Atmospheric corrosion indoors is of great practical importance for the degradation of metals, for example in electronics, military equipment, and cultural heritage items. It involves a wide range of chemical, electrochemical, and physical processes occurring in gas, liquid, and solid phases, and at the interfaces between them. Hence, a molecular understanding of the fundamental interactions during atmospheric corrosion is of utmost importance. Copper is one of the most used metals in electrical contacts, power generators, heat exchangers, etc. and is prone to indoor atmospheric corrosion. Although corrosion and oxidation of copper in the presence of corrosion stimulators is thermodynamically inevitable, there are ways to reduce the kinetics of corrosion and oxidation reactions. Self assembled monolayers (SAMs) of organic molecules, when adsorbed on copper surfaces, have proven to be efficient barriers against copper corrosion. However, understanding at the molecular level of the initial stages of corrosion of SAM covered copper in atmospheric corrosion conditions is lacking. The main reason is the inability of the conventional analytical methods to detect and characterize very thin corrosion products formed during the initial stages (from seconds to days) of atmospheric corrosion of SAM covered copper. To overcome this situation a highly surface sensitive technique, vibrational sum frequency spectroscopy (VSFS), has been utilized in situ and ex situ in this thesis to detect and follow the oxidation of alkanethiol SAM covered copper in dry air as well as to assess the conformational changes of SAM molecules during oxidation.  A very sensitive gravimetric method, quartz crystal microbalance with dissipation monitoring (QCM-D), and a highly sensitive and versatile optical technique, nanoplasmonic sensing (NPS), were combined in situ with VSFS to quantify this very slow oxidation process. This combination allowed the heterogeneity of the oxidation process as well as the mass and the rigidity of the corrosion products to be detected simultaneously. To address indoor atmospheric corrosion conditions where carboxylic acids play an important role we next studied the interaction between SAM covered copper and humidified air, to which formic acid was added. The in situ identification of the corrosion products and their formation kinetics was done using near surface sensitive infrared reflection/absorption spectroscopy (IRAS), and the effect of hydrocarbon chain length in alkanethiol SAMs on their corrosion protection efficiency was investigated. The effect of the anchoring group in the SAMs on their corrosion protection efficiency was studied for hexaneselenol using -SeH as the anchoring group, and the results were compared with its thiol counterpart, hexanethiol, with -SH as the anchoring group. Complementary in situ and ex situ VSFS measurements were performed to assess the quality of the SAMs before, during, and after exposure. It was shown that the SAMs of alkanethiols greatly inhibited the formation of copper (I) oxide and slowed down the formation of other corrosion products, i.e. copper formate and copper hydroxid. This was due to a selective hindrance of the corrosion stimulators, oxygen, water, and formic acid molecules reaching the copper-SAM interface. The corrosion inhibiting effect increased with the hydrocarbon chain length. The SAMs of hexaneselenols, on the other hand, exhibited an accelerated formation of copper (I) oxide, copper formate and copper hydroxide compared to an unprotected surface as a result of the partial removal of hexaneselenol molecules from the copper surface during prolonged exposure. The experience gained in characterizing and quantifying thin copper oxides was further used to explore the influence of gamma (γ) radiation on copper corrosion in anoxic water. This multi-analytical approach included IRAS, cathodic reduction, confocal Raman microscope, atomic force microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, and inductively coupled plasma - atomic emission spectroscopy. The results clearly showed that copper dissolution as well as the oxide layer thickness increase with gamma radiation under the exposure conditions. / Atmosfärisk korrosion under inomhusförhållanden är av stor praktisk betydelse på grund av dess inverkan på exempelvis vårt kulturarv i museimiljöer, tillförlitligheten hos elektronik i olika industriella sammanhang, eller militär utrustning förvarad i olika förråd. Den atmosfäriska korrosionen styrs av ett brett spektrum av kemiska, elektrokemiska och fysikaliska processer som äger rum i tre faser: atmosfären, den tunna fuktfilmen på objektytan och den fasta fasen, samt i de bägge fasgränserna mellan de tre faserna. För att kunna hitta motmedel mot korrosionen är det av yttersta vikt att öka den molekylära förståelsen för dessa processer. Koppar är en mycket använd metall i elektriska eller elektroniska komponenter, i värmeväxlare eller VVS-sammanhang, som beslag och i en rad olika dekorer. Metallen korroderar eller oxiderar spontant i många korrosiva miljöer, men det finns ett brett spektrum av metoder för att minska korrosions- eller oxidationshastigheten. Monoskikt av tätpackade självassocierande organiska molekyler (engelska: self assembled monolayers, förkortat SAM) adsorberade på kopparytan har visat sig vara effektiva barriärer för kopparkorrosion. Den molekylära insikten i dessa monoskikts