Featured paper: Nanorods to develop new anti-inflammatory drugs.

[Paper: Characterization of the structural, optical, photocatalytic and in vitro and in vivo anti-inflammatory properties of Mn2+ doped Zn2GeO4 nanorods. Suzuki, V. Y.; Amorin, L. H. C; Lima, N. M; Machado, E. G; Carvalho, P. E.; Castro, S. B. R.; Souza Alves, C. C.; Carli, A. P.; Li, Maximo Siu; Longo, Elson; Felipe La Porta. J. Mater. Chem. C, 2019, 7, 8216. DOI: 10.1039/c9tc01189g]

nanobastoesA team of researchers from Brazilian universities found, in cylindrical nanostructures known as nanorods, an anti-inflammatory effect equivalent to that achieved by commercial drugs. Researchers have also demonstrated the effectiveness of these nanorods as catalysts (accelerators) in the degradation of a pollutant. These applications are even more relevant considering that the scientific team was able to produce large quantities of the material through a simple and fast process. The work carried out shows the potential of these nanorods for the development of new medicines and for the treatment of effluents.

The work originated about three years ago when Professor Felipe de Almeida La Porta, who had recently joined the faculty of the Federal Technological University of Paraná (UTFPR), Londrina campus, was implementing a research group on nanotechnology and computational chemistry at this university. “Our laboratory was investigating some classes of emerging materials, with the perspective of aligning theory and practice, thus driving new discoveries and applications,” says La Porta. One of the materials studied by the group was zinc germanate (Zn2GeO4), a versatile semiconductor with well-known applications in sensors, catalysts, batteries and other devices.

Together with undergraduate researcher Victor Yuudi Suzuki, the professor started a project in which he synthesized pure Zn2GeO4 nanorods at the UTFPR laboratory with very small percentages of manganese ions. To produce this series of nanorods, they used “microwave assisted hydrothermal synthesis.” The method consists, in broad lines, of mixing aqueous solutions containing certain compounds, heating the final solution in a microwave oven and allowing the compounds to react for a certain period of time at controlled pressure and temperature. In this study, the manganese ion-doped Zn2GeO4 was prepared, and the reactions were performed at 140 °C for 10 minutes. The resulting material from these reactions was collected at room temperature, then washed and dried, which generate the nanorods.

Professor La Porta and his research group were able to optimize one of the process steps, the crystallization of materials, thus reducing the synthesis time from hours to a few minutes, but maintaining the quality of the material and the possibility to control its shape.

After preparing the samples, they traveled from Londrina (state of Paraná) to São Carlos (São Paulo state) to characterize the materials at the Center for Functional Materials Development (CDMF) at the Federal University of São Carlos (UFSCar) and at the Institute of Physics at the University of São Paulo (USP). Together with the local researchers, they were able to analyze the shape, structure and luminescence of the four types of nanorod compositions produced: manganese-free and with 1, 2 and 4% of this element incorporated into the structure of Zn2GeO4.

Finally, knowing that compounds containing zinc, germanium or manganese exhibit considerable effects on living things, the team contacted some collaborators to investigate these properties in the nanorods. Thus, several experiments were performed at the Departments of Chemistry and Pharmacy of the Federal University of Juiz de Fora and at the Federal University of Vales do Jequitinhonha and Mucuri, both in the state of Minas Gerais.

The authors of the paper. From the left: Victor Suzuki, Luís Amorin, Felipe La Porta, Maximo Si Li, Elson Longo, Sandra de Castro, Paloma de Carvalho, Alessandra Carli, Emanuelle Machado, Caio Alvez, Nerilson Lima.
The authors of the paper. From the left: Victor Suzuki, Luís Amorin, Felipe La Porta, Maximo Si Li, Elson Longo, Sandra de Castro, Paloma de Carvalho, Alessandra Carli, Emanuelle Machado, Caio Alvez, Nerilson Lima.

