Zwitterionic dendrimer – Polymer hybrid copolymers for self-assembling antifouling coatings

Abstract

In this work, we show two different routes to synthesize polymer-dendrimer hybrids by the coupling of poly(l-lysine) and zwitterionic dendrimers (ZIDs). Poly(l-lysine) (PLL) is used because of its advantageous self-assembly properties onto silicon oxide by charged-based interactions between the lysine groups and the negatively charged surface, whilst the coupled ZIDs provide antifouling properties. The first route yields network-like structures in which PLL and ZIDs are crosslinked by multiple amide bonds. By using different ratios of PLL and ZID, we vary the size of the formed networks. A more defined, linear PLL-ZID macromolecule is formed via coupling of multiple ZIDs to PLL in a controlled way by a copper-catalyzed azide/alkyne cycloaddition (CuAAC) “click” reaction. Following synthesis and characterization of the two different types of PLL-ZID macromolecules, they are self-assembled on silicon oxide surfaces from aqueous solutions in a single step, to form thin, hydrophilic coatings. Their potential use as antifouling coatings is tested by fluorescence microscopy and quartz crystal microbalance (QCM) with foulants such a single proteins and diluted human serum. Finally, by performing an on-surface biofunctionalization step by biotin we demonstrate it is possible to use these polymer-dendrimer hybrids for selective detection of target analytes (here: streptavidin), while the underlying coating maintains its antifouling properties.This method presents a new, straightforward approach for the manufacturing of PLL-ZID based coatings that can be pre-synthesized partly or fully and applied as coating in a single self-assembly step. Both steps can take place in aqueous solution and under ambient conditions, and result in stable coatings that not only display antifouling properties but also maintain the possibility of further functionalization.