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1.
Molecules ; 24(3)2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30736414

RESUMO

Gelatin is a biopolymer with interesting properties that can be useful for biomaterial design for different applications such as drug delivery systems, or 3D scaffolds for tissue engineering. However, gelatin suffers from poor mechanical stability at physiological temperature, hence methods for improving its properties are highly desirable. In the present work, a new chemical cross-linking strategy based on triazolinedione ene-type chemistry towards stable hydrogel is proposed. Two different homobifunctional 1,2,4-triazoline-3,5(4H)-diones, namely 4,4'-hexane-1,6-diylbis(3H-1,2,4-triazoline-3,5(4H)-dione) 1 and 4,4'-[methylenebis(4,1-phenylene)]bis(3H-1,2,4-triazoline-3,5(4H)-dione) 2 were used as cross-linkers in different ratio to tyrosine residues in gelatin. The reaction was proved effective in all experimented conditions and hydrogels featured with different thermal stability were obtained. In general, the higher the cross-linker/tyrosine ratio, the more thermostable the hydrogel. The swelling properties are strictly dependent upon the chemical nature of the cross-linker.


Assuntos
Gelatina/química , Hidrogéis/química , Triazóis/química , Tirosina/química , Materiais Biocompatíveis/química , Estabilidade de Medicamentos , Teste de Materiais , Estrutura Molecular , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura
2.
Phys Chem Chem Phys ; 20(41): 26161-26172, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30311617

RESUMO

The structure and electronic properties of carbon-based nanostructures obtained by metal surface assisted synthesis is highly dependent on the nature of the precursor molecule. Here, we report on a combined scanning tunneling microscopy, soft X-ray spectroscopy and density functional theory investigation on the surface assisted polymerization of Br-corannulene at Ag(110) and on the possibility of building a mesh of π-conjugated polymers starting from buckyball shaped molecules. Indeed, the corannulene units form one-molecule-wide ribbons in which the natural concavity of the precursor molecule is maintained. These C-based nanostructures are corrugated and merge into a covalent network on the surface.

3.
Nanoscale ; 8(41): 17843-17853, 2016 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-27714142

RESUMO

By a combination of scanning tunneling microscopy, X-ray spectroscopic techniques and density functional theory calculations, we prove the formation of extended patterns of parallel, graphene nanoribbons with alternate zig-zag and armchair edges and selected width by surface-assisted Ullmann coupling polymerization and dehydrogenation of 1,6-dibromopyrene (C16H8Br2). Besides the relevance of these nanostructures for their possible application in nanodevices, we demonstrate the peculiarity of halogenated pyrene derivatives for the formation of nanoribbons, in particular on Ag(110). These results open the possibility of tuning the shape and dimension of nanoribbons (and hence the correlated electronic properties) by choosing suitably tailored or on-purpose designed molecular precursors.

4.
Chem Commun (Camb) ; 51(63): 12593-6, 2015 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-26154619

RESUMO

The surface-assisted synthesis of gold-organometallic hybrids on the Au(111) surface both by thermo- and light-initiated dehalogenation of bromo-substituted tetracene is reported. Combined X-ray photoemission (XPS) and scanning tunneling microscopy (STM) data reveal a significant increase of the surface order when mild reaction conditions are combined with 405 nm light irradiation.

5.
Chemistry ; 21(15): 5826-35, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25711882

RESUMO

Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions.

6.
Nat Commun ; 5: 4276, 2014 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-25008948

RESUMO

Phloem, a plant tissue responsible for long-distance molecular transport, harbours specific junctions, sieve areas, between the conducting cells. To date, little is known about the molecular framework related to the biogenesis of these sieve areas. Here we identify mutations at the CHER1/AtCTL1 locus of Arabidopsis thaliana. The mutations cause several phenotypic abnormalities, including reduced pore density and altered pore structure in the sieve areas associated with impaired phloem function. CHER1 encodes a member of a poorly characterized choline transporter-like protein family in plants and animals. We show that CHER1 facilitates choline transport, localizes to the trans-Golgi network, and during cytokinesis is associated with the phragmoplast. Consistent with its function in the elaboration of the sieve areas, CHER1 has a sustained, polar localization in the forming sieve plates. Our results indicate that the regulation of choline levels is crucial for phloem development and conductivity in plants.


Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/crescimento & desenvolvimento , Comunicação Celular/fisiologia , Glicosídeo Hidrolases/fisiologia , Floema/crescimento & desenvolvimento , Desenvolvimento Vegetal/fisiologia , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Comunicação Celular/genética , Polaridade Celular/genética , Polaridade Celular/fisiologia , Citocinese/genética , Citocinese/fisiologia , Glicosídeo Hidrolases/genética , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/fisiologia , Mutação/genética , Floema/genética , Floema/fisiologia , Desenvolvimento Vegetal/genética
7.
Langmuir ; 30(5): 1336-42, 2014 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-24443819

RESUMO

Despite the relevance of carbohydrates as cues in eliciting specific biological responses, the covalent surface modification of collagen-based matrices with small carbohydrate epitopes has been scarcely investigated. We report thereby the development of an efficient procedure for the chemoselective neoglycosylation of collagen matrices (patches) via a thiol-ene approach, between alkene-derived monosaccharides and the thiol-functionalized material surface. Synchrotron radiation-induced X-ray photoelectron spectroscopy (SR-XPS), Fourier transform-infrared (FT-IR), and enzyme-linked lectin assay (ELLA) confirmed the effectiveness of the collagen neoglycosylation. Preliminary biological evaluation in osteoarthritic models is reported. The proposed methodology can be extended to any thiolated surface for the development of smart biomaterials for innovative approaches in regenerative medicine.


Assuntos
Materiais Biocompatíveis/química , Carboidratos/química , Química Click , Colágeno/química , Compostos de Sulfidrila/química , Animais , Sequência de Carboidratos , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Glicosilação , Masculino , Estrutura Molecular , Osteoartrite/terapia , Espectroscopia Fotoeletrônica , Ratos , Ratos Wistar , Espectroscopia de Infravermelho com Transformada de Fourier
8.
Langmuir ; 27(19): 12008-15, 2011 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-21875110

RESUMO

The integration of nanoscale processes and devices demands fabrication routes involving rapid, cost-effective steps, preferably carried out under ambient conditions. The realization of the metal/organic semiconductor interface is one of the most demanding steps of device fabrication, since it requires mechanical and/or thermal treatments which increment costs and are often harmful in respect to the active layer. Here, we provide a microscopic analysis of a room temperature, electroless process aimed at the deposition of a nanostructured metallic silver layer with controlled coverage atop the surface of single crystals and thin films of organic semiconductors. This process relies on the reaction of aqueous AgF solutions with the nonwettable crystalline surface of donor-type organic semiconductors. It is observed that the formation of a uniform layer of silver nanoparticles can be accomplished within 20 min contact time. The electrical characterization of two-terminal devices performed before and after the aforementioned treatment shows that the metal deposition process is associated with a redox reaction causing the p-doping of the semiconductor.


Assuntos
Nanopartículas Metálicas/química , Prata/química , Membranas Artificiais , Tamanho da Partícula , Semicondutores , Propriedades de Superfície
9.
Chemphyschem ; 11(2): 429-34, 2010 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-20029880

RESUMO

Blue amplified spontaneous emission at room temperature is demonstrated from the exposed face of the strongly emitting organic semiconductor 1,1,4,4-tetraphenyl-1,3-butadiene in single crystal form. The symmetry of the crystal and calculation of lattice sums indicate the J-type organization of the molecular transition moments. The minimum in the lowest exciton dispersion branch, from which emission takes place, is found at the edge of the Brillouin zone leading to a dominant vibronic emission since the zero-phonon line is forbidden. The observed gain narrowed line is attributed to the vibronic replica which becomes amplified with increased pumping. The reported emission is along the normal to the exposed crystal face, important for the development of vertical cavity geometry lasers based on organic single crystals. The threshold excitation fluence of 400 microJ cm(-2) is comparable to other organic crystalline systems, even if the amplification path is much reduced as a consequence of the vertical geometry. Considering these relevant aspects, the optical characterization of this material is provided. The polarized absorption spectra are reported and the properties of the lowest-energy excitonic state investigated. Calculation of the electronic transitions for the isolated molecule, lattice sums for the transition at lowest energy, and the symmetry of the crystal allow attributing the largest face of the samples and the observed optical bands in the spectra. Polarized time-resolved spectra are also reported allowing to identify the intrinsic excitonic emission.

