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Nanomaterials
Volume 4
Issue 3
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Nanomaterials, Volume 4, Issue 3 (September 2014) – 17 articles , Pages 535-843

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1260 KiB  
Article
Fungal Hydrophobin Proteins Produce Self-Assembling Protein Films with Diverse Structure and Chemical Stability
by Victor C. Lo, Qin Ren, Chi L. L. Pham, Vanessa K. Morris, Ann H. Kwan and Margaret Sunde
Nanomaterials 2014, 4(3), 827-843; https://doi.org/10.3390/nano4030827 - 17 Sep 2014
Cited by 48 | Viewed by 11182
Abstract
Hydrophobins are small proteins secreted by fungi and which spontaneously assemble into amphipathic layers at hydrophilic-hydrophobic interfaces. We have examined the self-assembly of the Class I hydrophobins EAS∆15 and DewA, the Class II hydrophobin NC2 and an engineered chimeric hydrophobin. These Class [...] Read more.
Hydrophobins are small proteins secreted by fungi and which spontaneously assemble into amphipathic layers at hydrophilic-hydrophobic interfaces. We have examined the self-assembly of the Class I hydrophobins EAS∆15 and DewA, the Class II hydrophobin NC2 and an engineered chimeric hydrophobin. These Class I hydrophobins form layers composed of laterally associated fibrils with an underlying amyloid structure. These two Class I hydrophobins, despite showing significant conformational differences in solution, self-assemble to form fibrillar layers with very similar structures and require a hydrophilic-hydrophobic interface to trigger self-assembly. Addition of additives that influence surface tension can be used to manipulate the fine structure of the protein films. The Class II hydrophobin NC2 forms a mesh-like protein network and the engineered chimeric hydrophobin displays two multimeric forms, depending on assembly conditions. When formed on a graphite surface, the fibrillar EAS∆15 layers are resistant to alcohol, acid and basic washes. In contrast, the NC2 Class II monolayers are dissociated by alcohol treatment but are relatively stable towards acid and base washes. The engineered chimeric Class I/II hydrophobin shows increased stability towards alcohol and acid and base washes. Self-assembled hydrophobin films may have extensive applications in biotechnology where biocompatible; amphipathic coatings facilitate the functionalization of nanomaterials. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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879 KiB  
Article
Encapsulation of Anti-Tuberculosis Drugs within Mesoporous Silica and Intracellular Antibacterial Activities
by Xin Xia, Kevin Pethe, Ryangyeo Kim, Lluis Ballell, David Barros, Jonathan Cechetto, HeeKyoung Jeon, Kideok Kim and Alfonso E. Garcia-Bennett
Nanomaterials 2014, 4(3), 813-826; https://doi.org/10.3390/nano4030813 - 11 Sep 2014
Cited by 21 | Viewed by 7221
Abstract
Tuberculosis is a major problem in public health. While new effective treatments to combat the disease are currently under development, they tend suffer from poor solubility often resulting in low and/or inconsistent oral bioavailability. Mesoporous materials are here investigated in an in vitro [...] Read more.
Tuberculosis is a major problem in public health. While new effective treatments to combat the disease are currently under development, they tend suffer from poor solubility often resulting in low and/or inconsistent oral bioavailability. Mesoporous materials are here investigated in an in vitro intracellular assay, for the effective delivery of compound PA-824; a poorly soluble bactericidal agent being developed against Tuberculosis (TB). Mesoporous materials enhance the solubility of PA-824; however, this is not translated into a higher antibacterial activity in TB-infected macrophages after 5 days of incubation, where similar values are obtained. The lack of improved activity may be due to insufficient release of the drug from the mesopores in the context of the cellular environment. However, these results show promising data for the use of mesoporous particles in the context of oral delivery with expected improvements in bioavailability. Full article
(This article belongs to the Special Issue Ordered Mesoporous Nanomaterials)
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2873 KiB  
Review
Self-Assembly in Biosilicification and Biotemplated Silica Materials
by Francisco M. Fernandes, Thibaud Coradin and Carole Aimé
Nanomaterials 2014, 4(3), 792-812; https://doi.org/10.3390/nano4030792 - 4 Sep 2014
Cited by 37 | Viewed by 10110
Abstract
During evolution, living organisms have learned to design biomolecules exhibiting self-assembly properties to build-up materials with complex organizations. This is particularly evidenced by the delicate siliceous structures of diatoms and sponges. These structures have been considered as inspiration sources for the preparation of [...] Read more.
