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Nanomaterials
Volume 6
Issue 2
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Nanomaterials, Volume 6, Issue 2 (February 2016) – 11 articles

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1289 KiB  
Communication
Degradable Dextran Nanopolymer as a Carrier for Choline Kinase (ChoK) siRNA Cancer Therapy
by Zhihang Chen, Balaji Krishnamachary and Zaver M. Bhujwalla
Nanomaterials 2016, 6(2), 34; https://doi.org/10.3390/nano6020034 - 22 Feb 2016
Cited by 19 | Viewed by 6197
Abstract
Although small interfering RNA (siRNA) therapy has proven to be a specific and effective treatment in cells, the delivery of siRNA is a challenge for the applications of siRNA therapy. We present a degradable dextran with amine groups as an siRNA nano-carrier. In [...] Read more.
Although small interfering RNA (siRNA) therapy has proven to be a specific and effective treatment in cells, the delivery of siRNA is a challenge for the applications of siRNA therapy. We present a degradable dextran with amine groups as an siRNA nano-carrier. In our nano-carrier, the amine groups are conjugated to the dextran platform through the acetal bonds, which are acid sensitive. Therefore this siRNA carrier is stable in neutral and basic conditions, while the amine groups can be cleaved and released from dextran platform under weak acid conditions (such as in endosomes). The cleavage and release of amine groups can reduce the toxicity of cationic polymer and enhance the transfection efficiency. We successfully applied this nano-carrier to deliver choline kinase (ChoK) siRNA for ChoK inhibition in cells. Full article
(This article belongs to the Special Issue Nanomaterials for Cancer Therapies)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) Hydrodynamic radius of dextran and amino-dextran dextran from intensity-based distributions. (<b>B</b>) Transmission electron microscopy (TEM) image of amino-dextran. Negative staining with phosphotungstic acid (PTA), scale bar is 100 nm. (<b>C</b>) Zeta potential of dextran and amino-dextran dextran. <span class="html-italic">n</span> = 3, values represent Mean ± standard deviation (SD).</p> Full article ">Figure 2
<p>(<b>A</b>) The rhodamine absorbance of 1 mg/mL dextran solution in pH 5.5 and pH 7.4 buffer at different time points. <span class="html-italic">n</span> = 3, values represent Mean ± SD. (<b>B</b>) Inhibition efficiency of choline kinase (ChoK) messenger RNA (mRNA) in MDA-MB-231 cells with different siRNA transfection agent treatments. Small interfering RNA (siRNA) concentration: 100 nM; N/P ratio: 15. Cells were treated with siRNA/dextran for 24 h, following by a further 6 h incubation in fresh medium. <span class="html-italic">n</span> = 3, values represent Mean ± SD. *, <span class="html-italic">p</span> &lt; 0.05.</p> Full article ">Figure 3
<p>Representative laser confocal fluorescence microscopy fields of view of MDA-MB-231 cells treated with siRNA/dextran nano-carrier. Cells were treated with fluorescein isothiocyanate (FITC)-siRNA/dextran nano-carrier at a concentration of siRNA: 50 nM and N/P ratio: 15.</p> Full article ">Figure 4
<p>Synthetic procedure of generating a degradable amino-dextran small interfering RNA (siRNA) carrier. <b>1</b>: Dextran with acetal group; <b>2</b>: Amino-dextran; <b>3</b>: Rhodamine labeled amino-dextran.</p> Full article ">
551 KiB  
Article
EU Regulation of Nanobiocides: Challenges in Implementing the Biocidal Product Regulation (BPR)
by Anna Brinch, Steffen Foss Hansen, Nanna B. Hartmann and Anders Baun
Nanomaterials 2016, 6(2), 33; https://doi.org/10.3390/nano6020033 - 16 Feb 2016
Cited by 41 | Viewed by 9214
Abstract
The Biocidal Products Regulation (BPR) contains several provisions for nanomaterials (NMs) and is the first regulation in the European Union to require specific testing and risk assessment for the NM form of a biocidal substance as a part of the information requirements. Ecotoxicological [...] Read more.
The Biocidal Products Regulation (BPR) contains several provisions for nanomaterials (NMs) and is the first regulation in the European Union to require specific testing and risk assessment for the NM form of a biocidal substance as a part of the information requirements. Ecotoxicological data are one of the pillars of the information requirements in the BPR, but there are currently no standard test guidelines for the ecotoxicity testing of NMs. The overall objective of this work was to investigate the implications of the introduction of nano-specific testing requirements in the BPR and to explore how these might be fulfilled in the case of copper oxide nanoparticles. While there is information and data available in the open literature that could be used to fulfill the BPR information requirements, most of the studies do not take the Organisation for Economic Co-operation and Development’s nanospecific test guidelines into consideration. This makes it difficult for companies as well as regulators to fulfill the BPR information requirements for nanomaterials. In order to enable a nanospecific risk assessment, best practices need to be developed regarding stock suspension preparation and characterization, exposure suspensions preparation, and for conducting ecotoxicological test. Full article
(This article belongs to the Special Issue Engineered Nanomaterials in the Environment)
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Figure 1
<p>Number of studies potentially fulfilling the Biocidal Product Regulation (BPR) information requirements for ecotoxicity tests.</p> Full article ">Figure 2
<p>Number of ecotoxicity studies on copper oxide nanoparticles considering the reporting and characterization parameters recommended in the Organisation for Economic Co-operation and Development (OECD) guidance document [<a href="#B18-nanomaterials-06-00033" class="html-bibr">18</a>].</p> Full article ">
3180 KiB  
Article
Energy Transfer between Conjugated Colloidal Ga2O3 and CdSe/CdS Core/Shell Nanocrystals for White Light Emitting Applications
by Paul C. Stanish and Pavle V. Radovanovic
Nanomaterials 2016, 6(2), 32; https://doi.org/10.3390/nano6020032 - 15 Feb 2016
Cited by 8 | Viewed by 6387
Abstract
Developing solid state materials capable of generating homogeneous white light in an energy efficient and resource-sustainable way is central to the design of new and improved devices for various lighting applications. Most currently-used phosphors depend on strategically important rare earth elements, and rely [...] Read more.
