Silica particles convert thiol-containing molecules to disulfides.

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Synthetic amorphous silica is widely used in food, cosmetics, and drug delivery due to its unique properties.
• Pure silica nanomaterials are generally considered chemically inert.
• The potential reactivity of silica surfaces in aqueous environments remains an area of interest.

Purpose of the Study:

• To investigate the potential for pure silica particles to facilitate chemical reactions.
• To explore the oxidation of thiol-containing molecules in the presence of mesoporous silica.
• To elucidate the mechanism behind silica-mediated oxidation.

Main Methods:

• Incubation of three thiol-containing molecules (L-cysteine, glutathione, D-penicillamine) with mesoporous silica particles.
• Monitoring oxidation yields over time and under varying conditions (e.g., dark, room temperature).
• Utilizing density functional theory (DFT) calculations to model reaction pathways and radical formation.

Main Results:

• Over 95% oxidation of thiol compounds occurred within 24 hours of incubation with mesoporous silica in the dark.
• Oxidation yields increased with incubation time and were higher for silica particles with larger surface areas.
• DFT calculations identified plausible pathways for the generation of silyloxy radicals (SiO•) on silica surfaces.

Conclusions:

• Pure silica particles are not entirely inert and can actively facilitate the oxidation of certain molecules.
• The silyloxy radical (SiO•) on silica surfaces is proposed as the key species mediating this oxidation.
• Understanding this reactivity is crucial for applications involving silica nanomaterials in biological and chemical systems.