Poly(amidoamine) (PAMAM) dendrimers have been identified as potential gene vectors. We have studied their association with surfactants, dilauroylphospholiponucleosides (DLPN), with a nucleobase polar head that triggers molecular recognition of DNA and RNA. The interactions of DLPN with pre-adsorbed PAMAM monolayers on silica have been investigated with quartz crystal microbalance with dissipation monitoring (QCM-D), showing the formation of a rigid layer, apparently independent of the DLPN concentration, and a partially irreversible adsorption, but the structure and composition of the layers are not accessible with QCM-D. We aim to investigate the interactions PAMAM/DLPN on silica using neutron reflectivity (NR) at INTER. We plan to employ isotopic solvent contrasts to characterize the adsorbing layers through the simultaneous fittings of corresponding NR profiles in different contrasts.