The organelle-specific pH is crucial for cell homeostasis. Aberrant pH of lysosomes has been manifested in myriad diseases. To probe lysosome responses to cell stress, we herein report the detection of lysosomal pH changes with a dual colored probe (CM-ROX), featuring a coumarin domain with “always-on” blue fluorescence and a rhodamine–lactam domain activatable to lysosomal acidity to give red fluorescence. With sensitive ratiometric signals upon subtle pH changes, CM-ROX enables discernment of lysosomal pH changes in cells undergoing autophagy, cell death, and viral infection.Keywords: autophagy; cell death; lysosome; pH changes; ratiometric fluorescence imaging; viral infection;

Cell fate is largely shaped by combined activity of different types of organelles, which often feature functionally critical parameters that succumb to pathological inducers. We herein report the analysis of cell bioenergetic profiles with a dual organelle-oriented chemosensor (RC-AMI), partitioning in mitochondria to give blue fluorescence and in lysosomes to give red fluorescence. Responsive to lysosomal pH and mitochondrial transmembrane potential (ΔΨm), two parameters crucial to cell bioenergetics, RC-AMI enables dual colored reporting of lysosomal acidity and ΔΨm, revealing upregulated ΔΨm and imbalance dramatically shifted favoring ΔΨm over lysosomal acidity in cancer cells whereas the tendency is reversed in starved cells. Complementing classical homo-organelle-specific sensors, this dual organelle-oriented and fluorescently responsive probe offers a new tool to detect imbalance between lysosomal acidity and mitochondrial ΔΨm, an index critical for cancer bioenergetics.

Malfunctioning organelles are often difficult to probe with classical organelle-homing sensors owing to disruption of physiological organelle-probe affinity. We herein report the use of a responsive hetero-organelle partition and signal activable probe (RC-TPP) for detecting mitochondrial depolarization, a pathologically relevant event featuring loss of the electrical potentials across the mitochondrial membrane (ΔΨm). Partitioned in mitochondria to give blue fluorescence, RC-TPP relocates into lysosomes upon mitochondrial depolarization and exhibits red fluorescence triggered by lysosomal acidity, enabling determination of autophagy relevant mitochondrial depolarization and the chronological sequence of mitochondrial depolarization and lysosomal neutralization in distinct cell death signalling pathways. As an alternative to classic homo-organelle specific molecular systems, this hetero-organelle responsive approach provides a new perspective from which to study dysfunctional organelles.

Techniques eliciting anti-tumor immunity are of interest for immunotherapy. We herein report the covalent incorporation of a non-self immunogen into the tumor glycocalyx by metabolic oligosaccharide engineering with 2,4-dinitrophenylated sialic acid (DNPSia). This enables marked suppression of pulmonary metastasis and subcutaneous tumor growth of B16F10 melanoma cells in mice preimmunized to produce anti-DNP antibodies. Located on the exterior glycocalyx, DNPSia is well-positioned to recruit antibodies. Given the high levels of natural anti-DNP antibodies in humans and ubiquitous sialylation across many cancers, DNPSia offers a simplified route to redirect immunity against diverse tumors without recourse to preimmunization.

Activatable molecular systems enabling precise tumor localization are valuable for complete tumor resection. Herein, we report sialic acid-capped polymeric nanovesicles encapsulating the near infrared profluorophore (pNIR@P@SA) for lysosome activation based dual modality tumor imaging. The probe features surface-anchored sialic acid for tumor targeting and a core of near infrared profluorophore (pNIR) which undergoes lysosomal acidity triggered isomerization to give optical and optoacoustic signals upon cell internalization. Imaging studies reveal high-efficiency uptake and signal activation of pNIR@P@SA in subcutaneous tumors and millimeter-sized liver tumor foci in mice. The high tumor-to-healthy organ signal contrasts and discernment of tiny liver tumors from normal liver tissues validate the potential of pNIR@P@SA for high performance optical and optoacoustic imaging guided tumor resection.

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.

