Yield Stress Enhancement of a Ternary Colloidal Suspension via the Addition of Minute Amounts of Sodium Alginate to the Interparticle Capillary Bridges.

Capillary suspensions are ternary solid-liquid-liquid systems produced via the addition of a small amount of secondary fluid to the bulk fluid that contained the dispersed solid particles. The secondary fluid could exert strong capillary forces between the particles and dramatically change the rheological properties of the suspension. So far, research has focused on capillary suspensions that consist of additive-free fluids, whereas capillary suspensions with additives, particularly those of large molecular weight that are highly relevant for industrial purposes, have been relatively less studied. In this study, we performed a systematic analysis of the properties of capillary suspensions that consist of paraffin oil (bulk phase), water (secondary phase), and α-Al2O3 microparticles (particle phase), in which the aqueous secondary phase contained an important eco-friendly polymeric binder, sodium alginate (SA). It was determined that the yield stress of the suspension increased significantly with the increase in the SA content in the aqueous secondary phase, which was attributed to the synergistic effect of the capillary force and hydrogen bonding force that may be related to the increase in the number of capillary bridges. The amounts of SA used to induce a significant change in the yield stress in this study were very small (<0.02% of the total sample volume). The addition of Ca2+ ions to the SA-containing secondary phase further increased the yield stress with possible gelation of the SA chains-in the presence of excess Ca2+ ions, however, the yield stress decreased because of the microscopic phase separation that occurred in the aqueous secondary phase. The microstructures of the sintered porous materials that were produced by using capillary suspensions as precursors were qualitatively well correlated to the rheological behavior of the precursor suspensions, suggesting a new method for the subtle control of the microstructures of porous materials using the addition of minute amounts of polymeric additives.

Facile Synthesis of Monodispersed Cubic and Spherical Calcite Nanoparticles in the Presence of Cetyltrimethylammonium Bromide.

We report the synthesis of monodisperse calcium carbonate (CaCO3) (nano)particles having either a cubic or spherical structure by reacting calcium nitrate with either sodium carbonate or citric acid, respectively, in the presence of cetyltrimethylammonium bromide (CTAB) via the sonication method. For comparison, CaCO3 (nano)particles were synthesized by the same method in the absence of CTAB and also via the standard hydrothermal method using CTAB. The synthesized CaCO3 (nano)particles were analyzed by various physico-chemical characterization techniques such as X-ray diffraction (XRD), Fourier transform infra-red spectroscopy, thermogravimetric analysis, and scanning electron microscopy with energy-dispersive spectrometer. It was found that the CaCO3 (nano)particles were highly pure with high crystallinity and exhibited the calcite polymorph phase as revealed by the XRD analysis. In addition, the analytical results showed that the (nano)particles prepared in the presence of CTAB by the sonication method had high structural ordering and no agglomeration as compared to the (nano)particles prepared by the hydrothermal method. Therefore, our sonication method is a new way to prepare shape-controlled CaCO3 (nano)particles under mild reaction conditions.

Quantitation of Oxidative Stress Gene Expression in Human Cell Lines Treated with Water-Dispersible MnO Nanoparticles.

The objective of this study was to assess cytotoxicity of engineered MnO nanoparticles by quantifying the reactive oxygen species (ROS) related genes (glutathione S-transferase (GST) and catalase) using real time-polymerase chain reaction (RT-PCR) and molecular beacon (MB) technologies. Monodisperse MnO nanoparticles of 14 nm in size were synthesized by the encapsulation of polyethyleneglycol (PEG)-phospholipid shell around the MnO core to endow high water-dispersibility and biocompatibility. In vitro cytotoxicity was evaluated at different concentrations (10, 50 and 100 µg/ml) and incubation times (12, 24 and 48 h) with human cancer cell lines (glioblastoma, lung adenocarcinoma and neuroblastoma cells). Both genetic and cellular cytotoxic screening methods produced consistent results, showing that GST and catalase ROS gene expression was maximized in 24 h incubation at 100 µg/ml concentration of MnO nanoparticles for each cell line. However, the cytotoxicity effect of the PEG-phospholipid coated MnO nanoparticle was not significant compared with control experiments, demonstrating its high potential in the applications of nanomedicines for a diagnostic and therapeutic tool.

