Ferrocene-grafted polyethyleneimine (PEI-Fc) was synthesized via the reaction of ferrocene carboxaldehyde with branched PEI.The graft level of Fc was about 8.35%.Based on the host-guest interaction between ferrocene and -cyclodextrin (CD)

CD-modified PEI was successfully prepared.1H-NMR spectrum indicated that there were 26 CD molecules per PEI-Fc chain.CD-modified PEI via host-guest interaction showed effective DNA condensation ability.At N/P ratio above 3

the positive nanoparticles with diameter of about 150~250 nm were formed.At the cell culture medium of DMEM with 10% FBS

PEI-Fc/CD/DNA polyplexes showed excellent stability.It was probably due to the electronic adsorption of proteins on the surface of polyplexes.HEK293 cells culture results indicated that the transfection of PEI-Fc/CD/DNA polyplexes at N/P ratio of 3

5 and 10 was almost 2~3 folds of that of PEI polyplexes at N/P ratio of 10.The CD modified PEI via host-guest interactions significantly improved the transfection efficiency.