Name: integration of miniaturized solid phase extraction and lc-ms/ms detection of 3-nitrotyrosine in human urine for clinical applications
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Description: Watch this Scientific Journal Video about Integration of Miniaturized Solid Phase Extraction and LC-MS/MS Detection of 3-Nitrotyrosine in Human Urine for Clinical Applications at JoVE.com

The authors would acknowledge Scott Howard and Abigail Marinack for general support and coordination of this work.

All studies involving human urine samples were conducted adherence to the procedure approved by Pharmasan/Neuroscience Institutional Review Board (IRB).
1. Urine Sample Collection and Creatinine (Cr) Determination
<ol>
	<li>Collect 5 mL of the next morning urine samples after ca. 10 h overnight fasting in a 5 mL transport tube A containing 250 &#181;L of 3 N HCl as preservative and store at -20 &#176;C until use.</li>
	<li>Thaw and vortex 5 mL transport urine A tube and centrifuge in a centr...

<ol>
	<li>Dalle-Donne, I., Rossi, R., Colombo, R., Giustarini, D., Milzani, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomarkers+of+oxidative+damage+in+human+disease.">Biomarkers of oxidative damage in human disease.</a> Clin. Chem. 52 (4), 601-623 (2006).</li><li>Pacher, P., Beckman, J. S., Liaudet, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitric+oxide+and+peroxynitrite+in+health+and+disease.">Nitric oxide and peroxynitrite in health and disease.</a> Physiol. Rev. 87 (1), 315-424 (2007).</li><li>Baraldi, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3-Nitrotyrosine,+a+marker+of+nitrosative+stress,+is+increased+in+breath+condensate+of+allergic+asthmatic+children.">3-Nitrotyrosine, a marker of nitrosative stress, is increased in breath condensate of allergic asthmatic children.</a> Allergy. 61 (1), 90-96 (2006).</li><li>Ischiropoulos, H., Beckman, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidative+stress+and+nitration+in+neurodegeneration:+Cause,+effect,+or+association?.">Oxidative stress and nitration in neurodegeneration: Cause, effect, or association?.</a> J. Clin. Invest. 111 (2), 163-169 (2003).</li><li>Butterfield, D. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elevated+levels+of+3-nitrotyrosine+in+brain+from+subjects+with+amnestic+mild+cognitive+impairment:+implications+for+the+role+of+nitration+in+the+progression+of+Alzheimer's+disease.">Elevated levels of 3-nitrotyrosine in brain from subjects with amnestic mild cognitive impairment: implications for the role of nitration in the progression of Alzheimer's disease.</a> Brain Res. 1148, 243-248 (2007).</li><li>Hui, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+and+robust+LC-MS/MS+method+for+quantification+of+free+3-nitrotyrosine+in+human+plasma+from+patients+receiving+on-pump+CABG+surgery.">A simple and robust LC-MS/MS method for quantification of free 3-nitrotyrosine in human plasma from patients receiving on-pump CABG surgery.</a> Electrophoresis. 33 (4), 697-704 (2012).</li><li>Kato, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+modified+tyrosines+in+healthy+and+diabetic+human+urine+using+liquid+chromatography/tandem+mass+spectrometry.">Quantification of modified tyrosines in healthy and diabetic human urine using liquid chromatography/tandem mass spectrometry.</a> J. Clin. Biochem. Nutr. 44 (1), 67-78 (2009).</li><li>Duncan, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+approaches+to+the+analysis+of+3-nitrotyrosine.">A review of approaches to the analysis of 3-nitrotyrosine.</a> Amino acids. 25 (3-4), 351-361 (2003).</li><li>Ryberg, H., Caidahl, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatographic+and+mass+spectrometric+methods+for+quantitative+determination+of+3-nitrotyrosine+in+biological+samples+and+their+application+to+human+samples.">Chromatographic and mass spectrometric methods for quantitative determination of 3-nitrotyrosine in biological samples and their application to human samples.</a> J. Chromatogr. B. 851 (1-2), 160-171 (2007).