Biocompatibility and Device Integrity of a Microfabricated Biopolymer Ocular Implant

Abstract

Purpose: : To assess the ocular tolerance and durability of a structured biopolymer device implanted into the rabbit eye.

Methods: : Biopolymer devices with microstructural surface architecture microfabricated from modified poly(caprolactone) (PCL) were implanted in New Zealand rabbit eyes (8 eyes in 6 rabbits). Thin-form devices were implanted into the anterior chamber (3 eyes) or vitreous cavity (5 eyes) via 20-gauge needle injection. Ocular tolerance was evaluated with serial ophthalmic exams over 1 to 6 months using pneumotonometry, slit lamp microscopy and indirect ophthalmoscopy. Histologic studies on enucleated post-mortem eyes were performed at 30 days to 6 months. Retrieved devices were evaluated by scanning electron microscopy (SEM) to determine their durability and structural integrity.

Results: : No signs of ocular toxicity were seen in the 8 study eyes over 1 to 6 months. Mild to moderate conjunctival injection was noted in 7 of 8 eyes; 4 cases resolved within 1 week. No ocular inflammation was noted in 6 of 8 eyes; 2 eyes had transient low grade iritis that resolved after 1 week. Traumatic posterior subcapsular cataracts from needle injection were present in 2 eyes. Endophthalmitis, retinal detachment, vitreous hemorrhage and retinal degeneration did not develop in any eyes. No device migration exceeding 1 clock hour or posterior dislocation was observed. Histological exam of 8 eyes showed no inflammation or morphologic abnormalities at ocular sites including the trabecular meshwork, retina and specific sites of anatomic residence of the implanted device. Retinal degeneration and device/tissue responses such as fibrotic encapsulation of the device were not seen. SEM studies demonstrated that the biopolymer device gross structure was maintained over 1 to 6 months. The microstructural surface featuring a 100-micron reservoir array showed no structural damage or degradation after implantation and ocular residency.

Conclusions: : Microstructured PCL biopolymers demonstrate material-ocular biocompatibility up to 6 months. Microstructural features at the scale of 100 microns maintain integrity after intraocular residence, supporting potential for functional micro-engineered biopolymers in ophthalmic applications.

Keywords: ocular irritancy/toxicity testing • retina • vitreous