Assessment of the Retinal Toxicity and Sealing Strength of Tissue Adhesives.

PURPOSE: The purpose of this in vitro prospective nonrandomized study is to compare the toxicity and strength of cyanoacrylate and hydrogel adhesives on human retinal pigment epithelium (RPE) cells and porcine retina, respectively. METHODS: The toxicity of cyanoacrylate (histoacryl, dermabond, superglue), ReSure PEG, and Tisseel fibrin glue on human RPE cells was determined by growing RPE cells in vitro, applying the different adhesives to the cells, and monitoring for disruption of growth over 3 days. The relative strength of these adhesives was tested by gluing a 3 mm piece of foam to a porcine retina and determining the amount of force needed to break the attachment. RESULTS: 0.085 N of force was required to break the porcine retinal tissue (p = .913). Histoacryl adhesive exhibited high strength (0.247 N) and high RPE toxicity (0.55 mm inhibition zone after 24 hrs). The strength of Tisseel fibrin glue was 0.078 N while that of ReSure was only 0.053 N. Both Tisseel and ReSure were nontoxic to the RPE cells. CONCLUSIONS: Tisseel VH fibrin sealant may provide the best option for sealing retinal breaks because of its high strength and low retinal toxicity.

Transgenic human embryonic stem cells overexpressing FGF2 stimulate neuroprotection following spinal cord ventral root avulsion.

Ventral root avulsion (VRA) triggers a strong glial reaction which contributes to neuronal loss, as well as to synaptic detachment. To overcome the degenerative effects of VRA, treatments with neurotrophic factors and stem cells have been proposed. Thus, we investigated neuroprotection elicited by human embryonic stem cells (hESC), modified to overexpress a human fibroblast growth factor 2 (FGF-2), on motoneurons subjected to VRA. Lewis rats were submitted to VRA (L4-L6) and hESC/FGF-2 were applied to the injury site using a fibrin scaffold. The spinal cords were processed to evaluate neuronal survival, synaptic stability, and glial reactivity two weeks post lesion. Then, qRT-PCR was used to assess gene expression of ß2-microglobulin (ß2m), TNFα, IL1ß, IL6 and IL10 in the spinal cord in vivo and FGF2 mRNA levels in hESC in vitro. The results indicate that hESC overexpressing FGF2 significantly rescued avulsed motoneurons, preserving synaptic covering and reducing astroglial reactivity. The cells were also shown to express BDNF and GDNF at the site of injury. Additionally, engraftment of hESC led to a significant reduction in mRNA levels of TNFα at the spinal cord ventral horn, indicating their immunomodulatory properties. Overall, the present data suggest that hESC overexpressing FGF2 are neuroprotective and can shift gene expression towards an anti-inflammatory environment.

Comparison between self-assembling peptide nanofiber scaffold (SAPNS) and fibrin sealant in neurosurgical hemostasis.

RADA16-I is a synthetic type I self-assembling peptide nanofiber scaffold (SAPNS) which may serve as a novel biocompatible hemostatic agent. Its application in neurosurgical hemostasis, however, has not been explored. Although RADA16-I is nontoxic and nonimmunogenic, its intrinsic acidity may potentially provoke inflammation in the surgically injured brain. We conducted an animal study to compare RADA16-I with fibrin sealant, a commonly used agent, with the hypothesis that the former would be a comparable alternative. Using a standardized surgical brain injury model, 30 Sprague-Dawley rats were randomized into three treatment groups: RADA16-I, fibrin sealant or gelatin sponge (control). Animals were sacrificed on day 3 and 42. Astrocytic and microglial infiltrations within the cerebral parenchyma adjacent to the operative site were significantly lower in the RADA16-I and fibrin sealant groups than control. RADA16-I did not cause more cellular inflammatory response despite its acidity when compared with fibrin sealant. Immunohistochemical studies showed infiltration by astrocytes and microglia into the fibrin sealant and RADA16-I grafts, suggesting their potential uses as tissue scaffolds. RADA16-I is a promising candidate for further translational and clinical studies that focus on its applications as a safe and effective hemostat, proregenerative nanofiber scaffold as well as drug and cell carrier.

