MEMS (Microelectromechanical Systems) acoustic sensors are a promising platform for Point-of-Care biosensing. In particular, piezoelectrically driven acoustic sensors can provide fast results with high sensitivity, can be miniaturized and mass produced, and have the potential to be fully integrated with sample handling and electronics in handheld devices. Furthermore, they can be designed as multiplexed arrays to detect multiple biomarkers of interest in parallel. In order to develop a microfabricated biosensing platform, a specific and high affinity biodetection platform must be optimized, and the microfabricated sensors must be designed to have high sensitivity and maintain good performance in a liquid environment. A biomolecular sensing system that uses high affinity peptide aptamers and a passivation layer has been optimized for the detection of proteins of interest using the quartz crystal microbalance with dissipation monitoring (QCM-D). The resulting system is highly specific to target proteins, differentiating between target IgG molecules and other closely related IgG subclasses, even in complex environments such as serum. Piezoelectrically actuated MEMS resonators are designed to operate in flexural microplate modes, with several modes shown to be ideally suited for fluid based biosensing due to improved performance in the liquid environment. The increase in quality factor of these MEMS microplate devices in liquid, as compared to air, is further investigated through the analytical and finite element modeling of MEMS fluid damping mechanisms, with a focus on acoustic radiation losses for circular microplate devices. It is found that the impedance mismatch at the air-water interface of a droplet is a key contributor to reduced acoustic radiation losses and thus improved device performance in water. Microplate acoustic sensors operating in flexural plate wave and microplate flexural modes are then integrated with a fluidic cell to facilitate protein sensing from fluid samples. Flexural plate wave devices are used to measure protein mass adsorbed to the sensor surface and initial results toward microplate flexural mode protein sensing are presented. Finally, challenges and areas of future research are discussed to outline the path towards finalization of a sensing platform taking advantage of the combination of the sensitive MEMS acoustic sensor capable of operating in a liquid environment and the specific and high affinity biomolecular detection system. Together, these form the potential basis of a novel Point-of-Care platform for simple and rapid monitoring of protein levels in complex samples.

Thickness shear mode (TSM) sensors, also known as quartz crystal micro-balances (QCM) are a class of acoustic wave sensors that have been used for gas/vapor sensing. Fast and sensitive chemical vapor sensing, specifically of hydrocarbon vapors is an important application for these vapor sensors. The TSM sensors typically used have a lower sensitivity compared with other acoustic wave sensors. This thesis describes the development of high sensitivity organic vapor sensors using thin polymer film coatings on TSM devices. Commercially available AT-quartz TSM devices were milled leaving a thin quartz membrane surrounded by a thicker outer ring. This resulted in an increased frequency and a consequent increase in sensitivity, as described by the Sauerbrey equation. The TSM sensors were then coated with thin sensing films of rubbery polymers. Isothermal experiments at room temperature were conducted. A fully instrumented and automated test bed consisting of a temperature-controlled organic vapor dilution system, a precision impedance analyzer, and computer based data acquisition was developed and used to evaluate the performance of the coated TSM devices. The TSM devices compared in this study were AT cut with fundamental resonant frequencies of 10, 20, and 96 MHz. The results of tests conducted are presented to demonstrate increase in sensitivity for higher fundamental frequency TSM devices. 96 MHz TSM resonators were found to be 8 to 27 times more sensitive than 10 MHz resonators. Sensitivity was limited by the difficulty in coating sensing layers and damping of the resonator. Additionally, each sensor was evaluated and compared in terms of detection limit and noise level. 96 MHz resonators had higher noise levels than 10 MHz or 20 MHz resonators; as a result, 96 MHz resonators did not show significant improvements in LOD. Also, response times for 96 MHz resonators were quicker than 10 MHz or 20 MHz resonators and response times generally decreased with analyte concentration. Several rubbery polymer films as well as copolymers were investigated to determine which sensing film would have the optimal performance in terms of response time, recovery, reproducibility, repeatability, frequency noise, and baseline drift. The organic vapors studied were benzene, toluene, hexane, cyclohexane, heptane, dichloroethane, and chloroform at levels ranging from 0.2 to over 13.7 volume percentage in nitrogen gas. The Butterworth-VanDyke (BVD) equivalent circuit model was used to model both the perturbed and unperturbed TSM resonator. Monitoring the sensor response through the equivalent circuit model allowed for discriminating between the organic vapors. Vapor discrimination, in turn, depended upon the changes in the resistance parameter. Finally, the vapor liquid equilibrium at the polymer solvent interface was utilized to correct for perturbations, due to temperature changes, in the sensor response.

No description available.

