The AAPS Journal

, Volume 6, Issue 3, pp 72-80

Neural retina limits the nonviral gene transfer to retinal pigment epithelium in an in vitro bovine eye model

  • Leena PitkänenAffiliated withDepartment of Pharmaceutics, University of KuopioDepartment of Ophthalmology, Kuopio University Hospital Email author 
  • , Jukka PelkonenAffiliated withDepartment of Clinical Microbiology, University of KuopioDepartment of Clinical Microbiology, Kuopio University Hospital
  • , Marika RuponenAffiliated withDepartment of Pharmaceutics, University of Kuopio
  • , Seppo RönkköAffiliated withDepartment of Pharmaceutics, University of Kuopio
  • , Arto UrttiAffiliated withDepartment of Pharmaceutics, University of Kuopio


We investigated the permeation of liposomal and polymeric gene delivery systems through neural retina into retinal pigment epithelium (RPE) and determined the roles of various factors in permeation and subsequent uptake of the delivery systems by RPE. Anterior parts and vitreous of fresh bovine eyes were removed. Retina was left intact or peeled away. Complexes of ethidium monoazide (EMA)-labeled plasmid DNA and cationic carriers (polyethyleneimine, poly-L-lysine, DOTAP liposomes) were pipetted on the retina or RPE. Two hours later the neural retina was removed, if present, and the RPE cells were detached. Contaminants were removed by sucrose centrifugation, and the RPE cells were analyzed for DNA uptake by flow cytometry. Cellular uptake of FITC-dextrans (molecular weight [mw] 20 000, 500 000 and 2 000 000), FITC-poly-L-lysine (mw 20 000), FITC-labeled oligonucleotide (15-mer), and naked EMA-labeled plasmid DNA was determined after pipetting the solutions on the RPE or neural retina. Location of the fluorescent materials in the retina was visualized with fluorescence microscopy. Neural retina decreased the cellular uptake of DNA complexes by an order of magnitude, the uptake of FITC-dextrans slightly, whereas delivery of polycationic FITC-poly-L-lysine to RPE was almost completely inhibibited. Neural retina decreased the cellular uptake of FITC-oligonucleotides, while the uptake of uncomplexed plasmid was always negligible. conclusions from FACS and fluorescence microscopy were similar: delivery of polymeric and liposomal DNA complexes into RPE are limited by the neural retina. This is due to the size and positive charge of the complexes.


gene delivery intravitreal retina liposome polymer