Anti-biofouling Activity Research Articles

Improved antifouling and antibacterial properties of forward osmosis membranes through surface modification with zwitterions and silver-based metal organic frameworks

This study investigates the effect of surface functionalization of a thin-film composite forward osmosis membrane with zwitterions and silver-based metal organic frameworks (Ag-MOFs) to improve the antifouling, anti-biofouling, and antimicrobial activity of the membrane. Two types of zwitterions, namely, 3-bromopropionic acid and 1,3-propane sultone, are chemically bonded, with and without incorporation of Ag-MOFs, over the surface of a polyamide membrane. Spectroscopy measurements indicate successful grafting of the modifying agents on the membrane surface. Contact angle measurements demonstrate a notable improvement in surface wettability upon functionalization. The performance of the membranes is evaluated in terms of water and salt fluxes in forward osmosis filtrations. The transport data show demonstrably increased water flux of around 300% compared to pristine membranes, with similar or slightly reduced salt reverse flux. The antifouling and anti-biofouling properties of the modified membranes are evaluated using sodium alginate and E. coli, respectively. These experiments reveal that functionalized membranes exhibit significant antifouling and anti-biofouling behavior, with high resilience against flux decline.

Surface functionalization of 3D printed structures: Aesthetic and antibiofouling properties

Additive manufacturing (AM) is a hot topic nowadays, having a first order in importance in research trends, improving existent technologies and carrying them further. AM can be applied to ceramics, which have importance in current technologies. Their capability to maintain functional properties for long time periods, combined with the easiness to process and the abundance of raw materials, make them a fundamental part of mankind development. Within ceramics, stoneware has a wide range of uses but in some conditions, it can be affected by biofouling. Ti(O)N and Ag-Ti(O)N coatings over 3D printed stoneware, were presented as multifunctional solution, linking aesthetical and antimicrobial properties. Films were developed by reactive direct current (DC) magnetron sputtering and characterized physical, chemical and morphologically, as well as regarding their colour variation. Moreover roughness, wettability, antibacterial and antibiofouling were also evaluated. The results revealed that the Ag doped coatings (with or without oxygen addition) had an enhanced multifunctionality compared to control samples (without Ag). Ag nanoparticles addition created a surface with potential antibacterial and antibiofouling activities, in order to resist outdoors and aqueous environments, making these films able to be applied in architectural pieces as sculptures or other decorative parts, maintaining their properties with good aesthetical properties.

Positively charged conjugated microporous polymers with antibiofouling activity for ultrafast and highly selective uranium extraction from seawater

Uranium high-efficiency separation from seawater still has some obstacles such as slow sorption rate, poor selectivity and biofouling. Herein, we report a strategy for ultrafast and highly selective uranium extraction from seawater by positively charged conjugated microporous polymers (CMPs). The polymers are synthesized by Sonogashira-Hagihara cross-coupling reaction of 1,3-dibromo-5,5-dimethylhydantoin and 1,3,5-triethynylbenzene, and then modified with oxime and carboxyl via click reaction. The CMPs show an ultrafast sorption (0.46 mg g−1 day−1) for uranium, and possess an outstanding selectivity with a high sorption capacity ratio of U/V (8.4) in real seawater. The study of adsorption process and mechanism indicate that the CMPs skeleton exhibits high affinity for uranium and can accelerate the sorption, and uranium(VI) is adsorbed on the materials by the interaction of oxime/carboxyl ligands and hydantoin. Moreover, the material can be simply loaded onto the filter membrane, and shows remarkable antibiofouling properties against E. coli and S. aureus and excellent uptake capacity for uranium with low concentration in real seawater. This work may provide a promising approach to design adsorbents with fast adsorption rate, high selectivity and antibacterial activity, and expand the thinking over the development of novel and highly efficient adsorbents for uranium extraction from seawater.