During evolution, living organisms have learned to design biomolecules exhibiting self-assembly properties to build-up materials with complex organizations. This is particularly evidenced by the delicate siliceous structures of diatoms and sponges. These structures have been considered as inspiration sources for the preparation of nanoscale and nanostructured silica-based materials templated by the self-assembled natural or biomimetic molecules. These templates range from short peptides to large viruses, leading to biohybrid objects with a wide variety of dimensions, shapes and organization. A more recent strategy based on the integration of biological self-assembly as the driving force of silica nanoparticles organization offers new perspectives to elaborate highly-tunable, biofunctional nanocomposites. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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476 KiB  
Article
Inclusion of Zinc Oxide Nanoparticles into Virus-Like Peptide Nanocapsules Self-Assembled from Viral β-Annulus Peptide
by Seiya Fujita and Kazunori Matsuura
Nanomaterials 2014, 4(3), 778-791; https://doi.org/10.3390/nano4030778 - 2 Sep 2014
Cited by 26 | Viewed by 8929
Abstract
A viral β-annulus peptide connected with a zinc oxide (ZnO)-binding sequence (HCVAHR) at its N-terminal was synthesized, and the inclusion behavior of quantum-sized ZnO nanoparticles into the peptide nanocapsules formed by self-assembly of the peptide in water was investigated. Dynamic light scattering (DLS) [...] Read more.
A viral β-annulus peptide connected with a zinc oxide (ZnO)-binding sequence (HCVAHR) at its N-terminal was synthesized, and the inclusion behavior of quantum-sized ZnO nanoparticles into the peptide nanocapsules formed by self-assembly of the peptide in water was investigated. Dynamic light scattering (DLS) measurements showed that ZnO nanoparticles (approximately 10 nm) in the presence of the peptide (0.1 mM) formed assemblies with an average size of 48 ± 24 nm, whereas ZnO nanoparticles in the absence of the peptide formed large aggregates. Transmission electron microscopy (TEM) observations of the ZnO nanoparticles in the presence of the peptide revealed that ZnO nanoparticles were encapsulated into the peptide nanocapsules with a size of approximately 50 nm. Fluorescence spectra of a mixture of the peptide and ZnO nanoparticles suggested that the ZnO surface and the peptide interact. Template synthesis of ZnO nanoparticles with the peptide nanocapsules afforded larger nanoparticles (approximately 40 nm), which are not quantum-sized ZnO. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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2790 KiB  
Article
Self-Assembling Organic Micro-/Nano-Pillars on Gold and Glass Surfaces
by Hai-Feng Ji, Wenli Ruan, Yingying Li and Guohua Ding
Nanomaterials 2014, 4(3), 768-777; https://doi.org/10.3390/nano4030768 - 2 Sep 2014
Cited by 4 | Viewed by 5591
Abstract
In this work, we report the formation of a family of organic micro-/nano-pillars prepared from surface-assisted self-assembly processes and factors controlling the growth of the pillars. These acids include cyanuric acid (CA), 1,3,5-benzenetricarboxylic acid (TMA), 1,2,4,5-benzenetetracarboxylic acid (TA) and 3,4,9,10-perylenetetracarboxylic acid (PTA). Aqueous [...] Read more.