High-resolution three-photon biomedical imaging using doped ZnS nanocrystals.

Three-photon excitation is a process that occurs when three photons are simultaneously absorbed within a luminophore for photo-excitation through virtual states. Although the imaging application of this process was proposed decades ago, three-photon biomedical imaging has not been realized yet owing to its intrinsic low quantum efficiency. We herein report on high-resolution in vitro and in vivo imaging by combining three-photon excitation of ZnS nanocrystals and visible emission from Mn(2+) dopants. The large three-photon cross-section of the nanocrystals enabled targeted cellular imaging under high spatial resolution, approaching the theoretical limit of three-photon excitation. Owing to the enhanced Stokes shift achieved through nanocrystal doping, the three-photon process was successfully applied to high-resolution in vivo tumour-targeted imaging. Furthermore, the biocompatibility of ZnS nanocrystals offers great potential for clinical applications of three-photon imaging.

Design of a multi-dopamine-modified polymer ligand optimally suited for interfacing magnetic nanoparticles with biological systems.

We have designed a set of multifunctional and multicoordinating polymer ligands that are optimally suited for surface functionalizing iron oxide and potentially other magnetic nanoparticles (NPs) and promoting their integration into biological systems. The amphiphilic polymers are prepared by coupling (via nucleophilic addition) several amine-terminated dopamine anchoring groups, poly(ethylene glycol) moieties, and reactive groups onto a poly(isobutylene-alt-maleic anhydride) (PIMA) chain. This design greatly benefits from the highly efficient and reagent-free one-step reaction of maleic anhydride groups with amine-containing molecules. The availability of several dopamine groups in the same ligand greatly enhances the ligand affinity, via multiple coordination, to the magnetic NPs, while the hydrophilic and reactive groups promote colloidal stability in buffer media and allow subsequent conjugation with target biomolecules. Iron oxide nanoparticles ligand exchanged with these polymer ligands have a compact hydrodynamic size and exhibit enhanced long-term colloidal stability over the pH range of 4-12 and in the presence of excess electrolytes. Nanoparticles ligated with terminally reactive polymers have been easily coupled to target dyes and tested in live cell imaging with no measurable cytotoxicity. Finally, the resulting hydrophilic nanoparticles exhibit large and size-dependent r2 relaxivity values.

Single step isolation and activation of primary CD3+ T lymphocytes using alcohol-dispersed electrospun magnetic nanofibers.

Electrospun polymer nanofibers with entrapped magnetic nanoparticles (magnetic NP-NF) represent a novel scaffold substrate that can be functionalized for single-step isolation and activation of specific lymphocyte subsets. Using a surface-embedded T cell receptor ligand/trigger (anti-CD3 monoclonal antibody), we demonstrate, as proof of principle, the use of magnetic NP-NF to specifically isolate, enrich, and activate CD3(+) T cells from a heterogeneous cell mixture, leading to preferential expansion of CD8(+)CD3(+) T cells. The large surface area, adjustable antibody density, and embedded paramagnetic properties of the NP-NF permitted enhanced activation and expansion; its use represents a strategy that is amenable to an efficient selection process for adoptive cellular therapy as well as for the isolation of other cellular subsets for downstream translational applications.

On the pH-dependent quenching of quantum dot photoluminescence by redox active dopamine.

