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Grace C. Shih, Eva M. Harth, Brian J. Carlson, David J. Calkins; Nanoparticle Delivery of Ocular Hypotensive Compounds. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3079.
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Elevated intraocular pressure (IOP) is the only modifiable risk factor for glaucoma. However, a major treatment barrier is patient compliance with use of topical agents to manage IOP, thus prompting a search for protracted therapeutic options. Recently, nanoparticles have been used for targeted drug delivery in chemotherapeutics, but have yet to be employed in ocular indications. To address the need for extended-release treatments, we examined the efficacy of nanoparticle-encapsulated compounds administered intravitreally to lower IOP in mice with microbead-induced ocular hypertension.
We constructed 400 and 700 nm nanoparticle sponges encapsulating bimatoprost (22.4% and 29.35 %, respectively) at 14% cross-linking density. C57BL/6 mice received a bilateral injection of microbeads (1.5 ul) into the anterior chamber to elevate IOP, followed by an intravitreal injection (1.0 ul) of either bimatoprost-encapsulating nanoparticles or PBS. IOP was measured by tonopen in both eyes up to 47 days post-injection.
Microbead injections elevated IOP bilaterally 40-43% above baseline measurements of 13-14 mmHg. A single injection of 400nm bimatoprost nanoparticles lowered IOP to baseline for two weeks followed by a gradual return to elevated levels by day 25. In contrast, 700nm bimatoprost nanoparticles lowered IOP for five weeks followed by a gradual return to elevation by day 48. Both hypotensive effects were highly significant (p<0.001).
Nanoparticle sponges encapsulating bimatoprost, when injected intravitreally, are effective at reducing elevations in IOP induced by microbead injection into the anterior chamber. Increasing particle size prolonged IOP reduction. This suggests that intravitreal injections of therapeutically-loaded nanoparticles may be a long-term drug delivery solution for glaucoma.
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