Comparison of synthetic glues and 10-0 nylon in rabbit lamellar keratoplasty.

PURPOSES: To evaluate changes in mean keratometry and to compare wound repair with corneal lamellar grafts in rabbit eyes using human synthetic tissue adhesives and 10-0 nylon. METHODS: Corneal grafts were made using a 6.0-mm-diameter trephine and blades in the eyes of 15 New Zealand white rabbits. Human fibrin tissue adhesive (Tisseel) was used in group 1, human fibrin tissue adhesive (Beriplast P) was used in group 2, polyethylene glycol adhesive (Coseal) was used in group 3, and 8 bite sutures with 10-0 nylon were used in group 4 (control) for lamellar keratoplasty. Four bite sutures were made with 10-0 nylon in groups 1, 2, and 3. Slit-lamp microscopy and keratometry were performed at 3 days and 1, 2, and 4 weeks after the surgery. Histopathologic and electromicroscopic examinations were performed 4 weeks after the surgery. RESULTS: No inflammation or corneal toxicity was seen in groups 1 and 2. Histologically, a few inflammatory cells were seen in groups 3 and 4. Groups 1, 2, and 3 showed no statistically significant changes in mean keratometry at 4 weeks postoperatively compared with preoperative mean keratometry (Wilcoxon signed-rank test, P = 0.178, 0.208, and 0.889, respectively). The control group showed significant changes in mean keratometry at 4 weeks postoperatively (Wilcoxon signed-rank test, P = 0.018). CONCLUSIONS: Human fibrin tissue adhesives were well tolerated in rabbit eyes, with no apparent corneal toxicity. Polyethylene glycol adhesive showed more inflammation and insufficient wound repair compared with human fibrin tissue adhesives. Therefore, human fibrin tissue adhesives can be used as an alternative to sutures in lamellar keratoplasty.

Analysis of mitochondrial DNA damage using 8-hydroxy 2'deoxyguanosine on in vitro and in vivo exposure of biomaterials.

The present study was carried out to evaluate the effect of HAP-EVA, fibrin glue, HA-BG, Latex and Dental material on oxidative stress related mtDNA damage by in vitro and in vivo methods. In vivo studies of these biomaterials were carried out by implanting biomaterials (five materials) on animals for period of 1, 4, 12, 26 and 52 weeks. At the end of observations, animals were anesthetized, sacrificed and tissues surrounding the implanted materials were collected. Brain, bone and muscles were used for the extraction of mtDNA. Similarly mtDNA was extracted from the homogenate of fresh brain, bone and muscles on exposure to the physiological saline extract of all the above five biomaterials (In vitro). The extracted mtDNA were subjected to analyse the presence of 8-OHdG. The results of study indicated that there was no significant increase in the level of 8-OHdG and thereby does not influence on the GC-TA transversions.

A comparison of a cyanoacrylate [corrected] glue (Glubran) vs. fibrin sealant (Tisseel) in experimental models of partial pulmonary resection and lung incision [corrected] in rabbits.

INTRODUCTION: Bronchopleural fistulas (BPF) and air leaks (AL) present major complications after pulmonary resection. Various tissue sealants have been proposed for their prevention, e.g., fibrin sealant (FS) and cyanoacrylate glues (CA). Contrary to the safety record of FS, substantial side effects such as foreign body reaction and impaired tissue integration have been reported for CA. This study compares the sealing efficacy and biocompatibility as well as side effects of FS and CA in experimental partial pulmonary resection and lung incision in rabbits. METHODS: 26 New Zealand white rabbits (3 kg) were randomized to one of the three groups: partial pulmonary resection (A, acute model; n = 7 FS/ 7CA), lung incision [2 (B; n = 3 FS/ 3 CA)], and 14-day observation period (C; n = 3 FS/ 3 CA). In all groups (A, B, and C), FS was considered as control and CA as treatment. Surgery was carried out in general anaesthesia and mechanical ventilation. For partial lung resection a median thoracotomy was performed and the apex of the left median lobe was resected and the parenchymal surface covered with 0.09 ml of FS and CA. The thoracic cavity was filled with ringer solution after 5 minutes. The inspiratory minute volume (IMV) was increased by 0.02 l after every 4th inspiration. In groups B and C, a left lateral thoracotomy was performed in the 4th intercostal space and the left median lobe was incised with a scalpel. The incision was covered with 0.5 ml of FS or CA. At autopsy (B and C) the operation site was assessed macroscopically. Histology was performed in all animals. RESULTS: In terms of sealing purposes, FS and CA yielded comparable results in all groups. CA elicited a substantial increase of tissue temperature in the acute phase immediately after application (A). After 14 days CA residues were found, whereas FS was completely degraded. Histology showed a pronounced inflammatory response to CA but not to FS. We conclude that although the effect of airtight sealing was equally satisfying, our results emphasize that FS is preferable to CA for the prevention of BPF and AL due to superior biocompatibility and degradability. Longterm effects of CA residues on pulmonary tissue require further experimental testing.

