Modulation of mechanical properties in multiple-component tissue adhesives.

In vitro, ex vivo, and in vivo studies were performed to investigate the effect of mixing upon the mechanical properties of a two-component tissue adhesive. The hypothesis investigated was that a more complete mixing of the two components would yield an increase in the mechanical performance of the adhesive. This in turn would be demonstrated by improved outcomes in models of clinical sealant application. In vitro stereological analysis of tissue adhesive mixed and delivered by several different applicators demonstrated variation in the amount of mixing provided by each type of delivery system. Ex vivo tensile adhesive strength showed that there was a correlation between the amount of mixing and bonding strength; that is, more thorough mixing demonstrated higher adhesive strength. No significant difference was seen, however, between the different applicator types and impact on in vivo dermal incisional closure strength. There was a correlation, though, in amount of mixing and in vivo hemostasis. In a rabbit spleen incision model, a more thoroughly mixed sealant corresponded with a decrease in time to obtain complete hemostasis, as well as less sealant used. The effects of mixing on tissue-adhesive mechanical performance were influenced somewhat by the amount of mixing provided by the applicator. This effect, however, was dependent upon the sealant formulation and the type of in vivo application.

Functional recovery of transected nerves treated with systemic BDNF and CNTF.

The purpose of this study was to investigate the effect of systemic co-injections of ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) on the functional recovery of transected sciatic nerves repaired by epineurial coaptation (EC) or collagen tubulization (CT). Forty Sprague-Dawley rats underwent transection of their sciatic nerves and repair by either EC or CT. With each repair technique, systemic injections of neurotrophic factors or control injections of lactated Ringer's solution were given. This resulted in four treatment groups: EC, EC + BDNF/CNTF, CT, and CT + BDNF/CNTF. Nerve function was assessed using sciatic functional indices (SFI). Animals whose nerves were repaired by CT (P = 0.01), CT + BDNF/CNTF (P = 0.04), and EC + BDNF/CNTF (P = 0.04) all had better functional recovery than those whose nerves were repaired by EC. There were no significant differences among these three groups, however. Animals in the CT group manifested the most rapid rate of recovery (P = 0.02 compared with EC). Collagen tubulization and systemic co-injections of BDNF/CNTF improve the rate and extent of sciatic functional recovery after nerve repair. The improvement in recovery conferred is not additive.

Skull base cerebrospinal fluid leakage control with a fibrin-based composite tissue adhesive.

Cerebrospinal fluid (CSF) leaks can be responsible for significant patient morbidity and mortality. While the majority of leaks induced after head trauma will seal without intervention, spontaneous or surgically-induced leaks often require operative repair. Many modifications on standard surgical technique are available for repair of CSF fistulae, but none assures adequate closure. We have studied the efficacy of a novel fibrin-based composite tissue adhesive (CTA) for closure of experimentally-induced CSF leaks in rats. Fistulae were created in two groups of animals. Two weeks after creation of the leaks, the animals were sacrificed and analyzed for persistence of leak. A 58% leakage rate was noted in the control group (n = 12), and no leaks were noted in the experimental group closed after application of CTA to the surgical defect followed by skin closure (n = 11). Comparing the control group to the experimental group, results were statistically significant (p = 0.015). These data suggest that CTA may be effective as an adjunct for the closure of CSF fistulae.

Fibrin sealant adhesive systems: a review of their chemistry, material properties and clinical applications.

Fibrin sealants (FS) are the most successful tissue adhesives to date. They have many advantages over adhesive technologies such as cyanoacrylates and marine adhesives in terms of biocompatibility, biodegradation and hemostasis. There are several commercial products in Europe but none in the United States due to the current regulatory stance against pooled plasma blood products. Blood banks and interested investigators have implemented single- and patient autologous-donor production methods with some success. This article will review the history of FS research and development and describe the chemistry of fibrin(ogen) and the production of commercial and research products. Fibrin sealant and purified fibrin characterization is compared and contrasted. The material and adhesive properties are described, and a survey of the clinical applications in which FS has been used is included as well.

A method to determine shear adhesive strength of fibrin sealants.

The adhesive strength of fibrin sealants has not been rigorously evaluated to date. The adhesive strength of six different concentrations of cryoprecipitated fibrinogen as well as the commercially available fibrin tissue adhesive Tissucol was tested under controlled conditions utilizing split-thickness skin grafts as the test adherand. This test configuration permitted the modeling of bonding strength for attachment of skin grafts as well as incorporate established engineering test standards for adhesives. An increase in fibrin concentration corresponded with an increase in shear adhesive strength. No significant increases in adhesive strength were attained after 5 min of bonding for all tested concentrations, except for the commercial adhesive, which attained the adhesive strength of an equivalent concentration of cryoprecipitated adhesive after 90 min. The adhesive strength, however, was an order of magnitude less than reported values of the tensile strength of fibrin material for similar concentrations. Therefore, it is important that the surgeon use a sufficiently high fibrinogen concentration for the specific clinical indication. The method of fibrin sealant preparation and/or the compounding adjuncts appear to have an effect on the development of adhesive strength.

The use of fibrin glue in intracranial procedures: preliminary results.

Intracranial procedures always have the potential of cerebrospinal fluid (CSF) leakage postoperatively. Sealing all routes of CSF drainage to the outside of the intracranial contents is essential. This is usually achieved with muscle and fat plugs, homograft dura, fascia, and suture. The use of a fibrin glue might affect and lessen the likelihood of a CSF leak. Eight clinical cases of various intracranial procedures using a simple, two-part patient autologous cryoprecipitate fibrinogen and bovine thrombin glue are described. Preliminary results of up to 1 year show no CSF leakage nor adverse reactions to the fibrin glue. The production method and material characteristics are briefly compared with other currently described autologous fibrin glue formulations. This version is similar in strength to other formulations, yet is simpler and more convenient to produce. The use of this autologous fibrin glue appears to provide an adjunct to commonly employed packing techniques in a convenient and effective manner. With more experience, fibrin glue might become an even more important tool in intracranial procedures.