Mechanisms involved in the sequestration and resistance of cadmium for a plant-associated Pseudomonas strain.

Understanding Cd-resistant bacterial cadmium (Cd) resistance systems is crucial for improving microremediation in Cd-contaminated environments. However, these mechanisms are not fully understood in plant-associated bacteria. In the present study, we investigated the mechanisms underlying Cd sequestration and resistance in the strain AN-B15. These results showed that extracellular Cd sequestration by complexation in strain AN-B15 was primarily responsible for the removal of Cd from the solution. Transcriptome analyses have shown that the mechanisms of Cd resistance at the transcriptional level involve collaborative processes involving multiple metabolic pathways. The AN-B15 strain upregulated the expression of genes related to exopolymeric substance synthesis, metal transport, Fe-S cluster biogenesis, iron recruitment, reactive oxygen species oxidative stress defense, and DNA and protein repair to resist Cd-induced stress. Furthermore, inoculation with AN-B15 alleviated Cd-induced toxicity and reduced Cd uptake in the shoots of wheat seedlings, indicating its potential for remediation. Overall, the results improve our understanding of the mechanisms involved in Cd resistance in bacteria and thus have important implications for improving microremediation.

Reduced cadmium toxicity in rapeseed via alteration of root properties and accelerated plant growth by a nitrogen-fixing bacterium.

Cd accumulation in crops has become a global environmental problem because it endangers human health. Screening for microorganisms that can reduce Cd accumulation in crops is a possible measure to address this issue. However, success has been limited, and most previous work did not involve bacteria. In the present study, a strain of N-fixing bacteria (Burkholderia spp.) that exhibits high levels of Cd tolerance was screened. The ability of this bacterium to reduce Cd in rapeseed was then assessed in sterile hydroponic and open soil culture systems. In the hydroponic system, the Burkholderia inoculum promoted Cd fixation in rapeseed roots and thus reduced Cd enrichment in aboveground edible tissues (leaves). The mechanisms were related to increased activity of pectin methylesterase in root cell walls, and the transformation of the chemical form of root Cd from "active" (NaCl-extracted) to "inert" (HCl-extracted and residual Cd) states. Additionally, Burkholderia accelerated plant growth, thus shortening the period in which the plant is available for Cd absorption. In the soil culture system, Burkholderia also reduced Cd enrichment in rapeseed leaves in the presence of other microorganisms. Thus, the bacterial strain shows potential for broad application for reducing the accumulation of Cd in crops.

A highly sensitive NIR fluorescence probe for hypoxia imaging in cells and ulcerative colitis.

Ulcerative colitis, a kind of inflammatory bowel disease (IBD), is caused by dysregulated immune response of intestinal bacteria. This chronic disorder can lead to a deficiency of O2 (hypoxia) in the colon microenvironment. Nitroreductase (NTR) is a highly expressed endogenous enzyme under hypoxia, so the detection of NTR can provide diagnostic information about ulcerative colitis. Herein, an ultrasensitive NTR-triggered fluorescence probe (WS-1-NO2) is developed for hypoxia imaging in ulcerative colitis. The probe shows a significant fluorescence enhancement (45-fold) after reacting with NTR, with an extremely low detection limit of 0.096 ng/mL. Furthermore, we apply it for fluorescence imaging of hypoxia in living cells, tumors and dextran sulphate sodium (DSS)-induced ulcerative colitis mouse models. We believe that the probe may be investigated as an effective potential tool for gaining insight into the hypoxia-relevant diseases, such as cancer and ulcerative colitis.

A sensitive NIR mitochondria-targeting fluorescence probe for visualizing viscosity in living cells and mice.

Mitochondria are the powerhouses in cells, providing the energy needed for cellular activities. However, the abnormalities in the mitochondrial microenvironment (e.g., the increased viscosity) can lead to mitochondrial dysfunctions and diseases. Herein, we develop a series of near-infrared (NIR) fluorescence probes for the detection of viscosity. After screening, probe CQ-4 is selected since it shows a great fluorescence enhancement (89-fold) in the NIR window. Its specific response to viscosity is not influenced by pH, polarity and biological species. Under stimulation with monensin or nystatin, CQ-4 can measure the cellular viscosity changes with good biocompatibility. In addition, we can observe an increase of viscosity during starvation. CQ-4 is applied to distinguish cancer cells from normal cells based on the viscosity differences. Furthermore, the probe has been successfully applied to image viscosity in inflamed and tumor-bearing mice in vivo. Therefore, CQ-4 may contribute to the future study about viscosity in the physiological and pathological processes.

