Elisabete M. S. Castanheira

University of Minho, Bracara Augusta, Braga, Portugal

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Publications (41)51.73 Total impact

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  • Tetrahedron 12/2013; 69(48):10254-10261. · 2.80 Impact Factor
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    ABSTRACT: The photophysical properties (absorption and fluorescence) of four 6-(hetero)arylthieno[3,2-b]pyridine derivatives, the methyl 3-amino-6-(thien-3-yl)thieno[3,2-b]pyridine-2-carboxylate 1, the methyl 3-amino-6-(2,2′-bithienyl-5-yl)thieno[3,2-b]pyridine-2-carboxylate 2, the methyl 3-amino-6-(thien-2-yl)thieno[3,2-b]pyridine-2-carboxylate 3 and the methyl 3-amino-6-(fur-3-yl)thieno[3,2-b]pyridine-2-carboxylate 4, evaluated previously as potential antitumor compounds, were studied in solvents of different polarity. All compounds have reasonable fluorescence quantum yields and exhibit a solvatochromic behaviour. The thienopyridine derivatives were incorporated in lipid membranes of neat egg-yolk phosphatidylcholine (egg-PC), dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylglycerol (DPPG) and dioctadecyldimethylammonium bromide (DODAB). Fluorescence measurements indicate that all compounds are mainly located in the lipid bilayer, feeling the transition from the rigid gel phase to the liquid-crystalline phase. The most promising antitumor compounds, the thien-3-yl and the 2,2′-bithienyl-5-yl thienopyridine derivatives 1 and 2, were encapsulated in different nanoliposome formulations, considering future drug delivery applications using liposomes as carriers. Almost all the liposomes with incorporated compounds have diameters lower than 165 nm and generally low polydispersity. The formulation DPPC:DMPG:DSPE-PEG (1:1:0.1) exhibits a small diameter (below 100 nm), low polydispersity and reasonable negative zeta-potential values for both thienopyridines 1 and 2.
    Journal of Photochemistry and Photobiology A Chemistry 07/2013; 264:56-66. · 2.42 Impact Factor
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    ABSTRACT: PURPOSE: The main goal was to study the biochemical composition of the tear film in two different times of the day. METHODS: Tear samples were collected from 10 individuals, non contact lenses wearers, from the university population without pathologies. To assess daily variations in the tear film, samples were collected twice in the day, one early in the morning and another in the evening using capillary tubes. Tear protein profile was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), tumor necrosis factor α (TNF-α) and immunoglobulin A (IgA) were quantified by Enzyme-Linked ImmunoSorbent Assay (ELISA). Tear film stability was obtained through measurements of Non-Invasive Break Up Time and tear surface tension was measured by obtaining the Langmuir isotherms. RESULTS: The stability of the tear film was higher in the morning than in the afternoon; corresponding to a higher value of surface tension in the afternoon. Protein electrophoresis tear profile is variable during the day as IgA concentration decreased from morning to afternoon (p<0.05). TNF-α concentration also decreased, but there were not significant statistical differences (p=0.089). CONCLUSION: We concluded that there are daily variations in the composition and properties of the tear film, indicating that changes occur without being caused by contact lenses wear or by the presence of ocular and systemic pathologies. Presence of TNF-α is not a direct indication of inflammatory pathology, since this cytokine was identified in relatively high amounts in subjects without inflammatory pathology.
    Contact lens & anterior eye: the journal of the British Contact Lens Association 01/2013;
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    ABSTRACT: Several β-arylalanine derivatives containing fluorescent groups were prepared in good yields using a rhodium-catalysed conjugate addition of arylboronic acids to N,N-diprotected and N-monoprotected dehydroalanines. The best conditions for these reactions required the use of an excess of arylboronic acid (4 equiv.), [Rh(COD)2]BF4 as catalyst, and CsF as base in dioxane/H2O (10:1) at 110 °C. These conditions were also applied to several dipeptides with dehydroalanine residues. The photophysical properties of some of the β-arylalanines were studied in three solvents with different polarities. Due to the absence of the α,β-double bond, the absorption and fluorescence emission of the new compounds are dominated by the photophysical properties of the polycyclic aromatic fluorophores (naphthalene, phenanthrene, and pyrene). Considering the relatively high fluorescence quantum yield of these compounds, some of them may be useful as fluorescent markers for peptides and proteins.
