleeding in rats.

Rational design of a degradable polyanion for layer-by-layer assembly for encapsulation and release of cationic functional biomolecules

We designed and synthesized a novel degradable polyanion, poly(phthalic ethylene glycol ester), that assembles with various polycationic biomolecules to form layer-by-layer films to encapsulate and release physiologically active biomolecules.

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.

Tissue sealants in endoscopic applications for anastomotic leakage during a 25-year period

BACKGROUND

Anastomotic leakage after gastrointestinal operation is a complication difficult to manage because conservative therapy and/or reoperation may be unsuccessful and carry the risk of increased morbidity and mortality. The endoscopic use of tissue sealants appears to be a promising alternative to avoid operation.

METHOD

We present conclusively our 25-year experience with tissue sealing in a series of 63 patients referred after gastrointestinal anastomosis leakage; 48 of the upper and 15 of the lower gastrointestinal tract, experiencing a drainage volume ranging 50-2,400 mL.

RESULTS

Tissue glue was applied orally in 37, anally in 10, through the fistula tract in 8, and through a combination of approximation routes in another 8 cases. Biological glue (fibrin) was used in 47, cyanoacrylate in 8, and both glue types in another 8 patients. The total volume of fibrin applied was 2-36 mL, in a median of four sessions, 0.5-4 mL for cyanoacrylate, in a median of two sessions, and, whenever a combination of glues was used, a volume of 12-40 mL of fibrin plus 1-4 mL of cyanoacrylate, in a median of nine sessions. The median hospital stay after initiation of gluing was 14 days (range 8-32). The clinical and technical success rate was 96.8% (61 of 63 patients).

CONCLUSION

Tissue glue appears to be a valuable clinical tool that would prevent further operative interventions and the associated morbidity and mortality after a gastrointestinal anastomosis dehiscence. However, it must be borne in mind that repeated sessions and large volumes of sealants are necessary in many cases.

Physical and biological characterization of ferromagnetic fiber networks: effect of fibrin deposition on short-term in vitro responses of human osteoblasts

Ferromagnetic fiber networks have the potential to deform in vivo imparting therapeutic levels of strain on in-growing periprosthetic bone tissue. 444 Ferritic stainless steel provides a suitable material for this application due to its ability to support cultures of human osteoblasts (HObs) without eliciting undue inflammatory responses from monocytes in vitro. In the present article, a 444 fiber network, containing 17 vol% fibers, has been investigated. The network architecture was obtained by applying a skeletonization algorithm to three-dimensional tomographic reconstructions of the fiber networks. Elastic properties were measured using low-frequency vibration testing, providing globally averaged properties as opposed to mechanical methods that yield only local properties. The optimal region for transduction of strain to cells lies between the ferromagnetic fibers. However, cell attachment, at early time points, occurs primarily on fiber surfaces. Deposition of fibrin, a fibrous protein involved in acute inflammatory responses, can facilitate cell attachment within this optimal region at early time points. The current work compared physiological (3 and 5 g·L(-1)) and supraphysiological fibrinogen concentrations (10 g·L(-1)), using static in vitro seeding of HObs, to determine the effect of fibrin deposition on cell responses during the first week of cell culture. Early cell attachment within the interfiber spaces was observed in all fibrin-containing samples, supported by fibrin nanofibers. Fibrin deposition influenced the seeding, metabolic activity, and early stage differentiation of HObs cultured in the fibrin-containing fiber networks in a concentration-dependant manner. While initial cell attachment for networks with fibrin deposited from low physiological concentrations was similar to control samples without fibrin deposition, significantly higher HObs attached onto high physiological and supraphysiological concentrations. Despite higher cell numbers with supraphysiological concentrations, cell metabolic activities were similar for all fibrinogen concentrations. Further, cells cultured on supraphysiological concentrations exhibited lower cell differentiation as measured by alkaline phosphatase activity at early time points. Overall, the current study suggests that physiological fibrinogen concentrations would be more suitable than supraphysiological concentrations for supporting early cell activity in porous implant coatings.

Comparison of a collagen membrane versus a fibrin sealant after a peroneal nerve section and repair: a functional and histological study

BACKGROUND

To date, fibrin sealant is considered to be one of the most effective substitutes to prevent post-operative fibrosis and to limit neuroma formation after nerve suture. Because fibrin sealant presents a number of drawbacks, more suitable techniques should be considered. The aim of this study was to functionally and histologically compare the efficiency of a fibrin sealant to a resorbable semi-permeable porcine type I collagen membrane after a peroneal nerve lesion and repair on rats.

