Bio-inspired systems for metal ion sensing : new emissive peptide probes based on benzo[d]oxazole derivatives and their gold and silica nanoparticles

Abstract

Seven new bio-inspired chemosensors (2-4 and 7-10) based on fluorescent peptides were synthesized and characterized by elemental analysis, 1H-NMR, 13C-NMR, melting point, matrix assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS), infrared, UV-vis absorption and emission spectroscopy. The interaction with transition and post-transition metal ions (Cu2+, Ni2+, Ag+, Zn2+, Cd2+, Hg2+, Pb2+ and Fe3+) has been explored by absorption and fluorescence emission spectroscopy and MALDI-TOF mass spectrometry. The reported fluorescent peptide systems, introducing biological molecules in the skeleton of the probes, enhance their sensitivity and confer them strong potentials for applications in biological fields. Gold and silica nanoparticles functionalized with these peptides were also obtained. All nanoparticles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-vis absorption and fluorescence spectroscopy. Stable gold nanoparticles (diameter 2-10 nm) bearing ligands 1 and 4 were obtained by common reductive synthesis. Commercial silica nanoparticles were decorated at their surface using compounds 8 to 10, linked through a silane spacer. The same chemosensors were also taken into aqueous solutions through their dispersion in the outer layer of silica core/PEG shell nanoparticles. In both cases, these complex nanoarchitectures behaved as new sensitive materials for Ag+ and Hg2+ in water. The possibility to use these species in this solvent is particularly valuable since the impact on human health of heavy and transition metal ions pollution is very severe, and all analytical and diagnostics investigations involve a water environment.