Yaowen Chen

Shantou University, Swatow, Guangdong, China

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Publications (22)73.65 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel and environmentally friendly reverse fluorescent immunoassay approach was proposed and utilized for sensing human chorionic gonadotropin (HCG) in human serum by coupling a newly prepared and highly fluorescent glutathione-stabilized silver-gold nano-alloy (GSH-AgAuNAs) with magnetic nanoparticles (MNPs). To construct such a reverse system, fluorescent GSH-AgAuNAs and MNPs were first prepared and bio-functionalized with monoclonal antibodies (Mab-I and Mab-II) toward HCG antigen, respectively. Then, the GSH-AgAuNAs functionalized with Mab-I were incubated with HCG, followed by the addition of MNPs attached to Mab-II. Thereafter, a sandwich-type immunoassay could be constructed for determination of HCG owing to the antibody-antigen recognition between the functionalized GSH-AgAuNAs and MNPs. Afterwards, a magnetic collection was employed. Hence, the amount of GSH-AgAuNAs would be reduced through an immuno-magnetic separation, thus weakening the fluorescent intensity. Different from conventional immunoassay, our work determined the quantitative signal by measuring the decreasing gradient fluorescent intensity. Under optimal conditions, the developed reverse method exhibited a wide linear range of 0.5-600 ng mL(-1) toward HCG with a detection limit of 0.25 ng mL(-1). Additionally, the proposed immunoassay was validated using spiked samples, illustrating a satisfactory result in practical application.
    Analytical and Bioanalytical Chemistry 11/2015; DOI:10.1007/s00216-015-9144-x · 3.44 Impact Factor
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    ABSTRACT: A new and environmentally friendly approach for the preparation of glutathione-stabilized silver–gold nano-alloys (GSH-AgAuNAs) with high fluorescence was proposed in this work. The as-prepared GSH-AgAuNAs were characterized with various methods and coupled with copper ions (Cu2+) to form a fluorescent switch probe (GSH-AgAuNAs/Cu2+ combination) for the detection of L-histidine. The fluorescence of the GSH-AgAuNAs was first quenched by adding an appropriate amount of Cu2+ solution. Then, in the presence of L-histidine, the GSH-AgAuNAs/Cu2+ combination solution exhibited an obvious fluorescence enhancement due to the specific interaction between the imidazole group of L-histidine and Cu2+. The strong chelation between L-histidine and Cu2+ illustrated the feasibility of constructing a selective “switch on” probe for the detection of L-histidine over other amino acids. Different from other methods for detecting L-histidine based on fluorescent nanomaterials, our work promises high selectivity, simplicity and the avoidance of organic solvents. Under the optimal conditions, the newly constructed GSH-AgAuNAs/Cu2+ fluorescent probe showed a satisfactory linear detection range of 2 to 40 μM, with a detection limit of 1.19 μM. The practical use of the GSH-AgAuNAs/Cu2+ combination in real human serum samples was tested, illustrating its potential application in L-histidine detection.
