A reversible thermosensitive adhesive for retinal implants: in vivo experience with plasma-deposited poly(N-isopropyl acrylamide).

Abstract

To study the in vivo effects of a thermosensitive retinal adhesive, plasma-polymerized N-isopropyl acrylamide (ppNIPAM), in rabbit eyes. Parylene C(poly(monochloro-p-xylylene)) (20 microm) and poly(dimethyl siloxane) (PDMS) (> or =200 microm) coated with ppNIPAM were used as implant materials. Following pars plana vitrectomy (PPV), ppNIPAM coated parylene (n = 3) and PDMS (n = 3) implants were inserted over the retina in six rabbits. Baseline and follow-up imaging (color fundus photographs, fluorescein angiography, and optic coherence tomography [OCT]) and electroretinogram recordings were performed. Histologic evaluation was performed following enucleation at 6 weeks. Intraoperative retinal adhesion occurred in all eyes with ppNIPAM coated parylene and PDMS implants. Two eyes developed retinal tears during the implantation procedure and the ppNIPAM coated implants closed the retinal tears successfully preventing retinal detachment. OCT findings confirmed the retinal adhesion in all eyes. Four weeks after implantation one parylene and one PDMS implant detached partly from the retinal surface. Histology showed mild changes at the outer retinal segments. There was no evidence of ocular toxicity and inflammation. None of the eyes that had an implant covering the retinal tear developed a retinal detachment but had some inflammatory changes around the implants. ppNIPAM coated implants may provide retinal adhesion in vivo without measurable ocular toxicity in the short term. Covering a retinal tear, the ppNIPAM coated implants may prevent retinal detachment.