Antifouling activity of simple synthetic diterpenoids against larvae of the barnacle Balanus albicostatus Pilsbry

Five new pimarane diterpenoids 1-5 were synthesized using ent-8(14)-pimarene-15R,16-diol as starting material. The structures were elucidated by means of extensive NMR and MS analysis. The antifouling activity against larval settlement of the barnacle Balanus albicostatus were evaluated using capsaicin as a positive control. Compounds 1-3 and 5 showed more potent antifouling activity than capsaicin. Compound 5, which exhibited almost the same antifouling activity as starting material, showed better stability than starting material. These compounds all showed antifouling activity in a non-toxic way against larval settlement of the barnacle B. albicostatus. Analysis of structure-activity relationships (SAR) demonstrated that the substituents on the C-15 and C-16 position of pimarane diterpenoid were responsible for the antifouling activity.     

Engineered nanoforce gradients for inhibition of settlement (attachment) of swimming algal spores

Current antifouling strategies are focused on the development of environmentally friendly coatings that protect submerged surfaces from the accumulation of colonizing organisms (i.e., biofouling). One ecofriendly approach is the manipulation of the surface topography on nontoxic materials to deter settlement of the dispersal stages of fouling organisms. The identification of effective antifouling topographies typically occurs through trial-and-error rather than predictive models. We present a model and design methodology for the identification of nontoxic, antifouling surface topographies for use in the marine environment by the creation of engineered nanoforce gradients. The design and fabrication of these gradients incorporate discrete micrometer-sized features that are associated with the species-specific surface design technique of engineered topography and the concepts of mechanotransduction. The effectiveness of designed nanoforce gradients for antifouling applications was tested by evaluating the settlement behavior of zoospores of the alga Ulva linza. The surfaces with nanoforce gradients ranging from 125 to 374 nN all significantly reduced spore settlement relative to a smooth substrate, with the highest reduction, 53%, measured on the 374 nN gradient surface. These results confirm that the designed nanoforce gradients may be an effective tool and predictive model for the design of unique nontoxic, nonfouling surfaces for marine applications as well as biomedical surfaces in the physiological environment.     

原位探测防污高分子材料与液体界面的分子结构

Marine organisms such as plants, algae or small animals can adhere to surfaces of materials that are submerged in ocean. The accumulation of these organisms on surfaces is a marine biofouling process that has considerable adverse effects. Marine biofouling on ship hulls can cause severe fuel consumption increase. Investigations on antifouling polymers are therefore becoming important research topics for marine vessel operations. Antifouling polymers can be applied as coating layers on the ship hull, protecting it against the settlement and growth of sea organisms. Polyethylene glycol (PEG) is a hydrophilic polymer that can effectively resist the accumulation of marine organisms. PEG-based antifouling coatings have therefore been extensively researched and developed. However, the inferior stability of PEG makes it subject to degradation, rendering it ineffective for long-term services. Zwitterionic polymers have also emerged as promising antifouling materials in recent years. These polymers consist of both positively charged and negatively charged functional groups. Various zwitterionic polymers have been demonstrated to exhibit exceptional antifouling properties. Previously, surface characterizations of zwitterionic polymers have revealed that strong surface hydration is critical for their antifouling properties. In addition to these hydrophilic polymers, amphiphilic materials have also been developed as potential antifouling coatings. Both hydrophobic and hydrophilic functional groups are incorporated into the backbones or sidechains of these polymers. It has been demonstrated that the antifouling performance can be enhanced by precisely controlling the sequence of the hydrophobic-hydrophilic functionalities. Since biofouling generally occurs at the outer surface of the coatings, the antifouling properties of these coatings are closely related to their surface characteristics in water. Therefore, understanding of the surface molecular structures of antifouling materials is imperative for their future developments. In this review, we will summarize our recent advancements of antifouling material surface analysis using sum frequency generation (SFG) vibrational spectroscopy. SFG is a surface-sensitive technique which can provide molecular information of water and polymer structures at interfaces in situ in real time. The antifouling polymers we will review include zwitterionic polymer brushes, mixed charged polymers, and amphiphilic polypeptoids. Interfacial hydration studies of these polymers by SFG will be presented. The salt effect on antifouling polymer surface hydration will also be discussed. In addition, the interactions between antifouling materials and protein molecules as well as algae will be reviewed. The above research clearly established strong correlations between strong surface hydration and good antifouling properties. It also demonstrated that SFG is a powerful technique to provide molecular level understanding of polymer antifouling mechanisms.     

