The Copper Development Association (CDA) has identified over 450 copper alloys registered with the U.S. Environmental Protection Agency (EPA) as antimicrobial. With growing antibiotic resistance, there is a need for copper coatings with increased antimicrobial capability. Cold spray is a high velocity, high deposition rate process that forms dense coatings with little to no oxides or inclusions. It is possible that this process contributes to the increased antimicrobial capability of copper cold spray coatings as compared to other additive processes. The focus of this effort is to understand the effects of powder production and cold spray process parameters on copper cold spray coatings in order to optimize antimicrobial properties. Specifically, this work looks at the differences in conventional and nanomaterial copper cold spray coatings. Materials characterization and test methods show differences in adhesion, microstructure, corrosion, mechanical properties, and surface topography. Materials data is compared against Abaqus FEA software model outputs, and antimicrobial efficacy test data, based on the EPA approved procedure, is used to support materials observations and modelling outputs.

Antimicrobial coatings in which the active agent (e.g. N-halamine) can regenerate activity represent a promising way to prevent microbial cross-contamination. A reported method for applying coatings containing antimicrobial N-halamines is layer-by-layer (LbL) application of polyelectrolytes, which form N-halamines upon cross-linking. Prior reports on dip layer-by-layer (LbL) fabrication have demonstrated the potential of this coating technology; however, spray LbL fabrication would enable more rapid coating and represents a more commercially translatable application technique. In this work, dip and spray LbL methods were used to coat polypropylene (PP) with N-halamine containing bilayers consisting of cross-linked polyethylenimine (PEI) and poly(acrylic acid) (PAA). Further experimentation with spray LbL fabrication used naturally occurring polyelectrolytes, chitosan and alginate. Materials were characterized using atomic force microscopy (AFM), ellipsometry, contact angle, fourier transform infrared spectroscopy, a chlorine content assay, and a dye assay for amine quantification. All methods of coating application exhibited a 99.999% (5-log) reduction against Listeria monocytogenes with application time for spray LbL taking less than 10% of the time required for dip LbL. Spray LbL fabrication of N-halamines is a rapid and inexpensive method to fabricate rechargeable antimicrobial surfaces.

In this project the factors influencing the stability and antimicrobial activity of allyl isothiocyanate (AITC) against Campylobacter jejuni, Salmonella or Listeria monocytogenes as well as factors that enhance sinigrin (glucosinolate in Oriental mustard) hydrolysis by these pathogens were investigated. The minimum inhibitory concentration (MIC) of AITC against 5 strains of each of Salmonella or L. monocytogenes, ranged from 60-100 ppm at 37 ºC. This was reduced to 10-40 ppm at 21 ºC and a further reduction to 5-10 ppm against strains of L. monocytogenes was observed at 4 ºC. This was attributed to greater stability of AITC as temperature was decreased. C. jejuni strains were more susceptible to AITC with MICs of 0.63-1.25 ppm and 2.5-5 ppm at 37 and 42 ºC, respectively. AITC was more inhibitory at ≤ 21 ºC against Salmonella with acidic pH or against L. monocytogenes with neutral pH. C. jejuni, Salmonella and L. monocytogenes strains and mixtures had the ability to degrade sinigrin to form inhibitory concentrations of AITC, and sinigrin hydrolysis was significantly enhanced by higher incubation temperature (21 ºC > 10 ºC > 4 ºC), the presence of 10 mM ferric or ferrous irons, and the presence of < 0.25% glucose. This project also investigated the antimicrobial activity of AITC or Oriental mustard extract alone or combined with ethylenediamine tetraacetic acid (EDTA), malic acid and acetic acid in edible antimicrobial coatings against C. jejuni and Salmonella on fresh, refrigerated, vacuum-packed chicken breasts or L. monocytogenes on refrigerated, cured roast chicken. Malic acid improved the antimicrobial activity of Oriental mustard extract against L. monocytogenes, while EDTA improved its activity against Salmonella. Incorporation of 25 to 50 µl/g AITC or 100 to 250 mg/g Oriental mustard extract in 0.5%κ-carrageenan/2%chitosan coatings, prepared using 1.5% malic or acetic acid, reduced L. monocytogenes on cooked, cured, vacuum-packed chicken slices 4.2 to > 7.0 log10 CFU/g, compared to uncoated chicken by 70 d at 4 ºC. In addition, 0.2%κ-carrageenan/2%chitosan coatings (prepared using a 1% acetic acid solution) containing 250 mg/g mustard extract or 50 µl/g AITC reduced