Protein phosphorylation is a very common posttranslational modification (PTM), which lately has been found to hold the keyrole in the development of many severe diseases, including cancer. Thereby, phosphoprotein analysis tools, generally based on specific enrichment of the phosphoryl group, have been a hot topic during the last decade. In this thesis, two new TiO2-based on-target enrichment methods are developed and presented together with enlightening fundamental results. Evaluation of the developed methods was performed by the analysis of: custom peptides, β-casein, drinking milk, and the viral protein pIIIa. The results show that: i) by optimizing the enrichment protocol (first method), new phosphorylated peptides can be found and ii) by the addition of a separation step after the enrichment (second method), more multi-phosphorylated peptides, which usually are hard to find, could be detected. The fundamental part, on the other hand, shows that the phosphopeptide adsorption is caused by electrostatic interactions, in general follows the Langmuir model, and the affinity increases with the phosphorylation degree. Here, however, the complexity of the system was also discovered, as the adsorption mechanism was found to be affected by the amino acid sequence of the phosphopeptide.

La microbalanza de cristal de cuarzo (QCM) se usa como técnica alternativa de análisis químico, donde las aplicaciones dependen directamente de la sensibilidad del cristal. Por tanto, es el parámetro más importante que determina el uso de los cristales de cuarzo frente a otras técnicas. La ecuación de Sauerbrey, teóricamente relaciona la variación de la densidad de masa en la superficie del cristal con el cambio de la frecuencia y al mismo tiempo predice que la sensibilidad aumenta en la misma proporción que el cuadrado de la frecuencia fundamental de resonancia serie del cristal. Aumentar la frecuencia fundamental de trabajo para aumentar la sensibilidad, es una necesidad; el objetivo principal de esta tesis doctoral es estudiar los sistemas de caracterización de resonadores de cuarzo, que se usan en la actualidad y proponer un sistema o una mejora a los ya existentes que permitan el uso de cristales de cuarzo de alta frecuencia de fundamental (HFF-QCM). De los sistemas que en la actualidad caracterizan a la microbalanza de cuarzo, se destacan los analizadores de impedancia y los osciladores, como métodos de caracterización de HFF-QCM. Los analizadores, por su gran tamaño y coste, quedan relegados a su uso como instrumento de referencia en el laboratorio. Los osciladores en cambio, por su bajo coste, su capacidad de integración, su sencillez del circuito y la monitorización continua de frecuencia de oscilación, lo hacen adecuados como interfaz para sistemas sensores basados en QCM. En esta tesis, se propone un sistema oscilador, basado en un oscilador diferencial equilibrado, como sistema de caracterización de cristales a 10 MHz, estudiándose el comportamiento del circuito, la capacidad de este sistema para compensar la capacitancia paralela del cristal, las aplicación de este tipo de interfaz para la caracterización de líquidos y finalmente se desarrollo una aplicación como inmunosensores piezoeléctricos para la detección del pesticida Carbaryl. / Montagut Ferizzola, YJ. (2011). Sistema Oscilador Mejorado para Aplicaciones de Microbalanza (QCM) en Medios Líquidos y Propuesta de un Nuevo Método de Caracterización para Biosensores Piezoeléctricos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/9688 / Palancia

Produced water (PW), or water associated with crude oil extraction, is the largest oily wastewater stream generated worldwide. The reuse and reclamation of these important water volumes are critical for more sustainable operation in the oilfield. Ceramic membrane filtration is a promising technology for PW treatment; however, fouling is the major drawback for a broader application. Fouling leads to higher resistance to flow, reducing membrane lifetime, and ultimately leading to higher capital expenditures and operating expenses. Further understanding of the interactions between PW foulants and the ceramic materials is needed for designing fouling control strategies and cleaning protocols for ceramic membranes. This work explored different techniques to characterize, visualize, and quantify the submicron PW contaminants content and its adsorption interactions with metal oxides. We visualized and characterized submicron oil droplets in oilfield PW samples by applying suitable advanced microscopy techniques. For the first time, crude oil droplets as small as 20 nm were found in oilfield PW together with other submicron contaminants. The adsorption studies performed by quartz crystal microbalance with dissipation (QCM-D) showed that the interactions of organic surface-active compounds with the metal oxides are driven by the nature of the surfactant and not by the surface properties. This has implications in the selection of the ceramic membrane material, wherein electrostatic interactions should not be taken as the only predicting factor of adsorption and fouling during PW treatment. Furthermore, our results suggested that the more fluid or viscoelastic-like the contaminant layer, the more difficult the cleaning process from the metal oxide. It demonstrates that the mechanical property of the attached films is a crucial factor in designing appropriate cleaning protocols for ceramic membranes. Finally, QCM-D and advanced microscopy techniques were applied to analyze adsorption and cleaning of contaminants in a complex Bahraini PW into alumina as a case study. Bacteria were found to attach irreversibly on the alumina surface, promoting nucleation points for calcium precipitates. The protocols developed in this work are suitable for understanding membrane fouling phenomena in the micron scale and could be implemented before filtration pilot testing to save time and expenses at larger scales.

