Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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Anal. Chem. 2010, 82, 6814–6820 Screening Assay of Very Long Chain Fatty Acids in Human Plasma with Multiwalled Carbon Nanotube-Based Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Wei-Yi Hsu, † Wei-De Lin, †,‡ Wuh-Liang Hwu, § Chien-Chen Lai,* ,‡,| and Fuu-Jen Tsai* ,†,|,& Department of Medical Research, China Medical University Hospital, Taichung, Taiwan, Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan, Department of Medical Genetics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan, Graduate Institute of Chinese Medical Science, China Medical University, Taichung, Taiwan, and Department of Health and Nutrition Biotechnology, Asia University, Taichung, Taiwan Peroxisomal disorders are characterized biochemically by elevated levels of very long chain fatty acids (VLCFAs) in serum. Herein, we describe a novel approach for quantification of VLCFAs in serum, namely, eicosanoic acid (C20:0), docosanoic acid (C22:0), tetracosanoic acid (C24:0), and hexacosanoic acid (C26:0). The methodology is based on (i) enrichment of VLCFA derivatives using multiwalled carbon nanotubes (MWCNTs); (ii) quantification using stable isotope-labeled internal standards; and (iii) direct detection using MWCNT-based surface-assisted laser desorption/ionization-time-of-flight mass spectrometry (SALDI-TOFMS). Four kinds of MWCNTs (Aldrich 636843, 636495, 636509, and 636819) of different lengths and diameters were tested using the developed technique. The data show that 636843, the MWCNT with the largest outer diameter (o.d.), the widest wall thickness, and shortest length, had the best limit of detection (0.5-1 µg/mL) We also found that there was no significant difference in enrichment efficiency of VLCFAs between the four MWCNTs, which suggests that the size of the MWCNT may contribute to desorption/ionization efficiency. To our knowledge, this is the first study to test the enrichment of VLCFAs using MWCNTs of different sizes. We have shown that the VLCFAs adsorbed by MWCNTs can be analyzed by SALDI-TOFMS. In addition, this method does not require liquid/gas chromatography separation, thereby allowing for high-throughput screening of VLCFAs in peroxisomal disorders. Carbon nanotubes (CNTs) are basically elongated fullerenes consisting of rolled graphite sheets with diameters in the nanom- * To whom correspondence should be addressed. (C.-C.L.) Phone: (886) 4-22840485ext. 235. Fax: (886) 4-22858163. E-Mail: lailai@dragon.nchu.edu.tw. (F.-J.T.) Phone: (886) 4-22062121ext. 7076. Fax: (886) 4-22033295. E-Mail: d0704@mail.cmuh.org.tw. † China Medical University Hospital. ‡ National Chung Hsing University. § National Taiwan University Hospital and National Taiwan University College of Medicine. | China Medical University. & Asia University. 6814 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 eter range and lengths in the micrometer range. CNTs were first discovered in the cathode deposit of arc discharge between graphite rods. 1 CNTs are classified based on the number of carbon atom layers into multiwalled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). 2 CNTs have unique chemical, physical, mechanical, and electrical properties, and therefore, they have potential applications in a variety of fields. 3,4 The hydrophobic features and large adsorption surface areas of CNTs make them effective solid-phase extraction adsorbents of a wide range of chemical compounds including endocrine disruptors, 5 chlorophenols, 6 polycyclic aromatic hydrocarbons, 7 benzodiazepine residues, 8 barbiturates, 9 herbicides, 10 tetracyclines, 11 and polybrominated diphenyl ethers. 12 It has been shown that functional groups (i.e., hydroxyl or carboxyl groups) introduced onto the surface of CNTs can modulate their affinity for and selectivity of hydrophilic solutes or compounds with polar functional groups. 13 From a structural point of view, buckminster fullerene (C60) has also been shown to be an effective solid-phase extraction adsorbent. Munoz and Valcarcel showed that MWCNTs as well as C60 and C70 fullerenes were superior to graphitized (1) Iijima, S. Nature 1991, 354, 56–58. (2) Iijima, S.; Ichihashi, T. Nature 1993, 363, 603–605. (3) Saito, N.; Usui, Y.; Aoki, K.; Narita, N.; Shimizu, M.; Hara, K.; Ogiwara, N.; Nakamura, K.; Ishigaki, N.; Kato, H.; Taruta, S.; Endo, M. Chem. Soc. Rev. 2009, 38, 1897–1903. (4) Valcarcel, M.; Cardenas, S.; Simonet, B. M. Anal. Chem. 2007, 79, 4788– 4797. (5) Cai, Y.; Jiang, G.; Liu, J.; Zhou, Q. Anal. Chem. 2003, 75, 2517–2521. (6) Cai, Y. Q.; Cai, Y. E.; Mou, S. F.; Lu, Y. Q. J. Chromatogr., A 2005, 1081, 245–247. (7) Wang, W. D.; Huang, Y. M.; Shu, W. Q.; Cao, J. J. Chromatogr., A 2007, 1173, 27–36. (8) Wang, L.; Zhao, H.; Qiu, Y.; Zhou, Z. J. Chromatogr., A 2006, 1136, 99– 105. (9) Zhao, H.; Wang, L.; Qiu, Y.; Zhou, Z.; Zhong, W.; Li, X. Anal. Chim. Acta 2007, 586, 399–406. (10) Zhou, Q.; Xiao, J.; Wang, W.; Liu, G.; Shi, Q.; Wang, J. Talanta 2006, 68, 1309–1315. (11) Suarez, B.; Santos, B.; Simonet, B. M.; Cardenas, S.; Valcarcel, M. J. Chromatogr., A 2007, 1175, 127–132. (12) Wang, J. X.; Jiang, D. Q.; Gu, Z. Y.; Yan, X. P. J. Chromatogr., A 2006, 1137, 8–14. (13) Sae-Khow, O.; Mitra, S. J. Chromatogr., A 2009, 1216, 2270–2274. 10.1021/ac100772j © 2010 American Chemical Society Published on Web 07/22/2010
