Browsing by Author "Freire, Cristina"
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- Assessment of 83 pharmaceuticals in WWTP influent and effluent samples by UHPLC-MS/MS: Hourly variationPublication . Paíga, Paula; Correia, Manuela; Fernandes, Maria João; Silva, Ana Margarida; Martins de Carvalho, Maria Manuela; Vieira, Joana; Jorge, Sandra; Silva, Jaime Gabriel; Freire, Cristina; Delerue-Matos, CristinaThe removal efficiency of pharmaceuticals in wastewater treatment plants (WWTPs) is variable and some of these compounds pass these plants almost intact and others presenting a removal efficiency close to 100%. Their incomplete removal results in a continuous discharge of pharmaceuticals into the environment. To assess the profile of contamination of influents and effluents over a day, a set of 83 pharmaceuticals were evaluated hourly in a WWTP in Leiria, Portugal. The composite samples of the influent and effluent were also collected. Concentrations varied from 1 in WWTP influents, and carbamazepine, fluoxetine, sertraline the pharmaceuticals with an RQ > 1 in WWTP effluents.
- Development of a disposable paper-based potentiometric immunosensor for real-time detection of a foodborne pathogenPublication . Silva, Nádia; Almeida, Cláudio M.R.; Magalhães, Júlia M.C.S.; Gonçalves, Maria P.; Freire, Cristina; Delerue-Matos, CristinaThis work reports a new paper-based sensing platform and its application in a label-free potentiometric immunosensor for Salmonella typhimurium detection based on the blocking surface principle. A paper-based strip electrode was integrated with a filter paper pad which acted as a reservoir of the internal solution. The design offers a convenient platform for antibody immobilization and sampling, proving also that is a simple and affordable methodology to control an ionic flux through a polymer membrane. Two different immunosensing interfaces were assembled on the developed paper-strip electrode. The simplest interface relied on direct conjugation of the antibody to the polymer membrane and the second one resorted to an intermediate layer of a polyamidoamine dendrimer, with an ethylenediamine core from the fourth generation. Electrochemical impedance spectroscopy was used to assess the successive interface modification steps and the resulting analytical performance of both immunosensors was compared. For such, the potential shift derived from the blocking effect of the ionic flux caused by antigen-antibody conjugation was correlated with the logarithm of the Salmonella typhimurium concentration in the sample. In optimized conditions, a limit of detection of 5 cells mL-1 was achieved. As a proof-of-concept, the proposed method was applied to apple juice samples, demonstrating to be a suitable prototype to be used in real scenarios in useful time (<1 h assay).
- Electrochemical biosensors for Salmonella: State of the art and challenges in food safety assessmentPublication . Silva, Nádia; Magalhães, Júlia M.C.S.; Freire, Cristina; Delerue-Matos, CristinaAccording to the recent statistics, Salmonella is still an important public health issue in the whole world. Legislated reference methods, based on counting plate methods, are sensitive enough but are inadequate as an effective emergency response tool, and are far from a rapid device, simple to use out of lab. An overview of the commercially available rapid methods for Salmonella detection is provided along with a critical discussion of their limitations, benefits and potential use in a real context. The distinguished potentialities of electrochemical biosensors for the development of rapid devices are highlighted. The state-of-art and the newest technologic approaches in electrochemical biosensors for Salmonella detection are presented and a critical analysis of the literature is made in an attempt to identify the current challenges towards a complete solution for Salmonella detection in microbial food control based on electrochemical biosensors.
