Biomedical subjects

Liqiang Zheng

Publications and source records attributed to Liqiang Zheng.

7 recordsLinked to original sources

PubMed2007

The effect of water on the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/benzene ionic liquid microemulsions.

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) forms nonaqueous microemulsions with benzene with the aid of nonionic surfactant TX-100. The phase diagram of the ternary system was prepared, and the microstructures of the microemulsion were recognized. On the basis of the phase diagram, a series of ionic liquid-in-oil (IL/O) microemulsions were chosen and characterized by dynamic light scattering (DLS), which shows a similar swelling behavior to typical water-in-oil (W/O) microemulsions. The existence of IL pools in the IL/O microemulsion was confirmed by UV/Vis spectroscopic analysis with CoCl2 and methylene blue (MB) as the absorption probes. A constant polarity of the IL pool is observed, even if small amounts of water are added to the microemulsion, thus suggesting that the water molecules are solubilized in the polar outer shell of the microemulsion, as confirmed by FTIR spectra. 1H NMR spectroscopic analysis shows that these water molecules interact with the electronegative oxygen atoms of the oxyethylene (OE) units of TX-100 through hydrogen-bonding interactions, and the electronegative oxygen atoms of the water molecules attract the electropositive imidazolium rings of [bmim][BF4]. Hence, the water molecules are like a glue that stick the IL and OE units more tightly together and thus make the microemulsion system more stable. Considering the unique solubilization behavior of added water molecules, the IL/O microemulsion system may be used as a medium to prepare porous or hollow nanomaterials by hydrolysis reactions.

Benzene↗

PubMed2007

Evaluation of medical treatment for peripheral arterial disease in Chinese high-risk patients.

BACKGROUND: Peripheral arterial disease (PAD) is an important manifestation of systemic atherosclerosis and is associated with elevated cardiovascular morbidity and mortality. The aim of the present study was to evaluate the use of antiplatelet agents, statins and angiotensin-converting enzyme inhibitors (ACEI) in Chinese high-risk cardiovascular (CV) patients with PAD, with an emphasis on the need for aggressive medical management of all atherosclerotic manifestations. METHODS AND RESULTS: Medical records from 5,263 Chinese patients at high risk of CV were evaluated for the use of antiplatelet agents, statins and ACEI in patients with and without PAD. PAD was defined as an ankle-brachial index (ABI)<0.9 in either leg. Multivariable logistic regression analyses were performed to compare medication use in the 2 groups. A total of 5,254 patients were analyzed (52.9% male, mean age 67.3 years). The prevalence of PAD in the total patient group was 25.4%; 22.5% of them had PAD only. Overall, 5.7% had PAD only, 19.6% had PAD and coronary heart disease (CHD) or stroke or diabetes, 7.7% had CHD only, 12.6% had stroke only, and 13.6% had diabetes only. The 28.9% subjects having none of PAD, CHD, stroke or diabetes were used as the reference group. Only 65%, 37% and 47% of all patients received antiplatelet agents, statins and ACEI, respectively. Antiplatelets, statins, ACEI and all 3 medications were used less frequently in PAD only patients (58.1%, 35.9, 53.5% and 21.6%) vs CHD only (90.9%, 74.5%, 70.6% and 55.9%, p<0.001). All 3 proven efficacious therapies were prescribed for only 56% of patients with CHD only, 8% with stroke only, 13% with diabetes only and 21% with PAD only. CONCLUSION: PAD is prevalent in Chinese high-risk CV patients, equivalent to CHD, but these patients receive less intensive treatment than those with CHD. Programs to improve CV risk reduction in these high-risk patients are needed.

Aged↗

PubMed2006

Structural studies of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/ p-xylene ionic liquid microemulsions.

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) forms nonaqueous microemulsions with p-xylene, with the aid of the nonionic surfactant TX-100. The phase behavior of the ternary system is investigated, and three microregions of the microemulsions-ionic liquid-in-oil (IL/O), bicontinuous, and oil-in-ionic liquid (O/IL)-are identified by conductivity measurements, according to percolation theory. On the basis of a phase diagram, a series of IL/O microemulsions are chosen and characterized by dynamic light scattering (DLS). The size of aggregates increases on increasing the amount of added polar component (bmimBF(4)), which is a similar phenomenon to that observed for typical water-in-oil (W/O) microemulsions, suggesting the formation of IL/O microemulsions. The microstructural characteristics of the microemulsions are investigated by FTIR and 1H NMR spectroscopy. The results indicate that the interaction between the electronegative oxygen atoms of the oxyethylene (OE) units in TX-100 and the electropositive imidazolium ring may be the driving force for the solubilization of bmimBF4 into the core of the TX-100 aggregates. In addition, the micropolarity of the microemulsions is investigated by using methyl orange (MO) as a UV/Vis spectroscopic probe. A relatively constant polarity of the microemulsion droplets is obtained in the IL microemulsion. Finally, a plausible structure for the IL/O microemulsion is presented.

