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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

Du polymère à empreintes moléculaires électrochimiques au capteur : Etude de faisabilité pour la détection du Bisphénol A / From electrochemical molecularly imprinted Polymer to Sensor : feasibility study for the detection of Bisphenol A

Mba Ekomo, Vitalys 12 July 2018 (has links)
Les polymères à empreintes moléculaires sont des matériaux aux propriétés de reconnaissance spécifiques qui peuvent être mis à profit pour la détection d’une large gamme d’analytes. Ainsi, depuis quelques années, des travaux décrivent leur utilisation dans des capteurs en raison de leur capacité à piéger une cible définie.L’objectif de ce travail est d’ajouter des propriétés redox à des polymères à empreintes moléculaires pour détecter le Bisphénol A (BPA) par des méthodes électrochimiques simples. Ces polymères électroactifs sont synthétisés par polymérisation par précipitation d’une sonde redox, le méthacrylate deméthylferrocène (Fc), et du diméthacrylate d’éthylène glycol (EDMA) en présence du BPA pour le polymère imprimé (e-MIP-Fc) et en son absence pour le polymère non-imprimé (e-NIP-Fc).L’introduction d’un deuxième monomère fonctionnel, la 4-vinyl pyridine (4-VP), conduit à deux autres polymères imprimé (e-MIP-Fc-VP) et non-imprimé (e-NIP-Fc-VP). Les propriétés d’adsorption des polymères ainsi obtenus sont caractérisés en batch à l’aide de la LC-MS et présentent une capacité de reconnaissance du BPA avec un facteur d’empreinte de 2,5 et 1,3 respectivement pour l’e-MIP-Fc-VP et e-MIP-Fc justifiant de l’efficacité de l’empreinte. Leurs caractérisations par voltampérométrie cyclique confirment d’une part la bonne intégration du monomère ferrocényle dans les e-MIP/e-NIP et d’autre part la capacité de ces polymères à révéler la présence ou pas de la cible. Les particules e-MIP-Fc ont ensuite été intégrées dans des dispositifs type micro électrode ou transistor OECT (Organic ElectroChemical Transistor). Les premiers résultats, mêmes s’ils doivent être confirmés, s’avèrent encourageants avec,comme attendu, des modifications des propriétés électriques en présence du BPA. L’e-MIP-Fc-VP après mélange avec de la pâte de carbone, a été utilisé en sérigraphie pour obtenir une électrode de travail modifiée dans des électrodes sérigraphiées (Screen Printed Electrode). Ces électrodes permettent la reconnaissance du BPA avec des limites de détection et de quantification de 60 pM et 190 pM respectivement pour une gamme de concentrations comprise entre 0,15 et 1,84 nM, ouvrant ainsi des perspectives intéressantes pour la détection du BPA en milieu aqueux. / Molecularly imprinted polymers are materials with specific recognition properties that can be used for the detection of a wide range of template. In recent years, many works have been reported on their use in sensors because of their capability to specifically bind a defined analyte.The aim of this work is to assign to the molecularly imprinted polymers redox properties in order to detect Bisphenol A (BPA) by using easy electrochemical techniques. These electroactive polymers are synthesizedby precipitation polymerization of ferrocenylmethyl methacrylate (Fc) and ethylene glycol dimethacrylate(EDMA) in the presence of BPA for the imprinted polymer (e-MIP-Fc) and in its absence for the nonimprinted polymer (e-NIP-Fc). The copolymerization of the previous monomer with 4-vinylpyridine (4-VP) leads to two other imprinted (e-MIP-Fc-VP) and non-imprinted (e-NIP-Fc-VP) polymers. The resulting polymers are characterized in batch using LC-MS and have ability to recognize BPA with an imprinting factor of 2.5 and 1.3 respectively for e-MIP-Fc-VP and e-MIP-Fc the proving the recognition efficiency ofthese polymers. Their cyclic voltammetry recording confirm first, the good integration of the redoxferrocenyl monomer inside the polymers e-MIP/e-NIP during the polymerization, and on the other hand,the capability of these polymers to reveal the presence of BPA in the solution. The e-MIP-Fc particles were then integrated inside devices like microelectrode and OECT (Organic ElectroChemical Transistor). The first results, even if they must be confirmed, are positive regarding the modification of the electrical properties of these devices in the presence of BPA. The e-MIP-Fc-VP particles, after mixing with a carbon paste, were screen-printed to obtain a modified working electrode in a screen-printed electrode device. This electrode enable the recognition of BPA with limits of detection and quantification of 60 pM and 190 pM respectively, for a concentration range between 0.15 and 1.84 nM, thus opening up interesting perspectives for the detection of BPA in aqueous medium.
2