Antibiofouling potential of 1-alkyl-3-methylimidazolium ionic liquids: Studies against biofouling barnacle larvae

Development of novel and environmental-friendly antifouling compounds is desirable due to the ban on use of tributyltin and concerns on copper and co-biocides. In the current study, antimacrofouling effects of alkylimidazolium ionic liquids on Amphibalanus (=Balanus) reticulatus, a dominant fouling barnacle were assessed. The effect of three alkylimidazolium ionic liquids ([CnMIM]+[X]−, n = 4, 12 and 16) on survival, metamorphosis and settlement of barnacle larvae (nauplii and cypris) was determined in laboratory bioassays. Among the tested ionic liquids, [C12MIM][I] exhibited superior antibiofouling activity with a cypris mortality (LC50) and settlement inhibition (EC50) concentrations of 0.35 μM and 0.39 nM, respectively. [C16MIM][Cl] showed moderate activity with LC50 and EC50 values of 0.63 μM and 1.56 nM, respectively. However, [C4MIM][Cl] exhibited lowest activity on survival and settlement with LC50 and EC50 values of 2.28 μM and 80.2 nM, respectively. The anion (Cl− or I−) did not contribute to the biological activity of ionic liquids. Antifouling activity of the tested ionic liquids on larvae decreased in the following order: [C12MIM][I] > [C16MIM][Cl] > [C4MIM][Cl]. Therapeutic ratios (TR = LC50/EC50) of the tested compounds at >28 to 900 were found to be much higher than the reference value (>15) qualifying them as promising non-toxic or environmentally benign antifoulants. Tested ionic liquids exhibited activity in the similar order ([C12MIM][I] > [C16MIM][Cl] > [C4MIM][Cl]) on survival and metamorphosis of nauplius larvae. EC50 and LC50 concentrations of all the three compounds had no lethal effect on non-target organism, Artemia salina. These data presents possibilities for designing effective and environmental friendly antifouling strategies.

Photoinduced Multiple Effects to Enhance Uranium Extraction from Natural Seawater by Black Phosphorus Nanosheets.

Based on the photoinduced photothermal, photoelectric, and photocatalytic effects of black phosphorus (BP) nanosheets, a BP-PAO fiber with enhanced uranium extraction capacity and high antibiofouling activity is fabricated by compositing BP nanosheets into polyacrylamidoxime (PAO). The photothermal effect increases the coordination interaction between UO2 2+ and the functional amidoxime group, and the photoelectric effect produces the surface positive electric field that exhibits electrostatic attraction to the negative [UO2 (CO3 )3 ]4- , which all increase the capacity for uranium adsorption. The photocatalytic effect endows the adsorbent with high antibiofouling activity by producing biotoxic reactive oxygen species. Owing to these three photoinduced effects, the photoinduced BP-PAO fiber shows a high uranium adsorption capacity of 11.76 mg g-1 , which is 1.50 times of the PAO fiber, in bacteria-containing natural seawater.

Photoinduced Multiple Effects to Enhance Uranium Extraction from Natural Seawater by Black Phosphorus Nanosheets

AbstractBased on the photoinduced photothermal, photoelectric, and photocatalytic effects of black phosphorus (BP) nanosheets, a BP‐PAO fiber with enhanced uranium extraction capacity and high antibiofouling activity is fabricated by compositing BP nanosheets into polyacrylamidoxime (PAO). The photothermal effect increases the coordination interaction between UO22+ and the functional amidoxime group, and the photoelectric effect produces the surface positive electric field that exhibits electrostatic attraction to the negative [UO2(CO3)3]4−, which all increase the capacity for uranium adsorption. The photocatalytic effect endows the adsorbent with high antibiofouling activity by producing biotoxic reactive oxygen species. Owing to these three photoinduced effects, the photoinduced BP‐PAO fiber shows a high uranium adsorption capacity of 11.76 mg g−1, which is 1.50 times of the PAO fiber, in bacteria‐containing natural seawater.

Lysine and α-Aminoisobutyric Acid Conjugated Bioinspired Polydopamine Surfaces for the Enhanced Antibacterial Performance of the Foley Catheter.

Microbial adhesion onto implanted devices was reduced by the immobilization of amino acid lysine and α-aminoisobutyric acid to polydopamine functionalized PET films and Foley catheters. The polydopamine functionalized film was prepared by a dip coating method followed by incorporation of biocompatible amino acids to prepared films. The purpose of development of the modified pDA film is to improve the anti-biofouling and antibacterial activity of the film which can be successfully applied for medical devices. The characterization of modification was done using different techniques such as contact angle measurement, ATR-FTIR, FE-SEM, AFM, and XPS analysis. ATR-FTIR spectroscopy and XPS confirmed the successful amino modification of film. The anti-biofouling and antimicrobial behavior of the prepared surfaces were evaluated using the bacterial attachment and death assay. The resulting coatings repelled bacterial cell attachment and killed clinically applicable Gram-negative and Gram-positive strains. The developed coatings were applied to the Foley catheters to study the antibacterial activity by the log reduction method. The results demonstrate that tested amino acid-modified film increases the antibacterial activity of the catheters and can significantly help in reduction of nosocomial infections.