This master thesis project was carried out at SP Technical Research Institute of Sweden within the FORMAMP project which goal is to increase the efficiency and stability of antimicrobial peptides (AMPs) by exploring and developing a number of innovative formulation strategies for the drug delivery of those systems. In view of the growing problem of bacterial resistance to traditional antibiotics, AMPs represent one of the most promising alternatives as therapeutics against infectious diseases: besides having a fast and non-specific mechanism of action, they are less prone to bacterial resistance. In this project, the goal was to develop an efficient method for the formulation of hexagonal lyotropic phase nanodispersions (called hexosomes) as drug delivery vehicles for the AP114, DPK-060 and LL-37 AMPs. Then, these formulations were characterized through size measurements, zeta potential measurements, SAXS, cryo-TEM and UPLC and their stability was assessed. Lastly, the interaction of these systems with model bacterial membranes was tested through QCM-D and ellipsometry. The relevant samples were found to have a hexagonal structure with the lattice parameter being larger when peptide was loaded. The systems were observed to be sufficiently stable and the peptide loading efficiency was found to be higher than 90% in most cases. The hexosomes loaded with LL-37 were observed to preserve the effectiveness of the peptide when interacting with the model membrane through QCM-D.

Plastics, due to their extensive production and inert nature, accumulate in the environment after their improper disposal. While being in the environment, these plastic-based products undergo different degradation processes resulting in smaller sized microplastics (MPs) and nanoscale plastics (NPs). MPs and NPs can adsorb various organic and inorganic contaminants due to their huge surface area to volume ratio and the presence of diverse functional groups. Hence, the presence of various contaminants in the environment can impact both the plastics and the adsorbed contaminants fate in the environment. In light of this, the current work investigates the co-transport behavior of polystyrene (PS) MPs and copper metal (Cu), as both PS MPs and Cu are commonly encountered in the environment. The co-transport behavior was observed by understanding the mobility and deposition behavior of both contaminants under various ionic strength conditions (IS) and salt types (NaCl, CaCl2). Bench scale packed column studies and batch adsorption experiments were used to observe the transport behavior. The quartz crystal microbalance (QCM) was used to determine the mechanisms responsible for the deposition behavior of MPs and NPs at the nanoscale level. Results showed that in the absence of Cu, the secondary energy minimum was responsible for the reduced PS mobility (40-60%) with increasing IS of NaCl and CaCl2 respectively. However, when Cu was present, PS mobility reduced even more (10-30%), which might result from the adsorption of PS-Cu complexes on porous media following their formation. Similarly, in the absence of PS, Cu had less mobility (nearly 10%) in all IS and salt types due to electrostatic attraction between sand and Cu. On the other hand, Cu demonstrated increasing mobility during co-transport owing to a lack of adsorption sites caused by the competing adsorption of PS and Cu. The batch adsorption results also revealed that MPs had a greater adsorption capacity on quartz sand in the presence of Cu, resulting in enhanced heavy metal mobility. QCM experiments also showed that with increasing IS and in absence of Cu, both MPs and NPs deposition on the silica surface increased due to compression of the electric double layer, following DLVO theory. However, in presence of Cu, PSMPs and PSNPs had 6.6 and 4.0-fold higher deposition respectively for NaCl and 1.5 and 4.8-fold respectively for CaCl2 under the high IS condition, than in absence of Cu. Positive metal ions can compress the electrostatic double-layer even more, lowering the energy barrier and form complexes with the PS causing greater PS deposition on the silica surfaces. Furthermore, QCM showed that regardless of the presence of heavy metals, NPs mass deposition was higher than MPs on the silica surface. According to DLVO theory, NPs had a lower energy barrier than MPs due to their smaller size, resulting in a higher deposition. In summary, the findings of this study showed that the interaction between PS and Cu can influence both their transport and deposition behaviors in the environment under different aquatic chemistry conditions. This work could be used to anticipate the fate and movement of MPs and NPs in the presence of other pollutants in the aquatic environment and allow necessary steps to be taken to prevent additional contamination and design their subsequent removal.