Developing solid state materials capable of generating homogeneous white light in an energy efficient and resource-sustainable way is central to the design of new and improved devices for various lighting applications. Most currently-used phosphors depend on strategically important rare earth elements, and rely on a multicomponent approach, which produces sub-optimal quality white light. Here, we report the design and preparation of a colloidal white-light emitting nanocrystal conjugate. This conjugate is obtained by linking colloidal Ga2O3 and II–VI nanocrystals in the solution phase with a short bifunctional organic molecule (thioglycolic acid). The two types of nanocrystals are electronically coupled by Förster resonance energy transfer owing to the short separation between Ga2O3 (energy donor) and core/shell CdSe/CdS (energy acceptor) nanocrystals, and the spectral overlap between the photoluminescence of the donor and the absorption of the acceptor. Using steady state and time-resolved photoluminescence spectroscopies, we quantified the contribution of the energy transfer to the photoluminescence spectral power distribution and the corresponding chromaticity of this nanocrystal conjugate. Quantitative understanding of this new system allows for tuning of the emission color and the design of quasi-single white light emitting inorganic phosphors without the use of rare-earth elements. Full article
(This article belongs to the Special Issue Current Trends in Colloidal Nanocrystals)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Overview transmission electron microscopy (TEM) image of colloidal γ-Ga<sub>2</sub>O<sub>3</sub> nanocrystals (NCs) having an average dimeter of <span class="html-italic">ca</span>. 5.5 nm; (<b>b</b>) X-ray diffraction (XRD) pattern of the same NCs; vertical black lines represent a reference XRD pattern of bulk γ-phase Ga<sub>2</sub>O<sub>3</sub>; (<b>c</b>) Overview TEM image of <span class="html-italic">ca</span>. 6.8 nm CdSe/CdS core/shell NCs; (<b>d</b>) Absorption (red) and photoluminescence (PL) (blue) spectra of CdSe/CdS NCs (solid lines), and the absorption spectrum of the corresponding CdSe NC cores (red dashed line).</p> Full article ">Figure 2
<p>(<b>a</b>) Overview TEM image of colloidal Ga<sub>2</sub>O<sub>3</sub>-CdSe/CdS NC conjugate obtained using NCs shown in <a href="#nanomaterials-06-00032-f001" class="html-fig">Figure 1</a>; (<b>b</b>) High resolution TEM image of the same sample. Orange and blue circles indicate CdSe/CdS and Ga<sub>2</sub>O<sub>3</sub> NCs, respectively; the lattice spacings shown correspond to {002} and {311} planes of CdS and Ga<sub>2</sub>O<sub>3</sub>, respectively; (<b>c</b>–<b>e</b>) Scanning transmission electron microscopy (STEM) image of the nanocrystal conjugate (<b>c</b>); and the corresponding Ga (<b>d</b>) and Cd (<b>e</b>) energy-dispersive X-ray spectroscopy (EDX) elemental maps.</p> Full article ">Figure 3
<p>Absorption spectrum of CdSe/CdS NCs (orange line) and PL spectrum of Ga<sub>2</sub>O<sub>3</sub> NCs (blue line). Excitation wavelength for Ga<sub>2</sub>O<sub>3</sub> NCs is 250 nm. Shaded area indicates a spectral overlap, as an essential requirement for Förster resonance energy transfer (FRET).</p> Full article ">Figure 4
<p>(<b>a</b>) PL spectra of colloidal Ga<sub>2</sub>O<sub>3</sub>-CdSe/CdS NC conjugates (solid lines) having different CdSe/CdS to Ga<sub>2</sub>O<sub>3</sub> NC concentration ratio, as indicated in the graph. PL spectra of thioglycolic acid (TGA)-bound CdSe/CdS NC suspensions having the same concentration as in the NC conjugate are shown with dashed lines (λ<sub>exc</sub> = 250 nm); (<b>b</b>) PL spectra of the mixtures of Ga<sub>2</sub>O<sub>3</sub> and CdSe/CdS NCs prepared in the same way as the NC conjugate but without the TGA linker; (<b>c</b>) Quenching efficiency of the donor-acceptor pair (DAP) emission of Ga<sub>2</sub>O<sub>3</sub> NCs in the conjugate (squares), mixed with CdSe/CdS NCs (circles), and mixed with TGA but without CdSe/CdS NCs (triangles).</p> Full article ">Figure 5
<p>(<b>a</b>) Time-resolved DAP PL decay of Ga<sub>2</sub>O<sub>3</sub> NCs containing different amounts of surface-bound TGA without CdSe/CdS NCs. TGA equivalents and absolute concentrations (in parentheses) in Ga<sub>2</sub>O<sub>3</sub> NC suspensions are indicated in the graph (aqua blue trace (0.84 mM) represents TGA concentration for the highest acceptor to donor ratio); (<b>b</b>) Time-resolved DAP PL decay of Ga<sub>2</sub>O<sub>3</sub> NCs in the NC conjugates having different CdSe/CdS to Ga<sub>2</sub>O<sub>3</sub> NC concentration ratio, as indicated in the graph; (<b>c</b>) Quenching efficiency of the DAP PL of Ga<sub>2</sub>O<sub>3</sub> NCs in the NC conjugate (squares) and with bound TGA (triangles).</p> Full article ">Figure 6
<p>FRET efficiency in Ga<sub>2</sub>O<sub>3</sub>-CdSe/CdS NC conjugate (circles) determined from the DAP PL lifetime data corrected for the lifetime shortenening due to TGA binding. The experimental data were fit using Equation (5) (dashed line). Solid line is the FRET efficiency predicted by the Förster theory (Equation (3)).</p> Full article ">Figure 7
<p>International Commission on Illumination 1931 (CIE 1931) color coordinate diagram for Ga<sub>2</sub>O<sub>3</sub>-CdSe/CdS NC conjugate having different acceptor to donor ratio. The photographs of the colloidal nanoconjugates corresponding to data points labeled in the graph are shown as insets.</p> Full article ">
1609 KiB  
Article
Effect of NaCl on the Lifetime of Micro- and Nanobubbles
by Tsutomu Uchida, Shu Liu, Masatoshi Enari, Seiichi Oshita, Kenji Yamazaki and Kazutoshi Gohara
Nanomaterials 2016, 6(2), 31; https://doi.org/10.3390/nano6020031 - 5 Feb 2016
Cited by 79 | Viewed by 8471
Abstract
Micro- and nanobubbles (MNBs) are potentially useful for industrial applications such as the purification of wastewater and the promotion of physiological activities of living organisms. To develop such applications, we should understand their properties and behavior, such as their lifetime and their number [...] Read more.