10.
Cont Lens Anterior Eye ; 32(3): 108-12, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19324586

RESUMO

Two experimental spectroscopic methods for the determination of the content of hyaluronic acid in solution are provided based on the formation of complexes between the hyaluronic acid and cationic dyes with sensitivity down to concentrations of either 0.25 or 2.5 microg/ml. These techniques were applied to commercial hydrophilic contact lenses and allowed (i) distinguishing among contact lenses either loaded or non-loaded with hyaluronic acid, (ii) determining, for the loaded ones, the content of hyaluronic acid, (iii) evaluating the release of hyaluronic acid by the lens in solution, and (iv) determining the role of the hyaluronic acid in preventing the adsorption and the successive release by the contact lens of other components which can be present, for example, in the conservation solutions and/or in the blisters of the lenses. The results represent new physical chemistry insights for the field of contact lenses with impact on the advancement of current technology.


Assuntos
Soluções para Lentes de Contato/química , Lentes de Contato Hidrofílicas , Ácido Hialurônico/análise , Ácido Hialurônico/química , Cloreto de Sódio/química , Água/química , Difusão , Interações Hidrofóbicas e Hidrofílicas , Espectrometria de Massas , Teste de Materiais , Soluções
11.
J Am Chem Soc ; 128(41): 13378-87, 2006 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-17031949

RESUMO

Hot-wall epitaxy and molecular-beam epitaxy have been employed for growing quaterthiophene thin films on the (010) cleavage face of potassium hydrogen phthalate, and the results are compared in terms of film properties and growth mode. Even if there is no geometrical match between substrate and overlayer lattices, these films are epitaxially oriented. To investigate the physical rationale for this strong orientation effect, optical microscopy, atomic force microscopy, and X-ray diffraction are employed. A clear correlation between the morphology of the thin films and the crystallographic orientation is found. The results are also validated by surface potential calculations, which demonstrate the primary role played by the corrugation of the substrate surface.

12.
Eur J Cancer ; 41(10): 1453-9, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15913986

RESUMO

In this study, we have shown the intracellular distribution of choline and phosphatidylcholine fluorescent derivatives in human breast carcinoma cells using confocal microscopy. The fluorescent choline derivatives ethanamimium 2-hydroxy-N,N-dimethyl-N-[2-N-(2,1,3-benzoxadiazol-4-amine,-N-methyl,-7- nitro)-ethyl] bromide (NBD-choline) and C(6)-NBD-phosphatidylcholine (C(6)-NBD-PC) were used in this work. NBD-choline was easily internalised into drug sensitive MCF-7 and in multidrug resistant MCF-7/DX cells. The probe was found to localise in the endoplasmic reticulum of sensitive cells and in the Golgi of multidrug resistant cells. In contrast, very low accumulation was found in normal MCF10A cells. For C(6)-NBD-PC, a similar pattern of localisation was found in tumour cells, but a significant uptake was also observed in normal cells. Unlike NBD-choline, C(6)-NBD-PC appears not to discriminate between normal and tumour cells. These results are consistent with previously published results showing higher levels of (11)C-choline uptake in malignant lesions seen with positron emission tomography (PET) in vivo imaging. Our results suggest that using NBD-choline and laser scanning confocal fluorescence microscopy (LSCFM) could be a useful tool to study choline metabolism in cancer cells and to consolidate PET imaging findings.


Assuntos
Neoplasias da Mama/metabolismo , Colina/metabolismo , Fosfatidilcolinas/análise , Neoplasias da Mama/química , Neoplasias da Mama/patologia , Colina/análogos & derivados , Feminino , Fluorescência , Humanos , Microscopia Confocal , Microscopia de Fluorescência , Tomografia por Emissão de Pósitrons , Células Tumorais Cultivadas
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