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1.
Angew Chem Int Ed Engl ; 58(16): 5302-5306, 2019 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-30786135

RESUMO

We describe the preparation of the first water-soluble pH-responsive supramolecular hexagonal boxes (SHBs) based on multiple charge-assisted hydrogen bonds between peramino-pillar[6]arenes 2 with the molecular "lid" mellitic acid (1 a). The interaction between 2 and 1 a, as well as the other "lids" pyromellitic and trimesic acids (1 b and 1 c, respecively) were studied by a combination of experimental and computational methods. Interestingly, the addition of 1 a to the complexes of the protonated form of pillar[6]arene 2, that is, 3, with bis-sulfonate 4 a or 4 b, immediately led to guest escape along with the formation of closed 1 a2 2 supramolecular boxes. Moreover, the process of the openning and closing of the supramolecular boxes along with threading and escaping of the guests, respectively, was found to be reversible and pH-responsive. This study paves the way for the easy and modular preparation of different SHBs that may have myriad applications.

2.
Materials (Basel) ; 11(11)2018 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-30380643

RESUMO

Epoxy resins have a wide range of applications, including in corrosion protection of metals, electronics, structural adhesives, and composites. The consumption of epoxy resins is predicted to keep growing in the coming years. Unfortunately, thermoset resins cannot be recycled, and are typically not biodegradable. Hence, they pose environmental pollution risk. Here, we report degradation of epoxy resin by two bacteria that are capable of using epoxy resin as a sole carbon source. These bacteria were isolated from soil samples collected from areas around an epoxy and polyurethanes manufacturing plant. Using an array of molecular, biochemical, analytical, and microscopic techniques, they were identified as Rhodococcus rhodochrous and Ochrobactrum anthropi. As epoxy was the only carbon source available for these bacteria, their measured growth rate reflected their ability to degrade epoxy resin. Bacterial growth took place only when the two bacteria were grown together, indicating a synergistic effect. The surface morphology of the epoxy droplets changed significantly due to the biodegradation process. The metabolic pathway of epoxy by these two microbes was investigated by liquid chromatography mass spectrometry. Bisphenol A, 3,3'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(propane-1,2-diol) and some other constituents were identified as being consumed by the bacteria.

3.
Psychophysiology ; 55(11): e13215, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30094856

RESUMO

Saccades constitute a major source of artifacts and confounds in brain imaging studies. Whereas some artifacts can be removed by omitting segments of data, saccadic artifacts cannot be typically eliminated by this method because of their high occurrence rate even during fixation (1-3 per second). Some saccadic artifacts can be alleviated by offline-correction algorithms, but these methods leave nonnegligible residuals and cannot mitigate the saccade-related visual activity. Here, we propose a novel yet simple approach for diminishing saccadic artifacts and confounds through experimental design. We suggest that specific tasks can lead to substantially less saccade occurrences around the time of stimulus presentation, starting from slightly before its onset and lasting for a few hundred milliseconds. In three experiments, we compared the frequency and size of saccades in a variety of tasks. Results of Experiment 1 showed that a foveal change-detection task reduced the number and sizes of saccades, relative to a parafoveal orientation-discrimination task. Experiment 2 replicated this finding with a parafoveal object recognition task. Experiment 3 showed that both foveal and parafoveal continuous change detection tasks induced fewer and smaller saccades than a discrete orientation-discrimination task. We conclude that adding a foveal or a parafoveal continuous task reduces saccades' number and size. This would lead to better artifact correction and enable the omission of contaminated data segments. This study may be the first step toward developing saccade-free experimental designs.


