Selective detection of hydrogen sulfide was achieved with 7-o-2′-(azidomethyl)benzoyl-4-methylcoumarin via analyte mediated reductive removal of the 2′-(azidomethyl)benzoyl moiety and concurrent generation of fluorescent 7-hydroxy-4-methylcoumarin.

Alteration of lysosome acidity has been implicated in many biological events ranging from apoptosis to cancer metastasis, etc. Mesoporous silica nanoparticles doped with acid activable rhodamine-lactam and fluorescein isothiocyanate (FITC) were developed for ratiometric sensing of lysosomal pH changes in live cells with flow cytometry.

Hypochlorous acid (HOCl) is biosynthesized from hydrogen peroxide via catalysis of myeloperoxidase in lysosomes of immunological cells. Despite being harnessed by immune systems against invading pathogens, biogenic HOCl can also damage host tissues and has been associated with a number of diseases. In this edge article, Förster resonance energy transfer based ratiometric imaging of lysosomal HOCl was achieved with silica nanoparticles comprising FITC (donor dye) and a nonfluorescent chemodosimeter which turned into rhodamine (acceptor dye) upon HOCl triggered tandem oxidation and β-elimination of the doped chemodosimeter. The nanodosimeter exhibited distinct biochemical properties relative to small molecule-based free chemodosimeters, e.g. lysosome-homing specificity and compatibility with aqueous media, enabling facile monitoring of lysosomal HOCl by conventional flow cytometry. The nanoprobe would be of broad utility for studies on in vivo generation and the impact of lysosomal HOCl in living cells or even in animals.

The parameters of intracellular acidic compartments are altered in apoptosis, autophagy, cancer metastasis, etc. Low background and selective staining of lysosomes and autophagosomes was achieved with N-(rhodamine 6G)-lactam-ethylenediamine (R6G-EDA) which fluoresces in acidic vesiclesvia pH mediated ring opening of the intramolecular lactam. Long retention time of R6G-EDA in lysosomes and its exceptional stability against photo-bleaching allow full time tracking of lysosome morphology changes in tumor necrosis factor-α (TNF-α) triggered cell death, suggesting its utility for acidic vesicle studies in cell biology.

A chromogenic and fluorogenic detection of a nerve agent simulant was developed based on diethyl chlorophosphate triggered tandem phosphorylation and intramolecular cyclization of N-(rhodamine B)-deoxylactam-2-aminoethanol.

A visual and fluorogenic detection method for a nerve agent simulant was developed based on a Lossen rearrangement of rhodamine–hydroxamate, in the presence of diethyl chlorophosphate, under alkaline conditions.