</li><li>Tsikas, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analytical+methods+for+3-nitrotyrosine+quantification+in+biological+samples:+the+unique+role+of+tandem+mass+spectrometry.">Analytical methods for 3-nitrotyrosine quantification in biological samples: the unique role of tandem mass spectrometry.</a> Amino acids. 42 (1), 45-63 (2012).</li><li>Tsikas, D., Duncan, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry+and+3-nitrotyrosine:+strategies,+controversies,+and+our+current+perspective.">Mass spectrometry and 3-nitrotyrosine: strategies, controversies, and our current perspective.</a> Mass Spectrom. Rev. 33 (4), 237-276 (2014).</li><li>Iwasaki, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+fluorescence+reagents+for+simultaneous+determination+of+hydroxylated+phenylalanine+and+nitrated+tyrosine+by+high-performance+liquid+chromatography+with+fluorescence+detection.">Comparison of fluorescence reagents for simultaneous determination of hydroxylated phenylalanine and nitrated tyrosine by high-performance liquid chromatography with fluorescence detection.</a> Biomed. Chromatogr. 26 (1), 41-50 (2012).</li><li>Saravanabhavan, G., Blais, E., Vincent, R., Kumarathasan, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high+performance+liquid+chromatography-electrochemical+array+method+for+the+measurement+of+oxidative/nitrative+changes+in+human+urine.">A high performance liquid chromatography-electrochemical array method for the measurement of oxidative/nitrative changes in human urine.</a> J. Chromatogr. A. 1217 (19), 3269-3274 (2010).</li><li>Mergola, L., Scorrano, S., Del Sole, ., Lazzoi, R., R, M., Vasapollo, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developments+in+the+synthesis+of+a+water+compatible+molecularly+imprinted+polymer+as+artificial+receptor+for+detection+of+3-nitro-L-tyrosine+in+neurological+diseases.">Developments in the synthesis of a water compatible molecularly imprinted polymer as artificial receptor for detection of 3-nitro-L-tyrosine in neurological diseases.</a> Biosens. Bioelectron. 40 (1), 336-341 (2013).</li><li>Schwedhelm, E., Tsikas, D., Gutzki, F. M., Frolich, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas+chromatographic-tandem+mass+spectrometric+quantification+of+free+3-nitrotyrosine+in+human+plasma+at+the+basal+state.">Gas chromatographic-tandem mass spectrometric quantification of free 3-nitrotyrosine in human plasma at the basal state.</a> Anal. Biochem. 276 (2), 195-203 (1999).</li><li>Tsikas, D., Mitschke, A., Suchy, M. T., Gutzki, F. M., Stichtenoth, D. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+3-nitrotyrosine+in+human+urine+at+the+basal+state+by+gas+chromatography-tandem+mass+spectrometry+and+evaluation+of+the+excretion+after+oral+intake.">Determination of 3-nitrotyrosine in human urine at the basal state by gas chromatography-tandem mass spectrometry and evaluation of the excretion after oral intake.</a> J. Chromatogr. B. 827 (1), 146-156 (2005).</li><li>Marvin, L. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+o,o'-dityrosine,+o-nitrotyrosine,+and+o-tyrosine+in+cat+urine+samples+by+LC/electrospray+ionization-MS/MS+using+isotope+dilution.">Quantification of o,o'-dityrosine, o-nitrotyrosine, and o-tyrosine in cat urine samples by LC/electrospray ionization-MS/MS using isotope dilution.</a> Anal. Chem. 75 (2), 261-267 (2003).</li><li>Orhan, H., Vermeulen, N. P., Tump, C., Zappey, H., Meerman, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+determination+of+tyrosine,+phenylalanine+and+deoxyguanosine+oxidation+products+by+liquid+chromatography-tandem+mass+spectrometry+as+non-invasive+biomarkers+for+oxidative+damage.">Simultaneous determination of tyrosine, phenylalanine and deoxyguanosine oxidation products by liquid chromatography-tandem mass spectrometry as non-invasive biomarkers for oxidative damage.</a> J. Chromatogr. B. 799 (2), 245-254 (2004).</li><li>Chen, H. J. C., Chiu, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+detection+and+quantification+of+3-nitrotyrosine+and+3-bromotyrosine+in+human+urine+by+stable+isotope+dilution+liquid+chromatography+tandem+mass+spectrometry.">Simultaneous detection and quantification of 3-nitrotyrosine and 3-bromotyrosine in human urine by stable isotope dilution liquid chromatography tandem mass spectrometry.</a> Toxicol. Lett. 181 (1), 31-39 (2008).