Assuntos
Artefatos , Eletroencefalografia/normas , Medições dos Movimentos Oculares/normas , Fóvea Central/fisiologia , Neuroimagem/normas , Projetos de Pesquisa/normas , Movimentos Sacádicos/fisiologia , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
5.
Biochem J ; 473(23): 4413-4426, 2016 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-27647935

RESUMO

Ornidazole of the 5-nitroimidazole drug family is used to treat protozoan and anaerobic bacterial infections via a mechanism that involves preactivation by reduction of the nitro group, and production of toxic derivatives and radicals. Metronidazole, another drug family member, has been suggested to affect photosynthesis by draining electrons from the electron carrier ferredoxin, thus inhibiting NADP+ reduction and stimulating radical and peroxide production. Here we show, however, that ornidazole inhibits photosynthesis via a different mechanism. While having a minute effect on the photosynthetic electron transport and oxygen photoreduction, ornidazole hinders the activity of two Calvin cycle enzymes, triose-phosphate isomerase (TPI) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Modeling of ornidazole's interaction with ferredoxin of the protozoan Trichomonas suggests efficient electron tunneling from the iron-sulfur cluster to the nitro group of the drug. A similar docking site of ornidazole at the plant-type ferredoxin does not exist, and the best simulated alternative does not support such efficient tunneling. Notably, TPI was inhibited by ornidazole in the dark or when electron transport was blocked by dichloromethyl diphenylurea, indicating that this inhibition was unrelated to the electron transport machinery. Although TPI and GAPDH isoenzymes are involved in glycolysis and gluconeogenesis, ornidazole's effect on respiration of photoautotrophs is moderate, thus raising its value as an efficient inhibitor of photosynthesis. The scarcity of Calvin cycle inhibitors capable of penetrating cell membranes emphasizes on the value of ornidazole for studying the regulation of this cycle.


Assuntos
Bactérias Anaeróbias/efeitos dos fármacos , Ornidazol/farmacologia , Fotossíntese/efeitos dos fármacos , Cianobactérias/efeitos dos fármacos , Ferredoxinas/metabolismo , Gliceraldeído-3-Fosfato Desidrogenase (Fosforiladora)/metabolismo , Gliceraldeído-3-Fosfato Desidrogenases/metabolismo , Glicólise , Metronidazol/farmacologia , Modelos Biológicos , Synechocystis/efeitos dos fármacos , Trichomonas/efeitos dos fármacos , Trichomonas/metabolismo , Triose-Fosfato Isomerase/metabolismo
6.
J Biomed Mater Res B Appl Biomater ; 91(2): 819-30, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19582851

RESUMO

Drug-eluting stents (DES) have become an accepted technology in intravascular intervention. Manufacturing methodologies of DES are based mainly on mechanical processes, which tend to generate coatings that have poor stability properties; these were recently related as a potential hazard. A novel approach for significantly increasing the adhesion of polymer coatings onto DES is presented. The method is based on the electrochemistry of diazonium salts. These substances are organic compounds with the characteristic structure of R-N(2) (+) X(-), where R is an organic residue and X(-) is an anion. The objective of this article is to study the properties of a selected diazonium salt 4-(1-dodecyloxy)-phenyldiazonium tetrafluoroborate, referred as C(12)-phenyldiazonium. This material was found to be a superior adhesive promoter for polymeric coatings applied onto metallic stents. C(12)-phenyldiazonium was synthesized and electrocoated on metallic stents and plates. The multilayer films of C(12)-phenyldiazonium were further characterized through electrochemical (cyclic voltammetry, impedance spectroscopy), physical (light and scanning electron microscopy, X-ray photoelectron spectroscopy, peeling tests), and chemical methodology (high pressure liquid chromatography). Further biocompatibility properties of the electrocoated basecoat were evaluated using in vitro and in vivo models. Synthesized C(12)-phenyldiazonium was successfully electrocoated onto metallic surfaces. Electrochemical tests demonstrated its efficient and controllable electrocoating. C(12)-phenyldiazonium was found to increase polymeric coating stability as was reflected by a standard adhesion test. Electrocoated metallic stents spray-coated with a second polymeric film showed improved durability following incubation in physiological buffer. Furthermore, this improvement in durability exhibits stabilized drug release. In addition, biocompatibility evaluations have demonstrated basecoat's inert properties.


