Rapid immunosensing based on dielectrophoretic manipulation of particles

A rapid immunosensing method for measuring two tumor markers, alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA), based on particle manipulation by negative dielectrophoresis (n-DEP) was developed. When microparticles modified with different antibodies were subjected to n-DEP manipulation by the application of an AC voltage, they accumulated in particular positions in poly(dimethylsiloxane) (PDMS) fluidic channels modified with corresponding antibodies within 1 min. The presence of a specific antigen, AFP or CEA, allowed the irreversible capture of microparticles via the formation of immuno-complexes. Uncaptured microparticles redispersed after the AC voltage was switched off. The fluorescent intensity from the irreversibly captured microparticles allowed us to determine the concentration of AFP and CEA in the sample. The range for both AFP and CEA assays was 0.1-100 ng/mL, which was sufficient to cover the concentration required for medical diagnoses. Our system measured the concentrations of AFP and CEA simultaneously in a single device with two channels modified for different antibodies. Since n-DEP was used for the rapid manipulation of the microparticles toward the PDMS surface, the time required for the assay was substantially short: 1 min for forcing and 5 min for redispersion of microparticles and sensing