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, micro-particle 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.