Bridging aquatic invasive species threats across multiple sectors through One Biosecurity.

Understanding the magnitude of biosecurity risks in aquatic environments is increasingly complex and urgent because increasing volumes of international shipping, rising demand for aquaculture products, and growth in the global aquarium trade, are accelerating invasive alien species spread worldwide. These threats are especially pressing amid climate and biodiversity crises. However, global and national biosecurity systems are poorly prepared to respond because of fragmented research and policy environments, that often fail to account for risks across sectors or across stakeholder needs and fail to recognize similarities in the processes underpinning biological invasions. In the present article, we illustrate the complex network of links between biosecurity threats across human, animal, plant, and environment sectors and propose a universal approach to risk assessment. One Biosecurity is a holistic, interdisciplinary approach that minimizes biosecurity risks across human, animal, plant, algal, and ecosystem health and is critical to reduce redundancy and increase cross-sectoral cohesion to improve policy, management, and research in aquatic biosecurity.

Novel metabolite madeirone and neomarinone extracted from Streptomyces aculeoletus as marine antibiofilm and antifouling agents.

Introduction: Biofouling poses a significant economic threat to various marine industries, leading to financial losses that can reach billions of euros annually. This study highlights the urgent need for effective alternatives to traditional antifouling agents, particularly following the global ban on organotin compounds. Material and methods: Streptomyces aculeolatus PTM-346 was isolated from sediment samples on the shores of the Madeira Archipelago, Portugal. The crude extract was fractionated using silica flash chromatography and preparative HPLC, resulting in two isolated marinone compounds: madeirone (1), a novel marinone derivative discovered in this study, and neomarinone (2). The antifouling activities of these compounds were tested against five marine bacterial species and the larvae of the mussel Mytilus galloprovincialis. Additionally, in silico and in vivo environmental toxicity evaluations of madeirone (1) and neomarinone (2) were conducted. Results: Madeirone (1) demonstrated significant antibiofilm efficacy, inhibiting Phaeobacter inhibens by up to 66%, Marinobacter hydrocarbonoclasticus by up to 60%, and Cobetia marina by up to 40%. Neomarinone (2) also exhibited substantial antibiofilm activity, with inhibition rates of up to 41% against P. inhibens, 40% against Pseudo-oceanicola batsensis, 56% against M. hydrocarbonoclasticus, 46% against C. marina, and 40% against Micrococcus luteus. The growth inhibition activity at the same concentrations of these compounds remained below 20% for the respective bacteria, highlighting their effectiveness as potent antibiofilm agents without significantly affecting bacterial viability. Additionally, both compounds showed potent effects against the settlement of Mytilus galloprovincialis larvae, with EC50 values of 1.76 µg/mL and 0.12 µg/mL for compounds (1) and (2), respectively, without impairing the viability of the targeted macrofouling species. In silico toxicity predictions and in vivo toxicity assays both support their potential for further development as antifouling agents. Conclusion: The newly discovered metabolite madeirone (1) and neomarinone (2) effectively inhibit both micro- and macrofouling. This distinct capability sets them apart from existing commercial antifouling agents and positions them as promising candidates for biofouling prevention. Consequently, these compounds represent a viable and environmentally friendly alternative for incorporation into paints, primers, varnishes, and sealants, offering significant advantages over traditional copper-based compounds.

On-site evaluation of DGT passive sampling for quantitatively measuring per- and polyfluoroalkyl substances in a river-estuary-sea water system.

