Abstract

Gold nanoparticle surface provides a biocompatible vehicle for delivery and release of a protein or peptide based therapeutic or diagnostic agent at a targeted site. In order to realize this, understanding the interaction of proteins and peptides with the gold nanoparticle surface and the forces that stabilize or destabilize such interactions is imperative. In our work, we have studied adsorption of two proteins, alcohol dehydrogenase (ADH) and insulin on gold surface using the incoherent second harmonic light scattering technique. The second harmonic light intensity scattered from the gold nanoparticle in aqueous buffer solution is high due to strong surface polarization and is easily detectable. When proteins are added in small quantities to the solution, this intensity is quenched by adsorption of proteins to the surface. The normalized second harmonic intensity decay is fitted to a modified Langmuir type isotherm to get the binding constant (K), the free energy change (ΔG⁰), and the number of adsorbed protein molecules (n_ads). The number of adsorbed protein molecules varies with the size and thus the surface area of the gold nanoparticles which is shown in Fig.1.

© 2016 Optical Society of America