Rapid determination of immunoglobulin a in human saliva by enzyme-linked immunosorbent assay on a micro channel chip

An enzyme-linked immunosorbent assay for the rapid determination of Immunoglobulin A (IgA) in human saliva has been developed on a microchannel chip. First, a primary antibody (anti-IgA) was adsorbed on the surface of a polydimethylsiloxane microchannel. The channel was then filled with an antigen (IgA) solution, followed by the introduction of a secondary antibody (anti-IgA HRP labeled) solution. Finally, a substrate solution (phosphate buffer containing Amplex (R) Red and hydrogen peroxide) was introduced into the microchannel, and the enzyme turnover was monitored by a fluorescent imaging system equipped with a CCD camera. The calibration curve of IgA standard solution at the enzyme-substrate reaction time of 5 minutes was linear over the range of 0 similar to 50 ng/ml with a correlation coefficient of 0.998. The former assay on a 96-well microtiter plate required 150 min for the determination of IgA, while the present assay on the microchannel chip enables the determination of IgA in less than 35 min. This method was successfully applied to the determination of IgA in human saliva. An on-line flow assay system with a microchannel chip has also been developed.