Efficient and Tunable Three-Dimensional Functionalization of Fully Zwitterionic Antifouling Surface Coatings

Abstract

To enhance the sensitivity and selectivity of surface-based (bio)sensors, it is of crucial importance to diminish background signals that arise from the nonspecific binding of biomolecules, so-called biofouling. Zwitterionic polymer brushes have been shown to be excellent antifouling materials. However, for sensing purposes, antifouling does not suffice but needs to be combined with the possibility to efficiently modify the brush with recognition units. So far this has been achieved only at the expense of either antifouling properties or binding capacity. Herein we present a conceptually new approach by integrating both characteristics into a single tailor-made monomer: a novel sulfobetaine-based zwitterionic monomer equipped with a clickable azide moiety. Copolymerization of this monomer with a well-established standard sulfobetaine monomer results in highly antifouling surface coatings with a large yet tunable number of clickable groups present throughout the entire brush. Subsequent functionalization of the azido brushes via widely used strain-promoted alkyne azide click reactions yields fully zwitterionic 3D-functionalized coatings with a recognition unit of choice that can be tailored for any specific application. Here we show a proof of principle with biotin-functionalized brushes on SiN that combine excellent antifouling properties with specific avidin binding from a protein mixture. The signal-to-noise ratio is significantly improved over that of traditional chain-end modification of sulfobetaine polymer brushes, even if the azide content is lowered to 1%. This therefore offers a viable approach to the development of biosensors with greatly enhanced performance on any surface.

Bioactive Antifouling Surfaces by Visible‐Light‐Triggered Polymerization

“…Nevertheless, neither of these approaches is able to fully prevent fouling from complex biological matrices such as blood plasma or serum . In contrast, polymer brushes created by grafting‐from methods have demonstrated remarkable resistance to biofouling from complex biological matrices, especially those based on zwitterionic polymers, such as polycarboxybetaines based on the corresponding methacrylate/amide (CBMA), polysulfobetaines from their methacrylate/amide precursor (SBMA), but also formally uncharged polymer brushes derived from N ‐(2‐hydroxypropyl) methacrylamide (HPMA) …”

“…Two recent examples led us to our current work. First, the combination of a sulfobetaine with a clickable but still zwitterionic sulfobetaine, which allows fully 3D loading of biomolecules . Second, a random copolymer brush of N ‐(2‐hydroxypropyl) methacrylamide and carboxybetaine methacrylamide (CBMAA), in which the latter could be bioconjugated via the use of activated ester reactions .…”

Laccase‐Mediated Grafting on Biopolymers and Synthetic Polymers: A Critical Review

“…In the grafting‐from approach, polymerisation of soluble monomers is initiated from the backbone of the composite or macromolecule. Surface‐initiated atom‐transfer radical polymerisation (SI‐ATRP) is often used to polymerise zwitterionic monomers via a radical initiator on the surface, so as to confer anti‐fouling properties to the surface . Lastly, grafting‐through involves the co‐polymerisation of bare monomers with monomers containing the graftable moiety to simultaneously form the graft and backbone …”

Mild and Selective C–H Activation of COC Microfluidic Channels Allowing Covalent Multifunctional Coatings

“…In addition, TFAAD is well-known for its ability to undergo further surface modifications for, for example, biological applications. 37,40,41 …”