abstract: Over the past several decades, there has been a growing interest in the use of fluorescent probes in low-cost diagnostic devices for resource-limited environments. This dissertation details the design, development, and deployment of an inexpensive, multiplexed, and quantitative, fluorescence-based lateral flow immunoassay platform, in light of the specific constraints associated with resource-limited settings. This effort grew out of the need to develop a highly sensitive, field-deployable platform to be used as a primary screening and early detection tool for serologic biomarkers for the high-risk human papillomavirus (hrHPV) infection. A hrHPV infection is a precursor for developing high-grade cervical intraepithelial neoplasia (CIN 2/3+). Early detection requires high sensitivity and a low limit-of-detection (LOD). To this end, the developed platform (DxArray) takes advantage of the specificity of immunoassays and the selectivity of fluorescence for early disease detection. The long term goal is to improve the quality of life for several hundred million women globally, at risk of being infected with hrHPV. The developed platform uses fluorescent labels over the gold-standard colorimetric labels in a compact, high-sensitivity lateral flow assay configuration. It is also compatible with POC settings as it substitutes expensive and bulky light sources for LEDs, low-light CMOS cameras, and photomultiplier tubes for photodiodes, in a transillumination architecture, and eliminates the need for expensive focusing/transfer optics. The platform uses high-quality interference filters at less than $1 each, enabling a rugged and robust design suitable for field use. The limit of detection (LOD) of the developed platform is within an order of magnitude of centralized laboratory diagnostic instruments. It enhances the LOD of absorbance or reflectometric and visual readout lateral flow assays by 2 - 3 orders of magnitude. This system could be applied toward any chemical or bioanalytical procedure that requires a high performance at low-cost. The knowledge and techniques developed in this effort is relevant to the community of researchers and industry developers looking to deploy inexpensive, quantitative, and highly sensitive diagnostic devices to resource-limited settings. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Philosophiae Doctor - PhD (Chemistry) / There is growing concern on endocrine disrupting compounds (EDCs). The presence of drugs in water supplies was first realized in Germany in the early 1990s when environmental scientists discovered clofibric acid. Clofibric acid has the ability to lower cholesterol in ground water below a water treatment plant. Endocrine disrupting compounds can be defined as those chemicals with the ability to alter daily functioning of the endocrine system in living organisms. There are numerous molecules that are regarded or referred to as EDCs such as but not limited to organochlorinated pesticides, industrial chemicals, plastics and plasticizers, fuels, estrogens and many other chemicals that are found in the environment or are in widespread use. 17?- estradiol is the principal estrogen found in mammals during reproductive years. Estriol is produced in large quantities during pregnancy. 17?-estradiol is the strongest, estriol the weakest. Estriol is water soluble, estrone and estradiol are not. Although estrogen is produced in women they are also at risk of over exposure to estrogen. Pesticides are extensively used today in agricultural settings to prevent and control pests. Various pesticides, including banned organochlorines (OCs) and modern non-persistent pesticides, have shown the ability to disrupt thyroid activity, disturbing the homeostasis of the thyroid system. Because these EDCs have adverse effects on health of both human and wildlife, it is imperative to develop viable costeffective analytical methods for the detection of these EDCs in complicated samples and at very low concentrations. Very high selectivity towards particular compounds is a very important property for the suitability of a detection method. This is because these compounds mostly coexist in complex matrices which makes the detection of a specific compound very challenging. It is paramount to develop highly sensitive and selective methods for the detection of these estrogens and phosphoric acid-based pesticides at trace levels. / 2021-08-31

