Ratiometric Near-Infrared Fluorescent Probes Based on Hemicyanine Dyes Bearing Dithioacetal and Formal Residues for pH Detection in Mitochondria

Ratiometric near-infrared fluorescent probes (AH+ and BH+) have been prepared for pH determination in mitochondria by attaching dithioacetal and formal residues onto a hemicyanine dye. The reactive formyl group on probe BH+ allows for retention inside mitochondria as it can react with a protein primary amine residue to form an imine under slightly basic pH 8.0. Probes AH+ and BH+ display ratiometric fluorescent responses to pH changes through the protonation and deprotonaton of a hydroxy group in hemicyanine dyes with experimentally determined pKa values of 6.85 and 6.49, respectively. Calculated pKa values from a variety of theoretical methods indicated that the SMDBONDI method of accounting for solvent and van der Waals radii plus including a water molecule located near the site of protonation produced the closest overall agreement with the experimental values at 7.33 and 6.14 for AH+ and BH+ respectively.

A near-infrared fluorescent probe based on a hemicyanine dye with an oxazolidine switch for mitochondrial pH detection

A near-infrared fluorescent probe (AH+) has been prepared by incorporating an oxazolidine switch into a near-infrared hemicyanine dye for pH detection in the mitochondria of HeLa cells.

A caveat to common hemicyanine dye components and their resolution

Hemicyanine dyes containing typical heterocycles such as 2-indolinium have limited chemo- and photo-stability issues, which can be resolved with a 4-pyridinium derivative that also shows good two-photon imaging capability.

A real-time ratiometric fluorescent probe for imaging of SO2 derivatives in mitochondria of living cells

A real-time ratiometric fluorescent probe (IN-CZ) for highly selective detection of sulfite was designed and synthesized, which is based on modulating the intramolecular charge transfer of the hemicyanine dye platform.

Trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium Iodide@Hemimethylcucurbit[6]uril Fluorescent Probe for Anion Recognition

In the present work, a host–guest system of a hemimethyl-substituted cucurbit[6]uril derived from 3α-methyl-glycoluril (HMeQ[6]) and a hemicyanine dye, trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide (t-DSMI) showing strong fluorescence emission has been evaluated as a fluorescent probe. The results of a preliminary systematic study on the detection of a series of inorganic anions have revealed that this Q[n]-based host–guest fluorescent probe shows clear responses to BF4− and H2PO4− anions through distinct fluorescence quenching. Application of this Q[n]-based host–guest interaction system in anion recognition or detection opens a new avenue in Q[n] chemistry.