Estimating the pathogen safety of manufactured human plasma products: application to fibrin sealants and to thrombin

A method to screen and evaluate tissue adhesives for joint repair applications

BACKGROUND

Tissue adhesives are useful means for various medical procedures. Since varying requirements cause that a single adhesive cannot meet all needs, bond strength testing remains one of the key applications used to screen for new products and study the influence of experimental variables. This study was conducted to develop an easy to use method to screen and evaluate tissue adhesives for tissue engineering applications.

METHOD

Tissue grips were designed to facilitate the reproducible production of substrate tissue and adhesive strength measurements in universal testing machines. Porcine femoral condyles were used to generate osteochondral test tissue cylinders (substrates) of different shapes. Viability of substrates was tested using PI/FDA staining. Self-bonding properties were determined to examine reusability of substrates (n = 3). Serial measurements (n = 5) in different operation modes (OM) were performed to analyze the bonding strength of tissue adhesives in bone (OM-1) and cartilage tissue either in isolation (OM-2) or under specific requirements in joint repair such as filling cartilage defects with clinical applied fibrin/PLGA-cell-transplants (OM-3) or tissues (OM-4). The efficiency of the method was determined on the basis of adhesive properties of fibrin glue for different assembly times (30 s, 60 s). Seven randomly generated collagen formulations were analyzed to examine the potential of method to identify new tissue adhesives.

RESULTS

Viability analysis of test tissue cylinders revealed vital cells (>80%) in cartilage components even 48 h post preparation. Reuse (n = 10) of test substrate did not significantly change adhesive characteristics. Adhesive strength of fibrin varied in different test settings (OM-1: 7.1 kPa, OM-2: 2.6 kPa, OM-3: 32.7 kPa, OM-4: 30.1 kPa) and was increasing with assembly time on average (2.4-fold). The screening of the different collagen formulations revealed a substance with significant higher adhesive strength on cartilage (14.8 kPa) and bone tissue (11.8 kPa) compared to fibrin and also considerable adhesive properties when filling defects with cartilage tissue (23.2 kPa).

CONCLUSION

The method confirmed adhesive properties of fibrin and demonstrated the dependence of adhesive properties and applied settings. Furthermore the method was suitable to screen for potential adhesives and to identify a promising candidate for cartilage and bone applications. The method can offer simple, replicable and efficient evaluation of adhesive properties in ex vivo specimens and may be a useful supplement to existing methods in clinical relevant settings.

Biochemical, mechanical, and morphological properties of a completely autologous platelet-rich wound sealant

The optimal composition of fibrin sealant preparations is not known. We, therefore, sought to construct a series of sealants from autologous components and compare their functioning to Bioseal a commonly used sealant. Characteristics of the platelet-rich plasma, cryoprecipitate, and thrombin were determined and compared to commercial glue from composition, function, and microscopy aspects. The concentrations of platelets as well as fibronectin in autologous fibrin glues were significantly higher than those in commercial ones (P < 0.001). Mechanical values (maximum amplitude and clot strength) obtained from thrombelastograph assays in two groups were not significantly different (P > 0.05). A dense platelet surface and fibrin net structures could be observed in the autologous samples, whereas there were only sparse fibrin nets without cellular components in Bioseal. Characterization of autologous and Bioseal fibrin sealants and their performance do not have significant difference in biochemical and mechanical properties. The entirely autologous platelet-rich gel in the present study may get wide application in future practice after confirmation of its safety, efficiency, and economic benefits.

Efficacy and safety of fibrin sealant for tissue adherence in facial rhytidectomy

