Metal-Organic Frameworks for the Quantitative Detection of Endogenous H2S
Résumé
According to the World Health Organization, the four major non-communicable diseases (NCDs) (cardiovascular disease, cancer, chronic respiratory diseases and diabetes) are responsible for 82% of NCDs deaths which corresponded to 31 million deaths in 2012. The past few years saw the increased number of scientific articles relating the intimate correlation between the clinical signs of these NCDs and Down syndrome and the blood or cerebral concentration of endogenous hydrogen sulfide.The determination of the blood level of hydrogen sulfide is thus a challenge in order to make early diagnostic and to build up a treatment protocol before the appearance of clinical signs. Hydrogen sulfide is indeed one of the three major gasotransmitters, with carbon monoxide and nitric oxide, and has a strong role in nervous and vascular systems. Its physiological concentration in the blood is only in the range of few nanomoles per liter when its pathological level can reach few micromoles per liter.Several systems based on organic chromophore molecules are already reported for the detection of H2S in simulated physiological media. Most of them are based on the reactivity of H2S with azide functions, to give the corresponding amine, and on the photoluminescent response of the amine.However, the development of applicable testing requires heterogeneous/solid H2S sensors. In this sense, Metal-Organic Frameworks (MOFs) are appealing platforms. Indeed, MOFs are crystalline and porous hybrid organic-inorganic solids. They can be built from organic chromophores and offer the advantage of site isolation. One recent example deals with the use of azido -containing MOF, made with 2-azidoterephthalate ligand, for the detection of H2S in solution but in the concentration range of 100 micromolar.We are presenting here a new MOF-based system for the detection of H2S in solution with concentration as low as 0.2 micromoles per liter. Appropriate irradiation of the azido-MOF, converted into amino-MOF upon H2S exposure, allows determining the linear correlation between photoluminescence signal intensity and H2S concentration.This opens bright new perspectives for the use of MOFs in sensing applications as well as for the applicable H2S detection for clinical diagnostic.