In an attempt to circumvent toxic effects of branched polyethylenimine (bPEI, 25 kDa), it was crosslinked with varying proportions of a novel linker, PEG600-bis(aminoethylphosphate) (PaP), which resulted in the formation of nanoparticles (PPaP) in the range of 61–99 nm. These nanoparticles were found to have significantly lower toxicity in vitro than the native PEI. GFP expression in cells mediated by PPaP (8.1%)/DNA complex was found to be ∼1.1–4.8 folds higher compared to GenePORTER 2™, Lipofectamine™, Superfect™ and native PEI in HeLa, HEK293 and CHO cells. FACS analysis on HeLa cells revealed ∼62% transfected cells, whereas, in the case of the GenePORTER 2™ transfection reagent, transfected cells were found to be ∼36%. Intracellular trafficking in HeLa cells showed a significant population of PPaP (8.1%) nanoparticles and their DNA complex in nucleus after 1 h of treatment. Also, efficient delivery of GFP specific siRNA resulted in ∼71% suppression of the target gene. DNase protection assay revealed that ∼78% of complexed DNA was protected by PPaP(8.1%) nanoparticles even after 2 h of treatment. In vivo transgene expression studies in Balb/c mice showed significantly higher expression in the spleen. The results advocate the potential of PPaP nanoparticles as efficient carriers of nucleic acids in vivo.
