title: Zwitterionic poly(amino acid methacrylate) brushes.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Sheffield , Brook Hill, Sheffield S3 7HF, United Kingdom.
authors.forename: Abdullah M
authors.initials: AM
authors.lastname: Alswieleh
authors.forename: Nan
authors.initials: N
authors.lastname: Cheng
authors.forename: Irene
authors.initials: I
authors.lastname: Canton
authors.forename: Burcin
authors.initials: B
authors.lastname: Ustbas
authors.forename: Xuan
authors.initials: X
authors.lastname: Xue
authors.forename: Vincent
authors.initials: V
authors.lastname: Ladmiral
authors.forename: Sijing
authors.initials: S
authors.lastname: Xia
authors.forename: Robert E
authors.initials: RE
authors.lastname: Ducker
authors.forename: Osama
authors.initials: O
authors.lastname: El Zubir
authors.forename: Michael L
authors.initials: ML
authors.lastname: Cartron
authors.forename: C Neil
authors.initials: CN
authors.lastname: Hunter
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Leggett
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
mesh_terms: D057219:Biofouling; D002448:Cell Adhesion; D060326:Chemistry Techniques, Synthetic; D003545:Cysteine / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry; D010782:Photolysis; D012825:Silicon; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D008689:Methacrylates; D049452:Green Fluorescent Proteins; D003545:Cysteine; D012825:Silicon