Synthesis and Characterization of Dendritic and Linear Glycol Methacrylates and Their Performance as Marine Antifouling Coatings

Investigating the anti-bioadhesion properties of short, medium chain length, and amphiphilic polyhydroxyalkanoate films

Silicone materials are widely used in fouling release coatings, but developing eco-friendly protection via biosourced coatings, such as polyhydroxyalcanoates (PHA) presents a major challenge. Anti-bioadhesion properties of medium chain length PHA and short chain length PHA films are studied and compared with a reference Polydimethylsiloxane coating. The results highlight the best capability of the soft and low-roughness PHA-mcl films to resist bacteria or diatoms adsorption as compared to neat PDMS and PHBHV coatings. These parameters are insufficient to explain all the results and other properties related to PHA crystallinity are discussed. Moreover, the addition of a low amount of PEG copolymers within the coatings, to create amphiphilic coatings, boosts their anti-adhesive properties. This work reveals the importance of the physical or chemical ambiguity of surfaces in their anti-adhesive effectiveness and highlights the potential of PHA-mcl film to resist the primary adhesion of microorganisms.

Antifouling Surfaces Based on Polyzwitterion Loop Brushes

Antifouling surfaces have attracted increasing interest in recent years due to their potential application in various fields. In this work, we report a loop polyzwitterionic coating that exhibits excellent resistance to protein adsorption. Triblock and diblock copolymers of 2-[(2-hydroxyethyl)disulfanyl]ethyl methacrylate) (HSEMA) and 2-(dimethylamino)ethyl methacrylate) (DMAEMA) were synthesized by atom-transferred radical polymerization, followed by betainization of the DMAEMA block with 1,3-propane sultone and reduction of the disulfide bond in HSEMA to yield a triblock copolymer comprising a zwitterionic poly(sulfobetaine methacrylate) (PSBMA) midblock and poly(2-sulfanylethyl methacrylate) (PSEMA) terminal blocks as well as its diblock analogue that was of the same composition as the former and half the chain length. Both copolymers adsorbed to the gold substrate via the thiol groups in the terminal PSEMA block(s), creating loop and linear PSBMA brush coatings of comparable thickness, as revealed by X-ray photoelectron spectroscopy and ellipsometry. Adsorption of bovine serum albumin and fibrinogen as model proteins from solution to these surfaces was investigated by a quartz crystal microbalance with dissipation and confocal laser scanning microscopy (CLSM), and platelet and bacterial adhesions were assessed by scanning electron microscopy and CLSM. The results demonstrate that both linear and loop polyzwitterion brushes are excellent in resisting the adsorption of the foulants, and the loop brushes are superior to the linear analogues.

Antifouling polymers for nanomedicine and surfaces: recent advances

Antifouling polymers are materials that can resist nonspecific interactions with cells, proteins, and other biomolecules. Typically, they are hydrophilic polymers with polar or charged moieties that are capable of strong nonbonding interactions with water molecules. This propensity to bind water generates a surface hydration layer that reduces nonspecific interactions with other molecules and is paramount to the antifouling behavior. This property is especially useful for nanoscale applications such as nanomedicine and surface modifications at the molecular level. In nanomedicine, antifouling polymers such as poly(ethylene glycol) and its alternatives play a key role in shielding drug molecules and therapeutic proteins/genes from the immune system within nanoassemblies, thereby enabling effective delivery to target tissues. For coatings, antifouling polymers help to prevent adhesion of cells and molecules to surfaces and are thus valued in marine and biomedical device applications. In this Review, we survey recent advances in antifouling polymers in the context of nanomedicine and coatings, while shining the spotlight on the major polymer classes such as PEG, polyzwitterions, poly(oxazoline)s, and other nonionic hydrophilic polymers.

Anti-Fouling and Anti-Biofilm Performance of Self-Polishing Waterborne Polyurethane with Gemini Quaternary Ammonium Salts

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings.

Bacterial surface attachment and fouling assay on polymer and carbon surfaces using Rheinheimera sp. identified using bacteria community analysis of brackish water

Biofouling on surfaces in contact with sea- or brackish water can severely impact the function of devices like reverse osmosis modules. Single species laboratory assays are frequently used to test new low fouling materials. The choice of bacterial strain is guided by the natural population present in the application of interest and decides on the predictive power of the results. In this work, the analysis of the bacterial community present in brackish water from Mashabei Sadeh, Israel was performed and Rheinheimera sp. was detected as a prominent microorganism. A Rheinheimera strain was selected to establish a short-term accumulation assay to probe initial bacterial attachment as well as biofilm growth to determine the biofilm-inhibiting properties of coatings. Both assays were applied to model coatings, and technically relevant polymers including laser-induced graphene. This strategy might be applied to other water sources to better predict the fouling propensity of new coatings.