Analytical chemistry can be split into two main types, qualitative and quantitative. Most modern analytical chemistry is quantitative. Popular sensitivity to health issues is aroused by the mountains of government regulations that use science to, for instance, provide public health information to prevent disease caused by harmful exposure to toxic substances. The concept of the minimum amount of an analyte or compound that can be detected or analysed appears in many of these regulations (for example, to discard the presence of traces of toxic substances in foodstuffs) generally as a part of method validation aimed at reliably evaluating the validity of the measurements.The lowest quantity of a substance that can be distinguished from the absence of that substance (a blank value) is called the detection limit or limit of detection (LOD). Traditionally, in the context of simple measurements where the instrumental signal only depends on the amount of analyte, a multiple of the blank value is taken to calculate the LOD (traditionally, the blank value plus three times the standard deviation of the measurement). However, the increasing complexity of the data that analytical instruments can provide for incoming samples leads to situations in which the LOD cannot be calculated as reliably as before.Measurements, instruments and mathematical models can be classified according to the type of data they use. Tensorial theory provides a unified language that is useful for describing the chemical measurements, analytical instruments and calibration methods. Instruments that generate two-dimensional arrays of data are second-order instruments. A typical example is a spectrofluorometer, which provides a set of emission spectra obtained at different excitation wavelengths.The calibration methods used with each type of data have different features and complexity. In this thesis, the most commonly used calibration methods are reviewed, from zero-order (or univariate) to second-order (or multi-linears) calibration models. Second-order calibration models are treated in details since they have been applied in the thesis.Concretely, the following methods are described:- PARAFAC (Parallel Factor Analysis)- ITTFA (Iterative Target Transformation Analysis)- MCR-ALS (Multivariate Curve Resolution-Alternating Least Squares)- N-PLS (Multi-linear Partial Least Squares)Analytical methods should be validated. The validation process typically starts by defining the scope of the analytical procedure, which includes the matrix, target analyte(s), analytical technique and intended purpose. The next step is to identify the performance characteristics that must be validated, which may depend on the purpose of the procedure, and the experiments for determining them. Finally, validation results should be documented, reviewed and maintained (if not, the procedure should be revalidated) as long as the procedure is applied in routine work.The figures of merit of a chemical analytical process are 'those quantifiable terms which may indicate the extent of quality of the process. They include those terms that are closely related to the method and to the analyte (sensitivity, selectivity, limit of detection, limit of quantification, ...) and those which are concerned with the final results (traceability, uncertainty and representativity) (Inczédy et al., 1998). The aim of this thesis is to develop theoretical and practical strategies for calculating the limit of detection for complex analytical situations. Specifically, I focus on second-order calibration methods, i.e. when a matrix of data is available for each sample.The methods most often used for making detection decisions are based on statistical hypothesis testing and involve a choice between two hypotheses about the sample. The first hypothesis is the "null hypothesis": the sample is analyte-free. The second hypothesis is the "alternative hypothesis": the sample is not analyte-free. In the hypothesis test there are two possible types of decision errors. An error of the first type occurs when the signal for an analyte-free sample exceeds the critical value, leading one to conclude incorrectly that the sample contains a positive amount of the analyte. This type of error is sometimes called a "false positive". An error of the second type occurs if one concludes that a sample does not contain the analyte when it actually does and it is known as a "false negative". In zero-order calibration, this hypothesis test is applied to the confidence intervals of the calibration model to estimate the LOD as proposed by Hubaux and Vos (A. Hubaux, G. Vos, Anal. Chem. 42: 849-855, 1970).One strategy for estimating multivariate limits of detection is to transform the multivariate model into a univariate one. This strategy has been applied in this thesis in three practical applications:1. LOD for PARAFAC (Parallel Factor Analysis).2. LOD for ITTFA (Iterative Target Transformation Factor Analysis).3. LOD for MCR-ALS (Multivariate Curve Resolution - Alternating Least Squares)In addition, the thesis includes a theoretical contribution with the proposal of a sample-dependent LOD in the context of multivariate (PLS) and