funktionssätt för att minska den atmosfäriska korrosionen är dock ännu rätt så begränsad. Den främsta orsaken är oförmågan hos mer etablerade analytiska metoder att kunna karakterisera de ytterst små mängder av korrosionsprodukter som bildas under den atmosfäriska korrosionens inledande skeenden upp till några dagars exponering. Den extremt ytkänsliga och i korrosionssammanhang fortfarande relativt oprövade analysmetoden summafrekvensspektroskopi (engelska: vibrational sum frequency spectroscopy, förkortat VSFS) har därför använts för att under pågående exponering följa det mycket långsamma oxidationsförlopp som uppstår när koppar, skyddat av något organiskt monoskikt, exponeras för torr luft. VSFS har även kunnat användas för att under pågående oxidation följa strukturella förändringar hos monoskiktet. För att kvantifiera en så långsam oxidationsprocess har även en annan extremt masskänslig metod kunnat kombineras med VSFS, en kvartskristallmikrovåg med s.k. dissipationsövervakning, förkortat QCM-D. Ytterligare en i korrosionssammanhang oprövad men lika masskänslig teknik har kunnat kombineras med VSFS. Den metoden besitter än så länge bara ett engelskt namn, nanoplasmonic sensing (NPS). Kombinationen VSFS–QCM-D–NPS har utnyttjats i en serie unika försök, där inte bara de ytterst långsamma oxidationshastigheterna kunnat mätas upp, utan även andra viktiga faktorer såsom graden av heterogenitet i den bakomliggande oxidationsprocessen. För att närma sig en miljö som kan efterlikna korrosiva inomhusförhållanden har atmosfären i nästa steg befuktats och dessutom har låga halter av myrsyra tillsats. Just tillsatsen av karboxylsyror har visat sig generera korrosionsprodukter med en sammansättning som på koppar och vissa andra metaller efterliknar de som bildas under atmosfärisk korrosion inomhus. Identifiering av korrosionsprodukter och deras tillväxthastighet på koppar, skyddat av olika långa tätpackade kolkedjor med en tiolgrupp i ena ändan som binder till kopparsubstratet, har kunnat ske med infraröd reflektions-absorptionsspektroskopi (IRAS) under in situ-förhållanden. Ju längre kolvätekedjor desto större korrosionsinhibieringsförmåga kunde påvisas. När den på koppar förankrade tiolgruppen ersattes med en selenolgrupp blev korrosionsinhibieringsförmågan sämre. Kompletterande mätningar in situ och ex situ  utfördes med hjälp av VSFS för att undersöka kvaliteten på de tätpackade kolvätekedjorna, varvid kunde påvisas att graden av tätpackning hos kolkedjorna försämrades med ökad exponeringstid. Förutom den allmänna nedbromsningen av korrosionshastigheten på koppar blev sammansättningen av bildade korrosionsprodukter på oskyddat koppar en annan än på  koppar skyddat av tioler. I det förra fallet detekterades korrosionsprodukterna koppar(I)oxid, koppar(II)format och koppar(II)hydroxid, under det att ingen koppar(I)oxid påvisades på skyddat koppar, endast små mängder koppar(II)format och koppar(II)hydroxid kunde detekteras. De adsorberade kolkedjorna tycks hindra de korrosionsstimulerande molekylerna vatten, myrsyra och syrgas från att nå kopparytan lika effektivt. När de tiolförankrade kolvätekedjorna ersattes med selenolförankrade kolvätekedjor desorberades en del kolvätekedjor från kopparsubstratet vid längre exponeringstider. Resultatet blev att mängden korrosionsprodukter nu blev signifikant större än på oskyddat koppar, sannolikt på grund av galvanisk korrosion. Erfarenheterna från detta doktorsarbete vad gäller kvantifiering av små mängder kopparoxider har även utnyttjats för att undersöka inverkan av g-strålning på kopparkorrosion i rent vatten. Härvid användes ett multianalytiskt angreppssätt bestående av IRAS, katodisk reduktion, konfokal Ramanmikroskopi, atomkraftsmikroskopi, svepelektronmikroskopi, fotoelektronspektroskopi, samt analys av utlöst mängd koppar i vattenlösningen med induktivt kopplad plasmaatomemissionsspektroskopi. Resultaten visar tydligt att utlösningen av koppar, liksom det bildade oxidskiktets tjocklek, ökar med g-strålningen under rådande exponeringsförhållanden. / <p>QC 20131206</p>

The cost of deconstructing cellulose into soluble sugars is a key impediment to the commercial production of lignocellulosic biofuels. The use of the quartz crystal microbalance (QCM) to investigate reaction variables critical to enzymatic cellulose hydrolysis is investigated here, extending previous studies of fungal cellulase activity for the first time to whole cell cellulases. Specifically, the activity of the cellulases of Clostridium thermocellum, which are in the form of cellulosomes, was investigated. To clearly differentiate the activity of free cellulosome and cell-bound cellulosome, the distribution of free cellulosome and cell-bound cellulosome in crude cell broth at different growth stages of C. thermocellum (ATCC 27405) was quantified. Throughout growth, greater than 70% of the cellulosome in the crude cell broth was unattached to the cell. The frequency response of the QCM was shown to capture adsorption and hydrolysis of amorphous cellulose films by the whole-cell cellulases. Further, both crude cell broth and free cellulosomes were found to have similar inhibition pattern (within 0 - 10 g/L cellobiose). Thus, kinetic models developed for the cell-free cellulosomes, which allow for more accurate interfacial adsorption analysis by QCM than their cell-attached counterparts, may provide insight into hydrolysis events in both systems.

