Germán Plascencia‐Villa

The University of Texas at San Antonio

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Miguel José‐Yacamán

Northern Arizona University

George Perry

The University of Texas at San Antonio

M. Josefina Arellano-Jiménez

The University of Texas at Dallas

Susmita Bandyopadhyay

University of Burdwan

Xiongwei Zhu

Case Western Reserve University

Jorge L. Gardea‐Torresdey

The University of Texas at El Paso

Joanna F. Collingwood

University of Warwick

Jose R. Peralta‐Videa

The University of Texas at El Paso

Juan Francisco Sánchez Pérez

Universidad Politécnica de Cartagena

Laura A. Palomares

Universidad Nacional Autónoma de México

Cooperative Institutions

University of Warwick

The University of Texas at San Antonio

Universidad Nacional Autónoma de México

Coventry (United Kingdom)

Instituto Politécnico Nacional

The University of Texas at El Paso

Center for Research and Advanced Studies of the National Polytechnic Institute

The University of Texas at Austin

Universidad Autónoma del Estado de Morelos

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Integrative structural and advanced imaging characterization of manganese oxide nanotubes doped with cobaltite

CrystEngComm (2017)

J.E. Samaniego-Benítez J. Jesús Velázquez‐Salazar Rubén Mendoza‐Cruz Lourdes Bazán-Díaz Germán Plascencia‐Villa

Manganese oxide nanotubes (MnO2) were efficiently produced through a hydrothermal method, using SiO2 powder as nucleation points, then doped with cobaltite (Co3O4) nanoparticles uniformly deposited along the surface of the MnO2 nanotubes. An integrative approach using advanced analytical electron microscopy techniques (UHR FE-SEM, HR-TEM, and BF/HAADF-STEM, coupled with EDX) in combination with spectroscopy allowed the determination of the structural characteristics of this composite nanomaterial. Advanced imaging clearly revealed the tubular structure of the MnO2 nanotubes (diameter of 30–80 nm and length of 3–5 μm) and the arrangement of the discrete Co3O4 deposits (10–40 nm). Remarkably, high-resolution and spherical aberration-corrected STEM imaging allowed for the determination of the crystalline arrangement of the nanomaterials, particularly at the interface between MnO2 and Co3O4 particles with high spatial sub-Angstrom resolution, revealing the distribution and high structural consistency of the novel composite materials produced. Furthermore, X-ray diffraction and Raman spectroscopy confirmed that MnO2 corresponded to the crystallographic phase cryptomelane (K2-xMn8O16), while the dopant cobalt nanoparticles adopted a cobaltite (Co3O4) phase. We demonstrated the catalytic properties of the composite MnO2–Co3O4 nanotubes as an electrocatalyst material for oxygen evolution, where it showed superior behaviour, with a significantly higher catalytic activity (6.8 times) than pure MnO2 in the OER region.

Cobaltite

Nanomaterials

Cobalt oxide

10.1039/c7ce00315c

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Use of recombinant rotavirus VP6 nanotubes as a multifunctional template for the synthesis of nanobiomaterials functionalized with metals

Biotechnology and Bioengineering (2009)

Germán Plascencia‐Villa José M. Sániger J.A. Ascencio Laura A. Palomares Octavio T. Ramı́rez

The structural characteristics and predefined constant size and shape of viral assemblies make them useful tools for nanobiotechnology, in particular as scaffolds for constructing highly organized novel nanomaterials. In this work it is shown for the first time that nanotubes formed by recombinant rotavirus VP6 protein can be used as scaffolds for the synthesis of hybrid nanocomposites. Rotavirus VP6 was produced by the insect cell-baculovirus expression vector system. Nanotubes of several micrometers in length and various diameters in the nanometer range were functionalized with Ag, Au, Pt, and Pd through strong (sodium borohydride) or mild (sodium citrate) chemical reduction. The nanocomposites obtained were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM) with energy dispersive spectroscopy (EDS), dynamic light scattering, and their characteristic plasmon resonance. The outer surface of VP6 nanotubes had intrinsic affinity to metal deposition that allowed in situ synthesis of nanoparticles. Furthermore, the use of preassembled recombinant protein structures resulted in highly ordered integrated materials. It was possible to obtain different extents and characteristics of the metal coverage by manipulating the reaction conditions. TEM revealed either a continuous coverage with an electrodense thin film when using sodium citrate as reductant or a discrete coverage with well-dispersed metal nanoparticles of diameters between 2 and 9 nm when using sodium borohydride and short reaction times. At long reaction times and using sodium borohydride, the metal nanoparticles coalesced and resulted in a thick metal layer. HRTEM-EDS confirmed the identity of the metal nanoparticles. Compared to other non-recombinant viral scaffolds used until now, the recombinant VP6 nanotubes employed here have important advantages, including a longer axial dimension, a dynamic multifunctional hollow structure, and the possibility of producing them massively by a safe and efficient bioprocess. Such characteristics confer important potential applications in nanotechnology to the novel nanobiomaterials produced here.

Sodium borohydride

10.1002/bit.22497

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Biogenic metallic elements in the human brain?

Science Advances (2021)

James Everett Frederik Lermyte Jake Brooks Vindy Tjendana Tjhin Germán Plascencia‐Villa

The chemistry of copper and iron plays a critical role in normal brain function. A variety of enzymes and proteins containing positively charged Cu

Brain Function

Human brain

10.1126/sciadv.abf6707

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High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer’s disease

Scientific Reports (2016)

Germán Plascencia‐Villa Arturo Ponce Joanna F. Collingwood M. Josefina Arellano-Jiménez Xiongwei Zhu

Abstract Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe 3 O 4 ) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

Electron holography

Superparamagnetism

10.1038/srep24873

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Citations (128)

Central role of brain regulatory T cells in the inflammatory cascade in Alzheimer’s disease

Proceedings of the National Academy of Sciences (2024)

Germán Plascencia‐Villa Rudolph J. Castellani George Perry

10.1073/pnas.2412255121

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Citations (2)

Comparative phytotoxicity of ZnO NPs, bulk ZnO, and ionic zinc onto the alfalfa plants symbiotically associated with Sinorhizobium meliloti in soil