Analytical Chemistry Chemical Cytometry Quantitates Superoxide
Analytical Chemistry Chemical Cytometry Quantitates Superoxide
Analytical Chemistry Chemical Cytometry Quantitates Superoxide
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Anal. Chem. 2010, 82, 6814–6820<br />
Screening Assay of Very Long Chain Fatty Acids in<br />
Human Plasma with Multiwalled Carbon<br />
Nanotube-Based Surface-Assisted Laser<br />
Desorption/Ionization Mass Spectrometry<br />
Wei-Yi Hsu, † Wei-De Lin, †,‡ Wuh-Liang Hwu, § Chien-Chen Lai,* ,‡,| and Fuu-Jen Tsai* ,†,|,&<br />
Department of Medical Research, China Medical University Hospital, Taichung, Taiwan, Institute of Molecular Biology,<br />
National Chung Hsing University, Taichung, Taiwan, Department of Medical Genetics, National Taiwan University<br />
Hospital and National Taiwan University College of Medicine, Taipei, Taiwan, Graduate Institute of Chinese Medical<br />
Science, China Medical University, Taichung, Taiwan, and Department of Health and Nutrition Biotechnology, Asia<br />
University, Taichung, Taiwan<br />
Peroxisomal disorders are characterized biochemically by<br />
elevated levels of very long chain fatty acids (VLCFAs) in<br />
serum. Herein, we describe a novel approach for quantification<br />
of VLCFAs in serum, namely, eicosanoic acid<br />
(C20:0), docosanoic acid (C22:0), tetracosanoic acid<br />
(C24:0), and hexacosanoic acid (C26:0). The methodology<br />
is based on (i) enrichment of VLCFA derivatives using<br />
multiwalled carbon nanotubes (MWCNTs); (ii) quantification<br />
using stable isotope-labeled internal standards; and<br />
(iii) direct detection using MWCNT-based surface-assisted<br />
laser desorption/ionization-time-of-flight mass spectrometry<br />
(SALDI-TOFMS). Four kinds of MWCNTs (Aldrich<br />
636843, 636495, 636509, and 636819) of different<br />
lengths and diameters were tested using the developed<br />
technique. The data show that 636843, the MWCNT with<br />
the largest outer diameter (o.d.), the widest wall thickness,<br />
and shortest length, had the best limit of detection<br />
(0.5-1 µg/mL) We also found that there was no significant<br />
difference in enrichment efficiency of VLCFAs between<br />
the four MWCNTs, which suggests that the size of<br />
the MWCNT may contribute to desorption/ionization<br />
efficiency. To our knowledge, this is the first study to test<br />
the enrichment of VLCFAs using MWCNTs of different<br />
sizes. We have shown that the VLCFAs adsorbed by<br />
MWCNTs can be analyzed by SALDI-TOFMS. In addition,<br />
this method does not require liquid/gas chromatography<br />
separation, thereby allowing for high-throughput screening<br />
of VLCFAs in peroxisomal disorders.<br />
Carbon nanotubes (CNTs) are basically elongated fullerenes<br />
consisting of rolled graphite sheets with diameters in the nanom-<br />
* To whom correspondence should be addressed. (C.-C.L.) Phone: (886)<br />
4-22840485ext. 235. Fax: (886) 4-22858163. E-Mail: lailai@dragon.nchu.edu.tw.<br />
(F.-J.T.) Phone: (886) 4-22062121ext. 7076. Fax: (886) 4-22033295. E-Mail:<br />
d0704@mail.cmuh.org.tw.<br />
† China Medical University Hospital.<br />
‡ National Chung Hsing University.<br />
§ National Taiwan University Hospital and National Taiwan University College<br />
of Medicine.<br />
| China Medical University.<br />
& Asia University.<br />
6814 <strong>Analytical</strong> <strong>Chemistry</strong>, Vol. 82, No. 16, August 15, 2010<br />
eter range and lengths in the micrometer range. CNTs were first<br />
discovered in the cathode deposit of arc discharge between<br />
graphite rods. 1 CNTs are classified based on the number of carbon<br />
atom layers into multiwalled carbon nanotubes (MWCNTs) and<br />
single-walled carbon nanotubes (SWCNTs). 2 CNTs have unique<br />
chemical, physical, mechanical, and electrical properties, and<br />
therefore, they have potential applications in a variety of fields. 3,4<br />
The hydrophobic features and large adsorption surface areas of<br />
CNTs make them effective solid-phase extraction adsorbents of<br />
a wide range of chemical compounds including endocrine disruptors,<br />
5 chlorophenols, 6 polycyclic aromatic hydrocarbons, 7 benzodiazepine<br />
residues, 8 barbiturates, 9 herbicides, 10 tetracyclines, 11<br />
and polybrominated diphenyl ethers. 12 It has been shown that<br />
functional groups (i.e., hydroxyl or carboxyl groups) introduced<br />
onto the surface of CNTs can modulate their affinity for and<br />
selectivity of hydrophilic solutes or compounds with polar functional<br />
groups. 13 From a structural point of view, buckminster<br />
fullerene (C60) has also been shown to be an effective solid-phase<br />
extraction adsorbent. Munoz and Valcarcel showed that MWCNTs<br />
as well as C60 and C70 fullerenes were superior to graphitized<br />
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10.1021/ac100772j © 2010 American <strong>Chemical</strong> Society<br />
Published on Web 07/22/2010