We investigated the charge transfer interactions between luminescent quantum dots (QDs) and redox active dopamine. For this, we used pH-insensitive ZnS-overcoated CdSe QDs rendered water-compatible using poly (ethylene glycol)-appended dihydrolipoic acid (DHLA-PEG), where a fraction of the ligands was amine-terminated to allow for controlled coupling of dopamine-isothiocyanate onto the nanocrystal. Using this sample configuration, we probed the effects of changing the density of dopamine and the buffer pH on the fluorescence properties of these conjugates. Using steady-state and time-resolved fluorescence, we measured a pronounced pH-dependent photoluminescence (PL) quenching for all QD-dopamine assemblies. Several parameters affect the PL loss. First, the quenching efficiency strongly depends on the number of dopamines per QD-conjugate. Second, the quenching efficiency is substantially increased in alkaline buffers. Third, this pH-dependent PL loss can be completely eliminated when oxygen-depleted buffers are used, indicating that oxygen plays a crucial role in the redox activity of dopamine. We attribute these findings to charge transfer interactions between QDs and mainly two forms of dopamine: the reduced catechol and oxidized quinone. As the pH of the dispersions is changed from acidic to basic, oxygen-catalyzed transformation progressively reduces the dopamine potential for oxidation and shifts the equilibrium toward increased concentration of quinones. Thus, in a conjugate, a QD can simultaneously interact with quinones (electron acceptors) and catechols (electron donors), producing pH-dependent PL quenching combined with shortening of the exciton lifetime. This also alters the recombination kinetics of the electron and hole of photoexcited QDs. Transient absorption measurements that probed intraband transitions supported those findings where a simultaneous pronounced change in the electron and hole relaxation rates was measured when the pH was changed from acidic to alkaline.

Poly(ethylene glycol)-based multidentate oligomers for biocompatible semiconductor and gold nanocrystals.

We have developed a new set of multifunctional multidentate OligoPEG ligands, each containing a central oligomer on which were laterally grafted several short poly(ethylene glycol) (PEG) moieties appended with either thioctic acid (TA) or terminally reactive groups. Reduction of the TAs (e.g., in the presence of NaBH(4)) provides dihydrolipoic acid (DHLA)-appended oligomers. Here the insertion of PEG segments in the ligand structure promotes water solubility and reduces nonspecific interactions, while TA and DHLA groups provide multidentate anchoring onto Au nanoparticles (AuNPs) and ZnS-overcoated semiconductor quantum dots (QDs), respectively. The synthetic route involves simple coupling chemistry using N,N-dicylohexylcarbodiimide (DCC). Water-soluble QDs and AuNPs capped with these ligands were prepared via cap exchange. As prepared, the nanocrystals dispersions were aggregation-free, homogeneous, and stable for extended periods of time over pH ranging from 2 to 14 and in the presence of excess electrolyte (2 M NaCl). The new OligoPEG ligands also allow easy integration of tunable functional and reactive groups within their structures (e.g., azide or amine), which imparts surface functionalities to the nanocrystals and opens up the possibility of bioconjugation with specific biological molecules. The improved colloidal stability combined with reactivity offer the possibility of using the nanocrystals as biological probes in an array of complex and biologically relevant media.

Rapid and efficient protein digestion using trypsin-coated magnetic nanoparticles under pressure cycles.

Trypsin-coated magnetic nanoparticles (EC-TR/NPs), prepared via a simple multilayer random crosslinking of the trypsin molecules onto magnetic nanoparticles, were highly stable and could be easily captured using a magnet after the digestion was complete. EC-TR/NPs showed a negligible loss of trypsin activity after multiple uses and continuous shaking, whereas the conventional immobilization of covalently attached trypsin on NPs resulted in a rapid inactivation under the same conditions due to the denaturation and autolysis of trypsin. A single model protein, a five-protein mixture, and a whole mouse brain proteome were digested at atmospheric pressure and 37°C for 12 h or in combination with pressure cycling technology at room temperature for 1 min. In all cases, EC-TR/NPs performed equally to or better than free trypsin in terms of both the identified peptide/protein number and the digestion reproducibility. In addition, the concomitant use of EC-TR/NPs and pressure cycling technology resulted in very rapid (∼1 min) and efficient digestions with more reproducible digestion results.

Large-scale synthesis of uniform and extremely small-sized iron oxide nanoparticles for high-resolution T1 magnetic resonance imaging contrast agents.