multi-linear (N-PLS) Partial Least Squares. / La Química Analítica es pot dividir en dos tipus d'anàlisis, l'anàlisi quantitativa i l'anàlisi qualitativa. La gran part de la química analítica moderna és quantitativa i fins i tot els govern fan ús d'aquesta ciència per establir regulacions que controlen, per exemple, nivells d'exposició a substàncies tòxiques que poden afectar la salut pública. El concepte de mínima quantitat d'un analit o component que es pot detectar apareix en moltes d'aquestes regulacions, en general com una part de la validació dels mètodes per tal de garantir la qualitat i la validesa dels resultats.La mínima quantitat d'una substància que pot ser diferenciada de l'absència d'aquesta substància (el que es coneix com un blanc) s'anomena límit de detecció (limit of detection, LOD). En procediments on es treballa amb mesures analítiques que són degudes només a la quantitat d'analit present a la mostra (situació d'ordre zero) el LOD es pot calcular com un múltiple de la mesura del blanc (tradicionalment, 3 vegades la desviació d'aquesta mesura). Tanmateix, l'evolució dels instruments analítics i la complexitat creixent de les dades que generen, porta a situacions en les que el LOD no es pot calcular fiablement d'una forma tan senzilla. Les mesures, els instruments i els models de calibratge es poden classificar en funció del tipus de dades que utilitzen. La Teoria Tensorial s'ha utilitzat en aquesta tesi per fer aquesta classificació amb un llenguatge útil i unificat. Els instruments que generen dades en dues dimensions s'anomenen instruments de segon ordre i un exemple típic és l'espectrofluorímetre d'excitació-emissió, que proporciona un conjunt d'espectres d'emissió obtinguts a diferents longituds d'ona d'excitació.Els mètodes de calibratge emprats amb cada tipus de dades tenen diferents característiques i complexitat. En aquesta tesi, es fa una revisió dels models de calibratge més habituals d'ordre zero (univariants), de primer ordre (multivariants) i de segon ordre (multilinears). Els mètodes de segon ordre estan tractats amb més detall donat que són els que s'han emprat en les aplicacions pràctiques portades a terme. Concretament es descriuen:- PARAFAC (Parallel Factor Analysis)- ITTFA (Iterative Target Transformation Analysis)- MCR-ALS (Multivariate Curve Resolution-Alternating Least Squares)- N-PLS (Multi-linear Partial Least Squares)Com s'ha avançat al principi, els mètodes analítics s'han de validar. El procés de validació inclou la definició dels límits d'aplicació del procediment analític (des del tipus de mostres o matrius fins l'analit o components d'interès, la tècnica analítica i l'objectiu del procediment). La següent etapa consisteix en identificar i estimar els paràmetres de qualitat (figures of merit, FOM) que s'han de validar per, finalment, documentar els resultats de la validació i mantenir-los mentre sigui aplicable el procediment descrit.Algunes FOM dels processos químics de mesura són: sensibilitat, selectivitat, límit de detecció, exactitud, precisió, etc. L'objectiu principal d'aquesta tesi és desenvolupar estratègies teòriques i pràctiques per calcular el límit de detecció per problemes analítics complexos. Concretament, està centrat en els mètodes de calibratge que treballen amb dades de segon ordre.Els mètodes més emprats per definir criteris de detecció estan basats en proves d'hipòtesis i impliquen una elecció entre dues hipòtesis sobre la mostra. La primera hipòtesi és la hipòtesi nul·la: a la mostra no hi ha analit. La segona hipòtesis és la hipòtesis alternativa: a la mostra hi ha analit. En aquest context, hi ha dos tipus d'errors en la decisió. L'error de primer tipus té lloc quan es determina que la mostra conté analit quan no en té i la probabilitat de cometre l'error de primer tipus s'anomena fals positiu. L'error de segon tipus té lloc quan es determina que la mostra no conté analit quan en realitat si en conté i la probabilitat d'aquest error s'anomena fals negatiu. En calibratges d'ordre zero, aquesta prova d'hipòtesi s'aplica als intervals de confiança de la recta de calibratge per calcular el LOD mitjançant les fórmules d'Hubaux i Vos (A. Hubaux, G. Vos, Anal. Chem. 42: 849-855, 1970)Una estratègia per a calcular límits de detecció quan es treballa amb dades de segon ordre es transformar el model multivariant en un model univariant. Aquesta estratègia s'ha fet servir en la tesi en tres aplicacions diferents::1. LOD per PARAFAC (Parallel Factor Analysis).2. LOD per ITTFA (Iterative Target Transformation Factor Analysis).3. LOD per MCR-ALS (Multivariate Curve Resolution - Alternating Least Squares)A més, la tesi inclou una contribució teòrica amb la proposta d'un LOD que és específic per cada mostra, en el context del mètode multivariant PLS i del multilinear N-PLS.

