ISEP – BioMark – Pósteres apresentados a eventos científicos
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Browsing ISEP – BioMark – Pósteres apresentados a eventos científicos by Author "Ferreira, Nádia S."
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- Carnitine tailored Sensors on Surface Molecular Imprinting based on Graphene layersPublication . Truta, Liliana A.A.N.A.; Ferreira, Nádia S.; Sales, M. Goreti F.A new biosensor based on surface molecularly imprinted polymer (MIP) on graphene layers was successfully developed. It consists in a 3D polymeric network created on top of surface and around the target template, Carnitine (CRT), a potential biomarker of ovary cancer. The polymeric structure was obtained after radical polymerization of (vinylbenzyl)trimethylammonium chloride, 4-styrenesulfonic acid and vinyl pivalate, including in the reaction mixture ethylene glycol dimethacrylate as cross-linker and ammonium persulphate as initiator. Non-imprinted polymer (NIP) material was also produced, by excluding the template from the procedure. The imprinted graphene structures were further used for the selective determination of CRT by potentiometric transduction. For this purpose, a selective membrane was prepared by using the MIP material as ionophore, and dispersing it in a plasticized poly(vinylchloride) matrix, that included (or not) a suitable amount of charged lipophilic additive. The membranes were casted over a solid conductive support, made of graphite or of conductive glass. Control membranes were also produced by replacing MIP by NIP material. The potentiometric performance of the above electrodes was assessed against CRT solutions of increasing concentrations. Graphite supports displayed the best analytical features, with average slope and detection limit of 40.51 mVdecade-1 and 3.55x10-6 molL-1, respectively. The effect of pH upon the potentiometric response was evaluated for different buffer solutions (within 2-9) and the best performance for this sensor was obtained with HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer of pH 5.2. The interference effect of albumin, ascorbic acid, glucose, creatinine and urea in the performance of the electrochemical unit was tested for concentrations up to their normal physiologic levels in urine and good selectivity was observed. The application of the devices to the analysis of spiked samples showed recoveries ranging from 91% (± 6.8%) to 118% (± 11.2%), with relative errors below -20%. Overall, the combination of the MIP sensory material with a suitable selective membrane and electrode design showed to be a promising tool for point-of-care applications.
- Disposable immunosensor with simple antibody orientation for label-free real-time detection of a cancer biomarkerPublication . Ferreira, Nádia S.; Sales, M. Goreti F.This work proposes a novel approach for a suitable orientation of antibodies (Ab) on an immunosensing platform, applied here to the determination of 8-hydroxy-2’-deoxyguanosine (8OHdG), a biomarker of oxidative stress that has been associated to chronic diseases, such as cancer. The Anti-8OHdG was bound to an amine modified gold support through its Fc region after activation of its carboxylic functions. Non-oriented approaches of Ab binding to the platform were tested in parallel, in order to show that the presented proposal favored Ab/Ag affinity. The immunosensor design was evaluated by Quartz-Crystal microbalance with Dissipation, Atomic Force Microscopy, Electrochemical Impedance Spectroscopy (EIS) and Square-Wave Voltammetry. EIS was also a suitable technique to follow the analytical behavior of the device against 8OHdG. The affinity binding between 8OHdG and the antibody immobilized in the gold modified platform increased the charged transfer resistance across the electrochemical sep-up. The observed behavior was linear from 0.02 to 7.0 ng/mL of 8OHdG concentrations. The interference from Glucose, Urea and Creatinine was found negligible. An attempt of application to synthetic samples was also successfully conducted. Overall, the presented approach enabled the production of suitably oriented Abs over a gold platform by means of a much simpler process than other oriented-Ab binding approaches described in the literature, as far as we know, and was successful in terms of analytical features and sample application.