The passive sampling technique of diffusive gradients in thin-films (DGT) is promising for monitoring emerging contaminants such as per- and polyfluoroalkyl substances (PFAS). It is urgent to evaluate the impacts of salinity and exposure time on DGT sampling before it can be set as a standard method. Herein, DGT sampler based on the binding gel of weak anion exchanger (WAX) resin was deployed in a representative water system of the Xiaoqing river-estuary-sea for representative sampling windows (<1 day to 28 days) with high pH (8.18 ± 0.04 to 8.51 ± 0.17) and wide ranges of salinity (0.95 ± 0.07‰ to 14.37 ± 3.92‰), total dissolved solids (1.20 ± 0.09 g/L to 15.29 ± 3.91 g/L) and dissolved organic matter (2.8-32 mg/L). The results showed that the WAX-DGT sampler exhibited good performance for most target PFAS except for short-chain perfluorocarboxylates (C ≤ 5) in 14 days. When the exposure time was over 14 days, biofouling of the sampler may deflect the mass accumulation of the PFAS in the sampler. Salinity played an important role in the mass binding of PFAS by DGT. The shorter the carbon chain of the compound, the greater the influence of the salinity. PFAS with carboxyl groups had greater affinities for the biofouled membrane filter than those with sulfonic groups. In the river-estuary-sea system, where PFAS concentrations changed dynamically, the temporal resolution of the monitoring strategy has been demonstrated to be more important than spatial resolution. DGT provided a better integral of PFAS exposure than grab sampling in the dynamic water system and offered equivalent sensitivity of grab sampling with exposure time <10 d and greater sensitivity with exposure time ≥10 d. Thus, DGT has the advantage of providing high temporal resolution monitoring. This study provided support for the standardization of the DGT technique.

Modelling passive sampling of hydrophilic compounds under time-variable aqueous concentrations.

Passive sampling is a crucial method for evaluating concentrations of hydrophilic organic compounds in the aquatic environment, but it is insufficiently understood to what extent passive samplers capture the intermittent emissions that frequently occur for this group of compounds. In the present study, silicone sheets and styrene-divinyl benzene-reversed phase sulfonated extraction disks with and without a polyethersulfone membrane were exposed under semi-field conditions in a 31 m3 flume at three different flow velocities. Natural processes and spiking/dilution measures caused aqueous concentrations to vary strongly with time. The data were analyzed using two analytical models that account for these time-variable concentrations: a sampling rate model and a diffusion model. The diffusion model generally gave a better fit of the data than the sampling rate model, but the difference in residual errors was quite small (median errors of 19 vs. 25% for silicone and 22 vs. 25% for SDB-RPS samplers). The sampling rate model was therefore adequate enough to evaluate the time-integrative capabilities of the samplers. Sampler performance was best for SDB-RPS samplers with a polyethersulfone membrane, despite the occurrence of lag times for some compounds (0.1 to 0.4 days). Sampling rates for this design also spanned a narrower range (80 to 110 mL/day) than SDB-RPS samplers without a membrane (100 to 660 mL/day). The effect of biofouling was similar for all compounds and was consistent with a biofouling layer thickness of 150 µm.

Assessment of plastic debris and biofouling in a specially protected area of the Antarctic Peninsula region.

The aim of this paper is to characterize the plastic and to study a potential relationship between plastic debris characteristics and the presence of fouling biota in an Antarctic Specially Protected Area Robert Island, on the Antarctic peninsula region. A combination of lab-based sorting, advanced spectral analysis and general linear modelling was used to assess the abundance and type of plastic debris washed up on the shore. Observations recorded 730 debris items, with 85 % being plastic. Polystyrene (PS) and Polyethylene terephthalate (PET) were the dominant plastics (61 %). Biofouling was observed on 25 % of plastic debris, with debris complexity and degradation significantly increasing the likelihood of fouling occurring. There was no correlation found between biofouling type and plastic polymer type. Findings raise concerns that even with the highest level of environmental protection, an external marine-based source of pollution can intrude the coastal habitat, with uncertain consequences to local flora and fauna.

Bioinspired Sulfobetaine Borneol Fluorinated Amphiphilic Polymers for Marine Antifouling and Fouling Release Applications.

The development of nontoxic antifouling coatings in static marine environments is urgent. Herein, the successful synthesis of sulfobetaine borneol fluorinated polymers (PEASBF) by a free radical polymerization method is reported. The PEASBF coatings exhibit outstanding antifouling activity, which effectively resists the adhesion of Bovine serum albumin (FITC-BSA adhesion rate: 0.5%), Pseudomonas sp. (Biofilm: 1.3 absorbance) and Navicula sp. (Diatom attachment rate: 33%). More importantly, the PEASBF coatings display outstanding fouling release properties, achieving a release rate of 98% for Navicula sp., and the absorbance of the Pseudomonas sp. biofilm is only 0.2 under 10 Pa shear stress. XPS and MD studies showed that the fluorinated/isobornyl groups induce more sulfobetaine groups to migrate toward polymer surfaces for intensify antifouling. Additionally, the chiral stereochemical structure of borneol enhances antifouling and fouling release ability of amphiphilic polymers. Therefore, the PEASBF has the potential for static marine antifouling applications.