Facile Nitrogen-Doping of Screen-Printed Carbon Electrodes for Detection of Hydrogen Peroxide

Nkyaagye, Emmanuel 01 December 2021 (has links)
Screen-printed carbon electrodes (SPCEs) have garnered much attention as sensors due to their simplicity and relatively low cost. However, to impart necessary selectivity and sensitivity for specific applications, modification of the SPCE surface, which can involve time-consuming procedures or costly equipment/materials, is typically required. Here, a simple nitrogen-doping process based on NH4OH was used to modify SPCEs prepared from commercially available ink for electrochemical detection of H2O2, a common target for biosensing strategies and indicator of cell stress. XPS studies showed that NH4OH treatment of SPCEs led to a nearly 5-fold increase in surface nitrogen content (from 0.28% to 1.34%). Compared to SPCEs, nitrogen-doped SPCEs (N-SPCEs) demonstrated enhanced current and lower onset potentials for H2O2 reduction. Amperometric detection of H2O2 at an applied potential of -0.4 V (vs. Ag/AgCl) using N-SPCEs also exhibited a wider linear range, lower detection limit, and higher sensitivity than SPCEs.
3

Nitrogen Doping of Electrochemically Activated Carbon Screen Printed Electrodes

Galloway, Ethaniel L, Bishop, Gregory W, Ph.D. 06 April 2022 (has links)
Screen printed electrodes (SPEs), which are prepared by patterning conductive inks or pastes onto an insulating support (e.g., plastic film), are widely employed as sensing and biosensing platforms due to their ease of fabrication and relatively low cost. This is especially applicable to electrodes of this nature prepared with carbon-based inks (SPCEs). To date, the most successful and significant commercial application of SPEs has been as test strips for glucose meters. Despite the maturity of this technology, SPE research remains very active as improvements in sensitivity and selectivity, which often involve modifying the electrode surface, hold the key to advancing their utility in routine applications and extending their benefits to other target analytes. Recent studies in the Bishop research group have demonstrated that nitrogen-doped SPCEs (N-SPCEs) exhibit enhanced electrochemical response towards hydrogen peroxide (H2O2), a product of oxidase enzyme (e.g., glucose oxidase, lactate oxidase, etc.) reactions and a common target in biosensing strategies. The presence of nitrogen heteroatoms on the carbon surface facilitates breakage of oxygen-oxygen bonds, a key step in reduction of H2O2. Since previous studies showed only modest incorporation of nitrogen species on SPCEs prepared from commercial ink, these studies aim to investigate the possibility of enhancing N-doping by performing a simple pre-treatment strategy that reportedly increases surface oxygen content of SPCEs prior to N-doping. Since surface oxygen sites have been previously reported to be preferentially modified with nitrogen during N-doping strategies, this seems like a promising technique for improving sensitivity of N-SPCEs for H2O2 reduction. To quantify the actuality of these claims, experimental groups were fabricated having undergone no enhancement, pretreatment enhancement only, nitrogen-doping enhancement only, and a combination of the pretreatment and nitrogen-doping enhancements. Here the electrochemical behaviors of pretreated SPCEs, N-SPCEs, and pretreated N-SPCEs for the detection of H2O2 by completing comparative cyclic voltammetry (CV) experiments with and with out the presence of H2O2 and with it present in varying concentrations is compared. It is projected that, if successful, the fabricated electrodes that have undergone both the pretreatment protocol and the nitrogen-doping process will have an increased sensitivity and detection limit towards H2O2.
4

Peroxide Sensing Using Nitrogen-Doped and Platinum Nanoparticle-modified Screen-Printed Carbon Electrodes

