Spectroscopic Analysis of the Interaction between Silver Nanoparticles and Trypsin

The rapid development of nanoparticles (NPs) and their broad applications in medicine caused concerns about biological effects and biosafety. Here, the interaction of silver NPs (Ag NPs) and trypsin is studied with ultravioletvisible spectra, circular dichroism, and fluorescence spectra. Trypsin is exposed to various sizes and concentrations of Ag NPs. The intensities of the trypsin ultraviolet-visible absorption peaks are proportional to the Ag NP concentration and size. In the circular dichroism spectra, there was evidence that Ag NPs affected the secondary structure of trypsin. Fluorescence spectra show that the formation of the protein-nanoparticle complexes alters the protein chromophore chemical environment or structure and quenches its fluorescence. Hence, the extent of Ag NP binding of trypsin depends on both NP concentration and size, and changes the Ag NPs physicochemical properties as well as the trypsin secondary structure. With regard to nanomaterial safety, the interaction of NPs with proteins must be explored further for establishing NP toxicity and design guidance.