- Evaluation of the Extraction Temperature Influence on Polyphenolic Profiles of Vine-Canes (Vitis vinifera) Subcritical Water ExtractsPublication . Dorosh, Olena; M. Moreira, Manuela; Pinto, Diana; F. Peixoto, Andreia; Freire, Cristina; Costa, Paulo; Rodrigues, Francisca; Delerue-Matos, CristinaThis work focused on evaluating the possibility of using vineyard pruning wastes from two Portuguese Vitis vinifera varieties; Touriga Nacional (TN) and Tinta Roriz (TR), as new potential ingredients for the nutraceutical industry. An environmentally friendly extraction technique; namely subcritical-water extraction (SWE), was employed. The overall results indicate that phenolic acids were the major class of compounds quantified; being gallic acid the principal one. The highest value for total phenolic content (TPC) was obtained for the TR extract at 250 °C (181 ± 12 mg GAE/g dw). In terms of antioxidant activity; the DPPH values for the extracts obtained at 250 °C were approximately 4-fold higher than the ones obtained at 125 °C; with TR extract presenting the highest value (203 ± 22 mg TE/g dw). Thus, the TR extract obtained through SWE at 250 °C was selected to evaluate the scavenging activity and the in vitro effects on cells due to the best results achieved in the previous assays. This extract presented the ability to scavenge reactive oxygen species (O2●-, HOCl and ROO●). No adverse effects were observed in HFF-1 viability after exposure to extract concentrations below 100 μg/mL. This work demonstrated that vine-canes extracts could be a potential ingredient to nutraceutical industry
- Green-Sustainable Recovery of Phenolic and Antioxidant Compounds from Industrial Chestnut Shells Using Ultrasound-Assisted Extraction: Optimization and Evaluation of Biological Activities In VitroPublication . Lameirão, Fátima; Pinto, Diana; F. Vieira, Elsa; F. Peixoto, Andreia; Freire, Cristina; Sut, Stefania; Dall’Acqua, Stefano; Costa, Paulo; Delerue-Matos, Cristina; Rodrigues, FranciscaChestnut processing industry generates large amounts of by-products, including leaves, burs and shells that are a source of bioactive compounds. The purpose of this study was to establish an ultrasound-assisted extraction (UAE) of phenolic and antioxidant compounds from industrial chestnut shells. A central composite design (CCD) was conducted to analyze the effects of time (4–46 min) and temperature (34–76 °C) in the antioxidant activity (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP)) and total phenolic compounds (TPC) of chestnut shells extracts. The optimal extraction conditions were obtained at 70 °C for 40 min. The optimal extract was characterized regarding phenolic profile, radical scavenging capacity, and effects on intestinal and dermal cell lines. The optimal extract revealed high amounts of ellagic acid (40.4 µg/mg dw), followed by caffeic acid derivative (15.4 µg/mg dw) and epigallocatechin (15.3 µg/mg dw). Indeed, the extract exhibited the highest scavenging efficiencies against NO● (IC50 = 0.1 µg/mL) and HOCl (IC50 = 0.7 µg/mL) and did not conducted to a decrease on HaCaT and HFF-1 viability up to 100 μg/mL. Oppositely, a decrease on Caco-2 and HT29-MTX viability was observed. This study suggests that UAE could be a sustainable option to valorize chestnut shells as raw material for different industries.
- In situ formation of gold nanoparticles in polymer inclusion membrane: Application as platform in a label-free potentiometric immunosensor for Salmonella typhimurium detectionPublication . Silva, Nádia; Magalhães, Júlia M.C.S.; Barroso, M. Fátima; Oliva-Teles, MT; Freire, Cristina; Delerue-Matos, CristinaPolymeric ion selective electrodes are highly sensitive to changes in zero current ion flow and this offers a route to signal amplification in label-free potentiometric immunosensors. In this work, a label-free potentiometric immunosensor toward Salmonella typhimurium (ST) assembled in a home-made pipette-tip electrode is described. The signal-output amplification was implemented on a gold nanoparticle polymer inclusion membrane (AuNPs-PIM) which was used as sensing platform and for antibody immobilization. Additionally, a marker ion was used to detect the antibody-antigen binding event at the electrode surface. The immunosensor construction was performed in several steps: i) gold salt ions extraction in PVC membrane; ii) AuNPs formation using Na2EDTA as reduction agent; iii) antibody anti-Salmonella conjugation on AuNPs-PIM in pipette-tip electrodes. The potential shift observed in potentiometric measurements was derived simply from the blocking effect in the ionic flux caused by antigen-antibody conjugation, without no extra steps, mimetizing the ion-channel sensors. A detection limit of 6 cells mL-1 was attained. As proof-of-concept, recovery studies were performed in spiked commercial apple juice samples with success. Due to the simplicity of use, the appealing cost of equipment and sensor production and being able to provide a quick analytical response (less than 1 h for a complete assay, including sample preparation for analysis), this scheme represents a good prototype device for the detection of foodborne pathogens like ST or other immune-responsive bacteria.
