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1.
Int J Mol Sci ; 22(19)2021 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-34638662

RESUMO

The protection of metals from atmospheric corrosion is a task of primary importance for many applications and many different products have been used, sometimes being toxic and harmful for health and the environment. In order to overcome drawbacks due to toxicity of the corrosion inhibitors and harmful organic solvents and to ensure long-lasting protection, new organic compounds have been proposed and their corrosion inhibition properties have been investigated. In this work, we describe the use of a new environment-friendly anticorrosive coating that takes advantage of the synergism between an eco-friendly bio-polymer matrix and an amino acid. The corrosion inhibition of a largely used Copper-based (Cu-based) alloy against the chloride-induced indoor atmospheric attack was studied using chitosan (CH) as a biopolymer and l-Cysteine (Cy) as an amino acid. To evaluate the protective efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated Cu-based alloys, further, the nature of the protective film formed on the Cu-based alloy surface was analyzed by Fourier-transformed infrared spectroscopy (FTIR) while the surface modifications due to the corrosion treatments were investigated by optical microscopy (OM). The evaluation tests reveal that the Chitosan/l-Cysteine (CH/Cy) coatings exhibit good anti-corrosion properties against chloride attack whose efficiency increases with a minimum amount of Cy of 0.25 mg/mL.

2.
Int J Mol Sci ; 22(13)2021 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-34201893

RESUMO

Lynch syndrome is a hereditary cancer-predisposing syndrome caused by germline defects in DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2. Carriers of pathogenic mutations in these genes have an increased lifetime risk of developing colorectal cancer (CRC) and other malignancies. Despite intensive surveillance, Lynch patients typically develop CRC after 10 years of follow-up, regardless of the screening interval. Recently, three different molecular models of colorectal carcinogenesis were identified in Lynch patients based on when MMR deficiency is acquired. In the first pathway, adenoma formation occurs in an MMR-proficient background, and carcinogenesis is characterized by APC and/or KRAS mutation and IGF2, NEUROG1, CDK2A, and/or CRABP1 hypermethylation. In the second pathway, deficiency in the MMR pathway is an early event arising in macroscopically normal gut surface before adenoma formation. In the third pathway, which is associated with mutations in CTNNB1 and/or TP53, the adenoma step is skipped, with fast and invasive tumor growth occurring in an MMR-deficient context. Here, we describe the association between molecular and histological features in these three routes of colorectal carcinogenesis in Lynch patients. The findings summarized in this review may guide the use of individualized surveillance guidelines based on a patient's carcinogenesis subtype.


Assuntos
Neoplasias Colorretais Hereditárias sem Polipose/genética , Carcinogênese/genética , Neoplasias Colorretais Hereditárias sem Polipose/etiologia , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Reparo de Erro de Pareamento de DNA/genética , Feminino , Predisposição Genética para Doença , Mutação em Linhagem Germinativa , Humanos , Masculino , Modelos Biológicos , Fenótipo , Fatores de Risco
3.
Cell Death Dis ; 12(4): 316, 2021 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-33767160

RESUMO

The prognosis of locally advanced colorectal cancer (CRC) is currently unsatisfactory. This is mainly due to drug resistance, recurrence, and subsequent metastatic dissemination, which are sustained by the cancer stem cell (CSC) population. The main driver of the CSC gene expression program is Wnt signaling, and previous reports indicate that Wnt3a can activate p38 MAPK. Besides, p38 was shown to feed into the canonical Wnt/ß-catenin pathway. Here we show that patient-derived locally advanced CRC stem cells (CRC-SCs) are characterized by increased expression of p38α and are "addicted" to its kinase activity. Of note, we found that stage III CRC patients with high p38α levels display reduced disease-free and progression-free survival. Extensive molecular analysis in patient-derived CRC-SC tumorspheres and APCMin/+ mice intestinal organoids revealed that p38α acts as a ß-catenin chromatin-associated kinase required for the regulation of a signaling platform involved in tumor proliferation, metastatic dissemination, and chemoresistance in these CRC model systems. In particular, the p38α kinase inhibitor ralimetinib, which has already entered clinical trials, promoted sensitization of patient-derived CRC-SCs to chemotherapeutic agents commonly used for CRC treatment and showed a synthetic lethality effect when used in combination with the MEK1 inhibitor trametinib. Taken together, these results suggest that p38α may be targeted in CSCs to devise new personalized CRC treatment strategies.


