Binding behaviors and kinetics studies on the interaction of silver nanoparticles with trypsin

The interaction of nanoparticles (NPs) with proteins is a topic of high relevance for the medical application of nanomaterials. In this study, a comprehensive investigation was performed to clarify the binding mechanism, adsorption isotherms and kinetics of the interaction between silver nanoparticles (AgNPs) and trypsin. The experimental results indicate that the binding of AgNPs to trypsin seems to be a static quenching mechanism. Thermodynamic analysis reveals that AgNPs binding to trypsin is synergistically driven by enthalpy and entropy, and the major driving forces are hydrophobic and electrostatic interactions. The adsorption of trypsin on AgNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fit well with Freundlich model. The kinetics of adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicate that a pseudo-second-order kinetic equation describes better. The conformational change at the secondary structural level of trypsin induced by AgNPs was investigated with the circular dichroism (CD) measurements and no obvious changes in trypsin secondary structural elements are observed. These fundamental works will provide some new insights into the safe and effective application of AgNPs in biological and medical areas.