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No description available.

No description available.

tert-butyl 1-methoxycarbonyl-1-ferrocenecarbamate, Boc-NH-Fc-COOMe, (1) was synthesized according to the literature procedure and modified to 1-amino-n′-ferrocenemethylcarboxylate, 1,n′-H2N-Fc-COOCH3 (2) by removing the Boc-group with TFA/Et3N mixture in dichloromethane. Compound 2 reacted with alkylating agents like MeI, EtI, EtSCH2CH2Cl (MA) and (CN)(EtO)2P(O) (NA) to form MeNH-Fc-COOMe (3), EtNH-Fc-COOMe (4), EtSCH2CH2NH-Fc-COOMe (5), (EtO)2P(O)NH-Fc-COOMe (6), respectively. Cyclic voltammetry (CV) of these compounds showed different half-wave potential characteristics compared to aminoferrocene and was dependent on the nature of the substituents, which was rationalized by molecular orbital calculations. Electron donating groups (Me, Et and 2-chloroethyl ethylsulfide, MA) shifted the half-wave potential towards the cathodic direction while electron withdrawing group like diethyl cyanophosphonate, NA, shifted it toward anodic direction. Anodic to cathodic peak separation were found to be within 62-88 mV indicating a quasi-reversible system. <p>Hydrolysis of compound 1 resulted in the formation of tert-butyl 1-methoxycarbonyl-1-ferrocenecarboxylic acid, Boc-NH-Fc-COOH, (11) which was coupled with cystamine using the EDC/HOBt protocol to synthesize the cystamine conjugate [BocHN-Fc-CO-CSA]2 (12). This molecule is equipped with an amino group that directly linked to the redox receptor. Compound 12 was fully characterized by spectroscopic methods and by single crystal x-ray diffraction. The cystamine conjugate 12 formed films on gold substrates, which upon deprotection of the amino group, reacted with chemical warfare agents (CWAs) mimics, such as EtSCH2CH2Cl (MA), a simulant for the sulfur mustard HD, and (CN)(EtO)2P(O) (NA), a simulant for the nerve agent Tabun. Their reaction with the surface-bound ferrocene derivative results in the formation of N-substituted products. <p>CV measurements showed anodic shifts of the Fc redox potentials by 50 (±5) mV after exposure to MA, and NA. Measurements by quartz crystal microbalance (QCM) showed an increase in mass upon exposure to MA and NA. Ellipsometry measured a film thickness increase from 6 (±1) Å for the deprotected film to 10 (±4) Å for the film modified with MA and to 7 (±2) Å for the film modified with NA. The surfaces were analyzed by x-ray photoelectron spectroscopy (XPS) and clearly showed the attachment of the cystamine conjugate on the surface and its reaction with CWAs mimics.

tert-butyl 1-methoxycarbonyl-1-ferrocenecarbamate, Boc-NH-Fc-COOMe, (1) was synthesized according to the literature procedure and modified to 1-amino-n′-ferrocenemethylcarboxylate, 1,n′-H2N-Fc-COOCH3 (2) by removing the Boc-group with TFA/Et3N mixture in dichloromethane. Compound 2 reacted with alkylating agents like MeI, EtI, EtSCH2CH2Cl (MA) and (CN)(EtO)2P(O) (NA) to form MeNH-Fc-COOMe (3), EtNH-Fc-COOMe (4), EtSCH2CH2NH-Fc-COOMe (5), (EtO)2P(O)NH-Fc-COOMe (6), respectively. Cyclic voltammetry (CV) of these compounds showed different half-wave potential characteristics compared to aminoferrocene and was dependent on the nature of the substituents, which was rationalized by molecular orbital calculations. Electron donating groups (Me, Et and 2-chloroethyl ethylsulfide, MA) shifted the half-wave potential towards the cathodic direction while electron withdrawing group like diethyl cyanophosphonate, NA, shifted it toward anodic direction. Anodic to cathodic peak separation were found to be within 62-88 mV indicating a quasi-reversible system. <p>Hydrolysis of compound 1 resulted in the formation of tert-butyl 1-methoxycarbonyl-1-ferrocenecarboxylic acid, Boc-NH-Fc-COOH, (11) which was coupled with cystamine using the EDC/HOBt protocol to synthesize the cystamine conjugate [BocHN-Fc-CO-CSA]2 (12). This molecule is equipped with an amino group that directly linked to the redox receptor. Compound 12 was fully characterized by spectroscopic methods and by single crystal x-ray diffraction. The cystamine conjugate 12 formed films on gold substrates, which upon deprotection of the amino group, reacted with chemical warfare agents (CWAs) mimics, such as EtSCH2CH2Cl (MA), a simulant for the sulfur mustard HD, and (CN)(EtO)2P(O) (NA), a simulant for the nerve agent Tabun. Their reaction with the surface-bound ferrocene derivative results in the formation of N-substituted products. <p>CV measurements showed anodic shifts of the Fc redox potentials by 50 (±5) mV after exposure to MA, and NA. Measurements by quartz crystal microbalance (QCM) showed an increase in mass upon exposure to MA and NA. Ellipsometry measured a film thickness increase from 6 (±1) Å for the deprotected film to 10 (±4) Å for the film modified with MA and to 7 (±2) Å for the film modified with NA. The surfaces were analyzed by x-ray photoelectron spectroscopy (XPS) and clearly showed the attachment of the cystamine conjugate on the surface and its reaction with CWAs mimics.

