Antigen/antibody immunocomplex from CdTe nanoparticle bioconjugates

Complementary bioconjugates based on antibody-antigen interactions were synthesized from luminescent CdTe nanoparticles (NPs). Antigen (bovine serum albumin) was conjugated to red-emitting CdTe NPs, while green-emitting NPs; were attached to the corresponding anti-BSA antibody (IgG). The NP bioconjugates were characterized by native and SDS-PAGE electrophoresis, gel-permeation HPLC, and circular dichroism. Antigen-antibody binding affinity was evaluated by enzyme-linked immunosorbent assay (ELISA). The formation of BSA-IgG immunocomplex resulted in the Forster resonance energy transfer (FRET) between the two different NPs: the luminescence of green-emitting NPs was quenched whereas the emission of the red-emitting NPs was enhanced. The luminescence recovered when the immunocomplex was exposed to an unlabeled antigen. The immunocomplexes; can be considered as a prototype of NP superstructures based on biospecific ligands, while the competitive FRET inhibition can be used in an immunoassay protocol.