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Editors Selection IGR 16-4
Medical Treatment: Drug delivery
Comment by Tina Wong on:
60294 Nanosponge-Mediated Drug Delivery Lowers Intraocular Pressure, Lambert WS; Carlson BJ; van der Ende AE et al., Translational vision science & technology, 2015; 4: 1
Development of drug delivery systems for ophthalmology, particularly for glaucoma and fibroproliferative retinal disorders is a fast growing area of research. Here the authors report on a proof of concept evaluation of their nanosponge delivery system for the extended release of brimonidine, travaprost in a mouse model of raised intraocular pressure. First of all, the description is rather misleading in that the nanoparticles described are not actually sponges, which one would think of. Instead the 'sponges' are biodegradable cross-linked particles that are injected intravitreally. This route of delivery of the brimonidine or travoprost would appear to be unnecessarily invasive for clinical use in glaucoma.
The authors show that IOP lowering effect for the brimonidine nanosponges was sustained for longer, 30 days with the larger 700 nm nanosponge compared to the 400nm version, which showed IOP lowering for 18 days. This is not surprising since the amount of drug loading is higher in the larger nanosponges. Similar effect of size was reported with the travoprost nanosponges.
A practical challenge in the use of such a delivery system would be the effect of size of the injected particles into the vitreous cavity. There is no mention of whether these nanosponge particles aggregate upon injection, an important factor to consider. Patients may experience visual disturbances from the opaque particles floating inside and particle aggregation may exacerbate this. So size and transparency are considerations to take when it comes to designing drug delivery systems for intravitreal injection. The authors also evaluated the nanosponge delivery system as a potential carrier for drugs and active biological molecules for vitreoretinal disorders such as age related macular degeneration. It seems to be a better fit for this delivery system to be applied for AMD.
The nanosponge delivery will ensure that the drug effectively reaches the target tissue, the retina. As to its application for glaucoma, it seems to be a less attractive approach compared to other systems being developed in this area. The target tissues in glaucoma remain in the anterior segment and it therefore seems logical to have a delivery platform placing the active drug closest to the site of action, namely the trabecular meshwork and ciliary body. Perhaps with this in mind, the nanosponge delivery system could provide a more effective and sustained IOP lowering than it currently does.
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