Phagocytosis is critical for immunity against pathogens. Prior imaging using dye-labeled synthetic beads or green fluorescent protein-expressing bacteria is limited by “always-on” signals which compromise discerning phagocytosed particles from adherent particles. Targeting cellular internalization of pathogens into acidic phagolysosomes, we herein report “turn-on” fluorescence imaging of phagocytosis with viable bacteria featuring peptidoglycans covalently modified with rhodamine-lactam responsive to acidic pH. Culturing of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with d-lysine conjugated rhodamine-lactam and fluorescein isocyanate (FITC) leads to efficient metabolic incorporation of FITC and rhodamine-lactam into bacterial peptidoglycan. E. coli and S. aureus become red-emissive upon phagocytosis into Raw 264.7 macrophages. With FITC as the reference signal, the mono- and dual-color emission allow efficient in situ distinction of ingested bacteria from extracellular bacteria. Given the ease of optical peptidoglycan labeling, the prevalence of microbial peptidoglycan and preservation of microbial surface landscape, this approach would be of use for investigation on microbial pathogenesis and high-throughput screening of immunomodulators of phagocytosis.

Inflammation causes significant morbidity and mortality, necessitating effective in vivo imaging of inflammation. Prior approaches often rely on combination of optical agents with entities specific for proteinaceous biomarkers overexpressed in inflammatory tissues. We herein report a fundamentally new approach to image inflammation by targeting lysosomes undergoing acidification in inflammatory cells with a sialic acid (Sia) conjugated near-infrared profluorophore (pNIR). Sia–pNIR contains a sialic acid domain for in vivo targeting of inflamed tissues and a pNIR domain which isomerizes into fluorescent and optoacoustic species in acidic lysosomes. Sia–pNIR displays high inflammation-to-healthy tissue signal contrasts in mice treated with Escherichia coli, Staphylococcus aureus, or lipopolysaccharide. In addition, inflammation-associated fluorescence is switched off upon antibiotics treatment in mice. This report shows the potentials of Sia–pNIR for activatable dual-modality inflammation imaging, and particularly the use of lysosomes of inflamed cells as a previously unappreciated biomarker for inflammation imaging.

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.

Surgical resection is widely used for tumor treatment, necessitating approaches for the precise locating of elusive tumor foci. We report the high performance detection of tumors in mice with fluorescein-isothiocyanate (FITC) labelled sialic acid (FITC-SA), a fluorescent monosaccharide with low cytoxicity. Analysis of mice intravenously injected with FITC-SA revealed high target-to-background fluorescence ratios in subcutaneous tumors and liver tumor implants with 0.2–5 mm diameters, which are significantly below the clinical threshold of minimal residual cancer (∼1 cm clearance). Extracellular FITC-SA is quickly cleared from circulation whereas the intracellular FITC-SA could be metabolically incorporated into glycoproteins via a cellular sialylation pathway. Compared with FITC-SA-laden nanoparticles, free FITC-SA is preferentially and quickly taken up by tumors in mice and displays high tumor-to-background signal contrast, suggesting the potential for fluorescence directed surgical ablation of tumors.

Tumor-reporting probes are valuable to guide surgical resection of tumor foci elusive to visual inspection. As tumors display distinct arrays of lectins, we herein report the construction and screening of a panel of glycan-displaying smart micelles for tumor illumination in mice. These micelles consist of cores of rhodamine-sultam (RST) responsive to lysosomal acidity and a corona of poly[styrene-alter-(maleic acid)] glycosylated with D-glucosamine, D-mannosamine or D-galactosamine. These nanoscale micelles are nonfluorescent extracellularly and become luminescent within acidic lysosomes, enabling optical tracking of tumor endocytosis of the micelles. In vivo screening revealed high-efficiency uptake and fluorescence activation of galactosylated micelles (RST@P-Gal) by subcutaneous tumor and disseminated liver tumor foci with diameters of 0.1–10 mm, which is significantly below minimal residual cancer (a minimum of 1 cm clearance). This system is readily adapted to illuminate different tumors by expanding the diversity of glycans on the shell. Given the robustness and high performance of this system, lectin-targeted responsive micelles are attractive for diagnosis or surgical ablation of tumors.

N-(Rhodamine B)-benzimidazole (RB-IM), featuring an intramolecular spiro-benzimidazole, was developed for selective sensing of protons via opening of the spiro-ring to give fluorescent and colored species. The utility of RB-IM was demonstrated by imaging of lysosomes in live cells and staining of the intestine of zebrafish.