Assuntos
Cromatina/metabolismo , Neoplasias Colorretais/tratamento farmacológico , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Células-Tronco Neoplásicas/metabolismo , Organoides/metabolismo , Processamento de Proteína Pós-Traducional/genética , beta Catenina/metabolismo , Neoplasias Colorretais/genética , Humanos , Prognóstico
4.
Front Chem ; 8: 304, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32411661

RESUMO

The aim of this study was to develop smart materials with stimuli-responsive properties for the long-term protection of steel. The idea was to obtain a tailored and controlled release of protective agents in response to the environment stimuli. First, the protective efficacy of three inhibitors containing a carboxylic moiety, such as p-aminobenzoic (pAB), succinic (SA), and caffeic (CA) acids, was investigated in alkaline chloride solutions. The results revealed that pAB is the most effective protective agent, significantly better than SA and CA. It is surprising that the steel surface in the pAB solution remains unchanged even after 5 months of corrosion treatment, whereas the formation of degradation products in the SA and CA solutions was observed after only 6 days. Based on these findings, pAB was selected and used for the functionalization of silica nanoparticles and layered double hydroxides (LDHs) that can act as delivery vehicles and as an inhibitor reservoir. Specifically, pAB was chemisorbed on silica amino groups via an amide bond, and this makes possible a gradual inhibitor release induced by an alkaline environment. The intercalation of pAB in its anionic form into the LDHs structure is responsible for a completely different behavior since the release is induced by chloride ions and occurs by an anionic exchange reaction. Thus, these materials play a dual role by acting as an inhibitor reservoir and by capturing chlorides. These findings reveal that it is possible to create a reservoir of corrosion inhibitors gradually released on demand based on the chemical environment. The stimuli-responsive properties and the complementary protective action of inhibitor-loaded silica and LDHs make them attractive for the long-term protection of steel and open the way for innovative solutions in the preservation of concrete cultural heritage.

5.
Front Chem ; 8: 175, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32232028

RESUMO

When investigating gilded artifacts or works of art, the determination of the gilding thickness plays a significant role in establishing restoration protocols or conservation strategies. Unfortunately, this is done by cross-sectioning the object, a destructive approach not always feasible. A non-destructive alternative, based on the differential attenuation of fluorescence radiation from the sample, has been developed in the past years, but due to the intrinsic random nature of X-rays, the study of single or few spots of an objects surface may yield biased information. Furthermore, considering the effects of both porosity and sample inhomogeneities is a practice commonly overlooked, which may introduce systematic errors. In order to overcome these matters, here we propose the extrapolation of the differential-attenuation method from single-spot X-ray fluorescence (XRF) measurements to macro-XRF (MA-XRF) scanning. In this work, an innovative algorithm was developed for evaluating the large amount of data coming from MA-XRF datasets and evaluate the thickness of a given overlapping layer over an area. This approach was adopted to study a gilded copper-based buckle from the sixteenth to seventeenth century found in Rome. The gilded object under investigation was also studied by other analytical techniques including scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Previous results obtained from SEM-EDS were used to confront the data obtained with the proposed methodology and validate it. MA-XRF elemental distribution maps were fundamental in identifying and choosing sampling areas to calculate the thickness of the gilding layer, avoiding lead islands present in the sample that could negatively influence the results. Albeit the large relative standard deviation, the mean thickness values fell within those found in literature and those obtained from previous studies with SEM-EDS. Surface fissure has been found to deeply affect the results obtained, an aspect that is often disregarded.

6.
ACS Omega ; 4(6): 11103-11111, 2019 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-31460208

RESUMO

The long-term interaction between Cu-based alloys and environmental species gives rise to the formation of different and sometimes unusual compounds (i.e., the patina) with distinctive chemical and structural features as a function of the peculiar characteristics of the context. In this paper, we describe some representative case studies concerning degraded bronze Roman valuable or common use objects, and we show that an attentive study at a microscale level, as for forensic analysis, allows one to understand the chemical processes that underlie the formation of the surface alteration products. The achieved information describe fragments of chemical life and disclose the complex chemical changes suffered by the artifacts, allowing one to write their chemical biography. This challenging approach expands the panorama of available information and demonstrates that it is possible to reconstruct the different modes through which the bronze surfaces and interfaces have interacted with environmental species, organic matter, and microorganisms, opening up a new possibility to describe complex environmental chemical stories, in certain cases interrelated.

