Interaction of G‐quadruplex Forming DNA Aptamers with PAMAM Dendrimers Studied by Dynamic Light Scattering and UV‐VIS Spectrophotometry**

Abstract

The complexes of G‐quadruplex forming DNA thrombin binding aptamers (TBA) and polyamidoamine dendrimers (PAMAM) were studied with the aim to form a model targeted drug delivery system. Hydrodynamic diameter, zeta potential and melting temperature (Tm) were investigated by dynamic light scattering and UV‐VIS spectrophotometry. Non‐covalent adsorption by means of electrostatic interaction between positively charged amino groups of dendrimers (+) and negatively charged phosphate groups of aptamers (−) has driven the formation of aggregates. The size of complexes was in the range of 0.2–2 μm and depended on the type of dispersant, charge ratio (+/−) and temperature. Raising the temperature increased the polydispersity, new smaller size distributions were observed indicating the G‐quadruplex unfolding. The melting transition temperature of TBA aptamer was affected by the presence of amino‐terminated PAMAM rather than carboxylated succinic acid PAMAM−SAH dendrimer, thus supporting the electrostatic nature of interaction that disturbed denaturation of target‐specific quadruplex aptamer structure.