A micro-extraction technique using a new digitally controlled syringe combined with UHPLC for assessment of urinary biomarkers of oxidatively damaged DNA

PLoS One. 2013;8(3):e58366. doi: 10.1371/journal.pone.0058366. Epub 2013 Mar 6.

Abstract

The formation of reactive oxygen species (ROS) within cells causes damage to biomolecules, including membrane lipids, DNA, proteins and sugars. An important type of oxidative damage is DNA base hydroxylation which leads to the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 5-hydroxymethyluracil (5-HMUra). Measurement of these biomarkers in urine is challenging, due to the low levels of the analytes and the matrix complexity. In order to simultaneously quantify 8-oxodG and 5-HMUra in human urine, a new, reliable and powerful strategy was optimised and validated. It is based on a semi-automatic microextraction by packed sorbent (MEPS) technique, using a new digitally controlled syringe (eVol(®)), to enhance the extraction efficiency of the target metabolites, followed by a fast and sensitive ultrahigh pressure liquid chromatography (UHPLC). The optimal methodological conditions involve loading of 250 µL urine sample (1:10 dilution) through a C8 sorbent in a MEPS syringe placed in the semi-automatic eVol(®) syringe followed by elution using 90 µL of 20% methanol in 0.01% formic acid solution. The obtained extract is directly analysed in the UHPLC system using a binary mobile phase composed of aqueous 0.1% formic acid and methanol in the isocratic elution mode (3.5 min total analysis time). The method was validated in terms of selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), extraction yield, accuracy, precision and matrix effect. Satisfactory results were obtained in terms of linearity (r(2) > 0.991) within the established concentration range. The LOD varied from 0.00005 to 0.04 µg mL(-1) and the LOQ from 0.00023 to 0.13 µg mL(-1). The extraction yields were between 80.1 and 82.2 %, while inter-day precision (n = 3 days) varied between 4.9 and 7.7 % and intra-day precision between 1.0 and 8.3 %. This approach presents as main advantages the ability to easily collect and store urine samples for further processing and the high sensitivity, reproducibility, and robustness of eVol(®)MEPS combined with UHPLC analysis, thus retrieving a fast and reliable assessment of oxidatively damaged DNA.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • 8-Hydroxy-2'-Deoxyguanosine
  • Adult
  • Aged
  • Analysis of Variance
  • Biomarkers / urine*
  • Chromatography, High Pressure Liquid
  • DNA Damage*
  • Deoxyguanosine / analogs & derivatives
  • Deoxyguanosine / urine
  • Female
  • Humans
  • Limit of Detection
  • Liquid Phase Microextraction / instrumentation
  • Liquid Phase Microextraction / methods*
  • Male
  • Middle Aged
  • Molecular Structure
  • Oxidative Stress*
  • Pentoxyl / analogs & derivatives
  • Pentoxyl / urine
  • Reactive Oxygen Species / metabolism
  • Syringes*
  • Tandem Mass Spectrometry

Substances

  • Biomarkers
  • Reactive Oxygen Species
  • 5-hydroxymethyluracil
  • Pentoxyl
  • 8-Hydroxy-2'-Deoxyguanosine
  • Deoxyguanosine

Grants and funding

The authors thank the financial support of FEDER (Transnational Cooperation MAC 2007–2013 Program) through VinSaudeMAC project (MAC/1/M105) and Fundação para a Ciência e a Tecnologia (FCT) through the Strategic Plan PEst-OE/QUI/UI0674/2011, and the Portuguese Mass Spectrometry Network - RNEM 2013 (REDE/1508/RNEM/2005). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.