Control of lysozyme adsorption by pH on surfaces modified with polyampholyte brushes

Area of Science:

• Biomaterials Science
• Surface Chemistry
• Protein Adsorption

Background:

• Controlling protein adsorption on surfaces is crucial for biomedical applications.
• Lysozyme's high isoelectric point (11.1) complicates pH-dependent adsorption control.
• Surface modification with polymers offers a strategy to tune protein-surface interactions.

Purpose of the Study:

• To investigate the pH-dependent adsorption of lysozyme on silicon surfaces modified with poly(2-(dimethylamino ethyl) methacrylate)-block-poly(methacrylic acid) (PDMAEMA-b-PMAA) diblock copolymer brushes.
• To determine the influence of the poly(methacrylic acid) (PMAA) block thickness on lysozyme adsorption.
• To explore the combined properties of PDMAEMA and PMAA in controlling protein adsorption.

Main Methods:

• Surface modification of silicon with PDMAEMA-b-PMAA diblock copolymer brushes.
• Varying the thickness of the outer PMAA block (lPMAA).
• Quantifying lysozyme adsorption at different pH values (4-10) using techniques like ellipsometry or QCM (not explicitly stated but implied).

Main Results:

• Good control of lysozyme adsorption by pH was achieved in the range of 4-10.
• The thickness of the outer PMAA block (lPMAA) critically influenced adsorption.
• Adsorption increased with pH for lPMAA < 10 nm, with a pH 10/pH 4 ratio up to 16.4.
• For lPMAA > 10 nm, adsorption resembled that on PMAA homopolymer brushes, indicating screening of the inner PDMAEMA block's protein-repellent effect.

Conclusions:

• PDMAEMA-b-PMAA diblock copolymer brushes enable tunable, pH-responsive lysozyme adsorption on silicon surfaces.
• The thickness of the PMAA block is a key parameter in controlling the adsorption behavior.
• Optimizing PMAA block thickness is essential to leverage the synergistic effects of both polymer blocks and achieve effective protein adsorption control.