Novel hyperbranched dendron for gene transfer in vitro and in vivo

Novel hyperbranched dendron (HD) polymers were synthesized using a low molecular weight poly(ethyleneimine) core (BPEI). Using successive attachment of ethyleneimine moieties to the PEI core, the relative ratio of linear-to-branched structures was lowered from 1.17 to 0.70. We found that the more extensive branching of PEI enables the condensation of plasmid DNA into nanostructures with a size of 70-100 nm. The obtained complexes were stable at least for 3 weeks at 4 degrees C. The HD-DNA complexes prepared using secondary and tertiary amine-containing dendrons exerted a very low cytotoxicity in vitro during a coincubation with cells for 48 h. Using firefly luciferase as a marker of protein expression, we established that HD complexes were efficient in transfecting cells in the presence of serum. Under optimized conditions, the transfection activity at a nitrogen-to-phosphate (N/P) ratio of 6 was approximately six times higher than that of the commercially available polycationic transfection reagent. Bioluminescent imaging of in vivo gene expression using a luciferase reporter gene showed the increase of the signal in the liver and in submandibular lymph nodes in live mice. Our preliminary in vivo gene expression data demonstrates the potential of HD polymers as in vivo transfection agents that could be potentially useful for lymph node gene delivery.