Magister Scientiae - MSc / Indinavir is a potent and well tolerated protease inhibitor drug used as a component of the highly active antiretroviral therapy (HAART) of HIV/AIDS, which results in pharmacokinetics that may be favourable or adverse. These drugs work by maintaining a plasma concentration that is sufficient to inhibit viral replication and thereby suppressing a patient’s viral load. A number of antiretroviral drugs, including indinavir, undergo metabolism that is catalysed by cytochrome P450-3A4 enzyme found in the human liver microsomes. The rate of drug metabolism influences a patient’s response to treatment as well as drug interactions that may lead to life-threatening toxic conditions, such as haemolytic anaemia, kidney failure and liver problems. Therapeutic drug monitoring (TDM) during HIV/AIDS treatment has been suggested to have a potential to reduce drug toxicity and optimise individual therapy. A fast and reliable detection technique, such as biosensing, is therefore necessary for the determination of a patient’s metabolic profile for indinavir and for appropriate dosing of the drugs. In this study biosensors developed for the determination of ARV drugs comprised of cysteamine self-assembled on a gold electrode, on which was attached 3-mercaptopropionic acid-capped palladium telluride (3-MPA-PdTe) or thioglycolic acid-capped palladium telluride (TGA-PdTe) quantum dots that are cross-linked to cytochrome P450-3A4 (CYP3A4) in the presence of 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The quantum dots were synthesized in the presence of capping agents (3-MPA or TGA) to improve their stability, solubility and biocompatibility. The capping of PdTe quantum dots with TGA or 3-MPA was confirmed by FTIR, where the SH group absorption band disappeared from the spectra of 3-MPA-PdTe and TGA-PdTe. The particle size of the quantum dots (< 5 nm) was estimated from high resolution transmission electron microscopy (HRTEM) measurements. Optical properties of the materials were confirmed by UV-Vis spectrophotometry which produced absorption iii bands at ~320 nm that corresponded to energy band gap values of 3 eV (3.87 eV) for TGAPdTe (3-MPA-PdTe) quantum dots. The electrocatalytic properties of the quantum dots biosensor systems were studied by cyclic voltammetry (CV) for which the characteristic reduction peak at 0.75 V was used to detect the response of the biosensor to indinavir. Results for indinavir biosensor constructed with 3-MPA-SnSe quantum dots are also reported in this thesis. The three biosensors systems were very sensitive towards indinavir; and gave low limits of detection (LOD) values of 3.22, 4.3 and 6.2 ng/mL for 3-MPA-SnSe, 3-MPA-PdTe and TGA-PdTe quantum dots biosensors, respectively. The LOD values are within the ‘maximum plasma concentration’ (Cmax) value of indinavir (5 - 15 ng/mL) normally observed 8 h after drug intake.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-01-19T14:06:17Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Flávia Moreno Duarte - 2014.pdf: 990547 bytes, checksum: 589026eb3ccc7e695e35abeb91deb9c4 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-01-19T14:06:33Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Flávia Moreno Duarte - 2014.pdf: 990547 bytes, checksum: 589026eb3ccc7e695e35abeb91deb9c4 (MD5) / Made available in DSpace on 2015-01-19T14:06:33Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação - Flávia Moreno Duarte - 2014.pdf: 990547 bytes, checksum: 589026eb3ccc7e695e35abeb91deb9c4 (MD5) Previous issue date: 2014-05-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Smell and taste are often impaired by neurodegenerative diseases, however, they have never been studied in association in individuals with cortical and subcortical neurodegenerative diseases in Brazil. This study aimed to evaluate the olfactory and gustative capacity of Parkinson’s disease (PD) individuals, comparing them to a group of subjects with cortical neurodegenerative diseases (CND) and to a control group. It was a cross-sectional study, with convenience sampling. PD individuals were recruited at the Reference Center of Movement Disorders of Clínicas Hospital at the Federal University of Goiás (Centro de Referência em Transtornos do Movimento do Hospital das Clínicas da Universidade Federal de Goiás) (n=80), CND patients were referred from