In order to reduce the lacrimal elimination and to increase the intraocular penetration of betaxolol after ocular administration, a drug carrier was prepared, polycapro-lactone nanocapsules, containing betaxolol in the base form, which was applied in the medical treatment of glaucoma in rabbits [910-912]. Reduction of cardiovascular side effects associated with ocular administration of metipra-nolol by inclusion in polymeric nanocapsules was investigated [913]. Antimetastatic activity in vivo of MTP-Chol entrapped in polyisobutylcyanoacrylate nanocapsules was studied [914]. With the aim of exploring the potential of poly(e-caprolactone) nanocapsules as drug carriers for ocular administration, the mechanism of interaction of these nanocapsules with the corneal and conjunctival epithelia was examined [915]. Ocular penetration of 1% cyclosporine A from nanocapsules and conventional formations in rabbit eyes was studied [916]. Topical application of nanocapsules of cyclosporine A on a penetrating keratoplasty rejection model was developed [917].

A research program was initiated to assess the ability of nanosperes to improve the biodelivery of active ingredients to plants [918]. The goal was to obtain stable poly(e-caprolactone) nanosperes with the smallest size and the largest amount of encapsulated active ingredients, using a nanoprecipitation method.

Chitosan-coated and poly-L-lysine-coated poly-e-caprolactone nanocapsules were designed based on a strategy that combines the features of poly-e-caprolactone nano-capsules as ocular carriers with the advantages of a cationic mucoadhesive coating and their capacity for increasing the corneal penetration of drugs investigated [919]. The ability of different drug carriers to improve the ocular bioavailability of drugs was investigated in the rabbit eye [920]. The assayed drug carriers were suspensions of nanoparticles, nanocapsules, and microparticles made of poly-e-caprolactone and a submicrometer emulsion. Polyester nanocapsules as new topical ocular delivery systems for cyclosporin A were developed [921-923]. The nanocapsules are an interesting alternative to the olive oil solution or ointments for the delivery of cyclosporin A to the eye [922].

Uptake of cyclosporine A loaded colloidal drug carriers by mouse peritoneal macrophages in vitro was studied [924]. The [H-3] cyclosporine A loaded colloidal particles, poly-lactic acid nanospheres, polylactic acid nanocapsules, and microemulsions, were prepared. The [H-3] cyclosporine A loaded colloidal particles were incubated with MPM for 30 min at 31 °C, then the cells were separated from the colloidal particles and the radioactivity was measured by a liquid scintillation counter.

Efficacy of topical cyclosporine A-loaded nanocapsules on keratoplasty rejection in the rat was evaluated [925]. Cyclosporine A formulated in migliol oil delayed corneal rejection onset, but blood levels were evident in this group. Cyclosporine A-loaded nanocapsules showed no effect on rejection and the drug was not detectable in blood.

Acyclovir-loaded polyethyl-2-cyanoacrylate (PECA) nanospheres were prepared by an emulsion polymerization process in the micellar phase and characterized [926]. The influence of the presence of nonionic surfactant as well as other substances [i.e., 2-hydroxypropyl-^-cyclodextrin (HP-^-CyD) and PEG] on formulation parameters and loading capacity was investigated. The presence of PEG resulted in an increase of mean size and size distribution. Ocular tolerability of PEG-coated PECA nanospheres was evaluated by the in vivo Draize test. The acyclovir-loaded PEG-coated PECA nanospheres showed a significant (p < 0.001) increase of drug levels (25-fold) in aqueous humor compared with the free drug or the physical mixture.

The anatomical, physiological, and pharmacological properties of the eye explain the short precorneal residence time and the poor bioavailability of most eyedrop solutions [927]. Many approaches were proposed to increase ocular bioavailability of drugs. Most eyedrops included a viscosity agent in their formulation to significantly prolong residence time although the increased viscosity was limited due to patient discomfort. The developments included biodegradable inserts, eyedrops based on cyclodextrins, liposomes, or nanoparticles.

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