Browsing by Author "Sales, M. Goreti F."
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- Amplified Sensitivity in SERS Detection of L1CAM With Silver Plasmonic Mesoporous Silica Capsules on an Imprinted FilmsPublication . Castaño-Guerrero, Yuselis; Arjones-Fernández, Belén; Moreira, Felismina T. C.; Alvarez-Puebla, Ramon A.; Correa-Duarte, Miguel A.; Águas, H.; Sales, M. Goreti F.This study presents a novel approach for dual detection, leveraging a combination of a Raman reporter-bearing nanomaterial and molecular imprinting polymers (MIP). A core-shell Au-Ag nanoparticles (Au-Ag NPs) encapsulated in mesoporous silica nanocapsules (Au-Ag NCs) and a new MIP-based material targeting L1CAM are used. The MIP prepared via surface imprinting on a carbon screen-printed electrode (C-SPE) used thionine (TH) as a monomer. The plasmonic Au-AgNCs are further functionalized with the Raman reporter 4-mercaptobenzoic acid (MBA) and anti-L1CAM for selective detection by surface-enhanced Raman scattering (SERS) spectroscopy. The biosensor's analytical performance is evaluated using both SERS and electrochemical impedance spectroscopy (EIS). EIS analysis reveals a linear response within the concentration range of 0.1 to 100 ng mL−1 in buffer and serum samples. SERS demonstrates a sensitivity ten times higher than EIS. Selectivity study demonstrates the biosensor's excellent specificity toward L1CAM, with minimal interference from other compounds such as creatinine, glucose, and carbohydrate antigen 19-9 (CA 19-9). The Raman signal from the reporter molecule correlates with increasing L1CAM concentrations, reinforcing the analytical findings obtained through electrochemical analysis. Thus, the combination of dual detection and recognition capabilities presents promising potential for detecting diverse biomarkers, especially in critical scenarios where reducing false-positive or false-negative errors is crucial.
- Artificial antibodies based potentiometric sensors for monitoring diabetic ketoacidosisPublication . Martins, Pedro D.P.; Truta, Liliana A.A.N.A.; Fernandes, Rúben; Sales, M. Goreti F.Diabetic ketoacidosis is a pathological condition characterized for the complex disordered metabolic state (as hyperglycemia, metabolic acidosis, dehydration or ketosis), caused by the total failing of insulin production for beta cells in the islets of Langerhans (type 1 diabetes) or abnormalities in the peripheral insulin action and insulin secretion (type 2 diabetes). This pathogenesis can be also associated with the increase of counter-regulation hormones, leading to an increase in the hepatic glucose synthesis and a decrease in the peripheral tissues, resulting in hyperglycemia and hyperosmolarity. The effect of lipolysis increase leads to an increase in the production of free fatty acids, which are oxidized in the hepatic microsomal system and converted to acetyl-CoA. When acetyl-CoA production exceeds hepatic utilization capacity, this substance acts as a substrate for the production of ketone bodies (β-hydroxybutyrate (BHB), acetoacetate and acetone), causing ketonemia and metabolic acidosis.
- Assessing and comparing the total antioxidant capacity of commercial beverages: application to beers, wines, waters and soft drinks using TRAP, TEAC and FRAP methods.Publication . Queirós, Raquel B.; Tafulo, Paula A. R.; Sales, M. Goreti F.This work measures and tries to compare the Antioxidant Capacity (AC) of 50 commercial beverages of different kinds: 6 wines, 12 beers, 18 soft drinks and 14 flavoured waters. Because there is no reference procedure established for this purpose, three different optical methods were used to analyse these samples: Total Radical trapping Antioxidant Parameter (TRAP), Trolox Equivalent Antioxidant Capacity (TEAC) and Ferric ion Reducing Antioxidant Parameter (FRAP). These methods differ on the chemical background and nature of redox system. The TRAP method involves the transfer of hydrogen atoms while TEAC and FRAP involves electron transfer reactions. The AC was also assessed against three antioxidants of reference, Ascorbic acid (AA), Gallic acid (GA) and 6-hydroxy-2,5,7,8-tetramethyl- 2-carboxylic acid (Trolox). The results obtained were analyzed statistically. Anova one-way tests were applied to all results and suggested that methods and standards exhibited significant statistical differences. The possible effect of sample features in the AC, such as gas, flavours, food colouring, sweeteners, acidity regulators, preservatives, stabilizers, vitamins, juice percentage, alcohol percentage, antioxidants and the colour was also investigated. The AC levels seemed to change with brand, kind of antioxidants added, and kind of flavour, depending on the sample. In general, higher ACs were obtained for FRAP as method, and beer for kind of sample, and the standard expressing the smaller AC values was GA.