水性防污涂料的研究进展

海洋污损生物是海洋资源开发首先要面对的问题。防污涂料是防除海洋污损生物的关键材料。传统的防污涂料虽然发展成熟,但以油性溶剂为介质,存在挥发性有机物(VOC)排放过高、环境污染严重的问题。不释放VOC的水性涂料符合绿色无污染的环保要求,是防污材料领域研究的热点。本文对最重要的四种水性防污涂料(污损释放型水性低表面能防污涂料、自抛光型水性防污涂料、污损阻抗型水凝胶海洋防污涂料、强碱释放型水性硅酸盐防污涂料)从防污机理、制备方法和存在的问题等几个方面进行了综述,并对水性防污涂料的发展趋势进行了展望。     

新型含吲哚环酯类化合物的合成、抑藻活性及构效关系研究

从苔藓虫Zoobotryon pellucidum中提取的2,5,6-三溴-1-甲基芦竹碱(TBG)能较好地抑制海洋生物藤壶的附着. 为提高该类化合物在防污涂料中的复配性能, 合成了4个新型的不同卤素取代和N-取代且具有较好亲脂性能的TBG类似物. 通过1H NMR, 13C NMR, IR和元素分析对目标化合物6a～6d进行了结构表征. 生物实验结果表明, 化合物5～6对海藻Nitzschia closterium均具有较好的生长抑制活性, 其中以亲脂性较强的6b和6d抑制作用最为显著, LC50分别可达1.33 µg/mL和1.06 µg/mL. 对化合物的定量构效关系进行了初步探讨.     

Terpenoids from a Chinese Gorgonian Anthogorgia sp. and Their Antifouling Activities

Chemical examination of a Chinese gorgonian Anthogorgia sp. resulted in the isolation of seven terpenoids, including two new compounds, an rearranged serrulatane‐type diterpenoid anthogorgiene P ( 1 ) and a guaiazuene‐based terpenoid anthogorgiene Q ( 2 ). Anthogorgiene P ( 1 ) contains an unprecedented cubebane nucleus which is rarely found from nature. The structures of new compounds were elucidated on the basis of extensive spectroscopic methods (IR, UV, MS, CD and NMR). Compound 7 showed potent antifouling activity against the larval settlement of Balanus amphitrite, while 1 and 4 possessed moderate inhibition.     

Ten new antifouling briarane diterpenoids from the South China Sea gorgonian Junceella juncea

Ten new antifouling briarane diterpenoids, juncins R-ZI (1-10) were isolated from the South China Sea gorgonian coral Junceella juncea. The structures of these new compounds were established by extensive spectroscopic analysis, including 1D and 2D NMR data. Compounds 1-10 all showed potent antifouling activities against the larval settlement of barnacle Balanus amphitrite at nontoxic concentrations with EC₅₀ values of 0.004, 0.34, 2.65, 1.61, 3.77, 21.06, 0.004, 0.14, 1.47, and 0.51 μg mL⁻¹. The structure-activity relationship was discussed.     

