Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 9 de 9
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Am Chem Soc ; 142(3): 1518-1525, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31922404

RESUMO

An electrogenerated chemiluminescence (ECL) system by in situ coreactant production, where Ru(bpy)32+ emission is generated at a boron-doped diamond (BDD) electrode, is presented. The system takes advantage of the unique properties of BDD to promote oxidation of carbonate (CO32-) into peroxydicarbonate (C2O62-), which further reacts with water to form hydrogen peroxide (H2O2), which acts as a coreactant for Ru(bpy)32+ ECL. Investigation of the mechanism reveals that ECL emission is triggered by the reduction of H2O2 to hydroxyl radicals (OH•), which later react with the reduced Ru(bpy)3+ molecules to form excited states, followed by light emission. The ECL signal was found to increase with the concentration of CO32-; therefore, with the concentration of electrogenerated H2O2, although at the same time, higher concentrations of H2O2 can quench the ECL emission, resulting in a decrease in intensity. The carbonate concentration, pH, and oxidation parameters, such as potential and time, were optimized to find the best emission conditions.

2.
Anal Bioanal Chem ; 411(19): 4375-4382, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31020369

RESUMO

The use of electrochemiluminescence (ECL), i.e., chemiluminescence triggered by electrochemical stimulus, as emitting light source for microscopy is an emerging approach with different applications ranging from the visualization of nanomaterials to cell mapping. In this trend article, we give an overview of the state of the art in this new field with the purpose to illustrate all the possible applications so far explored as well as describing the mechanism underlying this transduction technique. The results discussed here would highlight the great potential of the combination between ECL and microscopy and how this marriage can turn into an innovative approach with specific application in analytical sciences. Graphical abstract.


Assuntos
Técnicas Eletroquímicas/métodos , Luminescência , Medições Luminescentes/métodos , Microscopia/métodos , Eletrodos , Nanoestruturas , Análise de Célula Única
3.
Anal Chem ; 90(21): 12959-12963, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30399650

RESUMO

We report on the use of boron doped diamond electrodes for the electrochemiluminescence (ECL) of the coreactant peroxydisulfate and the luminophore ruthenium(II)-tris(2,2'-bipyridine). Compared to common electrode materials (i.e., Pt, Au, glassy carbon), boron doped diamond has a large overpotential for the evolution of hydrogen in aqueous electrolyte solutions. This intrinsic feature enables reductive-oxidation ECL with peroxydisulfate to be obtained without interference from hydrogen evolution and with high reproducible signals and stable emission. We investigated the effects of the peroxydisulfate concentration and the pH on the ECL emission to find the optimal conditions for enhancing the signal.

4.
Chemistry ; 24(46): 11954-11960, 2018 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-29603481

RESUMO

Salophens and Salens are Schiff bases generated through the condensation of two equivalents of salicylaldehyde with either 1,2-phenylenediamines or aliphatic diamines, respectively. Both ligands have been extensively exploited as key building blocks in coordination chemistry and catalysis. In particular, their metal complexes have been widely used for various catalytical transformations with high yield and selectivity. Through the modification of the phenol unit it is possible to tune the steric hindrance and electronic properties of Salophen and Salen. The introduction of long aliphatic chains in salicylaldehydes can be used to promote their self-assembly into ordered supramolecular structures on solid surfaces. Herein, we report a novel method towards the facile synthesis of robust and air-stable [Al(Salophen)] derivatives capable of undergoing spontaneous self-assembly at the graphite/solution interface forming highly-ordered nanopatterns. The new synthetic approach relies on the use of [MeAlIII (Salophen)] as a building unit to introduce, via a simple acid/base reaction with functionalized acidic phenol derivatives, selected frameworks integrating multiple functions for efficient surface decoration. STM imaging at the solid/liquid interface made it possible to monitor the formation of ordered supramolecular structures. In addition, the redox properties of the Salophen derivatives functionalized with ferrocene units in solution and on surface were unraveled by cyclic voltammetry. The use of a five-coordinate aluminum alkyl Salophen precursor enables the tailoring of new Salophen molecules capable of undergoing controlled self-assembly on HOPG, and thereby it can be exploited to introduce multiple functionalities with subnanometer precision at surfaces, ultimately forming ordered functional patterns.

5.
Macromol Biosci ; 17(3)2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27754612

RESUMO

Oligo(Glu70 -co-Leu30 ), a peptide synthesized by protease catalysis, is functionalized at the N-terminus with a 4-pentenoyl unit and grafted to polyLSL[6'Ac,6″Ac], a glycopolymer prepared by ring-opening metathesis polymerization of lactonic sophorolipid diacetate. First, polyLSL[6'Ac,6"Ac] fiber mats are fabricated by electrospinning. Oxidation of the fiber mats and subsequent reaction with cysteamine lead to thiol-functionalized fiber mats with no significant morphology changes. Grafting of the alkene-modified oligopeptide to thiol-functionalized polyLSL[6'Ac,6″Ac] fiber mats is achieved via "thiol-ene" click reaction. X-ray photoelectron spectroscopy analysis to characterize peptide grafting reveals that about 50 mol% of polyLSL[6'Ac,6''Ac] repeat units at fiber surfaces are decorated with a peptide moiety, out of which about 1/3 of the oligo(Glu70 -co-Leu30 ) units are physically adsorbed to polyLSL[6'Ac,6''Ac]. The results of this work pave the way to precise engineering of polyLSL fiber mats that can be decorated with a potentially wide range of molecules that tailor surface chemistry and biological properties.


