Co-reporter:Jiahong Pan, Zengyao Zheng, Jianying Yang, Yaoyu Wu, Fushen Lu, Yaowen Chen, Wenhua Gao
Talanta 2017 Volume 166() pp:1-7
Publication Date(Web):1 May 2017
DOI:10.1016/j.talanta.2017.01.033
•The carbon quantum dots with surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC).•The simple and environmental friendly synthesis process of carbon quantum dots.•A novel, rapid and sensitive measurement for GSH without complicated procedures.A novel fluorescence sensor based on controlling the surface passivation degree of carbon quantum dots (CQDs) was developed for glutathione (GSH) detection. First, we found that the fluorescence intensity of the CQDs which was obtained by directly pyrolyzing citric acid would increased largely after the surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). In the light of this phenomenon, we designed a simple, rapid and selective fluorescence sensor based on the surface passivated CQDs. A certain and excess amount of EDC were mixed with GSH, part of EDC would form a stable complex with GSH owing to the exposed sulfhydryl group of GSH. As the synthesized CQDs were added into the above mixture solution, the fluorescence intensity of the (EDC/GSH)/CQDs mixture solution could be directly related to the amount of GSH. Compared to other fluorescence analytical methods, the fluorescence sensor we design is neither the traditional fluorescent “turn on” probes nor “turn off” probes. It is a new fluorescence analytical method that target object indirectly control the surface passivation degree of CQDs so that it can realize the detection of the target object. Moreover, the proposed method manifested great advantages including short analysis time, low cost and ease of operation.Schematic principle of GSH detection by using the surface passivated CQDs.
Co-reporter:Yingjie Li, Yuqin Li, Yaoyu Wu, Fushen Lu, Yaowen Chen, Wenhua Gao
Biosensors and Bioelectronics 2017 Volume 89(Part 1) pp:585-591
Publication Date(Web):15 March 2017
DOI:10.1016/j.bios.2016.01.082
•First to use an ECL biosensor for endonuclease EcoRI detection.•Using a signal “off” to “on” model with a low background.•Improve the limit of detection.•Have very good selectivity towards to EcoRI.•Provide a platform for detection of different endonucleases.Endonucleases cleavage of DNA plays an important role in biological and medicinal chemistry. This work was going to develop a reliable and sensitive electrochemiluminescent (ECL) biosensor for detecting endonucleases by using gold nanoparticles graphene composite (GNPs-graphene) as a signal amplifier. Firstly, the GNPs and graphene were simultaneously deposited on the glassy carbon electrode (GCE) by cyclic voltammetry. Then a stem DNA was anchored on the surface of GCE. And with a modifying DNA introduced into the electrode by DNA assembly, a strong ECL signal was obtained. After a DNA modified with ferrocene assembly to the stem DNA, the ECL signal had a sharp decrease due to the quench effect of ferrocene to and the biosensor comes into being a “off” state. With the effect of endonuclease, the ECL signal had a recovery because of the ferrocene being released and the biosensor formed a “on” state. Moreover, the recovery of ECL signal was related to the concentration of endonucleases. Combining specific defined DNA and endonuclease, this method has a potential to detect different endonucleases. In this work, we took the EcoRI as an example to identify the feasibility of ECL biosensor in applying in sensitive detection of endonucleases using a GNPs-graphene signal amplifier. Under optimal condition, the proposed biosensor obtained a low limit of detection (LOD) 5.6×10−5 U mL−1. And the stability, selectivity and reproducibility of the biosensor also were researched.
Co-reporter:Xiang Huang, Yuqin Li, Xiaoshan Zhang, Xin Zhang, Yaowen Chen and Wenhua Gao
Analyst 2015 vol. 140(Issue 17) pp:6015-6024
Publication Date(Web):06 Jul 2015
DOI:10.1039/C5AN00769K
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 a thiolated adenosine triphosphate binding aptamer (ABA) tagged with a Ru complex (Ru(bpy)32+ derivatives) onto the surface of gold nanoparticle (AuNP) modified glassy carbon electrode (GCE). ABA immobilized onto AuNP 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 the 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 to 4.8 pM, respectively. The proposed aptasensor exhibited excellent reproducibility, stability, and outstanding selectivity, and ATP could be effectively distinguished from its analogues. More significantly, this efficient ECL aptasensor strategy based on GO acting both as an electrochemical and ECL signal indicator is general and can be easily extended to other biological binding events.
