Browsing by Author "Oliveira, Daniela"
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- Antigenotoxic properties of the halophyte Polygonum maritimum L. highlight its potential to mitigate oxidative stress-related damagePublication . Oliveira, Daniela; Dias, Maria Inês; Barros, Lillian; Custódio, Luísa; Oliveira, Rui P.Long-term exposure to dietary xenobiotics can induce oxidative stress in the gastrointestinal tract, possibly causing DNA damage and contributing to the initiation of carcinogenesis. Halophytes are exposed to constant abiotic stresses, which are believed to promote the accumulation of antioxidant metabolites like polyphenols. The aim of this study was to evaluate the antioxidant and antigenotoxic properties of the ethanol extract of the aerial part of the halophyte Polygonum maritimum L. (PME), which can represent a dietary source of bioactive compounds with potential to attenuate oxidative stress-related damage. The PME exhibited a high antioxidant potential, revealed by the in vitro capacity to scavenge the free radical DPPH (IC50 = 2.29 +/- 0.10 mu g/mL) and the improved viability of the yeast Saccharomyces cerevisiae under oxidative stress (p < 0.001, 10 min). An antigenotoxic effect of PME against H2O2-induced oxidative stress was found in S. cerevisiae (p < 0.05) with the dominant deletion assay. In vitro colorimetric assays and LC-DAD-ESI/MSn analysis showed that PME is a polyphenol-rich extract composed of catechin, (epi)catechin dimer and trimers, quercetin and myricetin glycosides. Hence, P. maritimum is a source of antioxidant and antigenotoxic metabolites for application in industries that develop products to provide health benefits.
- Development of high performance and facile to pack molecularly imprinted particles for aqueous applicationsPublication . Oliveira, Daniela; Freitas, Filipa; Kadhirvel, Porkodi; Dias, Rolando; Costa, Mário RuiDifferent kinds of molecularly imprinted particles were synthesized and compared, aiming at the development of materials combining high molecular recognition capabilities and facile use as column packing materials for chromatographic aqueous applications. Solution, inverse-suspension and precipitation polymerization were considered and two different model molecules (5-fluorouracil and caffeine) were used to highlight the effect of the interaction between the template molecule and the functional monomer on imprinting efficiency. Particles synthesized through the proposed inverse-suspension process exhibit facile use for packing columns, allow the stable running of chromatographic systems and present a high performance in drug uptake and release in aqueous media. Frontal analysis measurements highlight these key features of the synthesized particles. Drug sorption capabilities of 0.890 mol/g and 5.774 mol/g were measured for 5-fluorouracil and caffeine, respectively, using frontal analysis with eluents containing the target molecules at concentration 0.1 mM. Due to the lower amount of solvent required than with precipitation polymerization, the developed inverse-suspension process presents high synthesis yields, which can be exploited for the large-scale manufacture and commercialization of molecularly imprinted materials. The combined features of the particles makes possible their direct use in bioseparations or in the development of assays and pharmacokinetic studies concerning the presence of drugs in biological fluids.
- Development of stimuli-responsive smart hydrogels using molecular imprinting and interpenetrating polymer networksPublication . Oliveira, Tânia; Reitor, Patrícia; Oliveira, Daniela; Kadhirvel, Porkodi; Dias, Rolando; Costa, Mário RuiDifferent classes of stimuli-responsive smart hydrogels (SRSH) were synthesized in order to assess the usefulness of molecular imprinting and generation of interpenetrating polymer networks to obtain advanced materials with tailored properties/performance. Reversible Addition-Fragmentation Chain-Transfer (RAFT) polymerisation was exploited as an additional tool to increase the control on the formation process of these materials. Batch adsorption and frontal analysis (e.g. for 3-aminopyridine (3AMP) as depicted in the graphical abstract) techniques were used to quantify the affinity of different drugs with the produced SRSH. Stimulated drug release (e.g. due to temperature/pH changes) and protein immobilisation/release were also tested. Results obtained show that molecular imprinting and generation of interpenetrating networks are effective routes to obtain tailored materials with a particular affinity to selected template molecules.
