Conjugation of nanoparticles to proteins.

Nanoparticle-protein conjugates hold great promise in biomedical applications. Diverse strategies have been developed to link nanoparticles to proteins. This chapter describes a method to assemble and purify nanoparticle-protein conjugates. First, stable and biocompatible 1.5 nm gold nanoparticles are synthesized. Conjugation of the nanoparticle to the protein is then achieved via two different approaches that do not require heavy chemical modifications or cloning: cysteine-gold covalent bonding, or electrostatic attachment of the nanoparticle to charged groups of the protein. Co-functionalization of the nanoparticle with PEG thiols is recommended to help protein folding. Finally, structural characterization is performed with circular dichroism, as this spectroscopy technique has proven to be effective at examining protein secondary structure in nanoparticle-protein conjugates.