Molecular dynamics simulations of the interactions of charge-neutral PAMAM dendrimers with pulmonary surfactant

We have performed coarse grained molecular dynamics simulations (CGMD) to investigate the interactions of generation 7, 5 and 3 (G7, G5 and G3) charge-neutral polyamidoamine (PAMAM) dendrimers with a DPPC (dipalmitoylphosphatidylcholine) monolayer at the air-water interface (model pulmonary surfactant) during the end-expiration process. Our results show that different generations of PAMAM dendrimers have different influences on the DPPC monolayer. Generally, G3 PAMAM dendrimers show little influence on the DPPC monolayer's structure and relative properties. While G7 and G5 PAMAM dendrimers tend to induce the formation of largely deformed structures of the DPPC monolayer and inhibit or even reverse the normal phase transition of the interfacial DPPC molecules during the process of compression. Besides, we find that the formation processes of these disrupted structures are energy-favorable based on analyzing van der Waals interaction energy between PAMAM dendrimers and the whole system.