Synthesis and Bacteriostatic Activity and Antifouling Capability of Benzamide Derivatives Containing Capsaicin

Five benzamide deriatives containing capsaicin were synthesized which have similar structures to capsaicin. Their yield was high. The monomers synthesized were characterized by IR, 1H NMR and MS spectroscopy. Characterization data are in agreement with the proposed structures of the products. These five compounds exhibit bacterial inhibition and N-[4-hydroxy-2-methyl-5-(methylthio)benzyl]benzamide(HMMBBA), for instance, shows that the minimal inhibitory concentrations(MIC) of HMMBBA are 0.125 and 0.25 mg/mL on Staphyloccocus aureus and Escherichia coli, respectively. A static test site was set up in the eighth harbor to investigate the antifouling effectiveness of the five new antifoulants. Five-month exposure experiments were performed on sets of panels coated with each of antifouling coatings, and the results were compared to that of the test panel without antifouling coating. Test boards with antifouling coating were covered with just a macroscopic fouling organism such as Balanus. The results of the present paper demonstrate that new antifoulants represent an alternative to the biocidal antifouling paint.     

Antimicrobial coatings on textiles–modification of sol–gel layers with organic and inorganic biocides

Antimicrobial textile materials were produced by sol–gel coatings with embedded biocidal compounds. For preparation a sol–gel procedure was used, starting from pure silica sols and 3-glycidyloxypropyltriethoxysilane (GLYEO) containing silica sols. These sols were modified with silver compounds, hexadecyltrimethyl-ammonium-p-toluolsulfonat (HTAT) and copper compounds, respectively. The investigations were performed on viscose fabrics as function of the concentration of biocidal compounds and of thermal treatment of textile after dip-coating between 80 up to 180 °C. The use of modified silica coatings leads to a decreased growth of fungi (Aspergillus niger) and bacteria (Bacillus subtilis and Pseudomonas putida) with increasing amount of the biocide embedded in the coating. The addition of GLYEO supports the biocidal effect of the coatings and enhances the stability of the coating solutions. For preparation of antimicrobial silica coatings the biocides silver, copper or HTAT can be used alone but the combination of these compounds leads to enhanced results against both fungi and bacteria. Therefore silica sols containing a combination of different types of biocides may be used for antimicrobial modification of textiles in some practical applications. For industrial applications the here presented coating solutions are especially advantageous, because of 90% water content in the solvent.     

Synthetic aspects of tetraorganotins and organotin(IV) halides

Organotin(IV) compounds are being used for many applications, e.g., as stabilizers in PVC, in anti-fouling paints and coatings for the protection of ship hulls and as precursors for SnO₂-coatings on glass. Tetraorganotins and especially organotin(IV) halides often serve as synthetic precursors. A wide range of methods for the synthetic preparation of these compounds has been developed since the 1940s. This review gives an overview of the available routes for the preparation of organotin(IV) compounds and discusses their selectivity and yield. In particular, monoorganotin trihalides are often not accessible in high yield.     

Application of organotin compounds for protecting wood and other materials and in nonfouling paints

The present review is the third part of a review series dedicated to application of organotin compounds. This part discusses the application of organotin compounds for protection of wood and other natural and synthetic materials from biological damage, as well as biocidal additives to nonfouling paints. The prospects are discussed of using organotin compounds in these areas.     

Organotin catalysts in organosilicon chemistry

Organotin compounds are best known in the chemical industry as PVC stabilizers, polyurethane foam formers and antifungal agents. However, they have also been widely used in the silicon industry for decades for curing organosilicon polymers, despite the fact that neither the mechanism through which the siloxane bonds are formed nor their inherent toxicity are completely understood. This review gives an account of the use of organotin compounds in the preparation of diverse polysiloxane‐containing materials via cross‐linking with either organic or inorganic polymers. As they are common ingredients for this application, a brief outline of the preparation of relevant silicon‐containing compounds, as well as their reactivity, are given. In addition, since there is some evidence that stannasiloxanes formed in situ during the reaction play a determinant role as intermediates in the reaction mechanism, an overview of the synthesis and reactivity of Sn‐O‐Si‐containing compounds is also presented. Copyright © 2012 John Wiley & Sons, Ltd.     