METHODS

Rats were divided into four groups: (1) a SHAM group (n = 10) in which surgery was performed without damaging the nerve, (2) a LESION group (n = 15) in which the nerve was cut and immediately sutured without additional treatment, (3) a MEMBRANE group (n = 30) in which a collagen membrane was wrapped around the lesion site, and (4) a GLUE group (n = 30) in which the peroneal nerve was coated by fibrin sealant. Peroneal Functional Index (PFI), kinematic analysis of locomotion, muscular atrophy, axonal regrowth, and irritant ranking score (IRS) were performed during three months post-surgery.

RESULTS

Our results indicate that at the third month post-surgery, no difference in both the functional recovery and the histological measurement was observed between groups. However, no deleterious effect was observed following the use of the collagen membrane. Indeed, the porcine membrane was well-integrated into the host tissue, with no noticeable foreign body reaction at three months post-surgery.

CONCLUSION

Our preliminary results highlight the fact that the collagen membrane could be used as an alternative to fibrin sealant in peripheral nerve repair surgery. Indeed, animals in which the collagen membrane was used to wrap the lesion site exhibited similar functional and histological results as animals in which a fibrin sealant was used to coat the lesion. The greatest advantage of this membrane is that it could be used as a drug delivery device, regulated by its degradation rate.

Fibrin-mediated delivery of an ovarian follicle pool in a mouse model of infertility

The cryopreservation and autotransplantation of ovarian tissue is emerging as a powerful approach for preserving fertility. However, for cancer patients, it may not be possible to transplant ovarian tissue due to the risk of re-seeding disease. We investigated strategies for transplantation of individually isolated follicles to minimize the risk of re-introducing cancer cells present within the vasculature of ovarian stroma. Procedures for large-scale isolation of early-stage follicles and their encapsulation into fibrin hydrogels were developed. For in vivo validation studies, mice were ovariectomized and transplanted with encapsulated follicles into the ovarian bursa. A substantial increase in the number of secondary follicles was observed in the graft at 9 days after transplantation, and antral follicles by day 21, demonstrating primordial follicle recruitment into the growing pool. Initially, elevated follicle-stimulating hormone levels declined substantially by day 21, indicating feedback from the graft; presence of corpora lutea showed the graft's capability of restoring hormone cyclicity. Taken together, the transplanted follicles were able to engraft, mature, and restore ovarian function in an infertile mouse. This biomaterial may, thus, provide a platform for follicle transplantation with a low risk of cancer contamination and for developing strategies that preserve fertility for women facing a cancer diagnosis.

Efficacy and safety of ferric chloride in controlling hepatic bleeding; an animal model study

BACKGROUND

Controlling parenchymal hemorrhage especially in liver parenchyma, despite all the progress in surgical science, is still one of the challenges surgeons face saving patients' lives and there is a research challenge among researchers in this field to introduce a more effective method.

OBJECTIVES

This study attempts to determine the haemostatic effect of ferric chloride and compare it with that of the standard method (suturing technique) in controlling bleeding from liver parenchymal tissue.

MATERIALS AND METHODS

In this animal model study 60 male Wistar rats were used. An incision, two centimeters (cm) long and half a cm deep, was made on each rat's liver and the hemostasis time was measured once using ferric chloride with different concentrations (5%, 10%, 15%, 25% and 50%) and then using the control method (i.e. controlling bleeding by suturing). The liver tissue was examined for pathological changes.

RESULTS

The hemostasis time of ferric chloride concentration groups was significantly less than that of the control group (P value < 0.001). The pathologic examination showed the highest frequency of low grade inflammation based on the defined pathological grading.

CONCLUSIONS

Ferric chloride is an effective haemostatic agent in controlling liver parenchymal tissue hemorrhage in an animal model.

Is fibrin sealant effective and safe in total knee arthroplasty? A meta-analysis of randomized trials

The objective of this study was to evaluate the efficacy and safety of fibrin sealant in patients following total knee arthroplasty (TKA). A comprehensive literature search of the electronic databases PubMed, MEDLINE, Web of Science, and Cochrane Library for published randomized controlled trials (RCTs) was undertaken. The evidence base was critically appraised using a tool from the Cochrane Bone, Joint and Muscle Trauma Group. Eight RCTs involving 641 patients were included. The use of fibrin sealant significantly reduced postoperative drainage (weighted mean difference (WMD) -346, 95% confidence interval (CI) -496.29 to -197.54, P < 0.00001) and blood transfusions (risk ratio (RR) 0.47, 95% CI 0.35 to 0.63, P < 0.00001) and led to a significant improvement in the range of motion (WMD 16.59, 95% CI 6.92 to 26.25, P = 0.0008). However, using fibrin sealant did not significantly reduced total blood loss (WMD -305.25, 95% CI -679.44 to 68.95, P = 0.11). Regarding complications, there were no significant differences in any adverse events, fever, infection, or hematoma among the study groups. In conclusion, the present meta-analysis indicates that the use of fibrin sealant was effective and safe as a hemostatic therapy for patients with TKA.

