Conjugation of Gold Nanorods with Bovine Serum Albumin Protein

We used polarized fluctuation correlation spectroscopy (p-FCS) to study the interaction of bovine serum albumin (BSA) with cetyltrimethylammonium bromide (CTAB) stabilized gold nanorods (AuNRs). The translational (D-T) and rotational diffusion (DR) of the BSA-NR conjugate were determined in varying concentrations of BSA. The measured diffusion coefficients were analyzed to determine the change of the hydrodynamic size of the particle due to protein adsorption. We found that the saturation coverage is less than one monolayer of protein at a BSA concentration of approximate to 1 mM. The adsorption isotherm was compared with the Langmuir and anticooperative binding models to quantify BSA-NR association. Our data can be interpreted in terms of hydrophobic interaction between the imperfect CTAB coating and the buried hydrophobic residues of the protein, which results in the loss of protein native conformation. We compared our study with previous experiments involving carboxylic-acid-stabilized nanosphere interaction with BSA molecules, and significant differences were found.