Uniform and extremely small-sized iron oxide nanoparticles (ESIONs) of < 4 nm were synthesized via the thermal decomposition of iron-oleate complex in the presence of oleyl alcohol. Oleyl alcohol lowered the reaction temperature by reducing iron-oleate complex, resulting in the production of small-sized nanoparticles. XRD pattern of 3 nm-sized nanoparticles revealed maghemite crystal structure. These nanoparticles exhibited very low magnetization derived from the spin-canting effect. The hydrophobic nanoparticles can be easily transformed to water-dispersible and biocompatible nanoparticles by capping with the poly(ethylene glycol)-derivatized phosphine oxide (PO-PEG) ligands. Toxic response was not observed with Fe concentration up to 100 µg/mL in MTT cell proliferation assay of POPEG-capped 3 nm-sized iron oxide nanoparticles. The 3 nm-sized nanoparticles exhibited a high r(1) relaxivity of 4.78 mM(-1) s(-1) and low r(2)/r(1) ratio of 6.12, demonstrating that ESIONs can be efficient T(1) contrast agents. The high r(1) relaxivities of ESIONs can be attributed to the large number of surface Fe(3+) ions with 5 unpaired valence electrons. In the in vivo T(1)-weighted magnetic resonance imaging (MRI), ESIONs showed longer circulation time than the clinically used gadolinium complex-based contrast agent, enabling high-resolution imaging. High-resolution blood pool MR imaging using ESIONs enabled clear observation of various blood vessels with sizes down to 0.2 mm. These results demonstrate the potential of ESIONs as T(1) MRI contrast agents in clinical settings.

Analog Memristive Characteristics of Square Shaped Lanthanum Oxide Nanoplates Layered Device.

Square-shaped or rectangular nanoparticles (NPs) of lanthanum oxide (LaOx) were synthesized and layered by convective self-assembly to demonstrate an analog memristive device in this study. Along with non-volatile analog memory effect, selection diode property could be co-existent without any implementation of heterogeneous multiple stacks with ~1 µm thick LaOx NPs layer. Current-voltage (I-V) behavior of the LaOx NPs resistive switching (RS) device has shown an evolved current level with memristive behavior and additional rectification functionality with threshold voltage. The concurrent memristor and diode type selector characteristics were examined with electrical stimuli or spikes for the duration of 10-50 ms pulse biases. The pulsed spike increased current levels at a read voltage of +0.2 V sequentially along with ±7 V biases, which have emulated neuromorphic operation of long-term potentiation (LTP). This study can open a new application of rare-earth LaOx NPs as a component of neuromorphic synaptic device.

In vitro cytotoxicity screening of water-dispersible metal oxide nanoparticles in human cell lines.

In this study, we present in vitro cytotoxicity of iron oxide (Fe(3)O(4)) and manganese oxide (MnO) using live/dead cell assay, lactate dehydrogenase assay, and reactive oxygen species detection with variation of the concentration of nanoparticles (5-500 microg/ml), incubation time (18-96 h), and different human cell lines (lung adenocarcinoma, breast cancer cells, and glioblastoma cells). The surface of nanoparticles is modified with polyethyleneglycol-derivatized phospholipid to enhance the biocompatibility, water-solubility, and stability under an aqueous media. While the cytotoxic effect was negligible for 18 h incubation even at highest concentration of 500 microg/ml, MnO nanoparticle represented higher level of toxicity than those of Fe(3)O(4) and the commercial medical contrast reagent, Feridex after 2 and 4 day incubation time. However, the cytotoxicity of Fe(3)O(4) is equivalent or better than Feridex based on the live/dead cell viability assay. The engineered MnO and Fe(3)O(4) exhibited excellent stability compared with Feridex for a prolonged incubation time.

Beta-glucosidase coating on polymer nanofibers for improved cellulosic ethanol production.

Beta-glucosidase (betaG) can relieve the product inhibition of cellobiose in the cellulosic ethanol production by converting cellobiose into glucose. For the potential recycled uses, betaG was immobilized and stabilized in the form of enzyme coating on polymer nanofibers. The betaG coating (EC-betaG) was fabricated by crosslinking additional betaG molecules onto covalently attached betaG molecules (CA-betaG) via glutaraldehyde treatment. The initial activity of EC-betaG was 36 times higher than that of CA-betaG. After 20 days of incubation under shaking, CA-betaG and EC-betaG retained 33 and 91% of each initial activity, respectively. Magnetic nanofibers were also used for easy recovery and recycled uses of betaG coating. It is anticipated that the recycled uses of highly active and stable betaG coating can improve the economics of cellulosic ethanol production so long as economical materials are employed as a host of enzyme immobilization.