Micro- and nanobubbles (MNBs) are potentially useful for industrial applications such as the purification of wastewater and the promotion of physiological activities of living organisms. To develop such applications, we should understand their properties and behavior, such as their lifetime and their number density in solution. In the present study, we observed oxygen MNBs distributed in an electrolyte (NaCl) solution using a transmission electron microscope to analyze samples made with the freeze-fracture replica method. We found that MNBs in a 100 mM NaCl solution remain for at least 1 week, but at higher concentrations decay more quickly. To better understand their lifetimes, we compared measurements of the solution's dissolved oxygen concentration and the ζ-potential of the MNBs. Our detailed observations of transmission electron microscopy (TEM) images allows us to conclude that low concentrations of NaCl stabilize MNBs due to the ion shielding effect. However, higher concentrations accelerate their disappearance by reducing the repulsive force between MNBs. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Transmission electron microscopy (TEM) images of micro- and nanobubbles (MNBs) in (<b>a</b>,<b>b</b>) 10 mM and (<b>c</b>,<b>d</b>) 100 mM NaCl solutions. Each scale bar shows 100 nm. A bubble hole was sometimes covered with thin film (relatively brighter image) formed inside of the hole.</p> Full article ">Figure 2
<p>Apparent bubble diameter (<span class="html-italic">D</span>) observed from TEM-freeze-fracture replica method in 0 mM NaCl solution after 1 h MNB generation (solid bar, <span class="html-italic">n</span> = 39), and in pure water without MNB generation (open bar, <span class="html-italic">n</span> = 31).</p> Full article ">Figure 3
<p>(<b>a</b>) The cumulative distributions of <span class="html-italic">D</span> in different NaCl concentrations (0 mM: Solid line, 10 mM: larger dashed line, 100 mM: Smaller dashed line, 1 wt %: Dotted line, 3.5 wt %: Double solid line, pure water: thin dotted line). The value at the largest <span class="html-italic">D</span> equals the number density <span class="html-italic">N</span>. (<b>b</b>) Apparent bubble diameter distributions in 100 mM NaCl solution (coarse dot bar, <span class="html-italic">n</span> = 39), and in 3.5 wt % NaCl solution (fine dot bar, <span class="html-italic">n</span> = 20).</p> Full article ">Figure 4
<p>(<b>a</b>) Similar to <a href="#nanomaterials-06-00031-f003" class="html-fig">Figure 3</a> except for 100 mM NaCl solution at various storage periods at 293 K (0 day: thick solid line, 2 days: larger dashed line, 4 days: smaller dashed line, 7 days: thin solid line, pure water: thin dotted line). (<b>b</b>) Apparent bubble diameter distributions in 100 mM NaCl solution 2 days after MNB generation (coarse dot bar, <span class="html-italic">n</span> = 40), and 4 days after MNB generation (fine dot bar, <span class="html-italic">n</span> = 36).</p> Full article ">Figure 5
<p>Storage time dependence of <span class="html-italic">D</span> in 100 mM NaCl solution at 293 K (solid circle). Open squares show <span class="html-italic">D</span> in pure water. Error bars are the standard error based on a normal distribution.</p> Full article ">Figure 6
<p>Time dependence of (<b>a</b>) DO concentration and (<b>b</b>) pH of the O<sub>2</sub> MNB in the solution including 0 mM (open diamond) and 10 mM NaCl (solid circle). The measurement uncertainties are within the size of each symbol.</p> Full article ">Figure 7
<p>Time dependence of the ζ-potential of the O<sub>2</sub> MNB solution including 10 mM NaCl (solid circle) and no additives (open diamond). Each error bar shows the standard deviation of the measurement.</p> Full article ">Figure 8
<p>TEM image of a MNB in 1 wt % NaCl solution. Scale bar shows 100 nm. Arrow marks the thin layer on the MNB.</p> Full article ">
1964 KiB  
Article
Characterization of Nanoparticle Dispersion in Red Blood Cell Suspension by the Lattice Boltzmann-Immersed Boundary Method
by Jifu Tan, Wesley Keller, Salman Sohrabi, Jie Yang and Yaling Liu
Nanomaterials 2016, 6(2), 30; https://doi.org/10.3390/nano6020030 - 5 Feb 2016
Cited by 41 | Viewed by 8586
Abstract
Nanodrug-carrier delivery in the blood stream is strongly influenced by nanoparticle (NP) dispersion. This paper presents a numerical study on NP transport and dispersion in red blood cell (RBC) suspensions under shear and channel flow conditions, utilizing an immersed boundary fluid-structure interaction model [...] Read more.
