Low-Dimensional Hollow Nanostructures: from Morphology Control to the Release of an Active Pharmaceutical Ingredient

The mechanism guiding the growth of hollow silica nanotubes or nanospheres was unveiled for the first time through in situ liquid-phase transmission electron microscopy, allowing visualization of the morphology of the hydrated species involved in the early stage of material formation. The combined action of a surfactant (F127) and a swelling agent (toluene) was essential for the development of targeted nanostructures, owing to the formation of surfactant-stabilized toluene droplets in the aqueous phase. The quantity of surfactant-stabilized toluene droplets was unambiguously pointed as the key parameter guiding the formation of either tubular or spherical nanostructures. Leveraging on the fundamental understanding of the parameters guiding the formation of hollow silica nanostructures, tubular and spherical carriers were prepared and exploited for the release of an active pharmaceutical ingredient (API). The impregnation of nanotubes and nanospheres with a poorly water-soluble API (curcumin) was investigated, leading to an optimal loading of 20 wt %. The accessibility of nanotubes and nanospheres showed to be highly beneficial to increase the release kinetics of the targeted API in simulated intestinal fluid, opening promising perspectives in the field. Release was more efficient than with other conventional mesoporous silica-based carriers.