Hyaluronic acid coated poly-ɛ-caprolactone nanospheres deliver high concentrations of cyclosporine A into the cornea

Abstract

The objective of this study was to determine cyclosporine A (Cy A) levels in ocular tissues and fluids after topical administration of poly-ɛ-caprolactone (PCL)/benzalkonium chloride (BKC) nanospheres and hyaluronic acid (HA) coated PCL/BKC nanospheres onto healthy rabbit corneas. Nanospheres were prepared by nanoprecipitation and purified by gradient-rate centrifugation. Cy A (0.1%) in either castor oil solution (group 1), PCL/BKC nanosphere formulation (group 2) or HA coated PCL/BKC nanosphere formulation (group 3) was instilled onto rabbit corneas. Tear samples were adsorbed onto Schirmer tear strips. Cy A concentrations of fluid (blood, aqueous humor, tear) and specimen extracts (cornea, conjunctiva, iris/ciliary body) were determined by high performance liquid chromatography–mass spectrometry (LC–MS). The mean corneal Cy A concentration obtained at 0.5, 1, 2, 4, 8 and 24 h following instillation of the formulations ranged between 0.12 and 1.2 ng/mg tissue for group 1, 5.9–15.5 ng/mg tissue for group 2 and 11.4–23.0 ng/mg for group 3 (one-way analysis of variance (ANOVA) and pairwise tests (SNK (Student–Newman–Keuls) and Tukey); p < 0.05). Conjunctival Cy A levels of group 2 and 3 were not significantly different at any of the time points tested. However, there was a significant difference between Cy A concentration of castor oil formulation and that of PCL/BKC nanosphere formulation at 1 and 8 h ( p < 0.05). The mean iris/ciliary body concentrations obtained with the three formulations were not significantly different at any time point with the exception of group 2 levels being higher than those of groups 1 and 3 at 1 h ( p < 0.05). The lowest ocular tear Cy A concentrations (16–114 ng/ml) were found following the instillation of HA coated PCL/BKC nanoparticles (group 3) during the time period tested. Cy A loaded PCL/BKC and HA coated PCL/BKC nanospheres are able to achieve high levels of Cy A in the cornea that is 10–15-fold higher than that is achieved with Cy A solution in castor oil. Nanosphere formulation and HA may play an important role in delivering high levels of cyclosporine A into the cornea.