Browsing by Author "Tavares, Ana P. M."
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- Conductive Paper with Antibody- Like Film for Electrical Readings of BiomoleculesPublication . Tavares, Ana P. M.; Ferreira, Nádia S.; Truta, Liliana A. A. N. A.; Sales, GoretiThis work reports a novel way of producing an inexpensive substrate support to assemble a sensing film, designed for the electrical transduction of an intended biomolecule. The support uses cellulose paper as substrate, made hydrophobic with solid wax and covered by a home-made conductive ink having graphite as core material. The hydrophobicity of the paper was confirmed by contact angle measurements and the conductive ink composition was optimized with regard to its adhesion, conductivity, and thermal stability. This support was further modified targeting its application in quantitative analysis. Carnitine (CRT) was selected as target compound, a cancer biomarker. The recognition material consisted of an antibody-like receptor film for CRT, tailored on the support and prepared by electrically-sustained polymerization of 3,4-ethylenedioxythiophene (EDOT) or dodecylbenzenesulfonic acid (DBS). Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy analysis confirmed the presence of the polymeric film on the support, and the performance of the devices was extensively evaluated with regard to linear response ranges, selectivity, applicability, and reusability. Overall, the paper-based sensors offer simplicity of fabrication, low cost and excellent reusability features. The design could also be extended to other applications in electricalbased approaches to be used in point-of-care (POC).
- A cork based substrate coupled with artificial antibodies for point-of-care detection of pro-inflammatory cytokine biomarkersPublication . Correia, Bárbara; Oliveira, Daniela; Vulpe, Georgeta; Tavares, Ana P. M.; Sales, M. Goreti F.; Duarte, Abel J.; Sharma, Sanjiv; Moreira, Felismina T. C.Whilst single use point of care testing (PoCT) devices have transformed healthcare globally, there are major concerns over their environmental consequences. These concerns could be addressed by employing devices made of environmentally friendly materials. Herein, we report on the use of cork based PoCT devices. Cork is known to be fully biodegradable and can be easily recycled without producing toxic residues. We report on how a cork-based substrate coupled with a molecularly imprinted polymer (MIP) that serves as an “artificial antibody” can be used for point-of-care testing of the pro-inflammatory biomarker interleukin 6 (IL-6). The featured PoCT device has an electrochemical transducer that provides the desired clinical dynamic range for blood and can measure concentrations as low as 1 pg mL−1, indicating its usefulness in point of care measurements for monitoring pathological disorders, worldwide. In addition, it has a huge environmental impact as it can reduce the waste generated by other polymeric/ceramic carriers used for the same purpose.
- Haemoglobin smart plastic antibody material tailored with charged binding sites on silica nanoparticles: its application as an ionophore in potentiometric transductionPublication . Tavares, Ana P. M.; Moreira, Felismina T. C.; Sales, M. Goreti F.This work uses surface imprinting to design a novel smart plastic antibodymaterial (SPAM) for Haemoglobin (Hb). Charged binding sites are described here for the first time to tailor plastic antibody nanostructures for a large size protein such as Hb. Its application to design small, portable and low cost potentiometric devices is presented. The SPAM material was obtained by linking Hb to silica nanoparticles and allowing its ionic interaction with charged vinyl monomers. A neutral polymeric matrix was created around these and the imprinted protein removed. Additional materials were designed in parallel acting as a control: a neutral imprinted material (NSPAM), obtained by removing the charged monomers from the procedure, and the Non-Imprinted (NI) versions of SPAM and NSPAM by removing the template. SEM analysis confirmed the surface modification of the silica nanoparticles. All materials were mixed with PVC/plasticizer and applied as selective membranes in potentiometric transduction. Electromotive force (emf) variations were detected only for selective membranes having a lipophilic anionic additive in the membrane. The presence of Hb inside these membranes was evident and confirmed by FTIR, optical microscopy and Raman spectroscopy. The best performance was found for SPAM-based selective membranes with an anionic lipophilic additive, at pH 5. The limits of detection were 43.8 mg mL 1 and linear responses were obtained down to 83.8 mg mL 1, with an average cationic slope of +40 mV per decade. Good selectivity was also observed against other coexisting biomolecules. The analytical application was conducted successfully, showing accurate and precise results.
- Irreversible temperature indicator based cellulose membranes conjugated with leuco-dye pigmentPublication . Carvalho, Margarida; Tavares, Ana P. M.; Marques. Maria A.; Alves, Joaquim J.; Figueira, Joana; Morais, Maria; Pinto, Joana V.; Moreira, Felismina T. C.This research focuses on the development of thermochromic membranes made of cellulose acetate (CA) for temperature monitoring of sensitive food products. Two dual TC membranes developed for the control of different temperature ranges were formulated using a three-component system: a leuco-dye membrane (crystal violet lactone, CVL) integrated with an acidic membrane containing the color developer (salicylic acid) and the acidic solvent with different melting points (decanoic acid, DA, or methacrylic acid, MA). The CVL membrane, together with the DA membrane, showed an irreversible color change when exposed to 35°C, which was facilitated by the melting of DA. The CVL membrane also underwent an irreversible color change when exposed to 15°C together with the MA membrane. The membranes were characterized in detail using scanning electron microscopy. The evaluation of color changes, reproducibility, specificity, and stability ensured the practical suitability of these membranes. Overall, this innovative approach has proven to be a reproducible, sustainable, cost-effective method to produce irreversible colorimetric temperature sensors. These sensors have significant potential for applications in the food and pharmaceutical industries and offer a promising way to improve product safety and quality.
- 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.
- Synthesis of an antibody-like material for the detection of AlbuminPublication . Tavares, Ana P. M.; Sales, M. Goreti F.A novel molecularly imprinted polymer (MIP) is presented for the detection of Albumin, currently a biomarker of several diseases. The material acted as an antibody for Albumin and was obtained through a bulk imprinting approach, by electropolymerizing Eriochrome blackT (EBT) around the target protein.