Amperometric dectection of heparin and glucosamine in flow injection analysis

An electrochemical detection method based on long range surface plasmon waveguides is proposed and demonstrated in this integrated article thesis. This dissertation uses CYTOP gold (Au) waveguides supporting long range surface plasmon polaritons (LRSPPs) in conjunction with grating couplers as well as Au waveguides embedded on a one-dimensional photonic crystal (1DPC) supporting Bloch LRSPPs integrated grating couplers. Grating couplers for Au stripe waveguides embedded in Cytop are demonstrated and analyzed. Grating couplers are used in a broadside coupling scheme where a laser beam incident on a stripe of Au on Cytop. The use of gratings for excitation of LRSPPs simplifies optical alignment and does not require high-quality input and output edge facets. Over a broad operating wavelength range, optical experiments are performed to demonstrate coupling loss and determine the efficiency of grating coupling using both a cleaved bow-tie PM fiber and a lensed PM fiber. The coupling loss and grating coupling efficiency of both types of fibers are also calculated numerically. Fluoropolymers with refractive indices close to water, such as CYTOP, are widely used to make waveguide biosensors today. Due to its low glass transition temperature, CYTOP presents limitations to fabrication processes. A truncated 1D photonic crystal may replace a low-index polymer cladding such as CYTOP to support Bloch LRSPPs within the bandgap of the 1DPC over limited wavenumbers and wavelength range. As a result of the high sensitivity of Au stripe Bloch LRSPP waveguide biosensors and their compatibility with high levels of integration, microelectrode systems that can be integrated with such optical biosensors are examined. A chip bearing a Au LRSPP waveguide that can also function as a working electrode (WE), a Pt counter electrode (CE), and Pt/Cu electrical contact pads, is used to demonstrate the electrochemical performance of LRSPPs waveguides. The cyclic voltammetry measurements were performed at different scan rates and concentrations of potassium ferricyanide as the redox species on Au LRSPPs waveguides. By fitting our experimental data to the Randles-Sevcik equation, we find the diffusion coefficient of potassium ferricyanide. The results from CV measurements obtained from chips are compared with commercial macroscopic electrodes. The CV measurements are also compared with theoretical results computed using the Butler-Volmer equation to determine the rate constant of the redox species at zero potential. A waveguide containing a stripe of Au that propagates infrared surface plasmon polaritons (SPPs), acting simultaneously as an electrode in a three-electrode electrochemical cell is also examined. Under SPP excitation, cyclic voltammetry was measured as a function of incident optical power and wavelength (1350 nm). In oxidation and reduction reactions, energetic electrons are separated from energetic holes. Under SPP excitation, redox current densities increase by 10×. With the SPP power, the oxidation, reduction, and equilibrium potentials drop by as much as 2× and separate in correlation with the photon energy. According to electrochemical impedance spectroscopy, charge transfer resistance dropped by almost 2× under SPP excitation. During SPP excitation, the temperature of the working electrode is monitored in situ and independent control experiments are performed to isolate thermal effects. Measurements of chronoamperometry with SPPs modulated at 600 Hz yield a rapid current response modulated at the same frequency, ruling out thermally enhanced mass transport. The observation is attributed to the opening of optically controlled non-equilibrium redox channels associated with the energetic carrier transfer to the redox species. During CV and chronoamperometry measurements, convolutional voltammetry is performed by monitoring the SPP output power versus the applied voltage. Using both experimental and theoretical methods, we demonstrate that the SPP output power is proportional to the electrochemical current convolution. A SPP voltammogram confirms that signal changes are mainly caused by differences in refractive index between reduced and oxidized forms of redox species. In addition, we demonstrate that energetic carriers resulted from SPP absorption significantly improved electrochemical sensitivity. As a complementary electrochemical technique, convolutional voltammetry is useful since the signal is related directly to the concentration of electroactive species on the working electrode (WE) and independent of the scan rate. As a probe of electrochemistry taking place in waveguides, surface plasmon polaritons (SPPs) propagating along one are sensitive. In such a waveguide, the optical output power is proportional to the time convolution of the electrochemical current density, eliminating