Antifouling Coatings Research Articles

An Imine-Functionalized Silicone-Based Epoxy Coating with Stable Adhesion and Controllable Degradation for Enhanced Marine Antifouling and Anticorrosion Properties.

Biofouling and corrosion of submerged equipment caused by marine organisms severely restrict the rapid development of the marine industry. Traditional antifouling or anticorrosion coatings typically serve a sole purpose and exhibit limited degradability upon failure, rendering them inadequate for current demands. Herein, a novel imine-functionalized command-degradable bio-based epoxy coating (SAHPEP-DDM) with enhanced integrated antifouling and anticorrosion performances was synthesized utilizing 1,3-bis (3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and syringaldehyde. Compared with commercial epoxy resins (E51-DDM) and polydimethylsiloxanes (PDMS), the SAHPEP-DDM coating exhibits superior antifouling and anticorrosion properties due to the existence of -C=N- and Si-O-Si chain segments in the cross-linking network. The coating achieves resistance rates of 99.59 % and 99.20 % against E. coli and S. aureus, respectively, and shows promising resistance against algae and proteins, as well as excellent corrosion resistance in artificial seawater (with |Z|0.01 Hz and arc radius of about 1011 Ω and exceeding 1010 Ω respectively). The coating also exhibits excellent chemical resistance in organic solvents as well as neutral and alkaline environments. Moreover, its controlled degradation after coating failure can be achieved in acid aqueous solutions through temperature and acidity adjustments, facilitated by the presence of -C=N-. This work presents a novel degradable coating successfully coupled the dual functions of antifouling and anticorrosion coatings, avoiding the employment of intermediate coat, indicating vast potential for application in various marine engineering fields.

Prevention and Control of Biofouling Coatings in Limnoperna fortunei: A Review of Research Progress and Strategies.

The increasing environmental concerns of conventional antifouling coatings have led to the exploration of novel and sustainable solutions to address the biofouling caused by Limnoperna fortunei. As a rapidly expanding invasive species, the fouling process of Limnoperna fortunei is closely associated with microbial fouling, posing significant threats to the integrity of aquatic infrastructure and biodiversity. This review discusses recent progress in the development of non-toxic, eco-friendly antifouling coatings that are designed to effectively resist biofouling without using toxic chemicals. Recent research has focused on developing novel non-toxic coatings that integrate natural bioactive components with advanced material technologies. These formulations not only meet current environmental standards and exhibit minimal ecological impact, but also possess significant potential in preventing the attachment, growth, and reproduction of Limnoperna fortunei. This review aims to provide scientific guidance by proposing effective and sustainable solutions to address the ecological challenges presented by Limnoperna fortunei. The insights gained from current research not only reveal novel antifouling methods, but also identify key areas for further investigation aimed at enhancing performance and environmental compatibility.

Antifouling activity of PEGylated chitosan coatings: Impacts of the side chain length and encapsulated ZnO/Ag nanoparticles

PEGylation is regarded as a common antifouling strategy and the effect is normally linked with surface hydrophilicity of the coatings. Herein, the biopolymer chitosan (CS) was grafted by polyethylene glycol (PEG) of different chain lengths (molecular weight 200, 4 k and 100 k Da) to verify if the hydrophilicity of CS-PEG coatings is crucial in determining antifouling activities and if PEG chain length influences biofouling in marine environment. Properties of copolymers such as melting points and crystallinity are affected by grafting PEG. The water contact angle (WCA) of CS-PEG coatings increases with the chain length of grafted PEG, from 27° to 58°. Photocatalyst of zinc oxide-silver (ZnO/Ag) was also studied and its embedment (2 % to CS-PEG) renders the surface of CS-PEG coatings more hydrophobic with WCA increased from 52° to 86°. Antibacterial, anti-diatom, and anti-biofilm activities of the coatings were evaluated in natural sea water. The bacterial density on CS-PEG coatings was dramatically reduced to 4 × 104 compared to the control of 7 × 104 ind/mm2, and further to 2 × 104 for CS-PEG-ZnO/Ag coatings. CS-PEG coatings also strongly inhibit diatoms (120–200 ind/mm2), but the inclusion of ZnO/Ag did not obviously enhance such effect (50–150 ind/mm2). The findings provide useful insights for designing polymer-based antifouling coatings.

