Controlled Release of Hydrophilic Drug from Hollow Nanodots

Here the challenge of limited encapsulation efficiency of ionizable hydrophilic molecules in silica materials is addressed. Two effective strategies are showcased that allow high encapsulation efficiency of salicylic acid, while simultaneously maintaining the morphology and particle size of silica nanocapsules. These promising approaches involve the formation and encapsulation of a prodrug or the complexation of the hydrophilic payload with a hydrophobic moiety to form a complex that is dissociated in acidic conditions. Well-defined core-shell silica nanocapsules with a diameter of 6 nm are obtained and exhibited an encapsulation efficiency of over 90%. High amounts of salicylic acid are released in acidic conditions from silica nanocapsules entrapping the prodrug or the complex, leading to pH-responsive characteristics. This work demonstrates promising strategies for the encapsulation and the controlled release of hydrophilic fertilizers, pesticides or drugs.