Methoxy group substitution on catechol ring of dopamine facilitates its polymerization and formation of surface coatings

Publication date: 5 May 2017
Source:Polymer, Volume 116
Author(s): Jieyu Zhang, Yong Shung Cheah, Sridhar Santhanakrishnan, Koon Gee Neoh, Christina L.L. Chai
Deposition of polydopamine on substrates is a facile and effective method of surface modification and the deposited polydopamine can reduce silver ions to form silver nanoparticles (AgNPs) for antibacterial applications. However, polydopamine deposition is a time-consuming process that usually requires 24 h to produce a dense surface coating. Since oxidation of dopamine is critical for its polymerization, we hypothesize herein that substitution of an electron-donating group on the catechol ring of dopamine can enhance its oxidation potential and subsequently accelerate its polymerization. In this work, dopamine substituted with a 5-methoxy group (OMeDA) was prepared. OMeDA polymerized faster than dopamine under similar reaction conditions, resulting in a polymer coating of 13 nm thickness on a silicon surface after 8 h, compared to the 24 h required for dopamine to form a coating of similar thickness. A polymer layer with AgNPs can be directly formed on the silicon substrate after exposure to a solution containing OMeDA and silver nitrate. After 2 h exposure, the silver content on the modified surfaces prepared with OMeDA was 187% higher than that obtained with dopamine, and the antibacterial efficacy of the former against Staphylococcus aureus was correspondingly higher than that of the latter. This study demonstrates that OMeDA with an electron-donating group in the catechol ring offers improvements over dopamine for surface modification applications.

Graphical abstract

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