Surface morphology-controlled poly(ε-caprolactone) nanofiber anti-fouling coating: A promising approach for marine applications

Abstract To effectively combat marine biofouling, biomimetic anti-fouling coatings have garnered widespread attention as a novel anti-fouling method. Based on this biomimetic concept, this study adjusted the electrospinning process parameters and selected different solvent systems to effectively modify the surface morphology of poly (ॉ-caprolactone) (PCL) nanofiber coatings, developing a non-toxic anti-fouling smooth surface. These biodegradable slippery liquid-infused porous surfaces (SLIPS) coatings offer a simple way to prepare maritime anti-fouling coatings in an eco-friendly manner. They can withstand a variety of liquid, material, and microbiological contaminations.

Mechanically durable plant-based composite surface towards enhanced antifouling properties

The biofouling adhering to underwater facilities has a negative impact on the environment, energy, and economic development. However, conventional anti-adhesion organic silicon and organic fluorine materials often have poor adhesion properties and mechanical stability when combined with substrates. This work presents a novel strategy for preparing composite antifouling coatings that low surface energy plant-based carnauba wax (CW) covering through rough substrates and chemically bond with flexible polydimethylsiloxane (PDMS) oligomers or polymers. The CW coating adheres strongly to the substrate owing to the mobility of the liquated CW, which flows into the micro-nano structure of the substrate and solidifies on the solid surface. The polymerization reaction of (PDMS) oligomers compounded the coating, thereby creating a composite coating with superior lubricating and antifouling properties. This distinctive bonding process imbued the coating with exceptional characteristics, including remarkable mechanical stability in destructive tests as well as an impressive ability to repel fouling, such as protein attachment, bacterial adhesion, diatom deposition, and biofilm formation. This work systematically investigated the impact of the composition and structure of composite materials on their mechanical stability and resistance to fouling, and developed high-performance antifouling coatings in the real world.

Antimicrobial and antifouling hyaluronic acid-cobalt nanogel coatings built sonochemically on contact lenses

The wearing of contact lenses (CLs) may cause bacterial infections, leading in turn to more serious complications and ultimately vision impairment. In this scenario, the first step is the adhesion of tear proteins, which provide anchoring points for bacterial colonization. A possible solution is the functionalization with an antimicrobial coating, though the latter may also lead to sight obstruction and user discomfort. In this study, adipic acid dihydrazide-modified hyaluronic acid-cobalt (II) (HA-ADH-Co) nanogels (NGs) were synthesized and deposited onto commercial CLs in a single-step sonochemical process. The coating hindered up to 60 % the protein adsorption and endowed the CLs with strong antibacterial activity against major ocular pathogens like Staphylococcus aureus and Pseudomonas aeruginosa, reducing their concentration by around 3 logs. Cytotoxicity assessment with human corneal cells demonstrated viabilities above 95 %. The nanocomposite coating did not affect the optical power and the light transmission of the CLs and provided enhanced wettability, important for the wearer comfort.

Highly dispersed nanocomposite based on magnesium ion modified and silver nanoparticles loaded graphene oxide for enhanced antibacterial activity of silicone coatings

Silver nanoparticles (Ag NPs) possess excellent antibacterial properties and have received widespread attention. However, the poor dispersion and easy aggregation of Ag NPs can severely diminish their antibacterial efficacy, limiting their practical applications. In this work, we report a simple method for preparing graphene oxide (GO) nanocomposites (Mg-GO/Ag NPs), in which GO is modified by Mg2+ and uniformly loaded with Ag NPs. The Ag NPs have an average diameter of approximately 11.14 nm, and uniformly are deposited on the surface of the GO. Compared with GO, the dispersion of Mg-GO/Ag NPs in deionized water (DW) and N, N-dimethylformamide (DMF) is significantly improved. The reaction principle of preparing Mg-GO/Ag NPs was revealed by gas chromatography–mass spectrometry (GC–MS). Additionally, we studied the antibacterial properties of Mg-GO/Ag NPs coatings against marine bacteria and Navicula tenera. This study introduces a novel approach for the preparation of high-efficiency silver-based antifouling coatings, with promising potential for a wide range of marine antifouling applications.

Ultraviolet-cured polyurea-polyurethane acrylate/polysiloxane hybrid anti-fouling coatings with superior mechanical properties, transparency, and durability

The demand for rapidly preparing omniphobic liquid-like anti-fouling coatings has become increasingly important across a wide range of applications. However, achieving a rapid fabrication process that results in coatings with effective anti-fouling properties, alongside the comprehensive performance of the coatings such as hardness, flexibility, transparency, and abrasion resistance, remains a significant challenge. Herein, this paper proposes a synergistic strategy combining ultraviolet (UV) curing and organic/inorganic hybridization, which involves the rapid cross-linking of hyperbranched methacryloxypropyl polysiloxanes (HMO), polyurea-polyurethanes acrylate (SPUA) and bis-vinyl terminated polydimethylsiloxanes (PDMS-bvt) containing multiple double bonds under UV curing for just 60 s. Notably, HMO imparts excellent hardness (7H) and abrasion resistance, while SPUA enhances the coating's flexibility (2 mm bending diameter) and adhesion (5B). The anti-fouling properties of the coating are attributed to PDMS-bvt, which provides self-cleaning, anti-graffiti, and anti-fingerprint capabilities. Additionally, the coating's hydrophobicity and smooth surface significantly reduce ice adhesion strength (21.13 ± 6.9 kPa), offering a passive anti-icing effect. Furthermore, the coating exhibits excellent transparency, with a transmittance of >92 % in the visible region. The coating exhibits remarkable durability, maintaining its anti-fouling performance after exposure to mechanical abrasion (500 abrasion cycles and 1000 bending/release cycles), chemical corrosion (24 h of immersion in organic solutions), and UV aging (168 h). This strategy presents a fast and effective method for preparing multifunctional anti-fouling coatings, with potential applications on foldable screens, high-rise building glazing, and curved surfaces.

Enhanced antifouling and anti-swarming properties poly (sulfobetaine methacrylate-co-2-hydroxy-3-phenoxypropyl acrylate) hydrogel coatings for urinary catheters

Catheter-associated urinary tract infection (CAUTI) remains an unsolved challenge to date, particularly with the emergence and rapid spread of antimicrobial-resistant bacterial pathogens. Despite extensive research, a catheter coating that can offer intrinsic resistance to host protein deposition, bacterial biofilm formation, and swarming is still urgently required. Zwitterionic hydrogel coatings due to their superior lubricity and antifouling properties represent a promising candidate, but their weak mechanical stability in water and poor resistance to bacterial swarming migration limit their application in urinary catheters for infection control. In this research, we describe the fabrication of a multifunctional catheter coating by copolymerizing zwitterionic sulfobetaine methacrylate (SBMA) polymers and a swarming inhibitor material, 2-hydroxy-3-phenoxypropyl acrylate (HPA). The introduction of polyHPA (PHPA) effectively impeded the uncontrolled swelling behavior of the zwitterionic PSBMA hydrogel, resulting in enhanced mechanical stability. Moreover, the copolymer coating retains the antifouling and anti-swarming properties of the homopolymers when challenged with fibrinogen, Escherichia coli, and Proteus mirabilis. The HPA content significantly correlated with its anti-adhesion activity against fibrinogen and biofilm, and the coating with an SBMA: HPA monomer feed molar ratio of 4:1 showed the best antifouling activity, reducing fibrinogen deposition by about 40 % and biofilm coverage by around fourfold compared to the uncoated polydimethylsiloxane (PDMS) surface. Furthermore, the copolymer coating also exhibited no cytotoxicity, suggesting it as a promising catheter coating for preventing CAUTI.

Research Progress of Marine Anti-Fouling Coatings

The extended immersion of ships in seawater frequently results in biofouling, a condition characterized by the accumulation of marine organisms such as barnacles and algae. To combat this issue, the application of anti-fouling coatings to the hull surfaces of vessels has emerged as one of the most effective strategies. In response to the increasing global emphasis on environmental sustainability, there is a growing demand for anti-fouling coatings that not only demonstrate superior anti-fouling efficacy but also adhere to stringent environmental standards. The traditional use of organotin-based self-polishing anti-fouling coatings, known for their high toxicity, has been prohibited due to environmental concerns. Consequently, there is a progressive shift toward the development and application of environmentally friendly anti-fouling coatings. This paper reviews the toxicity and application limitations associated with conventional anti-fouling coatings. It provides a comprehensive overview of recent advancements in the field, including the development of novel self-polishing anti-fouling coatings, low surface energy coatings, biomimetic coatings, and nanostructured coatings, each leveraging distinct anti-fouling mechanisms. The paper evaluates the composition and performance of these emerging coatings and identifies key technical challenges that remain unresolved. It also proposes a multi-faceted approach to addressing these challenges, suggesting potential solutions for enhancing the effectiveness and environmental compatibility of anti-fouling technologies. The paper forecasts future research directions and development trajectories for marine anti-fouling coatings, emphasizing the need for continued innovation to achieve both environmental sustainability and superior anti-fouling performance.

Stable Air Retention under Water on Artificial Salvinia Surfaces Enabled by the Air Spring Effect: The Importance of Geometrical and Surface‐Energy Barriers, and of the Air Spring Height

AbstractSuperhydrophobic surfaces that can remain dry under water have a high potential as nontoxic antifouling coatings or for drag‐reducing ship coatings. The Salvinia effect leads to impressive stable air layers on underwater submerged floating plants Salvinia, decisively determined by the hydrophilic tips of the otherwise hydrophobic Salvinia hairs (Salvinia paradox). The water adheres to these hydrophilic tips, stabilizing the water–air interface. An even more important contribution to the stability of the air layer is provided by the air spring, which is formed by the air volume bound by the hydrophilic leaf edge and the leaf base. Using an artificial Salvinia model with hydrophobic pillars (syn‐trichomes), how the stability against pressure changes in water depends on the height of the artificial hair is systematically shown: a reduction of the air spring height from 3 mm to 300 µm increases the stability against negative pressure by 500% from 72 to 380 mbar. Thicker air layers react much more strongly when subjected to overpressure (1000 mbar). It is also shown that the presence of a boundary is essential for the function of the air spring: removing the limiting hydrophilic edge around the hydrophobic air spring reduces the stability against negative pressure by 300%.

Copper tannate nanosheets-embedded multifunctional coating for antifouling and photothermal bactericidal applications

Implant-associated infections (IAIs), triggered by pathogenic bacteria, are a leading cause of implant failure. The design of functionalized coatings on biomedical materials is crucial to address IAIs. Herein, a multifunctional coating with good antifouling effect and antibacterial photothermal therapy (aPTT) performance was developed. The copper tannate nanosheets (CuTA NSs) were formed via coordination bonding of Cu2+ ions and tannic acid (TA). The CuTA NSs were then integrated into the TA and poly(ethylene glycol) (PEG) network to form the TCP coating for deposition on the titanium (Ti) substrates via surface adhesion of TA and gravitational effect. The resulting Ti-TCP substrate exhibited good antifouling property, reactive oxygen species (ROS) scavenging capability and cytocompatibility. The TCP coating exhibited antifouling efficacy in conjunction with aPTT, curtailing the surface adhesion and biofilm formation of pathogens, such as Staphylococcus aureus and Escherichia coli. Notably, the Ti-TCP substrate also exhibited the ability to prevent bacterial infection in vivo in a subcutaneous implantation model. The present work demonstrated a promising approach in designing high-performance antifouling and photothermal bactericidal coatings to combat IAIs.

Progress in the Development of Antifouling Electrochemical Biosensors

Electrochemical biosensors a subclass of biosensors, consisting of a biosensing element and an electrochemical transducer, have been widely used in various fields due to their excellent performance and portable device. However, in complex actual samples, non-specific adsorption of proteins and solid particles, and adhesion of cells and bacteria will lead to problems such as reduced sensor sensitivity, prolonged response time, and expanded detection errors. Therefore, constructing antifouling sensing platforms to effectively resist the bioadhesion of non-targets is crucial for the performance of biosensors. This study first introduces the commonly used classifications of electrochemical biosensors and their main contaminants. It also provides a comprehensive overview of the construction methods and application research of electrochemical antifouling sensors using different strategies, including the construction of physical, chemical and biological modification interfaces. In addition, the research progress on antifouling and antibacterial dual-action coatings for electrochemical detection is also reviewed. Finally, the challenges and future development trends of various methods are summarized, providing clues for better practical applications of electrochemical biosensors.

