Publications

Abstract The promotion of positive attitudes towards science is an important goal of science education. This research aimed to identify students' attitudes towards science and whether their participation within a citizen science project has contributed to positive attitudinal changes. So, an attitudinal scale was developed, validated, and applied (as a pre and post-test) to 574 students aged between 12 and 14 years old. Positive attitudes towards science were recorded from the outset among children of both groups. Students' participation within the experimental group enhanced relevant positive attitudinal changes at the level of the critical analysis dimension, related to the perception of skills development such as questioning or critical thinking. Furthermore, positive attitudinal changes were achieved within the affinity dimension, related to perceived self-efficacy and appreciation of science and science classes. Positive attitudinal changes towards science among students indicate that citizen science contributes to enhance affective and attitudinal domains of their scientific literacy.

Abstract The development of composites from 1D and 2D nanocarbon building blocks, namely carbon nanotubes and graphene layers, with enhanced properties or novel functionalities is an emerging challenge in material science. Herein, we developed a colloid-based approach using surfactants and polymers to non-covalently functionalize multiwalled carbon nanotubes (MWNTs) and graphene nanoplatelets (GnPs), and to fabricate GnP@MWNT nanocomposites via an electrostatic-driven assembly process in aqueous solution. In the assembly process, two building methods were used and compared (bulk mixing and adapted layer-by-layer assembly), using surfactant and polymer/surfactant combinations as the dispersants for the initial nanomaterials. After their characterization by scanning electron microscopy, Raman spectroscopy and BET analysis, the nanocomposites were evaluated as electrocatalysts for the oxygen reduction reaction (ORR). Results show that the type of the dispersant (namely the presence of polymer) plays a more relevant role than the specific building method in almost all the ORR parameters. Further, the nanocomposites show selectivity toward the 2-electron pathway oxygen reduction for the electrochemical production of hydrogen peroxide. The development and optimization of further nanocomposite electrocatalysts can be pursued using this type of versatile and robust assembly method.

Abstract In this work, we explore the ability of newly synthesized threonine-derived surfactants to form robust, versatile and cytocompatible catanionic vesicles when mixed with gemini surfactants, as potential effective nanocarriers for biomolecules. The threonine surfactants consist of single-tailed amphiphiles with carboxylate headgroups and varying alkyl tail length, CnThr, where n is the (even) number of tail C atoms, varying from 8 to 16. After an initial characterization of the micellization behavior of the neat CnThr surfactants (at pH = 7 and 12), the dodecyl derivative, C12Thr, was selected as the optimal surfactant to investigate regions of formation of spontaneous catanionic vesicles. Phase behavior studies and microstructural characterization of mixtures involving both conventional bis-quat n-s-n gemini (where n and s are the tail and spacer number of C atoms) and biocompatible serine-derived gemini surfactants were carried out. Light and electron microscopy, dynamic light scattering and zeta potential measurements show spontaneous vesicles indeed form and exhibit versatile features in terms of average size, morphology, polydispersity, surface charge and pH. The toxicological profile of the neat surfactants and C12Thr/gemini vesicles based on MTT assays with a L929 cell line was also evaluated, showing good levels of in vitro cytocompatibility. Overall, the assortment of developed catanionic vesicles offers very attractive physicochemical and biological features to be explored for delivery purposes.

Abstract Drug delivery vectors based on amphiphiles have important features such as versatile physicochemical properties and stimuli-responsiveness. Amino acid-based surfactants are especially promising amphiphiles due to their enhanced biocompatibility compared to conventional surfactants. They can self-organize into micelles, vesicles and complex hierarchical structures, such as fibers, twisted and coiled ribbons, and tubules. In this work, we investigated the self-assembly and drug loading properties of a family of novel anionic double-tailed lysine-derived surfactants, with variable degree of tail length mismatch, designated as mLys10 and 10Lysn, where m and n are the number of carbon atoms in the tails. These surfactants form tubular aggregates with assorted morphologies in water that undergo gelation due to dense entanglement, as evidenced by light and electron microscopy. Lysozyme (LZM), an enzyme with antimicrobial properties, was selected as model protein for loading. After the characterization of the interfacial properties and phase behavior of the amphiphiles, the LZM-loading ability of the tubules was investigated, under varying experimental conditions, to assess the efficiency of the aggregates as pH- and temperature-sensitive nanocarriers. Further, the toxicological profile of the surfactants per se and surfactant/LZM hydrogels was obtained, using human skin fibroblasts (BJ-5ta cell line). Overall, the results show that the tubule-based hydrogels exhibit very interesting properties for the transport and controlled release of molecules of therapeutic interest.