Sculpting the blank slate: how fibrin's support of vascularization can inspire biomaterial design

Fibrin is the primary extracellular constituent of blood clots, and plays an important role as a provisional matrix during wound healing and tissue remodeling. Fibrin-based biomaterials have proven their utility as hemostatic therapies, scaffolds for tissue engineering, vehicles for controlled release, and platforms for culturing and studying cells in three dimensions. Nevertheless, fibrin presents a complex milieu of signals to embedded cells, many of which are not well understood. Synthetic extracellular matrices (ECMs) provide a blank slate that can ostensibly be populated with specific bioactive cues, including growth factors, growth factor binding motifs, adhesive peptides and peptide crosslinks susceptible to proteases, thereby enabling a degree of customization for specific applications. However, the continued evolution and improvement of synthetic ECMs requires parallel efforts to deconstruct native ECMs and decipher the cues they provide to constituent cells. The objective of this review is to reintroduce fibrin, a protein with a well-characterized structure and biochemistry, and its ability to support angiogenesis specifically. Although fibrin's structure-function relationships have been studied for decades, opportunities to engineer new and improved synthetic hydrogels can be realized by further exploiting fibrin's inspiring design.

Fibrin sealants: surgical hemostat, sealant and adhesive

INTRODUCTION

Fibrin sealants (FS) have been approved for use in the United States since 1998. Since approval, they have been used in a wide variety of clinical settings and new products continue to be introduced.

AREAS COVERED

This review covers the literature supporting the USA FDA-approved indications for FS products produced by Baxter Corp. Literature review of PubMed, the Cochrane Library, FDA approval documents and product websites yielded information contained in this article. Mechanism of action, efficacy and safety of these products are covered.

EXPERT OPINION

FS are generally safe, popular and are used for a wide variety of off-label indications. Their use appears to be expanding rapidly. For many uses, including approved ones, large well-controlled trials are still needed. Additionally, cost-effectiveness data for these products would be a great benefit in guiding their future use.

Endoscopic treatment of iatrogenic gastrointestinal perforations: an overview

In the past, the treatment of iatrogenic gastrointestinal perforations was limited to surgical management or to medical observation. Natural Orifice Transluminal Endoscopic Surgery (NOTES) has paved the way towards the development of reliable endoscopic closure techniques, which can be applicable in accidental perforations of the gastrointestinal tract. When endoscopic treatment is feasible, hemoclips are preferred in smaller perforations, while over-the-scope-clips or a combination of hemoclips, endoloops, and glue are used in larger ones. Endoscopic stitching is rarely utilized, and endoscopic stapling has been practically abandoned. The use of self-expandable covered stents can be considered in the esophagus and duodenum. Broad spectrum antibiotics are recommended in most cases. Clinical follow-up in a medico-surgical unit is mandatory and surgical intervention should not be delayed more than 24h if clinical or biological worsening occurs. Imaging with oral contrast medium is advisable before resumption of oral feeding in the case of large perforations.

Pleural tissue repair with cord blood platelet gel

BACKGROUND

Prolonged air leak is the major cause of morbidity after pulmonary resection. In this study we used in vitro and in vivo experiments to investigate an innovative approach based on the use of human umbilical cord blood platelet gel.

MATERIALS AND METHODS

In vitro, a scratch assay was performed to test the tissue repair capability mediated by cord blood platelet gel compared to the standard culture conditions using human primary mesothelial cells. In vivo, an iatrogenic injury was made to the left lung of 54 Wistar rats. Cord blood platelet gel was placed on the injured area only in treated animals and at different times histological changes and the presence of pleural adhesions were evaluated. In addition, changes in the pattern of soluble inflammatory factors were investigated using a multiplex proteome array.

RESULTS

In vitro, mesothelial cell damage was repaired in a shorter time by cord blood platelet gel than in the control condition (24 versus 35 hours, respectively). In vivo, formation of new mesothelial tissue and complete tissue recovery were observed at 45±1 and 75±1 hours in treated animals and at 130±2.5 and 160±6 hours in controls, respectively. Pleural adhesions were evident in 43% of treated animals compared to 17% of controls. No complications were observed. Interestingly, some crucial soluble factors involved in inflammation were significantly reduced in treated animals.

DISCUSSION

Cord blood platelet gel accelerates the repair of pleural damage and stimulates the development of pleural adhesions. Both properties could be particularly useful in the management of prolonged air leak, and to reduce inflammation.