Self-growing composite photocatalytic materials for surface self-renewal of marine antifouling coatings

The attachment of marine organisms leads to the problem of marine biofouling. Biofouling can be prevented by using antifouling coatings this provided a low surface energy surface to inhibit the attachment of marine organisms. However, microorganisms inevitably attach during their use, leading to failure of the fouling release coating. To address this problem, we report an innovative strategy of doping photocatalytic materials into silicone coatings. This approach enables the degradation of bacterial carcasses and their secretions, leading to surface self-renewal and extended fouling protection. In this work, we report the controlled crystallisation of Ag-TiO2 nanomaterials (APTES-Ag@TiO2) using various methods influenced by aminopropylsilane. This strategy ensures the full utilisation of sunlight and strong interfacial adhesion, thereby preventing the degradation of photocatalytic performance. APTES-Ag@TiO2 not only has a self-growth effect and excellent photocatalytic performance but also facilitates the degradation of bacterial carcasses, thereby renewing the surface in organosilicon coatings.

AgNP Composite Silicone-Based Polymer Self-Healing Antifouling Coatings.

Biofouling poses a significant challenge to the marine industry, and silicone anti-biofouling coatings have garnered extensive attention owing to their environmental friendliness and low surface energy. However, their widespread application is hindered by their low substrate adhesion and weak static antifouling capabilities. In this study, a novel silicone polymer polydimethylsiloxane (PDMS)-based poly(urea-thiourea-imine) (PDMS-PUTI) was synthesized via stepwise reactions of aminopropyl-terminated polydimethylsiloxane (APT-PDMS) with isophorone diisocyanate (IPDI), isophthalaldehyde (IPAL), and carbon disulfide (CS2). Subsequently, a nanocomposite coating (AgNPs-x/PDMS-PUTI) was prepared by adding silver nanoparticles (AgNPs) to the polymer PDMS-PUTI. The dynamic multiple hydrogen bonds formed between urea and thiourea linkages, along with dynamic imine bonds in the polymer network, endowed the coating with outstanding self-healing properties, enabling complete scratch healing within 10 min at room temperature. Moreover, uniformly dispersed AgNPs not only reduced the surface energy of the coating but also significantly enhanced its antifouling performance. The antibacterial efficiency against common marine bacteria Pseudomonas aeruginosa (P.sp) and Staphylococcus aureus (S.sp) was reduced by 97.08% and 96.71%, respectively, whilst the diatom settlement density on the coating surface was as low as approximately 59 ± 3 diatom cells/mm2. This study presents a novel approach to developing high-performance silicone antifouling coatings.

Self-sustaining antifouling coating for underwater solar cells

If not protected, underwater solar cells are encrusted with biological organisms, such as algae and barnacles, which lower the electrical or operational efficiency and are expensive to remove. We engineered a self-sustaining antifouling coating using ultra-low concentrations of nano-sized, seawater-soluble pigments, specifically cuprous oxide (Cu2O) and zinc oxide (ZnO), combined with an organic booster biocide and a fast-polishing binder material. This coating maintained high levels of visible light transmission for three months in tropical seawater without requiring human intervention, such as mechanical cleaning. Field tests demonstrated the coating's effectiveness in preventing biofouling, while preserving transparency. We anticipate that these self-sustaining antifouling coatings can be applied to thin, transparent, and interchangeable substrates for continual replacement on solar-powered autonomous underwater vehicles or solar cell platforms, thereby ensuring long-term operational efficiency.

