title: Determination of alpha-fetoprotein in human serum by a quartz crystal microbalance-based immunosensor.
abstract: BACKGROUND
  Increased alpha-fetoprotein (AFP) in adult plasma is considered an early indication of hepatocellular carcinoma and teratoblastoma. The aim of this study was to develop a rapid method to measure AFP in human serum by use of a direct immunosensor based on a quartz crystal microbalance (QCM).
  
  
  METHODS
  A self-assembled monolayer prepared by the cystamine method was applied to immobilize anti-AFP monoclonal antibodies on the gold surface of a quartz crystal. The frequency shifts of the QCM were measured and related to AFP concentrations. The piazoimmunosensor used no labeled reagent and no pretreatment of samples.
  
  
  RESULTS
  Ten cycles of measurements could be performed on the gold surface of the same crystal regenerated with a solution of glycine-HCl. A linear relationship existed between the frequency shifts (Hz) and the log values of AFP concentrations from 0.1 to 100 microg/L in buffer and human serum. When used for 15 days, the frequency shifts were all >95% of those on the response at the first day. The regression equation was y = 1.03x - 0.06 (S(y/x) = 3.92; r = 0.9987) for this QCM method and RIA in 29 clinical human serum samples.
  
  
  CONCLUSIONS
  The QCM sensor can measure AFP in buffer and human serum and offers advantages of high specificity, reusability, low detection limit, no label or sample pretreatment, and low sample requirement. The assay format of the immunosensor was more rapid and simpler than conventional methods.
authors.affiliation: Department of Food Health, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan, R.O.C.
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Chou
authors.forename: Win-Lin
authors.initials: WL
authors.lastname: Hsu
authors.forename: Jing-Min
authors.initials: JM
authors.lastname: Hwang
authors.forename: Chien-Yuan
authors.initials: CY
authors.lastname: Chen
mesh_terms: D000911:Antibodies, Monoclonal; D015374:Biosensing Techniques / Q000295:instrumentation; D002021:Buffers; D002138:Calibration; D004566:Electrodes; D006046:Gold; D006801:Humans; D011791:Quartz; D011863:Radioimmunoassay; D000509:alpha-Fetoproteins / Q000032:analysis* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D002021:Buffers; D000509:alpha-Fetoproteins; D011791:Quartz; D006046:Gold