Hysteresis effects of the interaction between serum albumins and silver nanoparticles

The mechanisms and effects about the interaction between serum albumins and silver nanoparticles have been intensively studied by means of transmission electron microscopy (TEM), circular dichroism (CD) and ultraviolet-visible (UV-Vis) spectroscopy. The adsorption of serum albumins on the surface of silver nanoparticles is observed by TEM. The studies with the surface plasmon bands indicate that the electrostatic and hydrophilic interactions are the major forces between serum albumins and silver nanoparticles; the number of adsorbed monolayer serum albumin molecules to a silver nanoparticle with the size of 60 nm is about 6.7×105. The far-UV CD spectra provide the evidence that the secondary structure of adsorbed serum albumins adopt a looser and more extended conformation, in which the content of α-helix decreases, whereas the content of β-sheet, turn and unordered coil increases. Using time-scanning UV-Vis spectra to monitor the interacting process, the particular twofold hysteresis effects are significantly found with the coverage of aggregated silver nanoparticles and the conformational transition of serum albumins, respectively. The rate constants and the thermodynamics parameters about the hysteretic processes are also calculated.