  Cellular uptake of nanoplastics is instrumental in their environmental
accumulation and transfer to humans through the food chain. Despite extensive
studies using spherical plastic nanoparticles, the influence of the
morphological characteristics of environmentally released nanoplastics is
understudied. Using dissipative particle dynamics simulations, we modeled the
interactions between a cell membrane and hydrophobic nanotetrahedra, which
feature high shape anisotropy and large surface curvature seen for
environmental nanoplastics. We observe robust uptake of nanotetrahedra with
sharp vertices and edges by the lipid membrane. Two local energy minimum
configurations of nanotetrahedra embedded in the membrane bilayer were
identified for particles of large sizes. Further analysis of particle dynamics
within the membrane shows that the two interaction states exhibit distinct
translational and rotational dynamics in the directions normal and parallel to
the plane of the membrane. The membrane confinement significantly arrests the
out-of-plane motion, resulting in caged translation and subdiffusive rotation.
While the in-plane diffusion remains Brownian, we find that the translational
and rotational modes decouple from each other as the particle size increases.
The rotational diffusion decreases by a greater extent compared to the
translational diffusion, deviating from the continuum theory predictions. These
results provide fundamental insights into the shape effect on the nanoparticle
dynamics in crowded lipid membranes.
