11 research outputs found

    Strategy for Sensor Based on Fluorescence Emission Red Shift of Conjugated Polymers: Applications in pH Response and Enzyme Activity Detection

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    A new strategy was developed and applied in monitoring pH response and enzyme activity based on fluorescence emission red shift (FERS) of the conjugated polymer PPP-OR10 induced by the inner filter effect (IFE) of nitrobenzene derivatives. Neutral poly­(<i>p</i>-phenylenes) functionalized with oligo­(oxyethylene) side chains (PPP-OR10) was designed and synthesized by the Suzuki cross-coupling reaction. Nitrobenzene derivatives display different light absorption activities in the acidic or basic form due to adopting different electron-transition types. When environmental pH is higher than their p<i>K</i><sub>a</sub> values, nitrobenzene derivatives exhibit strong absorbance around 400 nm, which is close to the maximal emission of polymer PPP-OR10. As a result, the maximal emission wavelength of PPP-OR10/nitrobenzene derivatives red shifts with the pH value increasing. Apparently, the IFE plays a very important role in this case. A new method has been designed that takes advantage of this pH-sensitive platform to sensor α-chymotrypsin (ChT) based on the IFE of <i>p</i>-nitroaniline, since the absorption spectrum of <i>p</i>-nitroaniline, the ChT-hydrolyzed product of <i>N</i>-benzoyl-l-tyrosine-<i>p</i>-nitroaniline (BTNA), overlaps with the emission spectrum of PPP-OR10. In addition, the present approach can detect α-chymotrypsin with a detection limit of 0.1 μM, which is lower than that of the corresponding absorption spectroscopy method. Furthermore, the pH response and enzyme detections can be carried out in 10% serum, which makes this new FERS-based strategy promising in applications in more complex conditions and a broader field

    Water-Soluble Conjugated Polymer as a Platform for Adenosine Deaminase Sensing Based on Fluorescence Resonance Energy Transfer Technique

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    We report a new biosensor for adenosine deaminase (ADA) sensing based on water-soluble conjugated poly­(9,9-bis­(6′-<i>N</i>,<i>N</i>,<i>N</i>-trimethylammonium)­hexyl)­fluorine phenylene (PFP) and fluorescence resonance energy transfer technique. In this biosensor, PFP, DNAc-FI labeled with fluorescein (FAM), and ethidium bromide (EB) were used as the fluorescence energy donor, resonance gate, and the final fluorescence energy acceptor, respectively. In the absence of ADA, the adenosine aptamer forms a hairpin-like conformation with adenosine, which is far from its complementary single-stranded DNA (DNAc-FI). When PFP is excited at 380 nm, fluorescein emits strong green fluorescence via one-step FRET while EB has no fluorescence. After addition of ADA, adenosine is hydrolyzed to inosine and then double-stranded DNA (dsDNA) is formed between the aptamer and DNAc-FI, followed by EB intercalating into dsDNA. Once PFP is excited, EB will emit strong yellow fluorescence after two-step FRET from PFP to fluorescein and from fluorescein to EB. The sensitive ADA detection then is realized with a low detection limit of 0.5 U/L by measuring the FRET ratio of EB to fluorescein. Most importantly, the assay is accomplished homogeneously in 25 min without further treatments, which is much more simple and rapid than that reported in literature. Hence, this method demonstrates the sensitive, cost-effective, and rapid detection of ADA activity. It also opens an opportunity for designing promising sensors for other enzymes

    Multifunctional Probe Based on Cationic Conjugated Polymers for Nitroreductase-Related Analysis: Sensing, Hypoxia Diagnosis, and Imaging

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    Nitroreductase (NTR) is overexpressed in hypoxic tumors. Moreover, hypoxia is usually considered as the most important feature of various diseases. Thus, it is important to build a sensitive and selective method for NTR detection and hypoxia diagnosis. Herein, a new cationic conjugated polymer (PBFBT-NP) with <i>p</i>-nitrophenyl group in the side chain was designed and synthesized as a fluorescent probe for the detection of NTR. In the absence of NTR, the fluorescence of PBFBT-NP was quenched due to photoinduced electron transfer (PET). On the contrary, in the presence of NTR, NTR can specifically react with <i>p</i>-nitrophenyl group to form <i>p</i>-aminophenyl group, which leads to the PET being inhibited and the polymer’s fluorescence significantly increasing (>110-fold). The sensitive and selective NTR sensing method in vitro is thus constructed with a low detection limit of 2.9 ng/mL. Moreover, the hypoxic status of tumor cells can be visualized by fluorescence bioimaging with very low cytotoxicity. Interestingly, the probe was successfully used for imaging an NTR-expressed microorganism, such as <i>E. coli</i>, and showed excellent antibacterial activity against <i>E. coli</i> under white light irradiation. In brief, this multifunctional probe is promising for widespread use in NTR-related biological analysis

