Polyethyleneimine-grafted hyperbranched conjugated polyelectrolytes: synthesis and imaging of gene delivery

We report for the first time the synthesis of polyethyleneimine (PEI) grafted hyperbranched conjugated polyelectrolytes (HCPEs) and demonstrate their applications as gene vectors and fluorescent contrast agents for imaging of gene delivery. The HCPE was synthesized via a facile cyclotrimerization reaction catalyzed by CpCo(CO)2. Two low molecular weight PEIs, PEI600 or PEI1800 were used to conjugate to HCPEs and the HCPE–PEI conjugates were found to show low cytotoxicity, and strong ability to condense plasmid DNAs at low N/P (the moles of the amine groups of cationic polymers to those of the phosphate ones of DNA) ratios (1 or 2). The formed nanoparticles have sizes of ∼70 to ∼150 nm with positive zeta potentials, which facilitate cellular uptake. Furthermore, the successful uptake of HCPEs–DNA polyplexes was clearly observed by confocal fluorescence microscopy due to the intrinsic fluorescence from the HCPE cores. This study highlights the strategy of utilizing HCPEs as a fluorescent core to construct star-burst polyethyleneimines gene vectors for simultaneous transfection and imaging functions.