- Backside-surface imprinting as a new strategy to generate specific plastic antibody materialsPublication . Cabral-Miranda, Gustavo; Sales, M. Goreti F.; Gidlund, MagnusA backside protein-surface imprinting process is presented herein as a novel way to generate specific synthetic antibody materials. The template is covalently bonded to a carboxylated-PVC supporting film previously cast on gold, let to interact with charged monomers and surrounded next by another thick polymer. This polymer is then covalently attached to a transducing element and the backside of this structure (supporting film plus template) is removed as a regular “tape”. The new sensing layer is exposed after the full template removal, showing a high density of re-binding positions, as evidenced by SEM. To ensure that the templates have been efficiently removed, this re-binding layer was cleaned further with a proteolytic enzyme and solution washout. The final material was named MAPS, as in the back-side reading of SPAM, because it acts as a back-side imprinting of this recent approach. It was able to generate, for the first time, a specific response to a complex biomolecule from a synthetic material. Non-imprinted materials (NIMs) were also produced as blank and were used as a control of the imprinting process. All chemical modifications were followed by electrochemical techniques. This was done on a supporting film and transducing element of both MAPS and NIM. Only the MAPS-based device responded to oxLDL and the sensing layer was insensitive to other serum proteins, such as myoglobin and haemoglobin. Linear behaviour between log(C, μg mL−1) versus charged tranfer resistance (RCT, Ω) was observed by electrochemical impedance spectroscopy (EIS). Calibrations made in Fetal Calf Serum (FCS) were linear from 2.5 to 12.5 μg mL−1 (RCT = 946.12 × log C + 1590.7) with an R-squared of 0.9966. Overall, these were promising results towards the design of materials acting close to the natural antibodies and applied to practical use of clinical interest.
- Biomimetic norfloxacin sensors made of molecularly-imprinted materials for potentiometric transductionPublication . Moreira, Felismina T. C.; Freitas, Victor De; Sales, M. Goreti F.A biomimetic sensor for norfloxacin is presented that is based on host-guest interactions and potentiometric transduction. The artificial host was imprinted into polymers made from methacrylic acid and/or 2-vinyl pyridine. The resulting particles were entrapped in a plasticized poly(vinyl chloride) (PVC) matrix. The sensors exhibit near-Nernstian response in steady state evaluations, and detection limits range from 0.40 to 1.0 μg mL−1, respectively, and are independent of pH values at between 2 and 6, and 8 and 11, respectively. Good selectivity was observed over several potential interferents. In flowing media, the sensors exhibit fast response, a sensitivity of 68.2 mV per decade, a linear range from 79 μM to 2.5 mM, a detection limit of 20 μg mL−1, and a stable baseline. The sensors were successfully applied to field monitoring of norfloxacin in fish samples, biological samples, and pharmaceutical products.
- Biomimetic norfloxacin sensors made of molecularly-imprinted materials for potentiometric transductionPublication . Moreira, Felismina T. C.; Freitas, Victor; Sales, M. Goreti F.A biomimetic sensor for norfloxacin is presented that is based on host-guest interactions and potentiometric transduction. The artificial host was imprinted into polymers made from methacrylic acid and/or 2-vinyl pyridine. The resulting particles were entrapped in a plasticized poly(vinyl chloride) (PVC) matrix. The sensors exhibit near-Nernstian response in steady state evaluations, and detection limits range from 0.40 to 1.0 μgmL−1, respectively, and are independent of pH values at between 2 and 6, and 8 and 11, respectively. Good selectivity was observed over several potential interferents. In flowing media, the sensors exhibit fast response, a sensitivity of 68.2 mV per decade, a linear range from 79 μM to 2.5 mM, a detection limit of 20 μgmL−1, and a stable baseline. The sensors were successfully applied to field monitoring of norfloxacin in fish samples, biological samples, and pharmaceutical products
- A biomimetic sensor for monitoring oxidative stress biomarker in point-of-carePublication . Martins, Gabriela V.; Fortunato, Elvira; Fernandes, Helena R.; Sales, M. Goreti F.Free radicals and other reactive species are constantly generated in vivo and can cause oxidative damage to biomolecules, a process that seems to play an important role at the origin of cancer. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) is a major product of DNA hydroxylation and is considered a biomarker of damage caused by oxidative stress (OS). Thus, early diagnosis of OS biomarkers may be used as a fundamental tool in cancer prevention and in more efficient therapeutic strategies. For this purpose, a biomimetic sensor for 8-OHdG detection and quantification by Electrochemical Impedance Spectroscopy (EIS) is proposed herein. The biomimetic sensor was obtained by modifying a clean gold (Au) electrode with a OH-terminal thiol compound, followed by direct electropolymerization of phenol in the presence of 8-OHdG. The biomimetic/Au acted as working electrode, while glassy carbon and Ag/AgCl were used as counter and reference electrodes, respectively. Electropolymerization of phenol was performed by Cyclic Voltammetry (CV) over the potential range 0.2 to 0.9 V in pH 7.0 PBS buffer, enabling the formation of a non-conductive layer. Non-imprinted materials (NIM) were also performed by removing the template from the procedure and, then, the ability of the polymer to interact non-specifically with the template was measured. Preliminary results showed the development of a direct and label-free biomimetic sensor with good performance, stability and sensibility. In particular, only MIP material was able to rebind to the target molecule and produce a linear response against EIS on the range 0.010 to 10ng/ml. Overall, the biosensor described herein is simple, precise and may allow routine use for biological samples on-site.
