Rapid quantitative immunochromatographic strip for multiple proteins test

A rapid quantitative immunochromatographic strip (IS) for simultaneous detection of multiple proteins was described. Rabbit IgG (R-IgG) and human IgM (H-IgM) were used as model protein targets for demonstration of the proof of concepts. Gold nanoparticles (Au-NP) were used as tags to label the anti-R-IgG and anti-H-IgM antibodies to form two kinds of gold nanoparticle-antibody conjugates, respectively. The mixture of above conjugates was dispensed on the conjugate pad of IS. Capture antibodies of IgG and IgM were dispensed in the different locations of nitrocellulose membrane of the IS to form two test zones. The multiplex immunoassay was performed by simply applying the sample solution on the IS, waiting for several minutes, two red bands at the test zones can be easily discriminated with eyes. For quantitative test, the captured Au-NP tags on the test zones were quantified with a portable strip reader by recording the intensities of the resulting red bands at the test zones. The detection limits were estimated to be 0.5 and 2.5 ng/ml for R-IgG and H-IgM, respectively, in association with a 7-min immunoassay time.