Activatable near-infrared fluorescent probe triggered by nitroreductase for in vivo ulcerative colitis hypoxia imaging.

Ulcerative colitis is a prevalent inflammatory disease caused by the intestinal bacterial infection. And it is related to the hypoxic degrees in the colon microenvironment. Hypoxia, a condition of imbalance in O2 supply and consumption, is accompanied by the overexpressed level of nitroreductase (NTR). Therefore, the NTR detection has been widely applied for the diagnosis of hypoxia-related diseases. In this study, we developed a novel near-infrared fluorescent probe (IW-1) for NTR. Upon reaction with NTR, IW-1 exhibited a significant fluorescence off-on response at 740 nm with a low detection limit of 0.043 µg/mL. Confocal fluorescence imaging verified its ability to detect the overexpression of NTR in cancer cells. More significantly, IW-1 was applied for in vivo hypoxia imaging in tumors and dextran sulphate sodium (DSS)-induced ulcerative colitis mouse model. We expect that the probe may present a new tool for better understanding the biological functions of NTR as well as revealing essential information about hypoxia-related pathological processes, including cancer and ulcerative colitis.

Visual monitoring of the mitochondrial pH changes during mitophagy with a NIR fluorescent probe and its application in tumor imaging.

Mitophagy, a mitochondria-selective autophagy process, plays critical roles in maintaining intracellular homeostasis by removing the damaged mitochondria and recycling the nutrients in a lysosome-dependent manner. Mitophagy process could result in the changes of mitochondrial pH. So fluorescent probes for detecting mitochondrial pH during mitophagy are highly needed for exploring the functions of mitochondria. Herein, a series of near-infrared pH probes were designed based on the rhodamine framework. The probes showed high sensitivity for pH with the tunable pKa from 4.74 to 6.54. Particularly, for probe 5 (with the pKa of 6.54), a linear relationship between fluorescence intensity and pH in the range of 5.6-7.2 was observed, which was suitable for mitochondrial pH detection. The probe displayed excellent mitochondria-targeting ability. It was applied to monitor pH changes during mitophagy caused by starvation. Besides, in vivo non-invasive visualization of tumor pH variations was achieved via the fluorescence imaging in the near-infrared region. We anticipate that the probe may be a useful tool for revealing essential information about mitophagy-related research and clinical tumor diagnosis.

Benzoindoxazine derivatives containing carbazole for detection of CN- and its application in plant seed extracts and cell imaging.

Cyanide (CN-) is a highly toxic compound that exists in many substances and is harmful to the environment and human health. Therefore, it is of great significance to develop excellent CN- ion probes, especially solvent-induced on-off fluorescent probes. Based on the condensation reaction of indolo[2,1-b][1,3]oxazine molecules with aldehydes, probes (E)-13a-(2-(9-ethyl-9H-carbazol-3-yl)vinyl)-14,14-dimethyl-10-nitro-13a,14-dihydro-8H-benzo[e]benzo[5,6][1,3]oxazino[3,2-a]indole (NCO) and (E)-13a-(2-(9-benzyl-9H-carbazol-3-yl)vinyl)-14,14-dimethyl-10-nitro-13a,14-dihydro-8H-benzo[e]benzo[5,6][1,3]oxazino[3,2-a]indole (NBO) were synthesized to detect CN-. Compared with other cyanogen ion probes, NCO and NBO have special carbazole ring structures and large conjugate systems. When CN- is added to the probe-detection solution, color changes that are visible to the naked eye can occur. The UV-vis spectrum test using differential spectroscopy shows that the probe (i) has excellent solvent-induced switching characteristics and stability (CH3OH-H2O) and (ii) high selectivity, anti-interference ability, and sensitivity for the detection of CN-. The fluorescence limit of detections (LODs) are 1.05 µM for NCO and 1.34 µM for NBO. The UV LODs are 0.83 µM for NCO and 0.87 µM for NBO. Fluorescence spectroscopy shows that the probe has remarkable fluorescence properties. Fluorescence titration experiments, liver cancer cell (Hep G2) imaging, and cytotoxicity experiments all show that the probes have high biocompatibility, low toxicity, high cell permeability, and high sensitivity for the detection of CN- in cells. In addition, NCO and NBO have been successfully used for the detection of cyanogenic glycosides in the seeds of ginkgo, crabapple, apple, and cherry. Test strips were fabricated to detect CN-. After adding CN-, the color of the test strip changed significantly-from brown to light yellow; thus, the test strips have a high application value in the fields of drug quality control, drug safety testing, and pharmacological research.

