Recycling old screen-printed electrodes with newly designed plastic antibodies on the wall of carbon nanotubes as sensory element for in situ detection of bacterial toxins in water

Using low cost portable devices that enable a single analytical step for screening environmental contaminants is today a demanding issue. This concept is here tried out by recycling screen-printed electrodes that were to be disposed of and by choosing as sensory element a low cost material offering specific response for an environmental contaminant. Microcystins (MCs) were used as target analyte, for being dangerous toxins produced by cyanobacteria released into water bodies. The sensory element was a plastic antibody designed by surface imprinting with carefully selected monomers to ensure a specific response. These were designed on the wall of carbon nanotubes, taking advantage of their exceptional electrical properties. The stereochemical ability of the sensory material to detect MCs was checked by preparing blank materials where the imprinting stage was made without the template molecule. The novel sensory material for MCs was introduced in a polymeric matrix and evaluated against potentiometric measurements. Nernstian response was observed from 7.24 × 10−10 to 1.28 × 10−9 M in buffer solution (10 mM HEPES, 150 mM NaCl, pH 6.6), with average slopes of −62 mVdecade−1 and detection capabilities below 1 nM. The blank materials were unable to provide a linear response against log(concentration), showing only a slight potential change towards more positive potentials with increasing concentrations (while that ofthe plastic antibodies moved to more negative values), with a maximum rate of +33 mVdecade−1. The sensors presented good selectivity towards sulphate, iron and ammonium ions, and also chloroform and tetrachloroethylene (TCE) and fast response (<20 s). This concept was successfully tested on the analysis of spiked environmental water samples. The sensors were further applied onto recycled chips, comprehending one site for the reference electrode and two sites for different selective membranes, in a biparametric approach for “in situ” analysis.

A new biomimetic sensor for detecting carnitine, a potential biomarker in ovarian cancer

1st ASPIC International Congress

A novel antibody-like material for breast cancer antigen CA15-3, used to track breast cancer by potentiometric transduction

This work presents the development of a low cost sensor device for the diagnosis of breast cancer in point-of-care, made with new synthetic biomimetic materials inside plasticized poly(vinyl chloride), PVC, membranes, for subsequent potentiometric detection. This concept was applied to target a conventional biomarker in breast cancer: Breast Cancer Antigen (CA15-3). The new biomimetic material was obtained by molecularly-imprinted technology. In this, a plastic antibody was obtained by polymerizing around the biomarker that acted as an obstacle to the growth of the polymeric matrix. The imprinted polymer was specifically synthetized by electropolymerization on an FTO conductive glass, by using cyclic voltammetry, including 40 cycles within -0.2 and 1.0 V. The reaction used for the polymerization included monomer (pyrrol, 5.0×10-3 mol/L) and protein (CA15-3, 100U/mL), all prepared in phosphate buffer saline (PBS), with a pH of 7.2 and 1% of ethylene glycol. The biomarker was removed from the imprinted sites by proteolytic action of proteinase K. The biomimetic material was employed in the construction of potentiometric sensors and tested with regard to its affinity and selectivity for binding CA15-3, by checking the analytical performance of the obtained electrodes. For this purpose, the biomimetic material was dispersed in plasticized PVC membranes, including or not a lipophilic ionic additive, and applied on a solid conductive support of graphite. The analytical behaviour was evaluated in buffer and in synthetic serum, with regard to linear range, limit of detection, repeatability, and reproducibility. This antibody-like material was tested in synthetic serum, and good results were obtained. The best devices were able to detect 5 times less CA15-3 than that required in clinical use. Selectivity assays were also performed, showing that the various serum components did not interfere with this biomarker. Overall, the potentiometric-based methods showed several advantages compared to other methods reported in the literature. The analytical process was simple, providing fast responses for a reduced amount of analyte, with low cost and feasible miniaturization. It also allowed the detection of a wide range of concentrations, diminishing the required efforts in previous sample pre-treating stages.