Ogbu, Chidiebere 01 August 2019 (has links)
Nitrogen-doped carbon materials have garnered much interest due to their abilities to behave as electrocatalysts for reactions important in energy production (oxygen reduction) and biosensing (hydrogen peroxide reduction). Here, we demonstrate fabrication methods and determine electrocatalytic properties of nitrogen-doped screen-printed carbon (N-SPCE) electrodes. Nitrogen doping of graphite was achieved through a simple soft-nitriding technique which was then used in lab-formulated screen-printing inks to prepare N-SPCEs. N-SPCEs displayed good electrocatalytic activity, reproducibility and long term stability towards the electrochemical reduction of hydrogen peroxide. N-SPCEs exhibited a wide linear range (20 µM to 5.3 mM), reasonable limit of detection of 2.5 µM, with an applied potential of -0.4 V (vs. Ag/AgCl). We also demonstrate that nitrided-graphite can similarly be used as a platform for the deposition of electrocatalytic platinum nanoparticles, resulting in Pt-N-SPCEs with a lower limit of detection (0.4 µM) and better sensitivity (0.52 µA cm-2 µM-1) towards H2O2 reduction.
5

Electrochemiluminescence using Pencil Graphite Electrodes and Screen-printed Carbon Electrodes Interfaced with a Simple Imaging System

Ehigiator, Sandra 01 May 2024 (has links) (PDF)
Electrochemiluminescence (ECL) is a phenomenon whereby electrochemical reactions generate a product that is capable of emitting light. ECL’s high sensitivity, selectivity, extremely low background, and relatively simple instrumentation make it particularly well-suited for chemical sensing and biosensing strategies. Here we report a simple ECL imaging system based on a camera interfaced with a zoom lens to compare pencil graphite electrode (PGE) and screen-printed carbon electrode (SPCE) arrays as ECL platforms. With this system, ECL signals generated from tris(2,2′- bipyridine)ruthenium(II) chloride hexahydrate ([Ru(bpy)3]2+) using co-reactant tri-n-propylamine (TPA) were linear with respect to [Ru(bpy)3]2+ concentrations from 9 to 450 μM. Detection limits for [Ru(bpy)3]2+ were found to be 1.8 μM with PGEs and 0.9 μM with SPCEs. Immobilization of a thin polyvinylpyridine (PVP) film ECL reporter [Ru(bpy)2(PVP)10]2+ on SPCEs was also investigated. Overall, the combination of PGEs or SPCEs with the simple ECL imaging system offers a cost-effective approach to ECL-based sensing and biosensing.
6

Vliv způsobu předúpravy tištěných uhlíkových elektrod na jejich elektrochemické chování / Effect of pretreatment methods on electrochemical behavior of screen-printed carbon electrodes

Weiss, Vojtěch January 2017 (has links)
The aim of this work is the thick-film electrochemical sensor characterization. In the theoretical part, the thesis describes sensor, three-electrode system, characterization electrode using cyclic voltammetry and electrode pretreatment methods. The experimental part compares the results of cyclic voltammetry of bare carbon electrodes, chemically pre-treated electrodes, electrochemically pre-treated electrodes and electrodes modified by plasma oxidation.
7

Desenvolvimento de dispositivos eletroquímicos baseados em papel para monitoramento não invasivo de lactato em suor / Development of wearable electrochemical paper-based devices for noninvasive monitoring of lactate in sweat