</li><li>Marc, D. T., Ailts, J. W., Campeau, D. C. A., Bull, M. J., Olson, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurotransmitters+excreted+in+the+urine+as+biomarkers+of+nervous+system+activity:+validity+and+clinical+applicability.">Neurotransmitters excreted in the urine as biomarkers of nervous system activity: validity and clinical applicability.</a> Neurosci. Biobehav. Rev. 35 (3), 635-644 (2011).</li><li>Li, X. G., Li, S., Wynveen, P., Mork, K., Kellermann, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+validation+of+a+specific+and+sensitive+LC-MS/MS+method+for+quantification+of+urinary+catecholamines+and+application+in+biological+variation+studies.">Development and validation of a specific and sensitive LC-MS/MS method for quantification of urinary catecholamines and application in biological variation studies.</a> Anal. Bioanal. Chem. 406 (28), 7287-7297 (2014).</li><li>Li, X. G., Li, S., Kellermann, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pre-analytical+and+analytical+validations+and+clinical+applications+of+a+miniaturized,+simple+and+cost-effective+solid+phase+extraction+combined+with+LC-MS/MS+for+the+simultaneous+determination+of+catecholamines+and+metanephrines+in+spot+urine+samples.">Pre-analytical and analytical validations and clinical applications of a miniaturized, simple and cost-effective solid phase extraction combined with LC-MS/MS for the simultaneous determination of catecholamines and metanephrines in spot urine samples.</a> Talanta. 159, 238-247 (2016).</li><li>Chao, M. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+detection+of+3-nitrotyrosine+and+3-nitro-4-hydroxyphenylacetic+acid+in+human+urine+by+online+SPE+LC-MS/MS+and+their+association+with+oxidative+and+methylated+DNA+lesions.">Simultaneous detection of 3-nitrotyrosine and 3-nitro-4-hydroxyphenylacetic acid in human urine by online SPE LC-MS/MS and their association with oxidative and methylated DNA lesions.</a> Chem. Res. Toxicol. 28 (5), 997-1006 (2015).</li><li>Radabaugh, M. R., Nemirovskiy, O. V., Misko, T. P., Aggarwal, P., Mathews, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunoaffinity+liquid+chromatography-tandem+mass+spectrometry+detection+of+nitrotyrosine+in+biological+fluids+development+of+a+clinically+translatable+biomarker.">Immunoaffinity liquid chromatography-tandem mass spectrometry detection of nitrotyrosine in biological fluids development of a clinically translatable biomarker.</a> Anal. Biochem. 380 (1), 68-76 (2008).</li><li>Li, X. G., Li, S., Kellermann, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tailored+96-well+&#181;Elution+solid-phase+extraction+combined+with+UFLC-MS/MS:+a+significantly+improved+approach+for+determination+of+free+3-nitrotyrosine+in+human+urine.">Tailored 96-well &#181;Elution solid-phase extraction combined with UFLC-MS/MS: a significantly improved approach for determination of free 3-nitrotyrosine in human urine.</a> Anal. Bioanal. Chem. 407 (25), 7703-7712 (2015).</li><li>. Roche Creatinine Jaffé Gen.2, package insert 2011-11, V7 Available from: <a target="_blank" href="https://usdiagnostics.roche.com/products/06407137190/PARAM2083/overlay.html">https://usdiagnostics.roche.com/products/06407137190/PARAM2083/overlay.html</a> (2011)</li><li>Li, X. G., Li, S., Kellermann, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+mixed-mode+solid+phase+extraction+coupled+with+LC-MS/MS+for+the+re-evaluation+of+free+3-nitrotyrosine+in+human+plasma+as+an+oxidative+stress+biomarker.">A novel mixed-mode solid phase extraction coupled with LC-MS/MS for the re-evaluation of free 3-nitrotyrosine in human plasma as an oxidative stress biomarker.</a> Talanta. 140, 45-51 (2015).</li><li>Li, X. 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Substantial variations in concentrations previously reported in the literature for the endogenous free 3-NT in human urine samples reveal methodological problems associated with available assays8,9,10,11. Accurate determination of the low basal level of 3-NT in human urine remains a challenging task that requires special precautions for sample preparation and LC-MS/MS analysis. This protocol ou...

