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S. Li, J. T. A. Meij, J. Hao, Y. Zhang, T.-H. Young, W. W. Y. Kao, C. Y. Liu; Electric Field Enhanced Delivery of Macromolecules for Gene Transfer in the Corneal Epithelium. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3194. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The objective was to study the effects of molecular size on electrically assisted delivery of macromolecules into the corneal epithelium in vivo. Corneal gene transfer was also studied using these methods.
Anodal and cathodal iontophoresis applications of 2 to 4 mA (up to 1 min) and up to 8 electroporation pulses of 20 to 100 V (2 to 50 ms each pulse) were the electrical treatment protocols. Chemically enhanced passive delivery methods with sodium caparate and digitonin were also performed for comparison. EGFP plasmid DNA (naked), viral encapsulated DNA, siRNA, and FITC-dextran of different molecular weight (4k to 250k Dalton) were the compounds tested in this study. Direct microscopy and whole mount confocal microscopy were used to analyze and compare the amounts of the compounds delivered into the cornea. All experiments were conducted with mice in vivo.
In the EGFP DNA study, all tested protocols failed to effectively deliver the compound into the corneal epithelium for transfection. For the smaller macromolecules, iontophoretic delivery of FITC-dextran was observed to be molecular-size dependent. Iontophoresis was effective in delivering macromolecules up to 70k Dalton into the cornea. The results of anodal and cathodal iontophoresis were also observed to be different although the electrical parameters were identical, suggesting an influence of the polarity of the electric fields. This may be related to electrokinetic phenomena such as electroosmosis in the cornea. Electroporation delivery was less effective than that of iontophoresis, and passive delivery with sodium caparate and digitonin was ineffective compared with iontophoresis.
The results illustrate the difficulty in delivering large macromolecules such as plasmid DNA into the corneal epithelium but suggest the feasibility of macromolecular delivery of molecular weight up to 70k Dalton.
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