Journal Article↗

PubMed2006

Microregion detection of ionic liquid microemulsions.

Nonaqueous ionic liquid (IL) microemulsion consisting of IL, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)), surfactant TX-100, and toluene was prepared and the phase behavior of the ternary system was investigated. Electrical conductivity measurement was used for investigating the microregions of the nonaqueous IL microemulsions. On the basis of the percolation theory, the bmimBF(4)-in-toluene (IL/O), bicontinuous, and toluene-in-bmimBF(4) (O/IL) microregions of the microemulsions were successfully identified using insulative toluene as the titration phase. However, this method was invalid when conductive bmimBF(4) acted as the titration phase. The microregions obtained by conductivity measurements were further proved by electrochemical cyclic voltammetry experiments. The results indicated that the conductivity method was feasible for identifying microstructures of the nonaqueous IL microemulsions.

Journal Article↗

PubMed2006

Inclusion complexes of beta-cyclodextrin with ionic liquid surfactants.

The three kinds of ionic liquid (IL) surfactants, 1-dodecyl-3-methylimidazolium hexafluorophosphate (C(12)mimPF(6)), 1-tetradecyl-3-methylimidazolium hexafluorophosphate (C(14)mimPF(6)), and 1-hexadecyl-3-methylimidazolium hexafluorophosphate (C(16)mimPF(6)), were used to form the inclusion complexes (ICs) with beta-cyclodextrin (beta-CD). The surface tension measurements revealed that there were two kinds of inclusion formations, 1:1 and 1:2 (beta-CD/IL) stoichiometry for beta-CD-C(12)mimPF(6) and beta-CD-C(14)mimPF(6) ICs, and only 1:1 stoichiometry for beta-CD-C(16)mimPF(6) ICs. These inclusion compounds were further characterized by XRD, (13)C CP/MAS NMR, (1)H NMR, rotating frame nuclear Overhauser effect spectroscopy (ROESY), and thermogravimetry (TGA). The results showed that these ICs were fine crystalline powder. The host-guest system presented a channel-type structure, and each glucose unit of beta-CD was in a similar environment. It was suggested that hydrophobicity played a crucial role in supporting the formation of ICs. The decomposition temperature of these ICs was lower than those of their precursors. Furthermore, the possible inclusion structures were also speculated. These inclusion behaviors are likely to be used to recover ILs in the process of their preparation.

Imidazoles↗

PubMed2006

Study of the Pm3n space group of cubic mesoporous silica.

By using a Gemini surfactant, [C14H25N+(CH3)2-(CH2)2-N+(CH3)2C14H25]2 Br-(C(14-2-14)), with a short spacer group (s = 2) as structure-directing agent and sodium silicate as precursor, high-quality, ordered cubic mesoporous silica with space group Pm3n was prepared by the S+I-route (S = surfactants, I = precursor). The samples were characterized by small-angle X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption. The results showed that the pore structure of the resulting mesoporous silica belonged to the cubic system (space group Pm3n). The unit-cell parameter of the cubic system was in the range of 8.81-9.14 nm. The high-quality cubic mesoporous structure was formed at molar ratios of C(14-2-14) to sodium silicate of 0.33:1 to 0.16:1 and a molar ratio of ethyl acetate to sodium silicate of 2:1. N2 adsorption-desorption curves revealed type IV isotherms and H1 hysteresis loops. The primary pore volume, and the most probable pore size according to the Barrett-Joyner-Halenda (BJH) model, increased with increasing molar ratio of C(14-2-14) to sodium silicate.

Journal Article↗

PubMed2005

Effect of sucrose on the structure of a cubic phase formed from a monoolein/water mixture.

The effect of sucrose on the structure of molecular assemblies formed in an MO/H2O mixture has been studied using a small-angle X-ray scattering method. It was found that the phase transition Ia3d --> Pn3m --> H(II) occurs with increased sucrose concentration in the mixture with the composition 70 wt% MO at 20 degrees C. This structural change induced by sucrose addition would be ascribed to a cosmotropic property of sucrose, which leads to the dehydration of the MO head group and hence causes a decrease in the effective area occupied by the MO molecule at the polar/apolar interface, which facilitates the formation of molecular assemblies with a high curvature for the reversed liquid-crystal mesophase.

Glycerides↗