7.
Angew Chem Int Ed Engl ; 57(25): 7380-7384, 2018 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-29663606

RESUMO

The photodegradation kinetics of 2-mercaptobenzothiazole (MBT), a corrosion inhibitor for copper-based alloys, is studied in high amorphous polyvinyl alcohol coatings subjected to either UV irradiation or indoor light exposure. The photodegradation process proceeds rapidly, thus compromising the anticorrosion ability of the coating. The encapsulation of MBT into layered double hydroxide (LDH) nanocarriers slows down its decomposition kinetics by a factor of three. Besides preserving the corrosion inhibitor, such a strategy allows a controlled release of MBT triggered by corrosion-related stimuli, for example, presence of chloride species and acid pH. The developed coating guarantees long-lasting corrosion protection even at low amounts of inhibitor-loaded LDH nanocarriers (ca. 5 wt %). This also reflects in a high transparency, which makes the protective coating suitable for demanding applications, such as the conservation of high-value metal works of art.

8.
ACS Appl Mater Interfaces ; 8(35): 23244-59, 2016 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-27538099

RESUMO

Improving the electrical and thermal properties of conductive adhesives is essential for the fabrication of compact microelectronic and optoelectronic power devices. Here we report on the addition of a commercially available conductive resin with double-wall carbon nanotubes and graphene nanoplatelets that yields simultaneously improved thermal and electrical conductivity. Using isopropanol as a common solvent for the debundling of nanotubes, exfoliation of graphene, and dispersion of the carbon nanostructures in the epoxy resin, we obtain a nanostructured conducting adhesive with thermal conductivity of ∼12 W/mK and resistivity down to 30 µΩ cm at very small loadings (1% w/w for nanotubes and 0.01% w/w for graphene). The low filler content allows one to keep almost unchanged the glass-transition temperature, the viscosity, and the curing parameters. Die shear measurements show that the nanostructured resins fulfill the MIL-STD-883 requirements when bonding gold-metalized SMD components, even after repeated thermal cycling. The same procedure has been validated on a high-conductivity resin characterized by a higher viscosity, on which we have doubled the thermal conductivity and quadrupled the electrical conductivity. Graphene yields better performances with respect to nanotubes in terms of conductivity and filler quantity needed to improve the resin. We have finally applied the nanostructured resins to bond GaN-based high-electron-mobility transistors in power-amplifier circuits. We observe a decrease of the GaN peak and average temperatures of, respectively, ∼30 °C and ∼10 °C, with respect to the pristine resin. The obtained results are important for the fabrication of advanced packaging materials in power electronic and microwave applications and fit the technological roadmap for CNTs, graphene, and hybrid systems.

9.
Phys Chem Chem Phys ; 15(39): 16949-55, 2013 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-24002434

RESUMO

An engineered bi-layered photoelectrode for dye solar cells has been developed which profitably employs two synergistic meso-ordered components, namely a thin meso-ordered TiO2 film and a main microparticles-based photoelectrode. The former has been deposited as an interfacial layer at the FTO-coated substrate and suppresses the back-transport reaction by blocking direct contact between the electrolyte and conductive oxide. The latter is made of hierarchical micro- and nano-structured building blocks prepared by template synthesis, which permits efficient light scattering without sacrificing the internal surface area. The optimization of light harvesting and charge recombination dynamics allowed us to achieve as high energy conversion efficiency as 9.7%.


Assuntos
Energia Solar , Titânio/química , Microscopia Eletrônica de Varredura , Nanopartículas/química , Porosidade , Difração de Raios X
10.
Acc Chem Res ; 46(11): 2365-75, 2013 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-23829823