- Biomimetic Sensor Potentiometric System for Doxycycline Antibiotic Using a Molecularly Imprinted Polymer as an Artificial Recognition ElementPublication . Kamel, Ayman H.; Moreira, Felismina T. C.; Sales, M. Goreti F.Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. A Biomimetic Sensor Potentiometric System was developed for assessment of doxycycline (DOX) antibiotic. The molecularly imprinted polymer (MIP) was synthesized by using doxycycline as a template molecule, methacrylic acid (MAA) and/or acrylamide (AA) as a functional monomer and ethylene glycol dimethacrylat (EGDMA) as a cross-linking agent. The sensing elements were fabricated by the inclusion of DOX imprinted polymers in polyvinyl chloride (PVC) matrix. The sensors showed a high selectivity and a sensitive response to the template in aqueous system. Electrochemical evaluation of these sensors under static (batch) mode of operation reveals near-Nernstian response. MIP/MAA membrane sensor was incorporated in flow-through cells and used as detectors for flow injection analysis (FIA) of DOX. The method has the requisite accuracy, sensitivity and precision to assay DOX in tablets and biological fluids.
- Biomimetic sensors of molecularly-imprinted polymers for chlorpromazine determinationPublication . Moreira, Felismina T. C.; Sales, M. Goreti F.A new man-tailored biomimetic sensor for Chlorpromazine host-guest interactions and potentiometric transduction is presented. The artificial host was imprinted within methacrylic acid, 2-vinyl pyridine and 2-acrylamido-2-methyl-1-propanesulfonic acid based polymers. Molecularly imprinted particles were dispersed in 2-nitrophenyloctyl ether and entrapped in a poly(vinyl chloride) matrix. Slopes and detection limits ranged 51–67 mV/decade and 0.46–3.9 μg/mL, respectively, in steady state conditions. Sensors were independent from the pH of test solutions within 2.0–5.5. Good selectivity was observed towards oxytetracycline, doxytetracycline, ciprofloxacin, enrofloxacin, nalidixic acid, sulfadiazine, trimethoprim, glycine, hydroxylamine, cysteine and creatinine. Analytical features in flowing media were evaluated on a double-channel manifold, with a carrier solution of 5.0 × 10−2 mol/L phosphate buffer. Near-Nernstian response was observed over the concentration range 1.0 × 10−4 to 1.0 × 10−2 mol/L. Average slopes were about 48 mV/decade. The sensors were successfully applied to field monitoring of CPZ in fish samples, offering the advantages of simplicity, accuracy, automation feasibility and applicability to complex samples.
- Biomimetic sensors of molecularly-imprinted polymers for chlorpromazine determinationPublication . Moreira, Felismina T. C.; Sales, M. Goreti F.A new man-tailored biomimetic sensor for Chlorpromazine host-guest interactions and potentiometric transduction is presented. The artificial host was imprinted within methacrylic acid, 2-vinyl pyridine and 2-acrylamido-2-methyl-1-propanesulfonic acid based polymers. Molecularly imprinted particles were dispersed in 2-nitrophenyloctyl ether and entrapped in a poly(vinyl chloride) matrix. Slopes and detection limits ranged 51–67 mV/decade and 0.46–3.9 μg/mL, respectively, in steady state conditions. Sensors were independent fromthe pHof test solutionswithin 2.0–5.5.Good selectivitywas observed towards oxytetracycline, doxytetracycline, ciprofloxacin, enrofloxacin, nalidixic acid, sulfadiazine, trimethoprim, glycine, hydroxylamine, cysteine and creatinine. Analytical features in flowing media were evaluated on a double-channel manifold, with a carrier solution of 5.0×10−2 mol/L phosphate buffer. Near-Nernstian response was observed over the concentration range 1.0×10−4 to 1.0×10−2 mol/L. Average slopes were about 48 mV/decade. The sensors were successfully applied to field monitoring of CPZ in fish samples, offering the advantages of simplicity, accuracy, automation feasibility and applicability to complex samples.