Amostras com pequenos volumes e matrizes complexas, como sistemas biológicos, necessitam de preparação criteriosa. Muitas dessas amostras são melhor analizadas em estruturas miniaturizadas devido à necessidade de detectar células e microorganismos em diferentes matrizes. Por essa razão, equipamentos capazes de detectar e destruir microorganismos e estruturas para prévia retenção desses se faz necessários na vida moderna. Chicanas, constrições usadas para reduzir velocidade de fluxo, que podem ser utilizadas para reter compostos, são estruturas macroscópicas para remover resíduos de lagos, fazendas e etc. e chicanas miniaturizadas foram usadas para a adsorção de compostos orgânicos do ar e da água. Assim, esse trabalho tem dois diferentes objetivos: 1) Produção de um equipamento de baixo custo, para teste de partículas ou eliminação de microorganismos e 2) O desenvolvimento de estruturas miniaturizadas para retenção e/ou seleção de partículas e substâncias viscosas de um fluido líquido. A metodologia utilizada foi: 1) Dois software foram escolhidos para esse trabalho. O LabVIEW® 7.0 foi utilizado como plataforma para o desenvolvimento do software do equipamento e o FemLAB® 3.1 para a simulação de estruturas. O equipamento produzido usou Microbalança de Quartzo como detector e um sistema de admissão baseado em uma bomba e tubos. 2) O desenho da estrutura foi otimizado por simulação do comportamento do fluxo. A estrutura otimizada foi feita desmontável, e usinada em polimetilmetacrilato ? acrílico, com ferramentas convencionais. Acrílico foi usado devido à sua transparência óptica, que permite testes com microsocpia óptica. As simulações consideraram N2 e Água como fluidos gasoso e líquido, respectivamente. Avaliou-se o comportamento das partículas (50?m and 13?m) em fluxo gasoso e polidimetilsiloxano (silicone, com viscosidade de 350 cSt) e partículas em fluxo líquido. As estruturas foram caracterizadas quanto à adsorção e retenção de partículas usando equipamento desenvolvido e por microscopia óptica. As estruturas foram, também, continuamente fotografadas durante a execução do experimento e fotos foram utilizadas para determinar o comportamento do fluxo. Os reagentes foram injetados na estrutura em pequenos pulsos. O equipamento mostrou boa performance para detecção de adsorção em fluxo líquido e reprodutibilidade no monitoramento do aquecimento de estruturas. As chicanas mostraram boa capacidade de reter partículas grandes (50?m), mas não pequenas (13?m), tanto para fluxos gasosos como líquidos. Contudo, a estrutura tem pequena capacidade de carga para fluidos líquidos (? 1mg); além disso, a retenção de amostras de silicone na estrutura, utilizando fluido líquido, ocorreu devido à diferença de velocidade entre os fluidos. A simulação e os resultados experimentais apresentam boa correlação. Assim, a chicana mostrou a possibilidade de, seletivamente, separar partículas em fluxos gasosos e líquidos ou reter substâncias viscosas em fluxo líquido. Esses resultados apontam para diversas aplicações, como por exemplo, pré-tratamento para análises biológicas e retenção ou eliminação de microorganismos. / Samples with small volume and complex matrix, such as biological systems, require careful preparation. Many of these samples are better analyzed in miniaturized structures owing to the need of detect cells and microorganisms in different arrays. Therefore equipment able to detect and destroy microorganisms and structures to previously retain them are require in the modern life. Chicanes, i.e. constrictions used to reduce flow velocity, can be useful to retain compounds, are macroscopic devices to remove waste removal from lakes, farms, etc. and miniaturized chicane was used to adsorption of organic compounds from air and water. Thus, this work has two different targets: 1) Production of a low-cost equipment useful for tests of particle or microorganisms elimination and 2) The development of miniaturized structures useful for retention and/or selection of particles and viscous substances from a liquid flow. The methodology used was: 1) Two software were chosen to this work. The LabVIEW® 7.0 was used for development of equipment software and FemLAB® 3.1 for structures simulation. The equipment production used Quartz Crystal Microbalance as detector and an admission system based on simple pumps and plumbing. 2) The design of the structure design was optimized using flow simulation. The optimized design was manufactured in poly(methyl methacrylate) -acrylic, with conventional tools. Acrylic was used due to the optical transparency that allows photographic tests and the structures can be easily disassembled. The simulations considered nitrogen and water for gaseous and liquid flow, respectively. It was evaluated the behavior of particles (50?m and 13?m) on gaseous flow and polydimethylsiloxane (silicone, viscosity of 350 cSt) and particles on liquid flow. The structures were characterized using equipment produced to measure adsorption and optical microscopy to evaluate particle retention. The structures were also continuously photographed during the experiments and the photos were analyzed to determine flow behavior. The reactants were inserted in the structure in small pulses. The equipment shows good performance for detection of adsorption in liquid flows and reproducibility on monitoring heated structures. Chicanes showed good ability to retain big particles (50 ?m) but not small ones (13 ?m) for both liquid and gaseous flow. However, the structure has small load capacity for liquids (? 1 mg). Moreover, the retention of silicone samples in the structure on liquid flow occurs due to the difference in the fluid velocity. The simulation and experimental results are in good agreement and also chicane structure shows the possibility of selectively separate particles from gaseous and liquid flow or retain viscous substances from a liquid flow. These results point out to several applications, such as sample pretreatment for biological analysis and microorganism retention or elimination.