Gomes, Nathalia Oezau 22 February 2019 (has links)
O lactato é um metabólito chave formado pelo metabolismo anaeróbico da glicose nos músculos, e tem se tornado um biomarcador importante no âmbito clínico e esportivo. Atualmente, existem biossensores eletroquímicos portáteis que são capazes de determinar os níveis de lactato no organismo em tempo real. No entanto, tal método é invasivo uma vez que requer amostras de sangue. O presente projeto tem como objetivo desenvolver um biossensor eletroquímico descartável para detecção de lactato no suor. Para isto a configuração do dispositivo foi feita utilizando a celulose bacteriana como substrato para obtenção de um dispositivo que seja resistente à deformação mecânica, especialmente quando molhado e, também, permeável ao suor. A impressão dos eletrodos de carbono neste substrato foi efetuada utilizando o processo de serigrafia. Com os dispositivos produzidos foram realizados experimentos de voltametria cíclica e espectroscopia de impedância eletroquímica, a fim de caracterizar o sensor desenvolvido e investigar a influência do pré-tratamento eletroquímico na sua performance analítica. A partir da modificação da superfície eletródica com nanocubos de Azul da Prússia foi possível desenvolver um sensor eletroquímico para detecção de peróxido de hidrogênio. A cronoamperometria foi utilizada para a determinação da curva analítica para o peróxido de hidrogênio. Com todos os parâmetros da cronoamperometria otimizados, uma dependência linear da corrente catódica com a concentração de peróxido de hidrogênio foi obtida, com a equação: Ip = 0,1 + 4,30 [H2O2], com r2 = 0,999 (n = 3). Esta curva analítica mostrou que a metodologia apresenta um Limite de Detecção e de Quantificação de mol L-1 e mol L-1, respectivamente. Para a configuração do biossensor eletroquímico a enzima lactato oxidase foi incorporada à superfície do papel pelo método de ligação covalente. Adotando esta metodologia foi verificado um aumento da área eletroativa que possibilitou uma melhora significativa no desempenho do sensor desenvolvido. No qual se obteve uma região linear de 1-24,0 mmol L-1 em suor sintético, obtendo-se Limites de detecção e Quantificação de e mol L-1. Tais parâmetros se mostraram adequados já que o suor pode apresentar níveis de aproximadamente 25 mmol L-1 de lactato. De modo geral, foi possível desenvolver uma plataforma eletroquímica no substrato de celulose bacteriana para a detecção de lactato em amostras de suor sintético. O dispositivo desenvolvido apresentou uma boa durabilidade e resistência ao se executarem sucessivas medidas corroborando a viabilidade deste substrato na projeção de sensores vestíveis para a aplicação direta na pele e monitoramento dos níveis de lactato em tempo real. / Lactate is a key metabolite formed in the anaerobic metabolism of glucose in the muscles. It has become an important biomarker in the clinical and sport scopes. Currently, there are portable biosensors that are able to determine lactate levels in real time. However, these methods are invasive since they require blood samples. Herein, we aim to develop a disposable wearable electrochemical biosensor for detection of lactate in sweat. For this purpose the configuration of the device was made with bacterial cellulose substrate in order to be permeable to sweat and resistant to mechanical deformation, especially when wet. The fabrication of the electrodes was made through screen printing technique. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the sensor developed in order to investigate the influence of the electrochemical pre-treatment in the analytical performance of the electrodes. To develop an electrochemical sensor for the detection of hydrogen peroxide the screen printed electrode was modified with Prussian blue nanocubes. Chronoamperometry experiments were used to detect of hydrogen peroxide. From optimized chronoamperometry parameters, a linear dependence of the cathodic current with the hydrogen peroxide concentration was obtained with the equation: Ip = 0.1 + 4.30 [H2O2], with r2 = 0.999 (n = 3). The limit of detection (LOD) and the limit of quantification (LOQ) were mol L-1 e mol L-1, respectively. For the configuration of the electrochemical biosensor the lactate oxidase enzyme was immobilized on the paper surface by the covalent bonding method. Adopting this methodology was verified an increase of the electroactive area that allowed a significant improvement in the performance of the developed sensor. In which a linear concentration range of 1-24.0 mmol L-1 was obtained in the synthetic sweat, obtaining LOD and LOQ of mol L-1 e mol L-1, respectively. Such parameters were adequate since sweat may have lactate levels of approximately 25 mmol L-1. Finally, it was possible to develop an electrochemical platform using the bacterial cellulose substrate for the detection of lactate in samples of synthetic sweat. The developed device presented a good durability and resistance when performing electrochemical measurements assuring the feasibility of this substrate in the projection of wearable sensors for the direct application to skin and monitoring of lactate levels in real time.
8

Detecção e quantificação eletroquímica de substâncias de interesse clínico, ambiental e forense utilizando eletrodo de pasta de grafite modificado com trisilanol poss ligado a suportes porosos e eletrodos impressos obtidos via screen-printed / Electrochemical detection and quantification of clinical, environmental and forensic interest substances using carbon paste electrode modified with trisilanol-poss bonded to porous supports and screen-printed electrodes

