Detection of DNA by electrochemical impedance spectroscopy (EIS) has been reported by many authors and assays have been developed using lab setups. However, as for most detection assay methods there are issues to address to enable the development for the sensor market: Long time-to-result & high complexity for labelled assays and a lack of sensitivity and reproducibility for label-free assays. This work considers two different approaches to address the issues of time-to-result and assay complexity. The first part presents work on achieving rapid sequence-specific electrochemical detection of DNA hybridisation to complementary DNA on an electrode surface. To accomplish assay sensitivity to low DNA target concentrations, a signal amplification strategy is often necessary. One approach is to couple an enzyme to the hybridised target molecules and to deposit insoluble dyes in the subsequent enzymatic reaction, which enhances sensitivity through an increase in the impedance signal in presence of a redox mediator. The time typically taken for this process (20 – 40 min) precludes the use outside lab setups. Therefore, a protocol for sensitive detection in the presence of redox mediator is demonstrated on a practical timescale required for use in sensor applications. Based on these results a model for the fundamental understanding of the amplification reaction is presented which explains the retention of sensitivity at these enhanced timescales. This also enabled further optimisation of the assay for application in single base pair mismatch detection in biologically relevant sequences. Moreover, direct detection of the precipitate formation is demonstrated which enables real-time measurement of the enzymatic reaction without redox agent addition and with enhanced mismatch discrimination. The second part investigates the possibility to detect DNA non-sequence-specifically by non-Faradaic means. This approach aims at reducing assay complexity by establishing whether it is possible to sense the presence of polymeric DNA in solution by measuring changes in the properties of the electrochemical double layer without DNA surface hybridisation. In a sensor setup this approach could be linked to a polymerase chain reaction (PCR) to discriminate polymer from nucleotide monomer and thereby enable PCR progress to be monitored. In this work the response in the electrochemical double layer at the interface of blocked metal electrodes and solutions containing DNA are studied by means of EIS. Blocking layers were applied to the electrode surface to prevent unspecific adsorption of molecules and ions to the metal surface whilst preserving the sensitivity to detection of changes in the double layer. The characteristics of surface blocking layers on disposable electrodes are studied as they are key to understand the double layer properties at a blocked surface. A number of self-assembled monolayers are compared with respect to their temperature stability and their blocking characteristics at different potentials and ion concentrations. This established the basis to study the effect of the presence of, initially, a model polyelectrolyte and, ultimately, DNA on the double layer. Polyelectrolyte detection is successfully shown for the model polyelectrolyte, polyacrylic acid. DNA detection was more challenging and possible causes for deviation from the polyacrylic acid response are discussed.