The purpose of this review is to clarify the present use of fibrin sealant in rhyditectomy procedures and help maximize the appropriate and safe application of this material. A set of terms and definitions for hemostats, sealants, and adhesives based on group, category, and class will be employed to highlight the specific capabilities of fibrin sealant. Fibrin sealant has now emerged as an example of maximizing the usefulness of a surgical agent and is the only product with Food and Drug Administration approval in all three groupings: hemostats; sealants; and adhesives. A variety of manufacturers’ fibrin sealant products are available including multiple liquids and one patch. A single liquid product is now specifically indicated for skin flap adherence during rhytidectomy. The unique characteristic of this particular two component fibrin sealant adhesive agent is its slower polymerization rate as a result of a low thrombin concentration which when combined with fibrinogen permits adequate time for manipulation of flaps and tissues prior to final fixation. In addition to its flap adherence and potential space elimination capability, fibrin sealant is also an excellent blood clotting agent and can seal tissues to prevent lymphatic leak or serous fluid accumulation. Thus, it is almost ideally suited to reduce the occurrence of fluid accumulation, hematomas, ecchymoses, and swelling, as well as to possibly eliminate the need for drains following rhytidectomy. A literature review of fibrin sealant in rhytidectomy is included to help define the current state of its clinical use. The author’s recommendations for the best use of this material during facial procedures are also provided.

TachoSil use in abdominal surgery: a review

The success of any surgical procedure is based on adequate hemostasis. Many different biomaterial products can be used to achieve that aim. The products that can be used during surgery may be classified as topical hemostats, sealants, and adhesives. Hemostats can clot blood. Sealants can create sealing barriers. Adhesives bond tissue together. Collagen, gelatin, and cellulose are hemostat agents. TachoSil(®) is a development of TachoComb(®) and TachoComb(®) H. TachoComb is made with equine collagen, bovine thrombin, bovine aprotinin, and human fibrinogen. The clinical efficacy of TachoSil was shown firstly by a clinical study of hepatic surgery. In the study, TachoSil proved to be superior to argon beamer in obtaining effective and fast intraoperative hemostasis. Following the study, many applications in different fields of surgery have been reported in the literature. The use of TachoSil in open abdominal surgery and its relevant results have encouraged the use of TachoSil in laparoscopic surgery. Unfortunately, its use in laparoscopy has not become as popular as it is in open surgery, due to a lack of efficacious techniques. Immunologic reactions to compounds of TachoSil and the transmission of infectious diseases are two major risks concerning topical hemostasis. Even though the risk of severe immunologic reactions to bovine material is low, TachoSil has gradually replaced all bovine material with material of human origin and has therefore eliminated the associated risks of bovine material. TachoSil has a good satisfaction rate among surgeons and reduces both the operating time for patients and the time spent in intensive care units.

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.

TachoSil use in abdominal surgery: a review

The success of any surgical procedure is based on adequate hemostasis. Many different biomaterial products can be used to achieve that aim. The products that can be used during surgery may be classified as topical hemostats, sealants, and adhesives. Hemostats can clot blood. Sealants can create sealing barriers. Adhesives bond tissue together. Collagen, gelatin, and cellulose are hemostat agents. TachoSil(®) is a development of TachoComb(®) and TachoComb(®) H. TachoComb is made with equine collagen, bovine thrombin, bovine aprotinin, and human fibrinogen. The clinical efficacy of TachoSil was shown firstly by a clinical study of hepatic surgery. In the study, TachoSil proved to be superior to argon beamer in obtaining effective and fast intraoperative hemostasis. Following the study, many applications in different fields of surgery have been reported in the literature. The use of TachoSil in open abdominal surgery and its relevant results have encouraged the use of TachoSil in laparoscopic surgery. Unfortunately, its use in laparoscopy has not become as popular as it is in open surgery, due to a lack of efficacious techniques. Immunologic reactions to compounds of TachoSil and the transmission of infectious diseases are two major risks concerning topical hemostasis. Even though the risk of severe immunologic reactions to bovine material is low, TachoSil has gradually replaced all bovine material with material of human origin and has therefore eliminated the associated risks of bovine material. TachoSil has a good satisfaction rate among surgeons and reduces both the operating time for patients and the time spent in intensive care units.