Cumba, Loanda Raquel [UNESP] 04 March 2016 (has links)
Submitted by LOANDA RAQUEL CUMBA null (loandacumba@gmail.com) on 2016-04-18T17:28:50Z No. of bitstreams: 1 Tese Final - Loanda Cumba (2016).pdf: 4586367 bytes, checksum: c39a78169180c1ccedbe3f393fccbaee (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-04-19T16:39:26Z (GMT) No. of bitstreams: 1 cumba_lr_dr_ilha.pdf: 4586367 bytes, checksum: c39a78169180c1ccedbe3f393fccbaee (MD5) / Made available in DSpace on 2016-04-19T16:39:26Z (GMT). No. of bitstreams: 1 cumba_lr_dr_ilha.pdf: 4586367 bytes, checksum: c39a78169180c1ccedbe3f393fccbaee (MD5) Previous issue date: 2016-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho descreve a preparação, caracterização e aplicação eletroanalítica de um metalosilsesquioxano ligado em uma sílica mesoporosa (MCM-41) e em uma zeólita (H-FAU-Si/Al 40) com hexacianoferrato de níquel adsorvido em sua superfície. Algumas técnicas espectroscópicas como: Espectroscopia no infravermelho por transformada de Fourier (FTIR), Microscopia eletrônica de varredura (MEV), Espectroscopia por Energia Dispersiva de Raios X (EDS) e Voltametria cíclica, foram utilizadas na caracterização dos materiais formados. Os espectros na região do Infravermelho para o MTTiPNiH e ZTTiPNiH apresentaram as bandas de seus precursores (TTiP, MCM-41 e H-FAU-Si/Al 40), apenas duas absorções diferiram dos demais espectros, uma em, aproximadamente, 2168 cm-1 e outra a 2098 cm-1, tais resultados foram atribuídos ao estiramento ν (C≡N). Para o MTTIPNiH, através das micrografias pode-se observar partículas com tamanhos variados, entre 0,30 µm a 0,60 µm. Para o ZTTiPNiH as micrografias apresentaram um pequeno aumento no tamanho de partículas, aproximadamente de 50 nm, quando comparado a seus precursores. O EDS determinou a composição química semi-quantitativa dos elementos carbono, oxigênio, silício, titânio, fósforo, níquel e ferro, presentes em ambas as amostras. O eletrodo de pasta de grafite exibiu um par redox bem definido com potencial de médio padrão (E°’) de +0,53 V e +0,51 V para o MTTiPNiH e ZTTiPNiH, respectivamente, atribuído ao processo redox FeII(CN)6 / FeIII(CN)6 em presença de níquel. O eletrodo de pasta de grafite modificado com MTTiPNiH apresentou atividade eletrocatalítica para dipirona e para o sulfito, já o eletrodo de pasta de grafite modificado com ZTTiPNiH apresentou atividade eletrocatalítica apenas para o sulfito. Em uma segunda etapa, prepararam-se eletrodos impressos via screen-printed para detecção e quantificação de pindolol utilizando a técnica de voltametria de onda quadrada em uma faixa de concentração de 0,10 µmol L-1 – 10,0 µmol L-1. Após a detecção de pindolol, o protocolo de detecção foi utilizado na avaliação e recuperação desta substância a partir de urina humana. Eletrodos impressos via screen-printed foram empregados pela primeira vez na detecção da substância psicoativa Synthacaine. A detecção eletroquímica indireta para MPA/2-AI simultaneamente, utilizando eletrodos impressos apresentou resultados satisfatórios. Após a detecção simultânea de MPA e 2-AI, amostras reais de Synthacaine foram utilizadas para quantificar, através de técnicas eletroquímicas, estes analitos por meio do protocolo de detecção anteriormente proposto. / This research describes the preparation, characterization and electroanalytical application of a metalosilsesquioxane bonded in mesoporous silica (MCM-41) and in zeolite (H-FAU-Si/Al 40) with nickel hexacyanoferrate adsorbed on their surface. Techniques as fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and cyclic voltammetry were used in the characterization of the synthesized materials. The spectra in the infrared region for MTTiPNiH and ZTTiPNiH showed the bands of their precursors (TTiP, MCM-41 and H-FAU Si/Al 40), only two absorption differed from the others spectra, one at, approximately, 2168 cm-1 and another at 2098 cm-1 , which were attributed to stretching ν(C≡N). For MTTIPNiH through the micrographs can be observed particles with varied sizes between 0.30 µM to 0.60 µm. For ZTTiPNiH the micrographs showed a small increase in particle size, approximately, 50 nm, as compared to their precursors. EDS determined the semi-quantitative chemical composition of carbon, oxygen, silicon, titanium, phosphorus, nickel and iron present in both samples. The carbon paste electrode exhibited a well-defined redox couple with E°' = +0.53 V and +0.51 V for MTTiPNiH and ZTTiPNiH, respectively, attributed to the redox process FeII(CN)6 / FeIII(CN)6 in presence of nickel. Carbon paste electrode modified with MTTiPNiH showed electrocatalytic activity to dipyrone and sulfite. However the carbon paste electrode modified with ZTTiPNiH showed electrocatalytic activity only for sulfite. In a second step, screenprinted electrodes were produced for the detection and quantification of pindolol using square wave voltammetry technique at a concentration range of 0.10 µmol L-1 to 10.0 µmol L-1 . After pindolol detection, the protocol of detection was used in the evaluation and recovery of pindolol from human urine. Screen-printed electrodes were used for the first time in the detection of psychoactive substance Synthacaine. Indirect electrochemical detection for MPA/2-AI simultaneously, using Screen-printed electrodes showed satisfactory results. After the simultaneous detection of MPA and 2-AI, real samples of Synthacaine were used to quantify through electrochemical techniques, these analytes by protocol of detection previously proposed.
9