    New Journal of Chemistry 09/2015; 39(11). DOI:10.1039/C5NJ01819F · 3.09 Impact Factor
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    Xiang Huang · Yuqin Li · Xiaoshan Zhang · Xin Zhang · Yaowen Chen · Wenhua Gao ·
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    ABSTRACT: An efficient aptasensor was developed in which graphene oxide (GO) was employed as an indicator for both electrochemical impedance spectroscopy and electrochemiluminescence (ECL) signal generation. The aptasensor was fabricated by self-assembling the ECL probe of thiolated adenosine triphosphate binding aptamer (ABA) tagged with Ru complex (Ru(bpy)32+ derivatives) onto the surface of gold nanoparticles (AuNPs) modified glassy carbon electrode (GCE). ABA immobilized onto AuNPs modified GCE could strongly adsorb GO due to the strong π-π interaction between ABA and graphene oxide, ECL quenching of the Ru complex then takes place because of energy transfer and electron transfer, and a large increase of the electron transfer resistance (Ret) of the electrode. While, in the presence of target adenosine triphosphate (ATP), the ABA prefers to form ABA-ATP bioaffinity complexes, which have weak affinity to graphene oxide and keep the graphene oxide away from electrode surface, thus allowing the ECL signal enhancement, and in conjunction with the decrease of the Ret. Because of the high ECL quenching efficiency, unique structure, and electronic properties of graphene oxide, the Ret and ECL intensity versus the logarithm of ATP concentration was linear in the wide range from 10 pM to 10 nM with an ultra-low detection limit of 6.7 pM, 4.8 pM, respectively. The proposed aptasensor exhibited excellent reproducibility and stability, outstanding selectivity, and ATP could be effectively distinguished from its analogues. More significantly, this efficient ECL aptasensor strategy based on GO as both electrochemical and ECL signal indicator is general and can be easily extended to other biological binding events. Keywords: Graphene oxide; Electrochemical impedance spectroscopy; Electrochemiluminescence; Aptasensor; ATP;
    The Analyst 07/2015; 140(17). DOI:10.1039/C5AN00769K · 4.11 Impact Factor
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    ABSTRACT: Efficient and stable quenching of electrochemiluminescence (ECL) of tris(2,2'-bipyridine)-ruthenium(II) (Ru(bpy)3(2+))/tri-n-propylamine (TPrA) system by graphene oxide (GO) at the glassy carbon electrode (GCE) was reported. For figuring out the possible reasons of the quenching mechanism, the electrochemical and ECL performance of GO, different reduction degree of reduced graphene oxide (RGOs) and polymer wrapped GO modified GCEs were systematacially investigated. The results demonstrated that the oxygen-containing groups and poor electrical conductivity of GO, along with the distance between GO and Ru(bpy)3(2+) was suggested as the reasons for quenching ECL. On the basis of this essential quenching mechanism, a novel "signal on" ECL DNA biosensor for ultrasensitive detection of specific DNA sequence was constructed by self-assembling the ECL probe of thiolated shared-stem hairpin DNA (SH-DNA) tagged with Ru complex (Ru(bpy)3(2+) derivatives) on the surface of GO/gold nanoparticles (AuNPs) modified GCE. The ECL probe sequences have their ECL signal efficiently quenched when they are self-assembled on the surface of GO unless they hybridizes with their target DNA (t-DNA) sequence. The designed ECL biosensor exhibited excellent stability and reproducibility, outstanding selectivity, and an extremely sensitive response to t-DNA in a wide linear range of 100aM-10pM with a low detection limit of 65aM. Our findings and the design of biosensing switch would open a new avenue in the application of GO based ECL quenching strategy for ultrasensitive bioassays. Copyright © 2015 Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 03/2015; 70:441-446. DOI:10.1016/j.bios.2015.03.072 · 6.41 Impact Factor
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    Xiaopeng Huang · Yuqin Li · Xiang Huang · Yaowen Chen · Wenhua Gao ·
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    ABSTRACT: An ingenious sensing strategy for detecting thrombin in human serum has been developed on the basis of a hairpin DNA sequence and resonance light scattering (RLS) technique. A thrombin aptamer sequence was embedded inside the hairpin DNA strand (H-eTBA), which was designed to be the loop-stem structure. Moreover, methylene blue (MB) was utilized as the RLS signal indicator according to its different affinity to single or double stranded DNA. Upon the addition of thrombin, the thrombin aptamer inside H-eTBA interacted specifically with thrombin. Thus the conformation of H-eTBA would change. After the introduction of the DNA strand (CTBA), which was complementary to H-eTBA, the amount of double stranded DNA would decrease as a consequence. Later when MB solution was added, the RLS signal would present various response value based on different amount of thrombin. The determination of thrombin in human serum could be obtained with a detection limit of 0.32 nM and this specific sensor could be applied to detect thrombin practically. Furthermore, this aptasensor showed quite good selectivity and simplicity toward thrombin. Finally, the proposed sensing method showed its superiority with selectivity and practicability, which could be used as a simple platform for thrombin detection.
