The order affects the release of vitamin D from hybrid self-assembled silica systems

Vitamin D (VD) suffers from low water solubility and strong degradation, which both decrease its bioavailability. This work aims at obtaining a silica-surfactant-VD hybrid material and verifying if this system can protect VD from degradation and enhance its solubility. This preliminary study aspires at tuning the mesostructure order of the hybrid system (by modifying the surfactant amount) with the scope of controlling, somewhat, its drug release capability. To this purpose, two silica-surfactant-VD systems with different long-range order were synthesized and characterized in terms of physico-chemical properties and release behavior in a model solution mimicking the topical environment. Results show that the hybrid materials are able to incorporate VD, protect it from degradation up to 17 months and release it in aqueous media. The mesostructure order and the interaction between VD, surfactant and silica seem to play a key role in tuning kinetics and the amount of released drug. While the less ordered structure incorporates less VD with faster and higher release percentage, the more ordered one incorporates more VD but, due to the stronger interactions with the carrier, requires a partial dissolution of the matrix to occur before releasing the drug, so inducing a lag-time and a smaller released quantity.