Co-reporter:Xiaopeng Huang, Yuqin Li, Xiang Huang, Yaowen Chen and Wenhua Gao
RSC Advances 2015 vol. 5(Issue 38) pp:30268-30274
Publication Date(Web):16 Mar 2015
DOI:10.1039/C4RA14729D
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 values based on different amounts 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.
Co-reporter:Xiaopeng Huang, Yuejuan Lin, Jiayang Chen, Yaowen Chen, Yuqin Li and Wenhua Gao
New Journal of Chemistry 2015 vol. 39(Issue 11) pp:8569-8575
Publication Date(Web):24 Aug 2015
DOI:10.1039/C5NJ01819F
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.
Co-reporter:Xiang Huang, Xiaopeng Huang, An Zhang, Bangrong Zhuo, Fushen Lu, Yaowen Chen, Wenhua Gao
Biosensors and Bioelectronics 2015 70() pp: 441-446
Publication Date(Web):
DOI:10.1016/j.bios.2015.03.072
Co-reporter:Xiaopeng Huang;Yingjie Li;Jiahong Pan;Fushen Lu;Yaowen Chen
Plasmonics 2015 Volume 10( Issue 5) pp:1107-1114
Publication Date(Web):2015 October
DOI:10.1007/s11468-015-9907-4
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.
Co-reporter:Bangrong Zhuo, Yuqin Li, An Zhang, Fushen Lu, Yaowen Chen and Wenhua Gao
Journal of Materials Chemistry A 2014 vol. 2(Issue 21) pp:3263-3270
Publication Date(Web):31 Mar 2014
DOI:10.1039/C4TB00115J
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.
Co-reporter:Wenhua Gao, An Zhang, Yunsheng Chen, Zixuan Chen, Yaowen Chen, Fushen Lu, Zhanguang Chen
Biosensors and Bioelectronics 2013 Volume 49() pp:139-145
Publication Date(Web):15 November 2013
DOI:10.1016/j.bios.2013.05.013
•GNPs array as self-assembly platform was applied for ECL biosensor to control probe density.•Optimal sensitivity was achieved by optimizing the GNPs density on the electrode surface.•Low probe density afforded the biosensor good impedance performance.•Ultra-sensitive ECL biosensor for Hg2+ based on ferrocene quench for Ru(bpy)32+ was developed on the GNPs array platform.•New way to get even higher sensitivity of biosensor was developed by improve the substrate itself.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 Hg2+. A 57-mer hairpin-DNA labeled with ferrocene as ECL quencher and a 13-mer DNA labeled with Ru(bpy)32+ 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 Hg2+ and induce the stem-loop open, meanwhile the ECL “signal-on” was triggered. The peak sensitivity with the lowest detection limit of 0.1 nM 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.
Co-reporter:Yuqin Li, Baoxiu Jia, Hao Wang, Nana Li, Gaopan Chen, Yuejuan Lin, Wenhua Gao
Colloids and Surfaces B: Biointerfaces 2013 Volume 104() pp:311-317
Publication Date(Web):1 April 2013
DOI:10.1016/j.colsurfb.2012.12.023
The interaction of 2-mercaptobenzimidazole (MBI) with human serum albumin (HSA) was studied in vitro by equilibrium dialysis under normal physiological conditions. This study used fluorescence, ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared (FT-IR), circular dichroism (CD) and Raman spectroscopy, atomic force microscopy (AFM) and molecular modeling techniques. Association constants, the number of binding sites and basic thermodynamic parameters were used to investigate the quenching mechanism. Based on the fluorescence resonance energy transfer, the distance between the HSA and MBI was 2.495 nm. The ΔG0, ΔH0, and ΔS0 values across temperature indicated that the hydrophobic interaction was the predominant binding Force. The UV, FT-IR, CD and Raman spectra confirmed that the HSA secondary structure was altered in the presence of MBI. In addition, the molecular modeling showed that the MBI–HSA complex was stabilized by hydrophobic forces, which resulted from amino acid residues. The AFM results revealed that the individual HSA molecule dimensions were larger after interaction with MBI. Overall, this study suggested a method for characterizing the weak intermolecular interaction. In addition, this method is potentially useful for elucidating the toxigenicity of MBI when it is combined with the biomolecular function effect, transmembrane transport, toxicological testing and other experiments.Graphical abstractHighlights► The interaction of 2-mercaptobenzimidazole (MBI) with HSA studied in vitro by molecule modeling. ► The interaction of MBI with HSA studied in vitro by atomic force microscopy, CD, FTIR and Raman spectra. ► Steady state and time resolved fluorescence spectroscopy suggested that the quenching mechanism was dynamic. ► The binding parameters were determined according to the Stern–Volmer equation. ► The thermodynamic results indicated that hydrophobic interaction was the predominant force.