carbon black and RP-C18 for the extraction of the organometallic compounds. 14 Surface-assisted laser desorption/ionization (SALDI), a matrixfree method for laser desorption/ionization mass spectrometry, 15 has overcome the limitations of matrix-assisted laser desorption/ ionization (MALDI). The lower matrix interference in the low mass spectrum (molecular mass < 500 Da) makes SALDI more appropriate for quantifying small molecules. There are four major types of SALDI substrates: silicon (DIOS), 16,17 sol-gels, 18 carbonbased substrates, and metal particle-based substrates. 19-22 Carbonbased SALDI, which utilizes graphite with sizes in the micrometer range, was first used as a desorption/ionization substrate for detection of peptides and proteins in 1995. 20 CNTs have also been used as SALDI substrates to analyze small peptides (
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Anal. Chem. 2010, 82, 6745-6750 Let
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purchased from Invitrogen-Molecular
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Figure 3. Electropherograms of TPP-
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Anal. Chem. 2010, 82, 6751-6755 Res
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(pH 8.0) with cysteine and cystamin
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Figure 4. Ion mobility mass spectra
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GOx glucose + O298 gluconic acid +
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coater at 2000 rpm for 20 s, and th
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Figure 5. Comparison of cyclic volt
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Page 75 and 76: Table 2. Concentrations and Ratios
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Page 105 and 106: Figure 1. 226 Ra spectrum by liquid
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Figure 1. Schematic illustration of
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Table 1. Absolute Quantification Re
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ment. Therefore, the long-time drea
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Figure 1. Chemically actuated micro
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Figure 2. Influence of a surfactant
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Figure 5. Device to eject and mix s
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Anal. Chem. 2010, 82, 6877-6886 Imm
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NaCl, phosphate buffer saline (PBS)
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Figure 2. Product ion mass spectra
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-70 °C resolved the problem, givin
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Table 1. Intraday Precision and Acc
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Anal. Chem. 2010, 82, 6887-6894 Fer
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Figure 1. Infrared spectra of (A) u
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Figure 3. Cyclic voltammograms obta
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Figure 6. Calculated charge from ch
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Anal. Chem. 2010, 82, 6895-6903 Ele
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Table 1. Chemical Structure, pKa Va
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pH with a tilted baseline (Figure 1
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Table 2. Linearity and Detection Li
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ascorbic acid (AA), uric acid (UA),
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the multielement capabilities, the
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RESULTS AND DISCUSSION Sulfur Detec
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Table 2. Molecular Properties and C
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Anal. Chem. 2010, 82, 6911-6918 Dir
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dilution and hybridization buffer.