Oceanic realistic application of a microplastic biofouling model to the river discharge case.

Marine biofouling is considered one of the major biophysical processes influencing the vertical dynamics of plastic debris in seawater. We numerically implement, for the first time, this mechanism within a fine-resolution, regional model of the Tyrrhenian Sea, in order to simulate the dispersion of microplastics (MPs) released at the mouth of a highly polluting river. Four polymers and three particle sizes are used to quantify algal concentration influence on the trajectories, fates, and accumulation spots of the tracked MPs, by comparing 2002 winter and summer runs encompassing or not biofouling. Besides a marked seasonality for most of the MP types and radii tested, biofouling effects are prominently observed for only 2 polymers and particles bigger than 1µm. Thus, further realistic applications of the biofouling mechanism in oceanic circulation models are required to achieve a thorough assessment of its impact on plastic density within distinctive basins of the world seas.

Understanding the flow behavior around marine biofilms.

In vitro platforms capable of mimicking the hydrodynamic conditions prevailing in natural aquatic environments have been previously validated and used to predict the fouling behavior on different surfaces. Computational Fluid Dynamics (CFD) has been used to predict the shear forces occurring in these platforms. In general, these predictions are made for the initial stages of biofilm formation, where the amount of biofilm does not affect the flow behavior, enabling the estimation of the shear forces that initial adhering organisms have to withstand. In this work, we go a step further in understanding the flow behavior when a mature biofilm is present in such platforms to better understand the shear rate distribution affecting marine biofilms. Using 3D images obtained by Optical Coherence Tomography, a mesh was produced and used in CFD simulations. Biofilms of two different marine cyanobacteria were developed in agitated microtiter plates incubated at two different shaking frequencies for 7 weeks. The biofilm-flow interactions were characterized in terms of the velocity field and shear rate distribution. Results show that global hydrodynamics imposed by the different shaking frequencies affect biofilm architecture and also that this architecture affects local hydrodynamics, causing a large heterogeneity in the shear rate field. Biofilm cells located in the streamers of the biofilm are subjected to much higher shear values than those located on the bottom of the streamers and this dispersion in shear rate values increases at lower bulk fluid velocities. This heterogeneity in the shear force field may be a contributing factor for the heterogeneous behavior in metabolic activity, growth status, gene expression pattern, and antibiotic resistance often associated with nutrient availability within the biofilm.

Durable, Photostable Omniphobic Synthetic Leather Surfaces with Anti-Biofouling Properties for Hygienic Applications.

Globally, the public health domain is increasingly emphasizing the need for surfaces that can resist bacterial contamination, as the consumption of bacteria-infected substance may cause illnesses. Thus, this study aimed to modify polyurethane (PU) synthetic leather surfaces by coating their upper layer with fluorine-functionalized nano-silica particles (FNPs). This simple modification imparted omniphobic characteristics, realizing anti-biofouling and self-cleaning properties. The effectiveness in preventing bacterial adhesion was confirmed by the dip-inoculation method using Escherichia coli O157:H7 and Staphylococcus epidermidis. Bacterial adhesion was evaluated based on bacterial counts using the pour plate method and by directly enumerating from scanning electron microscopy images. The attachment of bacteria to the modified omniphobic FNPs-coated PU leather surface decreased by over 98.2% compared to that on the bare surface. We expect that the method developed in this study will significantly reduce or even eliminate the potential risks associated with various biological cross-contamination scenarios, thereby enhancing hygiene standards.

Proof of Concept of Natural and Synthetic Antifouling Agents in Coatings.