Dihydroisocoumarin derivatives with antifouling activities from a gorgonian-derived Eurotium sp. fungus

Five pairs of new dihydroisocoumarin enantiomers, (±)-eurotiumides A–E, and two related racemates, (±)-eurotiumides F and G, were isolated from a gorgonian-derived fungus, Eurotium sp. XS-200900E6. The enantiomeric separations for (±)-eurotiumides A–E were achieved by chiral-HPLC, and their absolute configurations were determined by ECD spectra. All of the isolated compounds are rare dihydroisocoumarin derivatives with a methoxy at C-4. (+)- And (−)-eurotiumides B and D with cis configurations of H-3/H-4 exhibited potent antifouling activities against the larval settlement of the barnacle Balanus amphitrite with the EC₅₀ values ranging from 0.7 to 2.3 μg/mL, and displayed high therapeutic ratios (LC₅₀/EC₅₀ >15). The tested compounds also showed extensive antibacterial activities. It was the first report of antifouling activities for dihydroisocoumarin derivatives.     

Efficient and robust coatings using poly(2-methyl-2-oxazoline) and its copolymers for marine and bacterial fouling prevention

Molecular design, fabrication, and properties of thin-film coatings based on poly(2-methyl-2-oxazoline) (PMOX) and its copolymers were investigated to tackle problem of marine and bacterial fouling prevention. The ultraviolet crosslinkable macromonomer poly(2-methyl-2-oxazoline) dimethylacrylate was synthesized by cationic ring-opening polymerization in a microwave reactor initiated by 1,4-dibromobutane. In order to study the charge effect of the PMOX coatings on the adhesion of fouling organisms, PMOX surfaces with negative, neutral, and positive ζ-potential values were prepared by copolymerization with the positively charged monomer [2-(methacryloyloxy)-ethyl]trimethylammonium chloride. The coatings were stable in sea water for at least 1 month without significant reduction in the film thickness. The marine antifouling activity was evaluated against barnacle cyprids Amphibalanus amphitrite and algae Amphora coffeaeformis. Results showed that PMOX coatings provide effective reduction of the settlement regardless of the molar mass and surface charge of the polymer. Bacterial adhesion test showed that PMOX coatings effectively reduce Staphylococcus aureus and Escherichia coli adhesion. Owing to its good stability and antifouling activity PMOX has a great potential as antifouling coating for marine antifouling applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 275–283     

Settlement of Ulva zoospores on patterned fluorinated and PEGylated monolayer surfaces

Various designs for coatings that resist the attachment of marine organisms are based on the concept of "ambiguous" surfaces that present both hydrophobic and hydrophilic functionalities as surface domains. In order to facilitate the optimal design of such surfaces, information is needed on the scale of the domains that the settling stages of marine organisms are able to distinguish. Previous experiments showed that Ulva zoospores settle (attach) in high numbers onto fluorinated monolayers compared to PEGylated monolayers. The main aim of the present study was to determine, when zoospores of the green alga Ulva are presented with a choice of fluorinated or PEGylated surfaces, what the minimum dimensions of the two types of surface are that zoospores can detect and consequently settle on. Silicon wafers were chemically modified to produce a pattern of squares containing alternating fluorinated and PEGylated stripes of different widths on either a uniform fluorinated or PEGylated background. Each 1 cm x 1 cm square contained stripes with widths of 500, 200, 100, 50, 20, 5, or 2 microm as well as an unpatterned square with a chemistry opposite that of the background. Spores were selective in choosing where to settle, settling at higher densities on fluorinated stripes compared to PEGylated stripes. However, the magnitude of response, and the consequences for settlement on patterned areas overall, was dependent on both the width of the stripes and the chemistry of the background. The data are discussed in relation to the ability of spores to "choose" favorable sites for settlement and the implications for the development of novel antifouling coatings.     