To study the anti-inflammatory action, the team performed in vitro tests (in contact with cells in laboratory containers) and also in vivo tests (using rats with paw edema, within the norms of the Brazilian code for laboratory animal use). Both types of experiments revealed that nanorods with about 4% manganese were the most effective in controlling inflammation. The in vitro tests showed these nanostructures were able to modulate molecules that regulate inflammation without causing cell death (without cytotoxicity). In the in vivo experiments, the nanorods reduced the induced rat paw edema with results similar to that of the application of dexamethasone, a well-known drug of the corticoid group.

“At first, we thought that combining these elements to form a ternary oxide could somehow potentiate these effects. But we had no idea the results would be so significant. Given that the drugs currently available in therapy are proving to be less effective every day, these results may encourage the use of these nanorods, for example in the production of a new pharmaceutical formulation, especially for cases of inflammation,” says Felipe La Porta, who is the corresponding author of the paper that was recently published by the research team in the Journal of Materials Chemistry C (impact factor 6,641).

In addition to proving the potential of the material for this application in the health area, the authors of the paper have experimentally verified the ability of nanorods to degrade a chemical dye widely found in industrial effluents, known as methylene blue. For this application, 2% manganese nanostructures were the most efficient, completely decomposing the dye in 10 minutes. “Due to the manufacture simplicity of this system, coupled with its excellent properties, this material is also promising for cleaning various environmental pollutants, and can be easily recovered at the end of this process,” adds Prof La Porta.

In the center, a cluster of 4% manganese zinc germanate nanorods. Clockwise: photoluminescence measurements of the samples; representation of the structure of manganese-doped zinc germanate; pollutant degradation mechanism and methylene blue degradation measures; anti-inflammatory action of nanorods and other treatments in induced-edema rat paw.
In the center, a cluster of 4% manganese zinc germanate nanorods. Clockwise: photoluminescence measurements of the samples; representation of the structure of manganese-doped zinc germanate; pollutant degradation mechanism and methylene blue degradation measures; anti-inflammatory action of nanorods and other treatments in induced-edema rat paw.

The superior properties that the Brazilian scientific team found in the nanorods with manganese can be related to the structural defects observed in these samples. In fact, the three-dimensional network of atoms that forms zinc germanate is crystalline, that is, organized in regular patterns. The introduction of manganese generates irregularities, and new properties emerge.

The scientific paper that reports this work was selected to be part of the Materials and Nano Research in Brazil collection, prepared by the Royal Society of Chemistry in celebration of the 18th B-MRS Meeting, and can therefore be accessed free of charge until October 15 of this year, here.

The work was carried out with funding from Brazilian research support agencies: the federal CNPq and Capes, and the state Araucaria Foundation, Fapesp and Fapemig.

Featured paper: New ozone sensor based on nanorods of silver tungstate.

The scientific paper by members of the Brazilian community on Materials research featured this month is:

Luís F. da Silva, Ariadne C. Catto, Waldir Avansi, Laécio S. Cavalcante, Juan Andrés,  Khalifa Aguir, Valmor R. Mastelaro and Elson Longo. A novel ozone gas sensor based on one-dimensional (1D) α-Ag2WO4 nanostructures. Nanoscale (Print), 2014, v. 1, p. 1-2. DOI: 10.1039/C3NR05837A

New ozone sensor based on nanorods of silver tungstate

A study carried out by a research group from Brazil, with collaboration from French and Spanish scientists, has reported, for the first time, gas detection properties in nanorods of silver tungstate in its alpha phase (α-Ag2WO4).The study showed that this material can be applied as a resistive sensor, displaying great performance when detecting ozone (O3). The work was and coordinated by Elson Longo, Professor at the São Paulo State University “Júlio de Mesquita Filho” (UNESP).

Resistive gas sensors are basically built from a material capable of changing its electrical properties when molecules of a certain gas are adsorbed in its surface. In the specific case of the silver tungstate, when it is submitted to an oxidant gas such as ozone, there is an increase in its electrical resistance that is proportional to the presence and concentration of the gas.