Bulk Nanoencapsulation of Phase Change Materials (PCMs) via Spontaneous Spreading of a UV-Curable Prepolymer.

Phase change materials (PCMs) have received considerable attention for various latent heat storage systems for efficient thermal energy utilization. Herein, a facile and fast method for the bulk nanoencapsulation of organic PCMs is proposed, based on the thermodynamically spontaneous spreading phenomenon of three immiscible liquid phases. In this approach, a complete engulfing of PCM nanodroplets (core phase) by immiscible prepolymer droplets (coating phase), both of which are bulk-dispersed in another immiscible medium (continuous phase), is thermodynamically driven by the relation between the surface energies of the core, coating, and continuous phases. To demonstrate the proposed method, melted n-docosane (PCM, core phase) nanodroplets are completely engulfed within a couple of minutes by immiscible polyethylene glycol diacrylate (PEGDA, coating phase) in an aqueous poly(vinyl alcohol) solution (continuous phase), and the PEGDA layer quickly cross-linked upon UV irradiation to form a rigid shell protecting the PCM core. As-produced PCM nanocapsules display promising heat storage and release performances as well as high durability in repeated heating-cooling cycles in both dry and wet states. The proposed process may serve as a useful platform for bulk production of PCM nanocapsules with various core and shell compositions in a facile, fast, and scalable way.

Photopolymerization-Based Synthesis of Uniform Magnetic Hydrogels and Colorimetric Glucose Detection.

Magnetic hydrogels have been commonly used in biomedical applications. As magnetite nanoparticles (MNPs) exhibit peroxidase enzyme-like activity, magnetic hydrogels have been actively used as signal transducers for biomedical assays. Droplet microfluidics, which uses photoinitiated polymerization, is a preferred method for the synthesis of magnetic hydrogels. However, light absorption by MNPs makes it difficult to obtain fully polymerized and homogeneous magnetic hydrogels through photoinitiated polymerization. Several methods have been reported to address this issue, but few studies have focused on investigating the light absorption properties of photoinitiators. In this study, we developed a simple method for the synthesis of poly(ethylene glycol) (PEG)-based uniform magnetic hydrogels that exploits the high ultraviolet absorption of a photoinitiator. Additionally, we investigated this effect on shape deformation and structural uniformity of the synthesized magnetic hydrogels. Two different photoinitiators, Darocur 1173 and lithium phenyl (2,4,6-trimethylbenzoyl) phosphinate (LAP), with significantly different UV absorption properties were evaluated based on the synthesis of magnetic hydrogels. The magnetic characteristics of the PEG-stabilized MNPs in hydrogels were investigated with a vibrating sample magnetometer. Finally, the colorimetric detection of hydrogen peroxide and glucose was conducted based on the enzyme-like property of MNPs and repeated several times to observe the catalytic activity of the magnetic hydrogels.

Wrap-bake-peel process for nanostructural transformation from beta-FeOOH nanorods to biocompatible iron oxide nanocapsules.

The thermal treatment of nanostructured materials to improve their properties generally results in undesirable aggregation and sintering. Here, we report on a novel wrap-bake-peel process, which involves silica coating, heat treatment and finally the removal of the silica layer, to transform the phases and structures of nanostructured materials while preserving their nanostructural characteristics. We demonstrate, as a proof-of-concept, the fabrication of water-dispersible and biocompatible hollow iron oxide nanocapsules by applying this wrap-bake-peel process to spindle-shaped akagenite (beta-FeOOH) nanoparticles. Depending on the heat treatment conditions, hollow nanocapsules of either haematite or magnetite were produced. The synthesized water-dispersible magnetite nanocapsules were successfully used not only as a drug-delivery vehicle, but also as a T2 magnetic resonance imaging contrast agent. The current process is generally applicable, and was used to transform heterostructured FePt nanoparticles to high-temperature face-centred-tetragonal-phase FePt alloy nanocrystals.