the need to calculate the latter a posteriori via numerical integration. It is demonstrated that a waveguide WE provide an optical response that can be experimentally validated by chronoamperometry and cyclic voltammetry measurements under SPP excitation for a few potassium ferricyanide (redox species) concentrations in potassium nitrate (electrolyte) and various scan rates. Cyclic voltammetry measurements taken under increasing SPP power produce a regime where SPPs no longer act solely as the probe, but also act as a pump, producing energetic electrons and holes via their absorption in the WE. The energetic carriers enhance (10×) redox current densities as well as the convolution signal measured directly as the optical output power over time.

To address the challenge of accurate, low cost and robust biosensors for diabetes management and early detection of diabetes complications, we have developed novel, robust sensing chemistry (or receptors) for electrochemical POC biosensors. The biosensors have been developed for the bio-markers associated with diabetes management such as glycated haemoglobin (HbA1c), glycated albumin, glucose, biomarkers associated with diabetes complications such as microalbuminuria, urine creatinine and albumin-to-creatinine ratio (ACR) and biomarkers associated with anaemia and malnutrition conditions such as haemoglobin and serum albumin. For haemoglobin detection, a new POC bio sensing technique has been developed based on Aza-heterocyclic chemicals. The repeatability and accuracy of the biosensor have been tested on real pathology samples. The glycated form of haemoglobin, called glycated haemoglobin or HbA1c, is the gold standard test in diabetes management as it gives the 90-days average blood glucose value. We demonstrate a simple method for electrochemical detection of HbA1c by combining bosonic affinity principle along with aza-heterocyclic receptors. The technique has been verified on the real clinical patient samples. Albumin is the most abundant protein in the human blood. Human serum albumin (HSA) is either alone or an associative biomarker in several chronic diseases like necrosis, nephrosis, hepatitis, malnutrition, arthritis, immune disorders, cancer, diabetes and in some severe infections. In pathology laboratories, the serum albumin is usually tested on serum samples and not in whole blood samples. Since albumin is not a metalloproteinase, it is very difficult to develop electrochemical POC biosensor. We have developed a novel technique for the electrochemical detection of serum albumin in whole blood samples, by exploiting its binding property with redox active copper salts. The accuracy of technique has been verified on both real human blood plasma as well as whole blood samples. Glycated albumin, which is the glycated form of serum albumin, is emerging as a novel biomarker for diabetes management, as it gives the average blood glucose value of 15-20 days. It is also extremely useful in chronic kidney disease patients and patients with hemoglobinopathies where HbA1c can give the erroneous results. By combining the copper chemistry along with bosonic affinity principle, we present the first ever demonstration of glycated albumin sensing. Instant blood glucose monitoring is an integral part of diabetes management. Most of the glucometers available in the market are based on glucose oxidase enzyme. We have demonstrated a low cost non-enzymatic electrochemical technique for blood glucose detection using alkaline methylene blue chemistry. The accuracy of the technique has been verified on real human blood plasma samples. Glucometer is one of the most easily available POC biosensor and a useful tool for diabetes population. India has second largest diabetes population in the world. To analyse the accuracy of the POC glucometers which are available in Indian market, a comprehensive study was conducted. The results were compared with clinical accuracy guidelines using exhaustive statistical analysis techniques. The shortcomings of the commercial glucometers are elucidated, regarding different international standards. Diabetic nephropathy is one of the major diabetes complications and is the primary cause of chronic kidney disease (CKD). The presence of albumin in urine is a well-established biomarker for the early detection of diabetic nephropathy. We have developed a technique for electrochemical detection of microalbuminuria for point of care applications by exploring the binding property of human albumin with electrochemically active molecules like copper and hemin. Methylene blue mediated sensing technique has also been proposed. Urine Albumin-to creatinine ratio (ACR) is another variant of the microalbumuria test that can be done any time and does not suffer from the dilution factor of urine. Iron binding property of creatinine is exploited to develop creatinine biosensor, thus enabling POC ACR tests.