Reducing blood loss after total knee replacement

Blood loss during total knee replacement (TKR) remains a significant concern. In this study, 114 patients underwent TKR, and were divided into two groups based on whether they received a new generation fibrin sealant intra-operatively, or a local infiltration containing adrenaline. Groups were then compared for mean calculated total blood volume (TBV) loss, transfusion rates, and knee range of movement. Mean TBV loss was similar between groups: fibrin sealant mean was 705 ml (281 to 1744), local adrenaline mean was 712 ml (261 to 2308) (p = 0.929). Overall, significantly fewer units of blood were transfused in the fibrin sealant group (seven units) compared with the local adrenaline group (15 units) (p = 0.0479). Per patient transfused, significantly fewer units of blood were transfused in the fibrin sealant group (1.0 units) compared with the local adrenaline group (1.67 units) (p = 0.027), suggesting that the fibrin sealant may reduce the need for multiple unit transfusions. Knee range of movement was similar between groups. From our results, it appears that application of this newer fibrin sealant results in blood loss and transfusion rates that are low and similar to previously applied fibrin sealants.

Cite this article: Bone Joint J 2013;95-B, Supple A:135–9.

Autologous platelet rich fibrin glue for sealing of low-output enterocutaneous fistulas: an observational cohort study

BACKGROUND

Glue sealing has become an alternative option for occlusion of enterocutaneous fistula (ECF) because of it minimal invasiveness and simplicity. This study aimed to determine efficacy and safety of autologous, platelet-rich fibrin glue (PRFG) in promoting closure of ECFs.

METHODS

This was a nonrandomized cohort study, recruiting patients who had low-output ECFs (<200 mL/24 h). Beside standard of care, patients were assigned to either the PRFG or control group. Clinical efficacy and safety were determined prospectively. Moreover, a well-balanced subcohort was generated by propensity score (PS) matching. Unadjusted and adjusted Cox proportional hazard models were employed to determine hazard ratios (HRs) of ECF closure in both cohorts.

RESULTS

From January 2008 to January 2012, 145 patients were enrolled initially, with 70 in the control group and 75 in the PRFG-treated group. Compared with the control group, patients in the PRFG group had lesser median time of fistula closure (7 vs 23 days; P = .0010). In addition, PRFG healed more fistulas within the first 28 days (77% vs 57%; P = .0127). For all fistulas included, PRFG-treated fistulas were 3.13 (95% confidence interval [CI], 1.82-5.36) times more likely to achieve closure than those with the non-PRFG approach in the adjusted Cox model. In a PS-matched cohort with 28 paired fistulas, HRs were 3.41 (95% CI, 1.91-6.07) for all fistulas regardless of location. No adverse events related to glue applications were observed.

CONCLUSION

Autologous PRFG seems to be safe and effective in the treatment of low-output ECFs, and can lessen closure times and promote closure rates.

Comparison of hemostatic agents used in vascular surgery

INTRODUCTION

Over the past 15 years, a wide range of agents have been developed for use in surgical procedures to achieve hemostasis. These agents can be divided into three broad categories: hemostats, sealants and adhesives. They vary widely related to their mechanism of action, composition, ease of application, adherence to wet or dry tissue, immunogenicity and cost.

AREAS COVERED

This article focuses on the agents used in vascular surgery to achieve hemostasis; agents involved in clinical trials are also covered.

EXPERT OPINION

When surgeons achieve rapid hemostasis, potential benefits include better visualization of the surgical area, shorter operative times, decreased requirement for transfusions, better management of an anticoagulated patient, decreased wound healing time and overall improvement in patient recovery time. The need for safe and efficacious hemostatic agents that can provide a range of benefits is clearly a significant surgical issue.

Evaluation of a gelatin matrix as a topical hemostatic agent for hepatic bleeding in the dog

New generation topical hemostatic agents containing thrombin have been developed for use in surgical procedures when control of bleeding by conventional methods is either ineffective or impractical. The authors compared the safety, hemostatic efficacy, and handling characteristics of a thrombin-containing topical surgical hemostatic agent (a gelatin matrix) to a hemostatic gelatin sponge for treatment of parenchymal bleeding after liver biopsy. Fourteen dogs were enrolled in this prospective clinical study. Paired 1.5 cm × 1.5 cm and 0.5 cm deep liver biopsies were obtained via laparotomy for each dog. One bleeding liver biopsy lesion was treated with the gelatin matrix and the other with a gelatin sponge. The treated liver biopsy sites were compared for bleeding severity, time to hemostasis, cumulative blood loss, and hemostatic agent handling characteristics. Median time to hemostasis was significantly shorter (P = 0.034) and median cumulative blood loss was significantly lower (P = 0.033) for the lesions treated with the gelatin matrix than the gelatin sponge. Adverse reactions were not observed within the first 24 hr postoperatively. When used to control parenchymal bleeding from liver biopsy sites in the dog, the evaluated gelatin matrix was safe and more effective than the gelatin sponge.

