Protein sorption to charged microgels: characterizing binding isotherms and driving forces

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Understanding protein-surface interactions is crucial for biomaterials and drug delivery.
• Existing models often oversimplify the complex interplay of electrostatic and steric forces.
• Protein sorption onto charged substrates like microgels involves dynamic changes in binding affinity.

Purpose of the Study:

• To develop advanced Langmuir binding models that account for electrostatic cooperativity in protein sorption.
• To quantitatively determine the intrinsic binding affinity of lysozyme to core-shell microgels.
• To elucidate the contributions of electrostatic, hydrophobic, and osmotic forces to the overall binding process.

Main Methods:

• Incorporation of Guoy-Chapman-Stern electrostatic models into Langmuir binding frameworks.
• Analysis of lysozyme sorption isotherms onto oppositely charged core-shell microgels.
• Deconvolution of total binding affinity into intrinsic and electrostatic contributions.

Main Results:

• The intrinsic binding affinity of lysozyme to microgels was determined to be approximately 7 k(B)T.
• Intrinsic binding affinity is salt-independent and predominantly hydrophobic.
• Total binding affinity is largely electrostatic, highly variable during sorption, and influenced by osmotic deswelling.

Conclusions:

• The developed models provide a more quantitative interpretation of protein binding isotherms.
• Electrostatic cooperativity significantly impacts protein sorption onto charged microgels.
• The study offers a refined understanding of protein-microgel interactions for diverse applications.