Interactions of Amphiphilic Janus Nanoparticles with Lipid Monolayers

Interaction of nanoparticles (NP) with the lungs is an important field of study for controlling and understanding airborne nanotoxicity, as well as for advancing pulmonary drug delivery. In particular, NP interactions with lung surfactant (LS) films have been studied using experimental and computational means for particles of various physicochemical characteristics such as size, shape, and hydrophobicity. However, the dynamics of adhesion and encapsulation of heterogeneous NPs by biointerfaces remain poorly understood. In this work, we explore the effects of amphiphilic Janus NPs (JNPs) on lung surfactant films using dissipative particle dynamics (DPD) simulations. With a specially parametrized DPD model (Santo et al., Colloids and Surfaces A, 725, 137623 (2025)), we investigate the interfacial dynamics and interaction mechanisms of JNPs with model lung surfactant monolayers consisting of dipalmitoylphosphatidyl choline (DPPC) lipids. We find that the interaction of JNP with DPPC monolayers at a given surface density depends on the particle hydrophobic coverage and its initial orientation, resulting in three distinct scenarios: translocation, monolayer coating, and intercalation between the lipids as another amphiphilic entity. The surface pressure of the monolayer is found to increase nonmonotonically with JNP hydrophobic coverage, reaching a maximum at about 50% coverage. Interestingly, the surface pressure of a JNP-monolayer system is found to be similar to that of a pure monolayer at an effective area that excludes the JNP at the interface. Our simulation results elucidate the dynamics of JNP-lipid monolayer interactions and provide quantitative insights into how NPs of different surface chemistries could affect the functionality of LS films.