Octyl 2-cyanoacrylate tissue adhesive in experimental scleral buckling

BioAdhere: tailor-made bioadhesives for epiretinal visual prostheses

Introduction: Visual prostheses, i.e. epiretinal stimulating arrays, are a promising therapy in treating retinal dystrophies and degenerations. In the wake of a new generation of devices, an innovative method for epiretinal fixation of stimulator arrays is required. We present the development of tailor-made bioadhesive peptides (peptesives) for fixating epiretinal stimulating arrays omitting the use of traumatic retinal tacks. Materials and methods: Binding motifs on the stimulating array (poly[chloro-p-xylylene] (Parylene C)) and in the extracellular matrix of the retinal surface (collagens I and IV, laminin, fibronectin) were identified. The anchor peptides cecropin A (CecA), KH1, KH2 (author's initials) and osteopontin (OPN) were genetically fused to reporter proteins to assess their binding behavior to coated microtiter plates via fluorescence-based assays. Domain Z (DZ) of staphylococcal protein A was used as a separator to generate a bioadhesive peptide. Following ISO 10993 "biological evaluation of medical materials", direct and non-direct cytotoxicity testing (L-929 and R28 retinal progenitor cells) was performed. Lastly, the fixating capabilities of the peptesives were tested in proof-of-principle experiments. Results: The generation of the bioadhesive peptide required evaluation of the N- and C-anchoring of investigated APs. The YmPh-CecA construct showed the highest activity on Parylene C in comparison with the wildtype phytase without the anchor peptide. eGFP-OPN was binding to all four investigated ECM proteins (collagen I, laminin > collagen IV, fibronectin). The strongest binding to collagen I was observed for eGFP-KH1, while the strongest binding to fibronectin was observed for eGFP-KH2. The selectivity of binding was checked by incubating eGFP-CecA and eGFP-OPN on ECM proteins and on Parylene C, respectively. Direct and non-direct cytotoxicity testing of the peptide cecropin-A-DZ-OPN using L-929 and R28 cells showed good biocompatibility properties. Proof-of-concept experiments in post-mortem rabbit eyes suggested an increased adhesion of CecA-DZ-OPN-coated stimulating arrays. Conclusion: This is the first study to prove the applicability and biocompatibility of peptesives for the fixation of macroscopic objects.

Extraocular muscle fixation to porous polyethylene orbital implants using 2-octyl-cyanoacrylate

PURPOSE

To evaluate the efficacy of bioadhesive in attaching the extraocular muscles to porous polyethylene spheres in rabbit enucleated cavities.

METHODS

A prospective, experimental study was performed. Eight adult New Zealand white rabbits underwent right enucleation with insertion of an unwrapped 12 mm porous polyethylene sphere. The superior and inferior rectus muscles were attached to the implant with 2-octyl cyanoacrylate placed to the underside of the muscles and application of pressure for 5 seconds. Ninety days after surgery, the orbits were exenterated and four animals underwent histologic evaluation and the other four animals tensile strength testing of the muscle-sphere attachment.

RESULTS

There were no exposures or infections of the implants and the muscles remained attached in all cases. Histologic examination showed fibrous tissue reaction at the muscle-sphere attachment with minimal inflammation of the surrounding tissues; a pseudocapsule formation around the spheres and full vascularization of the implant was also observed. There was no evidence of residual glue on histologic examination. Tensile strength testing showed that rupture force was similar between bonded muscle and the porous polyethylene sphere.

CONCLUSIONS

The 2-octyl-cyanoacrylate did not cause deleterious effects in orbital tissues and provided strong adhesion between muscles and spheres. Bioadhesive may be an option for attaching the extraocular muscles to orbital implants in anophthalmic cavity reconstruction.

REVERSIBLE THERMOSENSITIVE GLUE FOR RETINAL IMPLANTS

PURPOSE

To determine in vitro effects of a plasma polymerized N-isopropyl acrylamide (pNIPAM) coating for thermally controllable adhesion to retinal tissue.

METHODS

Polyimide (50 microm), parylene C [poly(monochloro-p-xylylene)] (20 microm), and poly(dimethyl siloxane) (PDMS) (200 microm) coated with pNIPAM were used as implant materials to test retinal adhesion in enucleated pig eyes. Following preparation of the implant materials (n = 5) and retina, the authors held the implants over the retinal tissue at 22 degrees C and gradually increased the temperature of the water bath within 15 minutes. While increasing the temperature the authors monitored the adhesion with the retina and pNIPAM coated implant. The authors measured the adhesive force by a traction test using a suture attached to the implant and a strain gauge. Then the authors checked the reversibility of the adhesion by lowering the temperature of the water bath.

RESULTS

There was no retinal adhesion at room temperature (22 degrees C). The adhesion developed strongly within 60 seconds after reaching the critical temperature (>or=32 degrees C). This adhesion was persistent when the authors applied tractional forces of 98 mN and 148 mN between 32 and 38 degrees C. When the authors lowered the temperature back to 22 degrees C by irrigation with cold BSS, the implants detached from the retinal surface without using any tractional force.

CONCLUSION

pNIPAM provides effective in vitro retinal adhesion between 32 and 38 degrees C and this adhesion is completely reversible by lowering the temperature of the physiologic medium.

Preliminary in vitro evaluation of 2-octyl cyanoacrylate (Dermabond) to seal corneal incisions

OBJECTIVE

To compare the efficacy of Dermabond with conventional nylon sutures for sealing linear corneal incisions.

METHODS

A keratome knife was used to create a 4-mm full-thickness linear corneal incision anterior to the limbal arcade in 20 fresh pig eyes. The incision was sealed with Dermabond tissue adhesive or closed with 10-0 nylon sutures. A 27-gauge needle connected via tubing to a bottle containing balanced salt solution (BSS) was inserted into the anterior chamber. Infusion pressure was controlled by varying the height of the column of BSS. The tensile strength of the incisions was measured by increasing the infusion pressure to the point where leakage was noted.

RESULTS

The mean height at which leakage was detected was 100.20 +/- 31.19 cm H(2)O (equivalent to a pressure of 73.70 +/- 22.99 mm Hg) for the nylon suture group (n = 10 eyes) and 113.80 +/- 31.20 cm H(2)O (equivalent to a pressure of 83.71 +/- 22.95 mm Hg) for the Dermabond group (n = 10 eyes). The difference was not significant (P = 0.343).

CONCLUSIONS

The mean leakage pressures were comparable for the 2 groups. Either method of closure should be able to withstand any postoperative increases in intraocular pressure. Dermabond adhesive may be considered as an alternative to conventional sutures in corneal wound closure.