Salmonella numbers on vacuum-packed chicken breasts 3.0 log10 CFU/g by 21 d at 4 ºC. Further, 0.2%κ-carrageenan/2%chitosan coatings containing 50 or 100 µl/g AITC reduced numbers of C. jejuni on fresh, vacuum-packed chicken breasts > 5.0 log10 CFU/g (C. jejuni cells were not detected) after 5 d storage at 4 ºC, while coatings containing 200 to 300 mg/g Oriental mustard extract or 25 µl/g AITC reduced C. jejuni numbers by 3.6 to 4.6 log10 CFU/g. Numbers of lactic acid and aerobic bacteria on poultry meat products were significantly reduced by the coatings. It is clear that κ-carrageenan/chitosan coatings containing either AITC, mustard extract alone or combined with EDTA, malic or acetic acid significantly reduced C. jejuni and Salmonella on fresh, refrigerated, vacuum-packed chicken breasts and L. monocytogenes on refrigerated, cured roast chicken, and consequently enhanced their safety.

Ces travaux s'appuient sur un contexte de santé lié à la dégradation de la qualité de l'air intérieur induite par la présence de micro-organismes. Dans les environnements intérieurs humides, les matériaux de construction sont des cibles de contamination et de prolifération microbienne importantes. La photocatalyse est un procédé de dépollution qui présente une action contre une large gamme de polluants organiques (aqueux, gazeux ou biologiques). Son principe repose sur l'excitation d'un photocatalyseur par une irradiation lumineuse, généralement située dans les UV, qui va permettre de dégrader les polluants environnants par une succession de réactions d'oxydo-réduction. Le photocatalyseur le plus courant est le dioxyde de titane (TiO2). Outre la production d'espèces oxydo-réductrices agressives, le TiO2 illuminé présente également un caractère super-hydrophile qui lui confère un caractère autonettoyant intéressant. Une autre solution est envisagée pour lutter contre la prolifération microbienne sur matériaux de construction : l'utilisation de molécule bio-sourcées d'ester de glycérol aux propriétés naturellement antimicrobienne. L'objectif de cette étude est de développer des revêtements pour matériaux de construction intérieurs et d'étudier leur propriété de résistance à la prolifération microbienne et les modes d'action de ces dispositifs passifs formulés soit à base de particules de TiO2, soit à base d'ester de gycérol. Dans un premier temps, un travail de développement et de mise en œuvre de dispositifs expérimentaux a été nécessaire afin d'adapter des méthodes d'évaluation microbiologiques sur ces matériaux particuliers (particules, lasures, matériaux cimentaires). Ainsi, plusieurs essais ont été adaptés afin d'évaluer les performances antimicrobiennes en terme (i) d'activité antibactérienne, (ii) d'effet bactéricide, (iii) de résistance à la formation de biofilm et (iv) de résistance à la prolifération par contamination " naturelle ". Les premiers essais visent à mettre en évidence l'impact des facteurs méthodologiques sur l'activité antibactérienne des particules de TiO2 utilisées seules comme agent désinfectant. Dans un deuxième temps, des lasures photocatalytiques sont formulées sur la base de travaux antérieurs ayant montrés de bonnes efficacités de dépollution de l'air contre les NOx, NO et différents COV. Une fois les paramètres d'influence de l'activité du TiO2 mis en exergue, les lasures ont été testées dans des conditions optimales. Le développement d'un essai de résistance à la prolifération de biofilm montre l'importance de coupler différentes méthodes d'évaluation microbiologique (dénombrement des UFC et observation au microscope à épifluorescence). La dernière partie de cette étude explore le potentiel antimicrobien de la molécule d'ester de glycérol, sous-produit de la synthèse de biocarburant. La molécule montre des propriétés antibactériennes et bactéricides puissantes en quelques minutes de contact seulement. Elle présente également une protection très efficace contre la prolifération microbienne une fois recouverte sur matériaux de construction (placo-plâtre). Ces performances remarquables encouragent la poursuite des études sur cette molécule. / This work is included in a health-related context: the degradation of the indoor air quality induced by the presence of microorganisms. In damp environments, indoor building materials are among the main proliferation substrates for microorganisms. Photocatalysis is a decontamination process which is active against a wide range of organic pollutants (aqueous, gaseous or biological). The principle is based on the excitation of a photocatalyst by light irradiation, usually located in the UV-range, which leads to the degradation or mineralization of surrounding pollutants through a series of oxidative reactions. The most common photocatalyst is titanium dioxide (TiO2). In addition to produce aggressive redox