Immobilization of phenol-containing molecules on self-assembled monolayers on gold via surface chemistry

Various phenol-containing molecules such as flavonoids have a wide range of biological effects including anticancer, antimicrobial, and anti-inflammatory properties, and, therefore, they have become subjects of active research for various medicinal and biological applications. To construct applicable materials incorporated with phenol-containing molecules, strategies for immobilization of phenol-containing molecules on solid substrates are required. Although several immobilization methods have been devised and reported, mostly harnessing phenol functionality, however, development of a general immobilization method has been hampered due to its complicated chemical reactions and low reaction yields on surfaces. Furthermore, the use of phenol as a reaction center may compromise the biological activity of phenol-containing molecules. Here, we describe a simple, fast, and reliable method for the surface immobilization of phenol-containing molecules by introducing chemical functional groups, carboxylic acid, thiol, and azide, while maintaining phenol functionality by way of the Mannich-type condensation reaction. We examined the chemical functionalization of naphthol, tyrosine, and flavanone and their immobilization to the self-assembled monolayers on gold via various surface chemistries: the carbodiimide coupling reaction, Michael addition, and the 'click' reaction. We strongly believe our method can be a general and practical platform for immobilization of various phenol-containing molecules on surfaces of various materials.