- Laccase–Prussian blue film–graphene doped carbon paste modified electrode for carbamate pesticides quantificationPublication . Oliveira, Thiago M. B. F.; Barroso, M. Fátima; Morais, Simone; Araújo, Mariana; Freire, Cristina; Lima-Neto, Pedro de; Correia, Adriana N.; Oliveira, M. Beatriz P. P.; Delerue-Matos, CristinaA novel enzymatic biosensor for carbamate pesticides detection was developed through the direct immobilization of Trametes versicolor laccase on graphene doped carbon paste electrode functionalized with Prussianblue films (LACC/PB/GPE). Graphene was prepared by graphite sonication-assisted exfoliation and characterized by transmission electron microscopy and X-ray photoelectron spectro- scopy. The Prussian blue film electrodeposited onto graphene doped carbon paste electrode allowed considerable reduction of the charge transfer resistance and of the capacitance of the device.The combined effects of pH, enzyme concentration and incubation time on biosensor response were optimized using a 23 full-factorial statistical design and response surface methodology. Based on the inhibition of laccase activity and using 4-aminophenol as redox mediator at pH 5.0,LACC/PB/GPE exhibited suitable characteristics in terms of sensitivity, intra-and inter-day repeatability (1.8–3.8% RSD), reproducibility (4.1 and 6.3%RSD),selectivity(13.2% bias at the higher interference: substrate ratios tested),accuracy and stability(ca. twenty days)for quantification of five carbamates widely applied on tomato and potato crops.The attained detection limits ranged between 5.2×10−9 mol L−1(0.002 mg kg−1 w/w for ziram)and 1.0×10−7 mol L−1 (0.022 mg kg−1 w/w for carbofuran).Recovery values for the two tested spiking levels ranged from 90.2±0.1%(carbofuran)to 101.1±0.3% (ziram) for tomato and from 91.0±0.1%(formetanate)to 100.8±0.1%(ziram)for potato samples.The proposed methodology is appropriate to enable testing pesticide levels in food samples to fit with regulations and food inspections.
- MnFe2O4@CNT-N as novel electrochemical nanosensor for determination of caffeine, acetaminophen and ascorbic acidPublication . Fernandes, Diana M.; Silva, Nádia; Pereira, Clara; Moura, Cosme; Magalhães, Júlia M.C.S.; Bachiller-Baeza, Belén; Rodríguez-Ramos, Inmaculada; Guerrero-Ruiz, Antonio; Delerue-Matos, Cristina; Freire, CristinaFor the first time, a glassy carbon electrode (GCE) modified with novel N-doped carbon nanotubes (CNT-N) functionalized with MnFe2O4 nanoparticles (MnFe2O4@CNT-N) has been prepared and applied for the electrochemical determination of caffeine (CF), acetaminophen (AC) and ascorbic acid (AA). The electrochemical behaviour of CF, AC and AA on the bare GCE, CNT-N/GCE and MnFe2O4@CNT-N/GCE were carefully investigated using cyclic voltammetry (CV) and square-wave voltammetry (SWV). Compared to bare GCE and CNT-N modified electrode, the MnFe2O4@CNT-N modified electrode can remarkably improve the electrocatalytic activity towards the oxidation of CF, AC and AA with an increase in the anodic peak currents of 52%, 50% and 55%, respectively. Also, the SWV anodic peaks of these molecules could be distinguished from each other at the MnFe2O4@CNT-N modified electrode with enhanced oxidation currents. The linear response ranges for the square wave voltammetric determination of CF, AC and AA were 1.0 × 10−6 to 1.1 × 10−3 mol dm−3, 1.0 × 10−6 to 1.0 × 10−3 mol dm−3 and 2.0 × 10−6 to 1.0 × 10−4 mol dm−3 with detection limit (S/N = 3) of 0.83 × 10−6, 0.83 × 10−6 and 1.8 × 10−6 mol dm−3, respectively. The sensitivity values at the MnFe2O4@CNT-N/GCE for the individual determination of AC, AA and CF and in the presence of the other molecules showed that the quantification of AA and CF show no interferences from the other molecules; however, AA and CF interfered in the determination of AC, with the latter molecule showing the strongest interference. Nevertheless, the obtained results show that MnFe2O4@CNT-N composite material acted as an efficient electrochemical sensor towards the selected biomolecules.