Novel marine antifouling coatings inspired by corals

Biofouling is a major problem facing the marine industry. Since toxic antifouling coatings were banned globally due to their negative impacts on the marine environment, the development of environmental-friendly and efficient antifouling coatings has been identified as a pressing need. As an alternative, the antifouling coatings inspired by corals have attracted a great deal of attention over these years. within the marine environment, corals have evolved an excellent antifouling capability. There are five major antifouling strategies applied by corals, including natural antifoulants, foul release effect, sloughing effect, soft tentacles, and fluorescence effect. In this paper, a brief review is conducted to introduce the antifouling coatings inspired by the five strategies. Moreover, a discussion is conducted about the existing problems with the five strategies and the direction of their further development is indicated.     

The use of High-Performance Liquid Chromatography for the Speciation of Organotin Compounds

This review of the use of high-performance liquid chromatography (HPLC) for the speciation of organotin compounds which are primarily of significance in the marine environment is divided into sections on the basis of the different HPLC modes of separation. However, it should be noted that such a classification does not exist in reality. For instance, in an ion-pair reversed-phase system the separation mechanism for the ionic solutes may be ion-pair partitioning, or ion exchange, or both. The relevant practical information (e.g. column type, mobile phase, method of detection and detection limit) is presented in tabular form. A brief overview of the reported detection methods is included, because the delay in development of an easily interfaced, specific and sensitive detector has hindered the use of HPLC for organotin speciation studies. The literature reviewed covers publications from 1977, the year of the first application of HPLC to organotin speciation, to April 1995.     

Toxicity of butyltin,phenyltin and inorganic tin compounds to sulfate‐reducing bacteria isolated from anoxic marine sediments

The toxicity of butyltin, phenyltin and inorganic tin compounds to three pure strains of sulfate‐reducing bacteria (SRB), isolated from a tributyltin (TBT)‐polluted sediment, was determined. The isolated strains were identified as belonging to the genus Desulfovibrio. A new toxicological index (GR₂₅) was developed to assay the toxicity of organotin compounds. Deleterious effects on suspended anaerobic cell cultures were observed for concentrations ranging between 500 and 600 µM for tin tetrachloride, 55 and 260 µM for triorganotins, 30 and 90 µM for diorganotins, and 1 and 6 µM for mono‐organotins. Whereas the number of substituents influenced the toxicity of organotins, the type of substituent (butyl or phenyl) proved to have little or no impact. Trisubstituted compounds (tributyl‐ and triphenyl‐tin) were less toxic to these strains of SRB than the monosubstituted forms (monobutyl‐ and monophenyl‐tin). This is the opposite trend to that currently reported for aerobic organisms. Under the given anoxic conditions, the toxicity of organotin compounds obtained yielded a significant negative correlation with the total surface area (TSA) of the tested molecules. Comparison of the TBT toxicity data observed for different microbial groups suggests that the tolerance of bacteria to organotin compounds might be related to organotin–cell wall interactions as well as to aerobic or anaerobic metabolise pathways. Copyright © 2000 John Wiley & Sons, Ltd.     

Alternative antifouling biocides

In response to increasing scientific evidence on the toxicity and occurrence of organotin residues from antifouling paints in the aquatic environment, the use of triorganotin antifouling products was banned on boats of less than 25 m length in many countries during 1987. The use of tributyltin (TBT) products on small boats was superseded by products based on copper, containing organic booster biocides to improve the efficacy of the formulation. Available information and evidence on the occurrence, fate and toxicity of these biocides is reviewed. It is concluded that increased copper concentrations in the aquatic environment, due to the increased use of copper‐based antifoulants, do not have significant effects on marine ecosystems. However, lack of validated analytical methods, limited monitoring data, and very little information about the fate and toxicity of the booster biocides in the aquatic environment, make accurate risk assessments in relation to these compounds difficult. Copyright © 1999 John Wiley & Sons, Ltd.     

Long lasting marine antifouling polyurethane coating chemically bonded with poly(hexamethylene guanidine)

In order to protect the marine environment, traditional marine antifouling coatings such as tributyltin (TBT)-based antifouling coatings have been phased out. There is an urgent need to develop environmentally friendly marine antifouling coatings. In this work, the antibacterial poly(hexamethylene guanidine) (PHMG) was introduced into polyurethane (PU) through chemical bond to prepare a green environmentally friendly marine antifouling coating (PU-PHMG). The morphology, antimicrobial properties, mechanical properties and thermostability of the PU-PHMG films were investigated. The antimicrobial rates of PU-PHMG films against E. coli and S. aureus were both more than 99.9% when PHMG content in the films reached 1.0 wt%. The excellent antimicrobial activities can be maintained for more than 90 days due to the non-leaching characteristic of PHMG. The growth of algae was also inhibited on the surface of PU-PHMG films. The PU-PHMG coating is promising for the applications in marine antifouling field.     