Este trabalho descreve a construção e avaliação de um detector condutométrico sem contato (oscilométrico) para sua aplicação em eletroforese capilar de zona e cromatografia micelar eletrocinética (MEKC). A construção do detector contou com a avaliação de diversos materiais e métodos para a confecção dos eletrodos, tão bem como o aperfeiçoamento do seu circuito eletrônico. O seu comportamento e desempenho foram verificados através do estudo dos diversos parâmetros que influenciam sua resposta, como freqüência e amplitude do sinal aplicado, temperatura e condutividade do meio. Além disso, a simulação do circuito equivalente da cela de detecção auxiliou no entendimento das propriedades do detector frente a alterações na condutividade do meio, na freqüência de operação e nas dimensões da cela. A otimização dos parâmetros operacionais foi racionalizada pela formulação de equações analíticas que descrevem o fator de resposta do detector a partir de parâmetros obtidos experimentalmente. Para o desenvolvimento do sistema de detecção, dois equipamentos completos de eletroforese capilar foram construídos. Sistemas de injeção de amostra por pressão, por gravidade, e eletrocinética foram desenvolvidos. Um dos equipamentos permite que a injeção da amostra seja feita do lado aterrado da fonte de alta tensão. Conseqüentemente, o detector é posicionado próximo do ponto de aplicação da alta tensão. Este é, de que se tem notícia, o primeiro sistema de detecção eletroquímico para eletroforese capilar com essa característica. A termostatização dos capilares foi efetuada por convecção forçada de ar. De maneira a aumentar o grau de automação e facilitar o seu manuseio, os dois equipamentos foram interfaceados a microcomputador. Os equipamentos de eletroforese com detecção oscilométrica construídos permitiram a análise de diversas substâncias em matrizes variadas, como por exemplo íons orgânicos e inorgânicos em água de chuva e material particulado, ácidos graxos de cadeia linear em gordura de coco, formaldeído na fase gasosa da atmosfera, e, pela primeira vez, espécies neutras, como álcoois alifáticos, separadas por MEKC. / This work describes the construction and evaluation of a contactless conductometric (or oscillometric) detector, for its application in capillary zone electrophoresis and micellar electrokinetic chromatography (MEKC). The materials and methods used for the construction of the electrodes, as well as the improvements on the electronic circuit, were evaluated. The behavior and performance of the detector were studied by changing the parameters that affect its response, e. g., the frequency and amplitude of the input signal, temperature and solution conductivity. The simulation of the cell equivalent electric circuit helped to understand the detector properties related to the variations in the solution conductivity, frequency, and cell dimensions. The optimization of the parameters was conducted by the formulation of analytical equations that describe the response factor using experimental data. For the detection development, two complete capillary electrophoresis equipments were constructed. Pressure, gravity, and electrokinetic sample injection systems were developed. One of the equipments allows the sample injection on the grounded side of the capillary. Consequently, the detector is placed near the high voltage application point. This is the first electrochemical detector described for capillary electrophoresis with this characteristic. The capillary thermostating was made by passing a forced air stream. Both equipments were interfaced to microcomputers. The capillary electrophoresis equipments with oscillometric detection were applied to the analysis of many types of compounds in different matrices, such as organic and inorganic ions in rainwater and particulate material, fatty acids in cocoa oil, formaldehyde in the atmosphere and, for the first time, neutral species, like aliphatic alcohols, separated by MEKC.