    Annalen der Chemie und Pharmacie 01/2013; 2013(3). · 3.10 Impact Factor
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    ABSTRACT: New bis(oxazolyl)pyridine ligands for LnIII ions were prepared by using an expeditious methodology from threonine and dipicolinic chloride. The synthetic strategy includes a dehydration step to give a bis(dehydroaminobutyric acid) derivative followed by bromination and cyclization with DBU. Photophysical studies of EuIII and TbIII complexes of these ligands showed that the 2,6-bis(oxazolyl)pyridine moiety acts as an effective sensitizer for lanthanide luminescence and indicate the formation of 3:1 complexes [Ln{bis(oxazole)pyridine}3]3+.
    Annalen der Chemie und Pharmacie 07/2012; 2012(21). · 3.10 Impact Factor
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    ABSTRACT: A recently described non-viral gene delivery system [dioctadecyldimethylammonium bromide (DODAB)/monoolein (MO)] has been studied in detail to improve knowledge on the interactions between lamellar (DODAB) and non-lamellar-forming (MO) lipids, as a means to enhance their final cell transfection efficiency. Indeed, the morphology, fluidity, and size of these cationic surfactant/neutral lipid mixtures play an important role in the ability of these systems to complex nucleic acids. The different techniques used in this work, namely dynamic light scattering (DLS), fluorescence spectroscopy, differential scanning calorimetry (DSC), cryogenic transmission electron microscopy (cryo-TEM), light microscopy (LM), and surface pressure-area isotherms, allowed fully characterization of the phase behavior and aggregate morphology of DODAB/MO mixtures at different molar ratios. Overall, the results indicate that the final morphology of DODAB/MO aggregates depends on the balance between the tendency of DODAB to form zero-curvature bilayer structures and the propensity of MO to form non-bilayer structures with negative curvature. These results also show that in the MO-rich region, an increase in temperature has a similar effect on aggregate morphology as an increase in MO concentration.
    Journal of Colloid and Interface Science 02/2012; 374(1):206-17. · 3.17 Impact Factor
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    ABSTRACT: Among the strategies to improve a material's hemocompatibility, pre-coating with the tripeptide Arg-Gly-Asp (RGD) is used to favor endothelialization thus lowering thrombogenicity. The blood compatibility of native and RGD-modified bacterial cellulose (BC) was studied in this work for the first time. The plasma recalcification time and whole blood clotting results demonstrate the hemocompatibility of BC. A significant amount of plasma protein adsorb to BC fibres, however, according to analysis by intrinsic tryptophan fluorescence techniques when albumin, γ-globulin, and fibrinogen from pure protein solutions adsorb to BC do not undergo detectable conformational modifications. Human microvascular endothelial cells cultured on RGD-modified BC readily form a confluent cell layer, inhibiting the adhesion of platelets. As a general conclusion, both native and RGD-modified BCs may be classified as hemocompatible materials.
    Journal of Biomedical Materials Research Part A 06/2011; 98(4):554-66. · 2.83 Impact Factor
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    ABSTRACT: The main objective of this work was to increase the retarding effect of the acid dye Telon(®) Blue RR (C.I. Acid Blue 62; DyStar, Frankfurt, Germany) release on polyamide fibres dyeing by encapsulation of the dye in liposomes as an alternative to synthetic auxiliaries, in order to reduce effluent pollution. The retarding effect achieved with the use of mixed cationic liposomes of dioctadecyldimethylammonium bromide (DODAB)/soybean lecithin (containing a 10% molar fraction of DODAB) was better in comparison with either pure soybean lecithin liposomes or synthetic auxiliaries. The retarding effect of liposomes on the dye release was analysed through changes in the absorption and fluorescence spectra of the acid dye at different conditions. The effect of temperature (in the range of 25 °C - 70 °C) on the spectroscopic behaviour of the dye in the absence and in presence of polyamide was also studied, in order to simulate the dyeing conditions. Exhaustion curves obtained in dyeing experiments showed that, below 45 °C, the retarding effect of the mixed liposomes (lecithin/DODAB (9:1)) was similar to that of the auxiliaries, but better than the one of pure lecithin liposomes. At higher temperatures (above 45 °C), the system lecithin/DODAB presents a better performance, achieving a higher final exhaustion level when compared with the commercial leveling agent without losing the smoothing effect of lecithin.