The effects of oxidative stress on clinical presentation have been thrust into the forefront in recent years1. One of the biomarkers being explored is 3-nitrotyrosine (3-NT), an end stable product formed when reactive nitrogen species (RNS) interact with tyrosine, a catecholamine neurotransmitter precursor. While 3-NT may have clinical value as a biomarker for RNS in vivo, the substantial changes of the properties and functions of tyrosine may adversely affect corresponding proteins and cellular functions1,2. Emerging research has suggested that 3-NT may play an important role in inflammatory conditions3, neurodegenerative disorders4,5, cardiovascular disease6 and diabetes7 as well as conditions related to oxidative stress. However, these observations are based on results from methodologies lacking in sensitivity and/or selectivity8,9,10,11. The enormous 3-NT concentration ranges for the biological samples previously reported in the literature reveal that serious analytical problems are associated with these assays and technical improvement is needed to accurately quantify the levels of 3-NT and verify its role in the pathology of these conditions.
The quantitation of free 3-NT in biological matrices presents a special challenge to man and instrument8,9,10,11. First, the trace level of endogenous 3-NT demands an ultra-sensitive detection; second, the existence of numerous structurally similar analogues, especially tyrosine, which is present in vast excess, requires a high degree of selectivity; third, the artefactual formation of 3-NT by tyrosine nitration with ubiquitous nitrate and nitrite requires special consideration during sample preparation to avoid false overestimation of 3-NT.
Among a wide variety of methodologies employed to measure 3-NT, MS/MS has been considered the gold standard method due to its superior sensitivity and selectivity11,12,13,14. Gas chromatography (GC) coupled MS/MS offers the best sensitivity, however, the indispensable sample derivatization steps are too tedious and time-consuming to be efficient for clinical utility15,16. LC-MS/MS does not require complex sample derivatization, making it the more promising option. Nonetheless, there are several obstacles to overcome such as the sensitivity of LC-MS/MS methods reported in the literature needs to improve for the measurement of low abundant 3-NT7,17,18 and the relatively long turnaround time must be shortened for high-throughput applications12,13,17,19.
Additionally, when considering clinical applications, the biological matrix used plays a significant role. It should be easy and inexpensive to obtain and non-invasive if possible20,21,22. Plasma, the traditionally used sample in the literature, is not a clinically desirable matrix, so a methodology utilizing urine which is non-invasive and cost-effective, was sought.
Several attempts to develop reliable and specific LC-MS/MS methodologies have been made using urine9,10,11. However, they have all fallen short of being either selective, reliable or efficient enough for clinical use. The effectiveness of the predominant SPE using traditional reversed-phase cartridge (C18 type) as sample cleanup for the 3-NT analysis has been questioned and a sequential SPE of strong cation exchange (SCX) and reversed phase C18-OH has been proposed6,7,19. One recently developed LC-MS/MS method utilized a multi-step purification process of manual C18 SPE, preparative high pressure liquid chromatography (HPLC), and online SPE for analysis of 3-NT23. Although this method was sensitive enough for clinical purposes, with an LLOQ of 0.041 nM, the cleanup process was intensive and tedious and required 3 mL of urine, limiting its feasibility for high-throughput. A molecularly imprinted polymer was employed as the SPE sorbent to improve the efficiency of the cleanup process14, but the resulting LLOQ (0.7 &#181;g/mL) was not low enough for clinical specimens. Another method required two-dimensional (2D) LC-MS/MS and immunoaffinity chromatography for sample cleanup in order to achieve a limit of detection (LOD) of 0.022 nM24. While all these methods have made advancements in the assessment of 3-NT, none have achieved the sensitivity, reliability, and efficiency necessary for clinical applications.
In order to investigate the pathology of free 3-NT and its role as a biomarker of oxidative stress in clinical settings, we have developed a methodology that is simple, efficient, accurate and precise, enabling for high-throughput clinical applications25. A miniaturized mixed-mode cation exchange (MCX) 96-well extraction microplate was implemented to achieve simple and effective sample cleanup and enrichment of 3-NT in a single extraction bypassing the drawbacks seen in the existing methods that require derivatization, evaporation and 2D-LC. Liquid chromatography with 0.01% HCOOH as an additive in mobile phase offered an enhanced signal response with a rapid cycle time. Selectivity was further improved through application of a mild NH4OAc elution solution for selective elution of 3-NT, and use of MRM transition for both 3-NT and the internal standard (IS). The matrix effect was compensated for by using a reduced amount of a preferred 13C-labeled isotopic IS for quantification. With the advent of this methodology, researchers and clinicians will be able to verify the role of 3-NT in clinical conditions and further explore the impact of oxidative stress.

