Using ethidium bromide to probe the interactions between DNA and dendrimers

Investigations have been carried out to probe the interactions between double-stranded DNA and amine-terminated, ethylenediamine core polyamidoamine starburst dendrimers generation 2 (G2), generation 4 (G4), and generation 7 (G7). Ethidium bromide is used as a fluorescent probe for this study. Under our experimental conditions, the results show that there is mainly one binding mode between ethidium and DNA-dendrimer complexes and that dendrimers bind to DNA sufficiently strongly that they cannot be displaced by ethidium. In the proposed binding model for DNA-dendrimer complexes, the DNA wraps around G7 dendrimers while the wrapping of DNA does not occur for G2 and G4 dendrimers. DNA-dendrimer interactions display little preference on DNA base components. The influence of pH and ionic strength is in agreement with electrostatic interactions as the major binding force for DNA-dendrimer complexes.