title: Magnetic control of an electrochemical microfluidic device with an arrayed immunosensor for simultaneous multiple immunoassays.
abstract: BACKGROUND
  Methods based on magnetic bead probes have been developed for immunoassay, but most involve complicated labeling or stripping procedures and are unsuitable for routine use.
  
  
  METHODS
  We synthesized magnet core/shell NiFe(2)O(4)/SiO(2) nanoparticles and fabricated an electrochemical magnetic controlled microfluidic device for the detection of 4 tumor markers. The immunoassay system consisted of 5 working electrodes and an Ag/AgCl reference electrode integrated on a glass substrate. Each working electrode contained a different antibody immobilized on the NiFe(2)O(4)/SiO(2) nanoparticle surface and was capable of measuring a specific tumor marker using noncompetitive electrochemical immunoassay.
  
  
  RESULTS
  Under optimal conditions, the multiplex immunoassay enabled the simultaneous detection of 4 tumor markers. The sensor detection limit was <0.5 microg/L (or <0.5 kunits/L) for most analytes. Intra- and interassay imprecisions (CVs) were <4.5% and 8.7% for analyte concentrations >5 mug/L (or >5 kunits/L), respectively. No nonspecific adsorption was observed during a series of procedures to detect target proteins, and electrochemical cross-talk (CV) between neighboring sites was <10%.
  
  
  CONCLUSIONS
  This immunoassay system offers promise for label-free, rapid, simple, cost-effective analysis of biological samples. Importantly, the chip-based immunosensor could be suitable for use in the mass production of miniaturized lab-on-a-chip devices and open new opportunities for protein diagnostics and biosecurity.
authors.affiliation: Key Laboratory of Analytical Chemistry (Chongqing), College of Chemistry and Chemical Engineering, Southwest University, Chongqing, People's Republic of China. tdping@swu.edu.cn
authors.forename: Dianping
authors.initials: D
authors.lastname: Tang
authors.forename: Ruo
authors.initials: R
authors.lastname: Yuan
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Chai
mesh_terms: D018394:CA-125 Antigen / Q000032:analysis; D002272:Carcinoembryonic Antigen / Q000032:analysis; D004563:Electrochemistry; D005296:Ferrous Compounds / Q000737:chemistry*; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D008280:Magnetics; D046210:Microfluidic Analytical Techniques; D018396:Mucin-1 / Q000032:analysis; D053758:Nanoparticles; D040081:Protein Array Analysis / Q000295:instrumentation / Q000379:methods*; D012822:Silicon Dioxide / Q000737:chemistry*; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D018394:CA-125 Antigen; D002272:Carcinoembryonic Antigen; D005296:Ferrous Compounds; D018396:Mucin-1; D000509:alpha-Fetoproteins; D012822:Silicon Dioxide