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 gold nanoparticle surface with proteins and peptides is imperative. Here, we have studied the interaction of citrate-capped gold nanoparticle (GNPs) with lysozyme which is a globular protein by nondestructive label-free second harmonic light scattering (SHLS) technique at physiological pH. We have taken four different sizes of gold nanoparticle 15, 30, 40 and 70 nm. Due to the surface plasmons, GNP gives huge SHLS signal which we have utilized to see the interaction between lysozyme and different size of GNPs. We have followed the change in the SHLS intensity from nanomolar concentration of gold nanoparticles after addition of 20 microL aliquots of lysozyme and fitted the experimental data with extended modified Langmuir model. We found that the number of lysozyme which adsorbed on the surface of gold nanoparticles and induced aggregation of the same varied non linearly with the size of GNPs and the binding free energy is around -51 kJ/mol. Free energy change reveals that the interaction is weak.

Protein-Induced gold nanoparticle aggregation probed by label-free second harmonic light scattering

255th National Meeting (2018)

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