Tout support immergé dans l'eau est rapidement colonisé par de nombreux organismes micro- et macroscopiques. Ce phénomène séquentiel et complexe appelé biofouling est à l'origine de nombreux préjudices économiques et écologiques, notamment dans le milieu marin. L'interdiction récente de certaines substances toxiques, utilisées comme biocides dans les revêtements antifouling des coques de bateaux notamment, a relancé l'intérêt de rechercher de nouvelles molécules antifouling respectueuses de l'environnement. L'objectif de cette thèse a été de développer et d'amorcer l'étude de la représentativité d'un bio-essai permettant d'évaluer le potentiel antifouling de molécules et de revêtements sur des " biofilms " mono et plurispécifiques in vitro en microplaques grâce à l'utilisation de fluorochromes. Le choix a été fait de se focaliser sur le biofilm primaire car il est envisagé que l'élimination ou la limitation de ce dernier réduisent le biofouling. Cinq souches de bactéries marines pionnières, isolées de la Rade de Toulon et en Bretagne, ont été utilisées afin de comparer l'efficacité anti-adhésion de molécules commerciales et naturelles. Deux dérivés de synthèse de substances naturelles marines (TFA E et Z) ont présenté une activité significative associée à une absence de toxicité sur bactéries, suggérant ainsi un mode d'action anti-adhésion spécifique. En outre, les différences de sensibilité entre souches ont confirmée l'importance de réaliser le bio-essai avec un panel diversifié de bactéries.Afin de voir si les données obtenues en laboratoire reflétaient ce qui se produit dans le milieu naturel, une comparaison entre les résultats du bio-essai en microplaque appliqué à six revêtements et les biofilms qui ont colonisés ces mêmes peintures immergées un mois dans la Rade de Toulon (analysés par cytométrie de flux, microscopie et PCR-DGGE), a été effectuée. Les analyses quantitatives ont suggéré une cohérence entre les deux approches même si l'absence de revêtement d'efficacité intermédiaire et le nombre de systèmes testés limite la portée de nos conclusions

The increasing prevalence of diabetes and the severity of long-term complications have emphasized the need for continuous glucose monitoring. Optically-based methods are advantageous as they have potential for noninvasive or minimally invasive detection. Fluorescence-based affinity assays, in particular, can be fast, reagentless, and highly specific. Poly(ethylene glycol) (PEG) microspheres have been used to encapsulate such fluorescently labeled molecules in a hydrogel matrix for implantation into the body. The matrix is designed to retain the sensing molecules while simultaneously allowing sufficient analyte diffusion. Sensing assays which depend upon a spatial displacement of molecules, however, experience limited motility and diminished sensor response in a dense matrix. In order to overcome this, a process of hydrogel microporation has been developed to create cavities within the PEG that contain the assay components in solution, providing improved motility for large sensing elements, while limiting leaching and increasing sensor lifetime. For an implanted sensor to be successful in vivo, it should exhibit long-term stability and functionality. Even biocompatible materials that have no toxic effect on surrounding tissues elicit a host response. Over time, a fibrous capsule forms around the implant, slowing diffusion of the target analyte to the sensor and limiting optical signal propagation. To prevent this biofouling, a thermoresponsive nanocomposite hydrogel based on poly(N-isopropylacrylamide) was developed to create a self-cleaning sensor membrane. These hydrogels exist in a swollen state at temperatures below the volume phase transition temperature (VPTT) and become increasingly hydrophobic as the temperature is raised. Upon thermal cycling around the VPTT, these hydrogels exhibit significant cell release in vitro. However, the VPTT of the original formula was around 33-34 degrees C, resulting in a gel that is in a collapsed state, ultimately limiting glucose diffusion at body temperature. The hydrogel was modified by introducing a hydrophilic comonomer, N-vinylpyrrolidone (NVP), to raise the VPTT above body temperature. The new formulation was optimized with regard to diffusion, mechanical strength, and cell releasing capabilities under physiological conditions. Overall, this system is a promising method to translate a glucose-sensitive assay from the cuvette to the clinic for minimally invasive continuous glucose sensing.

