Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 75-82). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 18, 2007) Vita. Includes bibliographical references.

Thesis (Ph.D.) OGI School of Science & Engineering at OHSU, October 2007. / Includes bibliographical references (leaves 149-152).

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 27, 2007) Includes bibliographical references.

No description available.

Magister Scientiae - MSc / Selective serotonin re-uptake inhibitors (SSRIs) are a new class of antidepressants used mainly for the treatment of depression and other forms of related disorders. There are a number of side effects associated with these drugs which include loss of weight, sexual dysfunction, nervousness and nausea. A fast and reliable detection method such as biosensing for the determination of the SSRIs metabolic profile is therefore essential for the appropriate dosing of these drugs. Biosensors for the determination of the SSRIs biotransformation were prepared with cytochrome P450 (2D6) isoenzyme and poly (anilinonapthalene sulfonic acid) film electrochemically deposited on gold. / South Africa

Orientador: Valber de Albulquerque Pedrosa / Banca: Paulo dos Santos Roldan / Banca: Margarida Juri Saeki / Dissertação (mestrado) - Universidade Estadual Paulista "Julio de Mesquita Filho", Faculdade de Ciências de Bauru / O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi / Resumo: This project has as main objective the development of nanowires for application in biosensors. Nanomaterials have been highlighted by high sensitivity when applied to biological sensors. As they haver virtually the same dimensions as the molecules that should detect, these nanosensors could revolutionize the diagnoses way are made in medical and biological examinations. Therefores, in this research, we prepared and characterized multithreaded nanowires usind different types of metal and polymer. These nanowires were prepared by electrochemical deposition process and characterized by scanning electron microscopy (SEM). The synthesized nanowires have been changed for the attachment of the enzyme glucose oxidase. Several experimental parameters of biosensor was evaluated as the optimization of pH (at 6), as a function of the peak current obtained from glucose; the enzyme concentration of 0,4 mg ml-1 required to prepare the biosensor; as well as the study of electrochemical potential variation, where it was observed that the ideal is to use potential less than 0,4 V. The analyitcal curve for the determination of glucose showed a slope of 7.95 uA mol-1, with a correlation coefficient of 0.997 and detection limit of the biosensor determined was 3.7 x 10-7 mol L-1. The biosensor showed high selectivity only for detection of glucose and maintained a good response to glucose sensing (85%) in 30 days. Thus, the use of nanowires for the preparation of biosensors becomes and alternative to direct detection of glucose; the enzyme concentration of 0.4 mg ml-1 required to prepare the biosensor; as well as the study of electrochemical potential less than 0.4 V. The analytical curve for the determination o glucose showed a slope of 7.95 uA mol-1, with a correlation coefficient of 0.997 and detection limit of the biosensor... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This project has as main objective the development of nanowires for application in bionsensors. Nanomaterials have been highlighted by high sensitivity when applied to biological sensors. As they have virtually the same dimensions as the molecules that should detect, these nanosensors could revolutioneze the diagnoses way are made in medical and biological examinations. Therefore, in this research, we prepared and characterized multithreaded nanowires using different types of metal and polymer. These nanowires were prepared by electrochemical deposition process and characterized by scanning electron microscopy (SEM). The synthesized nanowires have been changed for the attachment of the enzyme glucose oxidase. Several experimental parameters of biosensor was evaluated as the optimization of pH (at 6), as a function of the peak current obtained from glucose; the enzyme concentration of 0.4 mg ml-1 required to prepare the bionsensor; as well as the study of electrochemical potential variation, where it was observed that the ideal is to use potential less than 0.4 V. The analytical curve for the determination of glucose showed a slope of 7.95 uA mol-1, with a correlation coefficient of 0.997 and detection limit of the biosensor determined was 3.7 x 10-7 mol L-1. The biosensor showed high selectivity only for detection of glucose and maintained a good response to glucose sensing (85%) in 30 days. Thus, the use... (Complete abstract click electronic access below) / Mestre

