The dual role of deposited microbead plug (DMBP): A blood filter and a conjugate reagent carrier toward point-of-care microfluidic immunoassay

To set up a point-of-care whole-blood immunoassay system, sample preparation and on-chip storage of conjugate reagents are indispensable functional units. Here, we merge these functions into a deposited microbead plug (DMBP) to simultaneously play the roles of a blood filter and a conjugate reagent carrier. The DMBP was easily fabricated by the use of natural deposition of beads without the need of weirs. Conjugate reagents (FITC labeled antibodies used here) were incorporated into the DMBP during the assembly of the DMBP. To demonstrate the ability of the DMBP, we constructed a DMBP-based microfluidic chip and used it for the detection of human IgG (hIgG). The DMBP enabled to remove blood cells from whole blood and provide the pure plasma for the downstream on-chip immunoreactions. The release of reconstituted FITC labeled antibodies from the DMBP was controlled in a passive fashion. Dry FITC labeled antibodies retained at least 81% of their activity after 60 days of storage at the room temperature. The DMBP presented here makes an important step towards the development of the self-contained, integrated, sample-to-answer microfluidic chips for point-of-care diagnostics.