Marine biofouling, caused by the deposition and accumulation of marine organisms on submerged surfaces, represents a huge concern for the maritime industries and also contributes to environmental pollution and health concerns. The most effective way to prevent this phenomenon is the use of biocide-based coatings which have proven to cause serious damage to marine ecosystems. Several research groups have focused on the search for new environmentally friendly antifoulants, including marine and terrestrial natural products and synthetic analogues. Some of these compounds have been incorporated into marine coatings and display interesting antifouling activities caused by the interference with the biofilm-forming species as well as by the inhibition of the settlement of macroorganisms. This review highlights the proof-of-concept studies of emerging natural or synthetic antifouling compounds in coatings, from lab-made to commercial ones, performed between 2019 and 2023 and their results in the field or in in vivo laboratorial tests.

Application of Natural Antibacterial Plants in the Extraction of Uranium from Seawater.

Marine biofouling directly affects the performance and efficiency of uranium (U(VI)) extraction from seawater. Compared to traditional chemical methods, natural plant extracts are generally biodegradable and nontoxic, making them an environmentally friendly alternative to synthetic chemicals in solving the marine biofouling problem. The effectiveness of natural antibacterial plants (i.e., pine needle, peppermint, Acorus gramineus Soland, Cacumen platycladi, and wormwood) in solving the marine biofouling problem was evaluated in this work. Experimental results showed that natural antibacterial plants could kill Vibrio alginolyticus in solution and effectively solve the marine biofouling problem of U(VI) extraction. To improve the adsorption capacity of natural plants for U(VI) in seawater, poly(vinylphosphonic acid) (PVPA) was modified on natural antibacterial plant surfaces by irradiation grafting technology. PVPA and natural antibacterial plants work as active sites and base materials for the U(VI) extraction material, respectively. The recovery performance of PVPA/pine needle for U(VI) was preliminarily studied. Results show that the adsorption of U(VI) on PVPA/pine needle follows pseudo-second-order and Langmuir models, and the maximum adsorption capacity is 111 mg/g at 298 K and pH 8.2.

Seasonality of mercury and its fractions in microplastics biofilms -comparison to natural biofilms, suspended particulate matter and bottom sediment.

Biofilms can enhance the sorption of heavy metals onto microplastic (MP) surfaces. However, most research in this field relies on laboratory experiments and neglects metal fractions and seasonal variations. Further studies of the metal/biofilm interaction in the aquatic environment are essential for assessing the ecological threat that MPs pose. The present study used in situ experiments in an environment conducive to biofouling (Vistula Lagoon, Baltic Sea). The objective was to investigate the sorption of mercury and its fractions (thermodesorption technique) in MP (polypropylene-PP, polystyrene-PS, polylactide-PLA) biofilms and natural matrices across three seasons. After one month of incubation, the Hg concentrations in MP and natural substratum (gravel grains-G) biofilms were similar (MP: 145 ± 45 ng/g d.w.; G: 132 ± 23 ng/g d.w.) and approximately twofold those of suspended particulate matter (SPM) (63 ± 27 ng/g d.w.). Hg concentrations in biofilms and sediments were similar, but labile fractions dominated in biofilms and stable fractions in sediments. Seasonal Hg concentrations in MP biofilms decreased over summer>winter>spring, with significant variation for mineral and loosely bound Hg fractions. Multiple regression analysis revealed that hydrochemical conditions and sediment resuspension played a crucial role in the observed variability. The influence of polymer type and morphology (pellets, fibres, aged MP) on Hg sorption in biofilms was visible only in high summer temperatures. In this season, PP fibres and aged PP pellets encouraged biofilm growth and the accumulation of labile Hg fractions. Additionally, high concentrations of mineral (stable and semi-labile) Hg fractions were found in expanded PS biofilms. These findings suggest that organisms that ingest MPs or feed on the biofilms are exposed to the adverse effects of Hg and the presence of MPs in aquatic ecosystems may facilitate the transfer of mercury within the food chain.

Enzymatically stable, non-cell adhesive, implantable polypyrrole/thiolated hyaluronic acid bioelectrodes for in vivo signal recording.