Keratins are important structural components of hair and skin. There has been extensive study of keratins from the health and medical perspectives, although little work has been done to date to investigate their basic physicochemical properties in the form of biomaterials. The work presented in this thesis aimed to study surface and interfacial adsorption and solution aggregation of water soluble keratin polypeptides (made available by previous work within the research group). A range of physical techniques were employed including spectroscopic ellipsometry (SE), neutron reflection (NR), dual polarisation interferometry (DPI), quartz crystal microbalance with dissipation (QCM-D), dynamic light scattering (DLS) and small-angle neutron scattering (SANS).A major technical advantage of the neutron techniques is the use of hydrogen/deuterium substitution to enhance structural resolution. This approach was explored to study the interaction of keratins with both conventional surfactants and novel biosurfactants. The work presented comprises four results chapters. The first examines and compares four widely used interfacial techniques, SE, DPI, QCM-D and NR, by studying the adsorption of C12E6 at the silicon oxide/water interface. Whilst the data exhibits a large degree of consistency in the interfacially adsorbed amount, each technique helped reveal unique structural information with a high degree of complementarity. The second results chapter reports on findings regarding the properties of keratin polypeptides in surface adsorption and solution aggregation. It was found that the keratins adsorbed strongly on the surface of water, and formed rugby-shaped nanoaggregates in solution, the size and shape of which responded to salt concentration. The third results chapter reports on the interfacial behaviour of keratin/surfactants complexes in bulk solution, with cationic DTAB and anionic SDS as model conventional surfactants. It was found that both the electrostatic and hydrophobic forces contributed strongly to the surface adsorption processes. The final results chapter reports on interactions of a coated keratin film with novel biosurfactants including rhamnolipids (R1 and R2 with 1 and 2 sugar head(s), respectively) and Mel-C. The keratin films formed were found to be exceptionally stable and reproducible below pH 8, and these films could be widely used as model keratin substrates for screening their binding with surfactants and bioactive molecules. Both rhamnolipids and Mel-C exhibited strong adsorption onto the keratin substrate and interestingly, whilst R1 exhibited a completely reversible adsorption, R2 showed only a partially reversible adsorption. Mel-C showed some degree of irreversible adsorption similar to R2 and exhibited the strongest adsorption at around pH 4-5. These results show mild interactions with the keratin substrate, but indicate that the extent of adsorption and desorption could be manipulated by surfactant structure or solution conditions. The findings presented in this thesis are fundamental in aiding the development of the use of keratin polypeptides as biomaterials, in applications such as personal care. The work is also highly relevant to the understanding of the interactions between surfactants and keratin molecules at interfaces and in solution.

