We present a new rapid and easy-to-use immunoassay chip which we have named the immuno-pillar chip. It has hydrogel pillars, fabricated inside a microchannel, with many antibody molecules immobilized onto 1 µm diameter polystyrene beads. To evaluate the chip performance, we applied it to the sandwich assay of C-reactive protein (CRP), α-fetoprotein (AFP) and prostate-specific antigen (PSA), a cardiac and inflammation marker, tumors and prostate cancer markers, respectively. For detection of disease markers, we confirmed the chip provides rapid analysis (total assay time of about 4 min) with high sensitivity, it is easy-to-use (no special skills are needed), and it uses small volumes of the sample and reagent (0.25 µL each). Moreover, multiplex assay for three biomarkers was also possible. Additionally, the immuno-pillar chip has a big advantage of having hardly any influence on the assay results even if the introduction quantities of the sample or reagents are different.

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Staphylococcal enterotoxins (SEs) have repeatedly caused food poisoning incidents worldwide. Some of the challenges associated with food poisoning outbreaks are that traditional detection methods are expensive and require long processing times and trained technicians. Microchannel devices represent a potential detection method by which these difficulties can be overcome. In this paper, we propose that immuno-pillar devices may represent a rapid, highly sensitive, and low-cost analytical system for the simultaneous detection of staphylococcal enterotoxin types A, B, and D (SEA, SEB, and SED) in milk. To prepare milk samples simulating food contaminated with SEs, commercial milk was spiked with equal amounts of SEA, SEB, and SED. A quantitative analysis of the milk samples was performed within 15 min by using the microchannel device. The analysis required only 0.5 mL of untreated milk sample. The resultant limit of detection was 15.6 pg mL À1 for each SE, and the total assay time and sensitivity were markedly shorter and higher, respectively, than those for commercially available assay kits. The detection range of each enterotoxin using these devices was estimated as 15.6 pg mL À1 to 100 ng mL À1 , which completely covers the SE concentrations that can lead to foodborne diseases based on the U.S. Food and Drug Administration's criterion for the infectious SE dose in SE poisoning (1 mg SE). Using our devices, frequent assessment of food potentially contaminated with SE is possible.

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