Antibodies/antigens, gold nanoparticle

Fig. 38.2. Particle-based electrochemical immunoassay protocol. (A) Introduction of antibody-modified magnetic beads to magnet/carbon paste electrochemical transducer surface (B) binding of the IgG antigen to the antibodies on the magnetic beads (C) capture of the gold nanoparticle labelled secondary antibodies (D) electrochemical stripping detection of AuNPs. Reprinted with permission from Ref. [72].

Fig. 1.1 ELISA-like immunoarray strategy to detect proteins (PSA=prostate specific antigen) demonstrating some uses of nanoparticles. Gold nanoparticles on the spot areas are linked to primary antibodies that capture the protein analytes. After washing, a labeled secondary antibody, or as illustrated here a multi-labeled nanoparticle with attached secondary antibody, is added. This detection particle binds selectively to the captured analyte molecules. After additional washing with blocking agents to remove non-specific binding of the labeled species, electrical or optical detection is used to count the number of bound labels that is proprational to protein analyte concentration...

Aptamer based biosensors, for example for recombinant human erythropoietin (as model analyte), can be made more sensitive by amplification with a boronic acid tethered gold nanoparticle that is then associated with an alkaline phosphatase to produce a redox active probe molecule. A similar re-usable bio-immuno-sensor has been suggested for carcinoembryonic antigen. A phenylboronic acid is assembled on gold to (reversibly) bind the antibody horseradish peroxidase conjugate. Interaction with the antigen slows down the hydrogen peroxide reduction. An HIV-1 immunoassay based on electroluminescence has been proposed by Zhou etaV In this process the... 

---