bPEI (polyethylenimine, 25 kDa, gold standard) is highly effective in transfection efficiency owing to its high buffering capacity, however, cytotoxicity limits its use in in vivo applications. We hypothesized that partial conversion of secondary amines in IPEI to tertiary amines, while preserving the overall number of amines, would result in improved buffering capacity, which may, in turn, improve transfection efficiency of the resulting nanoparticles with cell viability comparable to that of native IPEI. IPEI was crosslinked with BDE to obtain a series of IPEI nanoparticles (LPN-1 to LPN-8) which were obtained in approximately 80-85% yield. These particles were relatively non-toxic in vitro and in vivo. In vivo gene expression studies using LPN-5 in Balb/c mice through i.v. injection showed maximum expression of the reporter gene in the spleen. These results demonstrate the potential of these particles as efficient transfection reagents.