Tunable surface wettability and pH-responsive 2D structures from amphiphilic and amphoteric protein microfibrils

Area of Science:

• Materials Science
• Biomaterials Engineering
• Surface Chemistry

Background:

• Protein microfibrils offer unique self-assembly properties.
• Developing advanced materials with tunable surface characteristics is crucial for various applications.
• Controlling material response to environmental stimuli like moisture and pH is an ongoing challenge.

Purpose of the Study:

• To fabricate 2D films and paper-like structures from amphiphilic and amphoteric protein microfibrils.
• To investigate the tunable surface hydrophilicity/hydrophobicity of these protein microfibril structures.
• To explore the moisture- and pH-responsive behaviors and controlled release capabilities of the fabricated films.

Main Methods:

• Facile fabrication of 2D films via casting ethanolic dispersions of protein microfibrils.
• Controlled adjustment of temperature and moisture levels during film formation.
• Characterization of surface properties (water contact angles), crystallinity, structural features (β structure, β-sheet), and responsive behaviors (moisture, pH).

Main Results:

• Protein microfibril films (60-170 μm thick) were successfully fabricated.
• Surface hydrophilicity/hydrophobicity was tuned by substrate interaction, with water contact angles ranging from 5° to 71°.
• Films exhibited high crystallinity (56%), significant β structure (64%), moisture-responsive glass transition temperature (Tg), pH-responsive swelling, and excellent wet resiliency across a wide pH range (0-10).
• pH-dependent release of methylene blue demonstrated amphoterism and potential for controlled release applications.

Conclusions:

• Amphiphilic and amphoteric protein microfibrils can be engineered into versatile 2D structures.
• These structures possess tunable surface properties, moisture and pH responsiveness, and controlled release capabilities.
• The developed materials hold promise for applications in advanced coatings, sensors, and drug delivery systems.