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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Development of a Sensor System for Rapid Detection of Volatile Organic Compounds in Biomedical Applications

Angarita Rivera, Paula Andrea 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Volatile organic compounds (VOCs) are endogenous byproducts of metabolic pathways that can be altered by a disease or condition, leading to an associated and unique VOC profile or signature. Current methodologies for VOC detection include canines, gas chromatography-mass spectrometry (GC-MS), and electronic nose (eNose). Some of the challenges for canines and GC-MS are cost-effectiveness, extensive training, expensive instrumentation. On the other hand, a significant downfall of the eNose is low selectivity. This thesis proposes to design a breathalyzer using chemiresistive gas sensors that detects VOCs from human breath, and subsequently create an interface to process and deliver the results via Bluetooth Low Energy (BLE). Breath samples were collected from patients with hypoglycemia, COVID-19, and healthy controls for both. Samples were processed, analyzed using GC-MS, and probed through statistical analysis. A panel of 6 VOC biomarkers distinguished between hypoglycemia (HYPO) and Normal samples with a training AUC of 0.98 and a testing AUC of 0.93. For COVID-19, a panel of 3 VOC biomarkers distinguished between COVID-19 positive symptomatic (COVID-19) and healthy Control samples with a training area under the curve (AUC) of receiver operating characteristic (ROC) of 1.0 and cross-validation (CV) AUC of 0.99. The model was validated with COVID-19 Recovery samples. The discovery of these biomarkers enables the development of selective gas sensors to detect the VOCs. Polyethylenimine-ether functionalized gold nanoparticle (PEI-EGNP) gas sensors were designed and fabricated in the lab and metal oxide (MOX) semiconductor gas sensors were obtained from Nanoz (Chip 1: SnO2 and Chip 2: WO3). These sensors were tested at different relative humidity (RH) levels and VOC concentrations. The contact angle which measures hydrophobicity was 84° and the thickness of the PEI-EGNP coating was 11 µ m. The PEI-EGNP sensor response at RH 85% had a signal 10x higher than at RH 0%. Optimization of the MOX sensor was performed by changing the heater voltage and concentration of VOCs. At RH 85% and heater voltage of 2500 mV, the performance of the sensors increased. Chip 2 had higher sensitivity towards VOCs especially for one of the VOC biomarkers identified for COVID-19. PCA distinguished VOC biomarkers of HYPO, COVID-19, and healthy human breath using the Nanoz. A sensor interface was created to integrate the PEI-EGNP sensors with the printed circuit board (PCB) and Bluno Nano to perform machine learning. The sensor interface can currently process and make decisions from the data whether the breath is HYPO (-) or Normal (+). This data is then sent via BLE to the Hypo Alert app to display the decision.
2

