Zwitterionic poly(amino acid methacrylate) brushes

Abdullah M. Alswieleh, Nan Cheng, Irene Canton, Burcin Ustbas, Xuan Xue, Vincent Ladmiral, Sijing Xia, Robert E. Ducker, Osama El Zubir, Michael L. Cartron, C. Neil Hunter, Graham J. Leggett*, Steven P. Armes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

161 Citations (Scopus)


A new cysteine-based methacrylic monomer (CysMA) was conveniently synthesized via selective thia-Michael addition of a commercially available methacrylate-acrylate precursor in aqueous solution without recourse to protecting group chemistry. Poly(cysteine methacrylate) (PCysMA) brushes were grown from the surface of silicon wafers by atom-transfer radical polymerization. Brush thicknesses of ca. 27 nm were achieved within 270 min at 20 °C. Each CysMA residue comprises a primary amine and a carboxylic acid. Surface zeta potential and atomic force microscopy (AFM) studies of the pH-responsive PCysMA brushes confirm that they are highly extended either below pH 2 or above pH 9.5, since they possess either cationic or anionic character, respectively. At intermediate pH, PCysMA brushes are zwitterionic. At physiological pH, they exhibit excellent resistance to biofouling and negligible cytotoxicity. PCysMA brushes undergo photodegradation: AFM topographical imaging indicates significant mass loss from the brush layer, while XPS studies confirm that exposure to UV radiation produces surface aldehyde sites that can be subsequently derivatized with amines. UV exposure using a photomask yielded sharp, well-defined micropatterned PCysMA brushes functionalized with aldehyde groups that enable conjugation to green fluorescent protein (GFP). Nanopatterned PCysMA brushes were obtained using interference lithography, and confocal microscopy again confirmed the selective conjugation of GFP. Finally, PCysMA undergoes complex base-catalyzed degradation in alkaline solution, leading to the elimination of several small molecules. However, good long-term chemical stability was observed when PCysMA brushes were immersed in aqueous solution at physiological pH.

Original languageEnglish
Pages (from-to)9404-9413
Number of pages10
JournalJournal of the American Chemical Society
Issue number26
Publication statusPublished - 2 Jul 2014
Externally publishedYes


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