Nanodrug-carrier delivery in the blood stream is strongly influenced by nanoparticle (NP) dispersion. This paper presents a numerical study on NP transport and dispersion in red blood cell (RBC) suspensions under shear and channel flow conditions, utilizing an immersed boundary fluid-structure interaction model with a lattice Boltzmann fluid solver, an elastic cell membrane model and a particle motion model driven by both hydrodynamic loading and Brownian dynamics. The model can capture the multiphase features of the blood flow. Simulations were performed to obtain an empirical formula to predict NP dispersion rate for a range of shear rates and cell concentrations. NP dispersion rate predictions from the formula were then compared to observations from previous experimental and numerical studies. The proposed formula is shown to accurately predict the NP dispersion rate. The simulation results also confirm previous findings that the NP dispersion rate is strongly influenced by local disturbances in the flow due to RBC motion and deformation. The proposed formula provides an efficient method for estimating the NP dispersion rate in modeling NP transport in large-scale vascular networks without explicit RBC and NP models. Full article
(This article belongs to the Special Issue Nanomaterials for Biosensing Applications)
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Figure 1

Figure 1
<p>(<b>A</b>) Spring connected network cell membrane model. Kinematics for local stretching (<b>B</b>) and bending (<b>C</b>) modes of response.</p> Full article ">Figure 2
<p>The algorithm flow chart of immersed boundary method.</p> Full article ">Figure 3
<p>Interaction between nanoparticle (NP) and red blood cell (RBC) at shear rates of (<b>A</b>) 40 s<sup>−1</sup> (RBC tumbling) and (<b>B</b>) 200 s<sup>−1</sup> (RBC tank treading). The bold red lines outline the RBC membranes, while the green markers denote NPs. Flow streamlines are shown in the background.</p> Full article ">Figure 4
<p>NP dispersion rate as a function of shear rate. Error bars indicate the standard variance for three simulations. RBCs undergo tumbling motion at a low shear rate (<span class="html-italic">η</span>&lt; 40 s<sup>−1</sup>) and tank treading motion at a high shear rate (<math display="inline"> <semantics> <mi>η</mi> </semantics> </math> &gt; 200 s<sup>−1</sup>). In between, there is a transition region. Linear regression lines for the tumbling and tank treading regions are shown, as well.</p> Full article ">Figure 5
<p>Snapshots from a channel flow simulation for a cell-particle mixture with a hematocrit level of 23.5% and a shear rate of 200 s<sup>−1</sup> at 0.26 s (<b>A</b>) and 0.46 s (<b>B</b>). Fluid streamlines are shown in the background, while the yellow markers represent 100-nm nanoparticles. For illustration purposes, cells and particles are not shown to scale. A short movie of the simulation is provided in the <a href="#app1-nanomaterials-06-00030" class="html-app">Supplementary Materials</a>.</p> Full article ">Figure 6
<p>The NP fraction across the channel height for a hematocrit level of 23.5%. (<b>A</b>) NP fraction at <span class="html-italic">t</span> = 0, 0.26 s and 0.52 s for a shear rate of 200 s<sup>−1</sup>; and (<b>B</b>) NP fraction at <span class="html-italic">t</span> = 0.52 s for shear rates of 100 s<sup>−1</sup>, 200 s<sup>−1</sup>, 300 s<sup>−1</sup> and 500 s<sup>−1</sup>.</p> Full article ">Figure 7
<p>Dispersion rate of NPs in blood flow. (<b>A</b>) NP dispersion rate at different hematocrit (Ht) and shear rates; (<b>B</b>) relationship between dimensionless dispersion rate (<span class="html-italic">D<sub>r</sub></span>) and hematocrit (<span class="html-italic">H<sub>t</sub></span>). Error bars show the standard variance from three samples.</p> Full article ">Figure 8
<p>Comparison of the particle dispersion rate predicted from Equation (18) with the data reported in the literature. The dashed line is the prediction from Equation (18).</p> Full article ">
1678 KiB  
Article
Simultaneous Reduction and Functionalization of Graphene Oxide by 4-Hydrazinobenzenesulfonic Acid for Polymer Nanocomposites
by Song-Jie Qiao, Xiang-Nan Xu, Yang Qiu, He-Chong Xiao and Yue-Feng Zhu
Nanomaterials 2016, 6(2), 29; https://doi.org/10.3390/nano6020029 - 4 Feb 2016
Cited by 44 | Viewed by 8266
Abstract
Graphene oxide (GO) was functionalized and reduced simultaneously by a new reductant, 4-hydrazinobenzenesulfonic acid (HBS), with a one-step and environmentally friendly process. The hydrophilic sulfonic acid group in HBS was grafted onto the surface of GO through a covalent bond. The successful preparation [...] Read more.
