Binding of drugs to serum albumin determined by changes in surface plasmon resonance signal of gold nanoparticles

Surface plasmon resonance of metal nanoparticles shifts if these nanoparticles are coated with proteins (e.g. BSA or HSA). It is related to the changes of refractive index of medium around nanoparticles. A value of this shift depends on the kind of nanoparticles, kind of proteins and pH of solution in which proteins are solved and nanoparticles suspended. The further shift in surface plasmon resonance occurs if molecules of drugs are bound to these protein layer coating nanoparticles. This additional shift is called as biosensor response. It depends on the number of drug molecules bound to protein layer. By measurement of biosensor response the affinity constant for the binding of drug to proteins is determined in this paper. The surface plasmon resonance was used also to monitor the structural changes of albumin at different pH values. The interaction between gold nanoparticles and albumin was investigated by red-shift of extinction maximum of gold nanoparticles.