<table border="0" cellpadding="0" cellspacing="0" width="912">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:375px;">3-Nitro-L-tyrosine</td>
			<td style="width:161px;">Sigma</td>
			<td style="width:115px;">N7389-5g</td>
			<td style="width:263px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">3-Nitro-L-tyrosine-13C9</td>
			<td>Sigma</td>
			<td>652296-5.0mg</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mass Spec Gold Urine</td>
			<td>Golden West Biologicals</td>
			<td>MSG 5000-1L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Oasis MCX 96-well &#181;Elution plate</td>
			<td style="width:161px;">Waters</td>
			<td>186001830BA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2mL 96 well collection plate</td>
			<td style="width:161px;">Phenomenex&#160;&#160;</td>
			<td style="width:115px;">AH0-7194</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">96 positive processor</td>
			<td style="width:161px;">Waters&#160;</td>
			<td style="width:115px;">186005521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LC-MS Ultra CHROMASOLV methanol&#160;&#160;</td>
			<td style="width:161px;">Sigma</td>
			<td style="width:115px;">14262-2L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LC-MS Ultra CHROMASOLV water</td>
			<td style="width:161px;">Sigma</td>
			<td style="width:115px;">14263-2L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Formic acid for mass spectrometry</td>
			<td style="width:161px;">Sigma</td>
			<td>94318-50ML-F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium hydroxide solution</td>
			<td style="width:161px;">Sigma</td>
			<td style="width:115px;">338818-1L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultra PFP propyl columns</td>
			<td style="width:161px;">Restek</td>
			<td style="width:115px;">9179362</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5500 Triple quad</td>
			<td style="width:161px;">AB Sciex&#160;</td>
			<td style="width:115px;">/</td>
			<td style="width:263px;">Contact manufacture for more detail</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">UFLC-XR</td>
			<td style="width:161px;">Shimadzu&#160;</td>
			<td style="width:115px;">/</td>
			<td style="width:263px;">Contact manufacture for more detail</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Integra 400 Plus&#160;</td>
			<td style="width:161px;">Roche</td>
			<td style="width:115px;">/</td>
			<td style="width:263px;">Urinary Creatinine Jaff&#233; Gen 2 method</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LCMS certified 12 x 32mm screw neck vial</td>
			<td style="width:161px;">Waters</td>
			<td>600000751CV</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LCGC certified 12 x 32mm screw neck total recovery vial</td>
			<td style="width:161px;">Waters</td>
			<td>186000384C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5 mL transport tube</td>
			<td style="width:161px;">Phenix</td>
			<td>TT-3205</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:375px;">50 mL Centrifuge tube</td>
			<td style="width:161px;">Crystalgen&#160;</td>
			<td style="width:115px;">23-2263</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:375px;">15 mL Centrifuge tube</td>
			<td style="width:161px;">Crystalgen&#160;</td>
			<td style="width:115px;">23-2266</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">eLine electronic pipette</td>
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integration of miniaturized solid phase extraction and lc-ms/ms detection of 3-nitrotyrosine in human urine for clinical applications