Rhodamine–silica nanocomposite bridged by a cleavable linker was used for highly sensitive nitrite detection via analyte triggered release of rhodamine from silica particles. Centrifugal removal of pristine nanoconjugate from the assay medium effectively decreased background signals in the supernatant whereas rhodamine unleashed from silica platform is retained in the supernatant, enabling facile detection of nitrite with an assay limit of 50 nM which is 400 folds lower than legislated maximum contaminant levels of nitrite in drinking water. Assays based on small molecular chemosensors are often compromised by their intrinsic fluorescence signals and low aqueous compatibility. The performance of water compatible rhodamine–silica nanocomposite suggests broad analytical potentials of centrifugal nanoparticulate systems with dyes conjugated via appropriate cleavable linkers.Highly sensitive and facile nitrite detection is achieved with rhodamine–silica nanoconjugate via analyte triggered release of rhodamine from the silica and decreasing background signals by centrifugal removal of the nanocomposite from the assay medium.

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.

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.

Two nonfluorescent and colorless chemodosimeters featuring benzothiazoline moiety were developed for chromo-fluorogenic detection of HOCl.Two nonfluorescent and colorless chemodosimeters featuring benzothiazoline moiety were developed for chromo-fluorogenic detection of HOCl.

•A novel chimeric molecular pH-meter (Lyso-DR) was proposed.•The proton activatable rhodamine-lactam and dansyl moiety was linked to form ratiometric fluorescence pair.•Lyso-DR exhibited pH dependent dual fluorescence emission inside lysosomes in living cells.•pH variations of lysosomes undergoing apoptosis and necrosis were visualized with Lyso-DR.Intracellular acidic vesicles, constituted mostly by lysosomes, mediated a variety of biological events ranging from endocytosis, apoptosis, to cancer metastasis, etc. A chimeric molecular pH-meter (Lyso-DR), comprised of a dansyl fluorophore and proton activatable rhodamine-lactam, was prepared for ratiometric reporting of intralysosomal acidity. Exclusively confined in lysosomes, Lyso-DR exhibited pH dependent dual fluorescence emission bands which enable resolution of individual lysosomes in terms of acidity and quantitation of the overall intracellular lysosomal acidity, e.g. the lysosomal pH of HeLa cells is around pH 5.0 whereas that of L929 cells is around pH 6.2. Lyso-DR effectively differentiated the lysosomal pH changes of cells undergoing apoptosis vs necrosis, suggesting its utility in investigations on lysosome involved biomedical processes.

Optical probes that could illuminate tumors are promising tools to enable surgical ablation of tumor colonies that are elusive to identify by conventional visual inspection. Polymeric nanoprobes, comprised of a biocompatible poly[styrene-alter-(maleic acid)] carrier and pH responsive rhodamine-deoxylactam, preferentially accumulate in tumors in mice and are activated by lysosomal acidity into highly fluorescent species. The favorable characteristics of passive tumor targeting, e.g. high tumor to normal tissue ratio, long retention time in tumors and low in vivo toxicity, suggest the utility of the nanoprobes in fluorescence guided intraoperative detection of different tumors.

Synthetic carriers that enable site-specific intracellular delivery of proteins are valuable in many biomedical applications. Aldehyde-displaying silica nanoparticles (MSN-aldehyde) containing lysosome activatable rhodamine-lactams were prepared for fluorescent tracking and delivery of proteins via lysosomal acidity-triggered release of proteins and “turn-on” fluorescence of doped rhodamine-lactam. The carrier-protein nanocomposites were site-specifically internalized into lysosomes of HepG2, HeLa and L929 cells where the loaded proteins, including arginase and green fluorescent protein, were released via lysosomal acidity-mediated hydrolysis of the bridging imine linkages. The released proteins efficiently escaped from lysosomes into cytosol where arginase effectively induced autophagy of the host cells. With the ease of formation of pH-labile imine linkages between MSN-aldehyde and lysine of various proteins, MSN-aldehyde would be of interest as a general vector for cytosolic delivery of proteins.

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.

Determination of nitrite levels is of substantial interest in many applications from monitoring drinking water quality to clinical diagnosis, etc. N-(Rhodamine B)-lactam-o-phenylenediamine (RB-PDA) was identified from a panel of rhodamine-lactams for fluorogenic and visual detection of nitrite in aqueous media via analyte triggered formation of highly fluorescent and deep colored species.

