Core-shell Nanocapsules Research Articles

Diffusion and Molecular Exchange in Hollow Core-Shell Silica Nanoparticles.

The diffusion behavior of small molecules in hollow core-shell nanocapsules was studied using pulsed field gradient NMR. By purposefully selecting the liquid saturating the hollow core and the porous shell and the solvent between the nanocapsules, two different situations corresponding to the excluded and admitted molecular exchange between the intra- and intercapsule liquids at the external boundary of the nanoparticles were covered. In the former case, corresponding to the reflective boundary condition for the molecules approaching the nanocapsule boundary, restricted diffusion in the complex pore space formed by the hollow core and the mesoporous shell was observed. The time-dependent diffusivities measured in the experiment were inter-related with the geometry of the intraparticle pore space. The thus assessed structural information was found to be in a good agreement with that provided by electron microscopy. In the case of the molecular exchange occurring between the two pools of molecules in the nanocapsules and between them, the diffusive dynamics of only the molecules remaining in the nanocapsules during the entire observation times was studied.

Novel Core–Shell Nanocapsules for the Tunable Delivery of Bioactive <I>rh</I>EGF: Formulation, Characterization and Cytocompatibility Studies

Novel Core–Shell Nanocapsules for the Tunable Delivery of Bioactive <I>rh</I>EGF: Formulation, Characterization and Cytocompatibility Studies

Polyelectrolyte-coated nanocapsules containing undecylenic acid: Synthesis, biocompatibility and neuroprotective properties

The main objectives of the present study were to investigate the biocompatibility of polyelectrolyte-coated nanocapsules and to evaluate the neuroprotective action of the nanoencapsulated water-insoluble neuroprotective drug—undecylenic acid (UDA), in vitro. Core-shell nanocapsules were synthesized using nanoemulsification and the layer-by-layer (LbL) technique (by saturation method). The average size of synthesized nanocapsules was around 80nm and the concentration was 2.5×1010particles/ml. Their zeta potential values ranged from less than −30mV for the ones with external polyanion layers through −4mV for the PEG-ylated layers to more than 30mV for the polycation layers. Biocompatibility of synthesized nanocarriers was evaluated in the SH-SY5Y human neuroblastoma cell line using cell viability/toxicity assays (MTT reduction, LDH release). The results obtained showed that synthesized nanocapsules coated with PLL and PGA (also PEG-ylated) were non-toxic to SH-SY5Y cells, therefore, they were used as nanocarriers for UDA. Moreover, studies with ROD/FITC-labeled polyelectrolytes demonstrated approximately 20% cellular uptake of synthetized nanocapsules. Further studies showed that nanoencapsulated form of UDA was biocompatible and protected SH-SY5Y cells against the staurosporine-induced damage in lower concentrations than those of the same drug added directly to the culture medium. These data suggest that designed nanocapsules might serve as novel, promising delivery systems for neuroprotective agents.

Interfacial click chemistry for improving both dextran shell density and stability of biocompatible nanocapsules

Dextran-covered nanocapsules (NCs) have been obtained by emulsion-evaporation method coupled with an in situ click Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction occurring at liquid/liquid interface. To assure biocompatibility and biodegradability of NCs, α-alkyne PLA was chosen as inner shell and Miglyol 810 (M810) as oily core. NCs were covered by a hydrophilic superficial layer of dextran modified by azide-terminated 6-carbon aliphatic side chains, so-called DexN3. DexN3 was dissolved in the aqueous phase, but during emulsion process it migrated at the interface to act both as stabilizer and as reactant. Click reaction occurred at the oil-in-water interface between azide functions from DexN3 and alkyne groups of PLA present in the organic phase. Influence of different parameters, such as catalyst system or sonication conditions, has been studied on CuAAC reaction efficiency. CuSO4/AAsc was proven to be the most efficient catalyst. NCs characteristics in terms of particle size distribution, dextran coverage, colloidal stability in presence of salt and of SDS (competitive surfactant) as well as their morphology have been investigated. Core–shell NCs were obtained with various M810 content. Covalent linkages between PLA shell and dextran coverage improved colloidal stability of NCs, even in presence of SDS but also increased dextran density and thickness, in comparison to non-clicked NCs.

