Synthesis and characterization of a new acrylic adhesive mixture for use in ocular strabismus surgery

Abstract

A new series of acrylic adhesive mixtures was specifically designed for use in strabismus surgery, more precisely to join the rectus muscles to the sclera. These two-part adhesives consisted of a mixture of ethyl cyanoacrylate (CN) and ethyl carboxyacrylate (ECA). ECA acted as a plasticizer imparting flexibility to the CN, and also as a nonreactive diluent, serving to reduce the exotherm in the reaction between CN and eye tissues. In this article, the synthesis of the ethyl carboxyacrylate is described, and the properties of different ethyl cyanoacrylate + ethyl carboxyacrylate mixtures were studied. The curing reaction of the adhesive mixtures was monitored using Fourier transform infrared (FTIR) spectroscopy and scanning differential calorimetry (DSC). The rheological properties of the cured CN-ECA adhesive films were studied using plate-plate rheometer experiments. To quantify the adhesion, single lap-shear tests produced between a rubber and the adhesive mixtures were performed and, to evaluate the adhesion to eye tissues, tensile strength measurements of superior rectus muscle/adhesive mixture/sclera joints were carried out. The 70CN-30ECA (v/v) adhesive mixture provided the most adequate balance between adhesion and mechanical properties in the joining of the superior rectus muscle to the sclera. The glass transition temperature of the CN-ECA adhesive mixtures linearly decreased with increase in the ECA content, and a lower degree of conversion during polymerization was obtained by increasing the ECA content. As a consequence, the CN-ECA mixtures were less stiff than CN, giving better performance in the joining of the rectus muscles to the sclera. Finally, the adhesion of CN was sufficiently decreased in CN-ECA mixtures, and the locus of failure was directed to the adhesive film in the joint between the rectus muscles and the sclera.