Chemical defence in mussels: antifouling effect of crude extracts of the periostracum of the blue mussel Mytilus edulis

Shells of the blue mussel Mytilus edulis remain free of fouling organisms as long as they possess an intact periostracum, and a multiple antifouling defence that comprises a ripple-like microtopography and the production of chemical antifouling compounds has been suggested previously. This study investigates the chemical defence strategy of blue mussels for the first time. Six crude extracts of the periostracum of intact shells were made using solvents of increasing polarity. These extracts were tested against common fouling organisms in laboratory based bioassays. Non-polar and moderately polar fractions showed the highest activities: the diethyl ether fraction strongly inhibited attachment of Balanus amphitrite cyprids and the marine bacteria Cobetia marina and Marinobacter hydrocarbonoclasticus. Attachment of the benthic diatom Amphora coffeaeformis was significantly reduced by the dichloromethane extract, whereas both ethyl acetate and diethyl ether fractions slowed diatom growth. These results provide the first evidence of surface bound compounds that may moderate surface colonisation

The Effect of Dissolved Organic Carbon on Bacterial Adhesion to Conditioning Films Adsorbed on Glass from Natural Seawater Collected during Different Seasons

Adhesion of three marine bacterial strains, i.e. Marinobacter hydrocarbonoclasticus, Psychrobacter sp. and Halomonas pacifica with different cell surface hydrophobicities was measured on glass in a stagnation point flow chamber. Prior to bacterial adhesion, the glass surface was conditioned for 1 h with natural seawater collected at different seasons in order to determine the effect of seawater composition on the conditioning film and bacterial adhesion to it. The presence of a conditioning film was demonstrated by an increase in water contact angle from 15° on bare glass to 50° on the conditioned glass, concurrent with an increase in the amount of adsorbed organic carbon and nitrogen, as measured by X-ray photoelectron spectroscopy. Multiple linear regression analysis on initial deposition rates, with as explanatory variables the temperature, salinity, pH and concentration of dissolved organic carbon (DOC) of the seawater at the time of collection, showed that the concentration of DOC was most strongly associated with the initial deposition rates of the three strains. Initial deposition rates of the two most hydrophilic strains to a conditioning film, increased with the concentration of DOC in the seawater, whereas the initial deposition rate of the most hydrophobic strain decreased with an increasing concentration of DOC

Bacterial deposition to fluoridated and non-fluoridated polyurethane coatings with different elastic modulus and surface tension in a parallel plate and a stagnation point flow chamber

Deposition of three marine bacterial strains with different cell surface hydrophobicities from artificial seawater to polyurethane coatings on glass with different surface tensions and elastic modulus was studied in situ in a parallel plate (PP) and stagnation point (SP) flow chamber. Different surface tensions of the coatings were established by changing the amount of fluorine, whereas using more or less branched polymers made different elastic moduli. Surface tensions of the coating, derived from measured contact angles with liquids, ranged from 11.9 to 44.9 mJ m-2, while the elastic moduli, derived from force-distance curves as measured with an atomic force microscope were between 1.5 and 2.2 GPa. In both flow chambers, the most hydrophilic bacterium Halomonas pacifica adhered preferentially to the more hydrophilic, non-fluoridated coating, whereas the most hydrophobic bacterium Marinobacter hydrocarbonoclasticus showed a greater preference for the more hydrophobic coating. Bacterial adhesion in the PP flow chamber was not influenced by the elastic modulus of the coatings, but in the SP flow chamber bacteria adhered in higher numbers to hard surfaces than to coatings of lower elastic moduli

Multiple linear regression analysis of bacterial deposition to polyurethane coating after conditioning film formation in the marine environment

Many studies have shown relationships of substratum hydrophobicity, charge or roughness with bacterial adhesion, although bacterial adhesion is governed by interplay of different physico-chemical properties and multiple regression analysis would be more suitable to reveal mechanisms of bacterial adhesion. The formation of a conditioning film of organic compounds adsorbed from seawater affects the properties of substratum surfaces prior to bacterial adhesion, which is a complicating factor in studying the mechanism of bacterial adhesion. In this paper, the impact of conditioning films adsorbed from natural seawater to four polyurethane coatings with different hydrophobicity, elasticity and roughness was studied for three different marine bacterial strains in a multiple linear regression analysis. The water contact angle on hydrophobic coatings decreased on average by 8 degrees and increased on average by the same amount on hydrophilic coatings. These changes were accompanied by increased concentrations of oxygen and nitrogen on the surface as determined by X-ray photoelectron spectroscopy, indicative of adsorption of proteinaceous material. Furthermore, the mean surface roughness increased on average by 4 nm after conditioning film formation. Multiple linear regression analysis revealed that changes in deposition due to conditioning film formation of Marinobacter hydrocarbonoclasticus, Psychrobacter sp. SW5H and Halomonas pacifica in a stag nation-point flow chamber could be explained in a model comprising hydrophobicity and the prevalence of nitrogen-rich components on the surface for the most hydrophobic strain. For the two more hydrophilic strains, deposition was governed by a combination of surface roughness and hydrophobicity. Elasticity was not a factor in bacterial adhesion to conditioning films

Degradation, intra-articular retention and biocompatibility of monospheres composed of [PDLLA-PEG-PDLLA]-b-PLLA multi-block copolymers

In this study, we investigated the use of microspheres with a narrow particle size distribution (‘monospheres’) composed of biodegradable poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide) multiblock copolymers that are potentially suitable for local sustained drug release in articular joints. Monospheres with sizes of 5, 15 and 30 μm and a narrow particle size distribution were prepared by a micro-sieve membrane emulsification process. During in vitro degradation, less crystallinity, higher swelling and accelerated mass loss during was observed with increasing the PEG content of the polymer. The monospheres were tested in both a small (mice/rat) and large animal model (horse). In vivo imaging after injection with fluorescent dye loaded microspheres in mice knees showed that monospheres of all sizes retained within the joint for at least 90 days, while the same dose of free dye redistributed to the whole body within the first day after intra-articular injection. Administration of monospheres in equine carpal joints caused a mild transient inflammatory response without any clinical signs and without degradation of the cartilage, as evidenced by the absence of degradation products of sulfated glycosaminoglycans or collagen type 2 in the synovial fluid. The excellent intra-articular biocompatibility was confirmed in rat knees, where μCT-imaging and histology showed neither changes in cartilage quality nor quantity. Given the good intra-articular retention and the excellent biocompatibility, these novel poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide)-based monospheres can be considered a suitable platform for intra-articular drug delivery. Statement of Significance This paper demonstrates the great potential in intra-articular drug delivery of monodisperse biodegradable microspheres which were prepared using a new class of biodegradable multi-block copolymers and a unique membrane emulsification process allowing the preparation of microspheres with a narrow particle size distribution (monospheres) leading to multiple advantages like better injectability, enhanced reproducibility and predictability of the in vivo release kinetics. We report not only on the synthesis and preparation, but also in vitro characterization, followed by in vivo testing of intra-articular biocompatibility of the monospheres in both a small and a large animal model. The favourable intra-articular biocompatibility combined with the prolonged intra-articular retention (>90 days) makes these monospheres an interesting drug delivery platform. What should also be highlighted is the use of horses; a very accurate translational model for the human situation, making the results not only relevant for equine healthcare, but also for the development of novel human OA therapies