Single-Molecule Characterization of Gold Nanoparticle Bioconjugates with Rabbit IgG and EGFR Antibodies using Microwell Array Analysis

The use of nanoparticle bioconjugates (NBCs) as targeting and drug delivery vehicles is a growing area of research. A microwell-array based method has been developed to characterize NBCs at the single-particle level, in order to understand their surface chemistry and drive optimization of their preparation. Gold bipyramid nanoparticles are synthesized and functionalized with an alkanethiol self-assembled-monolayer (SAM). The nanoparticles are then bioconjugated with Rabbit IgG and Mouse EGFR complexes. . To test antibody-antigen interactions, the NBCs were exposed to corresponding antibodies, Goat Anti-Rabbit and Rat Anti-Mouse IgG respectively, labeled with horseradish peroxidase enzymes. Microwell arrays were loaded with the NBCs such that only that a small number of wells are occupied, along with fluorogenic substrate Amplex Red. The resulting intensity of the fluorescence in each microwell reflects the number of enzyme-labeled antibodies bound to the surface of the nanoparticle.