SEM image of the nanorods inside a diagram showing the sensor performance.

In this work, the Brazilian scientists synthesized nanorods of silver tungstate and assembled a sensor based on such nanoparticles. They had put the sensor in a temperature controlled test chamber, exposed it to different concentrations of ozone gas, from 80 to 930 parts per billion (ppb), and evaluated its capacity to detect the ozone.

Present in high atmospheric layers, the ozone plays an important role protecting living beings by absorbing the solar ultraviolet radiation. The ozone is also used by people in several applications, such as, for example, cleaning water. However, the exposition to the gas in certain concentrations may lead to health issues as headache, burning and irritation in the eyes, and respiratory system problems. The World Health Organization (WHO) recommends avoiding the exposure to ozone gas above 120 ppb.

“Subjecting the compound to low amounts of ozone, we observed a fast response, as well as a very short recovering time, making its properties comparable or even better than traditional sensors as tin dioxide (SnO2), tungsten trioxide (WO3), and indium oxide (In2O3),” says Luís Fernando da Silva, first author of the article and postdoctoral fellow of the São Paulo Research Foundation (Fapesp) at UNESP’s Chemistry Institute of Araraquara.

The results were published online in the peer reviewed journal Nanoscale in the end of January this year.

Background of the paper 

The studies with silver tungstate started in the postdoctoral research of Laécio Cavalcante, currently a Professor at Piauí State University (UESPI). Cavalcante synthesized nanorods of silver tungstate using microwave-assisted hydrothermal technique (process that was also used in the synthesis of nanorods from the paper published by Nanoscale). Performing electronic microscopic analysis with the microscope of the Chemistry Institute of Araraquara, the group of scientists coordinated by Professor Longo noticed that the interaction of the electron beam with the material was stimulating the growth of metallic silver particles on the surface of the nanorods. The result of this paper led to an article published in April last year by Scientific Reports (DOI: 10.1038/srep01676).

“Since then, Professor Elson Longo has researched and encouraged the investigation of the potentiality of the α-Ag2WO4 compound”, comments Luís Fernando da Silva. Longo, his team and partners have already observed that the material holds bactericidal (J. Phys. Chem. A, 2014; Doi:10.1021/jp410564p), photoluminescent (J. Phys. Chem. C, 2014, DOI: 10.1021/jp408167v), and photocatalytic properties, with a series of possible applications.

“Based on these potential applications”, Luís Fernando da Silva adds, “I, Professor Waltir Avansi Junior from the Physics Department of the Federal University of São Carlos (UFSCar), jointly with Professor Valmor Mastelaro from the São Carlos Physics Institute of São Paulo University (USP) and his PhD student, Ariadne Catto, started investigating about the detection properties of the non-irradiated α-Ag2WO4 compound (without nanoparticles of metallic silver)”. During the experiments, Silva says, the team noticed that the material was sensitive to detect ethanol and acetone steam and, ultimately, ozone gas, even in low amounts. Assisted by Professors Khalifa Aguir from Université Aix-Marseille (Marseille, France), and Juan Andrés, from Universitat Jaume I (Castelló, Spain), they prepared the communication published by Nanoscale, a renowned journal in the nanotechnology field.

The studies concerning silver tungstate performed by the team of Professor Longo might not end there. According to Luís Fernando da Silva, the team will assess the capacities of the material to detect other gases. In addition to that, returning to the silver tungstate nanorods with nanoparticles of metallic silver, the scientists are going to study the effects of electron irradiation on the gas detection capacity of the material.

“This paper contributes to the discovering of new materials applied as gas sensors”, states the postdoctoral fellow. “However, complementary examinations are necessary in order to achieve a deeper comprehension of the mechanisms involved in the detection, adsorption and desorption processes of the gas(es)”, he concludes.