Nanostructured silicon particles for medical applications.

Porous silicon (PS) which has different properties from the bulk material due to the quantum confinement effects is beside other physical properties (e.g., light emitting) bioactive or even bioresorbable. The aim of this paper is to optimise the experimental conditions for the fabrication of nanostructured Si particles and to find the best methods for attaching on its surface molecules of therapeutic interest. The selective porosification has been performed using (i) a dielectric/metallic masking layer micropatterned with corresponding etching windows; (ii) a controlled diffusion process leading to n-type islands into p-type Si substrate. The PS particles were detached from the Si substrate by switching the electrochemical etching conditions from porosification towards the electropolishing regime. Also, similar results were obtained by fabrication of PS multilayer structures subjected to an additional ultrasonation process. Different organic molecules with antitumoral effect, such as chondroitin sulphate (a sulphated glycosaminoglycan), lactoferrin (globular protein with antimicrobial activity) and N-butyldeoxynojirimycin (an imino sugar that inhibits the growth of the CT-2A brain tumour) were covalently attached on the PS particle surface using 3-aminopropyltriethoxysilane (APTS) molecule as linker. Furthermore, to complete the administration/therapy of drugs, for microparticle targeting and imaging, Fe3O4 nanoparticles were integrated in PS matrix by co-precipitation from a solution of iron salts (Fe3+/Fe2+) in alkaline medium. Microscopic and spectroscopic analyses have been used to characterize the Si microparticles. Tumoral cells were cultivated on the nanostructured PS particles and a significant decrease of the cells density was observed on all investigated samples comparatively with the blank substrate without antitumoral molecules.