A CuO-functionalized NMOF probe with a tunable excitation wavelength for selective detection and imaging of H2S in living cells.

Recently, fluorescent nanoscale metal-organic frameworks (NMOFs) have been proven to be useful probes for the detection and imaging of active biomolecules in living cells. However, the excitation wavelengths of these NMOF fluorescence probes are mostly in the ultraviolet region, which unavoidably results in reduced cell activity, limited tissue penetration depth and inevitable biological background interference. Herein, to solve this problem, a CuO functionalized NMOF probe with a tunable excitation wavelength based on Förster resonance energy transfer (FRET) for selective detection and imaging of the third important gaseous signaling molecule hydrogen sulfide (H2S) in living cells as an example is presented. In the energy transfer system, NMOF confines the luminophore organic dye thiazole orange within its intrinsic porous matrix as the energy donor, in which the excitation wavelength of the NMOF can be tuned simply from UV to Vis through the choice of dye molecules, and the H2S-responding site copper oxide nanoparticle (CuO NP) is the acceptor. After the surface functionalization of CuO NPs onto the NMOF, the fluorescence of the NMOF can be efficiently quenched based on the FRET. When H2S appeared, the fluorescence of the nanoprobe is recovered due to the interruption of FRET. This facile yet powerful strategy not only provides an instantaneous fluorescence probe for selective H2S detection in living cells but also offers a valuable approach for using porous NMOFs to sense other biological species.