Alternative Pathogen Control Chemistry of Glass Fiber-Reinforced Polyester Panels for Cooling Towers

This study aimed to investigate the antibiofouling activity of 3-(trimethoxysilyl)-propyl, alkyldimethylammonium chloride-based (SilQUAT)-treated glass fiber-reinforced polyester (GFRP) composite panels in model cooling tower system. All surface characterization analyses were performed by using FTIR and XPS and showed that surface chemical composition peaks confirmed the successful coating of compound. The antibiofilm efficacy of the SilQUAT-treated GFRP panels was evaluated with culture, ATP measurement and live/dead fluorescence staining, for 6 months. To mimic mechanical interventions, the durability and residual self-sanitizing activity of the treated GFRP panels was tested by modifying the EPA # 01-1A protocol, after abrasion. At the end of the 6-month period, the antibacterial effect was 95% and 99.90% for abraded and non-abraded materials, respectively. The current study provides an alternative application to prevent biofilm at source by modification and imparting antibacterial properties to the material. Prevention of biofilm at its source is an important approach by providing indirect benefits such as the reduction in corrosion and secondary environmental pollution caused by the use of excess biocides, and consequently, the reduction in cost and the risk of harm to the public/environment will also be of interest.

Zn Wetted CeO2 Based Composite Galvanization: An Effective Route To Combat Biofouling.

The present paper reports for the first time the development and application of novel Zn wetted CeO2 (Zn/CeO2) composite galvanic zinc coating to combat microbial induced corrosion (MIC). Zinc metal-metal interaction causes the effective incorporation of composite into the galvanic coating and accordingly increases the active sites for antibiofouling activity. The developed coatings are explored for their anticorrosion/antibiofouling characteristics toward MIC induced by cultured seawater consortia. Enhanced antibiofouling activity of the composite galvanic coating is achieved due to the tuned content of 28 wt % Zn and 34 wt % of Ce. High charge transfer resistance as high as 4.0 × 1014 Ω cm2 and low double layer capacitance as low as 3.99 × 10-8 F are achieved by tuning the structure and composition of the coating. The synergistic effect of Zn and Ce ensures the stability and corrosion resistance of the coatings in a corrosive bacterial environment. Evident decreases in the bacterial attachment and biofilm formation are illustrated using antibiofouling assay. The antibiofouling activity is attributed to the effective reduction of Ce4+ to Ce3+ and the shuttling characteristics of oxidation state of CeO2. This impairs the cellular respiration and results in bacterial death. Thus, it can be used as an effective coating to protect the steel based equipment in corrosive marine environments to combat marine microorganisms and their interactions. The present study also paves the scope for exploration of similar effective protective systems.

Ultrafast Recovery of Uranium from Seawater by Bacillus velezensis Strain UUS-1 with Innate Anti-Biofouling Activity.

Highly‐efficient recovery of uranium from seawater is of great concern in the growing demand for nuclear energy. Bacteria are thought to be potential alternatives for uranium recovery. Herein, a Bacillus velezensis strain, UUS‐1, with highly‐efficient uranium immobilization capacity is isolated and is used in the recovery of uranium from seawater. The strain exhibits time‐dependent uranium recovery capacity and only immobilizes uranium after growing for 12 h. The carboxyl group together with the amino group inside the bacterial cells, but not previously identified phosphate group, are essential for uranium immobilization. UUS‐1 shows broad‐spectrum antimicrobial activity by producing diverse antimicrobial metabolites, which endows the strain with innate resistance to the biofouling of marine microorganisms. Based on the dry weight of the initially used bacterial cultures, UUS‐1 concentrates uranium by 6.26 × 105 times and reaches the high immobilization capacity of 9.46 ± 0.39 mg U g−1 bacterial cultures in real seawater within 48 h, which is the fastest uranium immobilization capacity observed from real seawater. Overall considering the ultrafast and highly‐efficient uranium recovery capacity and the innate anti‐biofouling activity, UUS‐1 is a promising alternative for uranium recovery from seawater.