Fabrication of superstable gold nanorod–carbon nanocapsule as a molecule loading material

In this work, we fabricated a monodisperse nanocomposite by coating gold nanorods (AuNRs) with a layer of biocompatible, stable carbon, obtaining AuNR@Carbon core–shell nanocapsules, which without any functionalization could be used as a molecule loading material due to its high surface areas. In this system, the AuNR core had a high-absorption cross section for conversion of near-infrared light to heat, which could be explored for local hyperthermia. The carbon shell, which was biocompatible and stable even under concentrated acidic and alkaline conditions, was able to adsorb molecules with π–π interactions or electrostatic interactions. In comparison with AuNR@SiO2, AuNR@Carbon nanocapsules demonstrate the following merits: (1) simple and green synthesis method, (2) far more stable with respect to high-temperature stability and (3) larger molecule loading capacity, which indicate great potential in the biomedical applications.

Synthesis and Characterization of Poly(Acrylonitrile-co-Vinylacetate)/Fe2O3@PEDOT Core-Shell Nanocapsules and Nanofibers

P(AN-co-VAc)/Fe2O3 core-shell nanocapsules were synthesized by miniemulsion polymerization and P(AN-co-VAc)/Fe2O3@PEDOT core-shell structure was constituted by oxidative polymerization. Homogeneous nanofibers were obtained from the core-shell nanocapsules. Characterizations were performed by XRD, GPC, UV-vis, and FTIR-ATR. SEM, AFM, and TEM. Molecular weight and Tg of the nanocapsules were effected by the increase in γ-Fe2O3 NPs. Nanofiber resistance (Rnfb) drastically decreased from 2700 to 110 kΩ.cm2 by the inclusion of γ-Fe2O3 NPs into the nanocapsules 8.3 kΩ.cm2 obtained after coating with PEDOT. The electrochemical Impedance results were fitted to models of [R (Q(R (CR)))] and [R (Q(R (QR)))], respectively.

Magnetic Core–Shell Nanocapsules with Dual‐Targeting Capabilities and Co‐Delivery of Multiple Drugs to Treat Brain Gliomas

Lactoferrin (Lf)-tethered magnetic double emulsion nanocapsules (Lf-MDCs) are assembled from polyvinyl alcohol (PVA), polyacrylic acid (PAA), and iron oxide (IO) nanoparticles. The core-shell nanostructure of the Lf-MDCs (particle diameters from 100 to 150 nm) can simultaneously accommodate a hydrophilic drug, doxorubicin (Dox), and a hydrophobic drug, curcumin (Cur), in the core and shell, respectively, of the nanocapsules for an efficient drug delivery system. The release patterns of the two drugs can be regulated by manipulating the surface charges and drug-loading ratios, providing the capability for a stepwise adjuvant release to treat cancer cells. The results demonstrate that the dual (Dox+Cur)-drug-loaded nanocapsule can be effectively delivered into RG2 glioma cells to enhance the cytotoxicity against the cells through a synergistic effect. The combined targeting, i.e., magnetic guidance and incorporation of Lf ligands, of these Lf-MDCs results in significantly elevated cellular uptake in the RG2 cells that overexpress the Lf receptor. Interestingly, an intravenous injection of the co-delivered chemotherapeutics follows by magnetic targeting in brain tumor-bearing mice not only achieve high accumulation at the targeted site but also more efficiently suppress cancer growth in vivo than does the delivery of either drug alone.

Ni/amorphous CuO core–shell nanocapsules with enhanced electrochemical performances

A new type of core–shell nanocapsules with Ni nanoparticles as cores and amorphous CuO as shells have been synthesized through the arc-discharge method and subsequently annealing process. Amorphous CuO nanoshells lead to the improved stability and electrochemical performances. When evaluated as anode materials for lithium-ion batteries, the Ni/amorphous CuO nanocapsules deliver an initial discharge capacity of 1238.4 mAh g−1 at 100 mA g−1 and maintain a higher reversible capacity of 673.4 mAh g−1 over 100 cycles, compared to the Ni/crystalline CuO nanocapsules (392 mAh g−1). The feasibility of this material in lithium-ion batteries will offer guidelines for the future design of new materials with optimum properties and beneficial structural elements to realize improvements in electrochemical performances.