In vivo and in vitro study of suprachoroidal fibrin glue.

PURPOSE: The suprachoroidal space is preferred for many reasons for implantation of retinal prostheses or drug delivery systems. This study aimed to investigate the safety and feasibility of suprachoroidal fibrin glue (FG), one of the adhesives used to fix the implanted material. METHODS: Human retinal pigment epithelium cells (hRPE) were cultured with FG, assayed with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, and studied by transmission electron microscopy. A total of 48 rabbits were randomly divided into three groups to undergo surgery: group 1, 0.1 ml suprachoroidal FG; group 2, 0.1 ml suprachoroidal normal saline (control); group 3, 0.1 ml intravitreal FG. Slit-lamp examination, indirect ophthalmoscopy, fundus photography, fundus fluorescein angiography (FFA), indocyanine green angiography (IA), electroretinography (ERG), and histopathological examination were performed at various time points till 90 days after injection. RESULTS: No apoptosis changes of electron microscopy were observed in the hRPE cultured with FG, and the difference in the MTT test results was not statistically significant when compared with the control group (P>0.2). One day after suprachoroidal injection, slight choroidal hemorrhage occurred. No severe intraocular reactions were observed in any of the three groups, and FFA and IA showed no edema or leakage around blood vessels. There was no significant difference in latency or amplitude of the ERG wave among the three groups (P>0.1). Histopathological examinations showed the suprachoroidal FG induced localized inflammation (from acute inflammation to chronic phagocytosis) at the early stage and finally turned into fibrosis tissue. CONCLUSIONS: FG is feasible for suprachoroidal use, and no obvious toxic reaction was observed in either in vitro or in vivo studies.

Escalated regeneration in sciatic nerve crush injury by the combined therapy of human amniotic fluid mesenchymal stem cells and fermented soybean extracts, Natto.

Attenuation of inflammatory cell deposits and associated cytokines prevented the apoptosis of transplanted stem cells in a sciatic nerve crush injury model. Suppression of inflammatory cytokines by fermented soybean extracts (Natto) was also beneficial to nerve regeneration. In this study, the effect of Natto on transplanted human amniotic fluid mesenchymal stem cells (AFS) was evaluated. Peripheral nerve injury was induced in SD rats by crushing a sciatic nerve using a vessel clamp. Animals were categorized into four groups: Group I: no treatment; Group II: fed with Natto (16 mg/day for 7 consecutive days); Group III: AFS embedded in fibrin glue; Group IV: Combination of group II and III therapy. Transplanted AFS and Schwann cell apoptosis, inflammatory cell deposits and associated cytokines, motor function, and nerve regeneration were evaluated 7 or 28 days after injury. The deterioration of neurological function was attenuated by AFS, Natto, or the combined therapy. The combined therapy caused the most significantly beneficial effects. Administration of Natto suppressed the inflammatory responses and correlated with decreased AFS and Schwann cell apoptosis. The decreased AFS apoptosis was in line with neurological improvement such as expression of early regeneration marker of neurofilament and late markers of S-100 and decreased vacuole formation. Administration of either AFS, or Natto, or combined therapy augmented the nerve regeneration. In conclusion, administration of Natto may rescue the AFS and Schwann cells from apoptosis by suppressing the macrophage deposits, associated inflammatory cytokines, and fibrin deposits.

