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.