    Journal of Liposome Research 06/2011; 21(2):151-7. · 1.91 Impact Factor
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    ABSTRACT: On treatment with DBU, esters of N-acyl-β-halodehydraminobutyric acids produce the title compounds in good to excellent yields.
    ChemInform 02/2011; 42(8).
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    ABSTRACT: A 3-(Phenanthren-9-yl)-1H-indole-2-carboxylic acid (2) obtained from the cleavage of the methyl ester of the methyl 3-(phenanthren-9-yl)-1H-indole-2-carboxylate (1) was inserted into a peptide containing the RGD sequence. The GGRGDG peptide sequence was prepared by solid phase synthesis and coupled to compound (2), using diisopropylcarbodiimide (DIC) and 1-hydroxybenzotriazole (HOBt) in DMF. The peptide (3) labelled with the phenanthrenylindole moiety was obtained in 31% yield.The photophysical properties of the phenanthrenyl-indole derivatives were studied in several solvents of different polarity. Compounds 1 and 2 have reasonably high fluorescence quantum yields (between 27% and 85%) in non-protic solvents, the methyl phenanthrenyl-indole-2-carboxylate 1 being the more fluorescent compound. The fluorescence emission of both compounds is sensitive to solvent, indicating that they are good candidates for fluorescent probes. Fluorescence emission measurements of the labelled peptide in solution showed a strong decrease of ΦF value caused by the attachment of the Gly-Gly-Arg-Gly-Asp-Gly chain.The phenanthrenyl-indoles 1 and 2 and the labelled peptide 3 were incorporated in liposomes of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG) and mixtures of both lipids. Steady-state anisotropy measurements showed that compounds 1 and 2 are located inside the lipid bilayers and are able to report the transition between the gel and liquid-crystalline phases. The RGD labelled peptide locates mainly in the outer part of the vesicle interface. These results indicate that the phenanthrenyl-indole moiety may be used as a fluorescent probe for peptides and lipid membranes.
    Journal of Photochemistry and Photobiology A-chemistry - J PHOTOCHEM PHOTOBIOL A-CHEM. 01/2011; 221(1):47-57.
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    ABSTRACT: Several β,β-disubstituted dehydroalanines were prepared from β,β-dibromo or β-bromo, β-substituted dehydroalanines and aryl boronic acids using a Suzuki–Miyaura cross-coupling reaction. The electrochemical behaviour of these compounds was studied by cyclic voltammetry. All compounds studied showed similar reduction potentials and these were similar to the peak potential of the methyl ester of N-tert-butoxycarbonyl dehydrophenylalanine. Thus, the presence of a second aryl moiety in the dehydroalanine scaffold does not significantly change the reduction potential.Controlled potential electrolyses were performed at the cathodic peak potential in the presence of triethylammonium chloride as proton donor. The only products isolated in good to high yields were the corresponding β,β-diarylalanines. This reaction was also carried out using a dipeptide containing a β,β-diaryldehydroalanine to give a 1:1 diastereomeric mixture of the reduction product.The photophysical properties of two of the β,β-diaryldehydroalanines and of the corresponding β,β-diarylalanines were studied in three solvents of different polarity. The β,β-diaryldehydroalanines show low fluorescent quantum yields (ΦF
    Tetrahedron. 01/2011; 67(1):193-200.
