TiO2-coated pSi microparticles for nanomedicine

Porous silicon (pSi) is a sponge-like material that, due to quantum confinement effect, is photoluminescent when excited by UV light. We developed a process to obtain mesoporous silicon microparticles by electrochemical etching and we proved them to be optically stable in biological buffers once opportunely coated. This material is a promising system for nanomedicine application, first, because it is biodegradable, biocompatible and not activator of the immune response, then, since the porosity and the photoluminescence make them suitable for drug delivery and bioimaging. The microparticles were coated by ALD (atomic layer deposition) in a rotary reactor to avoid optical and structural degradation in aqueous media. A thin and uniform TiO2 layer was deposited on the pSi microparticles (pSi-TiO2 microparticles), without occluding the pores. In-vitro tests were performed to control the effect of pSi-TiO2 microparticles on human dendritic cells (DCs). We observed no decrease of cell viability after the internalization of the microparticles that maintained their PL, as can be seen in Figure 1, but an increase of the immune response (priming effect) in case of co-stimulation with an immune response activator. These preliminary results, recently published, are promising for the pSi-TiO2 microparticles application in nanomedicine, in particular, for drug delivery and bioimaging.