a private clinic of Goiânia (n=20) and the control individuals, at the same age group of PD patients, neurodegenerative disease-free, came from several areas of Clínicas Hospital (n=40). Socio-demographic and clinical data were collected through direct interview and the use of a structured questionnaire including the following variables: gender, age, skin color, schooling, disease duration and stage and life habits. Olfactory capacity was assessed through Sniffin’ Sticks test (odor threshold, discrimination and identification) and gustative capacity through threshold and recognition test of the five basic tastes (sweet, savory, bitter, acid and umami). In order to test the association of olfactory and gustative capacity among the groups, Fisher’s exact test was used. For the comparison of detection and recognition thresholds’ means of basic tastes ANOVA and Kruskal-Wallis were used. PD and CND individuals presented, respectively, 93.8 % and 100 % olfactory compromising and only 15 % of control group individuals presented olfactory reduction, demonstrating statistically significant differences (p<0.001). There were also differences both in detection thresholds as in recognition thresholds of basic tastes among the groups (p<0.001), except for recognition threshold of acid taste (p= 0.088) and umami (p=0.153). Regarding gustative capacity, 53.8 % of PD patients, 50 % of CND individuals and 35 % of control group subjects presented no altered identification of basic tastes, however, there were no significant differences among the groups (p=0.150). It can be concluded that olfactory and gustative capacity in individuals with neurodegenerative diseases, both cortical and subcortical, is compromised and, consequently, presents itself as an important marker of these diseases. / Olfato e paladar estão frequentemente prejudicados nas doenças neurodegenerativas, contudo, nunca foram estudados conjuntamente em indivíduos com doenças neurodegenerativas corticais e subcorticais no Brasil. Este estudo teve como objetivo avaliar a capacidade olfatória e gustativa de indivíduos com doença de Parkinson (DP), comparando-os com um grupo de indivíduos com doenças neurodegenerativas corticais (DNC) e um grupo controle. O desenho do estudo foi transversal, com amostragem por conveniência. Os indivíduos com DP foram recrutados no Centro de Referência em Transtornos do Movimento do Hospital das Clínicas da Universidade Federal de Goiás (n=80), os pacientes com DNC encaminhados de uma clínica particular de Goiânia (n=20) e os controles, da mesma faixa etária do grupo DP, sem doenças neurodegenerativas foram oriundos das diversas áreas do Hospital das Clínicas (n=40). Dados sociodemográficos e clínicos foram coletados por meio de entrevista direta e uso de questionário estruturado abordando as variáveis: gênero, idade, cor da pele, escolaridade, duração e estágio da doença e hábitos de vida. Avaliou-se a capacidade olfatória por meio do teste Sniffin’ Sticks (limiar, discriminação e identificação de odores) e a capacidade gustativa por meio do teste de limiar e de reconhecimento dos cincos gostos básicos (doce, salgado, amargo, ácido e umami). Para testar a associação, da capacidade olfatória e gustativa entre os grupos, utilizou-se teste exato de Fisher. Para comparação de médias dos limites de detecção e de reconhecimento dos gostos básicos utilizou-se ANOVA e Kruskal-Wallis. Os indivíduos com DP e DNC apresentaram, respectivamente, 93,8 % e 100 %, de comprometimento no sentido do olfato e apenas 15 % dos indivíduos controles apresentaram redução no sentido do olfato, com diferenças significativas (p<0,001). Houve também diferenças tanto nos limites de detecção como nos limites de reconhecimento dos gostos básicos entre os grupos (p<0,001), exceto para o limite de reconhecimento do gosto ácido (p= 0,088) e do gosto umami (p=0,153). Em relação à capacidade gustativa, 53,8 % dos pacientes com DP, 50 % dos indivíduos do grupo DNC e 35 % dos indivíduos do grupo controle apresentaram alterações na identificação dos gostos básicos, porém não houve diferenças significativas entre os grupos (p=0,150). Conclui-se que a capacidade olfatória e gustativa em indivíduos com doenças neurodegenerativas, tanto corticais quanto subcorticais, estão comprometidas e, consequentemente, apresentam-se como um marcador importante dessas doenças.