In this work, we report the formation of a family of organic micro-/nano-pillars prepared from surface-assisted self-assembly processes and factors controlling the growth of the pillars. These acids include cyanuric acid (CA), 1,3,5-benzenetricarboxylic acid (TMA), 1,2,4,5-benzenetetracarboxylic acid (TA) and 3,4,9,10-perylenetetracarboxylic acid (PTA). Aqueous solutions mixed with acids and melamine (M) can be fine-tuned to prepare ordered micro-/nano-pillars on substrates, which can be further optimized for their applications Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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129 KiB  
Editorial
Challenges and Advances in Nanotoxicology
by Robert L. Tanguay
Nanomaterials 2014, 4(3), 766-767; https://doi.org/10.3390/nano4030766 - 22 Aug 2014
Cited by 4 | Viewed by 4888
Abstract
This Special Issue of Nanomaterials examines the potential for engineered nanomaterials to negatively impact biological systems and highlights some advances in evaluating key areas of their hazard potential. Nanomaterial science is evolving rapidly with the generation of more complex nanostructures with exciting potential [...] Read more.
This Special Issue of Nanomaterials examines the potential for engineered nanomaterials to negatively impact biological systems and highlights some advances in evaluating key areas of their hazard potential. Nanomaterial science is evolving rapidly with the generation of more complex nanostructures with exciting potential applications. Keeping modern toxicology abreast of this innovation to the point that it guides a safer nanotechnology presents an equally exciting and eminently worthwhile challenge. [...] Full article
(This article belongs to the Special Issue Nanotoxicology)
1654 KiB  
Review
Nano-Assemblies of Modified Cyclodextrins and Their Complexes with Guest Molecules: Incorporation in Nanostructured Membranes and Amphiphile Nanoarchitectonics Design
by Leïla Zerkoune, Angelina Angelova and Sylviane Lesieur
Nanomaterials 2014, 4(3), 741-765; https://doi.org/10.3390/nano4030741 - 20 Aug 2014
Cited by 80 | Viewed by 12732
Abstract
A variety of cyclodextrin-based molecular structures, with substitutions of either primary or secondary faces of the natural oligosaccharide macrocycles of α-, β-, or γ-cyclodextrins, have been designed towards innovative applications of self-assembled cyclodextrin nanomaterials. Amphiphilic cyclodextrins have been obtained by chemical or enzymatic [...] Read more.
A variety of cyclodextrin-based molecular structures, with substitutions of either primary or secondary faces of the natural oligosaccharide macrocycles of α-, β-, or γ-cyclodextrins, have been designed towards innovative applications of self-assembled cyclodextrin nanomaterials. Amphiphilic cyclodextrins have been obtained by chemical or enzymatic modifications of their macrocycles using phospholipidyl, peptidolipidyl, cholesteryl, and oligo(ethylene oxide) anchors as well as variable numbers of grafted hydrophobic hydrocarbon or fluorinated chains. These novel compounds may self-assemble in an aqueous medium into different types of supramolecular nanoassemblies (vesicles, micelles, nanorods, nanospheres, and other kinds of nanoparticles and liquid crystalline structures). This review discusses the supramolecular nanoarchitectures, which can be formed by amphiphilic cyclodextrin derivatives in mixtures with other molecules (phospholipids, surfactants, and olygonucleotides). Biomedical applications are foreseen for nanoencapsulation of drug molecules in the hydrophobic interchain volumes and nanocavities of the amphiphilic cyclodextrins (serving as drug carriers or pharmaceutical excipients), anticancer phototherapy, gene delivery, as well as for protection of instable active ingredients through inclusion complexation in nanostructured media. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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1204 KiB  
Article
The Use of the Calcitonin Minimal Recognition Module for the Design of DOPA-Containing Fibrillar Assemblies
by Galit Fichman, Tom Guterman, Lihi Adler-Abramovich and Ehud Gazit
Nanomaterials 2014, 4(3), 726-740; https://doi.org/10.3390/nano4030726 - 20 Aug 2014
Cited by 9 | Viewed by 7542
Abstract
Amyloid deposits are insoluble fibrous protein aggregates, identified in numerous diseases, which self-assemble through molecular recognition. This process is facilitated by short amino acid sequences, identified as minimal modules. Peptides corresponding to these motifs can be used for the formation of amyloid-like fibrillar [...] Read more.
