PEG-based autonomous capillary system with integrated microbead array for immunoassay.

Surface-tension-driven capillary systems (CSs) enable self-powered delivery of samples and reagents for bioassays and thus are especially suitable for point-of-care applications. Current silicon and polymer based CSs require extensive work in professional cleanroom for the fabrication of either the silicon device itself or the micromold for polymer processing. In this work, we fabricated a PEG-based CS in a one-step photopolymerization process without the requirement of any cleanroom work. Water, buffer and serum can flow autonomously in this CS and the liquid flow rate can be tuned by modification with surfactant solution of different concentrations. We further integrated an antibody-coated microbead array into this CS for the autonomous immunoassay of two tumor markers, prostate specific antigen (PSA) and human chorionic gonadotropin (hCG), in serum samples with a total assay time of less than 10min. The detection limits for the two tumor markers were at sub-nanogram per milliliter range which is lower than their clinical threshold concentrations for cancer diagnosis. Moreover, simultaneous and multiplex detection of the two tumor markers was also achieved by using spatially encoded microbeads. This low cost and easy-fabricated CS enables fast, multiplex and autonomous immunoassay for protein markers and has the potential to be applied for point-of-care diagnostics on real clinical samples.