Non-covalent small molecule partnership for redox-active films: Beyond polydopamine technology

Area of Science:

• Materials Science
• Biochemistry
• Polymer Chemistry

Background:

• Polydopamine (PDA)-based films have limitations.
• Natural polymers like eumelanins and polyphenols possess biological activity.
• Hexamethylenediamine (HMDA) is explored to enhance film-forming properties of natural polymers.

Purpose of the Study:

• To investigate the use of HMDA for imparting film-forming ability to 5,6-dihydroxyindole-2-carboxylic acid methyl ester (MeDHICA).
• To characterize the resulting films and evaluate their properties.
• To assess the protective effects of these films against oxidative stress.

Main Methods:

• Reaction of MeDHICA and HMDA in aqueous buffer at pH 9.0.
• Investigation of reaction parameters (pH, diamine chain length).
• Analysis using voltammetry, AFM/SEM, HPLC, MALDI-MS, and 1HNMR.
• Evaluation of reducing activity and cytoprotective effects on HaCaT cells.

Main Results:

• Homogeneous, yellowish films with moderate hydrophobicity were formed.
• Film formation was optimal at pH 9 and induced by HMDA.
• Films comprised MeDHICA and HMDA, self-assembled via electrostatic interactions, not covalent bonds.
• Films exhibited strong reducing properties and protected keratinocytes from oxidative stress.

Conclusions:

• HMDA effectively induces film formation from MeDHICA via non-covalent self-assembly.
• The resulting MeDHICA/HMDA films possess significant antioxidant and cytoprotective capabilities.
• This approach broadens the application potential of bio-inspired functional materials.