Miniaturization is a key technological approach in current times. The most prominent examples of miniaturization are personal computers and mobile phones, but we observe miniaturization in other aspects of life, with the most recent example being small portable corona test kits. In science a big part of miniaturization focuses on detectors: to make them portable, to make them integrable into bigger, multi-function systems or to enable detection of smaller and smaller samples. For many experimental techniques highly sensitive and compact devices are already available, one of the extreme examples being single photon detectors. Compared to that, miniaturization of nuclear magnetic resonance (NMR) has still a long way to go in terms of both size and sensitivity. Recently, the successful miniaturization of an NMR coil was presented: on top of a flat polymeric bilayer a metallic layout is patterned. In an aqueous solution, one polymer layer absorbs water and swells, which induces strain between the two polymeric layers. This strain is released by a self-rolling-up of the bilayer, and the metal layer transforms into a microcoil. Such microcoils were successfully used for impedimetric measurements, as antennas, and as mentioned for NMR, but their performance in the latter was far from optimal. This thesis focuses on the optimization of rolled-up microcoils (RUMs) for NMR spectroscopy, with the goal to produce high-resolution and, most importantly, high-sensitivity microcoils. The performance of the microcoil can be expressed in three parameters, namely the spectral linewidth, the (normalized) limit of detection and the damping of a nutation curve, which was not a key parameter for this thesis. Both the microcoil design and the roll-up process have an influence on the quality of a RUM. For an optimal roll-up process, the polymeric bilayer layout needed some adjustment. The rolling process itself was improved through an addition of supporting structures on top of the bilayer, which resulted in tightly rolled tubes with a well-defined diameter. The coil layout was selected from several simple layouts. This layout was then optimized with the help of experiments and simulations. For example, an improvement in resolution was achieved through a reduction of the susceptibility of the metal. Finally, the coil was embedded into a microfluidic chip. This chip allows an easy sample supply into the coil interior and protects the coil from damage. As a side effect, the chip has a positive influence on the resolution of the detector. The best RUMs have a volume of only 1.5 nl, show a linewidth of only 8 ppb and a normalized limit of detection of 0.6 nmol√Hz at 600 MHz. The achieved resolution and sensitivity allow to resolve a 1H ethanol spectrum fully in a single measurement of 6 s duration. Compared to a standard shimmed NMR detector, where the linewidth is 0.65 ppb and the nLOD 10 nmol√Hz, the RUMs linewidth still needs some improvement, but the limit of detection is already an order of magnitude smaller. Combined with the fact that the limit of detection improves with linewidth, this shows the far superior sensitivity of RUMs compared to standard setups. A comparison with literature is also very promising, where optimized RUMs compete with the best published