Biohybrid sensor systems for the detection of metal ions in water

Jung, Jonas 20 February 2020 (has links)
Die Wasserverschmutzung durch Seltenen Erden (REEs) und Schwermetallen verursacht viele Probleme für die Umwelt und die menschliche Gesundheit. Daher ist der Nachweis solcher Elemente von hoher Priorität. Derzeit verwendete Methoden haben einige Nachteile, wie hohe Messkosten, beschränke Selektivität, komplexe Handhabung oder der Bedarf von hochqualifiziertem Personal für die Probenanalyse. Die Kombination von biologischen Komponenten und Nanomaterialien zur Sensorentwicklung bietet eine Möglichkeit diese Nachteile ausgleichen. Mikroorganismen haben evolutionäre Strategien entwickelt, um sich vor toxischen Schwermetallen zu schützen, z.B durch Binden der Metallionen an ihrer Zelloberfläche mit speziellen Oberflächenproteinen (S-Layer). Diese bestehen aus einer Monolage identischer (Glyco-) Proteine, die sich selbst assemblieren und eine hochgeordnete kristalline Struktur unterschiedlicher Symmetrie bilden können. Studien haben die Bindung von Metallionen (einschließlich REEs) durch S-Layer-Proteine gezeigt. In dieser Dissertation wurden drei Nanomaterialien (Goldnanopartikel (AuNPs), planare Goldoberflächen und Nanodiamanten (NDs)) mit acht verschiedene S-Layer-Proteinen beschichtet. Ziel war die Entwicklung von Biohybrid-Sensor-Systemen für die Detektion von bis zu 12 Metallionen in Wasser. Ein kolorimetrisches Sensorsystem mit biofunktionalisierten AuNPs zur Detektion von REEs und Schwermetallen, einschließlich der aktuell vermehrt auftretenden Schadstoffe Lanthan und Gadolinium, wurde etabliert. Die Nachweisgrenzen lagen im Bereich vergleichbarer AuNPs-Systeme zum Nachweis von Schwermetallen, während die Slayer-AuNP-Biohybride ein breiteres Spektrum von Metallionen detektieren konnten. Das Screening aller acht S-Layer-AuNP-Biohybride mit 12 Metallsalzlösungen ergab charakteristische Wechselwirkungsmuster für jede der Kombinationen und ermöglichte den spezifischen Nachweis einer einzelnen Metallionenspezies in unbekannten Lösungen. Eine Kosten- und Ressourcenoptimierung ist über die Lagerung bis zu drei Monate und Wiederverwendbarkeit gegeben. Auf planaren Goldoberflächen ermöglichten die SPR-Spektroskopie die Messung der Adsorption von S-Layer-Proteinen, sowie die anschließende Detektion von CuSO4, NiCl2 und YCl3. Die Detektionslimits lagen dabei unter den kolorimetrischen Biohybridsystemen. Die SPR-Chips wurden erfolgreich regeneriert und für mehrere Funktionalisierungen mit S-Layer-Proteinen wiederverwendet. Das S-Layer-Protein SslA von S. ureae ATCC 13881 wurde erstmals an NDs adsorbiert. Die NDs/SslA-Biohybride wurden zur Detektion von CuCl2 und NiCl 2 verwendet, indem die Agglomeration und das Fluoreszenzquenching gemessen wurden. Es hat sich gezeigt, dass die vorgestellten Systeme viele der Nachteile ausgleichen, die mit derzeit verwendeten Systemen verbunden sind. Sie detektieren eine Vielzahl von Metallionen und minimieren so den Bedarf für mehrere Methoden. Die Nachweisgrenzen waren vergleichbar mit aktuellen kolorimetrischen und chemischen Kit-Systemen. Die S-layer-AuNPs und NDs/S-layer-Biohybride waren schnell und einfach zu handhaben, wodurch der Bedarf an hochqualifiziertem Messpersonal minimiert werden kann. Darüber hinaus führt die Verwendung von kostengünstigen Materialien wie NDs und die Wiederverwendbarkeit der Biohybride zu einem ressourceneffizienten und kostengünstigen Nachweissystem. Diese Dissertation hat das enorme Potenzial von S-Layer-Proteinen für den Nachweis von REEs und Schwermetallen in Wasser unter Verwendung verschiedener Nachweissysteme wie kolorimetrischer AuNPs-Assays, SPR-Spektroskopie und NDs gezeigt. / The pollution of aqueous systems with rare earth elements (REEs) and heavy metals causes serious problems for environmental and human health. Therefore, the detection of such elements is of uttermost importance. Currently used methods have some disadvantages, such as high measurement costs, limited selectivity, complex sample handling, or the need for highly qualified personnel for sample analysis. The combination of biological components and nanomaterials for sensor development offers a way to offset these disadvantages. Microorganisms have developed strategies to protect themselves from heavy metal toxicity, e.g. by binding the metal ions on their cell surface with special Surface layer (S-layer) proteins. They consist of a monolayer of identical (glyco-) proteins, which can self-assemble and form a highly ordered crystalline structure of varying symmetry. Studies on the heavy metal binding of S-layer proteins have demonstrated their affinity for metal ions, including REE. The combination of nanomaterials with S-layer proteins enables the development of new sensors for these elements. Within this dissertation several nanomaterials in combination with S-layer proteins were investigated to obtain sensors for REEs and heavy metals. Eight different S-layer proteins were used to functionalize AuNPs, flat gold surfaces and nanodiamonds (NDs) for the detection of up to 12 metal ions in water. Colorimetric sensor systems with biofunctionalized AuNPs for the detection of REE and heavy metals, including the newly emerging pollutants lanthanum and gadolinium, were established. The detection limits of reference measurements and spiked tapwater samples were in the range of comparable AuNPs systems for the detection of heavy metals, while offering a broader range of metal ions to detect. The screening of all eight S-layer-AuNP biohybrids with 12 metal ions revealed specific interaction patterns for each of the combinations. The optimization cost and resource is achieved by storage up to three months and reusability of the S-layer-AuNP biohybrids. Surface plasmon resonance (SPR) spectroscopy enabled the measurement of S-layer proteins binding to flat gold surfaces, resulting in a stable protein layer used for the subsequent detection of CuSO4, NiCl2 and YCl3. The SPR chips were succesfully regenerated and reused for multiple functionalizations with S-layer proteins. The S-layer protein SslA from S. ureae ATCC 13881 was successfully adsorbed to the pristine NDs by physical conjugation. The NDs/SslA conjugates were used for the detection of CuCl2 and NiCl2, by measuring the agglomeration of the NDs and fluorescence quenching. The presented systems compensate many of the disadvantages associated with currently used techniques. They detect a broad variety of metal ions, minimizing the need for multiple methods. The detection limits were comparable to current colorimetric and chemical kit systems. The S-layer-AuNPs and NDs/S-layer biohybrids were quick and easy to handle, minimizing the need for highly qualitified personnel. In addition, the use of cost-effective materials such as NDs and the reusability of the biohybrids results in resource-efficient and cost-effective sensor systems. This project has shown the tremendous potential of S-layer proteins for the detection of REE and metal ions in water, by utilizing different detection systems like colorimetric AuNPs assays, SPR spectroscopy and NDs.
3

Towards Development of Smart Nanosensor System To Detect of Hypoglycemia From Breath

