title: Novel method using hybrid markers: development of an approach for pulmonary measurement of multi-walled carbon nanotubes.
abstract: BACKGROUND
  Multi-walled carbon nanotubes (MWCNT)s are suspected to induce pulmonary and pleural cancers due to their asbestos-like configurations. Therefore, accurate measurement of inhaled nanotubes in target organs is crucial for assessing cancer risk. Conventionally, nanotubes are measured after combustion at high temperature for conversion into CO2; however, the sensitivity is poor and the method lacks versatility. We have therefore developed a novel approach using hybrid markers for nanotube analysis, featuring high sensitivity and the capacity to conduct repeated analyses. The method involves adsorption of markers to nanotubes, followed by their desorption and assessment by means of high performance liquid chromatography (HPLC).
  
  
  METHODS
  Recovery of MWCNT from rat lungs was conducted, and pulmonary MWCNT amounts were determined using rats intratracheally-exposed to MWCNT aerosol at 5 mg/m3 for 6 hours/day.
  
  
  RESULTS
  The correlation coefficient for the calibration curve of MWCNT weight and the HPLC area was 0.9991. Consequently, the lower quantitation limit yielded was 0.2 μg. The recovery was 92-98% at approximately 0.4-2.0 μg demonstrating that MWCNTs in the lung could be measured accurately and precisely.
  
  
  CONCLUSIONS
  We have developed a novel method using a hybrid marker approach for nanotube analysis, featuring very high sensitivity and the capacity to conduct repeated analyses. We further confirmed correlations between the amounts of nanotubes and markers and pulmonary nanotube measurement demonstrated that trace amounts could be detected with values closely relating to the administered dose, verifying that the method is sensitive and precise.
authors.affiliation: Japan Bioassay Research Center, Japan Industrial Safety and Health Association, 2445 Hirasawa, Hadano, Kanagawa 257-0015, Japan. m-onishi@jisha.or.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ohnishi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yajima
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kasai
authors.forename: Yumi
authors.initials: Y
authors.lastname: Umeda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Seigo
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Okuda
authors.forename: Masaaki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Tomoshi
authors.initials: T
authors.lastname: Nishizawa
authors.forename: Shoji
authors.initials: S
authors.lastname: Fukushima