Molecular Characterization of Mesoporous Silica (Un)loading by Gemcitabine and Ibuprofen - An Interplay of Salt-Bridges and Hydrogen Bonds.

The molecular mechanisms of mesoporous silica nanomaterial (MSN) loading by gemcitabine and ibuprofen molecules, respectively, are elucidated as functions of pore geometry. Based on a small series of MSN archetypes, we use molecular dynamics simulations to systematically explore molecule-by-molecule loading of the carrier material. Apart from predicting the maximum active pharmaceutical ingredient (API) loading capacity, more detailed statistical analysis of the incorporation energy reveals dedicated profiles stemming from the interplay of guest-MSN salt-bridges/hydrogen bonding in concave and convex domains of the silica surfaces - which outcompete interactions among the drug molecules.

Molecular Dynamics Simulations of Nitrate/MgO Interfaces and Understanding Metastability of Thermochemical Materials.

We explore the role of molten nitrate interfaces on MgO surface treatment for improving the reversibility of thermochemical energy storage via sorption and desorption of water or CO. Our molecular dynamics simulations focus on melts of LiNO, NaNO, KNO, and the triple eutectic mixture LiNaKNO on the surface of MgO to provide atomic scale details of adsorbed layers and to rationalize interface energies. On this basis, a thermodynamic model is elaborated to characterize the effect of nitrate melts on the dehydration of Mg(OH) and to quantitatively explain the difference in dehydration temperatures of intact and LiNO-doped Mg(OH).

Interface between Water-Solvent Mixtures and a Hydrophobic Surface.

The mechanism behind the stability of organic nanoparticles prepared by liquid antisolvent (LAS) precipitation without a specific stabilizing agent is poorly understood. In this work, we propose that the organic solvent used in the LAS process rapidly forms a molecular stabilizing layer at the interface of the nanoparticles with the aqueous dispersion medium. To confirm this hypothesis, -octadecyltrichlorosilane (OTS)-functionalized silicon wafers in contact with water-solvent mixtures were used as a flat model system mimicking the solid-liquid interface of the organic nanoparticles.

On the Role of Silica Carrier Curvature for the Unloading of Small Drug Molecules: A Molecular Dynamics Simulation Study.

We present atomic scale models of differently shaped silica surfaces loaded by gemcitabine and ibuprofene molecules. Despite the dissimilar nature of the drug molecules, their association to silica carriers shows quite similar characteristics. We identify a well-defined contact layer that is stabilized by silica-molecule salt-bridges/hydrogen bonding in parallel to interactions among the drug molecules.

Molecular mechanisms of mesoporous silica formation from colloid solution: Ripening-reactions arrest hollow network structures.

The agglomeration of silica nanoparticles in aqueous solution is investigated from molecular simulations. Mimicking destabilization of colloidal solutions by full removal of protective moieties or surface charge, association of SiO2/Si(OH)4 core/shell particles leads to rapid proton transfer reactions that account for local silanole → silica ripening reactions. Yet, such virtually barrier-less binding is only observed within a limited contact zone.