Abstract <jats:p>As pesquisas voltadas a educação científica, especificamente, sobre o tema do Inquiry-Based Science Education (IBSE) eclodiram nos últimos anos. Investigar os principais contextos de aplicação, descobertas, dificuldades e desafios advindos do uso do IBSE na Educação Básica de Ciências. Foi realizada uma revisão de literatura, utilizando uma década de produções científicas – entre 2006 e 2016 – a partir da plataforma de busca avançada da Universidade do Porto que é fornecida pela EBSCO. O corpus de análise compreendeu 45 artigos. Os principais resultados indicam que o IBSE tem sido considerado uma abordagem muito eficaz, estimulando os estudantes a questionar e propor problemas, na construção de hipóteses e na divulgação e justificação dos resultados atingidos. A abordagem do IBSE permite que os estudantes aprendam num processo investigativo semelhante ao método científico, de modo cooperativo, construindo conexões com conceitos científicos e com questões cotidianas e preparando os estudantes para uma aprendizagem ao longo da vida. A prática do IBSE nas escolas não é uma tarefa fácil, existindo muitos desafios e dificuldades para os professores e estudantes, contudo, essas dificuldades e desafios impostos a prática do IBSE devem ser explorados e debatidos a fim de ser superados.</jats:p>

Abstract This work is part of a comprehensive study of the thermal properties of several molecules of tetradentate Schiff bases, obtained as condensation products of salicylaldehyde with alkyldiamines. Herein, we report an experimental thermochemical study of SALPN (N,N'-bis(salicylaldehydo)propylenediimine) and a computational thermochemical study of SALEN (N,N' -bis(salicylaldehydo)dimethylenediimine), SALPN and SALBUTEN (N,N'-bis(salicylaldehydo)tetramethylenediimine) ligands. The standard (p degrees =0.1 MPa) molar enthalpy of formation of crystalline SALPN, at T = 298.15 K, was determined using the static-bomb calorimetry technique. Also, the enthalpy of fusion of this ligand has been determined by differential scanning calorimetry. Additionally, using quantum chemical calculations at the CCSD(T) level of theory, we have calculated the gas-phase standard molar enthalpies of formation of three Schiff base ligands, SALEN, SALPN and SALBUTEN. Moreover, a computational study of the molecular structures of the ligands has been carried out.

Abstract Simple Summary: The Sodium/Iodide Simulator (NIS) is responsible for the uptake of iodide in the thyroid follicular cells. NIS is present in most differentiated thyroid carcinomas (DTC), allowing radioactive iodine (RAI) to be used to destroy malignant cells. However, a significant proportion of DTCs stop picking up iodide and become resistant to RAI therapy. This is mainly due to the symporter no longer being produced or not being placed correctly at the cell's membrane. This has been associated with mechanisms linked to malignant transformation, namely the overactivation of the so-called MAPK pathway. Thus, several drugs have been developed to inhibit this pathway, attempting to increase NIS levels and iodide uptake. However, MAPK inhibitors have had only partial success in restoring NIS expression. We found that the activity of another protein, the small GTPase RAC1, has an important role in this process, determining the outcome of MAPK inhibitors. Thus, our findings open new opportunities to find effective therapeutic alternatives for DTC resistant to RAI. The Sodium/Iodide Symporter (NIS) is responsible for the active transport of iodide into thyroid follicular cells. Differentiated thyroid carcinomas (DTCs) usually preserve the functional expression of NIS, allowing the use of radioactive iodine (RAI) as the treatment of choice for metastatic disease. However, a significant proportion of patients with advanced forms of TC become refractory to RAI therapy and no effective therapeutic alternatives are available. Impaired iodide uptake is mainly caused by the defective functional expression of NIS, and this has been associated with several pathways linked to malignant transformation. MAPK signaling has emerged as one of the main pathways implicated in thyroid tumorigenesis, and its overactivation has been associated with the downregulation of NIS expression. Thus, several strategies have been developed to target the MAPK pathway attempting to increase iodide uptake in refractory DTC. However, MAPK inhibitors have had only partial success in restoring NIS expression and, in most cases, it remained insufficient to allow effective treatment with RAI. In a previous work, we have shown that the activity of the small GTPase RAC1 has a positive impact on TSH-induced NIS expression and iodide uptake in thyroid cells. RAC1 is a downstream effector of NRAS, but not of BRAF. Therefore, we hypothesized that the positive regulation induced by RAC1 on NIS could be a relevant signaling cue in the mechanism underlying the differential response to MEK inhibitors, observed between NRAS- and BRAF-mutant tumors. In the present study, we found that the recovery of NIS expression induced through MAPK pathway inhibition can be enhanced by potentiating RAC1 activity in thyroid cell systems. The negative impact on NIS expression induced by the MAPK-activating alterations, NRAS Q61R and BRAF V600E, was partially reversed by the presence of the MEK 1/2 inhibitors AZD6244 and CH5126766. Notably, the inhibition of RAC1 signaling partially blocked the positive impact of MEK inhibition on NIS expression in NRAS Q61R cells. Conversely, the presence of active RAC1 considerably improved the rescue of NIS expression in BRAF V600E thyroid cells treated with MEK inhibitors. Overall, our data support an important role for RAC1 signaling in enhancing MAPK inhibition in the context of RAI therapy in DTC, opening new opportunities for therapeutic intervention.