Graphene oxide (GO) was functionalized and reduced simultaneously by a new reductant, 4-hydrazinobenzenesulfonic acid (HBS), with a one-step and environmentally friendly process. The hydrophilic sulfonic acid group in HBS was grafted onto the surface of GO through a covalent bond. The successful preparation of HBS reduced GO (HBS-rGO) was testified by scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopic (XPS) and thermogravimetric analysis (TGA). The interlayer space of HBS-rGO was increased to 1.478 nm from 0.751 nm for GO, resulting in a subdued Van der Waals’ force between layers and less possibility to form aggregations. The aqueous dispersibility of graphene was improved to 13.49 mg/mL from 0.58 mg/mL after the functionalization. The viscosity of the epoxy resin based HBS-rGO composite could be regulated by an adjustment of the content of HBS-rGO. This study provides a new and applicable approach for the preparation of hydrophilic functionalized graphene, and makes it possible for the application of graphene in some functional polymer nanocomposites, such as specialty water-based coatings. Full article
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<p>Reaction scheme for preparation of 4-hydrazinobenzenesulfonic acid (HBS) reduced graphene oxide (GO) (HBS-rGO).</p> Full article ">Figure 2
<p>Scanning electron microscope (SEM) images of (<b>a</b>) GO and (<b>b</b>) HBS-rGO.</p> Full article ">Figure 3
<p>The X-ray diffraction (XRD) patterns of (<b>a</b>) GO and (<b>b</b>) HBS-rGO.</p> Full article ">Figure 4
<p>The Raman spectroscopy of GO, HBS-rGO and grapheme.</p> Full article ">Figure 5
<p>The Fourier transform infrared spectra (FTIR) spectra of GO and HBS-rGO.</p> Full article ">Figure 6
<p>The X-ray photoelectron spectroscopic (XPS) spectra of GO and HBS-rGO: all elements survey scan of GO (<b>a</b>), HBS-rGO (<b>b</b>), C 1s survey scan of GO (<b>c</b>), HBS-rGO (<b>d</b>), (<b>e</b>) N 1s, and (<b>f</b>) S 2p for HBS-rGO.</p> Full article ">Figure 7
<p>Thermogravimetric analysis (TGA) measurements of GO and HBS-rGO.</p> Full article ">Figure 8
<p>(<b>a</b>) Digital images of graphene, GO and HBS-rGO aqueous solutions (1.5 mg/mL) after being kept for four weeks. (<b>b</b>) Aqueous dispersibility of graphene, GO and HBS-rGO.</p> Full article ">Figure 9
<p>The viscosity behavior of epoxy resin based composites.</p> Full article ">
1512 KiB  
Article
Spectroscopic and Electrochemical Studies of Imogolite and Fe-Modified Imogolite Nanotubes
by Carmen Castro, Nicolas Arancibia-Miranda, Cristina Acuña-Rougier, Mauricio Escudey and Federico Tasca
Nanomaterials 2016, 6(2), 28; https://doi.org/10.3390/nano6020028 - 2 Feb 2016
Cited by 10 | Viewed by 5268
Abstract
Carbon nanotubes and other forms of carbon nanoparticles, as well as metal nanoparticles have been widely used in film electrochemistry because they allow for the immobilization of larger amounts of catalyst (either biological or inorganic) on the top of the modified electrodes. Nevertheless, [...] Read more.
Carbon nanotubes and other forms of carbon nanoparticles, as well as metal nanoparticles have been widely used in film electrochemistry because they allow for the immobilization of larger amounts of catalyst (either biological or inorganic) on the top of the modified electrodes. Nevertheless, those nanoparticles present high costs of synthesis and of separation and purification that hamper their employment. On the other hand, imogolites (Im), with the general formula (OH)3Al2O3SiOH, are naturally-occurring nanomaterials, which can be obtained from glassy volcanic ash soils and can also be synthesized at mild conditions. In this research paper, we characterize through spectroscopic techniques (i.e., fourier transform infrared spectroscopy (FTIR) spectroscopy, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM)) synthetized Im and Fe-modified imogolite (Im(Fe)). Moreover, the Im and Im(Fe) were physically adsorbed on the top of a graphite electrode (GE) and were characterized electrochemically in the potential region ranging from −0.8 to 0.8 V vs. the saturated calomel electrode (SCE). When the film of the Im or of the Im(Fe) was present on the top of the electrode, the intensity of the charging/discharging current increased two-fold, but no redox activity in the absence of O2 could be appreciated. To show that Im and Im(Fe) could be used as support for catalysts, iron phthalocyanine (FePc) was adsorbed on the top of the Im or Im(Fe) film, and the electrocatalytic activity towards the O2 reduction was measured. In the presence of the Im, the measured electrocatalytic current for O2 reduction increased 30%, and the overpotential drastically decreased by almost 100 mV, proving that the Im can act as a good support for the electrocatalysts. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Scheme of the graphite electrode (GE) modified with imogolites (Im) or Im(Fe) and then with Im or Im(Fe) and FePc.</p> Full article ">Figure 2
<p>(<b>A</b>) Fourier transform infrared spectroscopy (FTIR) spectra of Im and Im(Fe); (<b>B</b>) X-ray diffraction (XRD) pattern of Im and Im(Fe); (<b>C</b>) Transmission electron microscopy (TEM) micrograph of Im; (<b>D</b>) TEM micrograph of Im(Fe).</p> Full article ">Figure 3
<p>Electrophoretic migration <span class="html-italic">vs.</span> pH curves for Im (squares) and Im(Fe) (circles). EM, electrophoretic migration.</p> Full article ">Figure 4
<p>(<b>A</b>) Cyclic voltammetry and polarization curves for the oxygen reduction reaction (ORR) (O<sub>2</sub> saturated conditions, dotted red line) of the graphite electrodes (GE) and GE modified with Im and with Im(Fe); (<b>B</b>) Cyclic voltammetry and polarization curves (O<sub>2</sub> saturated conditions, dotted red line) of the GE modified with FePc, Im-FePc and Im(Fe)-FePc. SCE, saturated calomel electrode.</p> Full article ">
5186 KiB  
Article
Extended Superspheres for Shape Approximation of Near Polyhedral Nanoparticles and a Measure of the Degree of Polyhedrality
by Susumu Onaka
Nanomaterials 2016, 6(2), 27; https://doi.org/10.3390/nano6020027 - 2 Feb 2016
Cited by 6 | Viewed by 6810
Abstract
Crystalline nanoparticles or nanoprecipitates with a cubic structure often have near polyhedral shapes composed of low-index planes with {100}, {111} and {110}. To consider such near polyhedral shapes, algebraic formulas of extended superspheres that can express intermediate shapes between spheres and various polyhedra [...] Read more.