RESUMO

Fire gilding and silvering are age-old mercury-based processes used to coat thesurface of less precious substrates with thin layers of gold or silver. In ancient times, these methods were used to produce and decorate different types of artefacts, such as jewels, statues, amulets, and commonly-used objects. Gilders performed these processes not only to decorate objects but also to simulate the appearance of gold or silver, sometimes fraudulently. From a technological point of view, the aim of these workmen over 2000 years ago was to make the precious metal coatings as thin and adherent as possible. This was in order to save expensive metals and to improve the resistance to the wear caused by continued use and circulation. Without knowledge about the chemical-physical processes, the ancient crafts-men systematically manipulated these metals to create functional and decorative artistic objects. The mercury-based methods were also fraudulently used in ancient times to produce objects such as jewels and coins that looked like they were made of silver or gold but actually had a less precious core. These coins were minted by counterfeiters but also by the official issuing authorities. The latter was probably because of a lack of precious metals, reflecting periods of severe economic conditions. In this Account, we discuss some representative cases of gold- and silver-coatedobjects, focusing on unique and valuable Roman and Dark Ages period works of art, such as the St. Ambrogio's altar (825 AD), and commonly used objects. We carried out the investigations using surface analytical methods, such as selected area X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy-dispersive spectroscopy. We used these methods to investigate the surface and subsurface chemical features of these important examples of art and technology, interpreting some aspects of the manufacturing methods and of disclosing degradation agents and mechanisms. These findings may contribute to cultural heritage preservation, thus extending the applicability of the surface analytical techniques.

11.
Langmuir ; 28(12): 5471-9, 2012 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-22385276

RESUMO

In this work, colloidal gold nanoparticles (AuNPs) stabilized into a chitosan matrix were prepared using a green route. The synthesis was carried out by reducing Au(III) to Au(0) in an aqueous solution of chitosan and different organic acids (i.e., acetic, malonic, or oxalic acid). We have demonstrated that by varying the nature of the acid it is possible to tune the reduction rate of the gold precursor (HAuCl(4)) and to modify the morphology of the resulting metal nanoparticles. The use of chitosan, a biocompatible and biodegradable polymer with a large number of amino and hydroxyl functional groups, enables the simultaneous synthesis and surface modification of AuNPs in one pot. Because of the excellent film-forming capability of this polymer, AuNPs-chitosan solutions were used to obtain hybrid nanocomposite films that combine highly conductive AuNPs with a large number of organic functional groups. Herein, Au-chitosan nanocomposites are successfully proposed as sensitive and selective electrochemical sensors for the determination of caffeic acid, an antioxidant that has recently attracted much attention because of its benefits to human health. A linear response was obtained over a wide range of concentration from 5.00 × 10(-8) M to 2.00 × 10(-3) M, and the limit of detection (LOD) was estimated to be 2.50 × 10(-8) M. Moreover, further analyses have demonstrated that a high selectivity toward caffeic acid can be achieved without interference from catechin or ascorbic acid (flavonoid and nonphenolic antioxidants, respectively). This novel synthesis approach and the high performances of Au-chitosan hybrid materials in the determination of caffeic acid open up new routes in the design of highly efficient sensors, which are of great interest for the analysis of complex matrices such as wine, soft drinks, and fruit beverages.


Assuntos
Técnicas Biossensoriais , Ácidos Cafeicos/análise , Nanocompostos/química , Quitosana , Coloide de Ouro , Química Verde/métodos , Humanos , Nanopartículas Metálicas/química , Microscopia Eletrônica de Varredura , Ressonância de Plasmônio de Superfície
12.
Chem Commun (Camb) ; 46(34): 6317-9, 2010 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-20676428

RESUMO

The appropriate combination of titania and silica, sulfating and non-sulfating support, respectively, results in Pd catalysts with improved water and sulfur tolerance in methane combustion. For the first time the catalyst recovers the initial activity after one cycle under lean-burn conditions without additional regenerating treatments.


Assuntos
Metano/química , Paládio/química , Sulfatos/química , Enxofre/química , Água/química , Catálise , Dióxido de Silício/química , Temperatura , Titânio/química
13.
J Phys Chem B ; 109(7): 2821-7, 2005 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-16851293

RESUMO

Gold catalysts supported on cerium oxide were prepared by solvated metal atom dispersion (SMAD), by deposition-precipitation (DP), and by coprecipitation (CP) methods and were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The catalytic activity was tested in the CO oxidation reaction. The structural and surface analyses evidenced the presence of a modified ceria phase in the case of the DP sample and the presence of pure ceria and gold metal crystallites in the case of the SMAD and CP samples. The DP sample, after a mild treatment in air at 393 K, exhibited only ionic gold, and it was very active below 273 K. By comparing the activities of the different catalysts, it is suggested that the presence of small gold particles, as obtained by the SMAD technique, is not the main requisite for the achievement of the highest CO conversion. The strong interaction between ionic gold and ceria, by enhancing the ceria surface oxygen reducibility, may determine the particularly high activity.

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