Development of a polyclonal antibody based strip assay for detection of cadmium residue

A rapid immunochromatographic lateral flow test strip has been developed using a gold-conjugated polyclonal antibody (pAb) for the specific determination of Cadmium (Cd²⁺) residue in environmental water. For this purpose, the isothiocyanate method was employed to synthesize Cd²⁺ artificial antigen and New Zealand white rabbits were immunized to produce anti-Cd²⁺ pAb. Antigen and goat anti-rabbit IgG were respectively drawn on NC membrane as test line and control line. Gold-labeled antibody was added on a pad and put on one end of the membrane. The detection limit of this strip was measured to be 50 ng/mL. Except for high cross-reactivity (83%) toward Hg²⁺, no significant cross-reactivity was observed for other metal chelates tested. The results demonstrate that the developed method can be potentially used as a screening tool for the determination of Cd²⁺ residues in a large amount of samples on site.