Functionalized Hybrid Nanoparticles and their Interaction with Spin-Labeled Cyclodextrin

Hybrid nanoparticles of the gold@silica and magnetite@silica type were obtained by embedding gold nanoparticles (protected by captopril, average size 2.3 nm) or magnetite nanoparticles (protected by alanine, average size 10 nm) into larger silica nanoparticles (50-100 nm) using the Stober method. A silica precursor, i.e., a mixture of tetramethoxysilane and 3-aminopropyl-trimethoxysilane (in a 10/1 ratio), was used in order to facilitate the links between inner nanoparticles and the silica layer. These nanoparticles containing free amino-groups were easily functionalized with adamantane, naphtyl and nitrobenzofurazan moieties using appropriate reagents (adamantane-1-carbonylchloride, 1-naphtylisocyanate, and 7-chlor-4-nitrobenzofurazan). The hybrid nanoparticles were characterized by different means (IR and TEM) and their interaction with spin-labeled beta-cyclodextrin was also studied (by EPR spectroscopy). EPR spectra show that cyclodextrins are attached to the nanoparticles surface. The hybrid nanoparticles functionalized with nitrobenzofurazan moieties have the largest interaction with the cyclodextrin cavity.