species, the illuminated TiO2 also shows super-hydrophilicity, which has an impact on the first step of microbial biofilm formation: the adhesion of microorganisms. Another technology to protect indoor building materials is explored: the use of glycerol esters, which are bio-based molecules with inherent antimicrobial properties. The main objective of this study is to develop semi-transparent coatings for indoor building materials and to study the resistance to microbial growth conferred by these passive devices, which are formulated using TiO2 nanoparticles or glycerol esters. Initially, the development and implementation of experimental devices has been necessary to adapt microbiological evaluation methods to these particular materials (nanoparticles, surface coatings, cementitious materials). Thus, several tests have been carried out in order to assess the antimicrobial performances in terms of (i) antibacterial activity, (ii) bactericidal effect, (iii) resistance to biofilm formation and (iv) resistance to proliferation by "natural" contamination. First tests aimed to underline the influence of methodological parameters on the efficiency of TiO2 particles used alone as antimicrobial agent. Then, semi-transparent coatings were formulated on the basis of previous works which have shown good efficiencies on the depollution of ambient air from NOx, NO and VOC. Once the parameters that influence TiO2 activity were identified, coatings were tested in optimum conditions. The evaluation of the resistance to biofilm formation shows the importance of overlapping different microbiological evaluation methods (e.g. CFU counting and epifluorescence observations). The last part was an exploratory work on the antimicrobial properties of a glycerol ester molecule, by-product from the synthesis of biofuels. The molecule shows potent antibacterial and bactericidal properties, several log of inactivation within only few minutes of contact. It also provides very effective protection against microbial growth once covered on building materials (plasterboard). These remarkable performances encourage further studies on this molecule.

Pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices commonly relies on the performance of animal studies since alternative in vitro models do not adequately represent the interactions between blood, bacteria, and material surfaces as they occur in vivo. To reduce the need of these cost-intensive and controversial animal tests, this project was dedicated to the development of a new model setup that overcomes this limitation and allows in vitro evaluation under in vivo-like conditions. This newly developed model was intended to be directly applied to evaluate recently in-house developed antimicrobial coatings, so-called anchor polymers. Therefore, the project was divided into two parts. The first part of the project focused on the evaluation of the anchor polymer coatings concerning their applicability in blood-contacting devices. For this purpose, the PEGylated styrene-maleic acid copolymers were intensively studied using established laboratory tests. These examinations showed very promising results regarding adsorption and stability on relevant polymer substrates, antimicrobial efficacy, and biological safety of the coatings, thus revealing their great potential for future applications in medical devices. Moreover, this basic characterization was meant to allow a subsequent comparison of the new in vitro model with state-of-the-art in vitro tests. The second part of the thesis focused on the development of the realistic in vitro model. Here, a single-pass flow system realized the implementation of adjustable flow conditions. Furthermore, incubation with freshly drawn human blood provided a physiological nutrient environment and included the influence of an immune response. Staphylococcus aureus were chosen as representative microorganisms, as they are responsible for a majority of device-related blood stream infections. The resulting blood flow model was validated with one anti-adhesive and one contact-killing anchor polymer coating, confirming the model’s ability to differentiate the investigated surfaces. Inflammatory and coagulant blood activation correlated slightly with bacterial coverage, which in turn was strongly dependent on the investigated material surface. Incubation with varying flow conditions demonstrated the model’s capability to reflect the well-documented dependence of bacterial colonization and occurring flow conditions. In contrast to the state-of-the-art in vitro tests, the simultaneous incubation of test surface, bacteria and whole blood allowed the analysis of mutual interactions of the three parameters. Thus, the model represents an excellent method for pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices.