(363e) Adsorption and Denaturation of Polymeric Nanoparticles at an Interface

Chang Tian¹, Jie Feng¹, Robert K. Prud’homme¹

¹ Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, 08540

Understanding nanoparticle (NP) self-assembly at an interface is essential to control NP adsorption onto targeted areas and determine subsequent drug release kinetics. However, few studies have characterized the adsorption of NPs onto interfaces quantitatively. By looking at the dynamic surface tension change over time, we investigate air-water interfacial adsorption of NPs, which are made with a hydrophobic core and hydrophilic polyethylene glycol corona through the Flash NanoPrecipitation (FNP) process. By utilizing the maximum bubble pressure tensiometer, we are able to record surface tension over the scales from 100 ms to 30 s. Three stages were documented for NP adsorption, which includes an early stage of free diffusion, a later one with steric adsorption barriers and a hitherto unrealized region where adsorption energy sharply increases due to surface restructuring of NPs to expose their hydrophobic cores. By modifying the Ward and Tordai model, we collapsed curves of surface tension change for NPs of different concentrations and physical characteristics into one dimensionless “master curve” via time-concentration shifting. In addition, we have analyzed the kinetics of NP adsorption in the presence of types of surfactants. Surfactants usually decrease the surface energy of an interface. However, we have observed phenomena where surfactants slow down the NP adsorption kinetics so as to raise the surface tension compared to that of a system with NPs alone. We have shown that this change of adsorption kinetics depends on the surfactant charge (anionic, cationic or non-ionic) as well as the formulation of NPs. A detailed mechanism is proposed to explain this NP-surfactant interaction.