Organization of Functionalized Gold Nanoparticles by Controlled Protein Interactions

Gold colloidal particles were synthesized and modified by molecular self‐assembly. In addition, the reaction of biotinylated colloids with a tetrameric protein, avidin, was studied by optical absorption spectroscopy and dynamic light scattering. The modification involves the chemisorption of octadecanethiol on the gold, with the further attachment of alkyl biotin and cross‐linking with avidin molecules. The specific interaction of avidin with biotin leads to the controlled cross‐linking of particles. The degree of flocculation was quantified using a semi‐empirical flocculation parameter and its dependence on the biotinylation system was studied. The measured data were in good agreement, showing the possibility of regulating the aggregation rate and size of the aggregates using the experimental time, degree of biotinylation, and avidin concentration. The morphology of the self‐assembled gold monolayers, from the aggregated particles, was imaged by high‐resolution scanning electron microscopy. The structure of the thin particulate film depends on the bulk aggregate size and aggregation rate.