Natural composites like wood are scale-integrated structures that range from molecular to the macroscopic scale. Inspired by this design, layer-by-layer (LbL) deposition technique was used to create lignocellulosic composites from isolated wood polymers namely cellulose and lignin, with a lamellar architecture. In the first phase of the study, adsorption of alkali lignin onto cationic surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Complete coverage of the cationic surface with alkali lignin occured at low solution concentration; large affinity coefficients were calculated for this system at differing pH levels. Adsorption studies with organosolv lignin in an organic solvent, and spectroscopic analysis of mixtures of cationic polymer with alkali lignin revealed a non-covalent interaction. The work demonstrated how noncovalent interactions could be exploited to molecular organize thin polyphenolic biopolymers on cationic surfaces. The second phase of the study examined the adsorption steps during the LbL assembly process to create novel lignocellulosic composites. LbL assembly was carried out using oxidized nanocellulose (NC) and lignin, along with a cationic polymer poly(diallyldimethylammonium chloride) (PDDA). QCM-D was used to follow the sequential adsorption process of the three different polymers. Two viscoelastic models, namely Johannsmann and Voigt, were respectively used to calculate the areal mass and thickness of the adsorbed layers. Atomic force microscopy studies showed a complete coverage of the surface with lignin in all the disposition cycles, however, surface coverage with NC was seen to increase with the number of layers. Free-standing composite films were obtained when the LbL process was carried out for 250 deposition cycles (500 bilayers) on a cellulose acetate substrate, following the dissolution of the substrate in acetone. Scanning electron microscopy of the cryo-fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle was estimated to be 17 nm. The third phase of the study investigated the effect of LbL ordering of the polymers versus a cast film composed of a blended mixture of the polymers, using dynamic mechanical analysis. A tan ï ¤ peak was observed in the 30 – 40 ºC region for both films, which was observed in the neat NC film. Heating of the samples under a compressive force produced opposite effects in the films, as the LbL films exhibited swelling, whereas the cast films showed densification. The apparent activation energy of this transition (65 – 80 kJ mol-1) in cast films, calculated based on the Arrhenius equation was found to be coincident to those reported for the ï ¢ transition of amorphous cellulose. The peak was seen to disappear in case of LbL films in the second heat, whereas it was recurring in case of cast films of the blended mixture, and neat NC films. Altogether, the together the work details a novel path to integrate an organized lignin and cellulose molecular structure, albeit modified from their native form, into a three-dimensional composite material. / Ph. D.

Self-assembly of polysaccharide derivatives at liquid/solid interfaces was studied by surface plasmon resonance spectroscopy (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D). Carboxymethyl cellulose (CMC) adsorption onto cellulose surfaces from aqueous solutions was enhanced by electrolytes, especially by divalent cations. A combination of SPR and QCM-D results showed that CMC formed highly hydrated layers on cellulose surfaces (90 to 95% water by mass). Voigt-based viscoelastic modeling of the QCM-D data was consistent with the existence of highly hydrated CMC layers with relatively low shear viscosities of ~ 10-3 N·s·m-2 and elastic shear moduli of ~ 105 N·m-2. Adsorption of pullulan 3-methoxycinnamates (P3MC) and pullulan 4-chlorocinnamates (P4CC) with different degrees of cinnamate substitution (DSCinn) onto cellulose, cellulose acetate propionate (CAP), poly(L-lactic acid) (PLLA), and methyl-terminated self-assembled monolayer (SAM-CH3) surfaces was also studied by SPR and QCM-D. Hydrophobic cinnamate groups promoted the adsorption of pullulan onto all surfaces and the adsorption onto hydrophobic surfaces was significantly greater than onto hydrophilic surfaces. SPR and QCM-D results showed that P3MC and P4CC also formed highly hydrated layers (70 to 90% water by mass) with low shear viscosities and elastic shear moduli. Finally, cellulose adsorption and activity on pullulan cinnamate (PC) and cellulose blend films were studied via QCM-D and in situ atomic force microscopy (AFM). The hydrophobicity of PC surfaces was controlled by adjusting the degree of cinnamate substitution per anhydroglucose unit (DSCinn). It was found that cellulase showed weak adsorption onto low DSCinn PC surfaces, whereas cellulase adsorbed strongly onto high DSCinn PC surfaces, a clear indication of the role surface hydrophobicity played on enzyme adsorption. Moreover, cellulase catalyzed hydrolysis of cellulose/PC and cellulose/polystyrene (PS) blend surfaces was studied. The QCM-D results showed that the cellulase hydrolysis rate on cellulose in cellulose/PC blend surfaces decreased with increasing DSCinn. AFM images revealed smooth surfaces for cellulose/PC (DSCinn = 0.3) blend surfaces and laterally phase separated morphologies for cellulose/PC (DSCinn ≥ 0.7) blend surfaces. The combination of QCM-D and AFM measurements indicated that cellulase catalyzed hydrolysis was strongly affected by surface morphology. The cellulase hydrolysis activity on cellulose in cellulose/PS blend surfaces was similar with cellulose/PC blend surfaces (DSCinn ≥ 0.7). These studies showed self-assembly of macromolecules could be a promising strategy to modify material surfaces and provided further fundamental understanding of adsorption phenomena and bioactivity of macromolecules at liquid/solid interfaces. / Ph. D.