CONICET | Buscador de Institutos y Recursos Humanos

A nanosensor based on β-cyclodextrin (βCD) macrocycles linked to gold nanoparticles for rhodamine B (RhB)sensing was developed applying the metal-enhanced fluorescence effect (MEF). Hence, we have developedmany ways to control the distance of supramolecular systems to nanoparticle surface with differentbioconjugation strategies in order to optimize signal detection. Different PEG spacer arm lengths were used tocover the nanoparticle surface with molecular spacers. This type of molecular shell is biocompatible, enablingto switch on/off the MEF effect using a dithiane linker by a simple reduction reaction. In the presence of thenanosensor obtained, an increase was observed in RhB fluorescence emission depending on molecular length,that is a characteristic effect ofMEF. Themajor increasemeasuredwas 60% comparedwith RhB emission in bufferat 1 nMlevel, for a spacer length of 3.58 nm and an 80% increase as compared with that in the presence of βCD.These differences are ascribed to the fact that, in the presence of macrocycle, we can observe a well-knownquenching effect that is overcome by the presence of the metallic core. Even at shorter spacer distances, withPEG lengths of 1.2 and 2.17nm, increases of 25 and 47% respectively allowthe analyte detection by the RhB complexationwith βCD. The optimal MEF enhancement was measured with the maximal emission signal stabilizedafter 50 min due to plasmonic effects based on inter nanoparticle interactions. Moreover, the emission increase,in the presence of the metallic core, was accompanied with a diminution in the fluorescence lifetime´s decayvalue averages, characteristic of MEF. This fact shows that the excited state is protected from the non-radiativeemission decays enhancing the analytical signal.