Implantable bioelectrodes have attracted significant attention for precise in vivo signal transduction with living systems. Conductive polymers, including polypyrrole (PPy), have been widely used as bioelectrodes due to their large surface areas, high charge injections, and versatilities for modification. Especially, several natural biopolymers, such as hyaluronic acid (HA), can be incorporated into conductive polymers to produce biomimetic electrodes with better biocompatibility. However, HA-incorporated PPy electrodes (PPy/HA) frequently lose their original performances after implantation in the body because of the deterioration of material properties, such as degradation of natural biopolymers in the electrode. Here, thiolated HA (HA-SH) was synthesized and introduced into PPy electrodes (PPy/HA-SH) to enhance the enzymatic stabilities of PPy electrodes against hyaluronidase (HAase) and endow these electrodes with robust resistances to non-specific cell adhesion, thereby enabling prolonged signal transmission. Unlike PPy/HA, PPy/HA-SH resisted cell adhesion even in the presence of HAase. Subcutaneous implantation studies revealed that PPy/HA-SH formed less fibrotic scar tissue and permitted more sensitive and stable signal recording for up to 15 days after implantation as compared to PPy/HA. These findings hold significance for the design and advancement of biocompatible implantable bioelectrodes for a wide range of applications, such as neural electrodes, cardiac pacemakers, and biosensors.

Biofouling behaviors of reverse osmosis membrane in the presence of trace plasticizer for circulating cooling water treatment: Characteristics and mechanisms.

Reverse osmosis (RO) system has been increasingly applied for circulating cooling water (CCW) reclamation. Plasticizers, which may be dissolved into CCW system in plastic manufacturing industry, cannot be completely removed by the pretreatment prior to RO system, possibly leading to severe membrane biofouling. Deciphering the characteristics and mechanisms of RO membrane biofouling in the presence of trace plasticizers are of paramount importance to the development of effective fouling control strategies. Herein, we demonstrate that exposure to a low concentration (1 - 10 µg/L) of three typical plasticizers (Dibutyl phthalate (DBP), Tributyl phosphate (TBP) and 2,2,4-Trimethylpentane-1,3-diol (TMPD)) detected in pretreated real CCW promoted Escherichia coli biofilm formation. DBP, TBP and TMPD showed the highest stimulation at 5 or 10 µg/L with biomass increasing by 55.7 ± 8.2 %, 35.9 ± 9.5 % and 32.2 ± 14.7 % respectively, relative to the unexposed control. Accordingly, the bacteria upon exposure to trace plasticizers showed enhanced adenosine triphosphate (ATP) activity, stimulated extracellular polymeric substances (EPS) excretion and suppressed intracellular reactive oxygen species (ROS) induction, causing by upregulation of related genes. Long-term study further showed that the RO membranes flowing by the pretreated real CCW in a polypropylene plant exhibited a severer biofouling behavior than exposed control, and DBP and TBP parts played a key role in stimulation effects on bacterial proliferation. Overall, we demonstrate that RO membrane exposure to trace plasticizers in pretreated CCW can upregulate molecular processes and physiologic responses that accelerate membrane biofouling, which provides important implications for biofouling control strategies in membrane-based CCW treatment systems.

The effect of temperature on fouling in anaerobic membrane bioreactor: SMP- and EPS-membrane interactions.

Biofouling is the main challenge in the operation of anaerobic membrane bioreactors (AnMBRs). Biofouling strongly depends on temperature; therefore, we hypothesize that the interactions and viscoelastic properties of soluble microbial products (SMP) and extracellular polymeric substances (EPS) vary with temperature, consequently influencing membrane permeability. This study compares the performance of an AnMBR operated at a similar permeate flux at two temperatures. The transmembrane pressure (TMP) rose rapidly after 5 ± 2 days at 25 °C but only after 18 ± 2 days at 35 °C, although the reactor's biological performance was similar at both temperatures, in terms of the efficiency of dissolved organic carbon removal and biogas composition, which were obtained by changing the hydraulic retention time. Using confocal laser scanning microscopy (CLSM), a higher biofilm amount was detected at 25 °C than at 35 °C, while quartz crystal microbalance with dissipation (QCM-D) showed a more adhesive, but less viscous and elastic EPS layer. In situ optical coherence tomography (OCT) of an ultra-filtration membrane, fed with the mixed liquor suspended solids (MLSS) at the two temperatures, revealed that while a higher rate of TMP increase was obtained at 25 °C, the attachment of biomass from MLSS was markedly less. Increased EPS adhesion to the membrane can accelerate TMP increase during the operation of both the AnMBR and the OCT filtration cell. EPS's reduced viscoelasticity at 25 °C suggests reduced floc integrity and possible increased EPS penetration into the membrane pores. Analysis of the structures of the microbial communities constituting the AnMBR flocs and membrane biofilms reveals temperature's effects on microbial richness, diversity, and abundance, which likely influence the observed EPS properties and consequent AnMBR fouling.