- PMo11V@N-CNT electrochemical properties and its application as electrochemical sensor for determination of acetaminophenPublication . Fernandes, Diana M.; Nunes, Marta; Bachiller-Baeza, Belén; Rodríguez-Ramos, Inmaculada; Guerrero-Ruiz, Antonio; Delerue-Matos, Cristina; Freire, CristinaA polyoxometalate-nanocarbon composite, PMo11V@N-CNT, was prepared by a simple procedure which consisted of the immobilization of phosphovanadomolybdate (PMo11V) onto N-doped carbon nanotubes (N-CNT). The FTIR and XPS characterizations confirmed its successful synthesis. The cyclic voltammograms of glassy carbon electrode (GCE) modified with PMo11V and PMo11V@N-CNT showed four Mo-centred redox processes (MoVI/V) and a vanadium redox process (VV/IV). All were surface-confined redox processes. Additionally, PMo11V@N-CNT/GCE showed good stability and well-resolved redox peaks with high current intensities. The electrocatalytic sensing properties of PMo11V@N-CNT/GCE towards acetaminophen (AC) in the presence of tryptophan (TRP) were evaluated by square wave voltammetry. Under the conditions used, the peak current increased linearly with AC concentration in the presence of TRP, with a linear range from 1.5 × 10−6 to 3.9 × 10−4 mol dm−3 and a detection limit of 1.0 × 10−6 mol dm−3.
- Production of ethyl levulinate fuel bioadditive from 5-hydroxymethylfurfural over sulfonic acid functionalized biochar catalystsPublication . Peixoto, Andreia F.; Ramos, Ruben; Moreira, Manuela M.; Soares, O. Salomé G.P.; Ribeiro, Lucilia S.; Pereira, Manuel F.R.; Delerue-Matos, Cristina; Freire, CristinaIn this work, a series of novel -SO3H functionalized biochar materials were prepared and investigated for the first time as catalysts for the production of fuel additive ethyl levulinate (EL) from biomass-derived 5-hydroxymethylfurfural (HMF). The employed biochar was directly produced from vineyard pruning wastes by a simple hydrothermal treatment using water in subcritical conditions followed by 3 different one-step sulfonation processes. The effects of sulfonating agent, reaction temperature, reaction time and alcohol solvent were examined. Full HMF conversion together with outstanding EL yields (over 84%) were achieved at 130 °C and after 6 h over the biochar functionalized with the organosilane 2-(4-chlorosulphonylphenyl)ethyltrimetoxysilane (BioC-S3). Catalyst characterization suggested that the high acid strength (0.983 mmol H+·g−1) derived from the anchoring of arylsulfonic groups were responsible for the promotion of acid-driven etherification and ethanolysis steps. The BioC-S3 catalyst can be recycled without a significant loss of catalytic activity, indicating the stability of – SO3H organosilane group structure in the porous biochar. The obtained results offer a competitive alternative for the production of fuel additives, such as alkyl levulinates, using low-cost and easy-to-prepare biochar-based catalysts, all from lignocellulose resources, as an example to support a future exploitation of a potential biorefinery.