Development of the microchip-based repeatable immunoassay system for clinical diagnosis

A microchip-based semi-automated heterogeneous immunoassay was developed wherein a flow injection-like system and repeatable-use gel were employed. Microfluidics used a pump with highly accurate control of flow rate, two injector valves and a microchip. The results of a system suitability test based on dye injection for microfluidics including a thermal lens microscope as a detector were good. A regeneration buffer for antigen-antibody interaction of brain natriuretic peptide (BNP) was found which did not lose binding activity of the antibody on the gels and integration of such an immunoassay scheme into a semi-automated microfluidics system would facilitate repeated-use heterogeneous immunoassay. Good reproducibility of BNP assay was obtained with the selected regeneration buffer. The concentration of BNP in the range of 0.1-100 pg mL(-1) (n = 3) was successfully determined using the system and protocol developed here.