Este trabalho descreve o desenvolvimento de microchips para eletroforese a partir dos processos de impressão direta e fotolitográfico. A estrutura dos microcanais fabricados pelo processo de impressão direta são definidos por filmes de poliéster (base e tampa) e por uma camada de toner (paredes). A caracterização da superfície e da composição do toner foram necessárias para um melhor entendimento da composição química da estrutura dos microcanais e para este propósito foram utilizadas diferentes técnicas como análise elementar de CHN-O, AFM, EDX e MEV. Além da química do toner as dimensões limites para os canais, como largura e altura, também foram estudadas. A aplicação de um efeito de cinza nos microcanais foi avaliado de modo a desenvolver um dispositivo de pré-concentração usando as partículas de toner como obstáculos para o fluxo. Os microdispositivos fabricados em poliéster-toner foram integrados com detecção amperométrica no final do canal de separação usando eletrodos produzidos a partir da combinação das tecnologias da produção de máscaras de toner e CDs, como fonte de ouro. O desempenho destes microchips foi avaliado com detecção amperométrica da separação eletroforética de iodeto e ascorbato. Os limites de detecção obtidos foram de 500 nmol L-1 (135 amol) e 1,2 mmol L-1 (486 amol) para o iodeto e ascorbato, respectivamente. Além do processo de impressão direta, o processo fotolitográfico também foi utilizado para a mesma finalidade. Neste processo foi utilizado o fotorresiste negativo SU-8 e microdispositivos com área de 1 cm2 foram fabricados usando diferentes substratos como vidro, silício e alumina. A alumina apresentou muitas irregularidades para os microdispositivos fabricados. Problemas com a absorção e dispersão da radiação ultravioleta foram observados. No entanto, a alumina foi um excelente material para as etapas de produção de dois moldes metálicos para a rápida produção de dispositivos poliméricos. Um molde com uma geometria complexa foi obtido para estudar um novo sistema de injeção e um segundo molde foi preparado para avaliar o uso de uma borracha de silicone como material moldante. Além disso, este trabalho também apresenta o desenvolvimento de um dispositivo microfabricado com eletrodos completamente integrados para separação e detecção eletroquímica. Eletrodos de ouro ou de titânio/platina foram obtidos através da técnica lift-off. As máscaras para a fabricação de moldes metálicos e dos dispositivos integrados foram preparadas em fotolito de alta resolução. / This work describes the development of electrophoresis microchip fabricated by direct-printing and photolithographic processes. The channel structures of the devices fabricated by direct-printing process are defined by polyester films (base and cover) and by a toner layer (walls). The characterization of toner surface and composition were necessary for a better understanding of the chemistry composition and for this purpose we have used different techniques such as CHN-O elemental analysis, AFM, EDX and SEM. Besides the chemistry of toner, the possible dimensions for the channels as the depth and the width were also studied. The application of a gray-scale effect in the channels was evaluated in order to create a preconcentration device using the toner particles as obstacles for the flow. The polyester-toner microdevices were coupled with end-channel amperometric detection using electrodes produced by combination of the toner masks laser-printing and compact discs as a gold source. The performance of this electrophoresis microchip was evaluated by amperometric detection of iodide and ascorbate. The detection limits found were 500 nmol L-1 (135 amol) and 1.2 mmol L-1 (486 amol) for iodide and ascorbate, respectively. Besides the direct-printing process, the photolithographic process was also used for this purpose. In this process it was used the SU-8 negative photoresist and microdevices with 1-cm2 area were fabricated using different substrates such as glass, silicon and alumina. The alumina presented several irregularities for the microdevices fabricated. Problems with the absorption and dispersion of ultraviolet radiation were observed. However, the alumina was an excellent material for the steps in the production of two metallic molds for fast production of PDMS devices. One mold with complex geometry was obtained in order to study a new injection system and a second mold was prepared to evaluate the use of silicon rubber as molding material. Furthermore, in this work it was also reported the development of a microfabricated device with fully integrated electrodes for separation and electrochemical detection. The gold or titanium/platinum electrodes were obtained by lift-off technique. The masks for fabrication of the metallic molds and of the integrated microdevices were prepared in transparency films with high resolution.