Mechanically robust, negative-swelling, mussel-inspired tissue adhesives

Most synthetic polymer hydrogel tissue adhesives and sealants swell considerably in physiologic conditions, which can result in mechanical weakening and adverse medical complications. This paper describes the synthesis and characterization of mechanically tough zero- or negative-swelling mussel-inspired surgical adhesives based on catechol-modified amphiphilic poly(propylene oxide)-poly(ethylene oxide) block copolymers. The formation, swelling, bulk mechanical, and tissue adhesive properties of the resulting thermosensitive gels were characterized. Catechol oxidation at or below room temperature rapidly resulted in a chemically cross-linked network, with subsequent warming to physiological temperature inducing a thermal hydrophobic transition in the PPO domains and providing a mechanism for volumetric reduction and mechanical toughening. The described approach can be easily adapted for other thermally sensitive block copolymers and cross-linking strategies, representing a general approach that can be employed to control swelling and enhance mechanical properties of polymer hydrogels used in a medical context.

Fibrin-based tissue engineering: comparison of different methods of autologous fibrinogen isolation

OBJECTIVE

This study is focussed on the optimal method of autologous fibrinogen isolation with regard to the yield and the use as a scaffold material. This is particularly relevant for pediatric patients with strictly limited volumes of blood.

MATERIALS AND METHODS

The following isolation methods were evaluated: cryoprecipitation, ethanol (EtOH) precipitation, ammonium sulfate [(NH(4))(2)SO(4))] precipitation, ammonium sulfate precipitation combined with cryoprecipitation, and polyethylene glycol precipitation combined with cryoprecipitation. Fibrinogen yields were quantified spectrophotometrically and by electrophoretic analyses. To test the influence of the different isolation methods on the microstructure of the fibrin gels, scanning electron microscopy (SEM) was used and the mechanical strength of the cell-free and cell-seeded fibrin gels was tested by burst strength measurements. Cytotoxicity assays were performed to analyze the effect of various fibrinogen isolation methods on proliferation, apoptosis, and necrosis. Tissue development and cell migration were analyzed in all samples using immunohistochemical techniques. The synthesis of collagen as an extracellular matrix component by human umbilical cord artery smooth muscle cells in fibrin gels was measured using hydroxyproline assay.

RESULTS

Compared to cryoprecipitation, all other considered methods were superior in quantitative analyses, with maximum fibrinogen yields of ∼80% of total plasma fibrinogen concentration using ethanol precipitation. SEM imaging demonstrated minor differences in the gel microstructure. Ethanol-precipitated fibrin gels exhibited the best mechanical properties. None of the isolation methods had a cytotoxic effect on the cells. Collagen production was similar in all gels except those from ammonium sulfate precipitation. Histological analysis showed good cell compatibility for ethanol-precipitated gels.

CONCLUSION

The results of the present study demonstrated that ethanol precipitation is a simple and effective method for isolation of fibrinogen and a suitable alternative to cryoprecipitation. This technique allows minimization of the necessary blood volume for fibrinogen isolation, particularly important for pediatric applications, and also has no negative influence on microstructure, mechanical properties, cell proliferation, or tissue development.

Transplantation of mesenchymal stem cells to the brain by topical application in an experimental traumatic brain injury model

Mesenchymal stem cells (MSCs) have been shown in various animal models to be capable of neurorepair and neuroprotection. To carry out a therapeutic function, MSCs must be delivered to the target organ. MSCs are administered to patients via systemic infusion, which has many drawbacks, including a low engraftment rate and the migration of MSCs to non-target organs. However, other approaches such as direct intracerebral injection of MSCs might cause cerebral bleeding. In this study, a traumatic brain injury (TBI) was induced over the right parietal cerebral cortex in Sprague Dawley rats, and green fluorescent protein (GFP)-expressing MSCs (GFP-MSCs), together with a thin layer of fibrin, were applied to the external surface of the contralateral side 2 days later. Within 5 days of topical application, the GFP-MSCs had migrated from the site of application on the cortical surface, through the white matter, and had emerged at the cortical surface of the TBI site on the contralateral cerebral hemisphere, apparently following axons along the corpus callosum. In sham-injured control animals, the topically applied GFP-MSCs proliferated superficially on the cortex at the site of application, and no GFP-MSCs were found at the contralateral cortical surface. In all instances, GFP-MSCs were not detected in other organs of either the test or the control animals. Our study demonstrated that MSCs topically applied to the brain surface can migrate to a TBI site.

