Drug delivery

Nano-structured titania reservoirs are promising for drug delivery and are currently investigated to host valproic acid and phenytoine as anticonvulsant drugs for epilepsy.

The development of controlled drug delivery systems has received much attention in the last years, with the aim to reduce the dose and to administer the drug in a controlled way directed toward some specify tissue. The drug inclusion in a delivery system improves its terapeutic effectiveness, increases its stability reducing at the sametime side effects and the patient upset. The controlled drug delivery systems most used are polymeric nano- and micro-particles, including microspheres and microcapsules. More recently, inorganic porous materials are emerging as a new category of drug hosting systems: several mineral have been tested such as zeolithe, silica xerogels materials and porous ceramic. The success of the inorganic matrix as drug delivery sytem is determined by its capacity to control the release of the drug to the environment. The diffusion process depends on the structure and morphology of the system as well as on matrix-solute or matrix-solvent interactions.

The Ti-OH hydroxyl groups found in TiO2 xerogels can act as a water reservoir ehnancing the ability to maintain the biochemical activity of the entraped drug and giving high stability to the drug in the matrix. In addition, the water reservoirs allow high mobility of the drug to enviroment.

Drug release from a sustained release hydrophilic matrix shows a typical time dependent drug release profile. Upon contact with the dissolution medium, an initial bolus of the drug is released ("burst") followed by a progressive reduction of the release rate due to an increase of the diffusion pathlength: drug molecules located at the window of mesopores and adsorbed on the external surface are quickly released while the molecules into the mesopores are released later.

The sol-gel process is a low temperature route widely used to obtain TiO2 materials by differents applications. This method involves the hydrolysis and condensation of a metal alkoxide leading to the formation of hydrous oxide network. If the water/alkoxide molar ratio is modified, inorganic matrix with different hydroxilation degree is obtained.

Valproic acid (VPA) is a first-line antiepileptic drug that is effective in tonic-clonic, myoclonic, tonic and absence seizures and partial seizures as a second-line drug. However, its hepatotoxicity and teratogenicity are disadvantages that limit its chronic use. Incorporating VPA into the TiO2 matrix (during its preparation by sol-gel method) and finding a way to stabilize its properties and its realese allow to insert the TiO2-VPA delivery system directly in the brain, thus avoiding unwanted effects.