title: Noninvasive biosensor for cathepsin L in the stratum corneum.
abstract: OBJECTIVE
  The objective is to propose an on-site testing biosensor of cathepsin L (CatL) activity in the stratum corneum, which can be used for the evaluation of skin conditions noninvasively and easily.
  
  
  METHODS
  The biosensor comprises of a disposable test strip and a desktop-sized reader (260 × 150 × 290 mm(3), 1.9 kg), incorporating a charge-coupled device image sensor (CCD) unit to measure the reflectance of the test strip. A novel immuno-chromatographic test strip was proposed for CatL analysis in the stratum corneum. In order to realize the test strip, a colloidal gold technique was selected as the molecular recognition method for the CatL. A human skin sample was collected noninvasively by adhesive tape stripping.
  
  
  RESULTS
  Based on optimal assay conditions, the sensitivity of the biosensor was evaluated. It required 10 min from a sample dropping to appear the test line on the test strip. The optical density was proportion to the CatL. Bioanalytical validation indicated that, within the biosensor's detection limit (172.2 μU/mL), its accuracy (R(2) = 0.94), and precision (CV = 15%) approach more elaborate laboratory-based analyzers. In addition, the truncated sampling-reporting cycle (<15 min) allows speedy reporting of CatL levels.
  
  
  CONCLUSIONS
  It was indicated that this noninvasive and easy-to use biosensor might be a novel tool for the semi-quantitative analysis of CatL in the stratum corneum.
authors.affiliation: Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan. masakiy@iwate-u.ac.jp
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Akira
authors.initials: A
authors.lastname: Date
authors.forename: Makoto
authors.initials: M
authors.lastname: Sasaki
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Makino
authors.forename: Tadamichi
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D056668:Cathepsin L / Q000032:analysis*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010783:Photometry / Q000295:instrumentation*; D011934:Reagent Strips / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012867:Skin / Q000378:metabolism*; D055815:Young Adult
chemical_list: D011934:Reagent Strips; D056668:Cathepsin L