N-halamine biocidal coatings via a layer-by-layer assembly technique

Two N-halamine copolymer precursors, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-acrylic acid potassium salt) and poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-trimethyl-2-methacryloxyethylammonium chloride) have been synthesized and successfully coated onto cotton fabric via a layer-by-layer (LbL) assembly technique. A multilayer thin film was deposited onto the fiber surfaces by alternative exposure to polyelectrolyte solutions. The coating was rendered biocidal by a dilute household bleach treatment. The biocidal efficacies of tested swatches composed of treated fibers were evaluated against Staphylococcus aureus and Escherichia coli. It was determined that chlorinated samples inactivated both S. aureus and E. coli O157:H7 within 15 min of contact time, whereas the unchlorinated control samples did not exhibit significant biocidal activities. Stabilities of the coatings toward washing and ultraviolet light exposure have also been studied. It was found that the stability toward washing was superior, whereas the UVA light stability was moderate compared to previously studied N-halamine moieties. The layer-by-layer assembly technique can be used to attach N-halamine precursor polymers onto cellulose surfaces without using covalently bonding tethering groups which limit the structure designs. In addition, ionic precursors are very soluble in water, thus promising for biocidal coatings without the use of organic solvents.     

Recovery of all species from photolytic degradation of tributyltin compounds TBTX (X = Cl,OSn Bu3)

Malformations in shellfish have been reported by many authors. They attributed the cause of the deformity to the presence in water of organotin compounds used in the formulation of antifouling paints, for example bis(tributyltin) oxide (TBTO) and tributyltin chloride (TBTC). The behaviour of these compounds has been examined under abiotic laboratory conditions. The influence of many parameters such as sunlight, pH, oxygen, salinity have been examined. The degradation compounds obtained have been identified: (1) In the gas phase two major products, butene-1 and buetene-2, are observed with consumption of oxygen; (2) In the liquid phase, three main products are obtained, butanol-1, butanol-2 and butanone 2. The identified products represent a small part of the total concentration, suggesting a competing process such as formation of butyltin polymers; (3) In fresh water an amorphous solid phase is observed while in seawater a white cristalline precipitate appears.     

New developments in catalysis

Environmental, safety and health concerns are major driving forces for the development of new coating systems, which in turn require catalysts with a different performance profile. One critical area for the development of new catalysts is the replacement of organotin compounds in polyurethanes with environmentally friendly catalysts, such as bismuth, aluminum and zirconium chelates. For applications in epoxies new catalysts for the epoxy-carboxyl reaction are also being developed. To gain the needed improved performance multiple cure mechanisms are being employed in coatings requiring dual action catalysts.     

Occurrence and chemical speciation analysis of organotin compounds in the environment: A review

Environmental concerns regarding organotin compounds have increased remarkably in the past 20 years, due in large part to the use of these compounds as active components in antifouling paints [mainly tributyltin (TBT)] and pesticide formulations [mainly triphenyltin (TPhT)]. Their direct introduction into the environment, their bio-accumulation and the high toxicity of these compounds towards “non-target” organisms (for example: oysters and mussels) causes environmental and economic damage around the world. As a consequence, the presence and absence of organotin compounds is currently monitored in a range of environmental matrices (e.g., water, sediment and shellfish) to examine the utility of controls meant to regulate the level of contamination as required in some EC Directives and the Water Framework Directive 2000/60/EC. To evaluate the environmental distribution and fate of these compounds and to determine the effectives of legal provisions adopted by a number of countries, a variety of analytical methods have been developed for organotin determination in the environment. Most of these methods include different steps such as extraction, derivatisation and clean up. The aim of the present review is to evaluate the environmental distribution, fate and chemical speciation of organotin compounds in the environment.     

