Fengyu Liu

Multifunctional mesoporous material for detection, adsorption and removal of Hg2+ in aqueous solution

A novel, “all-in-one”, multifunctional microsphere with a fluorescent mesoporous silica shell (Rhodamine B coordinate receptor inside) and a magnetic core (Fe3O4) has been successfully fabricated using a sol–gel method and small molecular (CTAB) surfactants as structure-directing agents. At the same time, they were examined for environmental protection applications to detect, adsorb and remove Hg2+ in aqueous solution. The prepared nanocomposite microspheres were fluorescent, mesoporous, and magnetizable, with a diameter of 300–450 nm, a surface area of 600 m2 g−1, a pore size of 2.5 nm, and a saturation magnetization of 27.5 emu g−1. These multifuctional microspheres showed excellent fluorescence sensitivity and selectivity towards Hg2+ over other metal ions (Na+, Mg2+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Ag+, Pb2+ and Cu2+). Upon the addition of Hg2+, an overall emission change of 16-fold was observed, and the detection limit of Hg2+ was as low as 10 ppb. The adsorption process of Hg2+ on the microspheres was well described by the Langmuir equation. The equilibrium can be established within five minutes and the adsorption capacity was 21.05 mg g−1. The concentration of Hg2+ ions can be reduced to less than 0.05 ppm and the used microspheres can be easily separated from the mixture by adding an external magnetic field. These results suggest that these “all-in-one” multifunctional nanocomposites are potentially useful materials for simultaneously rapidly detecting and recovering dangerous pollutants in aqueous solution.

Novel Bcl-2 Inhibitors: Discovery and Mechanism Study of Small Organic Apoptosis-Inducing Agents

Apoptosis as a novel target for cancer chemotherapy has generated an intense demand for new apoptosis‐inducing agents. The newly revealed role of protein families involved in the apoptosis pathway, and resistance to cytotoxic therapies have opened new avenues for the development of novel anticancer strategies. We have established a novel strategy to rapidly obtain protein‐targeted, instead of conventional DNA‐targeted, apoptosis inducers as antitumor leads. First, a novel organic non‐DNA intercalative compound S1 (8‐oxo‐3‐thiomorpholin‐4‐yl‐8H‐acenaphtho[1,2‐b]pyrrole‐9‐carbonitrile, MW=331) was found with an IC50 of 10−7–10−8 μM against diverse cancer cell lines. Further biological evaluation demonstrated that it was an apoptosis‐inducer both in vivo and in vitro. The treatment of hydroperitoneum hepatoma cells (H22 cell line) with S1 at various concentrations (from 0.01 to 10 μM) for 24 h triggered these cells to enter the apoptosis process. The antitumor efficiency was also tested in the H22 xenotransplant models in mice. At a dosage of 0.3 mg kg−1, S1 exhibited significant antitumor activity with a much longer survival time, a decrease in tumor size, and increased apoptosis cells in tumor tissue. More importantly, studies of the molecular mechanism of apoptosis induction by S1 revealed that S1 inactivated the Bcl‐2 protein by binding to it, depolarizing the mitochondrial membrane, and then activating caspase 9, followed by caspase 3. Finally, structure‐based virtual modification was performed by computer modeling. As a result, a derivative, S2 (8‐oxo‐3‐[(thienylmethyl)amino]‐8H‐acenaphtho[1,2‐b]pyrrole‐9‐carbonitrile, MW=341) was identified that possessed a lower binding energy to Bcl‐2, and demonstrated better antitumor potency, even on the Bcl‐2‐overexpressing human acute myeloid leukemia (HL‐60) cells (IC50=1.3 μM) in vitro. S1 and S2 are the well‐defined Bcl‐2 inhibitors that give us a promising platform for the development of new therapeutic agents.

The use of a near-infrared RNA fluorescent probe with a large Stokes shift for imaging living cells assisted by the macrocyclic molecule CB7

A near-infrared fluorescent dye Hsd was designed and synthesized, which absorbed as hemicyane and emitted as Cy7 and therefore produced a Stokes shift as large as 224 nm. Quantum chemistry calculation demonstrated that the large Stokes shift was produced by the combination of intramolecular charge transfer (ICT) and internal conversion. Significantly, Hsd showed selectively response to RNA in aqueous solution and fixed cells. Moreover, Hsd could be uptaken into the cells under the assistance of cucurbit[7]uril (CB7) and selectively stain RNA in living cells. The introducing of CB7 provides a platform to amplify the application of some cell-impermeant fluorescent stains through the supramolecular chemistry methods.

ECL performance of ruthenium tris-bipyridyl complexes covalently linked with phenothiazine through different bridge

Three ruthenium complexes 1a, 1b and 1c were synthesized, in which the phenothiazine moiety was covalently linked to the ruthenium complex through a 4 carbon chain and amide bond, respectively. The results demonstrate that one PTZ moiety is preferred to reach a good ECL performance, and the 4 carbon chain linked complex 1a exhibits the highest ECL enhancement (up to about 9 times), in comparison with the commonly utilized parent Ru(bpy)(3)(2+), permitting a lower detection limit of 1.0 x 10(-14) M with signal to noise of 3 for 20 mM DBAE at Au electrode.