Healthcare associated infections (HAIs) cost the US healthcare system over $45 billion to treat and cause millions of deaths annually. A large subset of HAIs are associated with medical devices that are meant to improve and save lives. Infected devices are treated using traditional antibiotics, contributing to development of antibiotic resistance. Antibiotic resistance is expected to cost $100 trillion and kill more people a year than cancer by 2050; thus, new alternative antimicrobials for the treatment of device-associated HAIs are critically needed. Antimicrobial peptides (AMPs), such as 26 amino-acid (aa), marine-derived Chrysophsin-1 (CHY1), are poised to reduce HAIs due to their broad antimicrobial activity and unique mechanisms of action that do not promote bacterial resistance. AMPs are short (12-50aa), positively charged (+2-+9) proteins found in the innate immune systems of many different species. Their high separation of hydrophilic and hydrophobic residues leads to many unique mechanisms derived from many unique secondary and tertiary structures that are not yet well understood. Despite the discovery of over 2000 natural AMPs and many more synthetically designed AMPs, none have been successfully commercialized for healthcare applications due to challenges surrounding cytotoxicity, short in vivo half-life (degradation), high costs of production and effectiveness in physiological environments (such as those with high-salt). Several strategies have been investigated to overcome these challenges, for example, truncation of cytotoxic sequences or D-amino acid substitution to improve AMP toxicity and stability; however, many of these strategies can reduce antimicrobial effectiveness. A unique strategy of increasing stability, reducing cytotoxicity, and maintaining antimicrobial activity that is relevant for medical devices is the covalent tethering (binding) of AMPs via a flexible tethering molecule to the surface. However, the effect of tethering parameters on resulting AMP mechanisms and activity is still widely debated. AMP activity can vary widely by utilizing different tethering strategies, which include additional variables such as: (1) peptide choice and properties (such as native mechanism, concentration, charge, and structure), (2) tether choice and properties (such as chemical composition, length, charge, surface density, and flexibility), and (3) testing conditions (such as temperature, solvent composition and substrate type). Some studies suggest that AMP performance may be tether-dependent, for example some AMPs require longer tethers while others do not and some need a flexible tether. Thus, models for predicting successful tethering strategies for different AMP properties, which currently do not exist, must be developed. Further, complicated and often destructive techniques, such as XPS and SEM, are typically implemented to study the relationship of all these parameters vs. antimicrobial activity, which are labor-intensive and limited in scope. Predictive models guiding tether strategy need to be constructed, but also new techniques to study tethering be developed. If these technical milestones are achieved they can serve as a predicate for commercial implementation of a host of new therapies targeted at reducing device-associated HAIs. The overall goal of this thesis was to study the relationship between antimicrobial activity of tethered C-CHY1 examining both spacer length and peptide surface density and the development of a feasible clinical business case for tethered AMPs. To achieve this goal, a traditional entrepreneurial approach was taken in which a minimally-viable product was first designed and business case analyzed, followed by studies to better optimize and understand the underlying structure-mechanism relationships. CHY1 with a C-terminus cysteine to allow for surface-binding (C-CHY1) was tethered onto a silicon dioxide surface via a flexible poly(ethylene glycol) (PEG) tether, and then both surface binding behavior and antimicrobial success of C-CHY1 were examined as a function of tether properties and reaction conditions. For these studies, quartz-crystal microbalance with dissipation (QCM-D) was the primary technique, a real-time, non-destructive flow method that was then coupled with downstream characterization techniques: fluorescent microscopy and contact angle measurements. In parallel a deep dive into domestic and international business models for commercializing AMP technologies. Specifically, tether length and surface density effects on C-CHY1 mechanisms were studied, followed by the effect of temperature, type of microbe, and salt concentration on the antimicrobial mechanisms of tethered C-CHY1. QCM-D was used to measure binding of C-CHY1 via three different length tethers, PEG molecular weight (MW) 866, 2000 and 7500, followed by microscopy to measure antimicrobial effectiveness against two model microbes Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Modeling of QCM-D data allowed for surface density and thickness to be calculated and related to C-CHY1 antimicrobial activity. PEG 7500 allowed proper C-CHY1 orientation and mobility, allowing for its native pore-forming mechanism and highest activity while PEG 866 tethers led to denser grafting and an effective, yet non-native ion displacement mechanism. The QCM-D was used to characterize the effect of salt concentration and temperature reaction conditions on the grafting density of C-CHY1 tethered via PEG 866 and PEG 7500, which was then related to antimicrobial activity. For PEG MW 866, neither temperature nor salt concentration increases significantly altered the grafting density of C-CHY1 while for PEG 7500 increasing temperature allowed for significantly increased grafting density. C-CHY1 density had no significant effect on antimicrobial activity against either microbe. Temperature of bacterial incubation did demonstrate microbe-specific changes in C-CHY1 antimicrobial activity. These results demonstrated that small changes in reaction conditions can drastically change membrane selectivity of C-CHY1. An in-depth investigation of the effects of bacterial membrane composition and temperature on soluble C-CHY1 mechanism was implemented to better understand the molecular membrane- and temperature-dependent selectivity and structure-function of C-CHY1. Supported lipid bilayers (SLBs) formed in QCM-D can be used as model membranes to elucidate AMP action mechanisms against membranes of different compositions. Two and three component SLBs representative of Gram-negative phosphatidylethanolamine (PE) and phosphatidyglycerol acid (PG) with and without charged lipopolysaccharide, LPS and Gram-positive bacteria phosphatidylcholine (PC) and PG with and without charged lipoteichoic acid, (LTA) were formed at both 23°C and 37°C. C-CHY1 at 5 µM was exposed to the different membranes and mechanistic surface action was studied. The membranes formed highly different baseline responses in QCM-D, indicative of vastly different membrane structures, thicknesses and deposition behaviors on SiO2, warranting future studies. Further, significant effects of LTA incorporation were observed in both peptide interaction and deposition. There were measurable effects of temperature on membrane formation as well as peptide interaction kinetics and even mode of interaction. Lastly, business models for the commercialization of novel medical device technologies such as surface-tethered C-CHY1 were investigated. While this technology has the potential to solve many unmet needs, there must a commercialization plan implemented in order to have an impact. There is a clear disconnect between technology development in academia and technology commercialization in industry that must be connected. Development of an entrepreneurial mindset at the graduate school level, can help bridge the gap. A thorough investigation of domestic and international business models for commercializing AMP technologies was carried out and distilled in the form of the Business Model Canvas developed by Alexander Osterwalder that can be used as a roadmap for commercialization efforts. Using the QCM-D a relationship between both spacer length and peptide surface density and the antimicrobial activity of tethered C-CHY1 was determined. A business plan was developed in order to increase the impact of this and other AMP based work. This work provides a roadmap for future researchers to quickly develop and commercial novel AMP based coating technology.

In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.

The report deals with the study of the resistence of the nonporous polymer materiále against permeation of the selected TICs, with the analysis of the running difussion processes and utilization of the acquired results for the selection of suitable barrier materials for the protective means.

Healthcare associated infections (HAIs) cost the US healthcare system over $45 billion to treat and cause millions of deaths annually. A large subset of HAIs are associated with medical devices that are meant to improve and save lives. Infected devices are treated using traditional antibiotics, contributing to development of antibiotic resistance. Antibiotic resistance is expected to cost $100 trillion and kill more people a year than cancer by 2050; thus, new alternative antimicrobials for the treatment of device-associated HAIs are critically needed. Antimicrobial peptides (AMPs), such as 26 amino-acid (aa), marine-derived Chrysophsin-1 (CHY1), are poised to reduce HAIs due to their broad antimicrobial activity and unique mechanisms of action that do not promote bacterial resistance. AMPs are short (12-50aa), positively charged (+2-+9) proteins found in the innate immune systems of many different species. Their high separation of hydrophilic and hydrophobic residues leads to many unique mechanisms derived from many unique secondary and tertiary structures that are not yet well understood. Despite the discovery of over 2000 natural AMPs and many more synthetically designed AMPs, none have been successfully commercialized for healthcare applications due to challenges surrounding cytotoxicity, short in vivo half-life (degradation), high costs of production and effectiveness in physiological environments (such as those with high-salt). Several strategies have been investigated to overcome these challenges, for example, truncation of cytotoxic sequences or D-amino acid substitution to improve AMP toxicity and stability; however, many of these strategies can reduce antimicrobial effectiveness. A unique strategy of increasing stability, reducing cytotoxicity, and maintaining antimicrobial activity that is relevant for medical devices is the covalent tethering (binding) of AMPs via a flexible tethering molecule to the surface. However, the effect of tethering parameters on resulting AMP mechanisms and activity is still widely debated. AMP activity can vary widely by utilizing different tethering strategies, which include additional variables such as: (1) peptide choice and properties (such as native mechanism, concentration, charge, and structure), (2) tether choice and properties (such as chemical composition, length, charge, surface density, and flexibility), and (3) testing conditions (such as temperature, solvent composition and substrate type). Some studies suggest that AMP performance may be tether-dependent, for example some AMPs require longer tethers while others do not and some need a flexible tether. Thus, models for predicting successful tethering strategies for different AMP properties, which currently do not exist, must be developed. Further, complicated and often destructive techniques, such as XPS and SEM, are typically implemented to study the relationship of all these parameters vs. antimicrobial activity, which are labor-intensive and limited in scope. Predictive models guiding tether strategy need to be constructed, but also new techniques to study tethering be developed. If these technical milestones are achieved they can serve as a predicate for commercial implementation of a host of new therapies targeted at reducing device-associated HAIs. The overall goal of this thesis was to study the relationship between antimicrobial activity of tethered C-CHY1 examining both spacer length and peptide surface density and the development of a feasible clinical business case for tethered AMPs. To achieve this goal, a traditional entrepreneurial approach was taken in which a minimally-viable product was first designed and business case analyzed, followed by studies to better optimize and understand the underlying structure-mechanism relationships. CHY1 with a C-terminus cysteine to allow for surface-binding (C-CHY1) was tethered onto a silicon dioxide surface via a flexible poly(ethylene glycol) (PEG) tether, and then both surface binding behavior and antimicrobial success of C-CHY1 were examined as a function of tether properties and reaction conditions. For these studies, quartz-crystal microbalance with dissipation (QCM-D) was the primary technique, a real-time, non-destructive flow method that was then coupled with downstream characterization techniques: fluorescent microscopy and contact angle measurements. In parallel a deep dive into domestic and international business models for commercializing AMP technologies. Specifically, tether length and surface density effects on C-CHY1 mechanisms were studied, followed by the effect of temperature, type of microbe, and salt concentration on the antimicrobial mechanisms of tethered C-CHY1. QCM-D was used to measure binding