Browsing by Author "Lee, Cheng-Yu"

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A pyrophosphatase biosensor with photocurrent analysis
(2019-04-01)
Lee, Cheng-Yu
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Liao, Chi-Hsiang
;
Tso, Jen-Te
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Hsieh, You-Zung
;
交大名義發表
A light-induced photochemical biosensor was developed for the analysis of inorganic pyrophosphatase (PPase). PPase hydrolyzes pyrophosphate (PPi) into two independent o-phosphate ions. Two PPi units can chelate a copper ion (Cu2+), forming a PPi-Cu2+-PPi complex and preventing the Cu2+ triggers other reactions. A transparent indium tin oxide (ITO) electrode was coated with a layer of CdS quantum dots (QDs), and then 3,4-diaminobenzoic acid (DBA) was deposited as the anchor. A solution of the PPi-Cu2+-PPi complex and o-phenylenediamine (OPD) was mixed with the analytical sample and then a drop of the mixture was placed on the modified ITO electrode. In the absence of PPase, no reaction occurred between OPD and DBA. A photocurrent was obtained upon excitation of the CdS QDs under light. In the presence of PPase, Cu2+ was released from the complex, triggering the reaction of OPD with DBA on the electrode surface, thereby shielding the CdS QDs from excitation by the light. The observed photocurrent decreased. The difference in the two measured photocurrents corresponded to the activity of PPase. This photochemical biosensor had excellent sensitivity for PPase in the range from 0.8 to 5000 mU, with a limit of detection of 0.41 mU.
Analysis of Calix[4]arenes Using Nonaqueous Capillary Electrophoresis
(2013-01-01)
Su, Hsiu-Li
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Lee, Yi-Ping
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Hung, Huan-Yi
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Lee, Cheng-Yu
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Chung, Wen-Sheng
In nonaqueous capillary electrophoresis (NACE), an organic solvent is used in place of an aqueous medium as the background solution to improve the solubility and selectivity for hydrophobic analytes. In this study, we employed NACE with UV detection for the analysis of eight calix[4]arenes. We examined the influence of several parameters-the buffer composition, the nonaqueous solvent's composition and proportion, and the concentration of the electrolyte of the nonaqueous buffer-on the efficiency of the electrophoretic separation. The separation was achieved through the analyte's different effective mobility via different degrees of deprotonation on the phenolic OH groups of the calix[4]arene. This deprotonation can further affect the analyte's ability to form a complex with the metal ion. The optimized background electrolyte (BGE), comprising a mixture of N-methylformamide/acetonitrile (30:70, v/v) and 100 mM AcOH/20 mM NH4OAc, provided rapid (<11 min) separation of the calix[4]arenes with good resolution. The relative standard deviations of the migration times for the eight analytes were all less than 1%. Within the calibration concentration range, the coefficients of determination (R-2) were all greater than 0.9914. Thus, the present study demonstrated NACE can provide adequate separation for the analysis of calix[4]arenes.
Analysis of metal ion impurities in liquid crystals using high resolution inductively coupled plasma mass spectrometry
(2012-11-01)
Hung, Huan-Yi
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Lu, Chien-Wei
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Lee, Cheng-Yu
;
Hsu, Chain-Shu
;
Hsieh, You-Zung
We have developed a method, using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), to directly analyze metal ion impurities in liquid crystals (LCs). From measurements of resistivity, a commonly used technique for quality control of liquid crystal display (LCD) cells, we found that the resistivities of the LCs decreased significantly upon progressing through the different stages of the LCD cell manufacturing process. We determined the levels of metal ion impurities in the LCs through direct loading of diluted LC samples into the HR-ICP-MS system at a steady flow rate. Solutions featuring LC contents of 10% (v/v) were formed by dissolving each LC in isopropanol (IPA) containing acetone as a modifier. We quantified the trace metal ion impurities in the LC samples using a certified standard of metal ions diluted in IPA (external calibration) without the need for digestion pretreatment. Next, we compared the levels of metal ion impurities with the resistivities of the LCs at the different stages of the LCD cell manufacturing process. We confirmed that the resistivities of the LCs decreased as the total levels of metal ion impurities in the LCs increased. The total content of metal ion impurities added into the LC was higher in the siphoning process than in the one-drop filling process during the fabrication of LCD cells. The HR-ICP-MS method could, therefore, be used to directly measure metal ion impurities in LCs during the LCD cell manufacturing process, potentially replacing resistivity measurements of LCs as a means of quality control. We suggest setting 1400 ng L-1 as the limit of the total metal ion concentration in LCs used for LCD cell manufacturing. We used the HR-ICP-MS method to analyze a stained LCD panel to confirm that the content of metal ion impurities was indeed significantly greater in the stained area of the defected LCD. HR-ICP-MS appears to be a promising technique for the direct and effective analyses of metal ion impurities in LCs.
