DRUG-ELUTING IOLs

A new nanotechnology technique, using a thin film coating as a vehicle for pharmaceutical substances, is showing promise and could be applied to IOLs, thereby eliminating the need for postoperative eye drops, said Lampros Lamprogiannis MD, MSc, Aristotle University of Thessaloniki, Thessaloniki, Greece. “The thin film was transparent and demonstrated a smooth release of the test drug. In previous research, the thin-film technology has shown excellent biocompatibility, and the films leave no toxic by-products as they decompose,” he told the XXXI Congress of the ESCRS in Amsterdam.

He presented his findings from a study in which he and his associates in the Laboratory for Thin Films - Nanosystems & Nanometrology, Department of Physics, Aristotle University of Thessaloniki, headed by Prof Stergios Logothetidis, prepared four groups of thin films on a silicone substrate using the spin-coating method. The technique involves depositing a small amount of the polymers mixed with the test drug, in this case dexamethasone, on the substrate, which rotates very fast. Part of the mixture is allowed to evaporate, leaving a thin film on the substrate.

Organic polymers served as a matrix for the films and each group had a different amount of dexamethasone. There were two groups with two film layers, one of which had a two-to-one ratio of matrix to dexamethasone, the other had a three-to-one ratio. The remaining two groups had one layer of film, with matrix-to-dexamethasone ratios corresponding to those of the other two groups.

Atomic force microscopy showed that in the two dual-layer groups the dexamethasone tended to aggregate but in the two monolayer groups the film was speckled with nanopores which apparently contained dexamethasone. Ellipsometry showed that the film reduced the transparency of the silicone substrate to light in the near-to-ultraviolet wavelengths. The film’s maximal level of reflectivity refractivity is in the green light wavelengths.

In a further investigation they tested the rate of release of the drug into an aqueous-like liquid over a 10-week period. They found that with all the films the release of dexamethasone was most rapid during the first two weeks, with 60 per cent released by one month and the rest released in a gradually tapering fashion over the following two weeks.

“We are currently working, under the supervision of assistant professor of ophthalmology Ioannis Tsinopoulos, on the development of thin films to be deposited directly on the surface of IOLs which we plan to test in vitro and possibly in an in vivo study. Our ultimate goal is to combine more than one pharmaceutical substance in the film so that patients with coated intraocular lenses will not require further postoperative application of eye drops,” Dr Lamprogiannis concluded.

Further developments will be presented by Dr Athanassios Karamitsos MD, PhD, at the XXXII ESCRS Congress in London.

Lampros Lamprogiannis: lamproslamprogiannis@hotmail.com