Ruiyuan Liu

A highly selective and sensitive fluorescent chemosensor for detection of CN−, SO32− and Fe3+ based on aggregation-induced emission

A novel fluorescence chemosensor 1 with aggregation-induced emission was designed and synthesized through a nucleophilic addition reaction between cyanide and triphenylamine. It exhibited remarkable selectivity and high sensitivity and was able to detect Fe3+, CN− and SO32− in almost pure aqueous solution with low detection limits of 1.44 μM, 9.88 nM and 0.107 μM, respectively. Jobs plot and 1H NMR data showed that the binding stoichiometry of 1 with Fe3+, CN− or SO32− was 1:1. Further observations of 1H NMR titration suggested that a coordination bond was formed between two cyano of 1 and Fe3+ which resulted in fluorescence quenching of 1 after detection of Fe3+, whereas the nucleophilic addition of cyanide or sulfite to the vinyl group was responsible for the fluorescent quenching of CN− or SO32− toward 1. The biological applications of 1 were also evaluated and it was found to exhibit low cytotoxicity and membrane permeability. In addition, 1 could also be made into test strips to detect Fe3+ and CN− and was employed as a sensor for detection Fe3+ in living cells.

A naked-eye chemosensor for fluoride ions: a selective easy-to-prepare test paper

A new naked-eye chromogenic chemosensor based on 2-thiohydantoin shows high selectivity for fluoride ions and is used to develop a test paper for detection of fluoride ions in the solid state.

Anti-αvβ3 antibody guided three-step pretargeting approach using magnetoliposomes for molecular magnetic resonance imaging of breast cancer angiogenesis

Purpose Pretargeting of biomarkers with nanoparticles in molecular imaging is promising to improve diagnostic specificity and realize signal amplification, but data regarding its targeting potential in magnetic resonance (MR) imaging are limited. The purpose of this study was to evaluate the tumor angiogenesis targeting efficacy of the anti-αvβ3 antibody guided three-step pretargeting approach with magnetoliposomes. Methods Polyethylene glycol-modified and superparamagnetic iron oxide-encapsulated magnetoliposomes with and without biotin were synthesized and characterized. The cytotoxicity of both probes was evaluated using the methyl thiazdyl tetrazolium assay, and their cellular uptake by mouse macrophage was visualized using Prussian blue staining. Three-step pretargeting MR imaging was performed on MDA-MB-435S breast cancer-bearing mice by intravenous administration of biotinylated anti-αvβ3 monoclonal antibodies (first step), followed by avidin and streptavidin (second step), and by biotinylated magnetoliposomes or magnetoliposomes in the targeted or nontargeted group, respectively (third step). The specificity of αvβ3 targeting was assessed by histologic examinations. Results The developed magnetoliposomes were superparamagnetic and biocompatible as confirmed by cell toxicity assay. The liposomal bilayer and polyethylene glycol modification protected Fe3O4 cores from uptake by macrophage cells. MR imaging by three-step pretargeting resulted in a greater signal enhancement along the tumor periphery, occupying 7.0% of the tumor area, compared with 2.0% enhancement of the nontargeted group (P < 0.05). Histologic analysis demonstrated the targeted magnetoliposomes colocalized with neovasculature, which was responsible for the MR signal decrease. Conclusion These results indicate that our strategy for MR imaging of αvβ3-integrin is an effective means for sensitive detection of tumor angiogenesis, and may provide a targetable nanodelivery system for anticancer drugs.

A fluorescent probe based on hydroxylnaphthalene 2-cyanoacrylate: fluoride ion detection and its bio-imaging in live cells

A novel ratiometric fluorescent probe based on hydroxylnaphthalene 2-cyanoacrylate was developed to act as a luminescent probe for biological fluoride ion detection. The probe is responsive and highly selective for fluoride ions over other common anions; it also exhibits a very low detection limit of 8.54 μM. The deprotonation of the phenol moieties leads to a fluorescent change in the probe. The biological applications of the probe were also evaluated and it was found to exhibit a low cytotoxicity, a good water solubility and membrane permeability. The probe was, therefore, employed as a sensing probe for the detection of fluoride ions in living cells.

2-Thiohydantoin containing OH and NH recognition subunits: a fluoride ion selective colorimetric sensor

A novel anion receptor based on 2-thiohydantoin, containing different hydrogen bonding donors such as OH and NH groups, was synthesized. This receptor showed a colorimetric response to fluoride ions. 1H NMR titration confirmed the deprontonation of the phenol OH group and hydrogen bonding interaction between NH group and F−.

A new fluorescent probe based on styrylcyanine dye containing pyridine: dissimilar fluorescent response to Cu2+ and Pb2+

A highly sensitive fluorescent probe (1) based on styrylcyanine dye for Cu2+ and Pb2+ has been developed. Probe 1 exhibited fluorescent turn-off sensing ability to Cu2+. On the other hand, 1 displayed ratiometric fluorescent response towards Pb2+ with a distinct fluorescent color change from blue to orange. The 1H NMR titrations revealed that the fluorescent response of 1 to Cu2+ and Pb2+ is triggered by the interaction of the pyridine unit and the metal ion. Detection limits of 1 to Cu2+ or Pb2+ were calculated as 1.24 and 3.41 × 10−6 M, respectively, by standard deviation and linear fitting. Furthermore, 1 can also be used as a sensor for detection of Cu2+ and Pb2+ in a test strip.

