Droplet-based magnetic bead immunoassay using microchannel-connected multiwell plates (mu CHAMPs) for the detection of amyloid beta oligomers

Abstract

Multiwell plates are regularly used in analytical research and clinical diagnosis but often require laborious washing steps and large sample or reagent volumes (typically, 100 mu L per well). To overcome such drawbacks in the conventional multiwell plate, we present a novel microchannel-connected multiwell plate (mu CHAMP) that can be used for automated disease biomarker detection in a small sample volume by performing droplet-based magnetic bead immunoassay inside the plate. In this mu CHAMP-based immunoassay platform, small volumes (30-50 mu L) of aqueous-phase working droplets are stably confined within each well by the simple microchannel structure (200-300 mu m in height and 0.5-1 mm in width), and magnetic beads are exclusively transported into an adjacent droplet through the oil-filled microchannels assisted by a magnet array aligned beneath and controlled by a XY-motorized stage. Using this mu CHAMP-based platform, we were able to perform parallel detection of synthetic amyloid beta (A beta) oligomers as a model analyte for the early diagnosis of Alzheimer's disease (AD). This platform easily simplified the laborious and consumptive immunoassay procedure by achieving automated parallel immunoassay (32 assays per operation in 3-well connected 96-well plate) within 1 hour and at low sample consumption (less than 10 mu L per assay) with no cumbersome manual washing step. Moreover, it could detect synthetic A beta oligomers even below 10 pg mL(-1) concentration with a calculated detection limit of similar to 3 pg mL(-1). Therefore, the mu CHAMP and droplet-based magnetic bead immunoassay, with the combination of XY-motorized magnet array, would be a useful platform in the diagnosis of human disease, including AD, which requires low consumption of the patient's body fluid sample and automation of the entire immunoassay procedure for high processing capacity.