of C-CHY1 via three different length tethers, PEG molecular weight (MW) 866, 2000 and 7500, followed by microscopy to measure antimicrobial effectiveness against two model microbes Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Modeling of QCM-D data allowed for surface density and thickness to be calculated and related to C-CHY1 antimicrobial activity. PEG 7500 allowed proper C-CHY1 orientation and mobility, allowing for its native pore-forming mechanism and highest activity while PEG 866 tethers led to denser grafting and an effective, yet non-native ion displacement mechanism. The QCM-D was used to characterize the effect of salt concentration and temperature reaction conditions on the grafting density of C-CHY1 tethered via PEG 866 and PEG 7500, which was then related to antimicrobial activity. For PEG MW 866, neither temperature nor salt concentration increases significantly altered the grafting density of C-CHY1 while for PEG 7500 increasing temperature allowed for significantly increased grafting density. C-CHY1 density had no significant effect on antimicrobial activity against either microbe. Temperature of bacterial incubation did demonstrate microbe-specific changes in C-CHY1 antimicrobial activity. These results demonstrated that small changes in reaction conditions can drastically change membrane selectivity of C-CHY1. An in-depth investigation of the effects of bacterial membrane composition and temperature on soluble C-CHY1 mechanism was implemented to better understand the molecular membrane- and temperature-dependent selectivity and structure-function of C-CHY1. Supported lipid bilayers (SLBs) formed in QCM-D can be used as model membranes to elucidate AMP action mechanisms against membranes of different compositions. Two and three component SLBs representative of Gram-negative phosphatidylethanolamine (PE) and phosphatidyglycerol acid (PG) with and without charged lipopolysaccharide, LPS and Gram-positive bacteria phosphatidylcholine (PC) and PG with and without charged lipoteichoic acid, (LTA) were formed at both 23°C and 37°C. C-CHY1 at 5 µM was exposed to the different membranes and mechanistic surface action was studied. The membranes formed highly different baseline responses in QCM-D, indicative of vastly different membrane structures, thicknesses and deposition behaviors on SiO2, warranting future studies. Further, significant effects of LTA incorporation were observed in both peptide interaction and deposition. There were measurable effects of temperature on membrane formation as well as peptide interaction kinetics and even mode of interaction. Lastly, business models for the commercialization of novel medical device technologies such as surface-tethered C-CHY1 were investigated. While this technology has the potential to solve many unmet needs, there must a commercialization plan implemented in order to have an impact. There is a clear disconnect between technology development in academia and technology commercialization in industry that must be connected. Development of an entrepreneurial mindset at the graduate school level, can help bridge the gap. A thorough investigation of domestic and international business models for commercializing AMP technologies was carried out and distilled in the form of the Business Model Canvas developed by Alexander Osterwalder that can be used as a roadmap for commercialization efforts. Using the QCM-D a relationship between both spacer length and peptide surface density and the antimicrobial activity of tethered C-CHY1 was determined. A business plan was developed in order to increase the impact of this and other AMP based work. This work provides a roadmap for future researchers to quickly develop and commercial novel AMP based coating technology.

Electrochemical quartz crystal microbalance has been employed to investigate electro-responsiveness of an ionic liquid as an additive in lubricant oils on a gold surface. Polarisation of the surface reveals changes in frequency where an increase in magnitude amplified the observed response, corresponding to a controllable alternation of the ionic liquid configuration on the surface as a function of applied potential. The frequency changes are due to different packing of the anion and cation, respectively, on the surface as their mass densities and geometries are different. Relaxation of the system was reversible to the application of a potential and it was also found to be diffusion dependent, where the ratio between the ion diffusivities could be extracted from the results. Measurement of the system relaxation reveals a potential decay of that of a discharging capacitor, with an internal resistance inducing an initial potential drop due to the resistivity of the oil medium. The discharge behaviour was also proven to show high internal reproducibility validity within experiments. This newly discovered insight in responsive differences of ion packing is of importance, not only for ionic liquid additives in tribology, but for understanding and exploiting ionic liquids in an array of electrochemical applications.

