Assembly and Characterization of Biomolecule-Gold Nanoparticle Conjugates and Their Use in Intracellular Imaging

In this chapter, we outline protocols for assembling and characterizing peptide-gold nanoparticle conjugates. We describe two strategies for attaching peptides to gold nanoparticles. One involves the covalent coupling of cysteine-terminated peptides directly to a particle surface via a sulfur-gold bond. Alternatively, peptides are coupled to bovine serum albumin (BSA) via a bifunctional molecular crosslinker. We also describe a number of characterization methods for determining the number of crosslinkers per BSA, peptides per BSA, and peptides adsorbed per particle. Finally, we show that the enormous visible light extinction properties of gold nanoparticles make them excellent imaging agents for tracking the trajectories of peptides inside living cells.