Novel pyrazoline-based fluorescent probe for detecting glutathione and its application in cells.

A novel compound, 2-(1,5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl)phenyl acrylate (probe L), was designed and synthesized as a highly sensitive and selective fluorescent probe for recognizing and detecting glutathione among cysteine, homocysteine and other amino acids. The structures of related compounds were characterized using IR, NMR and HRMS spectroscopy analysis. The probe is a non-fluorescent compound. On being mixed with glutathione in buffered EtOH:PBS=3:7 solution at pH 7.4, the probe exhibited the blue emission of the pyrazoline at 474 nm and a 83-fold enhancement in fluorescence intensity. This probe is very sensitive and displayed a linear fluorescence off-on response to glutathione with fluorometric detection limit of 8.2 × 10(-8)M. The emission of the probe is pH independent in the physiological pH range. Live-cell imaging of HeLa cells confirmed the cell permeability of the probe and its ability to selectively discriminate GSH from Cys and Hcy in cells. The toxicity of the probe was low in cultured HeLa cells.

A novel pyrazoline-based selective fluorescent probe for detecting reduced glutathione and its application in living cells and serum.

A new fluorescent probe, N-(4-(1,5-diphenyl-4,5-dihydro-1H-pyrazol-3-yl)phenyl)-2,4-dinitrobenzenesulfonamide (probe 3), was designed and synthesized as a highly sensitive and selective fluorescent probe for recognizing and detecting glutathione among biological thiols in aqueous media. Probe 3 is a nonfluorescent compound. On being mixed with biothiols under neutral aqueous conditions, the 2,4-dinitrobenzenesulfoyl moiety can be cleaved off by glutathione, and the blue emission of the pyrazoline at 464 nm is switched on, with a fluorescence enhancement of 488-fold for glutathione. Furthermore, probe 3 was highly selective for glutathione without interference from some biologically relevant analytes. The detection limit of glutathione was 4.11 × 10(-7) M. The emission of the probe is pH independent in the physiological pH range. Moreover, the probe can be used for fluorescent imaging of cellular glutathione and can be used for detecting glutathione in calf serum.

Novel chiral ferrocenylpyrazolo[1,5-a][1,4]diazepin-4-one derivatives--synthesis, characterization and inhibition against lung cancer cells.

A series of novel 2-ferrocenyl-7-hydroxy-5-phenethyl-5,6,7,8-tetrahydro-4H-pyrazolo[1,5-a][1,4]diazepin-4-one derivatives with optical activity (2) was synthesized in the microwave-assisted condition and characterized by means of IR, (1)H NMR and mass spectroscopy, and furthermore confirmed by X-ray analysis of a representative compound (R)-2a. Preliminary biological evaluation showed that some compounds could suppress the growth of A549, H322 and H1299 lung cancer cells. Among the tested compounds, 2b-d were more effective and might perform their action through cell cycle arrest for A549 cell. Whereas these compounds inhibited growth of H1299 and H322 cells by inducing apoptosis. The anti-tumor activities of these compounds were related to the nature of substituents in benzene moiety. In addition, the results indicated also that compounds 2b-d possessed notable cytotoxicity and selectivity for A549 vs H1299 and H322 lung cancer cells.

Synthesis of ferrocenyl pyrazole-containing chiral aminoethanol derivatives and their inhibition against A549 and H322 lung cancer cells.

A series of novel ethyl 3-ferrocenyl-1-(2-hydroxy-3-(phenylamino)propyl)-1H-pyrazole-5-carboxylate derivatives with optical activity (4) was synthesized by microwave-assisted reaction of substituted aniline and ethyl 3-ferrocenyl-1-(oxiran-2-ylmethyl)-1H-pyrazole-5-carboxylate that was prepared from ethyl 3-ferrocenyl-1H-pyrazole-5-carboxylate and (R)- or (S)-oxiran-2-ylmethyl 4-methylbenzenesulfonate. Structures of the compounds were characterized by means of IR, (1)H NMR and mass spectroscopy. Preliminary biological evaluation showed that all of the compounds could suppress the growth of A549 and H322 lung cancer cells. Among all of the tested compounds 4a, 4b and 4d were more effective and might perform their action through cell cycle arrest. Moreover, although the inhibition differences between R and S enantiomers are mostly not so significant, (R)-4b displayed more effective inhibition than (S)-4b.