Mie scattering and surface plasmon based spectroscopy for the detection of nanoparticle–protein interactions

A spectroscopic study of the kinetic interaction between protein and gold nanoparticles is presented here. Mie scattering in conjunction with excitation of surface plasmons on the surface of the nanoparticles allows access to kinetic information regarding the interactions. The influence of the geometrical shape and size of the nanoparticles regarding the binding of a protein is investigated. Spherical nanoparticles of 60 and 100 nm diameters as well as ellipsoidal (rod-shaped) particles of dimension 20 by 60 nm for the minor and major axes respectively have been used. By fitting the experimental data with theoretical predictions, the size of the nanoparticle and the distribution in the sample, the shape, the influence of sedimentation and the necessary kinetic parameters have been determined. Simulations were also carried out to predict the Raman spectra of selected molecules for in-depth analysis of the detailed reactions.