Platelet function in health and disease: from molecular mechanisms, redox considerations to novel therapeutic opportunities

Increased oxidative stress appears to be of fundamental importance in the pathogenesis and development of several disease processes. Indeed, it is well known that reactive oxygen species (ROS) exert critical regulatory functions within the vascular wall, and it is, therefore, plausible that platelets represent a relevant target for their action. Platelet activation cascade (including receptor-mediated tethering to the endothelium, rolling, firm adhesion, aggregation, and thrombus formation) is tightly regulated. In addition to already well-defined platelet regulatory factors, ROS may participate in the regulation of platelet activation. It is already established that enhanced ROS release from the vascular wall can indirectly affect platelet activity by scavenging nitric oxide (NO), thereby decreasing the antiplatelet properties of endothelium. On the other hand, recent data suggest that platelets themselves generate ROS, which may evoke pro-thrombotic responses, triggering many biological processes participating in atherosclerosis initiation, progression, and complication. That oxidative stress may alter platelet function is conceivable when considering that antioxidants play a role in the prevention of cardiovascular disease, although the precise mechanism accounting for changes attributable to antioxidants in atherosclerosis remains unknown. It is possible that the effects of antioxidants may be a consequence of their enhancing or promoting the antiplatelet effects of NO derived from both endothelial cells and platelets. This review focuses on current knowledge regarding ROS-dependent regulation of platelet function in health and disease, and summarizes in vitro and in vivo evidence for their physiological and potential therapeutic relevance.

Efficacy of fibrin sealant in reducing hemorrhage after a loop electrosurgical excision procedure

BACKGROUND/AIMS

We examined the association of fibrin sealant use with post-operative hemorrhage in patients who underwent a loop electrosurgical excision procedure (LEEP).

METHODS

We retrospectively collected clinicopathologic data of 344 patients who underwent LEEP at our institute between 2007 and 2009. We defined hemorrhage which occurred between 1 and 30 days after LEEP and required electrocautery to achieve hemostasis as severe secondary hemorrhage (SSH). We determined whether or not the use of fibrin sealant during LEEP was associated with a decreased occurrence of SSH. In addition, we examined the associations of other clinicopathologic variables with SSH and fibrin sealant use.

RESULTS

SSH occurred in 6 of 200 patients (3%) with fibrin sealant and in 12 of 144 patients (8%) without fibrin sealant. Based on univariate analysis, the use of fibrin sealant was associated with SSH (p = 0.028). However, age, surgeons and pathologic diagnosis were not associated with SSH. Based on multivariate analysis, the use of fibrin sealant was associated with less SSH (p = 0.033, OR = 0.328, 95% CI 0.117-0.917).

CONCLUSION

Fibrin sealant use reduces the incidence of severe post-operative hemorrhage after LEEP.

Sutureless sealing of penetrating corneal wounds using a laser-activated thin film adhesive

BACKGROUND AND OBJECTIVES

To demonstrate the feasibility of a novel, thin film, laser-activated adhesive in sealing penetrative corneal wounds with a view to replacing sutures in ophthalmic operations.

METHODS

A previously described thin film adhesive composed of chitosan and indocyanine green activated by infrared laser (808 nm) was used to seal penetrating corneal wounds ranging from 1 to 6 mm in size in enucleated bovine eyes. The excised corneas were subjected to pressure tests to evaluate the strength of the corneal repairs and compared to sutures and commercial fibrin glue, Tisseel®. Temperatures at the adhesive-tissue interface were measured and histological examinations of the repairs performed to investigate potential tissue damage. Biodegradability of the films was monitored in lysozyme solutions at concentrations reported in tears.

RESULTS

The adhesive effectively sealed corneal wounds, withstanding pressures of 140-320 mmHg, far in excess of the normal intraocular pressure. In contrast, pressures of 40-80 mm Hg were determined using a combination of sutures with Tisseel® as a sealant. The laser-activation process was 1.5-5 times faster than other procedures studied and required no curing time. A transient, mean temperature of 56 ± 2°C was measured at the adhesive-tissue interface while histology showed no tissue damage as a consequence of the irradiation process. Irradiation had no significant influence on adhesive biodegradation in vitro, which lost approximately 30% of their initial weight in a lysozyme solution (6 mg ml(-1)).

CONCLUSIONS

The thin film adhesive was found to be an effective in sealing corneal wounds with considerable advantages over sutures, including speed of application and sealing strength and biodegradability.

