Effect of Gold Nanoparticles on the Conformation of\nBovine Serum Albumin: Insights from CD Spectroscopic Analysis and\nMolecular Dynamics Simulations

With the development of nanotechnology, there is growing interest\nin using nanoparticles (NPs) for biomedical applications, such as\ndiagnostics, drug delivery, imaging, and nanomedicine. The protein’s\nstructural stability plays a pivotal role in its functionality, and\nany alteration in this structure can have significant implications,\nincluding disease progression. Herein, we performed a combined experimental\nand computational study of the effect of gold NPs with a diameter\nof 5 nm (5 nm Au-NPs) on the structural stability of bovine serum\nalbumin (BSA) protein in the absence and presence of NaCl salt. Circular\ndichroism spectroscopy showed a loss in the secondary structure of\nBSA due to the synergistic effect of Au-NPs and NaCl, and Thioflavin\nT fluorescence assays showed suppressed β-sheet formation in\nthe presence of Au-NPs in PBS, emphasizing the intricate interplay\nbetween NPs and physiological conditions. Additionally, molecular\ndynamics (MD) simulations revealed that 5 nm Au-NP induced changes\nin the secondary structure of the BSA monomer in the presence of NaCl,\nhighlighting the initial binding mechanism between BSA and Au-NP.\nFurthermore, MD simulations explored the effect of smaller Au-NP (3\nnm) and nanocluster (Au-NC with the size of 1 nm) on the binding sites\nof the BSA monomer. Although the formation of stable BSA-Au conjugates\nwas revealed in the presence of NPs of different sizes, no specific\nprotein binding sites were observed. Moreover, due to its small size,\n1 nm Au-NC decreased helical content and hydrogen bonds in the BSA\nmonomer, promoting protein unfolding more significantly. In summary,\nthis combined experimental and computational study provides comprehensive\ninsights into the interactions among Au nanosized substances, BSA,\nand physiological conditions that are essential for developing tailored\nnanomaterials with enhanced biocompatibility and efficacy.