Carnitine tailored Sensors on Surface Molecular Imprinting based on Graphene layers

III Jornadas de Electroquímica e Inovação (Electroquímica e Nanomateriais), na Universidade de Trás-os-Montes e Alto Douro, Vila Real, 16 a 17 de Setembro de 2013

Host-Tailored Sensors for Carnitine Potentiometric Measurements based on Surface Molecular Imprinting

Graduate Student Symposium on Molecular Imprinting 2013, na Queen’s University, Belfast, United Kingdom, 15 a 17 de Agosto de 2013

A potentiometric magnetic immunoassay for rapid detection of Salmonella typhimurium

Potentiometric detection with homemade polymeric membrane microelectrodes was coupled to a magnetic sandwich immunoassay for Salmonella typhimurium determination. Cadmium and sodium ion selective electrodes were used respectively as indicator and pseudo-reference electrodes and were prepared in pipette tips to allow potentiometric measurements in microliter sample volumes. In the proposed method, the concentration of S. typhimurium was proportional to the amount of cadmium released upon dissolution of a CdS nanoparticle labeled to the secondary detection antibody. The limit of detection was 2 cells per 100 μL. The immunomagnetic assay with potentiometric detection is suitable for sensitive and rapid (average total time per assay of 75 minutes) detection of S. typhimurium in milk samples. The proposed method is easy to perform, safe, sensitive, and low cost and has potential for in situ analysis.

Desenvolvimento do processo de produção de peça plástica revestida a PVC para a indústria automóvel

O desenvolvimento do processo de produção de um produto para a indústria automóvel é sempre um desafio de nível de dificuldade exigente. Este trabalho teve por base o estudo do desenvolvimento do processo de produção de um produto para a área automóvel, constituído por diversos componentes e exigindo diversas etapas de produção. O desafio partiu de um cliente da SIMOLDES - PLÁSTICOS, S.A. que necessitava de uma peça em plástico para um novo modelo de automóvel. Foram estabelecidas as condições iniciais impostas pelo cliente e foram estudados os condicionalismos impostos pelas mesmas. Foram estudadas diferentes alternativas com vista à optimização do processo, garantindo a qualidade e tentando minimizar o custo final do produto. Foi realizada uma optimização dos moldes, por forma a poderem ser utilizadas máquinas com Força de Fecho mais baixa. Foram desenvolvidos alguns equipamentos que permitiram à empresa optar por novas formas de produção, utilizando materiais mais amigos do ambiente. Foram estudadas as condições de distribuição e optimização das tarefas, com vista à garantia do cumprimento dos prazos de entrega exigidos pelo cliente. Foi estudado o ‘layout’ que optimizou as operações de transporte das diferentes peças que constituem o produto final. Este trabalho foi elaborado com base num trabalho desenvolvido e implementado na SIMOLDES – PLÁSTICOS, S.A.

Selective synthesis under microwave irradiation of new monomers for potential applications in PDLC films

Dissertation to obtain the degree of master in Bioorganic

Valorização da Drêche Cervejeira: Fermentação de Pentoses

O presente trabalho tem como objetivo a otimização da etapa de fermentação dos açúcares obtidos a partir da drêche cervejeira para produção do bioetanol através da utilização das leveduras Pichia stipitis NCYC 1541 e Kluyveromyces marxianus NCYC 2791 como agentes fermentativos. O meio de cultura usado para manter as culturas destas leveduras foi Yeast Extract Peptone Dextrose (YEPD). O principal propósito deste trabalho foi o de encontrar alternativas aos combustíveis fósseis, pautando-se por soluções inofensivas para o meio ambiente e sustentáveis. Assim, o trabalho está dividido em quatro etapas: 1) caraterização química e biológica da drêche; 2) pré-tratamento ácido e hidrólise enzimática para primeiramente quebrar as moléculas de lenhina que envolvem os polímeros de celulose e hemicelulose e em seguida romper as ligações poliméricas destas macromoléculas por ação enzimática e transforma-las em açúcares simples, respetivamente, obtendo-se então a glucose, a maltose, a xilose e a arabinose; e, por último, 3) otimização da etapa de fermentação da glucose, maltose e das pentoses que constitui a condição essencial para se chegar à síntese do bioetanol de um modo eficiente e sustentável e 4) a recuperação do bioetanol produzido por destilação fracionada. A quantificação dos açúcares libertados no processo foi feita recorrendo a análises por cromatografia líquida de alta eficiência (HPLC). Neste estudo foram identificados e quantificados cinco açúcares: Arabinose, Glucose, Maltose, Ribose e Xilose. Na etapa de pré-tratamento e hidrólise enzimática foram usados os ácidos clorídrico (HCl) e nítrico (HNO3) com a concentração de 1% (m/m), e as enzimas Glucanex 100g e Ultraflo L. Foram testadas seis condições de pré-tratamento e hidrólise enzimática, alterando os parâmetros tempo de contacto e razão enzimas/massa de drêche, respetivamente, e mantendo a temperatura (50 ºC), velocidade de agitação (75 rpm) e concentração dos ácidos (1% (m/m)). No processamento de 25 g de drêche seca com 0,5 g de Glucanex, 0,5 mL de Ultraflo e um tempo de reação de 60 minutos para as enzimas foi obtida uma eficiência de 15%, em hidrolisado com 6% da celulose. Realizou-se a fermentação do hidrolisado resultante do pré-tratamento ácido e hidrólise enzimática de drêche cervejeira e de meios sintéticos preparados com os açúcares puros, usando as duas estirpes selecionadas para este estudo: Pichia stipitis NCYC 1541 e Kluyveromyces marxianus NYCY 2791. As eficiências de fermentação dos açúcares nos meios sintéticos foram superiores a 80% para ambas as leveduras. No entanto, as eficiências de fermentação do hidrolisado da drêche foram de 45,10% pela Pichia stipitis e de 36,58 para Kluyveromyces marxianus, para um tempo de fermentação de 72 horas e à temperatura de 30 °C. O rendimento teórico em álcool no hidrolisado da drêche é de 0,27 g/g, três vezes maior do que o real (0,0856 g/g), para Pichia stipitis e de 0,19 g/g seis vezes maior do que o real (0,0308 g/g), para a Kluyveromyces marxianus.

