A high sensitivity bead-based immunoassay with nanofluidic preconcentration for biomarker detection

In this study, we developed a rapid biomarker sensor with a high sensitivity and high selectivity by applying a bead-based immunosensing technique in a nanofluidic preconcentration device. Antibody-coated 300-nm beads and antigens were mixed and then pumped into a valve-integrated nanofluidic preconcentration device for collection and trapping. Because of size differences between the molecules and 300-nm beads, the antigen (molecule) in the mixed solution could be concentrated by up to 10,000-fold in 2 min, but the nanobeads could not be thus concentrated. After concentrated antigens and antibody-coated nanobeads were isolated, microparticle tracking velocimetry was used to measure the Brownian diffusion of the nanobeads in real time to determine the antigen concentration. Through this preconcentration experiment, we demonstrated a rapid and high-sensitivity detection of prostate-specific antigen with a detection limit of 50 pg/ml in 20 min.