Biossegurança no controle da infecção hospitalar: desenvolvimento de imunossensor impedimétrico para detecção de Staphylococcus aureus em áreas críticas hospitalares / Biosafety in the control of hospital infection: development of an impedimetric immunosensor for detection of Staphylococcus aureus in critical areas of hospitals

Fialho, Ana Cristina Vasconcelos 21 October 2011 (has links)
Made available in DSpace on 2016-06-02T19:02:40Z (GMT). No. of bitstreams: 1 3890.pdf: 2739392 bytes, checksum: fdb93cb69cafb89992f3e6a155deacfb (MD5) Previous issue date: 2011-10-21 / The Biosafety is a very important tool for the Control of Hospital Infection establishing through methods, techniques and standards, measures to be adopted in order to prevent and control risks that may contribute to hospital infection. This work reports the development of an impedimetric immunosensor for detection of pathogenic bacteria, specifically Staphylococcus aureus (S. aureus), in hospital critical areas (Surgical Centers and Intensive Care Units) to contribute to the hospital infection control. Different parameters were studied: direct immobilization of protein A of S. aureus on the surface of the transducer or the working electrode (screen-printed electrode - SPE), immobilization of protein A on SPEs modified with self-assembled monolayers (SAMs) of cystamine (CYS) and glutaraldehyde (GA); different incubation times and dilutions were used for both modifiers as for protein A and anti- S. aureus antibodies; blocking with bovine serum albumin (BSA) and immunoassay (antigen-antibody reaction, Ag-Ab). Electrochemical techniques (electrochemical impedance spectroscopy - EIS and cyclic voltammetry - CV) and non electrochemical (microscopy) were used for the characterization and construction of the immunosensor. The impedance measurements and cyclic voltammetry showed the good results with self-assembled monolayer of cystamine 2 x 10-2 mol L-1 and glutaraldehyde 2,5% with incubation periods of 2 and 1h, respectively; immobilization of protein A 1:20 (tincub = 12 h) and anti-S. aureus monoclonal Ab (tincub = 3 h) and step blocking with 0.5% BSA (tincub = 1 h). For the Ag-Ab interaction S. aureus ATCC - 6535 strains (analyte) were used and incubation for 30 min. The immunosensor developed has proven to be an effective method for monitoring of S. aureus in a hospital environment and that can be applied as an indicative tool of the effectiveness of the standards and procedures applied to the control of hospital infection. / A Biossegurança constitui uma ferramenta de grande relevância para o Controle da Infecção Hospitalar estabelecendo através de métodos, técnicas e normas, condutas a serem adotadas com o intuito de prevenir e controlar os riscos que podem favorecer à infecção hospitalar. Este trabalho relata o desenvolvimento de um imunossensor impedimétrico para detecção de Staphylococcus aureus (S. aureus), em áreas críticas hospitalares (Centros Cirúrgicos e Unidades de Terapia Intensiva) visando contribuir para o controle de infecção hospitalar. Diferentes parâmetros foram estudados: imobilização direta da proteína A de S. aureus na superfície do transdutor ou eletrodo de trabalho (screen-printed electrode - SPE); imobilização da proteína A sobre SPEs modificados com monocamadas auto-organizadas (SAMs) de cistamina (CYS) e glutaraldeído (GA); diferentes tempos de incubação e diluições foram utilizados tanto para os modificadores como para a proteína A e anticorpos anti-S. aureus; bloqueio com soroalbumina bovina (SAB) e imunoensaio (reação antígeno-anticorpo, Ag-Ac). Técnicas eletroquímicas (espectroscopia de impedância eletroquímica - EIS e voltametria cíclica - VC) e não eletroquímicas (microscopias) foram utilizadas para a caracterização e construção do imunossensor. As medidas de impedância e voltametria cíclica mostraram bons resultados com monocamadas auto-organizadas de cistamina 2 x 10-2 mol L-1 e glutaraldeído 2,5% com tempos de incubação de 2 e 1 h, respectivamente;assim como as imobilizações da proteína A 1:20 (tincub = 12 h); Ac monoclonais anti-S. aureus (tincub = 3 h) e etapa de bloqueio com SAB 0,5% (tincub = 1 h). Na interação Ag-Ac utilizou-se cepas de S. aureus ATCC - 6535 (analito) e incubação de 30 min. O imunossensor desenvolvido indicou ser um método efetivo para monitoramento de S. aureus em ambiente hospitalar e que pode ser aplicado como instrumento indicativo da efetividade das normas e condutas aplicadas para o controle de infecção hospitalar.
10