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    ABSTRACT: Fluorescence properties of four new potential antitumoral compounds, 3-arylbenzothieno[2,3-c]pyran-1-ones, were studied in solution and in lipid membranes of dipalmitoyl phosphatidylcholine (DPPC), egg yolk phosphatidylcholine (Egg-PC) and dioctadecyldimethylammonium bromide (DODAB). The 3-(4-methoxyphenyl)benzothieno[2,3-c]pyran-1-one (1c) exhibits the higher fluorescence quantum yields in all solvents studied. All compounds present a solvent sensitive emission, with significant red shifts in polar solvents for the methoxylated compounds. The results point to an ICT character of the excited state, more pronounced for compound 1c. Fluorescence (steady-state) anisotropy measurements of the compounds incorporated in liposomes of DPPC, DODAB and Egg-PC indicate that all compounds have two different locations, one due to a deep penetration in the lipid membrane and another corresponding to a more hydrated environment. In general, the methoxylated compounds prefer hydrated environments inside the liposomes. The 3-(4-fluorophenyl)benzothieno[2,3-c]pyran-1-one (1a) clearly prefers a hydrated environment, with some molecules located at the outer part of the liposome interface. On the contrary, the preferential location of 3-(2-fluorophenyl)benzothieno[2,3-c]pyran-1-one (1b) is in the region of lipid hydrophobic tails. Compounds with a planar geometry (1a and 1c) have higher mobility in the lipid membranes when phase transition occurs.
    Journal of Fluorescence 03/2010; 21(3):911-22. · 1.79 Impact Factor
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    ABSTRACT: This paper describes the design of a miniature, cost-effective spectroscopy system for assessing tissue biochemical and morphological information using a few wavelengths. This instrument will integrate thin-film optical filters and silicon photodiodes, avoiding the use of a spectrograph and optical fibers. The components in the set-up design are described. The feasibility of using only 16 wavelengths to accurately extract tissue properties is confirmed on physical tissue models. Also, the suitable spectral performance of several optical filters for the selection of these wavelengths is demonstrated. The reduced size of this device will make possible its implementation in an endoscopic capsule.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:1210-3.
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    ABSTRACT: Several 2,5-disubstituted oxazole-4-carboxylates were prepared in high yields from the methyl esters of N-acyl-β-halodehydroaminobutyric acid derivatives by treatment with a 2% solution of DBU in acetonitrile. The scope of this reaction was investigated and it was found that dehydrodipeptides having a β-bromodehydroaminobutyric acid residue gave the corresponding oxazoles in good yields. The photophysical properties of some of the oxazoles prepared were studied in four solvents of different polarity. All compounds have reasonable high fluorescence quantum yields and a moderate solvent sensitivity, which makes them good candidates to be used as fluorescent probes. One of the fluorescent oxazoles prepared was inserted after cleavage of the methyl ester into two model peptides using a conventional solution phase strategy. The photophysical properties of the labelled peptides were studied in ethanol and water and compared with those of the oxazole. The results obtained showed that the oxazole maintains a good fluorescence level and the same solvent sensitivity when linked to a peptide chain.
    Tetrahedron. 01/2010; 66(45):8672-8680.
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    Goreti Pereira, Elisabete M. S. Castanheira, Paula M. T. Ferreira
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    ABSTRACT: Several new indole derivatives were synthesised from β-brominated dehydroamino acids and arylboronic acids by using a strategy developed in our research group that involves a sequential Suzuki–Miyaura cross-coupling reaction and a metal-assisted C–N intramolecular cyclisation. The cyclised products were obtained either by direct cyclisation or by isomerisation followed by cyclisation. The photophysical properties of these compounds were studied in four solvents of different polarity (cyclohexane, diethyl ether, acetonitrile and ethanol). All these compounds have reasonably high fluorescence quantum yields (between 16 and 85 %) and show different solvent sensitivity in their fluorescence emission. These results indicate that the indole derivatives prepared are good candidates for fluorescent probes. The response of the new synthesised compounds towards fluoride ion (F–) was evaluated. It was found that methyl 3-methyl-1H-dibenzo[e,g]indole-2-carboxylate, methyl 3-(phenanthren-9-yl)-1H-dibenzo[e,g]indole-2-carboxylate and methyl 1-(naphthalen-1-yl)-3H-benzo[e]indole-2-carboxylate showed significant spectral changes in fluorescence emission upon F– addition with a decrease in intensity and the appearance of a new band at longer wavelengths. No detectable emission spectral changes were observed when several other anions were added to these compounds, which indicates their selectivity towards F–.
