Antigen/Antibody Immunocomplex from CdTe Nanoparticle Bioconjugates

TLDR

Complementary antibody–antigen bioconjugates were assembled by attaching bovine serum albumin to red‑emitting CdTe nanoparticles and anti‑BSA IgG to green‑emitting CdTe nanoparticles, then characterized by electrophoresis, HPLC, circular dichroism, and ELISA to assess binding affinity. Binding of BSA to anti‑BSA IgG produced a FRET signal: green‑emitting nanoparticles were quenched while red emission increased, and the signal was restored upon addition of free antigen, demonstrating a prototype nanoparticle superstructure that could serve as a competitive FRET‑based immunoassay.

Abstract

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 Förster 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.