Universal and Ultrasensitive Immunochromatographic Assay by Using an Antigen as a Bifunctional Element and Antialbumin Antibody on a Test Line

A universal and ultrasensitive immunochromatographic assay (ICA) was established using antigen as a bifunctional element and antialbumin antibody in a test line. Preincubation was introduced for competitive recognition. After optimization, the linear detection of aflatoxin M1 (AFM1) with quantum dot bead (QB)-based ICA (QB-ICA) sensor ranged from 10 to 52 pg mL–1, with a 50% inhibitory concentration (IC50) of 23 pg mL–1, which was nearly 49.6-fold lower than those of ICA on a traditional structure with traditional pretreatment (IC50 = 1.10 ng mL–1) and 10-fold lower than those of ICA on a traditional structure with acid aid pretreatment (IC50 = 0.25 ng mL–1). The limit of detection (LOD) for AFM1 was 16 pg mL–1 in milk, which was approximately 16.3-fold times higher than those of ICA on a traditional structure with traditional pretreatment and 6.3-fold higher than those of ICA on a traditional structure with acid aid pretreatment. The LOD improved by 20-fold by using the proposed structure compared to that of conventional enzyme-linked immunosorbent assay (ELISA) for AFM1-spiked milk samples (IC10 = 0.12 ng mL–1). The performance and practicability of the established QB-ICA sensor were validated with a commercial ELISA kit. To evaluate universality, we successfully detected chloramphenicol, with IC50 of 0.42 ng mL–1. Given its high sensitivity and universality, the proposed QB-ICA can be used as an alternative for rapid, sensitive, and universal quantitative detection of all small-molecule analytes.