    Annalen der Chemie und Pharmacie 01/2010; 2010(3):464-475. · 3.10 Impact Factor
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    ABSTRACT: Two pyrenyl-dehydroamino acid derivatives were cyclized by a metal-assisted C–N intramolecular cyclization developed in our research group, to give a pyrenylindole and a phenalenoindole. The pyrenylindole was inserted into a peptide by solid-phase coupling, with use of a 2-chlorotrityl chloride resin and a Fmoc strategy. The photophysical properties of the pyrenylindole and phenalenoindole in several solvents were studied and showed that these compounds can be used as fluorescence probes. The results obtained with the peptide labelled with the pyrenylindole moiety show potential for use of this compound as a fluorescence label avoiding the aggregation propensity of pyrene compounds. Photophysical studies of the pyrenylindole and of the phenalenoindole in lipid membranes were also carried out. Steady-state fluorescence anisotropy measurements revealed that both compounds adopt locations inside the lipid bilayers and are able to report the transition between the gel and liquid-crystalline phases. The results point to potential use of these compounds as fluorescent probes for biological systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Annalen der Chemie und Pharmacie 06/2009; 2009(23):3906 - 3916. · 3.10 Impact Factor
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    ABSTRACT: To evaluate the influence of wear of silicone-hydrogel contact lenses on lens ultraviolet and visible spectrum transmittance by studying several contact lenses before and after wear. To investigate the ability of contact lenses to maintain their transmittance characteristics, we measured 104 different contact lenses in the ultraviolet (UV) and visible range from 200 to 700 nm, with a Shimadzu UV3101-PC UV-vis-NIR spectrophotometer equipped with an integrating sphere. The lenses used in this study were Acuvue Advance (Johnson & Johnson Vision Care, Inc.), Air Optix Night & Day (CIBA Vision), Air Optix (CIBA Vision), and PureVision (Bausch & Lomb). A conventional hydrogel contact lens was also tested, Acuvue (Johnson & Johnson Vision Care Inc.). Our study indicates that lenses that do not have UV absorbers incorporated into the polymer transmitted most of the UV radiation (UVR) before and after wear. The results of the statistical analysis show that for the UVC portion of the spectrum significant difference exists within the measurements obtained before and after wear for all the lenses, with the exception of PureVision. Acuvue Advance is the only material in which significant transmittance differences were observed in the visible spectral range. Transmittance is modified after contact lenses wear, probably due to the formation of biofilms on the contact lens surface, being more noticeable in the UVR region of the spectrum (200-400 nm). Silicone-hydrogel and conventional hydrogel contact lens materials that provide UVR protection (UV-blocker) maintain this property even after being worn. The changes observed in the visible spectrum seem not to have any implications in visual performance of silicone-hydrogel contact lenses.
    Optometry and vision science: official publication of the American Academy of Optometry 05/2009; 86(4):332-9. · 1.53 Impact Factor
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    ABSTRACT: Fluorescence properties of the antitumoral methyl 3-(benzo[b]thien-2-yl)-benzothieno[3,2-b]pyrrole-2-carboxylate (BTP) were studied in solution and in lipid bilayers of dipalmitoyl phosphatidylcholine (DPPC), dioleoyl phosphatidylethanolamine (DOPE) and egg yolk phosphatidylcholine (Egg-PC). BTP presents good fluorescence quantum yields in all solvents studied (0.20 ≤ ΦF ≤ 0.32) and a bathochromic shift in polar solvents. The results indicate an ICT character of the excited state, with an estimated dipole moment of μe = 7.38 D.Fluorescence (steady-state) anisotropy measurements of BTP incorporated in lipid membranes of DPPC, DOPE and Egg-PC indicate that this compound is deeply located in the lipid bilayer, feeling the difference between the rigid gel phase and fluid phases.BTP inhibits the growth of three human tumour cell lines, MCF-7 (breast adenocarcinoma), SF-268 (glioma) and NCI-H460 (non-small cell lung cancer), being significantly more potent against the NCI-H460 tumour cells.
    Journal of Photochemistry and Photobiology A: Chemistry. 01/2009;