Crystalline nanoparticles or nanoprecipitates with a cubic structure often have near polyhedral shapes composed of low-index planes with {100}, {111} and {110}. To consider such near polyhedral shapes, algebraic formulas of extended superspheres that can express intermediate shapes between spheres and various polyhedra have been presented. Four extended superspheres, (i) {100} regular-hexahedral; (ii) {111} regular-octahedral (iii) {110} rhombic-dodecahedral and (iv) {100}-{111}-{110} rhombicuboctahedral superspheres are treated in this study. A measure ∏ to indicate the degree of polyhedrality is presented to discuss shape transitions of the extended superspheres. As an application of ∏ superspherical coherent precipitate is shown. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The shape given by Equation (1) for <math display="inline"> <semantics> <mrow> <mi>p</mi> <mo>=</mo> <mn>8</mn> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>R</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 2
<p>Diagram showing the variations of polyhedra composed of {100}, {111} and {110} as the limiting shapes of the extended superspheres The parameters <span class="html-italic">a</span> and <span class="html-italic">b</span> are those for determining the ratios of the {100}, {111} and {110}. The points P, R and S respectively correspond to the {100} hexahedron, the {111} octahedron and the {110} dodecahedron. Polyhedra composed of one or two of the crystallographic planes can be shown around the quadrilateral surrounded as shown in the insets. The {100}-{111}-{110} polyhedra with different ratios of the three crystallographic planes are expressed inside of the quadrilateral.</p> Full article ">Figure 3
<p>The relationship between <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>=</mo> <mi>A</mi> <mo>/</mo> <msup> <mi>V</mi> <mrow> <mn>2</mn> <mo>/</mo> <mn>3</mn> </mrow> </msup> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mi mathvariant="sans-serif">η</mi> </semantics> </math> for the hexahedral, octahedral and dodecahedral superspheres respectively given by Equations (3)–(5) and rhombicuboctahedral (RCO) supersphere given by Equation (6) with <math display="inline"> <semantics> <mrow> <mi>a</mi> <mo>=</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <msqrt> <mn>2</mn> </msqrt> <mo>−</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> and <math display="inline"> <semantics> <mrow> <mi>b</mi> <mo>=</mo> <msqrt> <mn>2</mn> </msqrt> </mrow> </semantics> </math>. The results for the superspheres are shown with insets of the polyhedral shapes when <math display="inline"> <semantics> <mrow> <mi mathvariant="sans-serif">η</mi> <mo>=</mo> <msqrt> <mn>2</mn> </msqrt> </mrow> </semantics> </math>.</p> Full article ">Figure 4
<p>The relationship between <math display="inline"> <semantics> <mo>Π</mo> </semantics> </math> given by Equation (9) and <math display="inline"> <semantics> <mi mathvariant="sans-serif">η</mi> </semantics> </math> for the hexahedral, octahedral and dodecahedral and RCO superspheres, where <math display="inline"> <semantics> <mo>Π</mo> </semantics> </math> is a function of <math display="inline"> <semantics> <mi>N</mi> </semantics> </math>.</p> Full article ">Figure 5
<p>The shapes of the hexahedral, octahedral, dodecahedral and RCO superspheres at various values of <math display="inline"> <semantics> <mo>Π</mo> </semantics> </math>. The values in a parenthesis separated by a slash are those of <math display="inline"> <semantics> <mi>p</mi> </semantics> </math> (<b>left</b>) and <math display="inline"> <semantics> <mi mathvariant="sans-serif">η</mi> </semantics> </math> (<b>right</b>) for each shape.</p> Full article ">Figure 6
<p>The relationship between <math display="inline"> <semantics> <mo>Ξ</mo> </semantics> </math> and <math display="inline"> <semantics> <mi mathvariant="sans-serif">η</mi> </semantics> </math> for the hexahedral, octahedral and dodecahedral and RCO superspheres, where <math display="inline"> <semantics> <mo>Ξ</mo> </semantics> </math> is a function of the Steinitz number <math display="inline"> <semantics> <mi>S</mi> </semantics> </math>. It is interesting to note that this <math display="inline"> <semantics> <mrow> <mo>Ξ</mo> <mo>−</mo> <mi mathvariant="sans-serif">η</mi> </mrow> </semantics> </math> relation is very similar to the <math display="inline"> <semantics> <mrow> <mo>Π</mo> <mo>−</mo> <mi mathvariant="sans-serif">η</mi> </mrow> </semantics> </math> relation (<a href="#nanomaterials-06-00027-f004" class="html-fig">Figure 4</a>).</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic illustration showing a superspherical coherent precipitate in a matrix with a cubic structure. The precipitate has a purely dilatational misfit strains <math display="inline"> <semantics> <mrow> <msubsup> <mi mathvariant="sans-serif">ε</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> <mo>*</mo> </msubsup> <mo>=</mo> <msub> <mi mathvariant="sans-serif">δ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> <msup> <mi mathvariant="sans-serif">ε</mi> <mo>*</mo> </msup> </mrow> </semantics> </math> and causes elastic strains in the material containing the precipitate. (<b>b</b>) The precipitate-shape dependence of the elastic-strain energy shown by the relationship between the normalized elastic-strain energy <math display="inline"> <semantics> <mrow> <msub> <mi>E</mi> <mi mathvariant="normal">N</mi> </msub> </mrow> </semantics> </math> and the polyhedrality <math display="inline"> <semantics> <mo>Π</mo> </semantics> </math>. The results for the precipitate shapes of the hexahedral, octhedral, dodecahedral and RCO superspheres are shown.</p> Full article ">
2340 KiB  
Review
Manufacturing Techniques and Surface Engineering of Polymer Based Nanoparticles for Targeted Drug Delivery to Cancer
by Yichao Wang, Puwang Li, Thao Truong-Dinh Tran, Juan Zhang and Lingxue Kong
Nanomaterials 2016, 6(2), 26; https://doi.org/10.3390/nano6020026 - 1 Feb 2016
Cited by 178 | Viewed by 18329
Abstract
The evolution of polymer based nanoparticles as a drug delivery carrier via pharmaceutical nano/microencapsulation has greatly promoted the development of nano- and micro-medicine in the past few decades. Poly(lactide-co-glycolide) (PLGA) and chitosan, which are biodegradable and biocompatible polymers, have been approved by both [...] Read more.