Free 3-nitrotyrosine (3-NT) has been extensively used as a possible biomarker for oxidative stress. Increased levels of 3-NT have been reported in a wide variety of pathological conditions. However, existing methods lack the sufficient sensitivity and/or specificity necessary to measure the low endogenous level of 3-NT reliably and are too cumbersome for clinical applications. Hence, analytical improvement is urgently needed to accurately quantify the levels of 3-NT and verify the role of 3-NT in pathological conditions. This protocol presents the development of a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) detection combined with a miniaturized solid phase extraction (SPE) for the rapid and accurate measurement of 3-NT in human urine as a non-invasive biomarker for oxidative stress. SPE using a 96-well plate markedly simplified the process by combining sample cleanup and analyte enrichment without tedious derivatization and evaporation steps, reducing solvent consumption, waste disposal, risk of contamination and overall processing time. The employment of 25 mM ammonium acetate (NH4OAc) at pH 9 as the SPE elution solution substantially enhanced the selectivity. Mass spectrometry signal response was improved through adjustment of the multiple reaction monitoring (MRM) transitions. Use of 0.01% HCOOH as additive on a pentafluorophenyl (PFP) column (150 mm x 2.1 mm, 3 &#181;m) improved signal response another 2.5-fold and shortened the overall run time to 7 min. A lower limit of quantitation (LLOQ) of 10 pg/mL (0.044 nM) was achieved, representing a significant sensitivity improvement over the reported assays. This simplified, rapid, selective and sensitive method allows two plates of urine samples (n = 192) to be processed in a 24 h time-period. Considering the markedly improved analytical performance, and non-invasive and inexpensive urine sampling, the proposed assay is beneficial for pre-clinical and clinical studies.

