Aim: To study freeze-drying of silica nanoparticles (SiO2NPs) in order to find suitable conditions to produce lyophilized powders with no aggregation after resuspension and storage.
Methods: SiO2NPs were synthesized using a Stöber-based procedure, and characterized by scanning electron microscopy, dynamic light scattering and nitrogen adsorption/desorption isotherms. SiO2NPs 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 SiO2NPs 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 SiO2NPs freeze-drying process to obtain redispersable solids that maintain original sizes without residual aggregation.
Keywords: colloidal stability; freeze-drying; inorganic nanoparticles; lyophilization; nanoparticle storage; nanoparticles; redispersibility; silica.