Freeze-drying of silica nanoparticles: redispersibility toward nanomedicine applications.

Aim: To study freeze-drying of silica nanoparticles (SiONPs) in order to find suitable conditions to produce lyophilized powders with no aggregation after resuspension and storage.

Methods: SiONPs were synthesized using a Stöber-based procedure, and characterized by scanning electron microscopy, dynamic light scattering and nitrogen adsorption/desorption isotherms. SiONPs hydrodynamic diameters were compared prior and after freeze-drying in the presence/absence of carbohydrate protectants.

Results: Glucose was found to be the most suitable protectant against the detrimental effects of lyophilization. The minimum concentration of carbohydrate required to effectively protect SiONPs from aggregation during freeze-drying is influenced by the nanoparticle's size and texture. Negligible aggregation was observed during storage.

Conclusion: Carbohydrates can be used during SiONPs freeze-drying process to obtain redispersable solids that maintain original sizes without residual aggregation.