Co-reporter:Wenhua Gao;Ximeng Sun;Tufeng Chen;Yuejuan Lin;Yaowen Chen;Fushen Lu;Zhanguang Chen
Journal of Separation Science 2012 Volume 35( Issue 15) pp:1967-1976
Publication Date(Web):
DOI:10.1002/jssc.201200045
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.
Co-reporter:Wenhua Gao, Jing Xi, Yunsheng Chen, Song Xiao, Yuejuan Lin and Yaowen Chen
Analytical Methods 2012 vol. 4(Issue 11) pp:3836-3840
Publication Date(Web):29 Aug 2012
DOI:10.1039/C2AY25730K
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 × 10−7 to 2.53 × 10−4 M (r = 0.9915) and a low detection limit of 8.53 × 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.
Co-reporter:Wenhua Gao, Yunsheng Chen, Gaopan Chen, Jing Xi, Yaowen Chen, Jianying Yang, Ning Xu
Journal of Chromatography B 2012 Volume 904() pp:121-127
Publication Date(Web):1 September 2012
DOI:10.1016/j.jchromb.2012.07.032
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 H3PO4) 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.Highlights► A dual preconcentration method combined in an on-line mode. ► Simple and rapid operation without time-consuming matrix-transfer steps. ► High enrichment efficiencies are got in trace analysis of analytes in urine matrix. ► The method is used for pharmacokinetic of chlorpheniramine in human urine.
Co-reporter:Wenhua Gao, Gaopan Chen, Yaowen Chen, Nana Li, Tufeng Chen, Zhide Hu
Journal of Chromatography A 2011 Volume 1218(Issue 33) pp:5712-5717
Publication Date(Web):19 August 2011
DOI:10.1016/j.chroma.2011.06.074
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.
Co-reporter:Wenhua Gao, Nana Li, Gaopan Chen, Yanping Xu, Yaowen Chen, Shunlin Hu, Zhide Hu
Journal of Luminescence 2011 Volume 131(Issue 10) pp:2063-2071
Publication Date(Web):October 2011
DOI:10.1016/j.jlumin.2011.04.041
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.
Co-reporter:Wenhua Gao, Gaopan Chen, Yaowen Chen, Xiaoshan Zhang, Yegao Yin, Zhide Hu
Journal of Chromatography B 2011 Volume 879(3–4) pp:291-295
Publication Date(Web):1 February 2011
DOI:10.1016/j.jchromb.2010.11.040
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%.
Co-reporter:Wenhua Gao, Gaopan Chen, Tufeng Chen, Xiaoshan Zhang, Yaowen Chen, Zhide Hu
Talanta 2011 Volume 83(Issue 5) pp:1673-1679
Publication Date(Web):15 February 2011
DOI:10.1016/j.talanta.2010.11.066
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.