Studying the Effect of Pre-Polymer Composition and Incorporation of Surface-Modifying Amphiphilic Additives on the Fouling-Release Performance of Amphiphilic Siloxane-Polyurethane Coatings

Combining amphiphilic fouling-release (FR) coatings with the surface-active nature of amphiphilic additives can improve the antifouling/fouling-release (AF/FR) properties needed to offer broad-spectrum resistance to marine biofoulants. This work is focused on further tuning the amphiphilic character of a previously developed amphiphilic siloxane-polyurethane (SiPU) coating by varying the amount of PDMS and PEG in the base system. Furthermore, surface-modifying amphiphilic additives (SMAAs) were incorporated into these amphiphilic FR SiPU coatings in varying amounts. ATR-FTIR, contact angle and surface energy measurements, and AFM were performed to assess changes in surface composition, wettability, and morphology. AF/FR properties were evaluated using laboratory biological assays involving Cellulophaga lytica, Navicula incerta, Ulva linza, Amphibalanus amphitrite, and Geukensia demissa. The surfaces of these coatings varied significantly upon changes in PDMS and PEG content in the coating matrix, as well as with changes in SMAA incorporation. AF/FR properties were also significantly changed, with formulations containing the highest amounts of SMAA showing very high removal properties compared to other experimental formulations, in some cases better than that of commercial standard FR coatings.

One-pot method for preparation of capsaicin-containing double-network hydrogels for marine antifouling

Marine biofouling which interferes with normal marine operation and also causes huge economic loss has become a worldwide problem. With the development of society, there is an urgent need to develop non-toxic and efficient anti-fouling strategies. Capsaicin is an environmentally friendly antifouling agent, but controlling the stable release of capsaicin from the coating is still a challenge to be solved. To achieve long-lasting antifouling property, in this work, we incorporate a derivative of capsaicin N-(4-hydroxy-3-methoxybenzyl)acrylamide (HMBA) to prepare double network (DN) hydrogels and make HMBA a part of the polymer network. Polyvinyl alcohol (PVA) has good hydrophilicity, and as a soft and ductile network, acrylamide (AM) and HMBA can polymerize to generate a rigid and brittle network. By adjusting the content of HMBA in the DN hydrogels, we can obtain a PVA–PAHX hydrogel with high mechanical strength, low swelling rate, and excellent antifouling effect, which provides a feasible way for the practical application of a hydrogel coating in long-term marine antifouling.

Double-network hydrogel coatings containing capsaicin analogs were prepared by a one-pot method based on a green strategy, by incorporating a derivative of capsaicin N-(4-hydroxy-3-methoxybenzyl) acrylamide into the polymer network. An antifouling effect can be achieved.

A novel Y-shaped photoiniferter used for the construction of polydimethylsiloxane surfaces with antibacterial and antifouling properties

The simultaneous introduction of two new functionalities into the same polymeric substrate under mild reaction conditions is an interesting and important topic. Herein, dual-functional polydimethylsiloxane (PDMS) surfaces with antibacterial and antifouling properties were conveniently developed via a novel Y-shaped asymmetric dual-functional photoiniferter (Y-iniferter). The Y-iniferter was initially immobilized onto the PDMS surface by radical coupling under visible light irradiation. Afterwards, poly(2-hydroxyethyl methacrylate) (PHEMA) brushes and antibacterial ionic liquid (IL) fragments were simultaneously immobilized on the Y-iniferter-modified PDMS surfaces by combining the sulfur(VI)-fluoride exchange (SuFEx) click reaction and UV-photoinitiated polymerization. Experiments using E. coli as a model bacterium demonstrated that the modified PDMS surfaces had both the expected antibacterial properties of the IL fragments and the excellent antifouling properties of PHEMA brushes. Furthermore, the cytotoxicity of the modified PDMS surfaces to L929 cells was examined in vitro with a CCK-8 assay, which showed that the modified surfaces maintained excellent cytocompatibility. Briefly, this strategy of constructing an antibacterial and antifouling PDMS surface has the advantages of simplicity and convenience and might inspire the construction of diverse dual-functional surfaces by utilizing PDMS more effectively.

Low Fouling Polysulfobetaines with Variable Hydrophobic Content

Amphiphilic polymer coatings combining hydrophilic elements, in particular zwitterionic groups, and hydrophobic elements comprise a promising strategy to decrease biofouling. However, the influence of the content of the hydrophobic component in zwitterionic coatings on the interfacial molecular reorganization dynamics and the anti-fouling performance is not well understood. Therefore, coatings of amphiphilic copolymers of sulfobetaine methacrylate 3-[N-2'-(methacryloyloxy)ethyl-N,N-dimethyl]-ammonio propane-1-sulfonate (SPE) are prepared which contain increasing amounts of hydrophobic n-butyl methacrylate (BMA). Their fouling resistance is compared to that of their homopolymers PSPE and PBMA. The photo-crosslinked coatings form hydrogel films with a hydrophilic surface. Fouling by the proteins fibrinogen and lysozyme as well as by the diatom Navicula perminuta and the green algae Ulva linza is assessed in laboratory assays. While biofouling is strongly reduced by all zwitterionic coatings, the best fouling resistance is obtained for the amphiphilic copolymers. Also in preliminary field tests, the anti-fouling performance of the amphiphilic copolymer films is superior to that of both homopolymers. When the coatings are exposed to a marine environment, the reduced susceptibility to silt incorporation, in particular compared to the most hydrophilic polyzwitterion PSPE, likely contributes to the improved fouling resistance.