The evaluation of fibrin sealants and tissue adhesives in oral surgery among patients with bleeding disorders

OBJECTIVE

The aim of this study was to evaluate the efficiency of two local hemostatic agents administered with apreoperative dose of replacement therapy in patients with bleeding disorders undergoing oral surgery.

MATERIAL AND METHODS

The study included 21 patients that were randomly divided into 3 groups. Patients in Group1 (n = 7) received preoperative replacement therapy and postoperative fibrin sealant applied to the surgical site. Patientsin Group 2 (n = 7) received preoperative replacement therapy and postoperative tissue adhesive applied to the surgicalsite. Patients in Group 3 (n = 7) were given replacement therapy pre- and postoperatively.

RESULTS

Postoperative bleeding was not observed in 17 of the 21 patients, including 5 in Group 1 (71.42%), 6 in Group2 (85.71%), and 6 in Group 3 (85.71%). Hemorrhagic complications occurred in only 4 of the 21 patients.

CONCLUSION

The use of fibrin sealant and tissue adhesive was beneficial, as they reduced the level of factor concentratesused for replacement therapy and resulted in rapid hemostasis at the surgical site, facilitating the ability to performserial surgical procedures concurrently.

Cross-Reactivity of Various Thrombin Products With Anti-Rabbit Antibodies to Bovine, Human, and Recombinant Thrombin

JMI-thrombin is used as topical hemostatic agent. While earlier clinically available JMI were reported to produce immunologic responses upon repeated exposure, the improved JMI, Recothrom?, and Evithrom? are claimed to be less immunogenic. Recothrom, despite its reduced immunogenic nature, upon repeated administration may result in the generation of antibodies (Abs) and that may cross react with bovine and human thrombin. Therefore, groups of rabbits were challenged repeatedly with Recothrom, Evithrom, and JMI over a 9-month period. Pre-immune blood and antiserum were collected from each rabbit on different time point. To determine their relative cross reactivity, JMI, Recothrom, and Evithrom were evaluated by western blotting using the rabbit IgG fractions. The results suggest that anti-Recothrom Abs cross-react with Evithrom and JMI in a time dependent fashion. Anti-JMI Abs did not cross-react with Recothrom, and Evithrom. Also, anti-Evithrom did not show any cross-reactivity with Recothrom and JMI at any time.

Incorporation of exudates of human platelet-rich fibrin gel in biodegradable fibrin scaffolds for tissue engineering of cartilage

The goal of this study was to assess the incorporation of exudates of human platelet-rich fibrin (hPRF) that is abundant in platelet cytokines and growth factors into biodegradable fibrin (FB) scaffolds as a regeneration matrix for promoting chondrocyte proliferation and re-differentiation. hPRF was obtained from human blood by centrifugation without an anticoagulant, and the exudate of hPRF was collected and mixed with bovine fibrinogen, and then thrombin was added to form the FB scaffold. Proliferation and differentiation of human primary chondrocytes and a human chondrosarcoma cell line, the SW-1353, embedded in the three-dimensional (3D) scaffolds and on the two-dimensional (2D) surface of the FB scaffolds so produced were evaluated in comparison with an agarose (AG) scaffold serving as the control. Results demonstrated that the amounts of these cytokines and growth factors in hPRF exudates were higher than those in the blood-derived products except for TGF-β1. Chondrocytes and SW1353 cells on the 2D and 3D FB scaffolds with the addition of the exudates of PRF exhibited more-available proliferation and differentiation than cells on 2D and 3D FB and AG scaffolds. It was concluded that FB scaffolds can provide an appropriate environment for chondrocyte proliferation and re-differentiation, and it could be improved by adding exudates of hPRF. These 3D scaffolds have great promise for cartilage tissue engineering.

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.

Allogeneic single-donor cryoseal produced from fresh-frozen quarantine apheresis plasma as alternative for multidonor or autologous fibrin sealants

BACKGROUND

Fibrin sealant is a human blood product consisting of two components: cryoprecipitate and thrombin. Commercial fibrin sealants are produced from multidonors, increasing the viral risk, and contain fibrinolytic inhibitors such as tranexamic acid or bovine aprotinin. Autologous fibrin sealants reduce the viral risk and are mostly produced during a surgical procedure or well in advance. Alternatively, the allogeneic single-donor fibrin sealant cryoseal can be used. In this study cryoseal was characterized and the manufacturing consistency of the production process was investigated.

STUDY DESIGN AND METHODS

Cryoseal was produced from plasma collected on apheresis machines using a commercial device. In a research setting the protein composition and recovery were determined. Also, the manufacturing consistency of the production process was tested in a research setting as well as in a routine setting.