Marine biofouling is the accumulation of marine species on surfaces submerged in seawater leading to unwanted problems for man-made surfaces such as hulls of ships and aquaculture nets. Historically, the amount of biofouling was regulated using metal based coatings whose usage have been disused lately due to adverse toxic effects. Alternative environmentally friendly coatings are currently avidly being pursued. Nanopatterned polymer thin films were investigated as potential candidates for marine antifouling coatings. Polystyrene-block-poly(2-vinyl pyridine) and polystyrene-block-poly(methyl methacrylate) diblock copolymer thin films self-assembled using vapor solvent annealing into cylinders perpendicular to the substrate composed of poly(2-vinyl pyridine) or poly(methyl methacrylate) respectively with diameters between 30 nm to 82 nm and center-to-center spacing between 46 nm to 113 nm in a polystyrene matrix on various substrates such as silicon or nylon. Polystyrene-block-poly(2-vinyl pyridine) copolymers were also mixed with the photoinitiator benzophenone and irradiated with ultraviolet light to crosslink the polymer chains and decrease the surface hydrophobicity. In the case of polystyrene-block-poly(methyl methacrylate), the yield of these nanopatterned films increased with the modification of the vapor annealing method. A low temperature vapor annealing technique was developed in which the annealing occurs at 2 °C. In another strategy, polystyrene and poly(2-vinyl pyridine) homopolymers were nanopatterned with alternating lines and grooves with widths between 200 nm and 900 nm and depths between 15 nm to 100 nm using Thermal Nanoimprint Lithography. Poly(2-vinyl pyridine) films were synthesized as brushes using surface initiated Atom Transfer Radical Polymerization to produce robust polymer films. The chemical and/or the topographical heterogeneity of the polymer surfaces influenced the settlement of Ulva linza algae zoospores. Overall, the incorporation of nanoscale features enhanced the antifouling properties of the samples. Further exploration of these types of coatings is highly encouraged.

Marine biofouling is the accumulation of marine species on surfaces submerged in seawater leading to unwanted problems for man-made surfaces such as hulls of ships and aquaculture nets. Historically, the amount of biofouling was regulated using metal based coatings whose usage have been disused lately due to adverse toxic effects. Alternative environmentally friendly coatings are currently avidly being pursued. Nanopatterned polymer thin films were investigated as potential candidates for marine antifouling coatings. Polystyrene-block-poly(2-vinyl pyridine) and polystyrene-block-poly(methyl methacrylate) diblock copolymer thin films self-assembled using vapor solvent annealing into cylinders perpendicular to the substrate composed of poly(2-vinyl pyridine) or poly(methyl methacrylate) respectively with diameters between 30 nm to 82 nm and center-to-center spacing between 46 nm to 113 nm in a polystyrene matrix on various substrates such as silicon or nylon. Polystyrene-block-poly(2-vinyl pyridine) copolymers were also mixed with the photoinitiator benzophenone and irradiated with ultraviolet light to crosslink the polymer chains and decrease the surface hydrophobicity. In the case of polystyrene-block-poly(methyl methacrylate), the yield of these nanopatterned films increased with the modification of the vapor annealing method. A low temperature vapor annealing technique was developed in which the annealing occurs at 2 °C. In another strategy, polystyrene and poly(2-vinyl pyridine) homopolymers were nanopatterned with alternating lines and grooves with widths between 200 nm and 900 nm and depths between 15 nm to 100 nm using Thermal Nanoimprint Lithography. Poly(2-vinyl pyridine) films were synthesized as brushes using surface initiated Atom Transfer Radical Polymerization to produce robust polymer films. The chemical and/or the topographical heterogeneity of the polymer surfaces influenced the settlement of Ulva linza algae zoospores. Overall, the incorporation of nanoscale features enhanced the antifouling properties of the samples. Further exploration of these types of coatings is highly encouraged.

Biofouling pests, including non-indigenous species, can have significant impacts on anthropogenic activities. This is particularly true for aquaculture industries, where biofouling communities grow on crop species and infrastructure, potentially reducing revenue and increasing processing and production costs. It is of interest to marine farmers and scientists to gain a better understanding of the processes facilitating the regional proliferation and spread of biofouling pests. The structure of biofouling communities associated with marine farms in New Zealand’s main mussel growing region, Pelorus Sound, are characterised in this thesis. The patterns of connectivity and gene flow among biofouling populations are also investigated. Images and video footage of biofouling on mussel farms (Perna canaliculus) indicate strong spatial variation in the structure of biofouling communities, with a dominance of known problematic taxa and high wave energy tolerant species, such as the brown alga Undaria pinnatifida and the calcareous tubeworm Pomatoceros sp., near the entrance of Pelorus Sound. Genetic analyses and simple GIS-based modelling of a case study biofouling organism, Didemnum vexillum, revealed genetic differentiation among populations with extreme outcrossing and low levels of connectivity. Genetic analyses also suggest that anthropogenic-assisted dispersal may be vital for connecting certain D. vexillum populations compared to natural spread. The present study illustrates how multidisciplinary research approaches can be used to identify geographical areas that are less prone to biofouling and to inform the management of biofouling pests and invasive species in aquaculture environments.