    RSC Advances 03/2015; 5(38). DOI:10.1039/C4RA14729D · 3.84 Impact Factor
  • Bangrong Zhuo · Yuqin Li · Xiang Huang · Yuejuan Lin · Yaowen Chen · Wenhua Gao ·
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    ABSTRACT: In this work, we tactfully constructed an electrochemiluminescence (ECL) aptasensing platform with ferrocene-graphene nanosheets (Fc-GNs) using the ferrocene (Fc) as quench unit to tris(2.2′-bipyridyl) ruthenium (II) [Ru(bpy)32+] and the Ru(bpy)32+ tagged thrombin binding aptamer (Ru-TBA) to recognize the thrombin molecules. Duing to the unique π-π interaction between nucleotides and graphene, the Ru-TBA could be preferentially adsorbed on the surface of ferrocene-graphene nanosheets with the signal generator into off-state. The conformational transformation of Ru-TBA leads to the desorption of Ru-TBA from Fc-GNs after the biosensing electrode incubating with the thrombin solution and the ECL “signal-on” was triggered. With the transformation of luminescence signal from “off” to “on”, the biosensor exhibited high sensitivity for the determination of thrombin with a detection limit of 0.21 nM. Particularly, the proposed method could be widely applied to the aptamer-based determination of other target analytes.
    Sensors and Actuators B Chemical 03/2015; 208:518-524. DOI:10.1016/j.snb.2014.11.064 · 4.10 Impact Factor
  • Xiaopeng Huang · Yingjie Li · Jiahong Pan · Fushen Lu · Yaowen Chen · Wenhua Gao ·
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    ABSTRACT: Although numerous methods have been reported for the analysis of creatinine in human serum, the development of a simple, rapid, and practical sensor still remains a great challenge. In this work, a hierarchical colorimetric sensor was demonstrated based on the anti-aggregation effect of glutathione (GSH)-protected gold nanoparticles (AuNPs). Creatinine molecule could induce the aggregation of AuNPs, and the system could show blue color simultaneously. When GSH was added to incubate with AuNPs in advance, the solution could perform a hierarchical color change corresponding to different concentration of creatinine. Consequently, the change of AuNPs in size resulted in the difference of resonance light scattering (RLS) intensity and the quantitative detection of creatinine could be achieved. Meanwhile, the determination of creatinine in human serum could be attained with a detection limit of 1.21 μM, and the colorimetric sensor could be applied to detect creatinine in human serum successfully in a wide range from 10 to 1000 μM. As above, the creatinine in human serum could be distinguished using proper concentration of GSH. More practically, we could identify if the sample exceeded or below the critical value with our naked eye. This sensing proposal was accompanied with prominent simplicity, speediness, and practicability clinically.
    Plasmonics 02/2015; 10(5). DOI:10.1007/s11468-015-9907-4 · 2.24 Impact Factor
  • Bangrong Zhuo · Yuqin Li · An Zhang · Fushen Lu · Yaowen Chen · Wenhua Gao ·
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    ABSTRACT: A solid-state electrochemiluminescence (ECL) biosensor based on a DNA-modified electrode platform that depends on the variation of π–π interaction before and after the binding of target analytes is put forward. The single-stranded DNA (ssDNA) probe was successfully assembled on the surface of a glassy carbon electrode (GCE), which was pre-modified with Ru(bpy)32+ complex and gold nanoparticles (GNPs). The ssDNA probe could strongly adsorb graphene due to the strong π–π interaction between nucleotides and graphene (GN), while in the presence of Hg2+, the conformational transformation of DNA from a single-stranded to a double-stranded structure resulted in inhibited adsorption of GN. With thymine (T)-rich ssDNA as a Hg2+ probe, we prepared the ECL biosensor by using ferrocene–graphene (Fc–GN) as a quenching unit to quench the ECL emission of Ru(bpy)32+, and the Hg2+ can be detected by quenching efficiency transformation when the Fc–GN gets away from Ru(bpy)32+. The biosensor exhibited a sensitive response to various ranges of concentration of Hg2+ with a detection limit of 18 pM. The ECL biosensor held great promise in the highly sensitive and selective detection of Hg2+ in natural water.
