A colorimetric gold nanoparticle biosensor: effect of particle size on sensitivity

We have previously developed a label-free optical method to study biomolecular interactions in real time at the surface of an optically transparent substrate. The method relies on the change in the absorbance spectrum of a self-assembled monolayer of gold nanoparticles on glass as a function of biomolecular binding at the surface of the immobilized nanoparticles. Here, we report upon optimization of this sensor by examining the effect of particle size on the analytical sensitivity of the sensor. Increasing the diameter of the gold nanoparticles from 13 nm to 47 nm is shown to increase the sensitivity of the sensor by a factor of three for the model streptavidin-biotin receptor-ligand pair.