Synthesis of mesoporous lanthanum hydroxide with enhanced adsorption performance for phosphate removal.

Phosphate is a ubiquitous pollutant in aquatic systems, and increasingly stringent post-treatment phosphate effluent standards necessitate increasingly efficient removal techniques. In this study, mesoporous lanthanum hydroxide (MLHO) was synthesized by a hard-template method using ordered mesoporous silica, and its potential as an adsorbent for high-efficiency phosphate removal in aqueous solutions was tested. The porosity characteristics of MLHOs were controlled by adjusting the template structure and synthesis conditions. MLHO adsorbents showed great potential for phosphate removal from solutions containing both high and low initial phosphate concentrations. The phosphate adsorption capacity of MLHO strongly depended on its surface area as this process was governed by monolayer adsorption. Moreover, the phosphate removal performance of MLHO was affected by its structural properties. MLHO showed a high adsorption capacity of 109.41 mg P g-1 at 28 °C (q m by the Langmuir isotherm model). Further, it showed ultrafast adsorption in a solution with low initial concentration of 2 mg P/L; within the first 10 min, 99.8% of phosphate was removed, and the phosphorus concentration remaining in the solution dramatically reduced to 4 µg P/L. These findings suggest that MLHO adsorbent is a good candidate for rapid and efficient low-concentration phosphate removal to meet the increasingly stringent discharge standards for wastewater treatment plants.

Simple and generalized synthesis of oxide-metal heterostructured nanoparticles and their applications in multimodal biomedical probes.

Heterostructured nanoparticles composed of metals and Fe3O4 or MnO were synthesized by thermal decomposition of mixtures of metal-oleate complexes (for the oxide component) and metal-oleylamine complexes (for the metal component). The products included flowerlike-shaped nanoparticles of Pt-Fe3O4 and Ni-Fe3O4 and snowmanlike-shaped nanoparticles of Ag-MnO and Au-MnO. Powder X-ray diffraction patterns showed that these nanoparticles were composed of face-centered cubic (fcc)-structured Fe3O4 or MnO and fcc-structured metals. The relaxivity values of the Au-MnO and Au-Fe3O4 nanoparticles were similar to those of the MnO and Fe3O4 nanoparticles, respectively. Au-Fe3O4 heterostructured nanoparticles conjugated with two kinds of 12-base oligonucleotide sequences were able to sense a complementary 24-mer sequence, causing nanoparticle aggregation. This hybridization-mediated aggregation was detected by the overall size increase indicated by dynamic light scattering data, the red shift of the surface plasmon band of the Au component, and the enhancement of the signal intensity of the Fe3O4 component in T2-weighted magnetic resonance imaging.

Simple synthesis of functionalized superparamagnetic magnetite/silica core/shell nanoparticles and their application as magnetically separable high-performance biocatalysts.

Uniformly sized silica-coated magnetic nanoparticles (magnetite@silica) are synthesized in a simple one-pot process using reverse micelles as nanoreactors. The core diameter of the magnetic nanoparticles is easily controlled by adjusting the w value ([polar solvent]/[surfactant]) in the reverse-micelle solution, and the thickness of the silica shell is easily controlled by varying the amount of tetraethyl orthosilicate added after the synthesis of the magnetite cores. Several grams of monodisperse magnetite@silica nanoparticles can be synthesized without going through any size-selection process. When crosslinked enzyme molecules form clusters on the surfaces of the magnetite@silica nanoparticles, the resulting hybrid composites are magnetically separable, highly active, and stable under harsh shaking conditions for more than 15 days. Conversely, covalently attached enzymes on the surface of the magnetite@silica nanoparticles are deactivated under the same conditions.

Versatile PEG-derivatized phosphine oxide ligands for water-dispersible metal oxide nanocrystals.

We report the simple synthesis of poly(ethylene glycol)(PEG)-derivatized phosphine oxide ligands for water-dispersible metal oxide nanocrystals.