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Methods for optical tracking of pathogen–host interactions are of biomedical significance. We herein have reported a high molecular weight pH sensor (Den-pH) that is assembled in bacteria and then stably trapped in bacteria irrespective of bacterial membrane potentials. Endowed with acidity-triggered red fluorescence, Den-pH allows signal-on tracking of S. aureus in phagocytosis by macrophages. Intra-bacterial formation of multifunctional optical probes, which offers the advantage of overcoming the liability of conventional potential-sensitive dyes to dissipate from stressed bacteria, offers a new tool to study stressed pathogens. [ABSTRACT FROM AUTHOR]

Approaches that could enable precise photodynamic therapy (PDT) are of therapeutic potential. We herein report a trifunctional probe (Glu-RdEB) that could be activated to generate fluorescent rhodamine species to pinpoint tumor foci. The probe contains a γ-glutaminyl moiety cleavable to γ-glutamyl transpeptidase (GGT) overexpressed in multiple tumors, an entity of an ENBS photosensitizer for PDT, and an entity of rhodamine fluorescently quenched by ENBS. Upon activation by tumor-associated GGT, the probe releases highly fluorescent rhodamine that is selectively confined in tumors whereby light irradiation leads to effective tumor regression in mice. These results indicate the feasibility of a fluorescently quenched dye–photosensitizer pair to yield tumor-activatable fluorescence to direct PDT. [ABSTRACT FROM AUTHOR]

Stressed organelles are often challenging to image with canonical organelle probes owing to their propensity to dissipate from stressed organelles. We herein report the imaging of stressed lysosomes with color-switchable glyco-probes that contain an entity of mannose-6-carboxylate or sialic acid for targeting to and long-term retention in stressed lysosomes, and a diad of fluorescein/rhodamine-X-lactam exhibiting dramatic red-to-green fluorescence shift upon pH elevation. Relative to acidotropic dyes prone to dissipate from pH-elevated lysosomes, both glyco-probes are stably trapped in lysosomes without resorting to lysosomal acidity. Importantly, these probes are red emissive in acidic lysosomes (pH 4.5–5.8), but switched to green fluorescence in lysosomes of pH 6.0–7.4, allowing dual color discrimination of lysosomal pH alterations in cell starvation. These results support the use of sugar-armed sensors to investigate stressed lysosomes in biology and disease. [ABSTRACT FROM AUTHOR]

Dying cell clearance is critical for myriad biological processes such as tissue homeostasis. We herein report an enzyme-activated fluorescence cell labeling approach and its use for multicolor imaging of dying cell clearance. Diacetylated 4-hydroxymandelic acid (DHA)-conjugated dyes give rise to reactive quinone methides upon deacetylation in live cells, which in turn covalently labels cellular proteins. With partner cells tagged with distinct fluorescence, apoptotic cell clearance by Raw 264.7 macrophages and epithelial HeLa cells was captured by confocal microscopy, showing the potential of DHA-based cell labeling for investigating cell–cell interactions. [ABSTRACT FROM AUTHOR]

We report senescence imaging with a fluorescence-quenched self-immolative sialoside probe (Sia-RQ) which gives a reactive quinone methide to allow in situ fluorescence labeling of sialidases upon desialylation. Dramatic upregulation of lysosome-associated sialidase was uncovered in cell senescence with Sia-RQ, suggesting the use of sialidase as a new biomarker for senescence. [ABSTRACT FROM AUTHOR]

Nanoscale-vesicles that can target pathogens are valuable for biomedical applications. In this study, a photo-responsive nanogenerator of nitric oxide (NO) comprised of a hydrophobic core of 3-trifluoromethyl-4-nitroaniline (TFNA) and a hydrophilic shell of mannosylated poly[styrene-alter-(maleic acid)] was constructed to target and kill lectin-expressing cells. The release of NO from the nanogenerator (T@P-M) was effectively induced by luminol-derived chemiluminescence (CL), leading to high-efficiency killing of Escherichia coli (E. coli) treated with T@P-M. In addition, the uptake of T@P-M by Raw 264.7 macrophages was achieved by cell surface lectin-mediated endocytosis, enabling the intracellular release of NO from the internalized T@P-M upon the induction of extracellular chemiluminescence. Because in vivo-generated CL can overcome the limited penetration of exogenous light into biological tissues, T@P-M has potential uses as a targetable photo-activatable microbicide to combat pathogens bearing lectins or residing in macrophages. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Agents enabling tumor staging are valuable for cancer surgery. Herein, a targetable sialic acid-armed near-infrared profluorophore (SA-pNIR) is reported for fluorescence guided tumor detection. SA-pNIR consists of a sialic acid entity effective for in vivo tumor targeting and a profluorophore which undergoes lysosomal acidity-triggered fluorogenic isomerization. SA-pNIR displays a number of advantageous biomedical properties in mice, e.g. high tumor-to-normal tissue signal contrast, long-term retention in tumors and low systemic toxicity. In addition, SA-pNIR effectively converts NIR light into cytotoxic heat in cells, suggesting tumor-activatable photothermal therapy. With high performance tumor illumination and lysosome-activatable photothermal properties, SA-pNIR is a promising agent for detection and photothermal ablation of surgically exposed tumors.

A photothermal pH-reporting nanoprobe was developed for intraoperative tumor detection by "turn-on" fluorescence of the probe inside viable tumor cells, photothermal tumor therapy, and in situ monitoring of tumor killing by non-fluorescence of the probe in damaged cells.

Intracellular delivery is a prerequisite for the efficacy of many pharmaceutical proteins. Herein, vitamin B 6 (pyridoxal-5'-phosphate, PLP) functionalized calcium phosphate (CP) is used as the bio-recyclable nanocarrier for delivery of proteins into cells. Proteins could be loaded on/released from PLP-CP via formation/hydrolysis of pH sensitive aldimine bridging lysine and surface-displayed PLP. The loaded proteins could be delivered into the cytosol of HeLa, HepG2 and L929 cells where the carrier could be metabolized into endogenous metabolites of Ca 2+ , HPO 4 2- , and vitamin B 6 . PLP-CP mediated cell transduction is 10-40 folds more efficient than TAT which is a widely used cell penetrating peptide, demonstrating the utility of PLP-CP as the traceless platform for high-efficiency delivery of proteins into mammalian cells.

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.

A highly sensitive chemodosimeter was identified from a panel of rhodamine derivatives for rapid and visual detection of phosgene with a detection limit of 50 nM triphosgene. Visual detection of gaseous phosgene with chemodosimeter absorbed paper strips was demonstrated., (This journal is © The Royal Society of Chemistry 2012)

A chromogenic and fluorogenic detection of aldehydes was achieved via analyte triggered opening of the deoxylactam of N-(rhodamine B)-deoxylactam-ethylenediamine (dRB-EDA). The utility of the sensor was demonstrated by fluorescent labeling of aldehyde-displaying sialoproteins on cell surfaces.

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 vesicles via 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.

Micellar mannose nanoparticles were constructed from poly{styrene-co-[(maleic anhydride)-alt-styrene]} with fluorophores or quenchers doped into the hydrophobic inner cores, allowing the direct monitoring of multivalent lectin-glycan interactions. The mannose-displaying nanoparticles bind Con A and sperm surface lectins with high affinity, suggesting their broad utility for modulating protein-carbohydrate interaction mediated cell surface biology.