Imaging-Based Drug Penetration Profiling in an Excised Sheep Cornea Model

Area of Science:

• Ophthalmology
• Drug Delivery
• Corneal Science

Background:

• Topical ocular formulations are common for eye conditions.
• Existing in vitro methods primarily assess corneal permeation, not internal penetration depth.
• Methods for determining substance penetration within the cornea are limited.

Purpose of the Study:

• To introduce and validate a novel method for analyzing time-dependent penetration depth within the cornea.
• To compare a semiquantitative imaging technique with a quantitative depth-cut method.
• To assess the penetration kinetics of a model substance in a surrogate cornea model.

Main Methods:

• Utilized sheep cornea as a human surrogate, maintaining tissue viability.
• Employed fluorescein sodium as a model substance at varying concentrations.
• Applied a semiquantitative imaging method alongside a quantitative corneal depth-cut technique for penetration analysis.
• Validated kinetic traceability using polysorbate 80 as a penetration enhancer.

Main Results:

• Both methods demonstrated a strong correlation in measuring concentration- and time-dependent penetration depth of fluorescein sodium.
• The imaging method successfully detected the retention of larger molecules like hyaluronic acid and nanoemulsions within the lacrimal layer.
• Sustained tissue viability and integrity were maintained throughout the experiments.

Conclusions:

• The developed method provides a reliable approach for assessing corneal penetration depth and kinetics.
• This technique is valuable for evaluating the efficacy of topical ocular drug delivery systems.
• The study highlights the potential for imaging methods in analyzing ocular drug retention.