Rapid and highly sensitive detection of extracellular and intracellular H₂S by an azide-functionalized Al(iii)-based...

A new, azide-functionalized Al(iii)-based metal-organic framework (MOF) denoted as CAU-10-N₃ (1, CAU = Christian-Albrechts-University) and consisting of the 5-azido-isophthalic acid (H₂IPA-N₃) ligand was employed as a reaction-based fluorescent turn-on probe for the detection of H₂S. The activated compound (1') showed fast, selective and highly sensitive sensing properties for extracellular H₂S in HEPES buffer (10 mM, pH = 7.4). The material retained its high selectivity even in the presence of possibly competing biological species. The limit of detection of 1' for H₂S is 2.65 μM, which is lower than the earlier reports on MOFs for H₂S sensing. The material displayed a short response time (420 s) and a significant increase (20-fold and 26-fold after 1 and 7 min of addition of Na₂S, respectively) in the fluorescence intensity towards H₂S. Macrophage cells loaded with probe 1' exhibited blue fluorescence with a response time of 15 min after Na₂S addition, indicating the suitability of the probe for intracellular H₂S detection. Moreover, CAU-10-N₃ featured excellent detection performance (quick response and 32-fold increment in fluorescence intensity after 7 min of Na₂S addition) in water. Hence, it can be utilized to regulate the H₂S level in aqueous samples collected from the environment.