Synthesis of catechol and zwitterion-bifunctionalized poly(ethylene glycol) for the construction of antifouling surfaces

The synthesis of catechol-containing small molecules and macromolecules always requires multiple reaction steps, coupling agents, or enzymes. In this study, a simple and scalable strategy for the preparation of catechol-containing poly(ethylene glycol) (CaPEG) by epoxide–amine polymerization of PEG diglycidyl ether with dopamine is described. The as-formed tertiary amine groups in the backbone of CaPEG can be converted into sulfobetaine structures in an alkylsulfonation step, leading to the formation of catechol and zwitterion-bifunctionalized PEG (SBCaPEG). The resulting catechol-containing CaPEG and SBCaPEG can be anchored on various substrate surfaces, including stainless steel (SS), titanium and silicon wafer, under mild conditions. Since SS is susceptible to fouling by a variety of microorganisms, the antifouling properties of the polymer-coated SS surfaces are studied in detail. The CaPEG- and SBCaPEG-coated SS surfaces effectively reduced the adsorption of protein (albumin–fluorescein isothiocyanate conjugate and bovine plasma fibrinogen), as well as the adhesion of bacteria (Pseudomonas sp. and Escherichia coli) and microalgae (Amphora coffeaeformis), as compared to that of the pristine SS surface. In comparison with the CaPEG-coated SS surfaces, the zwitterionic SBCaPEG-coated SS surfaces exhibited even better antifouling efficiencies.