Thermodynamics of Protein Adsorption on Gold and Carbonaceous Nanoparticles Probed by Second Harmonic Light Scattering

Abstract

Over the past two decades, interaction of small molecules, peptides, and proteins with nanoparticles of various shapes and size have been keenly pursued for two reasons: to find application of these nanoparticle-molecule conjugates as sensors and drug delivery vehicles since the nanoparticle surface can be decorated with multiple agents with well-defined functions, and to understand and model adsorption of molecules on nanosurfaces by borrowing ideas from adsorption of gases on bulk solid substrates. In this thesis, I have investigated protein adsorption on gold and carbonaceous nanoparticles using a variety of techniques, including second harmonic light scattering (SHLS) from solution. The SHLS technique is fairly new in this application. It has certain specific advantages of high sensitivity, low background signal, etc., over the conventional analytical tools usually deployed for studying NP-protein conjugates. Due to high surface energy of NPs, proteins stick to the surface of the nanoparticle forming “NP-protein corona” (NPPC). The measurement of thermodynamic parameters like binding constant, binding stoichiometry (nsat), Gibb’s free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) associated with protein adsorption will help us understand the stability of the NPPC, which, in turn, will help design robust NPPCs for diagnostic and therapeutic applications.