    05/2014; 2(21). DOI:10.1039/C4TB00115J
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    ABSTRACT: Biosensor based on DNA hybridization holds great potential to get higher sensitivity as the optimal DNA hybridization efficiency can be achieved by controlling the distribution and orientation of probe strands on the transducer surface. In this work, an innovative strategy is reported to tap the sensitivity potential of current electrochemiluminescence (ECL) biosensing system by dispersedly anchoring the DNA beacons on the gold nanoparticles (GNPs) array which was electrodeposited on the glassy carbon electrode surface, rather than simply sprawling the coil-like strands onto planar gold surface. The strategy was developed by designing a "signal-on" ECL biosensing switch fabricated on the GNPs nanopatterned electrode surface for enhanced ultra-sensitivity detection of Hg(2+). A 57-mer hairpin-DNA labeled with ferrocene as ECL quencher and a 13-mer DNA labeled with Ru(bpy)3(2+) as reporter were hybridized to construct the signal generator in off-state. A 31-mer thymine (T)-rich capture-DNA was introduced to form T-T mismatches with the loop sequence of the hairpin-DNA in the presence of Hg(2+) and induce the stem-loop open, meanwhile the ECL "signal-on" was triggered. The peak sensitivity with the lowest detection limit of 0.1nM was achieved with the optimal GNPs number density while exorbitant GNPs deposition resulted in sensitivity deterioration for the biosensor. We expect the present strategy could lead the renovation of the existing probe-immobilized ECL genosensor design to get an even higher sensitivity in ultralow level of target detection such as the identification of genetic diseases and disorders in basic research and clinical application.
    Biosensors & Bioelectronics 05/2013; 49C:139-145. DOI:10.1016/j.bios.2013.05.013 · 6.41 Impact Factor
  • Wenhua Gao · Jing Xi · Yunsheng Chen · Song Xiao · Yuejuan Lin · Yaowen Chen ·
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    ABSTRACT: A facile and one-step colorimetric detection of hydrazine has been developed for the first time during the formation of size-controlled amidosulfonic acid capped gold nanoparticles (AA-AuNPs). Hydrazine served not only as a target analyte but also a reductant to react with chloroauric acid (HAuCl4). In order to obtain size-controlled gold nanoparticles (AuNPs), the amidosulfonic acid (AA) was used as a stabilizer. In the presence of AA, different aggregation states of AuNPs, which exhibited distinct color changes, were obtained by varying the concentration of hydrazine. Furthermore, the changes of color resulted in different ultraviolet visible (UV-Vis) absorptions, which realized quantitative analysis of hydrazine. The detection results indicated that the proposed method exhibited good performance for hydrazine determination with a wide linear range from 1.0 x 10(-7) to 2.53 x 10(-4) M (r = 0.9915) and a low detection limit of 8.53 x 10(-8) M. The proposed method was successfully used in detecting hydrazine in various real water samples with high selectivity, sensitivity and reliability. Even outdoors, the proposed method could also be applied in real time to determine whether the hydrazine concentration was permitted or not in water samples via the visible color change.
    Analytical methods 11/2012; 4(11):3836. DOI:10.1039/c2ay25730k · 1.82 Impact Factor
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    ABSTRACT: We developed a novel electrochemiluminescence (ECL) ethanol biosensor based on [Formula: see text] and alcohol dehydrogenase (ADH) immobilized by graphene/bovine serum albumin composite film. The graphene film was directly formed on a glassy carbon electrode surface via an in situ reduction of graphene oxide (GO) and [Formula: see text] was immobilized during its formation. The graphene film acted as both a decorating agent for immobilization of [Formula: see text] and a matrix to immobilize bovine serum albumin (BSA), meanwhile BSA not only acted as a reductant to reduce GO, but also provided a friendly environment for ADH immobilization. Furthermore, ADH was separated from [Formula: see text] by the electron-conductive graphene/BSA composite film to retain its enzymatic activity. The experimental results indicated that the biosensor had excellent electrochemical activity, ECL response to ethanol and stability. Such a design of [Formula: see text] -graphene/BSA film to modify electrode holds a great promise as a new biocompatible platform for the development of enzyme-based ECL biosensors.