Rare earth oxide nanoparticles for superhydrophobic, antifouling and self-cleaning coatings

The widely used rare earth oxides (REOs) have a limited application in antifouling coatings. Here, coatings composited with REOs-1H,1H,2H,2H-perfluorodecytrimeth-oxysilane (REOs-FAS) based on hydrothermal reaction were prepared for study if REOs can be used in marine antifouling coatings. A network consisting of polydimethylsiloxane (PDMS) and REOs-FAS (REOs-FAS/PDMS) (RE = Ce, Pr, Nd) was created by using the blending method and polymerization reaction. The presence of the REOs-FAS imparts to the polymers an amphiphobic structure and disrupts the cell membrane, resulting in excellent antifouling properties and antibacterial performance. The water, coffee, and soya-bean milk droplet state on the Pr6O11-FAS/Sylgard 184 silicone elastomer with the ratio of 4:1 (PFSR-4) and the ink self-cleaning experiment demonstrated that the PFSR-4 has a perfect self-cleaning property. The most suitable surface roughness of PFSR-4 not only empowered the superhydrophobic (the contact angle of water is as high as 157° ± 2° and the sliding angle of water is as low as 5° ± 2°)-oleophobic characteristic (the contact angle of diiodomethane is as high as 132° ± 3°), but also endowed the coating with the anti-diatom (as high as 97.7 %) and anti-mussel adhesive properties. Moreover, the colored PFSR coatings were prepared to do another barrier for the adhesion of large fouling organisms, especially for the white coatings. The anti-mussel attachment ratio of purely whited PDMS was high to 84.6 %. The antibacterial REOs are appropriate for preparing multi-functional coatings. In general, the designed coating has the potential to be a durable, self-cleaning, antibacterial, and antifouling coating and could serve as a foundation for developing innovative super-amphiphobic coatings.

Polydopamine-functionalized polyethersulfone membrane: A paradigm advancement in the field of α-amylase stability and immobilization

Biocatalytic membranes have great potential in various industrial sectors, with the immobilization of enzymes being a crucial stage. Immobilizing enzymes through covalent bonds is a complex and time-consuming process for large-scale applications. Polydopamine (PDA) offers a more sustainable and eco-friendly alternative for enzyme immobilization. Therefore, surface modification with polydopamine as mussel-inspired antifouling coatings has increased resistance to fouling. In this study, α-amylase enzyme was covalently bound to a bioactive PDA-coated polyethersulfone (PES) membrane surface using cyanuric chloride as a linker. The optimal activity of α-amylase enzyme immobilized on PES/PDA membrane was obtained at temperature and pH of 55°C and 6.5, respectively. The immobilized enzyme can be reused up to five reaction cycles with 55 % retention of initial activity. Besides, it maintained 60 % of its activity after being stored for five weeks at 4°C. Additionally, the immobilized enzyme demonstrated increased Michaelis constant and maximum velocity values during starch hydrolysis. The results of the biofouling experiment of various membranes in a dead-end cell demonstrated that the PES membrane’s water flux increased from 6722.7 Lmh to 7560.2 Lmh after PDA modification. Although α-amylase immobilization reduced the flux to 7458.5 Lmh due to enhanced hydrophilicity, compared to unmodified membrane. The findings of this study demonstrated that the membrane produced through co-deposition exhibited superior hydrophilicity, enhanced coating stability, and strong antifouling properties, positioning it as a promising candidate for industrial applications.

A Zwitterionic Anti-Fouling Coating Promotes Electrochemical Biosensing in Complex Media

