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Yi Zhang, John J Whalen, Paulo Falabella, Niki Bayat, Mark E. Thompson, Mark S Humayun; Efficacy Studies of Thermoresponsive Reversible Adhesive for Temporary Intervention in Ocular Trauma Utilizing a Rabbit Model. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1603.
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Poly(N-isopropylacrylamide), pNIPAM, 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 was proposed as a novel tissue adhesive to seal scleral wounds in our previous study. To evaluate feasibility in vivo, pNIPAM-based gel was used to seal 3mm scleral perforations in rabbit eyes and IOP vs. time was tracked and compared to control.
The ability of the hydrogels to seal perforating incisions through the sclera was evaluated using an in vivo New Zealand white rabbit model to mimic clinical cases. Three-millimeter straight, full-thickness, scleral incisions were created in the right eye (OD) of twelve (12) rabbits. In the treatment group (n = 5), 0.25mL pNIPAM-based gel was applied into the incisions by using a custom-made applicator with cooling function. In the control group (n=7), incisions were left open, and allowed to heal without adhesive. All eyes were treated with antibiotics and steroids once daily for 2.5 days. Intraocular pressures (IOP) of both eyes (OD and OS) were measured with an Icare, Inc., TONOVET® tonometer at baseline (before surgery) and postoperative at regular intervals. Ocular examinations were performed regularly to identify any signs of inflammation, infection, and toxicity. Statistical analysis was done to determine differences in IOP values between the groups. The rabbits were euthanized on day 3 and a histological examination was performed in the enucleated eyes.
Mean IOP in the group injected with pNIPAM-based gel (ODgel) were similar to mean IOP of the contralateral eyes (OS), which received no trauma. Mean IOPs of ODgel were significantly higher than the eyes (ODcontrol) which received a 3mm incision and no sealant intervention (control). Daily postoperative examinations showed no signs of ocular toxicity. Histologically, no inflammatory cells were seen in both the experimental and control eyes.
The Surgical procedures of pNIPAM-based gel adhesives were successfully validated in rabbit model as a fast and reversible approach to temporarily seal scleral penetrations, and these adhesives was well tolerated in rabbit eyes, with no or minimal ocular toxicity. The strength of the adhesive bond in the scleral trauma was satisfactory based on the IOP measurements.
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