Environmental aspects of tributyltin

The tributyltin species, the active ingredient in some antifouling paint formulations, is perhaps the most acutely toxic chemical to aquatic organisms ever deliberately introduced to water. It has been demonstrated to have an adverse effect on shellfish in France and England, and as a consequence the use of tributyltin-containing antifouling paints has been restricted in these countries. Other countries have banned the use of tributyltin-containing antifouling paints or are contemplating restrictions. This article reviews such environmental aspects of tributyltin as methods of analysis, toxicity, environmental occurrence, persistence and fate. Tributyltin concentrations in many locations may be high enough to cause chronic toxicity or harmful effects in some aquatic organisms, and in some locations the tributyltin concentrations may be high enough to be acutely toxic to some organisms. Biological degradation of tributyltin in water and sediment appears to be the most important factor limiting the persistence of tributyltin in aquatic environments. To some degree, then, the persistence of tributyltin in aquatic environments depends upon the nature of the ecosystem. Tributyltin exhibits low-to-medium persistence in water and moderate persistence in sediment. A summary is given of the regulatory status of tributyltin in some countries, and recommendations are made for further research.     

Pavidolides A-E, new cembranoids from the soft coral Sinularia pavida

Five new cembrane-based diterpenoids, namely pavidolides A-E (1-5) were isolated from the marine soft coral Sinularia pavida, together with sarcophytin and chatancin. The structures of new compounds were determined on the basis of extensive spectroscopic data analysis. Pavidolide B (2) possesses an unprecedented 6,5,7-tricarbocyclic nucleus, whereas pavidolide C (3) is characteristic of an unusual C-5 and C-9 conjuncted cembranoid. Pavidolides C and D showed moderate antifouling activity against the larval settlement of barnacle Balanus amphitrite, while pavidolides B and C exhibited inhibitory activity against the human leukemia cell line HL-60.     

Analytical methods for the determination of common booster biocides in marine samples

Booster biocides are organic compounds that are added to antifouling copper-based paints to improve their efficacy. Due to their widespread use, they are common pollutants of marine ecosystems. Some of these compounds show acute and chronic toxic effects in non-targeted organisms at concentrations as low as ng L⁻¹. The determination of these compounds is therefore important, and for some, which are prioritized in the EU water framework directive, a necessity.     

A multipurpose compound for protective coatings

International regulations concerning the protection of both the environment and industrial workers have prompted paint manufacturers and end users to look for suitable replacements for traditional pigments.One of the aims of this investigation was to study the inhibitive properties of ferric benzoate-based paints in simulated marine corrosion condition (3% NaCl solution). Anticorrosive paints containing ferric benzoate were formulated and their performance was evaluated by accelerated (salt fog chamber) and electrochemical (corrosion potential and ionic resistance) tests.In addition, the action of ferric benzoate as a probable antifouling agent was studied through laboratory tests and marine exposure. Ferric benzoate hydrolyzes in seawater producing a pH decrease. In this sense, the effects of the pH and the anion benzoate dissolved in seawater and leached from an antifouling paint were evaluated on Balanus amphitrite nauplii. Although benzoate anion showed an intense narcotic effect on nauplii, the results of this research clearly demonstrated that the antifouling activity is due to the combined action of this anion and the pH decrease, i.e. there exists a synergic effect. Field trials confirmed laboratory assays; paints containing ferric benzoate were effective for inhibiting organism settlement and as corrosion of metal.     

无毒海洋防污剂研究进展

综述了无毒海洋防污剂研究进展,从防污活性、机理、特点及应用等方面着手介绍了近年来开发的几种新型无毒天然产物防污剂和人工合成防污剂,并就其发展前景进行了展望;指出开发研制无毒海洋防污剂是海洋防污技术的发展方向之一.     

Anti-biofouling properties of comblike block copolymers with amphiphilic side chains

Surfaces of novel block copolymers with amphiphilic side chains were studied for their ability to influence the adhesion of marine organisms. The surface-active polymer, obtained by grafting fluorinated molecules with hydrophobic and hydrophilic blocks to a block copolymer precursor, showed interesting bioadhesion properties. Two different algal species, one of which adhered strongly to hydrophobic surfaces, and the other, to hydrophilic surfaces, showed notably weak adhesion to the amphiphilic surfaces. Both organisms are known to secrete adhesive macromolecules, with apparently different wetting characteristics, to attach to underwater surfaces. The ability of the amphiphilic surface to undergo an environment-dependent transformation in surface chemistry when in contact with the extracellular polymeric substances is a possible reason for its antifouling nature. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) was used, in a new approach based on angle-resolved X-ray photoelectron spectroscopy (XPS), to determine the variation in chemical composition within the top few nanometers of the surface and also to study the surface segregation of the amphiphilic block. A mathematical model to extract depth-profile information from the normalized NEXAFS partial electron yield is developed.     

