| Abstract
| - Poly(ethylene glycol) of various sizes was used as a molecular spacer to separate the cell-targetingligand, folate, from the surface of poly-l-lysine. The resulting ternary macromolecule (pLys-PEG-folate) was investigated in various formulations for its ability to transfect reporter plasmids intoreceptor-bearing HeLa and IGROV cell lines. Formulations were optimized with respect to DNAcontent, ± charge ratio, and the size and amount of PEG substitution off the pLys backbone.Transfection activity was highest 48 h after sample introduction, and PEG 3400 was determined tobe the most favorable spacer size tested. pLys-PEG-folate:DNA transfection was also found to be bothconcentration dependent and saturable; plus, it was blocked by the addition of excess-free folate,indicative of a specific mechanism of uptake. Transfection activity was virtually identical for complexesformed in 10% serum-supplemented media, deionized water, or Hepes buffer. And, cell viabilityremained greater than 85% at the highest concentrations of pLys-PEG-folate:DNA complexes tested(4.8 μg/mL pLys 331 000; 12 μg/mL DNA). Taken together, these observations provide evidence thatpLys-PEG-folate:DNA complexes are taken up specifically by the folate endocytosis pathway, andthat the intramolecular spatial distance of the ligand from the pLys backbone dramatically influencestransfection.
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