Assuntos
Materiais Revestidos Biocompatíveis , Stents Farmacológicos , Adesividade , Angioplastia com Balão , Animais , Antineoplásicos Fitogênicos/administração & dosagem , Antineoplásicos Fitogênicos/química , Derivados de Benzeno/química , Vasos Sanguíneos/crescimento & desenvolvimento , Vasos Sanguíneos/ultraestrutura , Adesão Celular , Sobrevivência Celular/efeitos dos fármacos , Compostos de Diazônio/química , Impedância Elétrica , Eletroquímica , Fulerenos/química , Hemólise/efeitos dos fármacos , Técnicas In Vitro , Teste de Materiais , Metais/química , Microscopia Eletrônica de Varredura , Paclitaxel/administração & dosagem , Paclitaxel/química , Polímeros , Coelhos , Espectrometria por Raios X
7.
ACS Appl Mater Interfaces ; 1(4): 758-67, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20356000

RESUMO

The coating of medical implants by polymeric films aims at increasing their biocompatibility as well as providing a durable matrix for the controlled release of a drug. In many cases, the coating is divided into a primer layer, which bridges between the medical implant and the drug-eluting matrix. The primer coating must be very carefully designed in order to provide optimal interactions with the surface of the medical implant and the outer layer. Here we present a simple and versatile approach for designing the primer layer based on electropolymerization of a carefully chosen blend of three different pyrrole derivatives: N-methylpyrrole (N-me), N-(2-carboxyethyl)pyrrole (PPA), and the butyl ester of N-(2-carboxyethyl)pyrrole (BuOPy). The composition and physical properties of the primer layer were studied in detail by atomic force microscopy (AFM) and a nano scratch tester. The latter provides the in-depth analysis of the adhesion and viscoelasticity of the coating. AFM phase imaging reveals a uniform distribution of the three monomers forming rough morphology. This primer layer significantly improved the morphology, stability, and paclitaxel release profile of a paclitaxel-eluting matrix based on methyl and lauryl methacrylates.


Assuntos
Prótese Vascular , Materiais Revestidos Biocompatíveis/química , Stents Farmacológicos , Paclitaxel/administração & dosagem , Paclitaxel/química , Polímeros/química , Pirróis/química , Absorção , Eletroquímica/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Dureza , Teste de Materiais , Propriedades de Superfície
8.
ACS Appl Mater Interfaces ; 1(11): 2519-28, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20356122

RESUMO

Drug-eluting stents (DESs) have been associated with adverse clinical effects. Moreover, recent publications have shown that the coating of DESs suffers from defects. The purpose of this contribution is to examine a three-step process for surface modification as a means of improving the durability of DESs. In the first step, 4-(2-bromoethyl)benzenediazonium tetrafluoroborate was electrografted onto a stainless steel (SS) stent. X-ray photoelectron spectroscopy (XPS) of the modified stent confirmed the formation of the organic layer. In the second step, methyl methacrylate was polymerized onto the grafted surface by atom-transfer radical polymerization. XPS, electrochemical impedance spectroscopy, and contact-angle measurements were used to characterize the polymer brushes. The last step involved spray-coating of the stent with a drug-in-polymer matrix [poly(n-butyl methacrylate)/poly(ethylene-co-vinyl acetate) + paclitaxel]. Scanning electron microscopy confirmed the considerably improved durability of the drug-in-polymer matrix. Bare controls showed greater cracking and delamination of the coating than did the two-step modified stents after incubation under physiological (37 degrees C) and accelerated (60 degrees C) conditions. Finally, paclitaxel controlled release from the modified SS DESs was moderate compared with that of nontreated samples. In conclusion, the proposed method significantly improves the durability of drug-in-polymer matrixes on a SS DESs.


Assuntos
Stents Farmacológicos , Paclitaxel/farmacologia , Polimetil Metacrilato/química , Aço Inoxidável/química , Boratos , Ácidos Bóricos/química , Tampões (Química) , Preparações de Ação Retardada/farmacologia , Técnicas Eletroquímicas , Microscopia Eletrônica de Varredura , Peso Molecular , Espectroscopia Fotoeletrônica , Propriedades de Superfície/efeitos dos fármacos , Água/química
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