Abstract
The objective of this work was to investigate phytantriol-based liquid crystal (LC) gels including cubic (Q2) and hexagonal (H2) phase for ocular delivery of pilocarpine nitrate (PN) to treat glaucoma. The gels were produced by a vortex method and confirmed by crossed polarized light microscopy, small-angle X-ray scattering, and rheological measurements. Moreover, the release behaviors and permeation results of PN from the gels were estimated using in vitro studies. Finally, the anti-glaucoma effect of LC gels was evaluated by in vivo animal experiments. The inner structure of the gels was Pn3m-type Q2 and H2 phase, and both of them showed pseudoplastic fluid properties based on characterization techniques. In vitro release profiles suggested that PN could be sustainably released from LC gels within 48 h. Compared with eye drops, Q2 and H2 gel produces a 5.25-fold and 6.23-fold increase in the Papp value (p < .05), respectively, leading to a significant enhancement of corneal penetration. Furthermore, a good biocompatibility and longer residence time on precorneal for LC gels confirmed by in vivo animal experiment. Pharmacokinetic studies showed that LC gels could maintain PN concentration in aqueous humor for at least 12 h after administration and remarkably improve the bioavailability of drug. Additionally, in vivo pharmacodynamics studies indicated that LC gels had a more significant intraocular pressure-lowering and miotic effect compared to eye drops. These research findings hinted that LC gels would be a promising pharmaceutical strategy for ocular application to enhance the efficacy of anti-glaucoma.
Highlights
Glaucoma is a progressive optic neuropathy caused by retinal ganglion cell death
Biofilm-like pilocarpine nitrate (PN)-loaded liquid crystal (LC) gels, including Q2 phase and H2 phase, were prepared for ocular application to treat glaucoma, whose matrix was constituted by PYT/water binary system and PYT/TAG/water ternary system, respectively
Their internal structures were identified by crossed polarized light microscopy (CPLM) and smallangle X-ray scattering (SAXS) methods to be Pn3m-type Q2 and H2 mesophase, respectively
Summary
Glaucoma is a progressive optic neuropathy caused by retinal ganglion cell death. As a chronic ophthalmic disease, it is characterized by the elevation of the intraocular pressure (IOP), decrease of retinal sensitivity and optic nerve head changing that lead to decreased vision (Yu et al, 2015; Hu et al, 2018). To ameliorate the limitations of eye drops, various delivery approaches have been investigated to increase ocular bioavailability during the past decades, including two major strategies: to enhance the corneal permeability of the drugs and to extend the residence time of the formulations (Almeida et al, 2014; Yu et al, 2015). Building on such background, many investigators have attempted several novel drug delivery systems, for example, polymeric micelles (Zhou et al, 2017), inserts (Everaert et al, 2017), suspensions (Kontadakis et al, 2018), ointments (Patere et al, 2018), gels (Moustafa et al, 2018), and lipid-based nanocarriers (Liu et al, 2018), to improve eye bioavailability. Various gel systems have attracted increasing attention for eye applications because they are more comfortable and likely to spread across the eye surface and tolerate the resist with tears during blinking (Krtalic et al, 2018)
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