Interaction of PAMAM dendrimers with bovine insulin depends on nanoparticle end-groups

We have looked at the interactions between polyamidoamine (PAMAM) dendrimers with different terminal groups (COOH, NH2, OH) and bovine insulin. The influence of PAMAM dendrimers on insulin was tested by measuring zeta potential and fluorescence quenching. The secondary structure of insulin in the presence of dendrimers was examined by circular dichroism. The effect of dendrimers on dithiotreitol-induced aggregation of insulin was investigated by spectrophotometry. Dendrimers quenched the fluorescence of insulin, but did not change its secondary structure. Thus dendrimers neither induce hormone aggregation nor inhibit the aggregation process induced by dithiotreitol (DTT), except at 0.01 µmol/l. Dendrimers-insulin interactions are mainly electrostatic.