Iron oxide/PAMAM nanostructured hybrids: combined computational and experimental studies

Recent studies in the field of iron oxide-dendrimer hybrids showed an increased potential of these materials to be used in diagnosis, monitoring, targeting, and therapy of cancer. The aim of this paper is to investigate the nature of interactions between iron oxide nanoparticles and polyamidoamine (PAMAM) dendrimers using computational and experimental techniques, namely molecular dynamics (MD) and electron paramagnetic resonance (EPR). Hybrid nanostructures based on iron oxide and PAMAM dendrimers were prepared in one-step synthesis route, using hydrothermal method at high pressure (40-100 atm). The interaction between dendrimers and iron oxide nanoparticles was predicted at specific temperature, pH, and pressure conditions. The same conditions were applied for hydrothermal synthesis. High-resolution transmission electron microscopy revealed the formation of magnetite (MAG) through hydrothermal reaction at 100 atm, starting only from iron (III) chloride. A possible explanation could be the variation of the fugacity value of oxygen under high-pressure conditions, which leads to diffusion-controlled reaction and to transformation of haematite into MAG. EPR parameter, namely linewidth, was exploited to evaluate the type of interactions from iron oxide-PAMAM hybrids, due to its dependence on spin-spin relaxation time and spin-lattice interactions. As a conclusion, MD indicated the existence of electrostatic interactions between PAMAM and iron oxide. In accordance with in silico results, EPR analysis suggested that MAG is not entrapped in PAMAM structure and the interactions between organic and inorganic components take place at dendrimer's surface. A good agreement between MD simulations and experimental results was observed.