The evolution of polymer based nanoparticles as a drug delivery carrier via pharmaceutical nano/microencapsulation has greatly promoted the development of nano- and micro-medicine in the past few decades. Poly(lactide-co-glycolide) (PLGA) and chitosan, which are biodegradable and biocompatible polymers, have been approved by both the Food & Drug Administration (FDA) and European Medicine Agency (EMA), making them ideal biomaterials that can be advanced from laboratory development to clinical oral and parental administrations. PLGA and chitosan encapsulated nanoparticles (NPs) have successfully been developed as new oral drug delivery systems with demonstrated high efficacy. This review aims to provide a comprehensive overview of the fabrication of PLGA and chitosan particulate systems using nano/microencapsulation methods, the current progress and the future outlooks of the nanoparticulate drug delivery systems. Especially, we focus on the formulations and nano/micro-encapsulation techniques using top-down techniques. It also addresses how the different phases including the organic and aqueous ones in the emulsion system interact with each other and subsequently influence the properties of the drug delivery system. Besides, surface modification strategies which can effectively engineer intrinsic physicochemical properties are summarised. Finally, future perspectives and potential directions of PLGA and chitosan nano/microencapsulated drug systems are outlined. Full article
(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Preparation of nanocapsules by emulsion diffusion method.</p> Full article ">Figure 2
<p>Preparation of nanoparticles (NPs) by salting out method.</p> Full article ">Figure 3
<p>Preparation of NPs by nanoprecipitation method.</p> Full article ">Figure 4
<p>Preparation of NPs by emulsion evaporation method.</p> Full article ">Figure 5
<p>Preparation of chitosan NPs by ion gelation technology.</p> Full article ">Figure 6
<p>Preparation of chitosan NPs by reverse micellar method.</p> Full article ">Figure 7
<p>Preparation of chitosan particulate systems by spray drying method.</p> Full article ">Figure 8
<p>Preparation of chitosan NPs by coacervation/precipitation method.</p> Full article ">Figure 9
<p>Schematic maps of chitosan modified poly(lactide-co-glycolide) nanoparticles (PLGA NPs) by (<b>a</b>) physical adsorption method and (<b>b</b>) chemical binding method. Reproduced with permission of [<a href="#B45-nanomaterials-06-00026" class="html-bibr">45</a>]. Copyright Springer, 2016.</p> Full article ">Figure 10
<p>(<b>a</b>) Formation of the PLGA-1, 3-diaminopropane-folic acid targeting drug delivery system. (<b>b</b>) Classification of targeting drug delivery system.</p> Full article ">Figure 11
<p>Schematic diagram of treatment chamber for gas plasma polymerization.</p> Full article ">Figure 12
<p>Preparation of galactosylated chitosan (GC).</p> Full article ">Figure 13
<p>Preparation of <span class="html-italic">N</span>-(2-hydroxyl)propyl-3-trimethylammonium chitosan chloride (HTCC).</p> Full article ">Figure 14
<p>Schematic representative of preparation of <span class="html-italic">O</span>-(2-hydroxyl)propyl-3-trimethylammonium chitosan chloride (O-HTCC).</p> Full article ">Figure 15
<p>Preparation of thiolated chitosan.</p> Full article ">
1487 KiB  
Article
Composites of Quasi-Colloidal Layered Double Hydroxide Nanoparticles and Agarose Hydrogels for Chromate Removal
by Gyeong-Hyeon Gwak, Min-Kyu Kim and Jae-Min Oh
Nanomaterials 2016, 6(2), 25; https://doi.org/10.3390/nano6020025 - 26 Jan 2016
Cited by 8 | Viewed by 5290
Abstract
Composite hydrogels were prepared that consisted of quasi-colloidal layered double hydroxide (LDH) nanoparticles and agarose via the electrophoretic method, starting from three different agarose concentrations of 0.5, 1, and 2 wt/v%. The composite hydrogel was identified to have a uniform distribution of LDH [...] Read more.
Composite hydrogels were prepared that consisted of quasi-colloidal layered double hydroxide (LDH) nanoparticles and agarose via the electrophoretic method, starting from three different agarose concentrations of 0.5, 1, and 2 wt/v%. The composite hydrogel was identified to have a uniform distribution of LDH nanoparticles in agarose matrix. Microscopic studies revealed that the composite hydrogel had a homogeneous quasi-colloidal state of LDHs, while the simple mixture of LDH powder and agarose hydrogels did not. It was determined that agarose concentration of the starting hydrogel did not significantly influence the amount of LDH that developed in the composite. The chromate scavenging efficiency of the composite hydrogel and corresponding agarose or mixture hydrogel was evaluated with respect to time, and chromate concentration. In general, the composite hydrogels exhibited much higher chromate removal efficacy compared with agarose or mixture hydrogels. Through estimating chromate adsorption by LDH moiety in the composite or mixture hydrogel, it was suggested that the agarose component facilitated the stability and dispersibility of the quasi-colloidal state of LDH nanoparticles in the composite resulting in high adsorption efficacy. From Freundlich isotherm adsorption fitting, composites were determined to possess beneficial cooperative adsorption behavior with a high adsorption coefficient. Full article
(This article belongs to the Special Issue Current Trends in Colloidal Nanocrystals)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Photographs and scanning electron microscopic (SEM) images of agarose only hydrogel (1 wt/v% agarose concentration, <b>A-1</b>) and Layered double hydroxide (LDH)-agarose composite hydrogel (1 wt/v% agarose concentration, <b>C-1</b>). For SEM images, both A-1 and C-1 were dehydrated to film.</p> Full article ">Figure 2