Amyloid deposits are insoluble fibrous protein aggregates, identified in numerous diseases, which self-assemble through molecular recognition. This process is facilitated by short amino acid sequences, identified as minimal modules. Peptides corresponding to these motifs can be used for the formation of amyloid-like fibrillar assemblies in vitro. Such assemblies hold broad appeal in nanobiotechnology due to their ordered structure and to their ability to be functionalized. The catechol functional group, present in the non-coded L-3,4-dihydroxyphenylalanine (DOPA) amino acid, can take part in diverse chemical interactions. Moreover, DOPA-incorporated polymers have demonstrated adhesive properties and redox activity. In this work, amyloid-like fibrillar assemblies were formed through the self-assembly of a pentapeptide containing DOPA residues, Asp-DOPA-Asn-Lys-DOPA. The design of this peptide was based on the minimal amyloidogenic recognition motif of the human calcitonin hormone, Asp-Phe-Asn-Lys-Phe, the first amyloidogenic pentapeptide identified. By substituting phenylalanine with DOPA, we obtained DOPA-functionalized amyloid-like assemblies in water. Electron microscopy revealed elongated, linear fibril-like nanometric assemblies. Secondary structure analysis indicated the presence of amyloid-characteristic β-sheet structures as well as random coil structures. Deposition of silver on the DOPA-incorporated assemblies suggested redox activity and demonstrated the applicative potential of this novel nanobiomaterial. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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1735 KiB  
Article
High-Temperature Synthesis of Ordered Mesoporous Aluminosilicates from ZSM-5 Nanoseeds with Improved Acidic Properties
by Xuan Hoan Vu, Reinhard Eckelt, Udo Armbruster and Andreas Martin
Nanomaterials 2014, 4(3), 712-725; https://doi.org/10.3390/nano4030712 - 18 Aug 2014
Cited by 17 | Viewed by 6858
Abstract
Ordered mesoporous SBA-15 analogs with different Si/Al ratios were successfully prepared in a two-step process from self-assembly of ZSM-5 nanoseeds at high temperature in mildly acidic media (473 K, pH 3.5). The obtained products were characterized as SAXS, XRD, N2 sorption, FTIR, [...] Read more.
Ordered mesoporous SBA-15 analogs with different Si/Al ratios were successfully prepared in a two-step process from self-assembly of ZSM-5 nanoseeds at high temperature in mildly acidic media (473 K, pH 3.5). The obtained products were characterized as SAXS, XRD, N2 sorption, FTIR, TEM, NH3-TPD, AAS and ICP. The results show that the initial Si/Al molar ratio of ZSM-5 precursors strongly affects the final materials’ properties. A highly condensed, well-ordered mesoporous SBA-15 analog with improved hydrothermal stability and acidic properties can be prepared from low aluminum containing ZSM-5 precursors (Si/Al ≥ 20). Reducing the initial Si/Al molar ratio to 10, however, leads to the formation of a disordered mesoporous SBA-15 type material accompanied by degraded textural and acidic properties. The gas phase cracking of cumene, carried out as probe reaction to evaluate Brønsted acidity, reveals that an increased density of Brønsted acid sites has been achieved over the SBA-15 analogs compared to conventional Al-SBA-15 due to the preservation of zeolite building units in the mesopore walls of the SBA-15 analogs. Full article
(This article belongs to the Special Issue Ordered Mesoporous Nanomaterials)
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731 KiB  
Article
Effect of Porosity and Concentration Polarization on Electrolyte Diffusive Transport Parameters through Ceramic Membranes with Similar Nanopore Size
by Virginia Romero, Victor Vega, Javier García, Victor M. Prida, Blanca Hernando and Juana Benavente
Nanomaterials 2014, 4(3), 700-711; https://doi.org/10.3390/nano4030700 - 6 Aug 2014
Cited by 14 | Viewed by 6525
Abstract
Diffusive transport through nanoporous alumina membranes (NPAMs) produced by the two-step anodization method, with similar pore size but different porosity, is studied by analyzing membrane potential measured with NaCl solutions at different concentrations. Donnan exclusion of co-ions at the solution/membrane interface seem to [...] Read more.
Diffusive transport through nanoporous alumina membranes (NPAMs) produced by the two-step anodization method, with similar pore size but different porosity, is studied by analyzing membrane potential measured with NaCl solutions at different concentrations. Donnan exclusion of co-ions at the solution/membrane interface seem to exert a certain control on the diffusive transport of ions through NPAMs with low porosity, which might be reduced by coating the membrane surface with appropriated materials, as it is the case of SiO2. Our results also show the effect of concentration polarization at the membrane surface on ionic transport numbers (or diffusion coefficients) for low-porosity and high electrolyte affinity membranes, which could mask values of those characteristic electrochemical parameters. Full article
(This article belongs to the Special Issue Ordered Mesoporous Nanomaterials)
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2809 KiB  
Article
Fabrication of Meso-Porous Sintered Metal Thin Films by Selective Etching of Silica Based Sacrificial Template
by Ludovic F. Dumée, Fenghua She, Mikel Duke, Stephen Gray, Peter Hodgson and Lingxue Kong
Nanomaterials 2014, 4(3), 686-699; https://doi.org/10.3390/nano4030686 - 4 Aug 2014
Cited by 7 | Viewed by 7585
Abstract
Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by [...] Read more.
Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by shear mixing. The resulted powders were cold-sintered to form dense, hybrid thin films. The sacrificial silica template was then removed by selective etching in 12 wt% hydrofluoric acid solutions for 15 min to reveal a purely metallic meso-porous thin film material. The impact of the initial silica nano-particle diameter (7–20 nm) as well as the sintering pressure (5–20 ton·m−2) and etching conditions on the morphology and properties of the final nano-porous thin films were investigated by porometry, pyknometery, gas and liquid permeation and electron microscopy. Furthermore, the morphology of the pores and particle aggregation during shear mixing were assessed through cross-sectioning by focus ion beam milling. It is demonstrated that meso-pores ranging between 50 and 320 nm in average diameter and porosities up to 47% can be successfully formed for the range of materials tested. Full article
(This article belongs to the Special Issue Ordered Mesoporous Nanomaterials)
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19633 KiB  
Review
Templated Synthesis of Magnetic Nanoparticles through the Self-Assembly of Polymers and Surfactants
by Vo Thu An Nguyen, Mario Gauthier and Olivier Sandre
Nanomaterials 2014, 4(3), 628-685; https://doi.org/10.3390/nano4030628 - 4 Aug 2014
Cited by 22 | Viewed by 17483
Abstract
The synthesis of superparamagnetic nanoparticles (NPs) for various technological applications continues to be an interesting research topic. The successful application of superparamagnetic NPs to each specific area typically depends on the achievement of high magnetization for the nanocrystals obtained, which is determined by [...] Read more.
