Molecular Dynamics Insights into Oil Droplet Adsorption and Penetration on the Stratum Corneum

Oil exposure represents a common environmental hazard that may compromise skin barrier function by disrupting the structural integrity of the stratum corneum (SC). Here, molecular dynamics (MD) simulations were employed to investigate the interactions between crude oil and the SC, aiming to elucidate how oil exposure impacts skin barrier function at the molecular level. The simulation results showed that the oil droplet rapidly adsorbed onto the SC within the first 1.0 ns upon contact. Permeation proceeded after the initial adsorption and spreading of the oil droplet and dominated the long-time dynamics of the system. Due to their larger molecular size and amphiphilic nature, asphaltene and resin molecules primarily remained at the SC-water interface, exhibiting limited permeability. Resin molecules showed distinct permeability despite comparable sizes, as heteroatom incorporation enhanced hydrophilicity and surface affinity, thereby hindering deeper penetration. In contrast, light crude oil molecules, characterized by their small size and hydrophobicity, penetrated deeply into the interior of the SC bilayer. Diffusion kinetics analysis revealed that the diffusion coefficients followed the order: light oil > resin > asphaltene, reflecting their relative mobility within the system. The high mobility of cholesterol (CHOL) molecules made them the most unstable components within the SC, playing a pivotal role in facilitating oil penetration. Upon interaction with oil droplet molecules, CHOL underwent a stepwise escape process from the bilayer, ultimately creating voids that promoted deeper oil ingress. This study provided detailed insights into how different crude oil components affect the structure and function of the SC, offering valuable guidance for developing strategies to protect the skin barrier.