The objective of this study was to identify and characterize naturally-occurring communities of Bacteria and Fungi fouling the surfaces of concrete structures in Georgia, USA, through the use of culture-independent and culture-dependent approaches. Genomic DNA was extracted and ribosomal RNA genes were PCR amplified from 4 biofouled sites located in or around the cities of Atlanta, Gainesville, LaGrange, and Savannah. Bacterial and fungal community composition was determined by phylogenetic analysis. Molecular analysis revealed five bacterial phyla, and representatives of the phylum Cyanobacteria and the classes Betaproteobacteria and Gammaproteobacteria dominated the bacterial clone libraries. Fungal clone libraries showed the dominant phylotypes to be most closely related to Alternaria, Cladosporium, Epicoccum and Udeniomyces. Phylogenetically distinct microbial populations were present at each of the biofouled sites. In addition, cultured isolates were obtained from sites and tested for their ability to foul concrete of varied compositions under laboratory-controlled conditions. Biofouling tests revealed that fungal isolates obtained from the field were able to colonize concrete surfaces when supplied with moisture (95-100% relative humidity) and a nutrient source, and that fouling was affected by concrete water/cement ratio, surface roughness, and the presence of photocatalytically-activated cement added to inhibit microbial growth.

Surfaces submerged in marine environments rapidly get colonized by marine organisms, a process known as biofouling. Fouling costs maritime industries billions of dollars annually. The most common methods of combating marine biofouling are toxin containing antifouling coatings which often have detrimental non-target environmental effects. These effects and proposed bans on harmful substances in antifouling coatings, mandates development of more environmentally friendly antifouling technologies. Of these, foul-release coatings, which minimize attachment and adhesion of fouling organisms (rather than killing them) are promising alternatives. Here I explored the utility of petroleum waxes as novel antifouling/foul-release coatings. I first investigated the responses of propagules (larvae or spores) of six common fouling organisms to wax coatings in the laboratory. A wide variation in the response of these different organisms, and in the different types of response (settlement, adhesion, etc.) by the same organism, was observed, but the most inhibitory coatings were those made from microcrystalline wax and silicone oil. However, in field trials in Sydney Harbour, paraffin waxes had the strongest antifouling performance, with activity up to one year (the trial duration). These waxes also had strong foul-release effects, with fouling that did attach mostly removed by a low pressure water jet. Composition of fouling communities on paraffin waxes differed significantly from other waxes or controls, with little or no hard fouling organisms (barnacles, bivalves) on paraffin. The mechanisms of antifouling and foul-release actions of paraffin waxes appear to be due to changes in surface properties. The surfaces of the paraffin waxes changed noticeably after 4 - 8 weeks immersion in the sea or in seawater aquaria. Antibiotic treatments showed that this change in surface appearance was due to biological (microbial) activity. Bacteria appear to remove the amorphous phase from the surface of the paraffin waxes, revealing an underlying crystalline phase, which is less affected by bacterial action. I suggest that these crystals form a microstructured ?bed of nails? of crystals of varying shapes and sizes which inhibit settlement and reduce adhesion strength of those organisms which do settle.