The 1st chapter provides a detailed review of the development of synthetic approaches to triarylboranes from their first report nearly 135 years ago to the present. In the 2nd chapter, a novel and convenient methodology is reported for the one-pot synthesis of sterically-congested triarylboranes, using bench-stable aryltrifluoroborates as the boron source. The new procedure gives access to symmetrically- and unsymmetrically-substituted triarylboranes. The borylated triarylboranes are suggested as building blocks for the design of functional materials. In the 3rd chapter, four luminescent tetracationic bis-triarylborane DNA and RNA sensors that show high binding affinities, in several cases even in the nM range, are investigated. The molecular structures of two of the neutral precursors reveal some structural flexibility for these compounds in the solid state. The compounds were found to be highly emissive even in water and DNA and RNA binding affinities were found to be dependent on linker length and flexibility. Strong SERS responses for three of the four compounds demonstrate the importance of triple bonds for strong Raman activity in molecules of this compound class. In chapter 4, the compound class of water-soluble tetracationic bis-triarylborane chromophores is extended by EDOT-linked compounds and those are compared to their thiophene-containing analogs. Absorption and emission are significantly red-shifted in these compounds, compared to their thiophene-containing analogs and, due to a large Stokes shift, one of the reported compounds exhibits the most bathochromically shifted emission, observable well into the near infrared region, of all tetracationic water-soluble bis-triarylborane chromophores reported to date. Long-lived excited states, completely quenched by oxygen, were observed for the water-stable compounds of this study via transient absorption spectroscopy and a quantum yield for singlet oxygen formation of 0.6 was determined for one of them. / Das erste Kapitel gibt einen detaillierten Überblick über die Entwicklung verschiedener Synthesemöglichkeiten von Triarylboranen seit ihrer erstmaligen Erwähnung vor rund 135 Jahren bis heute. In Kapitel 2 wurde eine neuartige und praktische Methode für die Eintopfsynthese von sterisch stabilisierten Triarylboranen unter Verwendung von luftstabilen Aryltrifluorboraten als Borquelle beschrieben. Das neue Verfahren ermöglicht den Zugang zu symmetrisch und unsymmetrisch substituierten Triarylboranen, die bei der Konstruktion borhaltiger Funktionsmaterialien verwendet werden könnten. Im dritten Kapitel wurden tetrakationische Bis-Triarylborane bezüglich DNA- und RNA-Sensorik untersucht, wobei hohe Bindungsaffinitäten, wurden. Die Molekülstrukturen von zwei neutralen Vorstufenverbindungen deuten auf eine gewisse Flexibilität für diese Verbindungen im Festkörper hin. Die Verbindungen erwiesen sich selbst in Wasser als stark emittierend und die DNA und RNA Bindungsaffinitäten waren abhängig von Länge und Flexibilität des Linkers. Starke SERS-Signale für drei der vier Verbindungen, zeigen die Bedeutung von Dreifachbindungen für eine starke Raman-Aktivität in Molekülen dieser Verbindungsklasse. In Kapitel 4 dieser Arbeit wurde die Verbindungsklasse wasserlöslicher tetrakationischer Bis Triarylboran-Chromophore um EDOT-verbrückte Verbindungen erweitert und diese mit ihren literaturbekannten Thiophenanaloga verglichen. Absorption und Emission sind in diesen Verbindungen im Vergleich zu ihren Thiophen-haltigen Analoga rotverschoben und eine der Verbindungen zeigt die am weitesten rotverschobene, noch weit im nahen Infrarotbereich detektierbare, Emission aller bisher bekannten Verbindungen dieser Art. Für die wasserstabilen Verbindungen wurden mittels transienter Absorptionsspektroskopie langlebige Zustände beobachtet, die vollständig durch Sauerstoff gequencht werden und eine Quantenausbeute für die Singulett-Sauerstoffbildung von 0.6 wurde für eine der Verbindungen bestimmt.

La réponse immunitaire innée est induite par des infections microbiennes ou des lésions tissulaires. L’étude de sa régulation est l'un des aspects les plus étudiés actuellement en immunologie, et porte notamment sur divers aspects du contrôle des agents pathogènes, du développement de vaccins et de la thérapie contre les maladies inflammatoires chroniques. L’ADN peut jouer le rôle de ligand endogène et induire une réaction immunitaire forte chez les animaux. Des souris déficientes pour la DNaseII lysosomiale accumulent de l’ADN dans leurs macrophages, notamment celui provenant des noyaux expulsés des érythroblastes lors de leur maturation en érythrocytes. Elles n’arrivent pas à les dégrader. Elles produisent en réponse de grandes quantités d’interférons de type I. Les souris meurent d'anémie au stade embryonnaire. Ce phénomène m’a amenée à poser une question importante: Comment les cellules reconnaissentelles l'ADN et comment y répondentelles? Pour savoir comment les cellules reconnaissent et répondent à l'ADN, nous avons visé trois objectifs spécifiques: I. Mise au point un modèle in vivo de drosophile pour étudier la réponse immunitaire innée contre l'ADN II. Dissection génétique de la réponse immunitaire induite par l'ADN III. Trouver des récepteurs de l’AND A l’issu de mon travail de thèse, je peux proposer que (i) la réponse immunitaire induite par l’ADN repose sur la voie IMD chez la drosophile, (ii) IK2 (TBK1), CG1667 (TMEM173), et EYA (EYA4) sont des molécules clés dans la cascade de signalisation en aval de la détection de l'ADN chez la drosophile, (iii) EYA est liée à la voie IMD au niveau de RELISH ou IKKβ, (iv) Orthologue drosophile LRRFIP1 de l'ADN des mammifères capteur est responsable de la détection de l'ADN dans le modèle DNaseII mouche déficiente (v) chez la drosophile CG3800 (CNBP) est un candidat pour la détection d'AND dans les insectes et les mammifères. / Innate immune responses are initiated during infections and tissue damage, and largely impact on various human diseases. DNA has been shown to be a strong innate immune stimulator in animals. For example, DNaseII deficient mice accumulate undigested DNA in macrophages from the expelled nuclei of erythroid progenitor cells, produce large amounts of type I Interferons in DNA-accumulated cells, and die from anemia at the embryonic stage. This phenomenon brought us an important question: How does cells recognize DNA and respond to it? To answer the question, we took three approaches: (1) Establishing in vivo model to study the innate immune response against DNA (2) Genetic dissection of the DNA-mediated immune response (3) Finding DNA sensors In my thesis project, we provide (1) DNA-mediated immune responses relies on the IMD pathway in Drosophila, (2) IK2(TBK1), CG1667(TMEM173, STING), and EYA(EYA4) are key molecules in the downstream signaling cascade of DNA sensing in Drosophila, (3) EYA is linked to the IMD pathway at the level of RELISH or IKKβ, (4) Drosophila orthologue of mammalian DNA sensor LRRFIP1 is responsible for DNA sensing in DNaseII deficient fly model, (5) Drosophila CG3800(CNBP) is a candidate for DNA sensing in both insects and mammals.