Co-reporter:Wenhua Gao, Nana Li, Yaowen Chen, Yanping Xu, Yuejuan Lin, Yegao Yin, Zhide Hu
Journal of Molecular Structure 2010 Volume 983(1–3) pp:133-140
Publication Date(Web):1 November 2010
DOI:10.1016/j.molstruc.2010.08.042
The interaction between syringin and HSA has been studied by AFM, molecule modeling, fluorescence, UV–vis, FTIR and CD spectroscopy. Fluorescence results revealed that syringin can enhance the intensity of HSA fluorescence. The enhancement data was analyzed by the equation which developed by Bhattacharya et al. The results showed that there was one primary syringin binding site on HSA with a binding constant of 2.97 × 104 M−1 at 295 K. Thermodynamic analysis by Van Hoff equation found enthalpy change (ΔH0) and entropy change (ΔS0) were −5.23 kJ mol−1 and 103.34 J mol−1 K−1 respectively, which indicated the hydrophobic interaction was the predominant force in the binding process. Competitive experiments showed a displacement of warfarin by syringin, which indicated that the binding site was located at the drug site I. AFM results revealed that the dimension of the individual HSA molecules was larger after interaction with syringin. The secondary structure compositions of free HSA and HSA–syringin complex were estimated by FTIR and CD spectra.
Co-reporter:Shao Yu Lin;Xi Kun Guo;Wen Hua Gao;Li Jia;Xing Guo Chen;Zhi De Hu
Journal of Separation Science 2005 Volume 28(Issue 1) pp:92-97
Publication Date(Web):27 DEC 2004
DOI:10.1002/jssc.200401863
A simple, rapid, reproducible, and universal non-aqueous capillary electrophoresis method has been developed for the separation and determination of three major active protoberberine alkaloids including berberine, palmatine, and jatrorrhizine within 7 min. The effects of the concentrations of acetic acid and electrolyte, the ratio of organic solvent, and the applied voltage on the separation were investigated. The optimum running buffer was composed of 50 mM ammonium acetate, 0.5% (v/v) acetic acid, and 10% (v/v) acetonitrile in methanol. The applied voltage was 18 kV. The analytes were detected by UV at 214 nm. The linearities between peak areas and the concentrations of the analytes were also investigated, and they exhibit excellent linear behavior over the concentration ranges (correlation coefficients: 0.9975–0.9986). The method was successfully applied to determine the three alkaloids in several families of herbal drugs (Rhizoma Coptidis, Cortex Berberidis, Cortex Phellodendri, Herba Chelidonii,Caulis Mahoniae) and their relevant medicinal preparations for the first time, and the recoveries of the three constituents ranged between 95.6–103.2% for berberine, 97.5–103.3% for palmatine, and 96.1–103.6% for jatrorrhizine.
Co-reporter:Shaoyu Lin;Yaowen Chen;Anjia Chen;Xingguo Chen;Zhide Hu;Yuqin Li
Journal of Separation Science 2005 Volume 28(Issue 7) pp:639-646
Publication Date(Web):27 APR 2005
DOI:10.1002/jssc.200400034
A simple, rapid, and sensitive non-aqueous capillary electrophoresis procedure with head-column field-amplified sample stacking concentration for the analysis of fangchinoline and tetrandrine is established. Optimum separation and stacking conditions were obtained when the sample was injected at 8 kV for 50 s after preliminary pressure injection of ethanol (16.9 kPa) for 0.6 s and separated with the buffer containing 50 mM ammonium acetate, 0.5% (v/v) acetic acid, and 50% (v/v) acetonitrile in methanol medium at 24 kV applied voltage. The analytes were detected by UV at 214 nm. The two bisbenzylisoquinoline alkaloids can be separated within 6 min and quantified with high sensitivity. The detection limits were 0.30 ng mL–1 for fangchinoline and 0.34 ng mL–1 for tetrandrine, which indicated that the sensitivities were at least 1000-fold enhanced over those reported in the literature as obtained by UV detection. The method was applied to the analysis of fangchinoline and tetrandrine in Radix Stephaniae tetrandrae and its medicinal preparations with good results.
Co-reporter:Wenhua Gao, Jing Xi, Yunsheng Chen, Song Xiao, Yuejuan Lin and Yaowen Chen
Analytical Methods (2009-Present) 2012 - vol. 4(Issue 11) pp:NaN3840-3840
Publication Date(Web):2012/08/29
DOI:10.1039/C2AY25730K
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 × 10−7 to 2.53 × 10−4 M (r = 0.9915) and a low detection limit of 8.53 × 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.
Co-reporter:Bangrong Zhuo, Yuqin Li, An Zhang, Fushen Lu, Yaowen Chen and Wenhua Gao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 21) pp:NaN3270-3270
Publication Date(Web):2014/03/31
DOI:10.1039/C4TB00115J
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.
