Modeling of Lipid Assemblies on Porous Silicon Nanoparticles

Porous silicon nanoparticles are used as drug delivery materials. To improve their in vivo performance, they are often created with a lipid layer coating on the exterior of the nanoparticle. To enable self-assembly of the lipids around the nanoparticles, the surface of the nanoparticle is prepared with either a hydrophilic or a hydrophobic chemistry.

Previously, we hypothesized that the hydrophobic particles would form a monolayer of lipids, while the hydrophilic particles would be enveloped in a bilayer. But the actual interactions are in reality not known.

Our objective for this project is to visualize lipid layers associated with these models. Specifically, we aim to understand the preferred configuration of lipid molecules when interacting with either hydrophobic or hydrophilic particles, starting with preliminary classical experiment interactions. This project intends to show these assumptions using model generating softwares and molecular dynamic simulations.

We generated two simplistic models of these nanoparticles. First, a porous silicon slab with surface-conjugated alkyl chains serves as a model for hydrophobic interactions; and second, a porous silicon slab with hydroxyl groups on its surface is used to represent the hydrophilic model.

We will then run molecular simulations and then visualize these simulations to model the interaction energy between the porous silicon nanoparticle surface, the lipid molecules, and water molecules in the system. The ultimate goal of this research is to develop a reliable computational system that can accurately model more complex drug delivery systems, including those with intricate lipid layer compositions or those incorporating various ligands and ion channels. This project focuses on the first aspect of this goal, where we visualize the change in energy depending on the distance of the monolayer or bilayer from the modified surface.