- Host-Tailored Sensors for Carnitine Potentiometric Measurements based on Surface Molecular ImprintingPublication . Truta, Liliana A.A.N.A.; Ferreira, Nádia S.; Sales, M. Goreti F.A novel surface molecularly imprinted polymer (MIP) is presented for Carnitine (CRT), a potential biomarker of ovary cancer. It consists in a 3D polymeric network created on top of graphene layers and around the target template. The polymeric structure was obtained after radical polymerization of (vinylbenzyl)trimethylammonium chloride, 4-styrenesulfonic acid and vinyl pivalate, including in the reaction mixture ethylene glycol dimethacrylate as cross-linker and ammonium persulphate as initiator. Non-imprinted polymer (NIP) material was also produced, by excluding the template from the procedure. The imprinted material was further used for the selective determination of CRT by potentiometric transduction. A selective membrane was prepared for this purpose by using the MIP material as ionophore, and dispersing it in a plasticized poly(vinylchloride) matrix with a suitable charged lipophilic additive. All membranes were casted over a solid conductive support made of graphite and applied over the smaller end of an insulin syringe. The best membranes were also applied over conductive glass/plastic. Control membranes were also produced by replacing MIP by NIP material. The potentiometric performance of the above electrodes was evaluated against CRT solutions of increasing concentrations. Overall, the best devices displayed linear response with average slope and detection limit of 47.28 mV.decade-1 and 3.55x10-6 mol.L-1, respectively. The effect of pH upon the potentiometric response was evaluated for different buffer solutions (within 2-9) and the best performance for this sensor was obtained with HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer of pH 5.2. Good selectivity was observed against albumin, ascorbic acid, glucose, creatinine and urea, tested for concentrations up to their normal physiologic levels in urine. The application of the devices to the analysis of spiked samples showed recoveries ranging from 91% (± 6.8%) to 118% (± 11.2%), with relative errors below -20%. Overall, the combination of the MIP sensory material with a suitable selective membrane and electrode design has lead to a promising tool for point-of-care applications, when applied to field monitoring of CRT in biological samples.
- A new biomimetic sensor for detecting carnitine, a potential biomarker in ovarian cancerPublication . Tavares, Ana P. M.; Ferreira, Nádia S.; Truta, Liliana A.A.N.A.; Sales, M. Goreti F.Carnitine (CRT) displays an important role in cellular metabolism and energy production. It has actions that include the metabolites associated with glycolysis and β-oxidation of fatty acids. The change of its levels in biological fluids has been associated to the presence of ovarian cancer, making CRT a potential biomarker of the disease. Sensitive CRT determination (in low levels) becomes therefore important, for which a low cost and sensitive device would be appreciated. A biomimetic polymer is proposed herein for this purpose, produced by bulk electropolymerization around a hydrophobic paper substrate that was made conductive by casting a graphite-based ink. Materials and methods The electrode substrate was prepared by modifying cellulose paper, first with solid wax and after with carbon ink. The hydrophobicity of the paper was tested by contact angle and the ink properties evaluated by Thermogravimetry, Raman Spectroscopy and FTIR. Two different biomimetic materials were electropolymerized over the carbon conductive support: 3,4-ethylenedioxythiophene (EDOT) and dodecilbenzenesulfonic acid sodium salt (NaDBS). The polymeric film depositions were obtained by chronoamperometry at 0.9 V vs Ag/AgCl during 240 s. The obtained sensors were characterized by Electrochemical Impedance Spectroscopy (EIS), in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer at pH 7.0.
- New modified electrochemical conductive paper support for BSA detectionPublication . Ferreira, Nádia S.; Moreira, Ana P. T.; Sales, M. Goreti F.Chemical sensors and biosensors are widely used to detect various kinds of protein target biomolecules. Molecularly Imprinted Polymers (MIPs) have raised great interest in this area, because these act as antibody-like recognition materials, with high affinity to the template molecule. Compared to natural antibodies, these are also of lower cost and higher stability. There are different types of supports used to carry MIP materials, mostly of these made of gold, favourably assembled on a Screen Printed Electrode (SPE) strategy. For this work a new kind of support for the sensing layer was developed: conductive paper. This support was made by modifying first cellulose paper with paraffin wax (to make it waterproof), and casting a carbon-ink on it afterwards, to turn it conductive. The SPAM approach previously reported in1 was employed herein to assemble to MIP sensing material on the conductive paper. The selected charged monomers were (vinylbenzyl) trimethlammonium chloride (positive charge) or vinylbenzoic acid (negative charge), used to generate binding positions with single-type charge (positive or negative). The non-specific binding area of the MIP layer was assembled by chronoamperometry-assisted polymerization (at 1 V, for 60, 120 or 180 seconds) of vinylbenzoate, cross-linked with ethylene glycol vinyl ether. The BSA biomolecules lying within the polymeric matrix were removed by Proteinase K action. All preparation stages of the MIP assembly were followed by FTIR, Raman spectroscopy and, electrochemical analysis. In general, the best results were obtained for longer polymerization times and positively charged binding sites (which was consistent with a negatively-charged protein under physiological pH, as BSA). Linear responses against BSA concentration ranged from 0.005 to 100 mg/mL, in PBS buffer standard solutions. The sensor was further calibrated in standard solutions that were prepared in synthetic or real urine, and the analytical response became more sensitive and stable. Compared to the literature, the detection capability of the developed device is better than most of the reported electrodes. Overall, the simplicity, low cost and good analytical performance of the BSA SPE device, prepared with positively charged binding positions, seems a suitable approach for practical application in clinical context. Further studies with real samples are required, as well as gathering with electronic-supporting devices to allow on-site readings.