Amphoteric surface hydrogels derived from hydrogen-bonded multilayers: reversible loading of dyes and macromolecules

Area of Science:

• Materials Science
• Polymer Chemistry
• Biotechnology

Background:

• Surface-bound hydrogels offer tunable properties for various applications.
• Controlling hydrogel swelling and biomolecule interactions is crucial for advanced materials.

Purpose of the Study:

• To create pH-responsive surface hydrogels with controlled swelling and protein uptake.
• To investigate the pH-dependent behavior of hydrogels formed from poly(N-vinylpyrrolidone) and poly(methacrylic acid).

Main Methods:

• Fabrication of hydrogen-bonded multilayers of poly(N-vinylpyrrolidone) (PVPON) and poly(methacrylic acid) (PMAA).
• Selective chemical cross-linking of PMAA using carbodiimide chemistry and ethylenediamine (EDA).
• In situ attenuated total reflection Fourier transform infrared spectroscopy and in situ ellipsometry to study swelling and protein uptake.

Main Results:

• Hydrogels exhibited pH-dependent polyampholytic swelling, with minimum swelling at pH 4.2-5.7.
• Swelling was influenced by amino groups from the EDA cross-linker and was fast and reversible.
• Hydrogels demonstrated reversible absorption of dyes and proteins, and protein replacement with polycations.

Conclusions:

• The developed surface hydrogels show tunable, pH-responsive swelling and reversible biomolecule interactions.
• These materials are promising for applications in bioseparation and controlled delivery systems.
• The fabrication method allows for control over hydrogel properties by adjusting cross-linking time.