Surface Adsorption and Molecular Modeling of Biofunctional Gold Nanoparticles for Systemic Circulation and Biological Sustainability

Abstract

Fundamental aspects of protein complex coated gold nanoparticles (Au NPs) were presented for their possible use in systemic circulation in terms of pharmaceutical formulations. For this purpose, protein complexes of bovine serum albumin (BSA), lysozyme (Lys), and zein with an industrial important bioactive polymer diethylaminoethyl dextran (DEAE) were studied in the presence of Au NPs. Surface adsorption of such complexes magnified DEAE–protein interactions which were easily monitored spectroscopically under the effect of temperature and reaction time. In vitro synthesis of Au NPs allowed a simultaneous adsorption of the DEAE–protein complex on the NP surface to achieve colloidal stability, which was dramatically influenced by the nature of the DEAE–protein complex. The DEAE–BSA complex demonstrated strong favorable mainly electrostatic interactions followed by DEAE–Lys, while DEAE–zein interactions were predominantly influenced by the hydrophobic nature of zein. At the molecular level, the interactions were evaluated from the molecular dynamics (MD) studies which focused on the protein surface charge, dihedral angle variations, and protein unfolding upon dextran–protein complexation as well as its surface adsorption. MD studies further helped us to identify specific amino acid residues which promoted such interactions among the DEAE and protein as well as the surface adsorption of DEAE–protein complexes and allowed the synthesis of suitable biofunctional Au NPs with interesting bioapplicability with blood cells. Biofunctional NPs coated with DEAE–BSA and DEAE–Lys complexes over the entire mixing range proved to be the best suited vehicles for biomedical applications in systemic circulation.