microcoils. Additionally, RUMs can be produced en masse, with, at the moment, four coils fitting on a single 50 x 50 mm2 glass substrate, while the best other microcoils were all made for single, specific experiments one at a time. And finally, the here presented recipe for self-assembled, RUMs is easily adaptable to even smaller sample volumes and to other coil layouts. It can be used to produce matching gradient coil systems and is a guideline on how to combine NMR and other techniques while maintaining a high NMR performance.:Introduction Nuclear magnetic resonance 1 NMR principle 1.1 A single nucleus in a magnetic field 1.2 Multiple spins in external field 1.3 Spins in natura 1.4 Typical liquid state spectrum 1.5 Typical NMR setup 2 Properties of an NMR detector 2.1 Quality of rf-field 2.2 Resolution 2.3 Signal-to-noise ratio 2.4 How to optimize a microcoil 3 Existing microdetectors 3.1 Solenoids 3.2 Saddle coils 3.3 Flat coils 3.4 Striplines/Microslots 4 Comparing microdetectors 4.1 The limit of detection 4.2 Performance of published microcoils Self-assembly 5 What is self-assembly? 6 Self-assembly in microfabrication 6.1 Macroscopic self-assembly 6.2 Self-rolled tubes 7 Self-assembly of rolled-up microcoils 7.1 Working principle 7.2 Experimental methods for self-assembly 8 Encapsulating rolled-up tubes 8.1 Microfluidics 8.2 Microfluidic chip 8.3 Experimental methods for encapsulation Rolled-up microcoils 9 Fabrication 9.1 Bilayer 9.2 Coil geometry 9.3 Metal stack 9.4 Supporting elements 9.5 Rolling process 9.6 Final layout 9.7 Microfluidic integration 10 Reducing susceptibility-induced field distortions 10.1 Simulating field distortions 10.2 Influence of the coil shape 10.3 Susceptibility matching 11 NMR performance 11.1 Measurement setup 11.2 Quality of rf-field 11.3 Resolution and sensitivity 11.4 Comparison to published microcoils 12 Outlook 12.1 Further improvements to rf-field, FWHM and nLOD 12.2 New coil shapes 12.3 New applications Summary Appendix A Simulation and maths A.1 Filling factor and rf-homogeneity A.2 Nutation and rf-homogeneity A.3 FT of one-sided exponential A.4 DFT A.5 Programs B Protocols B.1 Polymeric platform B.2 Metal layers C Test protocols C.1 Wet etching D Calculations for nLODs

The diploma thesis deals with the use of laser induced breakdown spectroscopy (LIBS) for detection of heavy metals traces, copper and lead, in aqueous solution of copper(II) sulphate pentahydrate and lead(II) ethanoate trihydrate. Results obtained by using single and double-pulse LIBS are compared. The theoretical section focuses on the issue of heavy metals and detection possibilities, describes the fundamental principle of LIBS technique and its modification for liquid analysis. The experimental section describes analyzed samples, the experimental apparatus, double-pulse technique, and method of spectral analysis. The moving breakdown model, which theoretically predicts optimal values of some experimental parameters, is explained briefly in section Optimalizácia. This model has been tested, however the results of experiments did not prove the theory. Furthermore, the experimental section reports the process and results of the optimization of all key measurement parameters and obtaining limits of detection from calibration curves.