Figure 1 illustrates that 3-NT is completely chromatographically separated from other structurally similar tyrosine analogues under the optimized LC condition, which eliminates the co-eluting interferences due to these vastly excessive compounds and consequently enhances the degree of assay selectivity. In addition, the gradient elution with 0.01% HCOOH as additive in MA and methanol at a flow rate of 0.45 mL/min allows rapid elution of 3-NT (i.e., 3...

Watch this Scientific Journal Video about Integration of Miniaturized Solid Phase Extraction and LC-MS/MS Detection of 3-Nitrotyrosine in Human Urine for Clinical Applications at JoVE.com

Integration of Miniaturized Solid Phase Extraction and LC-MS/MS Detection of 3-Nitrotyrosine in Human Urine for Clinical Applications

A selective and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method coupled with an efficient solid phase extraction on a mixed-mode cation-exchange (MCX) 96-well microplate was developed for the measurement of free 3-nitrotyrosine (3-NT) in human urine with high throughput, which is suitable for clinical applications.

Free 3-nitrotyrosine (3-NT) has been extensively used as a possible biomarker for oxidative stress. Increased levels of 3-NT have been reported in a wide ...

The overall goal of this miniaturized solid phase extraction combined with LC-MS/MS assay is to accurately quantify free 3-nitrotyrosine in human urine for clinical applications. Free 3-nitrotyrosine help in yields and a biomarker for oxidative stress. However, it will remain a special challenge to accurately quantify 3-nitrotyrosine in biological emergencies for clinical applications due to insufficient sensitivity, selectivity, and cumbersome sample preparations.This technique incorporating an effective solid phase extraction in a highly sensitive LC-MS/MS interaction allows rapid, specific, and accurate determination of low levels of endogenous 3-nitrotyrosine in human urine without the need of constitution and two-dimensional LC.Though this method can provide insight into oxidative stress investigation, it can also be applied to other pathological conditions such as complex inflammatory and neurodegenerative disorders. The implications of this technique could be extended toward monitoring the effectiveness of antioxidant treatment because the 3-nitrotyrosine level can be reduced by antioxidants. To begin this procedure, vortex previously prepared and thawed urine samples, standards, and QC samples.After vortexing, add 250 microliters of each sample and standard to 32 wells of a clean two milliliter 96-well collection plate. Add 50 microliters of previously prepared internal standard working solution to each well except the double blank sample well. Then add 50 microliters of LC-MS grade water with 0.01%of formic acid to the double blank sample well.Following this, add 250 microliters of LC-MS grade water with 0.1%of formic acid to the wells. Then mix the solutions three times with an eight-channel pipette and cover the plate until SPE loading. Next, place a mixed mode cation exchange 96-well extraction microplate and a collection reservoir on a positive pressure processor.The solid phase extraction utilizing a mixed mode cation exchange microplate enables simultaneous sample cleanup and enrichment of 3-nitrotyrosine in a single extraction. Condition the extraction plate by flowing 200 microliters of LC-MS grade methanol through the sorbent. Turn the pressure adjusting knob on the positive pressure processor to set a low positive pressure in order to allow the mixture to flow through the sorbent slowly, adjusting the pressure if needed.Equilibrate by flowing 200 microliters of LC-MS grade water with 2%formic acid through the sorbent. Using an eight-channel pipette, carefully load the entire volume of each of the pre-mixed samples onto the preconditioned extraction plate. Set low positive pressure on the positive pressure processor to allow the mixture to flow through the sorbent slowly, adjusting the pressure as needed.Following this, wash the wells by flowing 200 microliters of LC-MS grade water with 2%formic acid through the sorbent. After washing with 200 microliters of methanol and water, set the positive pressure processor to high pressure in order to dry the wells. Once the wells are dry, replace the reservoir with a clean two milliliter 96-well collection plate.Now, apply 50 microliters of a 25 millimolar ammonium acetate solution to slowly elute the retained analyte and internal standard from the extraction plate. Then add 50 microliters of LC-MS grade water with 5%formic acid to neutralize the eluent. The application of a mild ammonium acetate solution for elution of 3-nitrotyrosine provides substantial enhanced selectivity and sensitivity.Mix the samples with an eight-channel pipette three times in preparation for liquid chromatography tandem mass spectrometry analysis. After setting up the LC-MS/MS instrument, equilibrate the 3-nitrotyrosine LC-MS/MS method for 10 minutes with the LC gradient elution. By equilibrating the method, the LC gradient will be equilibrated to the initial gradient elution.The auto sampler temperature will be set to four degrees Celsius and the oven temperature will be set to 30 degrees Celsius. Create a batch list that includes the urine samples, standards, and QC samples. Then start the batch by injecting the prepared samples.After completing all the injections, establish a standard curve with a range of 10 to 2, 500 picograms per milliliter for 3-nitrotyrosine quantitation by linear regression of the peak area ratio of 3-nitrotyrosine and internal standard versus the nominal 3-nitrotyrosine concentration. Finally, quantify all the other samples using the established standard curve and determine if the QC samples fall within the established range. LC data of human urine samples show that 3-nitrotyrosine is chromatographically separated from other structurally similar tyrosine analogs under the optimized condition which eliminates co-eluting interferences due to these vastly excessive compounds and consequently enhances the degree of assay selectivity.A 3-nitrotyrosine signal is not observed in the multiple reaction monitoring chromatogram of the double blank sample, indicating that 3-nitrotyrosine is not formed during the entire process. Representative multiple reaction monitoring chromatograms of 3-nitrotyrosine and internal standard for a healthy individual are shown here. No interfering signals were observed at the retention times of 3-nitrotyrosine and internal standard.A representative standard curve is shown here. The limit of detection defined as the lowest concentration with a signal to noise ratio greater than three was determined to be two picograms per milliliter. The lower limit of quantification was determined to be 10 picograms per milliliter and is defined as the lowest concentration within 20%of imprecision and accuracy with a signal to noise ratio of greater than 10.The fine tuned integration assay delivers significant improved specificity, sensitivity, and throughput with reduced matrix effect, sorbent usage, and waste disposal. With this simple and rapid assay, urine sample can be processed within 24 hours. Take into account the non-invasive and inexpensive urine sampling.This remarkably improved method is well suited to evaluate the role of 3-nitrotyrosine as an oxidative stress biomarker in preclinical and clinical studies.

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