Thiourea-functionalized poly(phenyleneethynylene): fluorescent chemosensors for anions and cations

A novel poly(phenyleneethynylene) containing thiourea groups [poly(1)] was synthesized. The anion sensing ability of poly(1) was assessed using tetra-n-butylammonium (TBA) salts of a series of anions in DMF. The addition of F− changed the color of the polymer solution in DMF from yellow to orange and quenched the fluorescence, whereas the visible color and fluorescence of the solution only varied slightly upon the addition of Cl−, HSO4−, Br−, CH3COO−, C6H5COO−, and NO3−; this indicates that poly(1) exhibits an F− sensing ability. 1H NMR titrations of poly(1) revealed that the colorimetric and fluorescent response of poly(1) is triggered by thiourea/F− hydrogen bonding. Poly(1) also exhibited a turn-off fluorescence Ag+ sensing ability. The addition of Ag+ quenched the fluorescence of the polymer, while the addition of Pb2+, Zn2+, Cu2+, Mn2+, K+, Na+, and Co2+ resulted in only slight changes to the fluorescence. The sensor containing poly(1) and Ag+ shows a turn-on fluorescence adenosine diphosphate (ADP) sensing ability.

Thiourea based conjugated polymer fluorescent chemosensor for Cu+ and its use for the detection of hydrogen peroxide and glucose

A novel conjugated polymer, poly(1), containing thiourea moieties in main chain is synthesized via Suzuki coupling reaction. The addition of cuprous ion quenches the fluorescence of poly(1), whereas the fluorescence changes slightly upon addition of other metal ions, exhibiting the fluorescent almost turn-off sensing ability towards Cu+. When hydrogen peroxide was added to the solution containing poly(1) and Cu+, Cu+ was oxidized into Cu2+, resulting in the fluorescence recovery. The H2O2 released from glucose oxidation by glucose oxidase (GOD) also recovered the fluorescence of poly(1)/Cu+ solution. The results indicated that the poly(1)/Cu+ solution could serve as a sensing platform for hydrogen peroxide and glucose.

Organic Radical Contrast Agents Based on Polyacetylenes Containing 2,2,6,6‐Tetramethylpiperidine 1‐Oxyl (TEMPO): Targeted Magnetic Resonance (MR)/Optical Bimodal Imaging of Folate Receptor Expressing HeLa Tumors in Vitro and in Vivoa

Nitroxides have great potential as magnetic resonance imaging (MRI) contrast agents for tumor detection. Polyacetylenes(PAs) containing 2,2,6,6-tetramethyl-piperidine oxyl (TEMPO) and poly(ethylene glycol) were synthesized via metathesis polymerization of the corresponding substituted acetylenes to be used for targeted bimodal MRI /optical imaging of tumors. The poly(ethylene glycol) in the polyacetylenes enables covalent conjugation of carboxyl fluorescein and folic acid (FA) with hydroxyl groups to develop targeted multifunctional organic radical contrast agents (ORCAs). In vitro studies confirm the excellent binding specificity and subsequent enhanced cellular internalization of the targeted ORCAs (PA-TEMPO-FI-FA) without cytotoxicity. In vivo T1-weighted MRI demonstrates the active tumor targeting ability of PA-TEMPO-FI-FA to generate specific contrast enhancement in mice bearing HeLa tumors. Moreover, longitudinal optical imaging displays high tumor accumulation after 1 h post-injection of PA-TEMPO-FI-FA. These results indicate that multifunctional ORCAs may provide a tumor-targeted delivery platform for further molecular imaging guided cancer therapy.

UREA-BASED POLYACETYLENES AS AN OPTICAL SENSOR FOR FLUORIDE IONS

Novel acetylenes carrying urea groups, 1-(4-ethynylphenyl)-3-(4-nitrophenyl) urea (1), 1-(4-propargyl)-3-(4-nitrophenyl) urea (2), were synthesized and polymerized with rhodium catalyst. Polymers [poly(1) and poly(2)] with moderate molecular weights were obtained in good yields. The anion sensing ability of poly(1) and poly(2) was estimated using the tetra-n-butylammonium (TBA) salts of a series of anions in DMF. Upon the addition of F−, the color of the DMF solution of poly(1) and poly(2) immediately turned to a different color, while the color of solution changed slightly upon addition of Cl−, HSO4−, Br−, and NO3−, indicating the F− sensing ability of poly(1) and poly(2). The 1H-NMR titrations of poly(1) revealed that the colorimetric response of poly(1) was triggered by the urea/F− interaction through the hydrogen bonding and/or deprotonation process. The absorption spectra titration and Hill plot analysis were carried out to measure the F− binding ability, and the Hill coefficient in the poly(1)/F− complexation was found to be 5.8. This result clearly indicated that this binding mode between poly(1) and F− was based on a positive homotropic allosterism.