Browsing by Author "Chen, Wen-Jie"

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Carbon fiber ionization mass spectrometry coupled with solid phase microextraction for analysis of Benzo[a]pyrene
(2019-02-21)
Wu, Min-Li
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Chen, Te-Yu
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Chen, Wen-Jie
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Baig, Mirza Muhammad Fahad
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Wu, Yi-Cheng
Solid phase micro-extraction (SPME) is an effective technique that can be used to selectively enrich trace analytes of interest from complex samples. Owing to its high sensitivity and high selectivity, mass spectrometry (MS) has been widely used as the detection tool to confirm the analytes enriched on SPME fibers. Generally, thermal desorption or solvent desorption is used to desorb analytes from SPME fibers for MS analysis. A straightforward ionization method called carbon fiber ionization (CFI), which uses a single carbon fiber (diameter: similar to 10 mu m) as ionization emitter in MS, has been demonstrated lately. Analytes adsorbed on the carbon fiber, which is placed close (similar to 5 mm) to the inlet of a mass spectrometer, can be readily ionized through corona discharge and detected by the mass spectrometer. One unique feature regarding this approach over other existing ambient ionization methods is that no additional electric contact is applied directly on the carbon fiber. Nevertheless, on the basis of the electric field provided by the mass spectrometer, corona discharge can readily occur for ionizing analytes on the carbon fiber. Carbon fiber has high affinity toward polycyclic aromatic hydrocarbons due to its graphite-like surface structure. We herein explore a hyphenated-technique by combining carbon-fiber based SPME with CFI-MS for extraction of benzo[a]pyrene (BaP), a carcinogen, from aqueous samples. After BaP are adsorbed on a carbon fiber through SPME, the SPME carbon fiber can be readily placed in front of the mass spectrometer for MS analysis. The ions at m/z 252 derived from BaP adsorbed on the carbon fiber can be immediately acquired by the mass spectrometer without the requirement of applying heating or solvent. The limit of detection of BaP using the developed method was as low as similar to 60 pM. It is also feasible to detect BaP from complex serum sample. The feasibility of using the approach for quantitative analysis of BaP was also demonstrated. The linear dynamic range toward BaP was 0.2-5 nM. The extraction efficiency using this approach for aqueous samples was similar to 91%. (C) 2018 Elsevier B.V. All rights reserved.
Functional Gold Nanoparticles as Sensing Probes for Concanavalin A and as Imaging Agents for Cancer Cells
(2019-06-01)
Chen, Wen-Jie
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Kandasamy, Karthikeyan
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Chen, Yu-Chie
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應用化學系
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Department of Applied Chemistry
Concanavalin A (ConA), which exists in jack bean, can specifically bind to either mannose or glucose units. Given that ConA is a potential anticancer agent for antihepatoma therapy, analytical methods that can be used for ConA detection in plant extracts or biological fluids are important. Labeling agents that can be used to distinguish cancer cells from noncancer cells are also useful for cancer diagnostics. In this study, maltose-directed synthesis of Au nanoparticles (NPs; Au@Maltose NPs) were generated from one-pot reactions and used as sensing probes toward ConA tetrameric forms. Results showed that the binding affinity between Au@Maltose NPs and ConA was desirable with a dissociation constant as low as similar to 6.66 x 10(-8) M. Moreover, the limit of detection against ConA was estimated to be similar to 23 pM, which was the lowest ever reported when Au NPs were used as sensing probes against ConA. Moreover, Au@Maltose NPs were used as imaging agents for ConA-treated cancer cells, such as human hepatoma HepG2 cells and human breast T-47D cancer cells, which can overexpress mannose N-glycan units on the cell membrane. NIH 3T3 fibroblast cells, which are noncancer cells, were used for comparison. Results demonstrated that the imaging agent made from combined ConA and Au@Maltose NPs can be used to distinguish cancer cells from noncancer cells.
Using Dextran-encapsulated gold nanoparticles as insulin carriers to prolong insulin activity
(2017-08-01)
Lee, Kai-Chieh
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Chen, Wen-Jie
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Chen, Yu-Chie
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應用化學系
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Department of Applied Chemistry
Aim: Diabetes mellitus is commonly treated with painful insulin injections. We aim to explore drug carriers that can prolong insulin activity. Materials & methods: Dextran-encapsulated gold NPs (AuNPs@Dextran) that can bind with insulin are used as insulin carriers. The affinity (Kd = similar to 42pM) between insulin and insulin receptors on the cells is much higher than that (Kd = similar to 4.02 mu M) of insulin and AuNPs@ Dextran. Thus, insulin released from the AuNP@Dextran- insulin conjugates to maintain kinetic equilibrium and prefers to bind to the insulin receptor. The slow release of insulin from the AuNP@ Dextran-insulin conjugates facilitates the lasting of insulin activity. Results & discussion: AuNP@ Dextran-insulin conjugates can prolong insulin activity to 12 h, whereas free form insulin loses activity after 4 h in adipocyte cells. Conclusion: AuNPs@ Dextran are suitable carriers that can prolong insulin activity.