Bioelectrochemical recovery of silver from wastewater with sustainable power generation and its reuse for biofouling mitigation

Precious metals recovery and wastewater treatment using the microbial fuel cell (MFC) is an attractive approach for a sustainable environment. Silver recovery from wastewater and its valorization in the form of silver nanoflakes (AgNFs) brings back waste material to production stream and helps in transition from linear to circular economy. In the present study, bioelectrochemical performance of MFC fed with silver laden artificial wastewater (MFC-Ag) was compared with MFC fed with potassium ferricyanide (MFC-FC) and MFC fed with phosphate buffer as catholyte (MFC-blank). High silver removal (83 ± 0.7%) and recovery (67.8 ± 1%) efficiencies were achieved from MFC-Ag after 72 h operation. The maximum power density (3006 mW/m3) and current density (34100 mA/m3) of MFC-Ag were found to be significantly higher than the MFC-FC and MFC-blank. High chemical oxygen demand (COD) removal efficiency of MFC-Ag (82.7 ± 1.5%) compared with MFC-FC (76 ± 2) highlighted the suitability of silver laden wastewater as a cost effective catholyte. The high coulombic efficiency (8.73 ± 0.9%) and low solution resistance (24.38 Ω) for MFC-Ag also indicate the potential of silver laden wastewater for large scale applications. Analytical characterizations of electrochemically recovered silver revealed the pure (99%) and crystalline AgNFs with a mean diameter of 18 ± 1.2 nm on the cathode surface. Furthermore, a significant anti-biofouling activity of recovered AgNFs indicate the valorization of waste by current study with potential applications in several industrial and environmental processes. Our method has diverse potential to scale up the MFC technology for industrial waste management as a closed loop process with minimum facilities and higher sustainability.

Achieving high bactericidal and antibiofouling activities of 2D titanium carbide (Ti3C2Tx) by delamination and intercalation

The development of extrinsic antibacterial agents using newly identified nanoscale 2D layered transition metal carbide (MXene) was established by different delamination and intercalation approaches to explore structure-bioproperty relations. Herein, we report the potential impact of the microbial inactivation of Escherichia coli (E. coli) by delaminating (water, dimethyl sulfoxide (DMSO), and isopropylamine) and intercalating (hydrazine monohydrate (HMH), sodium hydroxide, and potassium hydroxide) of MXene (Ti3C2Tx), and its bactericidal mechanism was interpreted. The delaminations and intercalations all significantly increased the colloidal stability and bactericidal effect of Ti3C2Tx suspensions via unpacking of stacked MXene layers, among which the HMH intercalation showed the best performance. Our experimental results reveal that the mechanism of bacterial killing was primarily because of surface wrapping followed by extracellular reactive oxygen species independent oxidative stress. This study also shows that the stacked layer separation along with the surface moiety is an essential and decisive factor that determines the lethal bacterial potency of Ti3C2Tx. The application of Ti3C2Tx-coated polyvinylidene fluoride (PVDF) membranes effectively inactivates E. coli; importantly, it prevents biofilm formation on the active membrane surfaces and thus has high potential for antibiofouling. This study provides useful guidelines for the future development of Ti3C2Tx-based antimicrobial surface coatings and increases their bioapplication potential.

Brush Swelling and Attachment Strength of Barnacle Adhesion Protein on Zwitterionic Polymer Films as a Function of Macromolecular Structure.

The exceptional hydration of sulfobetaine polymer brushes and their resistance toward nonspecific protein absorption allows for the construction of thin films with excellent antibiofouling properties. In this work, swollen sulfobetaine brushes, prepared by surface-initiated atom transfer radical polymerization of two monomers, differentiated by the nature of the polymerizable group, are studied and compared by a liquid-cell atomic force microscopy technique and spectroscopic ellipsometry. Colloidal AFM-based force spectroscopy is employed to estimate brush grafting density and characterize nanomechanical properties in salt water. When the ionic strength-induced swelling behaviors of the two systems are compared, the differences observed on the antipolyelectrolyte response can be correlated with the stiffness variation on brush compression, likely to be promoted by solvation differences. The higher solvation of amide groups is proposed to be responsible for the lower adhesion force of the barnacle cyprid’s temporary adhesive proteins. The adhesion results provide further insights into the antibiofouling activity against barnacle cyprid settlement attributed to polysulfobetaine brushes.