具类辣素结构丙烯酰胺的合成及其抑菌和防污性能

以N-羟甲基丙烯酰胺和苯酚类化合物为原料,合成了N-(2-羟基-3-丙烯酰胺甲基-4,6-二甲基苄基)丙烯酰胺(HMABA)、N-(2-羟基-3-丙烯酰胺甲基-4,5-二甲基苄基)丙烯酰胺(AMHBA)、N-(3,5-二甲基-4-羟基苄基)丙烯酰胺(MHBA)、N-(3,6-二甲基-4-丙烯酰胺甲基-2-羟基苄基)丙烯酰胺(MAHBA)和N-(2甲氧基-4-甲基-5-丙烯酰胺甲基苄基)丙烯酰胺(MMABA)5个类辣素结构的丙烯酰胺衍生物。 通过红外光谱（IR）、核磁波谱（1H NMR）、质谱（HR-MS）和元素分析对化合物的结构进行了表征。 抑菌试验表明,HMABA对金黄色葡萄球菌和大肠杆菌的抑制效果最好,最低抑菌浓度均可达0.125 g/L。 将此5个化合物作为防污剂制备海洋防污涂料,120 d的实海结果表明,基本无污损海生物附着。     

Industrial contaminants in Antarctic biota

A critical review of the levels and patterns of industrial contaminants in biota from Antarctica and the Southern Ocean revealed that concentrations are low with respect to other regions of the world, although in some specimens/species (e.g. leopard seal, some invertebrates) they are occasionally high and comparable to those found in regions with a strong human impact; the highest levels of persistent organic pollutants (POPs) were detected in the vicinity of scientific stations. Bioconcentration prevails at the lower trophic levels of pelagic food webs, while biomagnification can become the main route of contamination at higher levels. In a benthic food web, biomagnification poses a major risk for organisms that accumulate lipids to overwinter, compared to those that accumulate glycogen. Hexachlorobenzene, DDTs and chlordanes showed similar concentrations and patterns in the 1980s-1990s period in organisms from Western and Eastern Antarctica, while the polychlorinated biphenyls time trend was different in a variety of species from the two regions.     

Saccharide-functionalized alkanethiols for fouling-resistant self-assembled monolayers: synthesis, monolayer properties, and antifouling behavior

We describe the synthesis of a series of mono-, di-, and trisaccharide-functionalized alkanethiols as well as the formation of fouling-resistant self-assembled monolayers (SAMs) from these. The SAMs were characterized using ellipsometry, wetting measurements, and infrared reflection-absorption spectroscopy (IRAS). We show that the structure of the carbohydrate moiety affects the packing density and that this also alters the alkane chain organization. Upon increasing the size of the sugar moieties (from mono- to di- and trisaccharides), the structural qualities of the monolayers deteriorated with increasing disorder, and for the trisaccharide, slow reorganization dynamics in response to changes in the environmental polarity were observed. The antifouling properties of these SAMs were investigated through protein adsorption experiments from buffer solutions as well as settlement (attachment) tests using two common marine fouling species, zoospores of the green macroalga Ulva linza and cypris larvae of the barnacle Balanus amphitrite. The SAMs showed overall good resistance to fouling by both the proteins and the tested marine organisms. To improve the packing density of the SAMs with bulky headgroups, we employed mixed SAMs where the saccharide-thiols are diluted with a filler molecule having a small 2-hydroxyethyl headgroup. This method also provides a means by which the steric availability of sugar moieties can be varied, which is of interest for specific interaction studies with surface-bound sugars. The results of the surface dilution study and the low nonspecific adsorption onto the SAMs both indicate the feasibility of this approach.