Detecção e quantificação eletroquímica de substâncias de interesse clínico, ambiental e forense utilizando eletrodo de pasta de grafite modificado com trisilanol poss ligado a suportes porosos e eletrodos impressos obtidos via screen-printed /

Cumba, Loanda Raquel January 2016 (has links)
Orientador: Devaney Ribeiro do Carmo / Resumo: O presente trabalho descreve a preparação, caracterização e aplicação eletroanalítica de um metalosilsesquioxano ligado em uma sílica mesoporosa (MCM-41) e em uma zeólita (H-FAU-Si/Al 40) com hexacianoferrato de níquel adsorvido em sua superfície. Algumas técnicas espectroscópicas como: Espectroscopia no infravermelho por transformada de Fourier (FTIR), Microscopia eletrônica de varredura (MEV), Espectroscopia por Energia Dispersiva de Raios X (EDS) e Voltametria cíclica, foram utilizadas na caracterização dos materiais formados. Os espectros na região do Infravermelho para o MTTiPNiH e ZTTiPNiH apresentaram as bandas de seus precursores (TTiP, MCM-41 e H-FAU-Si/Al 40), apenas duas absorções diferiram dos demais espectros, uma em, aproximadamente, 2168 cm-1 e outra a 2098 cm-1, tais resultados foram atribuídos ao estiramento ν (C≡N). Para o MTTIPNiH, através das micrografias pode-se observar partículas com tamanhos variados, entre 0,30 µm a 0,60 µm. Para o ZTTiPNiH as micrografias apresentaram um pequeno aumento no tamanho de partículas, aproximadamente de 50 nm, quando comparado a seus precursores. O EDS determinou a composição química semi-quantitativa dos elementos carbono, oxigênio, silício, titânio, fósforo, níquel e ferro, presentes em ambas as amostras. O eletrodo de pasta de grafite exibiu um par redox bem definido com potencial de médio padrão (E°’) de +0,53 V e +0,51 V para o MTTiPNiH e ZTTiPNiH, respectivamente, atribuído ao processo redox FeII(CN)6 / FeIII(CN)6 em... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This research describes the preparation, characterization and electroanalytical application of a metalosilsesquioxane bonded in mesoporous silica (MCM-41) and in zeolite (H-FAU-Si/Al 40) with nickel hexacyanoferrate adsorbed on their surface. Techniques as fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and cyclic voltammetry were used in the characterization of the synthesized materials. The spectra in the infrared region for MTTiPNiH and ZTTiPNiH showed the bands of their precursors (TTiP, MCM-41 and H-FAU Si/Al 40), only two absorption differed from the others spectra, one at, approximately, 2168 cm-1 and another at 2098 cm-1 , which were attributed to stretching ν(C≡N). For MTTIPNiH through the micrographs can be observed particles with varied sizes between 0.30 µM to 0.60 µm. For ZTTiPNiH the micrographs showed a small increase in particle size, approximately, 50 nm, as compared to their precursors. EDS determined the semi-quantitative chemical composition of carbon, oxygen, silicon, titanium, phosphorus, nickel and iron present in both samples. The carbon paste electrode exhibited a well-defined redox couple with E°' = +0.53 V and +0.51 V for MTTiPNiH and ZTTiPNiH, respectively, attributed to the redox process FeII(CN)6 / FeIII(CN)6 in presence of nickel. Carbon paste electrode modified with MTTiPNiH showed electrocatalytic activity to dipyrone and sulfite. However the carbon paste electrode... (Complete abstract click electronic access below) / Doutor

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