Thermodynamic Analysis of Protein-Nanoparticle Interactions Links Binding Affinity and Structural Stability

Area of Science:

• Biomaterials Science
• Protein-Surface Interactions
• Nanotoxicology

Background:

• Nanoparticles and nanoplastics form protein coronas in biological fluids, influencing their interactions.
• Understanding the energetics of protein-surface binding is crucial but challenging.

Purpose of the Study:

• To investigate how protein charge distribution affects adsorption to polystyrene nanoparticles (PSNPs).
• To explore systematic perturbations in a model protein (GB3) to understand protein-surface interactions.

Main Methods:

• Generated lysine-to-alanine variants of the GB3 protein to alter charge distribution.
• Utilized isothermal titration calorimetry (ITC) to measure binding energetics.
• Performed fluorescence denaturation experiments to assess protein stability.

Main Results:

• The K19A protein variant exhibited the strongest binding to both functionalized and non-functionalized PSNPs.
• ITC data suggested K19A forms a stable monolayer, unlike other variants forming multilayers.
• Binding free energy strongly correlated with protein unfolding, indicating stability influences adsorption.

Conclusions:

• Protein charge distribution and stability are key determinants of adsorption thermodynamics to nanoparticles.
• Systematic modification of protein charge can control nanoparticle-protein interactions.
• Findings inform predictive models for protein-surface interactions in biological systems.