Biofoulants present in complex media, such as blood, plasma, saliva, etc., can cause an increase in the background of the signal or a reduction in signal-to-noise ratio, due to which most biosensors require a sample processing step. One of the major interactions for biofouling in biosensing platforms is non-specific hydrophobic interactions, which can be prevented using hydrophilic polymeric coatings [1], [2]. However, most hydrophilic polymers are not conductive enough to provide a strong electrochemical current signal, whereas the existing conductive polymers are often hydrophobic. To avoid this, zwitterionic polymers that are both ionically conductive [3] and hydrophilic [3] can be used as anti-fouling polymers for electrochemical biosensing. Additionally, these polymers are highly effective at preventing fouling by electrostatically-induced water structuring [4]. Herein, we report a zwitterionic polymer (bearing thiols, aldehydes and carboxylic acid groups) that forms a thin conductive and hydrophilic layer on the electrodes, while also housing biorecognition layers for capturing target analytes of interest.The polymer was synthesized by free radical copolymerization and coated on gold electrodes to form a thin coating (16 nm when dry), which upon hydration results in a hydrophilic interface (contact angle <15 degrees). Anti-fouling properties were validated by determining the adsorption of radiolabeled human serum albumin (HSA) protein (spiked in plasma) on polymer-coated electrodes. The polymer-coated electrodes showed a ~67% reduction in protein adsorption relative to bare gold electrodes. Additionally, no significant change in anodic current was observed when 1% HSA was incubated on polymer-coated electrodes for 1 hour; whereas an 83% decrease in anodic current was observed on bare-gold electrodes under the same conditions. The polymer-modified electrode was used in detecting redox-labeled DNA sequences with a LOD of 11 nM in buffer and unprocessed plasma. The coating was also utilized to detect COVID-19, where the prepared setup detected 104 cp/mL of SARS-CoV-2 pseudovirus spiked in 50% unprocessed saliva. Similar coatings created from poly(ethylene glycol) (PEG) were unresponsive toward SARS-CoV-2 spiked in 50% saliva [5]. The anti-fouling polymer coatings developed herein show enhanced performance compared to previously reported strategies, based on self-assembled monolayers, in detecting target analytes in complex media, demonstrating the potential for use in clinical diagnostics.

On-demand bactericidal and self-adaptive antifouling hydrogels for self-healing and lubricant coatings of catheters

Catheter-related infections are one of the most common nosocomial infections with increasing morbidity and mortality, and robust antibacterial or antifouling catheter coatings remain great challenges for long-term implantation. Herein, multifunctional hydrogel coatings were developed to provide persistent and self-adaptive antifouling and antibacterial effects with self-healing and lubricant capabilities. Polyvinyl alcohol (PVA) with β-cyclodextrin (β-CD) grafts (PVA-Cd) and 4-arm polyethylene glycol (PEG) with adamantane and quaternary ammonium compound (QAC) terminals (QA-PEG-Ad) were crosslinked through host-guest recognitions between adamantane and β-CD moieties to acquire PVEQ coatings. In response to bacterial infections, QACs exhibit reversible transformation between zwitterions (pH 7.4) and cationic lactones (pH 5.5) to generate on-demand bactericidal effect. Highly hydrophilic PEG/PVA backbones and zwitterionic QACs build a lubricate surface and decrease the friction coefficient 10 times compared with that of bare catheters. The antifouling hydrated layer significantly inhibits blood protein adsorption and platelet activation and reveals negligible hemolysis and cytotoxicity. The dynamic host-guest crosslinking achieves full self-healing of cracks in PVEQ hydrogels, and the mechanical profiles were recovered to over 90 % after rejuvenating the broken hydrogels, exhibiting a long-term stability after mechanical stretching, twisting, knotting and compression. After subcutaneous implantation and local bacterial infection, the retrieved PVEQ-coated catheters display no tissue adhesion and 3 log folds lower bacterial number than that of bare catheters. PVEQ coatings effectively prevent the repeated bacterial infections and there are few inflammatory reactions in the surrounding tissue, while substantial lymphoid infiltration and inflammatory cell aggregation occur in muscle tissues around the bare catheter. Thus, this study demonstrates a catheter coating strategy by on-demand bactericidal, self-adaptive antifouling, self-healing and lubricant hydrogels to address medical devices-related infections. Statement of significanceIt is estimated over two billion peripheral intravenous catheters are annually used in hospitals around the world, and catheter-associated infection has become a great clinical challenge with rapidly rising morbidity and mortality. Surface coating is considered a promising approach, but substantial challenges remain in the development of coatings that simultaneously satisfy both anti-fouling and antibacterial attributes. Even more, few attempts have been made to design mechanically robust coatings and reversible antibacterial or antifouling capabilities, which are critical for long-term medical implants. To address these challenges, we propose a concise strategy to develop hydrogel coatings from commercially available poly(ethylene glycol) and polyvinyl alcohol. In addition to self-healing and lubricant capabilities, the reversible conversion between zwitterionic and cationic lactones of quaternary ammonium compounds enables on-demand bactericidal and self-adaptive antifouling effects.