Chitosan Nanoparticles: The Drug Delivery System to the Anterior Segment of the Eye

The effectiveness of drug penetration into the inner tissues of the eye under local application is significantly limited by the barrier effect of the cornea and by the washout of the drug with the lacrimal fluid. To increase the bioavailability of a drug, it is proposed to include the drug in the chitosan particles formed by two types of chitosan: 5 kDa chitosan and 72 kDa glycol-chitosan. Chitosan particles with the loaded angiotensin-converting enzyme inhibitor enalaprilat, capable to reduce intraocular pressure, are characterized by dynamic light scattering and scanning electron microscopy. Particles formed by 5 kDa chitosan have an average hydrodynamic diameter from 85 to 125 nm and a positive ζ potential of +21 ± 3 mV, while particles formed by 72 kDa glycol-chitosan have a size from 440 to 480 nm and are characterized by a ζ potential of +10 ± 2 mV. The percentage of enalaprilat inclusion in the chitosan particles is 25% and 40%, respectively. In vivo experiments showed that the inclusion of the drug int the chitosan particles can increase the retention time of enalaprilat in the lacrimal film of rabbits.