# Interactions of Amphiphilic Janus Nanoparticles with Lipid Monolayers

## TL;DR

This study uses simulations to explore how Janus nanoparticles interact with lung surfactant films, revealing how their surface properties affect these interactions.

## Contribution

The paper introduces a parametrized simulation model to study the dynamic interactions of amphiphilic Janus nanoparticles with lipid monolayers.

## Key findings

- JNPs interact with DPPC monolayers in three distinct ways: translocation, coating, and intercalation.
- Surface pressure increases nonmonotonically with JNP hydrophobic coverage, peaking at 50%.
- The surface pressure of the JNP–monolayer system matches that of a pure monolayer excluding the JNP.

## Abstract

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.