BIOSILICA NANOVECTOR FROM DIATOMITE FOR siRNA TRANSPORT IN CANCER CELL

Diatomite is a natural porous biomaterial of sedimentary origin, formed by fragments of diatom siliceous skeletons, called "frustules". Due to large availability in many areas of the world, chemical stability, and non-toxicity, these fossil structures have been widespread used in a lot of industrial applications, such as food production, water extracting agent, production of cosmetics and pharmaceutics. However, diatomite is surprisingly still rarely used in biomedical applications. In this study, the properties of diatomite nanoparticles as potential system for the delivery of anticancer molecules in cancer cells were exploited. A purification procedure, based on thermal treatments in strong acid solutions, was used to remove inorganic and organic impurities from diatomite and to make them a safe material for medical applications. The micrometric diatomite powder was reduced in nanoparticles by mechanical crushing, sonication, and filtering. Morphology and composition of diatomite were investigated by scanning electron microscopy equipped by energy dispersive X-ray spectroscopy, photoluminescence and dynamic light scattering measurements. In-vitro experiments show a very low toxicity on exposure of the cells to diatomite nanoparticle concentration up to 300 ?g/ml for 72 h. Diatomite nanoparticles were functionalized by 3-aminopropyltriethoxysilane and labeled by tetramethylrhodamine isothiocyanate. Different concentrations of chemically modified nanoparticles were incubated with cancer cells and confocal microscopy was performed. Imaging analysis showed an efficient cellular uptake and homogeneous distribution of nanoparticles in cytoplasm and nucleus, thus suggesting their potentiality as nanocarriers for drug delivery. Subsequently, siRNA bioconjugation were performed and confocal microscopy imaging on cancer cells incubated with siRNAconjugated nanoparticles demonstrated a cytoplasmatic localization of vectors. Gene silencing by delivered siRNA was also demonstrated. Our studies endorse diatomite nanoparticles as non-toxic nanocarriers for siRNA transport in cancer cells. siRNA-diatomite nanoconjugate may be well suited for delivery of therapeutic to cancer cells.