Poly(oxanorbornene)‐Based Polyzwitterions with Systematically Increasing Hydrophobicity: Synthesis, Physical Characterization, and Biological Properties

Abstract

Surfaces coated with polyzwitterions are known to resist protein adhesion and to be generally bio‐inert. In recent reports, several polyzwitterionic coatings with carboxylate groups and intrinsic antimicrobial activity due to the pH‐responsivity of that group are described, but the design rules to obtain such activity remain unclear. Therefore, in this work, a set of surface‐attached polyzwitterions with carboxylate groups and varying alkyl residues is studied. The gradually increasing hydrophobicity of these surfaces (verified by contact angle and swellability measurements) has an impact on their biological properties. Hydrophilic surfaces (polyzwitterions bearing short alkyl residues) behave like “classical” polyzwitterions: they repel proteins and human cells and are non‐toxic to bacteria. The more hydrophobic polyzwitterionic surfaces are protein‐adhesive, cell‐toxic, and can kill bacteria. This indicates that the hydrophobicity of polyzwitterionic surfaces needs to be balanced precisely to combine protein‐repellency and antimicrobial activity in a single material.

In vitro biocompatibility analysis of protein-resistant amphiphilic polysulfobetaines as coatings for surgical implants in contact with complex body fluids

“…While ethyl and butyl groups do neither affect the wettability nor the NSA of proteins, an increase of the alkyl chain length from hexyl to octyl increased the WCA and CBCA substantially and increased the NSA of fibrinogen (Fg). ( Paschke et al, 2022 ). Literature also reported that copolymers consisting of PC and BMA showed increasing resistance with increasing zwitterionic content with the highest resistance achieved by the highest zwitterionic content of 30%.…”

Antifouling polymers for nanomedicine and surfaces: recent advances

“…More recently, Lienkamp and coworkers have also reported poly(oxanorbornene)-based polyzwitterions (Fig. 17) whereby the hydrophilicity/hydrophobicity balance of the materials could be engineered at will, 95 thus allowing for fine control over their resulting properties and applications. Specifically, the polymers with short alkyl residues (e.g., Me) were more hydrophilic and antifouling than the analogs with longer alkyl chains, resisting adhesion to proteins and human cells easily but showing no antimicrobial activity.…”

“…More recently, Lienkamp and coworkers have also reported poly(oxanorbornene)-based polyzwitterions (Fig. 17) whereby the hydrophilicity/hydrophobicity balance of the materials could be engineered at will, 95 thus allowing for fine control over their resulting properties and applications. Specifically, the polymers with short alkyl residues ( e.g.…”

Spacer Effects in Sulfo‐ and Sulfabetaine Polymers on Their Resistance against Proteins and Pathogenic Bacteria

“…[17,18] Nevertheless, several recent reports note the susceptibility of PEG-based polymers to oxidation and the induction of immunogenic responses. [19][20][21] On top of a certain hydrophilicity, [22][23][24][25][26] a neutral net charge and hydrogen bond acceptors at the interface were identified as key design rules for inert coatings. [17] Zwitterionic materials [27][28][29] fulfill these requirements and are capable to form strong bonds with surrounding water molecules by electrostatically induced hydration.…”

“…On top of a certain hydrophilicity, [ 22–26 ] a neutral net charge and hydrogen bond acceptors at the interface were identified as key design rules for inert coatings. [ 17 ] Zwitterionic materials [ 27–29 ] fulfill these requirements and are capable to form strong bonds with surrounding water molecules by electrostatically induced hydration.…”