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

AIM: To study freeze-drying of silica nanoparticles (SiO2 NPs) in order to find suitable conditions to produce lyophilized powders with no aggregation after resuspension and storage.

METHODS: SiO2 NPs were synthesized using a Stöber-based procedure, and characterized by scanning electron microscopy, dynamic light scattering and nitrogen adsorption/desorption isotherms. SiO2 NPs 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 SiO2 NPs 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 SiO2 NPs freeze-drying process to obtain redispersable solids that maintain original sizes without residual aggregation.