Tissue adhesives and the pancreas: biocompatibility and adhesive properties of 6 preparations.

OBJECTIVES: The aim of this study was to investigate biocompatibility and adhesive properties of 6 tissue adhesives available, when applied between the pancreas and jejunum in an experimental model. METHODS: Portion of jejunum was glued on the pancreas in rats with 3 cyanoacrylate derivatives (Histoacryl, Dermabond, and Glubran 2), 2 human fibrin sealants (Tisseel Duo Quick and Quixil), and 1 albuminglutaraldehyde sealant (BioGlue). Pancreatic tissue specimens and blood samples were harvested 1, 3, 7, and 21 days after gluing for histological determination and amylase activity measurement. Pancreaticojejunal attachment created with adhesives underwent tensile strength measurement at each time point. Samples were also taken from unoperated rats and sham-operated rats. RESULTS: Exposure and sham groups both induced a similar increase in amylase activity on day 1 with normalization by day 3. Sham operation induced mild changes in the pancreas. Each tissue adhesive induced changes in pancreatic histology to the entire gland. Injurious effect was more severe with the 3 cyanoacrylates than with the 3 fibrin/semisynthetic glues. Histoacryl and Quixil induced lower tensile strength than the other adhesives. CONCLUSIONS: All of the tissue adhesives studied induced histological changes in the pancreas of which at least part might be considered harmful. The potentially harmful tissue effects of the preparations tested might compromise the use of these substances in pancreatic surgery.

Comparison of the bacteriostatic effects, corneal cytotoxicity, and the ability to seal corneal incisions among three different tissue adhesives.

PURPOSE: To compare the bacteriostatic effects, corneal cytotoxicity, and ability to seal corneal incisions among fibrin glue and 2 commercially available cyanoacrylate derivatives: N-butyl cyanoacrylate and methoxypropyl cyanoacrylate. METHODS: The bacteriostatic activities of these tissue glues were verified by measuring the zones of bacterial growth inhibition surrounding the adhesive droplets on agar plates inoculated with Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, Escherichia coli, or Mycobacterium chelonae. Corneal cytotoxicity was tested by a direct contact method by using cultured bovine corneal epithelial cells, keratocytes, and corneal endothelial cells challenged with droplets of adhesives. Each of the cells was treated with droplets of adhesives. The ability to seal corneal incisions was verified by calculating the maximum intraocular pressure resistant to leakage of rabbit corneal stab wounds sealed with tissue adhesives. RESULTS: Methoxypropyl cyanoacrylate and N-butyl cyanoacrylate showed bacteriostatic effects against S. aureus, S. pneumoniae, and M. chelonae but not P. aeruginosa and E. coli. In contrast, fibrin glue had no such effects against either Gram-positive or -negative bacteria (P < 0.01). Methoxypropyl cyanoacrylate showed the highest levels of corneal cytotoxicity, followed by N-butyl cyanoacrylate. Fibrin glue, however, showed minimal cytotoxicity (P < 0.01). Methoxypropyl cyanoacrylate and N-butyl cyanoacrylate also displayed a greater ability to seal corneal incisions than that of fibrin glue (P < 0.01). CONCLUSIONS: The bacteriostatic effects, corneal cytotoxicity, and ability to seal corneal incisions differed among the 3 compounds tested. These different properties should be considered when choosing tissue adhesives during corneal surgery.

Fibrin glue as a suture substitute: histological evaluation of trabeculectomy in rabbit eyes.