    Biosensors & Bioelectronics 10/2012; 41(1). DOI:10.1016/j.bios.2012.10.005 · 6.41 Impact Factor
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    ABSTRACT: A simple, cost-effective, and rapid colorimetric method for hydrazine detection using tryptophan-caped gold nanoparticles (Trp-AuNPs) has been developed. Tryptophan (Trp) is a protein with reducibility and amino group which can reduce chloroauric acid (HAuCl4) to AuNPs and modify the surface of AuNPs simultaneously. The Trp-AuNPs could be used to quantitatively detect hydrazine and showed different responses to vary concentration of hydrazine in an aqueous solution based on the aggregation-induced color change of Trp-AuNPs. The real water sample analysis verified the conclusion. The sensitivity of the detection system was influenced by the size of AuNPs which is determined by the pH of the detection system, the concentration of Trp, and the react time. We found that higher temperature contributed to more rapidly results. The detection system can detect as low as 1 μM hydrazine. We expect our approach to have wide-ranging applications in the developing region for monitoring water quality in some areas.
    Journal of Spectroscopy 10/2012; 2013(1). DOI:10.1155/2013/517613 · 0.54 Impact Factor
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    ABSTRACT: A rapid and efficient dual preconcentration method of on-line single drop liquid-liquid-liquid microextraction (SD-LLLME) coupled to sweeping micellar electrokinetic chromatography (MEKC) was developed for trace analysis of three antihistamines (mizolastine, chlorpheniramine and pheniramine) in human urine. Three analytes were firstly extracted from donor phase (4 mL urine sample) adjusted to alkaline condition (0.5 M NaOH). The unionized analytes were subsequently extracted into a drop of n-octanol layered over the urine sample, and then into a microdrop of acceptor phase (100 mM H(3)PO(4)) suspended from a capillary inlet. The enriched acceptor phase was on-line injected into capillary with a height difference and then analyzed directly by sweeping MEKC. Good linear relationships were obtained for all analytes in a range of 6.25 × 10(-6) to 2.5 × 10(-4)g/L with correlation coefficients (r) higher than 0.987. The proposed method achieved limits of detections (LOD) varied from 1.2 × 10(-7) to 9.5 × 10(-7)g/L based on a signal-to-noise of 3 (S/N=3) with 751- to 1372-fold increases in detection sensitivity for analytes, and it was successfully applied to the pharmacokinetic study of three antihistamines in human urine after an oral administration. The results demonstrated that this method was a promising combination for the rapid trace analysis of antihistamines in human urine with the advantages of operation simplicity, high enrichment factor and little solvent consumption.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 08/2012; 904:121-7. DOI:10.1016/j.jchromb.2012.07.032 · 2.73 Impact Factor
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    ABSTRACT: A facile, low-cost and effective electrochemiluminescence (ECL) sensor based on Ru(bpy)32+ immobilized by graphene film without any auxiliary medium had been developed for the first time. The graphene film was directly formed on a glassy carbon electrode surface via an in situ wet-chemical reduction of graphene oxide (GO). It had fast electron-transfer rate and excellent stability for immobilizing Ru(bpy)32+ via π–π interaction. The cyclic voltammetry result indicated that the ECL sensor had high electrochemical activity. Moreover, ECL behaviors of this sensor were investigated in details using tripropylamine as the model. And the experimental results indicated that the sensor had excellent ECL efficiency and long-term stability. Furthermore, the sensor was successfully applied to detect oxalate in urine samples with high selectivity, sensitivity and reliability, which suggested the ECL sensor could be applicable for real sample analysis.
    Sensors and Actuators B Chemical 08/2012; 171-172:1159-1165. DOI:10.1016/j.snb.2012.06.056 · 4.10 Impact Factor
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    ABSTRACT: In the present work, we showed a novel method to synthesize cyano-functionalized multiwalled carbon nanotubes (MWCNTs-CN) and utilize it as a solid-phase extraction sorbent for preconcentration of phenolic compounds in environmental water samples. MWCNTs-CN was synthesized through surface functionalization of multiwalled carbon nanotubes (MWCNTs). The functional groups on the surface of modified MWCNTs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The analytical procedure was based on a conventional solid-phase extraction step for which 100 mg of MWCNTs-CN were packed in a 3 mL polypropylene cartridge. Analytes were thus isolated and preconcentrated from the pretreated samples and subsequently detected on high-performance liquid chromatography-ultraviolet detection. The results showed the proposed method exhibited good sensitivity and precision for the extraction and elution of analytes. The limit of detections (S/N = 3) of the method were 0.45, 0.09, 0.08, and 3.00 ng mL(-1) for p-chlorophenol, 1-naphthol, 2-naphthol, and 2,4-dichlorophenol, respectively. The mean relative recoveries (n = 3) were between 80.28 and 103.13%, and the repeatability (RSD ≤ 5.10%) and reproducibility (RSD ≤ 7.68%) were accepted. This developed method was applied to determine phenolic compounds in environmental water samples. There is a positive result only for 2-naphthol with concentration of 0.38 ng mL(-1) in seawater sample.