abstract: Drinking water filtration using reverse osmosis (RO) membranes effectively removes salts and most other inorganic, organic, and microbial pollutants. RO technologies are utilized at both the municipal and residential scale. The formation of biofilms on RO membranes reduces water flux and increases energy consumption. The research conducted for this thesis involves In-Situ coating of silver, a known biocide, on the surface of RO membranes. This research was adapted from a protocol developed for coating flat sheet membranes with silver nanoparticles, and scaled up into spiral-wound membranes that are commonly used at the residential scale in point-of-use (POU) filtration systems. Performance analyses of the silver-coated spiral-wound were conducted in a mobile drinking water treatment system fitted with two POU units for comparison. Five month-long analyses were performed, including a deployment of the mobile system. In addition to flux, salt rejection, and other water quality analyses, additional membrane characterization tests were conducted on pristine and silver-coated membranes. For flat sheet membranes coated with silver, the surface charge remained negative and contact angle remained below 90. Scaling up to spiral-wound RO membrane configuration was successful, with an average silver-loading of 1.93 g-Ag/cm2. Results showed the flux of water through the membrane ranged from 8 to 13 liters/m2*hr. (LMH) operating at 25% recovery during long-term of operation. The flux was initially decreased due to the silver coating, but no statistically significant differences were observed after 14 days of operation (P < 0.05). The salt rejection was also not effected due to the silver coating (P < 0.05). While 98% of silver was released during long-term studies, the silver release from the spiral-wound membrane was consistently below the secondary MCL of 100 ppb established by the EPA, and was consistently below 5 ppb after two hours of operation. Microbial assays in the form of heterotrophic plate counts suggested there was no statistically significant difference in the prevention of biofouling formation due to the silver coating (P < 0.05). In addition to performance tests and membrane characterizations, a remote data acquisition system was configured to remotely monitor performance and water quality parameters in the mobile system. / Dissertation/Thesis / Masters Thesis Engineering 2017

Microorganisms attachment to the surfaces located in the marine water has become a significant problem. Historically, the antifouling properties of the coatings were achieved by using biocides, which had a negative consequence to the marine environment. Currently, alternative environmental friendly methods are required. This thesis aimed to investigate and produce the antifouling coatings that can be used as potential candidates in the marine industry. In this study, a range of novel polymer nanocomposite coatings was fabricated via the method of solvent and tested based on the strategy of microbial adhesion. The composition of the coatings mainly contains polidimethylsiloxane (PDMS) and different nanomaterials. The coatings applied on glass substrate were characterised using X-ray spectroscopy (XRD), scanning electron microscopy (SEM), contact angle measurements, inductively coupled plasma mass spectroscopy (ICP-MS) and atomic force microscopy (AFM). In biofouling assays, attachment of bacteria B. Subtilis and three marine microalgae (Skeletonema sp., Amphora sp., D. Salina) was investigated in laboratory scale. The obtained results suggested that small amount of nanoparticles in the polymer matrix can improve the antifouling settlement behaviour of the coatings. All microalgae attached more on PDMS/SiO2 and control surfaces (glass and PDMS) compared to the coatings containing multiwall carbon nanotubes (MWCNT) and sodium bismuth titanate (NBT). The influence of contact time, surface roughness and surface wettability was also studied. The microbial attachment varied significantly with respect to contact time and surface properties. There was no obvious evidence showing that the wetting properties and the roughness of the coatings have an effect on growth ... [cont.].

Currently, the most utilized desalination technology is reverse osmosis (RO), where a membrane is used as a physical barrier to separate the salts from the seawater, using high hydraulic pressure as driving force. A major problem in RO systems is biofouling, caused by severe growth of bacterial biofilms. Both, the need of an external energy input, as well as biofouling, impose a high cost on RO operation. Forward osmosis (FO) is an alternative membrane process that uses an osmotic pressure difference as driving force. FO uses a concentrated draw solution to generate high osmotic pressure, which extracts water across a semi permeable membrane from a feed solution. One of the main advantages of FO is the limited amount of external energy required to extract water from the feed solution. The objective of this research is the assessment of the impact of spacers, separating the membrane sheets, and biofouling on the FO system performance. This type of studies allow the optimization of membrane devices and operational conditions. For this, a two dimensional numerical model for FO systems was developed using computational fluid dynamics (CFD). This model allowed the evaluation of the impact of (i) spacers and (ii) biofilm, and (iii) the combined impact of spacers and biofilm on the performance of FO systems. The results obtained showed that the presence of spacers improved the performance of FO systems. Cavity configuration spacer gave the higher water flux across the membrane in clean systems; whereas for biofouled systems, the submerged configuration showed a better performance. In absence of spacers, the thickness or amount of biofilm is inversely proportional with the water flux. Furthermore, membrane surface coverage of the biofilm is more important than the amount of biofilm in terms of the impact on the performance. The numerical model can be adapted with other parameters (e.g. membrane and spacer thickness, feed and draw solution, solution concentration, etc.) to predict the impact of biofilm on FO systems under different experimental conditions. The use of numerical modeling may contribute to faster development of economic viable FO based desalination systems.