Fluorescent imaging of mitochondria is an essential tool for studies of mitochondrial functions. The staining of mitochondria with potential-indicating dyes, e.g., rhodamine 123, readily vanishes upon loss of the transmembrane potential under certain conditions. 1-(Rhodamine B)-4-(2′-chloroacetyl)-piperazine amide (RB-CAP) was shown to be electrophoretically accumulated into mitochondria, forming covalent bioconjugates with intramitochondrial protein sulfhydryls which enabled the mitochondrial staining to endure in subsequent collapse of the transmembrane potentials. RB-CAP is highly photostable and exhibits stringent selectivity in covalent labeling of mitochondria in living cells. Being much less expensive, RB-CAP is a superior substituent for MitoTracker probes in functional studies of mitochondria.

N-(rhodamine B)-deoxylactam-5-amino-1-pentanol (dRB-APOH) was designed and prepared as the chromo-fluorogenic sensor for detection of a nerve agent simulant via analyte triggered tandem phosphorylation and opening of the intramolecular deoxylactam. The successful detection of diethyl chlorophosphate suggests the utility of rhodamine-deoxylactams as the chromo-fluorogenic signal reporting platform for design of sensors targeting reactive chemical species via various chemistries.N-(rhodamine B)-deoxylactam-5-amino-1-pentanol (dRB-APOH) was designed and prepared as the chromogenic and fluorogenic chemodosimerter for detection of a nerve agent simulant via analyte triggered tandem phosphorylation and opening of the intramolecualr deoxylactam.

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.

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.

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 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.

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.

Topical microbicides offer women the opportunity to protect themselves from sexual HIV transmission under their own control. A series of poly[styrene-alt-(maleic anhydride)] derivatives were prepared by amidation or hydrolysis of the anhydride moiety. The derivatives were shown to be of low cell toxicity and effectively inhibited HIV-1 infections in an in vitro cellular model. Poly[styrene-alt-(maleic acid, sodium salt)] was the most potent inhibitor, being 100-fold more potent than dextran sulfate suggesting its potential application as a new class of polyanionic microbicides.

Determination of nitrite levels is of substantial interest in many applications from monitoring drinking water quality to clinical diagnosis, etc. N-(Rhodamine B)-lactam-o-phenylenediamine (RB-PDA) was identified from a panel of rhodamine-lactams for fluorogenic and visual detection of nitrite in aqueous media via analyte triggered formation of highly fluorescent and deep colored species.

Tumor-reporting probes are valuable to guide surgical resection of tumor foci elusive to visual inspection. As tumors display distinct arrays of lectins, we herein report the construction and screening of a panel of glycan-displaying smart micelles for tumor illumination in mice. These micelles consist of cores of rhodamine-sultam (RST) responsive to lysosomal acidity and a corona of poly[styrene-alter-(maleic acid)] glycosylated with D-glucosamine, D-mannosamine or D-galactosamine. These nanoscale micelles are nonfluorescent extracellularly and become luminescent within acidic lysosomes, enabling optical tracking of tumor endocytosis of the micelles. In vivo screening revealed high-efficiency uptake and fluorescence activation of galactosylated micelles (RST@P-Gal) by subcutaneous tumor and disseminated liver tumor foci with diameters of 0.1–10 mm, which is significantly below minimal residual cancer (a minimum of 1 cm clearance). This system is readily adapted to illuminate different tumors by expanding the diversity of glycans on the shell. Given the robustness and high performance of this system, lectin-targeted responsive micelles are attractive for diagnosis or surgical ablation of tumors.

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.

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.

Activatable molecular systems enabling precise tumor localization are valuable for complete tumor resection. Herein, we report sialic acid-capped polymeric nanovesicles encapsulating the near infrared profluorophore (pNIR@P@SA) for lysosome activation based dual modality tumor imaging. The probe features surface-anchored sialic acid for tumor targeting and a core of near infrared profluorophore (pNIR) which undergoes lysosomal acidity triggered isomerization to give optical and optoacoustic signals upon cell internalization. Imaging studies reveal high-efficiency uptake and signal activation of pNIR@P@SA in subcutaneous tumors and millimeter-sized liver tumor foci in mice. The high tumor-to-healthy organ signal contrasts and discernment of tiny liver tumors from normal liver tissues validate the potential of pNIR@P@SA for high performance optical and optoacoustic imaging guided tumor resection.

