Surface charge control for zwitterionic polymer brushes: Tailoring surface properties to antifouling applications.
OBJECTIVE
Electrostatic interactions play an important role in adhesion phenomena particularly for biomacromolecules and microorganisms. Zero charge valence of zwitterions has been claimed as the key to their antifouling properties. However, due to the differences in the relative strength of their acid and base components, zwitterionic materials may not be charge neutral in aqueous environments. Thus, their charge on surfaces should be further adjusted for a specific pH environment, e.g. physiological pH typical in biomedical applications.


METHODS
Surface zeta potential for thin polymeric films composed of polysulfobetaine methacrylate (pSBMA) brushes is controlled through copolymerizing zwitterionic SBMA and cationic methacryloyloxyethyltrimethyl ammonium chloride (METAC) via surface-initiated atom transfer polymerization. Surface properties including zeta potential, roughness, free energy and thickness are measured and the antifouling performance of these surfaces is assessed.


RESULTS
The zeta potential of pSBMA brushes is -40 mV across a broad pH range. By adding 2% METAC, the zeta potential of pSBMA can be tuned to zero at physiological pH while minimally affecting other physicochemical properties including dry brush thickness, surface free energy and surface roughness. Surfaces with zero and negative zeta potential best resist fouling by bovine serum albumin, Escherichia coli and Staphylococcus aureus. Surfaces with zero zeta potential also reduce fouling by lysozyme more effectively than surfaces with negative and positive zeta potential.
NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Kent Ridge, Singapore 117576, Singapore.
Shanshan
S
Guo
Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore; Laboratory of Technological Processes, Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland. Electronic address: dominik.janczewski@ch.pw.edu.pl.
Dominik
D
Jańczewski
Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore. Electronic address: zhux@imre.a-star.edu.sg.
Xiaoying
X
Zhu
Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore.
Robert
R
Quintana
Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore.
Tao
T
He
NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Kent Ridge, Singapore 117576, Singapore; Department of Chemical & Biomolecular Engineering, National University of Singapore, Kent Ridge, Singapore 119260, Singapore. Electronic address: chenkg@nus.edu.sg.
Koon Gee
KG
Neoh
D000327:Adsorption; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000187:drug effects; D057219:Biofouling / Q000517:prevention & control*; D002417:Cattle; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D008689:Methacrylates / Q000737:chemistry* / Q000494:pharmacology; D009113:Muramidase / Q000037:antagonists & inhibitors / Q000737:chemistry; D058105:Polymerization; D012710:Serum Albumin, Bovine / Q000037:antagonists & inhibitors / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D055672:Static Electricity; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
C120889:2-(trimethylammonio)ethyl methacrylate; D000900:Anti-Bacterial Agents; D008689:Methacrylates; C521589:sulfobetaine methacrylate polymer; D014867:Water; D012710:Serum Albumin, Bovine; D012822:Silicon Dioxide; D009113:Muramidase
Antifouling; Mixed charge; Polymer brushes; Surface charge; Surface-initiated ATRP; Zeta potential