Synthesis of dual-functionalized poly(vinyl alcohol)/poly(acrylic acid) electrospun nanofibers with enzyme and copper ion for enhancing anti-biofouling activities

The aim of this study was to synthesize dual-functionalized poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA) electrospun nanofibers with enzyme and copper ion (Cu(II)) for enhancing anti-biofouling activities. The PVA/PAA nanofibers were successfully synthesized by co-electrospinning (voltage = 17 kV; tip-to-collector distance = 15 cm) and cross-linked by heat treatment. The PVA/PAA nanofibers were functionalized through adsorbing Cu(II) onto the nanofibers to prepare the PVA/PAA-Cu(II) nanofibers. Three proteases (proteinase K, trypsin, and α-chymotrypsin) and a quorum quenching enzyme (acylase I) were tested for biofilm reduction that α-chymotrypsin effectively inhibited the biofilm formation and removed biofilms of Pseudomonas aeruginosa and Staphylococcus aureus. The PVA/PAA nanofibers were dual-functionalized with α-chymotrypsin and Cu(II) to obtain PVA/PAA-Cu(II)-α nanofibers. Degradation tests for extracellular polymeric substances (EPS) extracted from P. aeruginosa indicated that the PVA/PAA-Cu(II)-α nanofibers could degrade the EPS proteins up to 0.26 mg mL−1 for 300 min, which was higher than that of free α-chymotrypsin. For anti-biofouling tests, the log number of planktonic and sessile cells of P. aeruginosa was the lowest in the PVA/PAA-Cu(II)-α nanofibers. The anti-biofouling activities of the PVA/PAA-Cu(II)-α nanofibers could be attributed to the effects of both Cu(II) (killing planktonic and sessile cells) and α-chymotrypsin (degrading the EPS protein in biofilm).

Novel chitosan based thin sheet nanofiltration membrane for rejection of heavy metal chromium.

In recent years, polymeric membranes holds superior position in filtration processes as it was cost effective and simple to prepare. In the present study we have synthesized a novel organic-inorganic hybrid thin sheet membrane using chitosan/polyvinyl alcohol and montmorillonite clay followed by non-solvent induced phase inversion technique. This hybrid clay-polymeric nanofiltration membrane possesses excellent overall performance, such as enhanced hydrophilic nature, and holds good rejection rate. Analytical techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and Scanning Electron Microscopy (SEM) have been employed to characterize the membrane material. Membrane characterizations such as pure water flux, membrane hydraulic resistance, water content, percentage of porosity and pore size were also evaluated. An important characteristic of membrane for long term usage "anti-biofouling activity" is investigated by determining zone of inhibition of membrane on pathogens of bacterial and fungal strains. The remediation of chromium was performed by varying the parameters such as pH, metal ion concentration, applied pressure and thickness of membrane. The rejection of chromium removal by CS/PVA/MMT membrane is confirmed by comparing the spectral images of EDAX and FT-IR taken before and after filtration.

Anti-biofouling activity of Ranaspumin-2 bio-surfactant immobilized on catechol-functional PMMA thin layers prepared by atmospheric plasma deposition.

The deposition of polymeric thin layers bearing reactive functional groups is a promising solution to provide functionality on otherwise inert surfaces, for instance, for bioconjugation purposes. Atmospheric pressure plasma (AP plasma) deposition technology offers many advantages, such as fast deposition rates, low costs, low waste generation and suitability for coating various kind of material surfaces. In this work, the AP plasma-assisted copolymerization of methyl methacrylate (MMA) with a vinyl derivative of L-DOPA was studied in order to deposit coatings with reactive catechol/quinone groups suitable for protein covalent immobilization. The effect of adding a chemical cross-linker, between 0 and 2 mol%, to the monomer mixture is also studied in order to prepare robust plasma PMMA-based layers in liquid physiological media. The layer prepared with 0.2 mol% of cross-linker shows the best balance between stability in saline-buffered media and surface functionalization. Bioconjugation via the grafting of Ranaspumin-2 recombinant, a naturally occurring surfactant protein, is carried out in a single step after plasma deposition. Protein immobilization is corroborated by Quartz Crystal Microbalance with Dissipation (QCM-D) and Surface Plasmon Resonance (SPR) analyses and confirmed via Epicocconone staining, X-Ray Photoemission Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurements and surface wettability characterizations. The bio-functionalized layers presented an enhanced activity against the adhesion of Human Serum Albumin (HSA), indicating the grafting potential of the Ranaspumin-2 bio-surfactant to produce anti-biofouling functional coatings.