- Development of tailored hydrogels using RAFT polymerization in continuous flow microreactorPublication . Machado, Carla; Oliveira, Tânia; Reitor, Patrícia; Oliveira, Daniela; Freitas, Filipa; Kadhirvel, Porkodi; Dias, Rolando; Costa, Mário RuiThis research is devoted to the development of tools aiding the production of smart hydrogels with tailored molecular architecture and properties. Molecular imprinting, RAFT polymerization and operation in continuous flow microreactor are individually considered and also simultaneously combined in order to try the synthesis of materials with improved performance.
- Estratégias de coping e qualidade de vida em doentes crónicosPublication . Oliveira, Daniela; Ramos, Olga Moura; Gomes, Maria José; Matos, Maria JoséA doença crónica é caracterizada pelas suas incapacidades e limitações tais como: limitações funcionais, dificuldade na concretização das atividades diárias e dos papéis desempenhados quer no ciclo familiar quer no social. A presença de um prognóstico incerto e a recorrência prolongada de tratamentos e de intervenções médicas, prejudicam a qualidade de vida destes doentes.
- Estudos experimentais e modelação matemática da libertação de fármacos em redes de polímeros interpenetrantesPublication . Oliveira, Daniela; Dias, RolandoAs redes de polímeros interpenetrantes (IPN) têm sido consideradas nos últimos anos como forma de melhorar as propriedades de materiais convencionais. Aumento do desempenho mecânico e incorporação simultânea de polímeros naturais e sintéticos no mesmo produto são exemplos de vantagens associadas aos IPNs. Neste trabalho foram explorados IPNs baseados em redes de ácido acrílico (AA) e N-isopropilacrilamida (NIPA) como forma de obtenção de materiais com sensibilidade simultânea ao pH (decorrente da rede de AA) e à temperatura (decorrente da rede de NIPA). Os hidrogéis resultantes apresentam potenciais aplicações em biomedicina e na indústria farmacêutica, nomeadamente na libertação controlada de fármacos. Os IPNs de AA/NIPA foram sintetizados através de polimerização radicalar clássica (FRP), tendo sido consideradas diferentes estratégias de interpenetração das redes de base (variação do solvente, concentrações, temperatura, iniciador, etc). Após purificação, os IPNs foram caracterizados em termos da variação da sua razão de inchamento (SR) quando colocados em soluções aquosas (procurando recriar meios biológicos) com diferentes valores de pH e temperatura. Os materiais sintetizados foram também caracterizados em termos da sua capacidade de adsorção/dessorção (retenção/libertação) de moléculas alvo importantes em biomedicina (ex. 5-fluoruracilo usado no tratamento do cancro ou 4-aminopiridina, potencialmente útil no tratamento da esclerose múltipla). Em concreto, foi quantificada a adsorção dos fármacos nos IPNs em modo fechado (batch) e também em modo contínuo. Para esse efeito, os materiais foram empacotados em colunas de GPC e submetidos a testes de análise frontal usando soluções aquosas contendo os fármacos. Adicionalmente, os IPNs foram ainda sujeitos a estudos de extração em fase sólida (SPE) envolvendo também soluções aquosas dos mesmos fármacos. Os resultados experimentais obtidos foram usados em estudos de modelação matemática, nomeadamente para a determinação de isotérmicas de adsorção (Langmuir, Freundlich, etc) e no desenvolvimento de ferramentas de cálculo auxiliadoras da interpretação dos resultados obtidos por análise frontal (quantificação da capacidade de adsorção). Com a investigação realizada mostra-se que a interpenetração de redes pode ser considerada na obtenção de hidrogéis com sensibilidade combinada a estímulos (ex. pH/temperatura) e que os materiais resultantes apresentam propriedades úteis em biomedicina, nomeadamente na retenção/libertação de fármacos quando selecionadas combinações de elevada afinidade entre o IPN e a molécula alvo.