<p>X-ray diffraction (XRD) patterns of (<b>A</b>) calcined composites and (<b>B</b>) reconstructed ones for (<b>a</b>) LDH-agarose composite hydrogel (0.5 wt/v% agarose concentration, C-0.5), (<b>b</b>) LDH-agarose composite hydrogel (1 wt/v% agarose concentration, C-1) and (<b>c</b>) LDH-agarose composite hydrogel (2 wt/v% agarose concentration, C-2), respectively. XRD patterns of the calcined composite (<b>A</b>) showed a typical phase of periclase (JCPDS No. 71-1176), and those of reconstructed ones (<b>B</b>) exhibited the layered double hydroxide (LDH) phase (hydrotalcite, JCPDS No. 14-0191). The vertical lines under the XRD patterns are the corresponding JCPDS patterns.</p> Full article ">Figure 3
<p>Three-dimensional atomic force microscopic (AFM) images and corresponding line profiles along the double-headed arrow for (<b>a</b>) agarose only hydrogel (1 wt/v% agarose concentration, A-1), (<b>b</b>) LDH-agarose composite hydrogel (1 wt/v% agarose concentration, C-1) and (<b>c</b>) LDH-agarose mixture hydrogel (1 wt/v% agarose concentration, M-1), respectively. Single-headed arrows in (<b>b</b>) stand for singe LDH nanoparticles distributed in agarose matrix.</p> Full article ">Figure 4
<p>Time-dependent chromate removal efficacy (mg chromate/g dry weight) of agarose only (A), LDH-agarose mixture (M) and LDH-agarose composite (C) samples for (<b>a</b>) 0.5 wt/v%; (<b>b</b>) 1 wt/v%; and (<b>c</b>) 2 wt/v% agarose-based materials. The experiments were carried out at initial chromate concentration of 400 ppm and at pH ~7.5.</p> Full article ">Figure 5
<p>Isotherms of chromate removal efficacy (mg chromate/g dry weight) of agarose only (A), LDH-agarose mixture (M) and LDH-agarose composite (C) samples for (<b>a</b>) 0.5 wt/v%; (<b>b</b>) 1 wt/v%; and (<b>c</b>) 2 wt/v% agarose-based materials. The experiments were carried out at pH 7.2 ± 0.3 after 24 h.</p> Full article ">Figure 6
<p>Estimated chromate removal efficacy (μmol/g) by LDH moiety in LDH-agarose composite (C) and LDH-agarose mixture (M) samples at initial chromate concentration of (<b>a</b>) 50 ppm, (<b>b</b>) 100 ppm, (<b>c</b>) 200 ppm, and (<b>d</b>) 400 ppm, respectively. For calculation, chromate removal by C or M sample was subtracted by the chromate removal by agarose only at the same chromate concentration.</p> Full article ">
1976 KiB  
Article
A Nanostructured SERS Switch Based on Molecular Beacon-Controlled Assembly of Gold Nanoparticles
by Yansheng Li, Yaya Cheng, Liping Xu, Hongwu Du, Peixun Zhang, Yongqiang Wen and Xueji Zhang
Nanomaterials 2016, 6(2), 24; https://doi.org/10.3390/nano6020024 - 22 Jan 2016
Cited by 9 | Viewed by 6653
Abstract
In this paper, highly purified and stable gold nanoparticle (AuNP) dimers connected at the two ends of DNA linkage were prepared by a versatile method. A nanostructured, surface-enhanced Raman scattering (SERS) switching sensor system was fabricated based on the controlled organization of gold [...] Read more.
In this paper, highly purified and stable gold nanoparticle (AuNP) dimers connected at the two ends of DNA linkage were prepared by a versatile method. A nanostructured, surface-enhanced Raman scattering (SERS) switching sensor system was fabricated based on the controlled organization of gold nanoparticles (AuNPs) by a DNA nanomachine through the controlled formation/deformation of SERS “hotspots”. This strategy not only opens opportunities in the precise engineering of gap distances in gold-gold nanostructures in a highly controllable and reproducible fashion, but also provides a unique ability to research the origin of SERS and sequence-specific DNA detection. Full article
(This article belongs to the Special Issue Nanostructured Biosensors 2016)
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Figure 1

Figure 1
<p>Characterization of discrete DNA-AuNP conjugates: (<b>a</b>) Electrophoretic analysis (2.5% agarose gel) of ssDNA-bridged AuNP dimers formed from molecular beacon sequences with 15 nm AuNPs. Lane 1: Bare AuNP, as a reference; Lane 2: A mixture of AuNP with the two cyclic disulfide–modified DNA strands. (<b>b</b>) Typical transmission electron microscopy (TEM) image of AuNP dimers separated by agarose gel electrophoresis. (<b>c</b>) Typical TEM image of AuNP-DNA separated by agarose gel electrophoresis. (<b>d</b>) Typical TEM image of AuNP dimers produced by the traditional hybridization method with two complementary AuNP-DNA conjugates.</p> Full article ">Figure 2
<p>(<b>a</b>) TEM observation of AuNP dimers at “close” states and (<b>b</b>) AuNPs dimers at “open” states; (<b>c</b>) A histogram of the distance of the open form. The average distance was about 18.2 nm, which is coincident with the theoretical value for DNA 60 bases (~20 nm).</p> Full article ">Figure 3
<p>(<b>a</b>) SERS spectra of 4-aminothiophenol (ATP) molecules measured on nanostructured switch devices at “colse” (I) and “open” states (II), respectively. The spectra were recorded by using 633 nm laser lines. (<b>b</b>) A plot of the Raman intensity at 1078 cm<sup>−1</sup> for 4-ATP molecules as a function of the number of cycles. High and low Raman absorbance maxima values indicate the devices at the “close” and the “open” states, respectively.</p> Full article ">Figure 4
<p>(<b>a</b>) Demonstration of the structural changes of the DNA nanomachine after the addition of F1 and F2. (<b>b</b>) Fluorescence spectroscopy after the addition of F1 (black curve) and F2 (red curve). (<b>c</b>) Fluorescence intensity showing the reversible switching of the DNA nanoswitch.</p> Full article ">Figure 5
<p>Schematic representations of surface-enhanced Raman scattering (SERS) switch through the control of the distance between the two AuNPs by sequential addition of fueling/analytes sequences of F1 and F2.</p> Full article ">
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