The synthesis of superparamagnetic nanoparticles (NPs) for various technological applications continues to be an interesting research topic. The successful application of superparamagnetic NPs to each specific area typically depends on the achievement of high magnetization for the nanocrystals obtained, which is determined by their average size and size distribution. The size dispersity of magnetic NPs (MNPs) is markedly improved when, during the synthesis, the nucleation and growth steps of the reaction are well-separated. Tuning the nucleation process with the assistance of a hosting medium that encapsulates the precursors (such as self-assembled micelles), dispersing them in discrete compartments, improves control over particle formation. These inorganic-organic hybrids inherit properties from both the organic and the inorganic materials, while the organic component can also bring a specific functionality to the particles or prevent their aggregation in water. The general concept of interest in this review is that the shape and size of the synthesized MNPs can be controlled to some extent by the geometry and the size of the organic templates used, which thus can be considered as molds at the nanometer scale, for both porous continuous matrices and suspensions. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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1852 KiB  
Article
Design of Magnetic Gelatine/Silica Nanocomposites by Nanoemulsification: Encapsulation versus in Situ Growth of Iron Oxide Colloids
by Joachim Allouche, Corinne Chanéac, Roberta Brayner, Michel Boissière and Thibaud Coradin
Nanomaterials 2014, 4(3), 612-627; https://doi.org/10.3390/nano4030612 - 31 Jul 2014
Cited by 10 | Viewed by 9805
Abstract
The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first [...] Read more.
The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first method leads to bi-continuous hybrid nanocomposites containing a limited amount of well-dispersed magnetite colloids. In contrast, the second approach allows the formation of gelatine-silica core-shell nanostructures incorporating larger amounts of agglomerated iron oxide colloids. Both magnetic nanocomposites exhibit similar superparamagnetic behaviors. Whereas nanocomposites obtained via an in situ approach show a strong tendency to aggregate in solution, the encapsulation route allows further surface modification of the magnetic nanocomposites, leading to quaternary gold/iron oxide/silica/gelatine nanoparticles. Hence, such a first-time rational combination of nano-emulsion, nanocrystallization and sol-gel chemistry allows the elaboration of multi-component functional nanomaterials. This constitutes a step forward in the design of more complex bio-nanoplatforms. Full article
(This article belongs to the Special Issue Self-Assembled Nanomaterials)
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4035 KiB  
Article
Electrochemical Properties of Poly(Anthraquinonyl Sulfide)/Graphene Sheets Composites as Electrode Materials for Electrochemical Capacitors
by Wonkyun Lee, Shinya Suzuki and Masaru Miyayama
Nanomaterials 2014, 4(3), 599-611; https://doi.org/10.3390/nano4030599 - 30 Jul 2014
Cited by 31 | Viewed by 6663
Abstract
Poly(anthraquinonyl sulfide) (PAQS)/graphene sheets (GSs) composite was synthesized through in situ polymerization to evaluate its performance as an electrode material for electrochemical capacitors. PAQS was successfully synthesized in the presence of GSs with uniform distribution. PAQS/GSs showed a pair of reversible redox peaks [...] Read more.
Poly(anthraquinonyl sulfide) (PAQS)/graphene sheets (GSs) composite was synthesized through in situ polymerization to evaluate its performance as an electrode material for electrochemical capacitors. PAQS was successfully synthesized in the presence of GSs with uniform distribution. PAQS/GSs showed a pair of reversible redox peaks at around 0 V (vs. Ag/AgCl). The specific capacitance of PAQS/GSs was 349 F·g−1 (86 mAh·g−1) at a current density of 500 mA·g−1, and a capacitance of 305 F·g−1 was maintained even at a high current density of 5000 mA·g−1. The in situ polymerization of PAQS with GSs facilitated their interaction and enabled faster charge transfer and redox reaction, resulting in enhanced electrode properties. Full article
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3331 KiB  
Article
Mesoporous Titania Powders: The Role of Precursors, Ligand Addition and Calcination Rate on Their Morphology, Crystalline Structure and Photocatalytic Activity
by Elisabetta Masolo, Manuela Meloni, Sebastiano Garroni, Gabriele Mulas, Stefano Enzo, Maria Dolors Baró, Emma Rossinyol, Agnieszka Rzeszutek, Iris Herrmann-Geppert and Maria Pilo
Nanomaterials 2014, 4(3), 583-598; https://doi.org/10.3390/nano4030583 - 30 Jul 2014
Cited by 21 | Viewed by 8035
Abstract
We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, [...] Read more.