- Modeling RAFT gelation and grafting of polymer brushes for the production of molecularly imprinted functional particlesPublication . Oliveira, Daniela; Dias, Rolando; Costa, Mário RuiRAFT precipitation polymerization was here used for the molecular imprinting of 5-fluorouracil (a drug used in cancer treatment) followed by grafting of polymer functional brushes in the particles surface. Materials combining high molecular recognition capabilities and stimulation triggered by changes in the surrounding environment (e.g. pH/temperature) have thus been sought. Mathematical modeling of the RAFT copolymerization of vinyl/divinyl monomers was used to describe the crosslinking process involved in the molecular imprinting step. The size of the grafted polymer functional brushes was estimated using models for the calculation of molecular weight distribution in RAFT homopolymerization. One of the goals of this study consists in the development of polymer reaction engineering tools for the design of synthesis conditions leading to tailored molecularly imprinted particles with responsive features. A first sketch of the two steps involved in the production of the MIP responsive particles is here presented. However, the need for new kinetic studies accounting for specificities of the molecular imprinting and surface extension processes (e.g. presence of template during molecular imprinting and solvent effects) is here identified. Measurements of the dynamics of gelation and brushes growth are also needed to perform model validation. Improvement on the modeling of RAFT gelation with heterogeneous conditions avoiding some simplifications and the amelioration of the numerical efficiency in the calculation of the MWD of RAFT polymers are other issues to be addressed in future works.
- Molecular imprinting of 5-fluorouracil in particles with surface RAFT grafted functional brushesPublication . Oliveira, Daniela; Dias, Rolando; Costa, Mário RuiMolecularly imprinted particles with surface grafted functional polymer brusheswere synthesized and evaluated aiming at the targeting of 5-fluorouracil (5-FU). A molecular imprinting material for 5-FU was prepared through precipitation crosslinking polymerization, in the presence of a RAFT agent, and choosing either methacrylic acid (MAA) or 2-hydroxyethyl methacrylate (HEMA) as functional monomers. In a later step, different kinds of functional polymer brushes, namely poly(methacrylic acid), poly(2-hydroxyethyl methacrylate) and poly(Nisopropylacrylamide) were grafted in the particles through a “grafting from” process starting on the RAFT groups present in their surface. The accomplishment of 5-FU imprinting was proven through comparative drug uptake measurements with imprinted/non-imprinted materials. Enhancement of 5-FU release in alkaline conditions comparatively to acidic environmentswas shown for particleswith different combinations of molecular imprinting and grafted functional brushes. TheMAA imprinting systemwith PMAA grafted functional brushes shows the highest improvement in 5-FU release triggered by a pH change from 2 to 10. Furthermore, for particles with PNIPA grafted brushes, a boost in drug release was also shown at T = 20 °C as compared to 40 °C. The novel achievements reported here put into evidence the combined benefits of molecularly imprinted particles with surface grafted functional polymer brushes concerning molecular recognition and stimulated 5-FU release.