    Journal of Separation Science 08/2012; 35(15):1967-76. DOI:10.1002/jssc.201200045 · 2.74 Impact Factor
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    Jia Ni · Kai-Ju Wei · Yuanzeng Min · Yaowen Chen · Shunze Zhan · Dan Li · Yangzhong Liu ·
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    ABSTRACT: Reactions of CuX (X = Br(-), I(-) or CN(-)) with various types of 2,2'-dipyridylamine (dpa) derivatives have been performed via a hydrothermal-solvothermal method and the products have been structurally characterized by X-ray crystallography. Four ligands with different coordination motifs were employed in the reactions, including angular N,N,N',N'-tetra(2-pyridyl)-2,6-pyridinediamine (tppda); linear N,N,N',N'-tetra(2-pyridyl)-1,4-phenylenediamine (tppa) and N,N,N',N'-tetra(2-pyridyl)biphenyl-4,4'-diamine (tpbpa); and star-shaped tris-[4-(2,2'-dipyridylamino)-phenyl]amine (tdpa), which yielded eight copper(I) complexes exhibiting different stoichiometries of Cu-dpa and variable coordination modes of dpa. The compound [Cu(2)(tppda)(μ-I)(2)](n) (1) forms a one dimensional (1D) coordination polymer exclusively through double μ(2)-I bridges, which arranges to two dimensional (2D) metal-organic frameworks (MOFs) via the face-to-face π···π stacking interactions from pyridyl rings. The compound [Cu(6)(tppa)(μ(3)-Br)(6)](n) (2) forms a 2D network linked through multiple μ(3)-Br bridges. The compound [Cu(2)(tppa)(μ-CN)(2)](n) (3) is also a 2D MOF containing 1D (CuCN)(n) chains. The compounds [Cu(tpbpa)Br](n) (4) and [Cu(4)(tpbpa)(2)(μ-I)(4)](n) (5) display two different 1D assemblies: a zig-zag chain for 4 and a linear structure for 5. The compound [Cu(4)(tpbpa)(μ-CN)(4)](n) (6) shows a pseudo-4,8(2) topological net, while the compound [Cu(8)(tpbpa)(μ-CN)(8)](n)·2nH(2)O (7) exhibits a three-dimensional (3D) framework containing a ···PM··· double helical structure, although both of them contain (CuCN)(n) chains. The compound [Cu(2)(tdpa)(μ-I)(2)](n) (8) is a zig-zag chain based on the star-shaped molecule tpda, in which one of three dpa-arms is free of coordination to metal ions. All complexes exhibit luminescence in the solid state.
    Dalton Transactions 03/2012; 41(17):5280-93. DOI:10.1039/c2dt12032a · 4.20 Impact Factor
  • Wenhua Gao · Nana Li · Gaopan Chen · Yanping Xu · Yaowen Chen · Shunlin Hu · Zhide Hu ·
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    ABSTRACT: Human serum albumin (HSA), a major plasma protein and plasma-derived therapeutic, interacts with a wide variety of drugs and native plasma metabolites. In this study the interactions of costunolide (CE) and dehydrocostuslactone (DE) with HSA were investigated by molecule modeling, atomic force microscopy (AFM), and different optical techniques. In the mechanism discussion, it was proved that fluorescence quenching of HSA by both of the drugs is a result of the formation of drug–HSA complexes. Binding parameters for the reactions were determined according to the Stern–Volmer equation and static quenching. The results of thermodynamic parameters ΔG0, ΔH0, and ΔS0 at different temperatures indicated that hydrogen bonding interactions play a major role in the drug–HSA associations process. The binding properties were further studied by quantitative analysis of CD, FTIR, and Raman spectra. Furthermore, AFM results showed that the dimension of HSA molecules became more swollen after binding with the drugs.Highlights► Interactions of costunolide and dehydrocostuslactone with HSA have been investigated for the first time. ► Raman spectra were used to analyze the drug–HSA interactions. ► Atomic force microscopy has been used to study the topography change of HSA by addition of the drugs. ► These results are important for the drugs containing costunolide and dehydrocostuslactone distribution and metabolism.