PURPOSE: To describe the outcome of the use of fibrin adhesive (Quixil) in penetrating trabeculectomy in a rabbit model. METHODS: Fibrin adhesive was used experimentally to attach the conjunctiva and the scleral flap in two groups of 17 New Zealand albino adult rabbits (34 eyes). In the first experiment (20 eyes), the fibrin adhesive was used to reattach the tissue after conjunctival peritomy and scleral flap only in 14 eyes (experiment I). In 6 eyes (controls), the conjunctiva was attached with nylon sutures. In the second experiment (14 eyes), the fibrin adhesive was used after conjunctival peritomy, scleral flap, and penetrating trabeculectomy in 8 eyes (experiment II). In a control group of 6 eyes, nylon sutures were used to attach the scleral flap and the conjunctiva after penetrating trabeculectomy. Biomicroscopy and histopathological examinations were performed on postoperative days 1, 3, 7, 14, 21, and 30. Intraocular pressure was measured before and after surgery in the second experiment. Main outcome measures are histological presence of adhesive in the tissue, degree of capillary congestion, inflammatory reaction, collagen density [scar formation] and clinical (IOP measurements before and after surgery, conjunctival chemosis, anterior chamber reaction, presence of filtering bleb and wound leakage). RESULTS: In experiments I and II, the adhesive was well identified histologically in the tissue as an amorphic eosinophilic substance for up to day 3 and nearly disappeared by day 7. An acute inflammatory reaction was noted for up to 14 days, which converted to chronic inflammation with collagen deposits and scar formation by day 30. Similar inflammatory reaction was observed in the control group. The adhesive had no adverse effects on ocular tissue compared with sutures. One eye in experiment II demonstrated wound dehiscence. Intraocular pressure dropped from 17.35 mmHg preoperatively to 8.28 mmHg on postoperative day 1 in experiment II, and from 17.2 mmHg to 11.5 mmHg in the controls. No significant change in intraocular pressure was noted in experiment I. CONCLUSIONS: The fibrin adhesive had no adverse effects on ocular tissue compared with sutures. It might serve as an effective substitute for conjunctival and scleral wound closure in trabeculectomy surgery.

Retinal function after subconjunctival injection of carboplatin in fibrin sealant.

PURPOSE: To evaluate retinal function in a rabbit model after subconjunctival delivery of carboplatin in balanced saline solution (BSS) or fibrin sealant to determine possible retinal toxicity. METHODS: One group of rabbits (n = 5) received a unilateral subconjunctival injection of 12.2 +/- 1.0 mg/mL of carboplatin (Paraplatin) in BSS. Another group of rabbits (n = 5) received 25.1 +/- 7.7 mg/mL of carboplatin in fibrin sealant (Hemaseel APR). Rabbits injected with fibrin sealant only (n = 2) and BSS only (n = 2) were used as control groups. Electroretinographic recordings consisted of a series of intensities presented under dark- and light-adapted conditions. Electroretinograms were recorded before the injection (baseline) and 2 days, 1, 2, and 3 weeks after the injection. After 3 weeks, all rabbit eyes were obtained for histopathologic examination. RESULTS: Transient reductions in the dark-adapted b-wave amplitudes were noted 2 days after treatment for eyes injected with carboplatin compared with the vehicle-only treatment groups. Other treatment groups and postinjection time points showed no significant changes from baseline. Retinal structure and thickness were normal 3 weeks after treatment for all treatment groups. CONCLUSION: Subconjunctival delivery of carboplatin in fibrin sealant or BSS does not have a toxic effect on retinal function or structure in a non-tumor-bearing rabbit model at the doses used in this study at 3 weeks' follow-up.

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.

The current status of cyanoacrylate and fibrin tissue adhesives.

Surgical tissue adhesives could simplify complex surgical procedures by stabilizing tissue surfaces through hemostasis, sealing wounds, and fixating tissue in areas inaccessible to suture placement. The most common surgical tissue adhesives available to the surgeon include the cyanoacrylate derivatives and the fibrin tissue adhesives. Butyl-2 cyanoacrylate (Histoacryl) is a cyanoacrylate derivative that is frequently used in Canada and Europe. This adhesive has excellent binding strength for skin closure; however, subcutaneous implantation can result in inflammation and foreign body giant cell reaction. Fibrin tissue adhesives use a fibrin clot as the binding moiety and vary in adhesive strength depending on the fibrinogen concentration of the preparation. Autologous fibrin tissue adhesives are prepared using one of several different methods, which vary in fibrinogen yield and concentration. The currently available autologous fibrin tissue adhesives demonstrate good hemostatic properties with relatively low binding strengths. This article reviews the status of cyanoacrylate adhesives and the preparation, efficacy, and clinical applications of the fibrin tissue adhesives.