Antifouling activities of proteinase K and α-amylase enzymes: Laboratory bioassays and in silico analysis.

The application of enzymes as antifoulants is one of the environment-friendly strategies in biofouling management. In this study, antifouling activities of commercially available proteinase K and α-amylase enzymes were evaluated using barnacle larva and biofilm-forming bacteria as test organisms. The enzymes were also tested against barnacle cement protein through in silico analysis. The results showed that both enzymes inhibited the attachment of bacteria and settlement of barnacle larvae on the test surface. The lowest minimum inhibitory concentration of 0.312 mg ml-1 was exhibited by proteinase K against biofilm-forming bacteria. The calculated LC50 values for proteinase K and α-amylase against the barnacle nauplii were 91.8 and 230.96 mg ml-1 respectively. While α-amylase showed higher antibiofilm activity, proteinase K exhibited higher anti-larval settlement activity. Similarly, in silico analysis of the enzymes revealed promising anti-settlement activity, as the enzymes showed good binding scores with barnacle cement protein. Overall, the results suggested that the enzymes proteinase K and α-amylase could be used in antifouling coatings to reduce the settlement of biofouling on artificial materials in the marine environment.

Polyaromatic Hydrocarbon-Functionalized 2D MXene-Based 3D Porous Antifouling Nanocomposite with Long Shelf Life for High-Performance Electrochemical Immunosensor Applications.

Affinity-based electrochemical (AEC) biosensors have gained more attention in the field of point-of-care management. However, AEC sensing is hampered by biofouling of the electrode surface and degradation of the antifouling material. Therefore, a breakthrough in antifouling nanomaterials is crucial for the fabrication of reliable AEC biosensors. Herein, for the first time, we propose 1-pyrenebutyric acid-functionalized MXene to develop an antifouling nanocomposite to resist biofouling in the immunosensors. The nanocomposite consisted of a 3D porous network of bovine serum albumin cross-linked with glutaraldehyde with functionalized MXene as conductive nanofillers, where the inherited oxidation resistance property of functionalized MXene improved the electrochemical lifetime of the nanocomposite. On the other hand, the size-extruded porous structure of the nanocomposite inhibited the biofouling activity on the electrode surface for up to 90 days in real samples. As a proof of concept, the antifouling nanocomposite was utilized to fabricate a multiplexed immunosensor for the detection of C-reactive protein (CRP) and ferritin biomarkers. The fabricated sensor showed good selectivity over time and an excellent limit of detection for CRP and ferritin of 6.2 and 4.2 pg/mL, respectively. This research successfully demonstrated that functionalized MXene-based antifouling nanocomposites have great potential to develop high-performance and low-cost immunosensors.

Development of methodology for the visual identification of Tributyltin (TBT) in antifouling paint matrices.