The Use of Solvent/Detergent Treatment in Pathogen Reduction of Plasma

The solvent/detergent (SD) process used for plasma can safely inactivate all lipid-enveloped viruses. The introduction of a specific prion-binding ligand gel in combination with SD treatment, time-reduced from 4 to 1-1.5 h, still ensures efficient virus kill, reduces abnormal prion protein by >5 log steps, and preserves levels of plasmin inhibitor at close to the reference range. Infections with known non-enveloped viruses such as HAV or parvovirus B19 are prevented by ensuring low virus loads in the starting plasma units, dilution through pooling of single plasma units, and neutralization of immune antibodies already present in the initial plasma pools. The major advantages of SD plasma over fresh frozen plasma and the other pathogen-inactivated plasmas are its extreme safety with respect to transfusion-related acute lung injury and the significantly lower likelihood of provoking allergic reactions. Both advantages are best interpreted as results of the dilution effect of pooling. No fewer than 18 clinical studies covering all indications for plasma, and extensive clinical experience have shown that reduced levels of coagulation factors and inhibitors as a result of SD treatment do not impair significantly the clinical efficacy or tolerance of plasma. Properly standardized clotting factor and inhibitor potencies and low batch-to-batch variations when compared with single-donor plasma units makes SD plasma more suitable for standardized treatment.

Defining "adequate" pathogen reduction performance for transfused blood components

Pathogen reduction of labile blood products offers the opportunity to introduce to the blood banking community the same mechanism of protection that is employed for fractionated or pooled plasma products today--blood components that have been treated with methods to inactivate or reduce the infectivity of a variety of organisms that may contaminate donated blood and thus potentially transmit infection via transfusion. Due to the mechanisms of action, the methods employed in the plasma fractionation environment are not directly applicable to labile blood products. This article examines whether the same criteria of performance required for plasma derivatives (i.e., 6 log/mL reduction by multiple orthogonal methods) should be applied to the treatment of labile components and if not what criteria for performance might be sufficient. In conducting this analysis, we have considered what has been learned in the past several decades regarding the dynamics and infectivity of various pathogens and disease transmission by blood products, the introduction and progressive enhancement of testing methods based on serology and nucleic acid testing, and the performance characteristics for pathogen reduction technologies that are available today.

European guideline for the management of hepatitis B and C virus infections, 2010

These are the guidelines on hepatitis B and C management for IUSTI/WHO in Europe, 2010. They describe the epidemiology, diagnosis, clinical features, treatment and prevention of hepatitis B and C with particular reference to sexual health clinical practice.

The use of fibrin glue in surgery of the knee

Fibrin glue, also known as fibrin sealant, is now established as a haemostatic agent in surgery, but its role in orthopaedic surgery is neither well known nor clearly defined. Although it was originally used over 100 years ago, concerns about transmission of disease meant that it fell from favour. It is also available as a slow-release drug delivery system and as a substrate for cellular growth and tissue engineering. Consequently, it has the potential to be used in a number of ways in orthopaedic surgery. The purpose of this review is to address its use in surgery of the knee in which it appears to offer great promise.

Topical thrombins: benefits and risks

Whether from surgical misadventure, inherent patient factors, or iatrogenic causes, postoperative bleeding can be a consequence of any surgical procedure. There are many methods and products available to assist in managing or preventing bleeding. For each method, there may be specific benefits and indications, but they may also carry some degree of risk. Topical thrombin is used extensively in many surgical specialties, especially in the cardiovascular and neurosurgical arenas where other hemostatic modalities may not be appropriate choices. As a class, topical thrombins are generally a safe and effective method for achieving intraoperative hemostasis; however, some members of the class carry associated risks with their use. For example, the United States Food and Drug Administration required the addition of a black-box warning to the prescribing information of bovine-derived thrombin, the oldest member of the class, due to concerns of immune-mediated coagulopathies developing after use. In addition, human thrombin derived from pooled plasma has its own, if theoretical, risk of transmitting infections due to viral or prion agents. We address the topical thrombin class and review each product in the context of the current literature.

A newly identified bocavirus species in human stool

Viral metagenomic analysis was used to identify a previously uncharacterized parvovirus species, "HBoV2," whose closest phylogenetic relative is the human bocavirus (HBoV). HBoV2 has a genomic organization identical to that of HBoV but has only 78%, 67%, and 80% identity, respectively, with the latter's NS1, NP1, and VP1/VP2 proteins. The study used polymerase chain reaction to detect HBoV2 sequences in 5 of 98 stool samples from Pakistani children and in 3 of 699 stool samples from Edinburgh. Nearly-full-length genome sequencing revealed the presence of 3 HBoV2 genotypes and evidence of recombination between genotypes. Further studies are necessary to identify anatomical sites of HBoV2 replication and potential associations with clinical symptoms or disease.