Abstract The gas-phase enthalpies of formation of two fragrance compounds, methyl anthranilate and butyl anthranilate, at T = 298.15 K, were determined from the combination of the corresponding enthalpies of vaporisation and energies of combustion, obtained from Calvet microcalorimetry and combustion calorimetry measurements, respectively. Additionally, theoretical calculations were performed, using the G3(MP2)//B3LYP composite method, to estimate the gas-phase enthalpies of formation of the two fragrance compounds. The good agreement between the experimental and computational gas-phase enthalpies of formation of the methyl anthranilate and butyl anthranilate, provided the confidence for extending the theoretical study to propyl anthranilate. Furthermore, the results were interpreted in terms of enthalpic increments, aiming to evaluate and understand the energetic effect inherent to the alkyl group (methyl, ethyl, propyl or butyl) present in the ester functional group of the anthranilate derivatives. (c) 2021 Elsevier Ltd.

Abstract Combustion calorimetry is the predominant method for determination of enthalpies of formation for organic compounds. Both initial and final states of the calorimeter deviate significantly from the standard conditions. Correction of the obtained results to the standard state must be applied as accurately as pos-sible to determine the combustion energy with an acceptable uncertainty, which is typically a few hun-dredths of a percent. The correction procedures in their current form were introduced in 1956 with simplifications to allow application in a pre-computer era. In this work, the procedures have been updated with respect to both the equations and reference values. The most reliable data sources are iden-tified, and the updated algorithm is presented in the form of a Web-based tool available through the NIST TRC Web site. (c) 2021 Elsevier Ltd.

Abstract The energetic study of 2-aminobenzoxazole (ABO) and 2-methyl-6-nitrobenzoxazole (MNBO) has been developed using experimental and computational tools. The enthalpies of combustion, of fusion, and of sublimation of these compounds were measured by static-bomb combustion calorimetry, differential scanning calorimetry, and Calvet microcalorimetry drop-technique and/or the Knudsen-effusion method. Additionally, we calculated the gas-phase standard molar enthalpies of formation of these compounds, as well as of 2-methyl-6-nitrobenzothiazole (MNBT), through high level ab initio calculations, at the G3(MP2)//B3LYP level of theory. Furthermore, the energetic effects associated with the presence of the amino and nitro groups on the core of benzoxazole or benzothiazole molecules were also evaluated, as well as stabilizing electronic interactions occurring in the molecules. The latter were investigated through Natural Bonding Orbital (NBO) of the corresponding wave functions. Finally, the thermodynamic stability of the titled compounds was evaluated and a comparison with their sulfur heteroanalogs was achieved. In the gaseous phase, the oxygen derivatives exhibit the lowest tendency to decompose into their constituent elements at standard conditions.