Combining high hydrophilicity with charge neutrality, polyzwitterions are intensely explored for their high biocompatibility and low-fouling properties. Recent reports indicated that in addition to ...charge neutrality, the zwitterion’s segmental dipole orientation is an important factor for interacting with the environment. Accordingly, a series of polysulfobetaines with a novel architecture was designed, in which the cationic and anionic groups of the zwitterionic moiety are placed at equal distances from the backbone. They were investigated by in vitro biofouling assays, covering proteins of different charges and model marine organisms. All polyzwitterion coatings reduced the fouling effectively compared to model polymer surfaces of poly(butyl methacrylate), with a nearly equally good performance as the reference polybetaine poly(3-(N-(2-(methacryloyloxy)ethyl)-N,N-dimethylammonio)propanesulfonate). The specific fouling resistance depended on the detailed chemical structure of the polyzwitterions. Still, while clearly affecting the performance, the precise dipole orientation of the sulfobetaine group in the polyzwitterions seems overall to be only of secondary importance for their antifouling behavior.
Layer-by-layer (LbL) assembly is a versatile platform for applying coatings and studying the properties of promising compounds for antifouling applications. Here, alginate-based LbL coatings were ...fabricated by alternating the deposition of alginic acid and chitosan or polyethylenimine to form multilayer coatings. Films were prepared with either odd or even bilayer numbers to investigate if the termination of the LbL coatings affects the physicochemical properties, resistance against the nonspecific adsorption (NSA) of proteins, and antifouling efficacy. The hydrophilic films, which were characterized using spectroscopic ellipsometry, water contact angle goniometry, ATR-FTIR spectroscopy, AFM, XPS, and SPR spectroscopy, revealed high swelling in water and strongly reduced the NSA of proteins compared to the hydrophobic reference. While the choice of the polycation was important for the protein resistance of the LbL coatings, the termination mattered less. The attachment of diatoms and settling of barnacle cypris larvae revealed good antifouling properties that were controlled by the termination and the charge density of the LbL films.
Amphiphilic coatings are promising materials for fouling-release applications, especially when their building blocks are inexpensive, biodegradable, and readily accessible polysaccharides. Here, ...amphiphilic polysaccharides were fabricated by coupling hydrophobic pentafluoropropylamine (PFPA) to carboxylate groups of hydrophilic alginic acid, a natural biopolymer with high water-binding capacity. Layer-by-layer (LbL) coatings comprising unmodified or amphiphilic alginic acid (AA*) and polyethylenimine (PEI) were assembled to explore how different PFPA contents affect their physicochemical properties, resistance against nonspecific adsorption (NSA) of proteins, and antifouling activity against marine bacteria (Cobetia marina) and diatoms (Navicula perminuta). The amphiphilic multilayers, characterized through spectroscopic ellipsometry, water contact angle goniometry, elemental analysis, AFM, XPS, and SPR spectroscopy, showed similar or even higher swelling in water and exhibited higher resistance toward NSA of proteins and microfouling marine organisms than multilayers without fluoroalkyl groups.
The fouling resistance of zwitterionic coatings is conventionally explained by the strong hydrophilicity of such polymers. Here, the in vitro biocompatibility of a set of systematically varied ...amphiphilic, zwitterionic copolymers is investigated. Photocrosslinkable, amphiphilic copolymers containing hydrophilic sulfobetaine methacrylate (SPe) and butyl methacrylate (BMA) were systematically synthesized in different ratios (50:50, 70:30, and 90:10) with a fixed content of photo-crosslinker by free radical copolymerization. The copolymers were spin-coated onto substrates and subsequently photocured by UV irradiation. Pure pBMA and pSPe as well as the prepared amphiphilic copolymers showed BMA content-dependent wettability in the dry state, but overall hydrophilic properties a fortiori in aqueous conditions. All polysulfobetaine-containing copolymers showed high resistance against non-specific adsorption (NSA) of proteins, platelet adhesion, thrombocyte activation, and bacterial accumulation. In some cases, the amphiphilic coatings even outperformed the purely hydrophilic pSPe coatings.
The three dominating polyzwitterion families, polyphosphatidylcholines, polycarboxybetaines, and polysulfobetaines, all of which provide high fouling resistance, have been complemented by a fourth ...one recently, the so‐called polysulfabetaines that combine ammonium with sulfate moieties. To elucidate the relationship between their structure and antifouling potential, coatings of a set of systematically varied poly(sulfabetaine methacrylate)s are investigated. In particular, the effects of the spacer groups, either separating the zwitterionic units from the polymer backbone, or the cationic from the anionic charges, are explored, studying the resistance against non‐specific protein adsorption and the accumulation of single species of marine biofouling organisms. All polysulfabetaines are at least as effective, or even more potent than the structurally closely related standard poly(sulfobetaine methacrylate). Their resistance against proteins and fouling organisms can be tuned via the betaine‐to‐backbone spacer. Overall, the polysulfabetaine coatings with the shorter ethylene spacer show higher resistance against non‐specific adsorption of proteins, in particular of lysozyme, or against colonization by diatoms. This may result from the higher steric constraints of the polymer attached zwitterions, favoring particularly advantageous conformations. Moreover, a shorter spacer between the oppositely charged ionic groups of the zwitterionic moiety reduces the settlement of cyprid larvae more effectively.
Poly(sulfabetaine methacrylate)s are explored as coatings against marine biofouling, investigating the effect of the spacer groups that separate the cationic ammonium from the anionic sulfate groups, and those separating the zwitterionic moiety from the backbone. While the shorter ethylene spacers provide the highest fouling‐resistance, the spacer type, inter‐charge or betaine‐to‐backbone, controls which particular organism is most effectively prevented from adhesion.
