Excised Porcine Cornea Integrity Evaluation in an in vitro Model of Iontophoretic Ocular Research

Abstract

Background/Aims: It is a challenge to adapt traditional in vitro diffusion experiments to ocular tissue. Thus, the aim of this work was to present experimental evidence on the integrity of the porcine cornea, barrier function and maintenance of electrical properties for 6 h of experiment when the tissue is mounted on an inexpensive and easy-to-use in vitro model for ocular iontophoresis. Methods: A modified Franz diffusion cell containing two ports for the insertion of the electrodes and a receiving compartment that does not need gassing with carbogen was used in the studies. Corneal electron transmission microscopy images were obtained, and diffusion experiments with fluorescent markers were performed to examine the integrity of the barrier function. The preservation of the negatively charged corneal epithelium was verified by the determination of the electro-osmotic flow of a hydrophilic and non-ionized molecule. Results: The diffusion cell was able to maintain the temperature, homogenization, porcine epithelial corneal structure integrity, barrier function and electrical characteristics throughout the 6 h of permeation experiment, without requiring CO₂ gassing when the receiving chamber was filled with 25 mM of HEPES buffer solution. Conclusion: The system described here is inexpensive, easy to handle and reliable as an in vitro model for iontophoretic ocular delivery studies.

Transcorneal iontophoresis of dendrimers: PAMAM corneal penetration and dexamethasone delivery

“…The same protocol, but in the absence of the electrical current, was performed for the passive experiments. The integrity of the cornea following iontophoresis was previously confirmed after 6 h of electrical current application, with a total electric current density of 180 mA/cm 2 [3].…”

“…After the preparation of the cornea, modified iontophoretic vertical diffusion cells [3] were assembled with the cornea, separating the donor from the receptor compartment. The area of the cornea that was exposed was 0.78 cm 2 .…”

“…Transcorneal and transcleral iontophoresis are non-invasive and safe physical methods that involve the application of a low electrical potential gradient across the cornea [1][2][3] and sclera [1,4,5], respectively, to enhance drug delivery to anterior and posterior segments of the eye. Early studies have demonstrated that iontophoresis increased the concentration of penicillin in the aqueous humor compared with subconjunctival injections [6] and recently, successful delivery of nucleic acids [7,8] and siRNAs [9] into the eye has been reported.…”

A simple and high‐resolution HPLC‐PDA method for simultaneous quantification of local anesthetics in in vitro buccal permeation enhancement studies

“…The suitability of the epithelium was assessed by measuring its electrical resistance. The isolated esophageal epithelium was sandwiched between the donor and receptor compartments of modified vertical side-by-side diffusion cells (Unividros, Ribeirão Preto, SP, Brazil) with a permeation area of 0.64 cm 2 and receptor compartment volume of 35 mL (Gratieri et al, 2010) . Both donor and receptor compartments were filled with artificial saliva.…”

Topical delivery of ocular therapeutics: carrier systems and physical methods

“…[239,240] Iontophoresis was shown to increase the concentration of penicillin in the aqueous humour compared with subconjunctival injections [239] and provided satisfactory results when treating intraocular infections induced by staphylococcus. [240] Since these studies, there have been many reports showing the application of iontophoresis to improve drug delivery through both the cornea [236,[241][242][243] and sclera, [243][244][245][246][247] including improvement of the penetration of macromolecules. [237,248,249] In general, iontophoresis through the sclera (transscleral iontophoresis) is more effective for drug delivery to the posterior segment of the eye whereas iontophoresis through the cornea (transcorneal iontophoresis) is more useful for drug delivery to the anterior segment.…”