We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N2 physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl4 and Ti(OBu)4, and a more classic route with Ti(OiPr)4 and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and tested in the water splitting reaction by recording I-V curves and comparing the results with commercial P25 powders. The complex data framework suggests that a narrow pore size distribution, due to the use of acetylacetone, plays a major role in the photoactivity, leading to a current density value higher than that of P25. Full article
(This article belongs to the Special Issue Ordered Mesoporous Nanomaterials)
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967 KiB  
Review
Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity
by Vanessa Cohignac, Marion Julie Landry, Jorge Boczkowski and Sophie Lanone
Nanomaterials 2014, 4(3), 548-582; https://doi.org/10.3390/nano4030548 - 8 Jul 2014
Cited by 53 | Viewed by 13037
Abstract
The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes [...] Read more.
The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes of nanomaterials. It has been shown that some of them can induce toxic effects, essentially depending on their physico-chemical characteristics, but other studies did not identify such effects. Inflammation and oxidative stress are currently the two main mechanisms described to explain the observed toxicity. However, the exact underlying mechanism(s) still remain(s) unknown and autophagy could represent an interesting candidate. Autophagy is a physiological process in which cytoplasmic components are digested via a lysosomal pathway. It has been shown that autophagy is involved in the pathogenesis and the progression of human diseases, and is able to modulate the oxidative stress and pro-inflammatory responses. A growing amount of literature suggests that a link between nanomaterial toxicity and autophagy impairment could exist. In this review, we will first summarize what is known about the respiratory effects of nanomaterials and we will then discuss the possible involvement of autophagy in this toxicity. This review should help understand why autophagy impairment could be taken as a promising candidate to fully understand nanomaterials toxicity. Full article
(This article belongs to the Special Issue Nanotoxicology)
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463 KiB  
Article
Accumulation and Toxicity of Copper Oxide Engineered Nanoparticles in a Marine Mussel
by Shannon K. Hanna, Robert J. Miller and Hunter S. Lenihan
Nanomaterials 2014, 4(3), 535-547; https://doi.org/10.3390/nano4030535 - 27 Jun 2014
Cited by 42 | Viewed by 8291
Abstract
Cu is an essential trace element but can be highly toxic to aquatic organisms at elevated concentrations. Greater use of CuO engineered nanoparticles (ENPs) may lead to increased concentrations of CuO ENPs in aquatic environments causing potential ecological injury. We examined the toxicity [...] Read more.
Cu is an essential trace element but can be highly toxic to aquatic organisms at elevated concentrations. Greater use of CuO engineered nanoparticles (ENPs) may lead to increased concentrations of CuO ENPs in aquatic environments causing potential ecological injury. We examined the toxicity of CuO ENPs to marine mussels and the influence of mussels on the fate and transport of CuO ENPs. We exposed marine mussels to 1, 2, or 3 mg L−1 CuO ENPs for four weeks, and measured clearance rate, rejection, excretion and accumulation of Cu, and mussel shell growth. Mussel clearance rate was 48% less, and growth was 68% less, in mussels exposed to 3 mg L−1 than in control animals. Previous studies show 100% mortality at 1 mg Cu L−1, suggesting that CuO ENPs are much less toxic than ionic Cu, probably due to the slow dissolution rate of the ENPs. Mussels rejected and excreted CuO ENPs in biodeposits containing as much as 110 mg Cu g−1, suggesting the potential for magnification in sediments. Mussels exposed to 3 mg L−1 CuO ENPs accumulated 79.14 ± 12.46 µg Cu g−1 dry weight, which was 60 times more Cu than in control animals. Our results suggest that mussels have the potential to influence the fate and transport of CuO ENPs and potentially cause magnification of CuO ENPs in mussel bed communities, creating a significant source of Cu to marine benthos. Full article
(This article belongs to the Special Issue Nanotoxicology)
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