Combining aptamer-modified gold nanoparticles with barcode DNA sequence amplification for indirect analysis of ethanolamine
(2018-01-01)
Lee, Cheng-Yu
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Shiau, Ru-June
;
Chou, Han-Wen
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Hsieh, You-Zung
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應用化學系
An indirect analysis strategy for small organic molecules is presented herein, combining aptamermodified gold nanoparticles (AuNPs) with a designed barcode sequence for amplification. Ethanolamine, which could not be analyzed directly through liquid chromatography coupled with mass spectrometry (LC/MS), was used as a model compound to demonstrate the feasibility of the proposed scheme. A poly adenosine barcode sequence was part of the designed cDNA Al (cDNA + barcode sequence) to provide a large number of adenine bases for signal amplification. In the presence of fixed amounts of the aptamer and cDNA Al, the concentration of ethanolamine could be estimated indirectly through measurement of the concentration of the hydrolyzed bases of the unbound cDNA Al. The thiol-terminated aptamer was immobilized on the AuNPs through Au-S self-assembly. The aptamer-immobilized AuNPs were removed, with their bound ethanolamine and cDNA Al, through centrifugation. The unbound cDNA Al remaining in the supernatant was hydrolyzed and analyzed. Through indirect analysis and amplification of the cDNA Al, the concentration of ethanolamine could be analyzed with a linear range (on a logarithmic scale) between 5 and 5000 nM (detection limit: 1.2 nM). This developed method might be applied as a general platform for indirect detection using LC/MS analysis. (C) 2017 Elsevier B.V. All rights reserved.
Combining DNA-stabilized silver nanocluster synthesis with exonuclease III amplification allows label-free detection of coralyne
(2018-12-26)
Lee, Cheng-Yu
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Lin, Shun-Wen
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Wu, Yi-Hsuan
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Hsieh, You-Zung
;
交大名義發表
In this paper we describe a label-free biosensor for coralyne, prepared by combining DNA-stabilized silver nanoclusters (Ag NCs) with an exonuclease III amplification strategy. An artificial DNA probe having a polyadenine (poly-A) sequence at both the 3'- and 5'-ends was used as a probe to detect coralyne. In the absence of coralyne, the probe existed in a hairpin conformation that left both its 3'- and 5'-ends free. In the presence of coralyne, two adjacent adenine (A) bases in the poly-A sequence of the probe formed an A(2) unit and then coordinated with coralyne through non-Watsone-Crick base pairing. The DNA probe, having captured coralyne, was subsequently digested by exonuclease III, even though the distance between the A(2) units in the A(2)-ecoralynee-A(2) complex would be much larger than that found in common Watsone-Crick base pairing. After digestion, the DNA probe became a single-stranded DNA (ssDNA) residue and released its captured coralyne. The liberated coralyne was then coordinated by another DNA probe having the hairpin conformation; as a result, many ssDNA residues formed after digestion. Two kinds of Ag NCs having different optical utilities were obtained: one corresponding to the hairpin conformational DNA probe and the other to the ssDNA residue. The difference in fluorescence intensity at 588 nm of these two kinds of Ag NCs reflected the concentration of coralyne. The linear range (on a logarithmic scale) for detecting coralyne spanned from 5 to 1000 nM, with an estimated detection limit of 1.83 nM. (C) 2018 Elsevier B.V. All rights reserved.
Disposable aptasensor combining functional magnetic nanoparticles with rolling circle amplification for the detection of prostate-specific antigen
(2018-02-01)
Lee, Cheng-Yu
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Fan, Hsiao-Ting
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Hsieh, You-Zung
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應用化學系
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Department of Applied Chemistry
This paper describes a disposable and accurate aptasensor that functions with signal amplification for prostate-specific antigen (PSA) analysis in neutral (pH 7.4) condition. Combining aptamer-immobilized magnetic nanoparticles with rolling circle amplification (RCA) has provided a PSA detector with adequate sensitivity. In the absence of PSA, a portion of the complementary DNA-primer (cDNA-primer) bound with the aptamer and became the primer for the RCA reaction. The product of RCA contained G-rich bases that bound specifically with methylene blue (MB), thereby providing a measurable signal. In the presence of PSA, the aptamer would bind to it and fold, leading to fewer bound cDNA-primer units. Because the number of RCA primer elements decreased, the signal of MB weakened. The difference in the currents of MB measured in the presence and absence of PSA reflected the concentration of PSA. The intensity of the signal had a linear relationship with the logarithm of the PSA concentration over the range from 100 fM to 10 nM. The correlation of determination (R-2) of this calibration curve was 0.993, with a limit of detection of 22.3 fM. (C) 2017 Elsevier B.V. All rights reserved.