Systèmes catalytiques retardés pour des élastomères polyuréthannes: Application à la préparation d'inhibiteurs de combustion de blocs de propergols

Elastomeric polyurethanes are widely used as inhibitor coatings for solid rocket propellant charges for protection against undesired burning-off. For safety, inhibition must be done at room temperature but, for economic reasons, polymerisation must occur in a short time after the moulding is finished. We have developed a satisfactory room temperature delayed action catalyst for elastomeric polyurethanes. The proposed system comprises an organotin catalyst, a suppressor component and a chemical scavenger; the catalyst is temporarily inactivated by addition of a consumable suppressor. β-Dicarbonyl compounds have been used already as suppressor for the organotin catalysts, but reactivation was done thermally. The use of alkaline acetates as scavengers allows progressive restoration of the activity of the catalyst at room temperature. With this method, it is possible to modify the rate of cure by changing the concentration of alkaline acetate. Thus the potlife can be increased without increase of the required tack-free time for the resin.     

Structures and antifouling properties of low surface energy non-toxic antifouling coatings modified by nano-SiO_2 powder

Antifouling coatings are used to improve the speed and energy efficiency of ships by preventing or- ganisms, such as barnacles and weed, building up on the underwater hull and helping the ships movement through the water. Typically, marine coatings are tributyltin self-polishing copolymer paints containing toxic molecules called biocides. They have been the most successful in combating bio- fouling on ships, but their widespread use has caused severe pollution in the marine ecosystem. The low surface energy marine coating is an entirely non-toxic alternative, which reduces the adhesion strength of marine organisms, facilitating their hydrodynamic removal at high speeds. In this paper, the novel low surface energy non-toxic marine antifouling coatings were prepared with modified acrylic resin, nano-SiO2, and other pigments. The effects of nano-SiO2 on the surface structure and elastic modulus of coating films have been studied, and the seawater test has been carried out in the Dalian Bay. The results showed that micro-nano layered structures on the coating films and the lowest surface energy and elastic modulus could be obtained when an appropriate mass ratio of resin, nano-SiO2, and other pigments in coatings approached. The seawater exposure test has shown that the lower the sur- face energy and elastic modulus of coatings are, the less the marine biofouling adheres on the coating films.     

Organotin biocides XV: Modelling the interactions of triorganotins with cell membranes

The interaction of triorganotins with cell membranes has been examined using synthetic phospholipid membranes (vesicles). Electron microscopy and NMR methods indicate that the organotin is in a five-coordinate environment at the membrane surface, and is associated weakly with the phosphate headgroups of the vesicle components. Both trimethyl- and tributyl-tin cause extensive modifications to the vesicles including fusion, aggregation, blebbing and total rupture, these effects being initiated at concentrations as low as 25 μmol dm^?3.     

Correlation of molecular total surface area with organotin toxicity for biological and physicochemical applications

There exists a high correlation between molecular total surface area (TSA) values and diorganotin toxicity towards several distinct types of organisms. This correlation was found for N₂a neuroblastoma cells, 3T3 fibroblasts, Daphnia magna Rhithropanopeus harrisii and Ankistrodesmus falcatus. In the case of Rhithropanopeus harrisii, a high correlation was also found between TSA and toxicity for triorganotins as well. This study suggests that the relationship between TSA and toxicity is a function of the hydrophobicity of the organotin compounds rather than electronic or steric effects.     

Organotin compounds: Toxicology and biomedicinal applications

The toxicology and biomedical aspects and applications of organotin compounds are discussed. Factors affecting toxicity are considered first and then the mechanisms of toxicity are described and assessed. A review of the main biomedical applications then follows, covering biochemical, agricultural and other biocidal uses, and recent developments in the field of anticarcinogenesis.     

Silver bromide nanoparticle/polymer composites: dual action tunable antimicrobial materials

We present a simple method of fabricating highly potent dual action antibacterial composites consisting of a cationic polymer matrix and embedded silver bromide nanoparticles. A simple and novel technique of on-site precipitation of AgBr was used to synthesize the polymer/nanoparticle composites. The synthesized composites have potent antibacterial activity toward both gram-positive and gram-negative bacteria. The materials form good coatings on surfaces and kill both airborne and waterborne bacteria. Surfaces coated with these composites resist biofilm formation. These composites are different from other silver-containing antibacterial materials both in the ease of synthesis and in the use of a silver salt nanoparticle instead of elemental silver or complex silver compounds. We also demonstrate the ability to tune the release of biocidal Ag(+) ions from these composites by controlling the size of the embedded AgBr nanoparticles. These composites are potentially useful as antimicrobial coatings in a wide variety of biomedical and general use applications.