Label-free detection of DNA has been successfully demonstrated on field effect transistor (FET) based devices. Since conducting organic materials was discovered and have attracted more and more research efforts by their profound advantages, this work will focus on utilizing an organic field effect transistor (OFET) as DNA sensor. An OFET constructed with a transporting fluidic channel, WetOFET, forms a fluid-polymer (active layer) interface where the probe DNA can be introduced. DNA hybridization and non-hybridization after injecting target DNA and non-target DNA were monitored by transistor characteristics. The Hysteresis area of transfer curve increased after DNA hybridization which may be caused by the increasing electrostatic screening induced by the increasing negative charge from target DNA. The different morphology of coating surface could also influence the OFET response.

<p>Label-free detection of DNA has been successfully demonstrated on field effect transistor (FET) based devices. Since conducting organic materials was discovered and have attracted more and more research efforts by their profound advantages, this work will focus on utilizing an organic field effect transistor (OFET) as DNA sensor.</p><p>An OFET constructed with a transporting fluidic channel, WetOFET, forms a fluid-polymer (active layer) interface where the probe DNA can be introduced. DNA hybridization and non-hybridization after injecting target DNA and non-target DNA were monitored by transistor characteristics. The Hysteresis area of transfer curve increased after DNA hybridization which may be caused by the increasing electrostatic screening induced by the increasing negative charge from target DNA. The different morphology of coating surface could also influence the OFET response.</p>

No description available.

<p>In the year of 2020, an international pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has afflicted tens of millions of people’s life also disrupting global economics. Diagnostic testing is an important part of ensuring public health until a vaccine that has been shown to be safe and effective is made available to the general public. Most tests for detecting COVID-19 utilize quantitative polymerase chain reaction (qPCR) assays, which is a specific and relatively simple quantitative assay that could provide adequate sensitivity for diagnosing early infection. Although powerful, these lab-based molecular assays have a significant lag time, usually several days before receiving results. To satisfy the needs of different purposes (diagnostics, screening, and surveillance), a unified approach is impractical. This thesis presents an alternative testing method supporting the current procedure of point of care (POC) testing and in community testing. This paper-based test overcomes the limitations of current testing methods by utilizing reverse-transcription loop-mediated isothermal amplification (RT-LAMP) and receiving the result on-site by a color change in the presence of the virus within 60 minutes. The test utilizes untreated freshly collected saliva, a less invasive specimen, as the sample and possesses a limit of detection (LoD) of 200 copies of virus per microliter of whole saliva with an analytical sensitivity of 97% and analytical specificity of 100%. The test requires minimal operator training and could be fabricated on a large-scale using roll-to-roll methods. Since the test is based on nucleic acids, the testing platform itself lends to further applications <a>including food safety monitoring, animal diagnostic, etc. simply by changing the specific primers</a>. </p>