Fig. 1

Schematic of sandwich type immunostick test. a The model of double antibody sandwich immunostick and internal control design. Immunostick was obtained as individual tube (1). Each stick consists of four paddles (as indicated by red circle) and each paddle was designed as test, positive control, isotype-matched mAb control and uncoated negative control, as indicated (2). The test paddle was coated with mAb PL2 to capture ζ-globin chain (3). Internal positive control was coated with goat anti-mouse immunoglobulins antibody (4). Internal negative control composes of isotype-matched mAb control and uncoated negative control. The isotype-matched mAb control was coated with mouse IgG1 mAb (5). The uncoated negative control was the paddle that left as uncoated paddle (6). Biotinylated mAb PL3 was used to detect captured ζ-globin chain and HRP-conjugated streptavidin (Streptavidin-HRP) was used to monitor the antigen-antibody complexes. Finally, sticks were dipped into precipitating TMB substrate. Positive reaction (color spot) was observed with the naked eye. b For determining the presence of ζ-globin chain, the color spots were graded as no color (N): negative reactivity; light blue (LB): weakly positive reactivity; and dark blue (DB): strongly positive reactivity