Biocompatible silica nanoparticles conjugated with azidocoumarin for trace level detection and visualization of endogenous H2S in PC3 cells

Abstract

The silica nanoparticles (SiO2NPs) conjugated with azidocoumarin (Cy-N3) was applied for the selective and sensitive H2S detection, even when H2S was present in 1000-fold excess of other bio thiols and ions. In the silica nanoprobes, azide in the Cy-N3 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 H2S into the probe solution, the fluorescent intensity at 456 nm increased linearly as a function of H2S concentration (correlation coefficient, 0.9970), and the limit of detection was 6 nM. The enhanced fluorescent emission intensity was due to H2S-mediated reduction of the electron-withdrawing azide into electron-donating amine. The SiO2NPs@Cy-N3 and its reaction products with H2S (SiO2NPs@Cy-NH2) were characterized by 1H NMR and TEM. The probe also showed low cytotoxicity and could trace endogenous H2S in physiological pH. We therefore then successfully utilized it to detect H2S in living PC3 cells. The probe was also successfully employed for detection of H2S gas using Whatman papers coated with SiO2NPs@Cy-N3.