Biocompatible silica nanoparticles conjugated with azidocoumarin for trace level detection and visualization of endogenous H 2 S in PC3 cells

Abstract The silica nanoparticles (SiO 2 NPs) conjugated with azidocoumarin (Cy-N 3 ) was applied for the selective and sensitive H 2 S detection, even when H 2 S was present in 1000-fold excess of other bio thiols and ions. In the silica nanoprobes, azide in the Cy-N 3 group acted as the recognition element, and the probe was biocompatible. The nanoprobe displayed blue emission at 456 nm and excitation at 367 nm. After introducing H 2 S into the probe solution, the fluorescent intensity at 456 nm increased linearly as a function of H 2 S concentration (correlation coefficient, 0.9970), and the limit of detection was 6 nM. The enhanced fluorescent emission intensity was due to H 2 S-mediated reduction of the electron-withdrawing azide into electron-donating amine. The SiO 2 NPs@Cy-N 3 and its reaction products with H 2 S (SiO 2 NPs@Cy-NH 2 ) were characterized by 1 H NMR and TEM. The probe also showed low cytotoxicity and could trace endogenous H 2 S in physiological pH. We therefore then successfully utilized it to detect H 2 S in living PC3 cells. The probe was also successfully employed for detection of H 2 S gas using Whatman papers coated with SiO 2 NPs@Cy-N 3 .