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solution under appropriate incubati
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Figure 4. Standardization curve for
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Anal. Chem. 2010, 82, 6919-6925 Ele
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the ×10 objective, to have a large
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Figure 2. With a suitable removal o
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the NB signal in a much better foot
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Scheme 1. Reactions of Selenium Rea
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Figure 2. (a) ESI-MS spectrum showi
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Figure 4. (a) ESI-MS spectrum showi
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Anal. Chem. 2010, 82, 6933-6939 Dif
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trode 28 by a finite element using
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Figure 4. Comparison between simula
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Figure 6. Comparison between simula
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educed in the vicinity of double bo
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Figure 2. Normalized product ion ab
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Figure 4. EID (a) and IRMPD (b) of
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Anal. Chem. 2010, 82, 6947-6957 Ide
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Figure 1. Schematic flowchart showi
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difference, ppm compound Table 1. I
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isoforms, its successful use, in th
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Figure 5. Extracted ion current ESI
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m/z 1172.935 was observed for Ser14
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linked products via affinity tags.
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Scheme 2. Fragmentation Mechanism o
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Figure 1. (A) ESI-LTQ-CID-MS 2 prod
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Figure 3. (A) ESI-LTQ-CID-MS 2 prod
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Figure 5. (A) MALDI-TOF/TOF product
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Anal. Chem. 2010, 82, 6969-6975 Ana
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Figure 3. Equilibrium response as a
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Figure 6. The average measured resp
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for the fill time, and we find that
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nucleotide tails. 3-5 Thus, the amo
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allow the use of higher aptamer con
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quent ligation of the aptamers afte
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Anal. Chem. 2010, 82, 6983-6990 Imp
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Figure 2. Configuration editor wind
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Figure 4. Dependencies between volu
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Since the time for liquid expulsion
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Anal. Chem. 2010, 82, 6991-6999 Int
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Figure 1. Representation of the Car
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Table 2. Capillary Electrophoresis
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Figure 4. (A) Typical raw electroph
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field. DNA profiles were delivered
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Another approach to handle this lim
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(principal components, PCs) in whic
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Figure 5. Relevant score plots and
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CONCLUSIONS In this paper we have i
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electroactive-species loaded liposo
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Figure 2. Qdot-based FLFTS response
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Figure 6. Fluorescence imaging of Q
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Anal. Chem. 2010, 82, 7015-7020 Sel
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Table 1. Effect of 1 D-LC Condition
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Figure 3. Peak-production rate vers
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Anal. Chem. 2010, 82, 7021-7026 Cel
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luciferase (T7 control vector) was
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Figure 3. Inhibitory effects of luc
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Anal. Chem. 2010, 82, 7027-7034 Pat
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Electrochemistry. Electrochemical m
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Figure 2. SEM images of Au substrat
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Table 3. Film Thickness Measurement
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Anal. Chem. 2010, 82, 7035-7043 Qua
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Figure 1. (A) FL spectra of BSPOTPE
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Figure 4. (A) Variation in the FL i
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Figure 6. (A) FL spectra of BSPOTPE
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Scheme 1. Proposed Mechanism for Fl
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one or more drawbacks including poo
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Figure 2. Free fluorophores do not
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Anal. Chem. 2010, 82, 7049-7052 Dev
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Figure 2. Comparative analysis of d
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