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.

Fluorescent imaging of mitochondria is an essential tool for studies of mitochondrial functions. The staining of mitochondria with potential-indicating dyes, e.g., rhodamine 123, readily vanishes upon loss of the transmembrane potential under certain conditions. 1-(Rhodamine B)-4-(2′-chloroacetyl)-piperazine amide (RB-CAP) was shown to be electrophoretically accumulated into mitochondria, forming covalent bioconjugates with intramitochondrial protein sulfhydryls which enabled the mitochondrial staining to endure in subsequent collapse of the transmembrane potentials. RB-CAP is highly photostable and exhibits stringent selectivity in covalent labeling of mitochondria in living cells. Being much less expensive, RB-CAP is a superior substituent for MitoTracker probes in functional studies of mitochondria.

Malfunctioning organelles are often difficult to probe with classical organelle-homing sensors owing to disruption of physiological organelle-probe affinity. We herein report the use of a responsive hetero-organelle partition and signal activable probe (RC-TPP) for detecting mitochondrial depolarization, a pathologically relevant event featuring loss of the electrical potentials across the mitochondrial membrane (ΔΨm). Partitioned in mitochondria to give blue fluorescence, RC-TPP relocates into lysosomes upon mitochondrial depolarization and exhibits red fluorescence triggered by lysosomal acidity, enabling determination of autophagy relevant mitochondrial depolarization and the chronological sequence of mitochondrial depolarization and lysosomal neutralization in distinct cell death signalling pathways. As an alternative to classic homo-organelle specific molecular systems, this hetero-organelle responsive approach provides a new perspective from which to study dysfunctional organelles.

Optical probes that could illuminate tumors are promising tools to enable surgical ablation of tumor colonies that are elusive to identify by conventional visual inspection. Polymeric nanoprobes, comprised of a biocompatible poly[styrene-alter-(maleic acid)] carrier and pH responsive rhodamine-deoxylactam, preferentially accumulate in tumors in mice and are activated by lysosomal acidity into highly fluorescent species. The favorable characteristics of passive tumor targeting, e.g. high tumor to normal tissue ratio, long retention time in tumors and low in vivo toxicity, suggest the utility of the nanoprobes in fluorescence guided intraoperative detection of different tumors.

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.

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 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.

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.

Surgical resection is widely used for tumor treatment, necessitating approaches for the precise locating of elusive tumor foci. We report the high performance detection of tumors in mice with fluorescein-isothiocyanate (FITC) labelled sialic acid (FITC-SA), a fluorescent monosaccharide with low cytoxicity. Analysis of mice intravenously injected with FITC-SA revealed high target-to-background fluorescence ratios in subcutaneous tumors and liver tumor implants with 0.2–5 mm diameters, which are significantly below the clinical threshold of minimal residual cancer (∼1 cm clearance). Extracellular FITC-SA is quickly cleared from circulation whereas the intracellular FITC-SA could be metabolically incorporated into glycoproteins via a cellular sialylation pathway. Compared with FITC-SA-laden nanoparticles, free FITC-SA is preferentially and quickly taken up by tumors in mice and displays high tumor-to-background signal contrast, suggesting the potential for fluorescence directed surgical ablation of tumors.

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.

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.

Synthetic carriers that enable site-specific intracellular delivery of proteins are valuable in many biomedical applications. Aldehyde-displaying silica nanoparticles (MSN-aldehyde) containing lysosome activatable rhodamine-lactams were prepared for fluorescent tracking and delivery of proteins via lysosomal acidity-triggered release of proteins and “turn-on” fluorescence of doped rhodamine-lactam. The carrier-protein nanocomposites were site-specifically internalized into lysosomes of HepG2, HeLa and L929 cells where the loaded proteins, including arginase and green fluorescent protein, were released via lysosomal acidity-mediated hydrolysis of the bridging imine linkages. The released proteins efficiently escaped from lysosomes into cytosol where arginase effectively induced autophagy of the host cells. With the ease of formation of pH-labile imine linkages between MSN-aldehyde and lysine of various proteins, MSN-aldehyde would be of interest as a general vector for cytosolic delivery of proteins.