Intracellular redox potential affects cellular function and its dysregulation is associated with disease. Current methods of monitoring intracellular redox potential are limited because they typically only report potentials of the redox buffer glutathione. Our group has developed redox-active probe molecules that change bond order depending on the probe oxidation state, and are instead sensitive to overall redox potential within the cell. Gold nanoshells coated with the probe form a novel intracellular redox nanosensor, and spectral discrimination of the oxidised and reduced states by Surface-Enhanced Raman Scattering (SERS) allows calculation of redox potential. Prior work by the group provided basic proof-of-principle for its use in measuring intracellular redox potential. The aim of this project, therefore, was to develop the tools and techniques to enable its application to meaningful biological questions, and extend the method into a pathologically relevant cell line. The initial stages of the project standardised the functionalisation of gold nanoshells with the NQ probe molecule and the application of the nanosensors to the A549 human lung cancer cell line. Toxicity tests confirmed the nanosensor was non-toxic. A protocol was then developed for rapidly obtaining SERS maps to enable localisation of nanosensors within the cell. This was successful, and the protocols can be applied to any combination of adherent cell type and nanosensor. A bespoke piece of software was created to determine redox potential and pH from SERS maps to produce a colourmap showing spatial variation of redox potential and pH with subcellular resolution. This software enables more rapid and precise calculation of redox potential or pH than manual processing. As a test case, changes in intracellular redox potential in response to treatment with toxic metal nanoparticles were studied and shown to correlate with other measures of oxidative stress. Hypoxia (abnormally low oxygen levels) is relevant in disease. Investigating redox potential in hypoxic cells requires precise control of the oxygen concentration during the acquisition of SERS spectra. To facilitate such experiments, a specialised imaging chamber was designed, constructed and tested. Such environmental control enables experiments to be carried out at various oxygen concentrations as well as under optimal cellular physiological conditions, enabling not only the response to alterations in oxygen levels to be studied but also extending the biological model system to more closely reflect animal physiology. Finally, a device was constructed that allowed the acquisition of SERS spectra from both intracellular and extracellular nanosensors in the same experiment, as the relationship between intracellular and extracellular redox potential is incompletely understood. The intracellular and extracellular nanosensors are spatially separated, allowing clear discrimination of the SERS spectra obtained simply by changing the orientation of the device. This device enables the effect of quantitative modification of extracellular redox potential on intracellular redox potential to be investigated. In summary, the work has greatly extended a method of measuring intracellular redox potential. It was taken from the proof-of-principle stage to being a robust method, capable of providing useful quantitative biological information. Improvements have been made in production and toxicity testing of the nanosensors, robustness of SERS data acquisition and analysis, environmental control during SERS data acquisition and application to disease-relevant cell culture models. The result is that we are now able to rapidly and reproducibly determine intracellular redox potential in single cells.

Made available in DSpace on 2014-11-10T11:09:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-04-25Bitstream added on 2014-11-10T11:58:20Z : No. of bitstreams: 1 000773536_20161212.pdf: 666854 bytes, checksum: c983f025f8c552641bf7430c84326894 (MD5) Bitstreams deleted on 2016-12-12T11:23:44Z: 000773536_20161212.pdf,. Added 1 bitstream(s) on 2016-12-12T11:24:26Z : No. of bitstreams: 1 000773536.pdf: 2206448 bytes, checksum: e1c9544c3f226058be35c3855241d242 (MD5) / O presente trabalho apresenta o desenvolvimento de biossensor baseado em extrato de açaí e sensor biomimético baseado em polímeros de impressão molecular, para a determinação eletroquímica da hexazinona–HXZ (3-ciclohexila-6-(dimetilamino)-1-metil-1,3,5-triazina-2,4(1H,3H)-diona) empregando eletrodos de pasta de carbono e de ouro. O sensor biomimético à base de pasta de carbono foi construído usando polímeros biomiméticos, MIPs (Moleculary Imprinted Polymer). As sínteses dos MIPs e dos respectivos polímeros de controle NIPs, foram realizadas pelos métodos de bulk e de precipitação. O comportamento eletroquímico do sensor biomimético foi estudado por voltametria cíclica e a quantificação da hexazinona foi realizada utilizando voltametria adsortiva de pulso diferencial com redissolução catódica (DPAdCSV). Sob estas condições, obteve-se uma faixa de resposta para HXZ, entre 2,0 x 10-11 e 1,1 x 10-10 mol L-1, e um limite de detecção de 5,8 x 10-12 mol L-1, o sensor biomimetico foi aplicado para a determinação de hexazinona em agua utilizada em uma plantação de cana de açucar, obtendo-se uma recuperação de 98%. No biossensor, a base do extrato de açaí usou-se um eletrodo de ouro cuja superfície foi modificada com monocamadas auto-arranjadas (SAM) de cistamina sobre a qual foi imobilizada a enzima peroxidase extraída da polpa de açaí (Euterpe oleracea). A voltametria de onda quadrada foi a técnica utilizada na otimização e quantificação do herbicida, obtendo-se uma resposta para HXZ de 2,0 x 10-5 até 1,1, x 10-4 mol L-1 e limite de detecção de 6,6 x 10-6 mol L-1. Os resultados obtidos mostram que os sensores propostos são promissores para a quantificação da hexazinona. / The present work describe the development of electrochemical biosensors and biomimetec sensor for the determination of hexazinone-HXZ (3-ciclohexyl-6- (dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione) employing carbon paste and gold electrodes. The biomimetic sensor based on carbon paste was prepared using molecularly imprinted polymers (MIPs). The syntheses of MIPs and the respective control polymers, NIPs, were performed by bulk and precipitation methods. The electrochemical behavior of biomimetic sensor was studied by cyclic voltammetry and the quantification of hexazinone was performed using differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV). Under these conditions response range was obtained for HXZ between 2.0 x 10-11 e 1.1 x 10-10 mol L-1 and detection limit of 5.8 x 10-12 mol L-1. the biomimetic sensor was applied to real samples of a sugar plantation, the recovery was 98% The In the second sensor gold electrode was used whose surface was modified with self-assembled monolayers (SAM) of cystamine on which was immobilized peroxidase enzyme extracted from the pulp of Açai (Euterpe oleracea). The square wave voltammetry technique was used in the optimization and quantification of the herbicide having response for HXZ 2.0 x 10-5 up to 1.1 x 10-4 mol L-1 and detection limit of 6.6 μmol L-1. The results obtained show that the proposed sensors are promising for the quantification of this pesticide.

