Colorimetric multiplexed immunoassay using specific aggregation of antigenic peptide-modified luminous nanoparticles

A rapid immunoassay capable of detecting specific antibodies in one-step procedure is described. Antigenic peptides with cationic (KKKKC) or anionic (DDDDC) pentamer tail were immobilized on luminous nanospheres of 40 nm diameter (Ø) through cystamine and bifunctional linker molecules under various conditions. The numbers of each peptide anchored to a sphere were 5.0 x 10(2) and 0.8-3.8 x 10(3), respectively. A mixture of the antigenic peptides of FAK and c-Myc was immobilized to the spheres with red emission, while that of c-Myc and alpha-catenin was likewise to green spheres. Multiplexed immunoassay was easily achieved by adding the antibodies to a mixed dispersed solution of these spheres under appropriate conditions. Anti-FAK and anti-alpha-catenin antibodies formed aggregates with red and green emissions, respectively. On the other hand, the anti-c-Myc antibody formed aggregates emitting a yellow light. This system enabled us to differentiate three antibodies in one vessel from the definite differences in aggregate color.