Interaction of Ru(phen)3Cl2 with graphene oxide and its application for DNA detection both in vitro and in vivo

The fluorescence of Ru(phen)3Cl2 (tris(1,10-phenanthroline)ruthenium(ii) dichloride) can be effectively quenched with the addition of graphene oxide in aqueous solution, due to the formation of a GO-Ru hybrid. A fluorescence enhancement of approximately 50 times can be observed after the addition of a certain amount of DNA into the above-mentioned solution. The fluorescence increase is linearly proportional to the amount of DNA added in the concentration range of 0-70 μM and the DNA detection limit is down to 3.3 × 10-8 M. Meanwhile, it is found that the GO-Ru hybrid can enter into the nuclei and stain the DNA of living human breast cancer cells MCF-7, while Ru(phen)3Cl2 alone cannot cross the cellular membrane in the control experiment. This method can be employed to detect DNA both in vitro and in vivo.

Intra- and intermolecular interaction ECL study of novel ruthenium tris-bipyridyl complexes with different amine reductants

A series of ruthenium(II) tris-bipyridyl complexes covalently linked with different amine reductants such as tripropylamine (TPrA), ethanolamine and diethanolamine for an electrochemiluminescence (ECL) system have been synthesized. Their ECL property at different working electrodes has been studied with and without the presence of TPrA, triethanolamine (TEOA) and 2-(dibutylamino) ethanol (DBAE) as the coreactant, respectively. The results demonstrate that the conjugated ruthenium complex alone can generate ECL through intramolecular interaction at a relatively low concentration, while with intermolecular interaction the ECL intensity increases progressively and becomes increasingly dominant with increasing complex concentration. For the coreactant system ECL, the amine coreactant needed for the conjugate complexes can be significantly lowered in comparison with that of the well known [Ru(bpy)(3)](2+)/TPrA system. One amine substituent is better for the system in order to diminish the steric hindrance, and the intramolecular amine reductant employed should have a similar structure with that of the additive amine coreactant to achieve a good ECL performance, which can pave a new route to further improving the ECL efficiency and increase the sensitivity of detection through combining both intra- and intermolecular interaction.

Study of an unusual charge-transfer inclusion complex with NIR absorption, and its application for DNA photocleavage

A stable 1:1:1 ternary inclusion donor–acceptor dyad complex PTZ–MV2+–CB[8] with NIR absorption (500–1100 nm, λmax = 756 nm) can easily be obtained by use of a supramolecular method. It exhibits photocleavage ability on supercoiled plasmid DNA (pBR322), suggesting a potential application in photodynamic therapy.

Fluorescence detecting of paraquat using host-guest chemistry with cucurbit[8]uril

Paraquat (PQ) is one of the most widely used herbicides in the world, which has a good occupational safety record when used properly. While, it presents high mortality index after intentional exposure. Accidental deaths and suicides from PQ ingestion are relatively common in developing countries with an estimated 300,000 deaths occurring in the Asia–Pacific region alone each year, and there are no specific antidotes. Good predictors of outcome and prognosis may be plasma and urine testing within the first 24 h of intoxication. A fluorescence enhancement of approximately 30 times was seen following addition of PQ to a solution of the supramolecular compound 2MB@CB[8], which comprised two methylene blue (MB) molecules within one cucurbit[8]uril (CB[8]) host molecule. The fluorescence intensity was linearly proportional to the amount of PQ added over the concentration range 2.4 × 10−10 M–2.5 × 10−4 M. The reaction also occurred in living cells and within live mice.

Determination of melamine based on electrochemiluminescence of Ru(bpy)32+ at chemically converted graphene-modified glassy carbon electrode

Electrochemiluminescence (ECL) of Ru(bpy)32+ at chemically converted graphene (CCG)-modified glassy carbon (GC) electrode has been employed for the determination of melamine. It gave a linear response (R2 = 0.99) for melamine concentration from 1.0 × 10−15 mol L−1 to 1.0 × 10−11 mol L−1 with a remarkable detection limit of 1.0 × 10−15 mol L−1 in 0.1 mol L−1 phosphate buffer (pH = 10). This is much lower compared to other detection methods. To check its applicability, the proposed method was employed for the determination of melamine spiked into the milk samples, and a detection limit of 5.0 × 10−15 mol L−1 was achieved with good reproducibility and stability. All these results provide a possibility to develop an ECL method for the determination of melamine at the chemically converted graphene (CCG)-modified GC electrode.

Determination of hydrazine hydrate based on electrochemiluminescence of Ru(bpy) 3 2

Considering of the basic properties and also the two nitrogen atoms in the structure, hydrazine hydrate was employed to be an amine additive candidate, to build a Ru(bpy)32+/hydrazine electrochemiluminescence (ECL) system, and ECL of Ru(bpy)32+ has been employed for the determination of hydrazine hydrate in the paper. The result demonstrated that the logarithmic ECL increasing (ΔECL = ECLafter addition of hydrazine − ECLbefore addition of hydrazine) versus the logarithmic concentration of hydrazine hydrate is linear over a concentration range of 1.0 × 10−9 to 1.0 × 10−5 mol/L, on both glassy carbon and Pt electrodes in a pH 9 phosphate buffer. The hydrazine hydrate detection limit was down to 1.0 × 10−9 mol/L, comparatively lower than other detection methods. To check its applicability, the proposed method was applied to the determination of hydrazine hydrate added into a tap water sample with good reproducibility and stability. All these provide a possibility to develop a novel ECL detection method for hydrazine in water.