>Magister Scientiae - MSc / infarction (MI) affects many parts of the western world and in South Africa alone it is estimated that MI is responsible for 1 in 6 deaths (17.3%). Traditional diagnostic methods for MI include an electrocardiograms and blood tests. The problem with these diagnostic methods are that they are time consuming, require large sample volumes, expensive equipment and complicated machinery. To achieve early detection of MI the discovery of specific, sensitive and reliable biomarkers are required. Brain natriuretic peptide (BNP) has been identified as a reliable biomarker for MI due to the fact that it has a defined cutoff of 100 pg/ml and it is not susceptible to patient‘s age which could make early detection of BNP complicated. Early detection methods for BNP has been based on immunoradiometric assays but problems associated with immunoradiometric assays are that there is a restricted availability of antigens and incubation of the labeled antibody could take up to two weeks which affects the patients waiting time on results. Electrochemical biosensors are emerging as early detection method for MI because they can be designed to be sensitive, specific to BNP at a low cost. This research study reported for the first the successful fabrication and implementation of highly sensitive mercaptosuccinic acid capped nickel selenide quantum dots (MSA-NiSe2 QDs) aptasensor for the detection of BNP. The poly-dispersed MSA-NiSe2 QDs were synthesized via an inexpensive, simple and reproducible aqueous microwave assisted irradiation method. The prepared MSA-NiSe2 QDs were characterized by Ultraviolet spectroscopy (UV-Vis), X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), High Resolution Transmission/Scanning Electron Microscopy (HR TEM/SEM) and Small Angle X-ray Scattering (SAXSpace). The electrochemical properties of the MSA-NiSe2 QDs were investigated by Cylic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). HR-TEM revealed the formation of small sized MSA-NiSe2 QDs about 4 nm in diameter which was complemented by SAXSpace. UV-Vis studies showed absorption peaks in the ultraviolet region (100-400 nm) confirming the small size of these QDs as well confirming the direct and indirect bandgap of the QDs. XRD confirmed that the QDs are crystalline and belong to the bulk cubic MSA-NiSe2 QDs phase. FTIR studies confirmed the successful capping of MSA on the QDs due to the disappearance of the thiol peak at 2652 cm-1. Electrochemical studies revealed that the MSA-NiSe2 QDs showed good electrochemical properties on screen printed carbon electrodes (SPCE) which allowed them to be used as a mediating platform between the aptamer and SPCE. The successful detection of BNP was achieved by an incubation process between the aptamer drop coated on the MSA-NiSe2 QDs/SPCE surface overnight. The response of the MSA-NiSe2 QDs based aptasensor towards different concentrations of BNP was studied by differential pulse voltammetry (DPV). DPV showed a good linearly with correlation coefficient of R2 = 0.98. DPV also showed a high sensitivity (0.4513 μA/ pg/mL) towards detecting BNP with a detection limit of 11.93 pg/ml. The value of 11.93 pg/ml falls within the negative predictive value range of 10-100 pg/ml for early-stage diagnosis of BNP.

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<p>In 2021, an estimated 1.5 million people were diagnosed with HIV globally, increasing the total to 38.4 million people. Approximately 16% of this population were unaware of their infected status and required HIV testing, which is a critical first step in HIV prevention, treatment, and care. Hence, there is a need to develop a rapid, user-friendly, and cost-effective point-of-care test for HIV detection. The time between HIV infection and a detectable host HIV antibody concentration can extend up to 90 days. By incorporating more sensitive testing for the HIV p24 antigen on the virus, the diagnosis lag can be reduced to 17 days. This window could be further shortened by using horseradish peroxidase (HRP) enzyme as a signal enhancement technique. The work herein focuses on developing an enzymatically signal-enhanced lateral flow assay test for the p24 antigen to detect HIV during the acute phase of infection. Conjugation chemistry for the sandwich assay was characterized using DLS and UV-Vis. Dot blots were then used to assess and enhance the functionality of the individual components via a visual color gradient formed by the protein coupled with antibody-conjugated gold nanoparticles. A quantitative analysis was performed using ImageJ software through signal pixel intensity analysis. A limit of detection (LoD) of 6 ng/mL was obtained for the detection of the p24 antigen. This LoD was improved to 0.2 ng/mL by incorporating HRP signal enhancement with the diaminobenzidine substrate. This 30x signal improvement could drive down the LoD even further to improve the sensitivity of the commercial p24 antigen tests. Different fabrication and scalability studies were performed to produce a cost- efficient, fully functional prototype of a paper-based lateral flow device incorporating the signal- enhanced p24 assay. This study serves as a solid foundation to research focused on creating more efficient point-of-care tests that can be used in resource-limited settings to provide early detection of HIV for the 6 million individuals who are currently unaware of their HIV status. </p>