Assuntos
Materiais Biocompatíveis/química , Biopolímeros/química , Glicoproteínas/química , Peptídeos/química , Materiais Biocompatíveis/síntese química , Glicoproteínas/síntese química , Peptídeos/síntese química , Espectroscopia Fotoeletrônica , Propriedades de Superfície
6.
J Am Chem Soc ; 138(48): 15636-15641, 2016 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-27934028

RESUMO

A novel co-reactant-free electrogenerated chemiluminescence (ECL) system is developed where Ru(bpy)32+ emission is obtained on boron-doped diamond (BDD) electrodes. The method exploits the unique ability of BDD to operate at very high oxidation potential in aqueous solutions and to promote the conversion of inert SO42- into the reactive co-reactant S2O82-. This novel procedure is rather straightforward, not requiring any particular electrode geometry, and since the co-reactant is only generated in situ, the interference with biological samples is minimized. The underlying mechanism is similar to that of the Ru(bpy)32+/S2O82- system; however, the intensity of the emitted signal increases linearly with [SO42-] up to ∼0.6 M, with possible implications for analytical uses of the proposed procedure.

7.
Chemistry ; 21(7): 2936-47, 2015 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-25538028

RESUMO

The electrochemistry, photophysics, and electrochemically generated chemiluminescence (ECL) of a family of polysulfurated dendrimers with a pyrene core have been thoroughly investigated and complemented by theoretical calculations. The redox and luminescence properties of dendrimers are dependent on the generation number. From low to higher generation it is both easier to reduce and oxidize them and the emission efficiency increases along the family, with respect to the polysulfurated pyrene core. The analysis of such data evidences that the formation of the singlet excited state by cation-anion annihilation is an energy-deficient process and, thus, the ECL has been justified through the triplet-triplet annihilation pathway. The study of the dynamics of the ECL emission was achieved both experimentally and theoretically by molecular mechanics and quantum chemical calculations. It has allowed rationalization of a possible mechanism and the experimental dependence of the transient ECL on the dendrimer generation. The theoretically calculated Marcus electron-transfer rate constant compares very well with that obtained by the finite element simulation of the whole ECL mechanism. This highlights the role played by the thioether dendrons in modulating the redox and photophysical properties, responsible for the occurrence and dynamics of the electron transfer involved in the ECL. Thus, the combination of experimental and computational results allows understanding of the dendrimer size dependence of the ECL transient signal as a result of factors affecting the annihilation electron transfer.

8.
J Mater Sci Mater Med ; 25(10): 2313-21, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24664673

RESUMO

Collagen electrospun scaffolds well reproduce the structure of the extracellular matrix (ECM) of natural tissues by coupling high biomimetism of the biological material with the fibrous morphology of the protein. Structural properties of collagen electrospun fibers are still a debated subject and there are conflicting reports in the literature addressing the presence of ultrastructure of collagen in electrospun fibers. In this work collagen type I was successfully electrospun from two different solvents, trifluoroethanol (TFE) and dilute acetic acid (AcOH). Characterization of collagen fibers was performed by means of SEM, ATR-IR, Circular Dichroism and WAXD. We demonstrated that collagen fibers contained a very low amount of triple helix with respect to pristine collagen (18 and 16% in fibers electrospun from AcOH and TFE, respectively) and that triple helix denaturation occurred during polymer dissolution. Collagen scaffolds were crosslinked by using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), a commonly employed crosslinker for electrospun collagen, and 1,4-butanediol diglycidyl ether (BDDGE), that was tested for the first time in this work as crosslinking agent for collagen in the form of electrospun fibers. We demonstrated that BDDGE successfully crosslinked collagen and preserved at the same time the scaffold fibrous morphology, while scaffolds crosslinked with EDC completely lost their porous structure. Mesenchymal stem cell experiments demonstrated that collagen scaffolds crosslinked with BDDGE are biocompatible and support cell attachment.


Assuntos
Colágeno/química , Reagentes para Ligações Cruzadas/farmacologia , Nanofibras/química , Solventes/farmacologia , Tecidos Suporte , Animais , Materiais Biocompatíveis/química , Butileno Glicóis , Células Cultivadas , Colágeno/efeitos dos fármacos , Estabilidade de Medicamentos , Galvanoplastia/métodos , Matriz Extracelular/química , Teste de Materiais , Coelhos , Engenharia Tecidual/métodos , Tecidos Suporte/química
9.
Mater Sci Eng C Mater Biol Appl ; 36: 130-8, 2014 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-24433895

RESUMO

Bio-synthetic scaffolds of interspersed poly(l-lactic acid) (PLLA) and gelatin (GEL) fibers are fabricated by co-electrospinning. Tailored PLLA/GEL compositions are obtained and GEL crosslinking with genipin provides for the maintenance of good fiber morphology. Scaffold tensile mechanical properties are intermediate between those of pure PLLA and GEL and vary as a function of PLLA content. Primary human chondrocytes grown on the scaffolds exhibit good proliferation and increased values of the differentiation parameters, especially for intermediate PLLA/GEL compositions. Mineralization tests enable the deposition of a uniform layer of poorly crystalline apatite onto the scaffolds, suggesting potential applications involving cartilage as well as cartilage-bone interface tissue engineering.


Assuntos
Condrócitos/citologia , Gelatina/farmacologia , Ácido Láctico/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Polímeros/farmacologia , Engenharia Tecidual/métodos , Tecidos Suporte/química , Animais , Calcificação Fisiológica/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Forma Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Condrócitos/efeitos dos fármacos , Condrócitos/enzimologia , Condrócitos/ultraestrutura , Reagentes para Ligações Cruzadas/química , Humanos , L-Lactato Desidrogenase/metabolismo , Poliésteres , Espectroscopia de Infravermelho com Transformada de Fourier , Sus scrofa , Resistência à Tração/efeitos dos fármacos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA