Modulation of Near-Infrared Mitochondria-Targetable fluorescent probe for H2S bioimaging through the modification of heavy atom iodine

H2S is correlated with mitochondrial dysfunction, which results in the death of cells. Two near-infrared fluorescent probes, Mito-HS-1 and Mito-HS-2, were designed for mitochondrial H2S imaging. Initially, the synthesis protocol of expensive IR-780-based hemicyanine (HXPI) was optimized with an appreciate yield of 80 % as compared with 14-56 % previously reported. Iodine atom was introduced to HXPI to obtain iodine-HXPI whose Stokes shift was increased to be 90 nm. On account of the rapid and fast nucleophilic attack of H2S, HXPI-based Mito-HS-1 could be applied for the real time imaging of mitochondrial H2S. Besides some similar optical properties with Mito-HS-1, iodine-HXPI-based Mito-HS-2 exhibited wider linear range (3-150 μM), more stable fluorescent imaging and more favorable specificity in vitro. Both Mito-HS-1 and Mito-HS-2 could be used to image exogenous H2S in cells, with Mito-HS-2 showing fairly better signal-to-noise. Additionally, the Pearson correlation coefficient of two probes demonstrated that they could successfully monitor mitochondrial H2S in A549 cells and Hela cells.