Organotin compounds (OTC), mainly tributyltin (TBT), have been used since the 1970s as biocides in the composition of antifouling paints. Due to its physical-chemical characteristics, TBT has high toxicity to the marine environment affecting non-target organisms. The present study aims to develop a method of direct visual identification of TBT in antifouling paints using the cyclopalladate complex, 4- (2-thiazolylazo) resorcinol (TAR-Pd), synthesized in our laboratory. Tests were performed in blank and in the paint matrix with the following OTC: TBT-O; TBT-Cl; TPT-Cl; DBT-Cl (tributyltin oxide, tributyltin chloride, triphenyltin chloride, dibutyltin chloride), in addition to the SnCl4 and SnCl2 compounds (tin IV chloride and tin II chloride), all at a concentration of approximately 20 g/ kg of dry paint). The test was performed by applying paint samples to test bodies and scraping a few tens of milligrams of the dry paint film. The scraped paint samples were submitted to the test, showing a different staining reaction for the TBT-Cl and SnCl4 samples concerning blank and other samples (TBT-O, TPT, DBT-Cl, and SnCl2). Solution tests were performed to characterize reaction products by spectroscopy in the visible band. The method developed has potential for application in real samples, being selective for TBT-Cl and SnCl4 in an acid medium, obtaining a limit of detection, in the range of 1-10 mg/kg dry paint.

Chalcone derivatives as promising antifoulants: Molecular optimization, bioactivity evaluation and performance in coatings.

Marine biofouling remains a huge concern for maritime industries and for environmental health. Although the current biocide-based antifouling coatings can prevent marine biofouling, their use has been associated with toxicity for the marine environment, being urgent to find sustainable alternatives. Previously, our research group has identified a prenylated chalcone (1) with promising antifouling activity against the settlement of larvae of the macrofouling species Mytilus galloprovincialis (EC50 = 16.48 µM and LC50 > 200 µM) and lower ecotoxicity when compared to Econea®, a commercial antifouling agent in use. Herein, a series of chalcone 1 analogues were designed and synthesized in order to obtain optimized antifouling compounds with improved potency while maintaining low ecotoxicity. Compounds 8, 15, 24, and 27 showed promising antifouling activity against the settlement of M. galloprovincialis larvae, being dihydrochalcone 27 the most potent. The effect of compound 24 was associated with the inhibition of acetylcholinesterase activity. Among the synthesized compounds, compound 24 also showed potent complementary activity against Navicula sp. (EC50 = 4.86 µM), similarly to the lead chalcone 1 (EC50 = 6.75 µM). Regarding the structure-activity relationship, the overall results demonstrate that the substitution of the chalcone of the lead compound 1 by a dihydrochalcone scaffold resulted in an optimized potency against the settlement of mussel larvae. Marine polyurethane (PU)-based coatings containing the best performed compound concerning anti-settlement activity (dihydrochalcone 27) were prepared, and mussel larvae adherence was reduced compared to control PU coatings.

Hybrid Zinc Phthalocyanine/PVDF-HFP System for Reducing Biofouling in Water Desalination: DFT Theoretical and MolDock Investigations.

Fouling and biofouling remain significant challenges in seawater desalination plants. One practical approach to address these issues is to develop anti-biofouling membranes. Therefore, novel hybrid zinc phthalocyanine/polyvinylidene fluoride-co-hexafluoropropylene (Zn(4-PPOx)4Pc/PVDF-HFP) membranes were prepared by electrospinning to evaluate their properties against biofouling. The hybrid nanofiber membrane was characterized by atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle measurements. The theoretical calculations of PVDF-HFP, Zn(4-PPOx)4Pc), and Zn(4-PPOx)4Pc/PVDF-HFP nanofibers were performed using a hybrid functional RB3LYP and the 6-31 G (d,p) basis set, employing Gaussian 09. DFT calculations illustrated that the calculated physical and electronic parameters ensured the feasibility of the interaction of PVDF-HFP with Zn(4-PPOx)4Pc via a halogen-hydrogen bond, resulting in a highly stable and remarkably reactive structure. Moreover, molecular electrostatic potential (MEP) maps were drawn to identify the reactive regions of the Zn(4-PPOx)4Pc and PVDF-HFP/Zn(4-PPOx)4Pc nanofibers. Molecular docking analysis revealed that Zn(4-PPOx)4Pc has highest binding affinity (-8.56 kcal/mol) with protein from S. aureus (1N67) mainly with ten amino acids (ASP405, LYS374, GLU446, ASN406, ALA441, TYR372, LYS371, TYR448, LYS374, and ALA442). These findings highlight the promising potential of Zn(4-PPOx) 4Pc/PVDF-HFP nanocomposite membranes in improving the efficiency of water desalination by reducing biofouling and providing antibacterial properties.