RESULTS

In the research setting all produced cryoseal met the quality control requirements of a clotting time of less than 10 seconds and the presence of Factor (F)XIII (qualitative). In the routine setting, one procedure per year did not meet these requirements. The protein composition showed the following mean ± standard deviation (%recovery) results: thrombin 25.7 ± 11.1 IU/mL, fibrinogen 19.9 ± 4.6 (15%) mg/mL, FVIII 15.6 ± 5.4 (44%) IU/mL, FXIII 2.7 ± 0.7 (6%) IU/mL, and plasminogen 1.8 ± 0.2 (4%) U/mL. In both research and routine settings the production process resulted in a consistent product.

CONCLUSION

The cryoseal manufacturing process resulted in a consistent product, which meets the predetermined specifications. The single-donor origin and the absence of fibrinolytic inhibitors make cryoseal a good alternative for multidonor and autologous fibrin sealants.

Evolution of hemostatic agents in surgical practice

Objective:

Topical hemostatic agents are used in a wide variety of surgical settings, and the evolution of this class of surgical tools is an interesting topic. We reviewed and outlined the historical progress of topical hemostats into present day surgery and urology, and highlight opportunities for future research.

Materials and Methods:

A MEDLINE search of all available literature concerning several classes of topical hemostatic agents was performed. Fibrins sealants, Gelatin sponge hemostatics, cyanoacrylate adhesives, oxidized regenerated cellulose, and microfibrillar collagen were included. References were chosen from a broad range of surgical literature.

Results:

Topical hemostatic agents have historically taken advantage of a wide variety of mechanisms for hemostasis. Fibrin sealants have a rich history and large potential for further applications. Gelatin sponge hemostatics have been widely used since their introduction, but have changed little. Cyanoacrylate adhesives have a unique mechanism and opportunity for novel applications of existing products. Oxidized cellulose was original in the use of plant-based components. Microfibrillar collagen hemostats have evolved to a wide variety of formats.

Conclusions:

A review of the evolution of topical hemostatic agents highlights opportunities for potential novel research. Fibrin sealants may have the most opportunity for advancement, and understanding the history of these products is useful. With the drive in urology for minimally invasive surgical techniques, adaptation of topical hemostatic agents to this surgical approach would be valuable and offers an opportunity for novel contributions.

Clinical use of topical thrombin as a surgical hemostat

When surgical ligation of bleeding fails, or is not possible, surgeons rely on a number of hemostatic aids, including thrombin. This review discusses the history, pharmacology and clinical application of thrombin as a surgical hemostat. The initial thrombin was bovine in origin, but its use has been complicated by the formation of antibodies that cross react with human coagulation factors. This has been associated with life threatening bleeding and in some circumstances anaphylaxis and death. Human thrombin, isolated from pooled plasma of donors, has been developed in an effort to minimize these risks, but its downside is the potential of transmitting blood-borne pathogens and limited availability. Recently a recombinant thrombin has been developed and approved for use by the FDA. It has the advantage of being minimally antigenic and devoid of the risk if viral transmission. Thrombin is often used in conjunction with other hemostatic aids, including absorbable agents (like gelfoam, collagen, and cellulose), and with fibrinogen in fibrin glues. The last part of this review will discuss these agents in detail, and review their clinical applications.

Isocyanate-functional adhesives for biomedical applications. Biocompatibility and feasibility study for vascular closure applications

Biodegradable isocyanate-functional adhesives based on poly(ethylene glycol)-adipic acid esters were synthesized, characterized, and evaluated in vitro and in vivo. Two types of formulations, P2TT and P2MT, were developed by functionalization with 2,4-tolylene diisocyanate (TDI) or 4,4'-methylene-bis(phenyl isocyanate) (MDI), respectively, and branching with 1,1,1-trimethylolpropane (TMP). The biocompatibility of the synthesized adhesive formulations was evaluated as per ISO 10993. Cytotoxicity, systemic toxicity, pyrogenicity, genotoxicity (reverse mutation of Salmonella typhimurium and Escherichia coli), hemolysis, intracutaneous reactivity, and delayed-type hypersensitivity were evaluated. All formulations met the requirements of the conducted standard tests. The biological behavior and ability of the adhesive formulations to close an arteriotomy and withstand arterial pressure following partial approximation with a single suture were evaluated in a rat abdominal aorta model. Animals were evaluated at 1, 2, 3, and 4 weeks after surgery. Macroscopic and histopathologic evaluation of explanted arteries suggested that the P2TT formulation had better in vivo performance than the P2MT formulation. Additionally, the P2TT formulation resulted in less tissue reaction than P2MT formulation. To our knowledge, this is the first study demonstrating the potential of this new class of isocyanate-functional degradable adhesives for vascular applications.