The main tasks of this thesis were to evaluate a number of amperometric enzyme electrode chemistries for the selective and sensitive detection of L-lactate, and apply mass fabrication technologies to reproducibly manufacture sensors in a controllable manner. The sensors studied were based on the use of lactate oxidase with a range of modified-carbon electrodes. Noble metals, hexacyanoferrate (111) or Prussian Blue were used to modify carbon electrodes for the electro-catalytic determination of hydrogen peroxide, the product of the reaction of lactate oxidase with L-lactate. Tetrathiafulvalene was employed as an artificial mediator between the enzyme and the electrode. Polypyrrole was tested as a means of immobilising lactate oxidase and to achieve direct charge transfer to the underlying carbon electrode. The characteristics of the sensor responses to hydrogen peroxide, L-lactate and ascorbate were compared, in relation to the electrochemical electrode area. From this investigation, it was confirmed that screen-printed electrodes were more reproducible to manufacture than hand-fabricated electrodes. For screen-printed rhodinised-carbon electrodes, an operating potential of +400 mV (SCE) was selected. Interference from ascorbic acid and sensitivity to hydrogen peroxide were determined to be 26 μA.mM⁻¹.cm⁻² and 27 μA.mM⁻¹.cm⁻², respectively. Screen-printed carbon electrodes modified with platinum, rhodium or palladium were selected for further investigation. Rhodium on carbon performed the best in ten-ns of sensitivity and selectivity at low potentials, and different formations of rhodium-carbon complexes were studied. Although rhodium electroplated onto carbon screen-printed electrodes was examined, printing inks made from a preformed powder of rhodium on carbon-graphite proved to be the preferred route of electrode fabrication. Screen printing, ink-jet printing and Cavro solution deposition were employed to fabricate the amperometric enzyme electrodes. These sensors were composed of rhodinised carbon and lactate oxidase in a water-based electrode ink with a protective outer membrane layer. Each stage, from ink preparation to membrane composition, was developed empirically. The sensitivity, stability and reproducibility of the working electrode was improved by altering it to a homogeneous ink, consisting of carbon graphite powder, rhodinised carbon powder (5% Rh by weight), hydroxyethyl cellulose (2% w/v) and lactate oxidase in the weight ratio of 2:8:18:1. A layer of cellulose acetate (2% w/v in a 1:1 solution of acetone to cyclohexanone) and an outer coating of a polyurethane called Pellethane (1% to 4% w/v in dimethyl formamide and tetrahydrofuran) improved the selectivity, sensitivity and detection range of the sensor, allowing it to operate in physiological solutions with reduced passivation from protein adsorption. The sensor design was revised to allow its passage through a catheter and operation within a blood vessel; it was manufactured on flexible material using screen printing and Cavro solution deposition techniques. These miniature sensors, with a working surface of 0.5 x 15 mm, were capable of linearly measuring lactate up to 3 mM in buffer solutions with an average sensitivity of 44.8 nA.mM⁻¹ L-lactate. To test the sensor operation in physiological solutions, a flow injection system was employed. A planar three-electrode card used in this system was manufactured using screen printing and Cavro solution deposition techniques. L-lactate concentrations up to 6.4 mM were sensitively and, after minor correction, accurately determined in undiluted plasma and whole blood samples. This thesis has therefore made progress toward mass fabricating an amperometric enzyme electrode device suitable for the determination of L-lactate concentrations in vitro.