Thakur, Sanskar S. 05 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The link between volatile organic compounds (VOCs) from breath and various diseases and specific conditions has been identified since long by the researchers. Canine studies and breath sample analysis on Gas chromatography/ Mass Spectroscopy has proven that there are VOCs in the breath that can detect and potentially predict hypoglycemia. This project aims at developing a smart nanosensor system to detect hypoglycemia from human breath. The sensor system comprises of 1-Mercapto-(triethylene glycol) methyl ether functionalized goldnanoparticle (EGNPs) sensors coated with polyetherimide (PEI) and poly(vinylidene fluoride -hexafluoropropylene) (PVDF-HFP) and polymer composite sensor made from PVDF-HFP-Carbon Black (PVDF-HFP/CB), an interface circuit that performs signal conditioning and amplification, and a microcontroller with Bluetooth Low Energy (BLE) to control the interface circuit and communicate with an external personal digital assistant. The sensors were fabricated and tested with 5 VOCs in dry air and simulated breath (a mixture of air, small portion of acetone, ethanol at high humidity) to investigate sensitivity and selectivity. The name of the VOCs is not disclosed herein but these VOCs have been identified in-breath and are identified as potential biomarkers for other diseases as well. The sensor hydrophobicity has been studied using contact angle measurement. The GNPs size was verified using Ultra-Violent-Visible (UV-VIS) Spectroscopy. Field Emission Scanning Electron Microscope (FESEM) image is used to show GNPs embedded in the polymer film. The sensors sensitivity increases by more than 400\% in an environment with relative humidity (RH) of 93\% and the sensors show selectivity towards VOCs of interest. The interface circuit was designed on Eagle PCB and was fabricated using a two-layer PCB. The fabricated interface circuit was simulated with variable resistance and was verified with experiments. The system is also tested at different power source voltages and it was found that the system performance is optimum at more than 5 volts. The sensor fabrication, testing methods, and results are presented and discussed along with interface circuit design, fabrication, and characterization. / 2022-05-8
4

Alternative Auslesemöglichkeiten für Hefe-Ganzzellsensoren

Altenkirch, Falko 18 January 2019 (has links)
Ganzzellsensoren sind potentielle Kandidaten für den Einsatz in der Umwelttechnik zur Detektion von Schwermetallen, organischen Lösungsmitteln oder Xenobiotika. Ebenso können mit ihrer Hilfe andauernde Prozesse, wie z.B. in der Biogasentwicklung, überwacht werden. Etablierte, auf Genexpression basierende Ausleseverfahren besitzen unterschiedliche Nachteile, die den Einsatz bisher weitestgehend auf das Labor beschränken. In der vorliegenden Arbeit wurden dazu drei alternative Auslesemöglichkeiten evaluiert, die durch kostengünstige Messverfahren und einem einfachen experimentellen Aufbau realisiert werden können. Die gezielte Morphologieänderung von Sensorhefen, die analytinduzierte Aggregation von Zellen und die analytabhängige Anlagerung von Goldnanopartikeln an Sensorhefen. Während sich die zwei erstgenannten Verfahren derzeit noch in Entwicklungszustand befinden, konnte durch die Anlagerung von Goldnanopartikeln an Sensorhefen der Wirkstoff Diclofenac erfolgreich detektiert werden. Die dazu notwendige Inkubationsdauer der Sensorhefen mit Diclofenac als auch das Detektionslimit wurde im Vergleich zu veröffentlichten Daten um je eine Größenordnung verringert.
5

Metallic nanostructure synthesis using DNA origami molds

Helmi, Seham 14 September 2018 (has links)
The past decade has witnessed a breakthrough in the field of structural DNA nanotechnology, which utilizes DNA molecules as a construction material rather than as simple carriers of the genetic information. With the superior programmability of DNA, sub-nanometer precision in the self-assembly of various complex two- and three-dimensional nanostructures is achievable. It also allows a site-specific placement of different objects and functional groups onto the formed structures. This has enabled the assembly of highly sophisticated nanostructures for various applications. While the field of structural DNA nanotechnology has been astonishingly advancing, many nanoelectronics-relevant structures are made of inorganic materials, and DNA-based nanostructures have shown rather low conductivity. This has limited the use of DNA structures in nanoelectronics and reflected the need for a similar programmable route for the inorganic nanofabrication. A conceivable solution would use DNA nanostructures in a way that will precisely transfer the structural information of the DNA shapes into fabricated metallic nanostructures. One way to do that is to use the DNA nanostructures as templates for external material deposition onto the DNA surface. While this strategy has been effective in proving the concept of DNA-shape transfer, metallic nanostructures fabricated this way have shown some drawbacks, such as showing rough surface morphologies and lacking the required homogeneity for the fabricated metallic structures. An alternative strategy would be to design DNA mold structures that can dictate the shape of metal that is “cast” inside such a DNA container. The main topic of my thesis concerns the second strategy. To discuss this in detail, the structure and some of the important properties of DNA are introduced in section 1.1. In section 1.2 the main milestones in the development of the DNA-nontechnology field are discussed and section 1.3 focuses on previous fabrication approaches of DNA-based metallic nanostructures.

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