Spectroscopic and coarse-grained simulation studies of the BSA and HSA protein adsorption on silver nanoparticles

The photophysical properties of the bovine serum albumin (BSA) and human serum albumin (HSA) adsorbed on (non) functionalized Ag(0) nanoparticles have been studied by spectroscopic techniques. The surface plasmon resonance kinetic of the BSA/HSA-Ag(0) nanoparticle complexes has been assessed by UV-Vis absorption spectroscopy. Transmission electron microscopy analysis showed that the average size of the particles is similar to 9 nm and the core-shell structure of the protein-Ag(0) nanoparticle complexes has been supported by UV-Vis spectra. The structure, stability, dynamics, and conformation of the proteins have been investigated by steady-state, time-resolved fluorescence, and circular dichroism spectroscopy. Insights of the HSA conformation at the nanoparticle surface were obtained by the Monte Carlo simulations carried out using an appropriate coarse-grained model. The HSA conformation upon adsorption on the nanoparticle surface is distorted so that the Trp fluorescence is quenched and the a-helix content diminished. The adsorbed protein exhibited an extended conformation with Trp residue depleted from the nanoparticle surface and rather located toward the protein boundary. Experimental and simulated experiments were in good agreements and the results are discussed in terms of functional properties of the serum albumins in protein-Ag(0) nanoparticle complex.