Aggregation, stabilization, and binding between bovine serum albumin and gold nanoparticles of varying sizes

Abstract

Gold nanoparticles (GNPs) of different sizes are used in various biomedical applications. We explored the interaction between differently sized (5–60 nm) citrate-coated GNPs and bovine serum albumin (BSA). Using techniques such as dynamic light scattering, zeta potential, circular dichroism (CD) spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), and synchrotron X-ray absorption spectroscopy (XAS), we demonstrate that BSA significantly enhances the colloidal stability of GNPs by preventing aggregation. Addi­tionally, GNPs did not induce unfolding or loss of secondary structure in BSA, as confirmed by CD and ToF-SIMS, suggesting that BSA interacts with GNPs without disrupting its native conformation. Unlike previous studies on the interaction between GNPs and L-cysteine, ToF-SIMS revealed no preferential binding of gold to any specific functional groups in BSA. XAS suggested that BSA adsorption on the GNPs changed their electronic structure (replenishing electrons in the Au 5d orbital). Collectively, our results support the conclusion that BSA adsorbs onto citrate-coated GNPs through non-covalent, long-range interactions that preserve protein structure and enhance colloidal stability.