Poly( L ‐histidine) with several aminoethyl groups for a new pH‐sensitive DNA carrier

In this study, poly(L‐histidine) with several aminoethyl groups, i.e. aminated poly(L‐histidine), is reported to be able to make complexes with DNA and to transfect cells in vitro in the presence of serum. The present study was performed to determine whether the pH of the medium had an influence on the complex formation with DNA, on the cell membrane fusion activity and on the transfection efficiency. Agarose gel retardation assays proved that the polyion complex formation of the aminated poly(L‐histidine) with DNA was affected by pH of the medium, owing to the basicity (protonation–deprotonation) of the imidazole groups with a pKa value around 6.0. Hemolysis assay showed that the resulting DNA complex enhanced membrane disruptive ability at endosomal pH. The aminated poly(L‐histidine) gene carrier demonstrated significant transfection efficacy which was decreased by the inclusion of chloroquine as an endosomolytic agent. These results suggest that the aminated poly(L‐histidine) promises to be a new pH‐sensitive DNA carrier for endosomal escape.