    Cationic Oligo(thiophene ethynylene) with Broad-Spectrum and High Antibacterial Efficiency under White Light and Specific Biocidal Activity against <i>S. aureus</i> in Dark

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    We designed and synthesized a novel oligo­(thiophene ethynylene) (OTE) to investigate the antibacterial activities against Gram-positive (<i>Staphylococcus aureus</i> and <i>Staphylococcus epidermidis</i>) and Gram-negative (<i>Ralstonia solanacearum</i> and <i>Escherichia coli</i>) bacteria in vitro by photodynamic therapy (PDT). Notably, OTE presents broad-spectrum and greatly high antibacterial activities after white light irradiation at nanogram per milliliter concentrations. The half inhibitory concentrations (IC<sub>50</sub>) values obtained for <i>S. aureus</i>, <i>S. epidermidis</i>, <i>E. coli</i>, and <i>R. solanacearum</i> are 8, 13, 24, and 52 ng/mL after illumination for 30 min, respectively, which are lower than that of other PDT agents. Interestingly, OTE shows the specific and very strong dark killing capability against <i>S. aureus</i> at the concentration of 180 ng/mL for 30 min, which is the highest efficiency biocide against <i>S. aureus</i> without the need of irradiation to date. The antibacterial mechanism investigated demonstrated that reactive oxygen species or singlet-oxygen generated by OTE kills bacteria irreversibly upon white light irradiation, and OTE as a v-type oligomer exerts its toxicity directly on destroying bacterial cytoplasmic membrane in the dark. Importantly, the OTE shows no cell cytotoxicity and excellent biocompatibility. The results indicate that it is potential to provide versatile applications in the efficient control of pathogenic organisms and specific application for killing <i>S. aureus</i>

    “End-Only” Functionalized Oligo(phenylene ethynylene)s: Synthesis, Photophysical and Biocidal Activity

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    It is essential to develop alternative strategies to treat infections, especially those infections caused by Staphylococcus aureus, which is responsible for most skin infections. Among those strategies, light-induced inactivation of pathogens appears to be a promising candidate. We present four novel “end only” oligo(phenylene ethynylene)s (EO-OPE-1s) that have the ends functionalized with cationic groups and are powerful light-activated biocides against Escherichia coli, Staphylococcus epidermidis, and S. aureus. We have correlated the light-induced biocidal activities with singlet oxygen quantum yields Φ (<sup>1</sup>O<sub>2</sub>) of EO-OPE-1s, and a higher Φ (<sup>1</sup>O<sub>2</sub>) correlates with a better light-induced biocidal activity. Coupled with our previous work on the interactions of EO-OPE-1s with dioleoyl-<i>sn</i>-glycero-3-phosphocholine (DOPC)/cholesterol vesicles, we believe the biocidal process involves the following: (1) EO-OPE-1s penetrate the bacterial membrane, (2) EO-OPE-1s photosensitize the generation of singlet oxygen and/or other reactive oxygen species, and (3) singlet oxygen and/or reactive oxygen species trigger the cytotoxicity

    Blood samples were obtained from healthy controls (HC, n = 28), chronic hepatitis B (CHB, n = 18) and autoimmune hepatitis (AIH, n = 29) patients.

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    <p>Peripheral blood mononuclear cells (PBMCs) were isolated, labeled with fluorescent antibodies against CD4, CD25, CCR4 and CCR6, and analyzed by flow cytometry. (A) Plasma IL-17 and IL-23 levels. (B) Representative dot plots; and (C) Mean (±SD) percentage of Th17 (CD4<sup>+</sup>CD25<sup>−</sup> CCR4<sup>+</sup>CCR6<sup>+</sup>) cells in PBMC. Panel B and C are gated on CD4<sup>+</sup>CD25<sup>−</sup> cells. *p<0.05, **p<0.01.</p

    Characterization of the Study Participants.

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    <p>Data is shown as media and range. ALT: alanine aminotransferase; AST: aspartate aminotransferase. There is no statistical difference between all three groups in sex, age. There is no statistical difference between CHB and AIH groups in serum transaminases and histological findings.</p

    Liver biopsies were obtained from patients with either autoimmune hepatitis (AIH, n = 39) or chronic hepatitis B (CHB, n = 32).

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    <p>Th17 cells in the liver were evaluated by immunohistochemical staining of IL-17. (A) Representative histology of Th17 cells (IL-17+, brown stained cells, 400×); (B) Mean (±SD) of Th17 cells in AIH and CHB patients; (C) Mean (±SD) of hepatic inflammatory scores of AIH and CHB patients; (D) Confocal staining of CD4 (in green), IL-17 (in red) and DAPI (for nuclei in blue) in the liver of AIH patients. The frequency of Th17 cells in the liver is positively correlated with hepatic inflammatory degrees (E) and fibrosis grades (F) in AIH patients.</p
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