Edible coatings based on chitosan-beeswax emulsions

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Non-clinical isolates bring new findings on enterococcal virulence

Dissertation presented to obtain the PhD degree in Biology

Deeper insights into SRB-driven biocorrosion mechanisms

Dissertação para obtenção do Grau de Doutor em Química Sustentável

Effect of surfactant on PDLC films with and without permanent memory effect

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Porous structures for the purification of biopharmaceuticals

This work aimed at the development of a (bio)polymeric monolithic support for biopharmaceuticals purification and/or capture. For that, it was assured that functional groups on its surface were ready to be involved in a plethora of chemical reactions for incorporation of the desired and most suitable ligand. Using cryogelation as preparation method a screening on multiple combinations of materials was performed in order to create a potentially efficient support with the minimal footprint, i.e. a monolithic support with reasonable mechanical properties, highly permeable, biocompatible, ready to use, with gravitational performance and minimal unspecific interactions towards the target molecules, but also biodegradable and produced from renewable materials. For the pre-selection all monoliths were characterized physico-chemically and morphologically; one agarose-based and two chitosan-based monoliths were then subjected to further characterizations before and after their modification with magnetic nanoparticles. These three specimens were finally tested towards adenovirus and the recovery reached 84% for the chitosan-GMA plain monolith prepared at -80°C. Monoliths based on chitosan and PVA were prepared in the presence and absence of magnetic particles, and tested for the isolation of GFP directly from crude cellular extracts. The affinity ligand A4C7 previously selected for GFP purification was synthesized on the monolith. The results indicated that the solid-phase synthesis of the ligand directly onto the monolith might require optimization and that the large pores of the monoliths are unsuitable for the purification of small proteins, such as GFP.

Writing/erasing 3D micro and nano wrinkles in flexible elastomers for volatile organic compounds sensor

Micro/nano wrinkled patterns on cross-linked urethane/urea polymeric flexible free standing films with two soft segments, polypropylene oxide and polybutadiene, can be induced by UV-irradiation. The ability to write/erase these 3D structures, in a controlled manner, is the main focus of this work. The imprinting of the wrinkled structures was accomplished by swelling in an appropriate solvent followed by drying the membranes after the cross-linking process and UV irradiation. The surface tailoring of the elastomeric membranes was imaged by optical microscopy, scanning electronic microscopy and by atomic force microscopy. To erase the wrinkled structures the elastomers were swollen. The swelling as well as the sol/gel fraction and the UV radiation were tuned in order to control the wrinkles characteristics. It was found that the wrinkles wavelength, in the order of microns (1±0,25μm), was stamped by the UV radiation intensity and exposure time while the wrinkles' amplitude, in the order of nanometers (150-450 nm), was highly dependent on the swelling and sol/gel fraction. A prototype for volatile organic compounds detection was developed taking advantage of the unique 3D micro/nano wrinkles features.