Modification of a polypropylene feed spacer with metal oxide-thin film by chemical bath deposition for biofouling control in membrane filtration

Surface modification of polypropylene feed spacers typical of spiral wound membrane modules was studied by generation of crystalline ZnO nanorods. A seeding layer made by deposition of ZnO nanoparticles (20–40–60 nm diameter) from aqueous dispersions served as nucleation centers for crystallization. A uniform layer of ZnO nanorods was grown on the seeding layer by chemical bath deposition from a zinc acetate solution. Biocidal activity was estimated by antibacterial tests in static liquid culture against Escherichia coli and antibiofouling tests in flow-through/cross-flow mode against a mixture of Pseudomonas fluorescens and Bacillus subtilis. Best biocidal activity was displayed by 20 nm ZnO particles, suggesting a tradeoff between surface coverage, roughness and particle size. Although the seed layer itself displayed acceptable antibacterial activity, a marked improvement was achieved by the nanorods, proving that the morphology of the deposition layer was involved in the antibacterial mechanism. Antibiofouling activity was further improved by superhydrophobic over-coating of the nanorods with octadecyl-phosphonic acid. Modified spacers reduced permeate flux decay by at least 40% compared to controls. The enhanced antibiofouling activity of crystalline ZnO nanorods, compared with amorphous ZnO nanoparticles, can be explained by a combination of the abrasive surface of the crystalline nanorods, hydrophobic repulsion and cumulative oxidation.

Antibacterial and Antibiofouling Properties of Light Triggered Fluorescent Hydrophobic Carbon Quantum Dots Langmuir–Blodgett Thin Films

Inimitable properties of carbon quantum dots as well as a cheap production contribute to their possible application in biomedicine especially as antibacterial and antibiofouling coatings. Fluorescent hydrophobic carbon quantum dots are synthesized by bottom-up condensation method and used for deposition of uniform and homogeneous Langmuir–Blodgett thin films on different substrates. It is found that this kind of quantum dots generates singlet oxygen under blue light irradiation. Antibacterial and antibiofouling testing on four different bacteria strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa) reveals enhanced antibacterial and antibiofouling activity of hydrophobic carbon dots thin films under blue light irradiation. Moreover, hydrophobic quantum dots show noncytotoxic effect on mouse fibroblast cell line. These properties enable potential usage of hydrophobic carbon quantum dots thin films as excellent antibacterial and antibiofouling coatings for different ...

Preparation and Characterization of an Antifouling Polyethersulfone Nanofiltration Membrane Blended with Graphene Oxide/Ag Nanoparticles

Graphene oxide/Ag nanoparticles (Ag/GO) was prepared and employed to synthesize antifouling polyethersulfone (PES) mixed matrix membranes. The performance of the membranes was evaluated in terms of flux, hydrophilicity and anti-biofouling properties. With increment of the Ag/GO from 0 to 0.1 wt.%, the pure water flux increased from 24.7 up to 54.1 kg/m2 h. The flux recovery ratio (FRR) of the membranes was performed using milk powder solution and the results illustrated that the 0.1 wt.% Ag/GO membrane had the best fouling resistance with the FRR value of 95.45%. The performance of the nanofiltration was assessed using the retention of Direct Red 16. It was indicated that the Ag/GO-PES membranes have remarkable dye removal (98.38% rejection). The anti-biofouling activities of the 0.1 wt.% Ag/GO mixed matrix membrane was also investigated using activated sludge and the results showed a notable improvement.

Electroactive Polyhydroquinone Coatings for Marine Fouling Prevention-A Rejected Dynamic pH Hypothesis and a Deceiving Artifact in Electrochemical Antifouling Testing.

Nanometer-thin coatings of polyhydroquinone (PHQ), which release and absorb protons upon oxidation and reduction, respectively, were tested for electrochemically induced anti-biofouling activity under the hypothesis that a dynamic pH environment would discourage fouling. Antifouling tests in artificial seawater using the marine, biofilm-forming bacterium Vibrio alginolyticus proved the coatings to be ineffective in fouling prevention but revealed a deceiving artifact from the reactive species generated at the counter electrode (CE), even for electrochemical bias potentials as low as |400| mV versus Ag|AgCl. These findings provide valuable information on the preparation of nanothin PHQ coatings and their electrochemical behavior in artificial seawater. The results further demonstrate that it is critical to isolate the CE in electrochemical anti-biofouling testing.