Extraordinary sensitivity for H2S and Fe(iii) sensing in aqueous medium by Al-MIL-53-N3 metal–organic framework: in vitro and in vivo applications of H2S sensing

Abstract

An Al(III) metal–organic framework (MOF) called Al-MIL-53-N₃ (1) was synthesized under solvothermal reaction conditions using Al(NO₃)₃·9H₂O and H₂BDC-N₃ (H₂BDC-N₃ = 2-azido-1,4-benzenedicarboxylic acid) ligand in a DMF/water (DMF = N,N-dimethylformamide) mixture. Phase purity was checked by performing X-ray powder diffraction, infrared spectroscopy and thermogravimetric analysis. Thermogravimetric analysis suggests that 1 is highly stable up to 300 °C under air atmosphere. The activated 1 (called 1′) showed a very fast fluorescence response to H₂S (turn-on) and Fe(III) ions (turn-off) in an aqueous medium with excellent sensitivity and selectivity even in the presence of other potentially intrusive analytes. In the presence of H₂S, the conversion of the azide moiety to amine is responsible for the fluorescence turn-on properties. On the other hand, the partial replacement of framework Al(III) ions by Fe(III) can be assigned for the selective detection behavior to Fe(III) ions. The detection limits (90.47 nM for H₂S and 0.03 μM for Fe(III) ions in water) of 1′ are lower than those of the formerly reported MOF type of fluorescent sensors. The 1′-loaded J774A.1 macrophage cells are healthy and respond to intracellular H₂S to exhibit strong blue fluorescence, confirming its suitability to detect H₂S inside the cells. In addition, 1′ can detect H₂S in human blood plasma (HBP) and sulfide ions in real water samples. These features make 1′ a very promising candidate for the on-site sensing of Fe(III) ions and the detection of intracellular and extracellular H₂S.