Functional magnetic nanoparticles-assisted electrochemical biosensor for eosinophil cationic protein in cell culture
(2018-03-01)
Lee, Cheng-Yu
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Wu, Li-Ping
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Chou, Tzu-Ting
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Hsieh, You-Zung
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應用化學系
A low-cost electrochemical biosensor, assisted by a new type of functional magnetic nanoparticles (NPs), has been developed to detect eosinophil cationic protein (ECP), a known biomarker of asthma, in cell culture. The heparin-modified magnetic NPs were mixed with a sample solution containing ECP. After ECP had been captured by the NPs, a magnetic field was applied behind a graphite-based screen-printed electrode. The functional magnetic NPs were attracted to the electrode, raising the ECP concentration near its surface. Because of the use of the functional magnetic NPs, the difference in the signal was amplified when applying larger sample volumes for detection, thereby enhancing the sensitivity of the biosensor. This approach provided a linear range for the analysis of the logarithm of the ECP concentration from 1 to 1000 nM, with a coefficient of determination 0.992; the limit of detection was 0.30 nM. The fabricated biosensor displayed good recovery in a cell culture medium incubated with the Beas-2 B cell line. The ability to detect the concentration of ECP in a cell culture at any time point should be useful for explaining contradictory findings regarding the relationship between the initial ECP concentration and the cell line. (c) 2017 Elsevier B.V. All rights reserved.
Photocatalytic performance of bipyramidal anatase TiO2 toward the degradation organic dyes and its catalyst poisoning effect
(1970-01-01)
Chan, Kuei-Lin
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Lin, Wei-Hsiang
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Chen, Fu-Jung
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Yang, Min-Han
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Jiang, Cheng-Han
It has been reported that bipyramidal anatase TiO2 with {101}-exposed facets (AT170) results in outstanding photocatalytic performance. However, its activity decayed significantly and comparatively lower than that of commercial P25 after 20 min. Further studies and calculations showed that the methylene blue (MB) degradation rate constants for AT170 were time dependent and decrease of k values with time. Besides, the results of XPS, EA and TEM could clearly elucidate that the active sites of catalysts were blocked by the carbon buildup and covered on the surface creating the metal-carbon bonding on the catalysts. These observation strongly implied the existence of the poisoning effect of AT170 during photocatalytic processes. Also, the surface area values of P25 and AT170 were found to be 46.83 and 3.56 m(2)/g respectively. It was suggested that the catalyst poisoning effect could be prevented or controlled by increasing the surface area of the catalyst. Besides of surface area, zeta potential was also found to be served as the important factor determining the photocatalytic performance toward organic dyes due to the attraction/repulsion of electrostatic interaction. The zeta potential values of P25 and AT170 were found to be - 3.8 and - 32.9 mV respectively, which can adsorb cationic MB dyes on the negative charged surface through attraction of electrostatic interaction successively enhancing the degradation performance. It strongly indicates that both surface area and zeta potential play vital roles in photocatalytic degradation toward organic dyes and affect the rate constants.
Ultrahigh-resolution optical coherence tomography/angiography with an economic and compact supercontinuum laser
(2019-11-01)
Wang, Tai-Ang
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Chan, Ming-Che
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Lee, Hsiang-Chieh
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Lee, Cheng-Yu
;
Tsai, Meng-Tsan
In this study, a Q-switch pumped supercontinuum laser (QS-SCL) is used as a light source for in vivo imaging via ultrahigh-resolution optical coherence tomography and angiography (UHR-OCT/OCTA). For this purpose, an OCT system based on a spectral-domain detection scheme is constructed, and a spectrometer with a spectral range of 635 - 875 nm is designed. The effective full-width at half maximum of spectrum covers 150 nm, and the corresponding axial and transverse resolutions are 2 and 10 mu m in air, respectively. The relative intensity noise of the QS-SCL and mode-locked SCL is quantitatively compared. Furthermore, a special processing algorithm is developed to eliminate the intrinsic noise of QS-SCL. This work demonstrates that QS-SCLs can effectively reduce the cost and size of UHR-OCT/OCTA instruments, making clinical applications feasible. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement