title: System-on-fluidics immunoassay device integrating wireless radio-frequency-identification sensor chips.
abstract: A simple and sensitive point-of-care-test (POCT) device for chemiluminescence (CL) immunoassay was devised and tested. The device consists of a plastic flow-channel reactor and two wireless-communication sensor chips, namely, a photo-sensor chip and a temperature-sensor chip. In the flow-channel reactor, a target antigen is captured by an antibody immobilized on the inner wall of the flow-channel and detected with enzyme labeled antibody by using CL substrate. The CL signal corresponding to the amount of antigen is measured by a newly developed radio-frequency-identification (RFID) sensor, which enables batteryless operation and wireless data communication with an external reader. As for the POCT device, its usage environment, especially temperature, varies for each measurement. Hence, temperature compensation is a key issue in regard to eliminating dark-signal fluctuation, which is a major factor in deterioration of the precision of the POCT device. A two-stage temperature-compensation scheme was adopted. As for the first stage, the signals of two photodiodes, one with an open window and one with a sealed window, integrated on the photo-sensor chip are differentiated to delete the dark signal. As for the second stage, the differentiated signal fluctuation caused by a temperature variation is compensated by using the other sensor chip (equipped with a temperature sensor). The dark-level fluctuation caused by temperature was reduced from 0.24 to 0.02 pA/°C. The POCT device was evaluated as a CL immunoassay of thyroid-stimulating hormone (TSH). The flow rate of the CL reagent in the flow channel was optimized. As a result, the detection limit of the POCT device was 0.08 ng/ml (i.e., 0.4 μIU/ml).
authors.affiliation: Hitachi, Ltd., Central Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601, Japan. Electronic address: yoshiaki.yazawa.yw@hitachi.com.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Yazawa
authors.affiliation: Hitachi, Ltd., Central Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Oonishi
authors.affiliation: Hitachi, Ltd., Central Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Hitachi, Ltd., Central Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Shiratori
authors.affiliation: Sumitomo Bakelite Co., Ltd., S-BIO Business Division, 1-1-5 Murotani, Nishi-ku, Kobe, Hyogo 651-2241, Japan.
authors.forename: Sohei
authors.initials: S
authors.lastname: Funaoka
authors.affiliation: Sumitomo Bakelite Co., Ltd., S-BIO Business Division, 1-1-5 Murotani, Nishi-ku, Kobe, Hyogo 651-2241, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D055910:Antibodies, Immobilized / Q000737:chemistry*; D000941:Antigens / Q000032:analysis*; D006801:Humans; D007118:Immunoassay; D057230:Limit of Detection; D008163:Luminescent Measurements / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D019095:Point-of-Care Systems; D057233:Radio Frequency Identification Device; D059629:Signal-To-Noise Ratio; D013696:Temperature; D013972:Thyrotropin / Q000737:chemistry
chemical_list: D055910:Antibodies, Immobilized; D000941:Antigens; D013972:Thyrotropin
keywords: Flow-channel reactor; Immunoassay; Point of care testing; Radio frequency identification; Temperature compensation