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Yi Zhang, Paulo Falabella, Niki Bayat, Stacey Rauen, James D Weiland, John J Whalen, Mark E Thompson, Mark S Humayun; Thermoresponsive Reversible Adhesive for Temporary Intervention in Ocular Trauma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2353.
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Poly(N-isopropylacrylamide), pNIPAM, is a temperature-responsive polymer which exhibits a reversible macromolecular transition that demonstrates adhesive properties at body (eye) temperature and non-adhesive properties at decreased temperature. We report on the feasibility of developing a novel tissue adhesive to seal scleral wounds using pNIPAM-based gels.
Free-standing pNIPAM-based gels were synthesized using a wet chemistry approach, characterized and stored at low temperature prior to use. Adhesion to dissected cadaveric porcine scleral tissue was characterized using a uniaxial tension tester to test under ideal normal force conditions. An in vitro cadaveric porcine eye model was designed to assess the ability of the gels to seal penetrating incisions through the sclera, mimicking clinical cases. Adhesion in each test was compared against medical-grade cyanoacrylate glue and sutures, respectively. Real-time IOP was tracked in the whole porcine eye using 19-gauge catheter pressure transducer inserted through the pars plana. Primary objectives: 1) Determine whether pNIPAM-based gel can reach adhesion performance of cyanoacrylate in uniaxial tension testing. 2) Determine if pNIPAM-based gel can prevent hypotony in a cadaveric porcine eye and maintain IOP comparable to suture. Secondary objective: Determine if pNIPAM-based gel can be removed using a temperature lowering protocol.
Synthesized pNIPAM-based gels predictably and reversibly transitioned between adhesive and non-adhesive states in the desired temperature range for scleral closure. Uniaxial tension testing yielded adhesion performance data comparable to cyanoacrylate with some gel formulations. Intraocular pressure results from the porcine eye model showed that IOP as high as 70-77mm Hg could be maintained for sustained periods without any leakage. Performance in both tests varied as a function of placement procedure, chemical formula, molecular weight, and gel solution concentration. Gel detachment was successfully achieved by irrigation of the placement site with cold water.
pNIPAM-based gel adhesives may offer a fast and reversible approach to temporarily and satisfactorily seal scleral penetrations. Such adhesives represent a promising new reversible technique for temporary intervention in ocular trauma and other applications.
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