    Journal of Luminescence 10/2011; 131(10):2063-2071. DOI:10.1016/j.jlumin.2011.04.041 · 2.72 Impact Factor
  • Wenhua Gao · Gaopan Chen · Yaowen Chen · Nana Li · Tufeng Chen · Zhide Hu ·
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    ABSTRACT: A novel method of on-line single drop microextraction (SDME) coupled with sweeping micellar electrokinetic chromatography (MEKC) for the selective extraction and dual preconcentration of alkaloids was developed. In this technique, analytes of three alkaloids were firstly extracted from 4.0 mL basic aqueous sample solution (donor phase, 500 mM NaOH) into a layer of n-octanol at temperature 30 °C with the stirring rate of 1150 rpm, then back-extracted into the acidified aqueous acceptor (acceptor phase, 50 mM H₃PO₄) suspended at the tip of a capillary at 650 rpm. Then, the aqueous acceptor was introduced into capillary by hydrodynamic injection with a height difference of 15 cm between the inlet and outlet of capillary for 300 s, and analyzed directly by on-line sweeping MEKC. With the selective SDME, we were able to extract three alkaloids without any interfering components in human urine samples. Under the optimum conditions, the proposed method achieved limits of detections (LOD) of between 0.2 ng mL⁻¹ and 1.5 ng mL⁻¹ with 1583-3556-fold increases in detection sensitivity for three analytes, which indicated that it was a promising method for analysis of alkaloids in human urine.
    Journal of Chromatography A 08/2011; 1218(33):5712-7. DOI:10.1016/j.chroma.2011.06.074 · 4.17 Impact Factor
  • Wenhua Gao · Gaopan Chen · Yaowen Chen · Xiaoshan Zhang · Yegao Yin · Zhide Hu ·
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    ABSTRACT: A simple and novel method of single drop liquid-liquid-liquid microextraction (SD-LLLME) coupled with capillary electrophoresis (CE) for the determination of six fluoroquinolones (FQs) was developed. The method was eventually applied to extraction and preconcentration of FQs in human urine samples. Good linear relationships were obtained for all analytes in a range of 40-1000 μg L⁻¹ with the correlation coefficients from 0.9913 to 0.9995. The limit of detections (LODs) varied from 7.4 to 31.5 μg L⁻¹ at a signal-to-noise (S/N) of 3. The recoveries at two spiking levels were 81.8-104.9% with relative standard deviations <8.3%.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 02/2011; 879(3-4):291-5. DOI:10.1016/j.jchromb.2010.11.040 · 2.73 Impact Factor
  • Wenhua Gao · Gaopan Chen · Tufeng Chen · Xiaoshan Zhang · Yaowen Chen · Zhide Hu ·
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    ABSTRACT: A simple and novel method of directly suspended droplet microextraction (DSDME) combined with single drop back-extraction prior to capillary electrophoresis (CE) measurement is developed. In this technique, DSDME was firstly carried out under the maximum stirring rate for a desired time. Then, an aqueous droplet as back-extractive phase suspended at the needle tip was immersed in droplet of organic phase for back-extracted. After extraction, the aqueous droplet was transferred into a suitable vial and injected into CE for analysis. Three alkaloids were selected as model compounds for developing and evaluating the method performance. Under the optimum conditions, the enrichment factors ranged from 231 to 524. The relative standard deviations for five replicates were in the range of 4.8-8.1%. The calibration graph was linear in the range of 20-1000 ng mL(-1) yielding correlation coefficients higher than 0.9983. The limit of detections varied from 8.1 to 14.1 ng mL(-1). Human urine samples were spiked with three alkaloids standard to assess the matrix effects and satisfactory results were obtained. The advantages of this method are simplicity of operation, rapid detection, low cost, high enrichment factor and little solvent consumption.
    Talanta 02/2011; 83(5):1673-9. DOI:10.1016/j.talanta.2010.11.066 · 3.55 Impact Factor