- Persistence of antioxidant properties of Carpobrotus edulis L. extract after in vitro digestionPublication . Oliveira, Daniela; Dias, Maria Inês; Barros, Lillian; Custódio, Luísa; Oliveira, RuiThe human being is unknowingly cxposcd to many toxic chcrnicals through diet, which can trigger an excessive pra ductian a f reactive oxygen and ni trogen species that can cause a redax imbalance and generate oxidativc stress in thc gastrointcstin al tract, potcntially contri buting to the development of degenerative discases. In fact, oxidative stress has becn indi cated to contribute to ali three phases a f carcinogenesis. Thus, the attenuation of oxidative strcss could contribute to the prevention of cancer in itiation. Halophytes are associated wi th strong ant ioxidant capacity, which makes them excellent candidates to anen uale lhe oxidative stress in the gaslrointestinal tracl. For instance, Carpobrotus edulis L is an edible halophyte 1hal has been reported for its antioxidant properties and high content in phenolic compounds. However, most of these stud ies did not consider the impact of digeslion, which can alter the chemical structure of the phytochemicals and possibly their biaacti vilics. To our knowledge, there are no studies considering the efTect of digestion on lhe antiox idant properti es of C. edulis. The objecti ve of th is work was to evaluate the impact of digestion on the chemical compos ition and ant ioxidant capacity of C. edulis aerial part ethanol extract (CEE). The extract was subjected to in vilro simulation of human digestion (IVO) and aI the end we obtained the digesled extracl lhat becomes avai lable in lhe colon (DCEE). Both forms of lhe extract were subjected to chemical characterization by lhe Folin-Ciocalteu melhod and by LC-DADESI/ MS· to delect alterations caused by IVO. The anti oxidant capacity ofCEE and DCEE was evaluated in vi/ro by determ in ati an of scavenging of ni lric oxide (NO) and 2,2-diphenyl- l picrylhydrazyl (DPPH) rad icaIs and in viab il ity assays again st hydrogen peroxide (H,O,) in the yeast Saccharomyces cerevisiae. The resu lts showed Ihat lhe phenolic composition ofCEE was severely affected by IVO. as wel! as the capacity to scavenge the OPPH radical In oppositian, the capac ity to scavenge the NO rad ical increased. Moreover, CEE protected yeast cel ls against 1-1,0" corroborating the antioxidant propert ies reported in the li leralure. These properties seem to pers isl after IVO, bUl at a lower extent. Thus, although the IVD s ignificantly altered the chemi cal compos it ion of CEE and decreased the antioxidant capacity, lhe beneficiai effect is still relevant since it provided pratect ion against oxidative stress in the viabi lity assay in S. cerevisiae. Thercforc. C. edlllis scems to have potent ia l to be included in the human diet to decrease the oxidative stress generated in the gastrointestinal tract due to lhe recurrent consumption of contaminated foods and lhus could play a role in the prevention of carcinogenesis.
- A Prática de Ensino Supervisionada em contexto pré-escolar: uma experiência de intervenção colaborativaPublication . Oliveira, Daniela; Sanches, AngelinaConsiderando as exigências e desafios que a ação educativa pré-escolar representa, abordamos, nesta comunicação, a experiência realizada no decurso da prática de ensino supervisionada e os contributos da ação supervisiva para a construção da profissionalidade docente. Entre os desafios em que nos envolvemos, sublinhamos o da integração na dinâmica do projeto educativo da instituição. Para tal, tornou-se fundamental não apenas a pesquisa da literatura e a consulta da documentação disponível, como também o desenvolvimento de interações positivas com os membros da comunidade educativa, assumindo particular pertinência, nesse processo, o papel da supervisão. Outro importante desafio centrou-se no desenvolvimento de uma intervenção educativa que favorecesse a construção de um clima social, cognitivo e emocionalmente positivo, no quadro de respostas significativas, socializadoras e integradas. Neste âmbito, merece-nos particular reflexão a ação colaborativa estabelecida para que pudessem ser promovidas estratégias educativas responsivas a necessidades formativas e a problemas identificados. Entre estes sublinhamos o modo como o grupo crianças, com três anos de idade e que frequentava pela primeira vez a instituição, manifestava estar a gerir estados emocionais decorrentes da separação dos pais e da necessidade de partilhar os materiais e os espaços da sala/instituição. Assim, assumindo uma atitude indagadora sobre as dinâmicas de cooperação e supervisão desenvolvidas, propomos apresentar e discutir essa experiência, fazendo uma breve abordagem a referenciais teóricos, atividades promovidas e contributos ao nível do processo de ensino-aprendizagem e da construção da nossa profissionalidade docente.