Hybrid particles for vitamin D3 release in view of psoriasis treatment

One of the main applications for nanotechnologies in biomedical field is the preparation of drug delivery systems to have a controlled release of the drug to treat a disease and to limit the possible side-effects of the conventional treatments. The goal of this thesis work is synthesizing mesostructured silica hybrid systems for the vitamin D3 release for the topical treatment of psoriasis: vitamin D3 is an organic molecule produced by the skin that stimulates the cell differentiation, limiting the psoriasis effects. In order to overcome the problems related to the poor bioavailability of vitamin D3 due to its lipophilic behaviour, it is possible to exploit mesostructured silica particles as carriers, taking advantage of their ordered structure, high surface area and biocompatibility. In this experimental work, a bottom-up approach is exploited to incorporate drug inside the mesostructured silica particles. This process consists in self-assembled surfactant molecules (CTAB) that form micelles, which act as templating agent and drive the deposition of the silica precursor (TEOS). These particles are composed by an amorphous silica matrix, which allows the vitamin D3 incorporation inside the surfactant micelles. Three different syntheses are performed varying the vitamin D3/surfactant ratio and, then, the samples are characterized by using different techniques. In particular, UV spectroscopy is exploited to study the drug quantity extracted in ethanol. This test demonstrates that the vitamin D3/surfactant ratio affects the incorporation process: lower this ratio, higher the percentage of incorporated drug. However, the synthesized hybrid system reveals a good incorporation efficiency in all the three cases. Moreover, the comparison between the results of XRD analyses related to the first and second syntheses demonstrates that, by using a higher quantity of vitamin D3, the particle structure is transformed from hexagonal (for a lower vitamin D3 amount) to a mixed phase (lamellar and hexagonal). The XRD result related to the third sample, instead, does not show the presence of a specific phase, but only a disordered structure: this proves the importance of the CTA, in fact, by reducing the CTA amount in synthesis, the produced particles do not have an order anymore. Finally, a release test is performed in artificial sweat to evaluate the release kinetics of vitamin D3 in time and to know the released drug quantity at the end of the process. This experimental work demonstrates that: - Vitamin D3 is involved in the construction of the structure symmetry of the particles, acting as a co-templating agent. Hence, varying its amount in synthesis, it is possible to change the particle phase. - The particle structure affects the drug release kinetics; in particular, the hexagonal phase grants a released drug quantity higher than in the case of mixed phase. On the other hand, an ordered phase is important: in fact, the particles with a disordered structure show the lowest released drug quantity. - However, in all the cases, the incorporation efficiency of vitamin D3 inside the particles is high, about 90%, and no vitamin D3 waste is produced. - Silica particles have a low release quantity of vitamin D3 in artificial sweat. Furthermore, during the release process not only the drug is released, but also the surfactant. Hence, in future studies it would be interesting trying to synthesize hybrid systems using a surfactant less toxic than CTAB.