Analytical Sciences

A Single-Bead Analysis on a Disk-shaped Microfluidic Device Using an Antigen-immobilized Bead

Hidenori NAGAI,* Yuka NARITA,** Miyuki OHTAKI,** Keiitsu SAITO,** and Shin-ichi WAKIDA*

*Human Stress Signal Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
**Graduate School of Human Development and Environment, Kobe University, 3-11 Tsurukabuto, Nada, Kobe 657-8501, Japan

A disk-shaped microfluidic device (lab-on-a-Disk) was developed to allow the evaluation of mental stress. As a standard sample, secretory immunoglobulin A (sIgA), which is a candidate marker of mental stress, was measured by a heterogeneous enzyme immunoassay (EIA) on the lab-on-a-Disk. Centrifugal force provided a microfluidic control on the lab-on-a-Disk. We examined the relationship between the rotational speed, the channel profile, and the position of the microfluidic chambers from the center of rotation to manipulate sample solutions into each reaction reservoir through microchannels sequentially, i.e., retain in a reservoir or flow into a subsequent reservoir. A single glass bead with immobilized sIgA on its surface was injected into a reservoir for a competitive antigen-antibody reaction, and applied to a specific surface in a heterogeneous assay. It is expected that the lab-on-a-Disk would be suitable for miniaturization and automation of the processes in EIA compared with a conventional EIA using a titer plate.

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