Plasma protein binding of positively and negatively charged polymer-coated gold nanoparticles elicits different biological responses.

The binding of proteins to nanoparticles is an important event that can determine the biological effect of nanoparticles in the body. We examined plasma protein binding to gold nanoparticles (5-20 nm) with different surface charge. Positively and negatively charged nanoparticles bound a range of proteins whereas neutral nanoparticle bound very little. As little as 25% neutral polymer on the surface of the charged nanoparticles inhibited protein binding, with only slight change in surface charge. Fibrinogen bound with high affinity to both of the charged nanoparticles. However, binding kinetics and protease digestion suggested that the binding orientation for each nanoparticle was different. Only the negatively charged nanoparticles induced cytokine release from THP-1 cells. While common proteins can bind to different nanoparticles, the biological outcome may not be the same. Consequently, knowledge about the composition of the protein corona is not sufficient to predict biological effects of nanoparticles.