Drug delivery from structured porous inorganic materials

Structured porous inorganic materials show high chemical and mechanical stability under an array of physiological conditions. Their hydrophilic character and porous structure can in principle be tailored to control the diffusion rate of an adsorbed or encapsulated drug, gene, or protein. This organized porosity has been used to achieve a sustained, controlled, or pulsed release in drug delivery applications. Their large surface areas together with their large pore volumes have been used to improve the solubility of poorly soluble drugs. Their low density allows them to float in the gastrointestinal tract and prolong the gastric retention of oral drugs. In addition, their easy surface functionalization allows their grafting with bioadhesive and targeting moieties, and their interior pore volume protects biological payloads from physiological degradation. Some of those porous inorganic materials can be synthesized or microfabricated to form deposits thus acting as drug reservoirs. Finally, diffusion-controlling porous membranes or coatings of those materials can be tailored with specific pore sizes to control drug release in eluting devices. Current research is focused on designing on demand targeted drug delivery systems using those inorganic porous materials as reservoirs together with triggering systems on their pore entrances to be externally activated to release the encapsulated therapeutic moiety. All of the previous scenarios will be overviewed to demonstrate the numerous possibilities of structured porous inorganic materials in drug delivery applications. WIREs Nanomed Nanobiotechnol 2012, 4:1630. doi: 10.1002/wnan.132