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Abstract no.: 3
Vitreous– a barrier to non‐viral ocular gene therapy
Author(s) -
Peeters L.,
Sanders N.N.,
Braeckmans K.,
Boussery K.,
Van de Voorde J.,
De Smedt S. C.,
Demeester J.
Publication year - 2006
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.2006.00420_3.x
Subject(s) - polystyrene , fluorescence recovery after photobleaching , liposome , chemistry , biophysics , peg ratio , fluorescence microscope , fluorescence , membrane , polymer , biochemistry , organic chemistry , optics , physics , finance , economics , biology
Purpose Intravitreal injection of therapeutic DNA, complexed to non‐viral carriers like cationic liposomes, may be promising to treat many severe retinal eye diseases. However, after intravitreal injection such DNA/cationic liposome complexes, so called lipoplexes, which are typically some hundreds of nanometers in size, must first diffuse through the vitreous before they can reach the retina. The aim of this study was both to elucidate whether vitreous is a barrier for the lipoplexes as well as to evaluate strategies to overcome this barrier. Methods Fluorescent polystyrene nanospheres and lipoplexes were mixed with vitreous and their mobility was monitored by fluorescence recovery after photobleaching (FRAP), a microscopy based technique. The stability of lipoplexes and naked pDNA in vitreous was studied by gel electrophoresis. Results We showed that polystyrene nanospheres, in our first experiments used as a model for the lipoplexes, do not diffuse freely into the vitreous but adhere to fibrillar structures in the vitreous, most likely to collagen fibers. Making the surface of the polystyrene nanospheres hydrophillic by attaching hydrophillic polyethyleneglycol (PEG) chains at their surface circumvented the binding to fibrillar structures in the vitreous. FRAP revealed that ‘pegylated’ polystyrene nanospheres, as long as they are smaller than 500 nm in size, are indeed mobile in the vitreous. It was further demonstrated that lipoplexes severely aggregate in vitreous and strongly bind to biopolymers in the vitreous which immobilizes them completely. However, as observed for the polystyrene nanospheres, coating of the lipoplexes with PEG avoided both their aggregation in the vitreous as well as their binding to fibrillar structures. Conclusions Modifying the surface of lipoplexes with hydrophylic PEG chains prevents them from aggregation in vitreous. In this way lipoplexes are obtained which can freely move in vitreous, an absolute request to be able to reach the retina after intravitreal injection.