In this study a biosensor based on real time quartz crystal microbalance (QCM) monitoring is optimized and characterized for the application in the Norosensor. This biosensor is aimed to recognise, capture and amplify Norovirus (NoV). In an initial step a simplified bioassay was developed that focuses on the latter parts of the assay which consists of DNA-guided probing and amplification of the captured virus and includes the development of an amplification model assay directly to the functionalised crystal surface. A padlock probe with matching sequence to the conjugated oligonucleotide on the quartz crystal surface is used as target in the model assay. Although a number of studies have been carried out based on padlock probe ligation and rolling circle amplification (RCA) based QCM sensing, these studies utilize the entire crystal surface to capture and amplify the biomolecule. In this research work the QCM monitoring is explored on a centrally functionalised electrode surface through conjugation only at the centre of the electrode for increased mass sensitivity. Thus, allowing capture and amplification of the padlock probe only at the centre of the quartz crystal. A 14mm diameter, thermoncompensated AT-cut, nonpolished quartz crystal with a 10mm diameter gold surface coating acting as electrode was utilized for QCM measurements. The detection system is based on mass binding and amplification on the QCM to produce a negative frequency shift in the fundamental frequency of the vibrating quartz crystal. The amplification products were additionally fluorescently labelled and fluorescent microscopy images were also obtained at the end of every experiment to verify the presence or absence of DNA capture and amplification. Experimental findings show that the current flow chamber with a 15ul capacity is able to detect a specific padlock probe concentration of 1nM on a conjugated region of ~2.5mm diameter. RCA amplified the mass with an average frequency shift of -80Hz in 60mins RCA incubation time. Further, the specificity and sensitivity of the QCM system was explored. However, the system has limitations where sensor binding of reaction proteins, such as DNA ligase and BSA, to some extent is observed. The storage stability of the functionalized self-assembled monolayer (SAM) on the QCM is also observed to deteriorate and thus, is of concern. Nevertheless the combination of RCA based amplification with QCM real-time monitoring has the potential for rapid and simple, low cost detection of the Norovirus. / I det här arbetet har vi optimerat och karateriserat en biosensor för detektion av Norovirus som orsakar häftiga utbrott av kräksjuka under vinterhalvåret vilket leder till både försämrad vård samt stora ekonomiska förluster för samhället. Målet inom EU projektet “Norosensor” är att utveckla ett snabbtest som kan tillämpas efter ett utbrott på till exempel en vårdavdelning och som ska mäta mängden virus i luften vilket kan fungera som riktlinje för om en avdelning är säker att användas eller ej. Tekniskt är målet med testet att fånga in viruspartiklar från luften som specifikt binds till sensorytan. Därefter ökar vi känsligheten från bundna partiklar genom en DNA-baserad amplifiering. Detta genererar specifik, viruskorrelerad massa som mäts med en kvartskristall mikrovågs sensor. När massan ökar minskar frekvenser vid vilken kristallen vibrerar och detta mäts i realtid. Det här arbetet har inte behandlat infångande eller inbindning av virus utan har fokuserat på den senare delen av protokollet som omfattar amplifieringen på sensorytan. En modell-assay har därför utvecklats där viruspartikeln istället representeras av en så kallad “padlock probe” (hänglås probe). Då sensorn är mycket känslig har först olika protokoll testats för effektiv rengöring av ytan med hjälp av ultraljud. I nästa steg har ytan funktionaliserats med thiol-modifierade syntetiska DNA molekyler som används för infångningen av målmolekylen på sensorytan (virus eller i detta fall padlock proben). Det har tidigare uppskattats att för att få maximal känslighet i massmätningen så är det fördelaktigt att binda viruset endast i mitten på en mycket liten yta av kristallen. Den här avhandlingen har därför fokuserat på att utveckla protokoll för detta där ytan först funtionaliserats i mitten innan resten av ytan blockats för att undvika ospecific inbindning. Resultaten visar att vi kan generera en centrerad funtionalisering och att vi får låg ospecifik binding. Protokollet består av flera biokemiska reakionssteg såsom (i) inbindning och lingering av padlock probe och (ii) amplifiering av den ligerade proben genom “rolling circle amplification”. För att kunna verifiera att vi fått amplifieringsprodukter på ytan har vi dels mätt frekvensändringen på grund av ökad massa men också märkt in dem med fluorescerande molekyler och detekterat dem i microskop. Under arbetets gång har ett flertal olika typer av kristaller testats. Det visade sig att om en polerad yta används (1μm grovhet) så migrerade molekylerna iväg från mitten när vi oscillerade kristallen medan vi fick bättre resultat om något grövre (3μm) ytor användes. Vi testade även ett flertal olika flödesceller av olika material och med olika reaktionsvolymer. Eftersom kristallen är mycket känslig så påverkar faktorer som flödeshastigheter och eventuella luftbubblor frekvensen. Vi optimerade därför detta och körde mätningarna vi6konstant flöde men med alternerande, låga hastigheter när vi tillsatte nya reagens eller inkuberade reaktionerna. Vi förvärmde även reaktionsmixarna för att minska ospeficika effekter och konstaterade att den funktionaliserade ytan påverkades av lagring över tid. I våra försök såg vi att protein såsom ligeringsenzymet och albumin, vilka har förhållandevis stor massa, hade effekter på frekvensen redan i sig genom att binda till ytan. Ytterligare optimeringar måste därför göras framöver för att minska denna inbinding bland annat genom bättre tvättsteg. Vi kunde dock påvisa linjär massökning med ökad amplifieringstid och har bevisad hög specificitet. Slutligen utvecklades ett litet mjukvaruprogram för att automatisera analysen och minska bruset. Sammanfattingsvis har vi lyckats utveckla ett enkelt och snabbt system för specifik massamplifering av Norovirus.