Synthesis and properties of phase change material-polypyrrole core-shell nanocapsules via Fe3+-oxidative miniemulsion polymerization

Synthesis and properties of phase change material-polypyrrole core-shell nanocapsules via Fe3+-oxidative miniemulsion polymerization

Supramolecular Core–Shell Nanosilica@Liposome Nanocapsules for Drug Delivery

The fabrication of core-shell structural nanosilica@liposome nanocapsules as a drug delivery vehicle is reported. SiO(2) nanoparticles are encapsulated within liposomes by a W/O/W emulsion approach to form supramolecular assemblies with a core of colloidal particles enveloped by a lipid bilayer shell. A nanosilica core provides charge compensation and architectural support for the lipid bilayer, which significantly improves their physical stability. A preliminary application of these core-shell nanocapsules for hemoglobin (Hb) delivery is described. Through the H-bonding interaction between the hydroxyl groups on nanosilicas and the amino nitrogens of Hb, Hb-SiO(2) nanocomplexes in which the saturated adsorption amount of Hb on SiO(2) is 0.47 g g(-1) are coated with lipids to generate core-shell Hb-SiO(2)@liposome nanocapsules with mean diameters of 60-500 nm and Hb encapsulation efficiency of 48.4-87.9%. Hb-SiO(2)@liposome supramolecular nanovehicles create a mode of delivery that stabilizes the encapsulated Hb and achieves long-lasting release, thereby improving the efficacy of the drug. Compared with liposome-encapsulated Hb and Hb-loaded SiO(2) particles, such core-shell nanovehicles show substantially enhanced release performance of Hb in vitro. This finding opens up a new window of liposome-based formulations as drug delivery nanovehicles for widespread pharmaceutical applications.

Preparation of core-shell polymeric nanocapsules containing liquid cores via redox interfacial-initiated microemulsion polymerization

AbstractIn this work, polystyrene (PSt) nanocapsules were successfully prepared by one-stage redox Interfacial-initiated inversed micro-emulsion polymerization of styrene (St), the cumene hydroperoxide (CHPO) and tetraethylenepentamine (TEPA) as the redox initiation pairs. The water-soluble TEPA acted as the reducing component and the oil-soluble CHPO as the oxidant component of the redox initiation system. The primary radicals were produced mainly at the oil/water interface to initiate the polymerization of styrene (St). Core-shell polymeric PSt nanocapsules were obtained by one-stage polymerization via this method, which was supported by the techniques of transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The particle size and polydispersity index (PDI) of nanocapsules were determined by dynamic light scattering (DLS). The results demonstrated that interfacial-initiated inversed microemulsion polymerization to form core-shell nanocapsules containing liquid cores by one-stage is successful.

Self‐Assembled Core–Shell Vascular‐Targeted Nanocapsules for Temporal Antivasculature and Anticancer Activities

A biocompatible core-shell nanocapsule is fabricated to target tumor vascular endothelial cells where it releases anti-angiogenesis and anticancer drugs sequentially. The fabrication of the core-shell nanocapsule is accomplished through a robust double self-assembly procedure: the hydrophobic polymeric core is first precipitated to encapsulate a poorly water-soluble anticancer drug paclitaxel (PTX) with the assistance of lecithin and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[carboxy(polyethylene glycol)2000] (DSPE-PEG) self-assembled in aqueous phase. Another lipid layer self-assembled around the above hydrophobic core is formed to load a second drug combretastatin A4 (CA4) as a vascular disrupting agent in the lipid layer. The lipid layer serves both as a depot for CA4, as well as a molecular fence to sustain the release of PTX from the polymeric core. The size of the resultant nanocapsule can be fine-turned by slightly adjusting the preparation conditions from several tens of nanometer to one hundred nanometers. The uptake of this nanocapsule by human umbilical vein endothelial cells (HUVEC) is efficient, and the two loaded drugs maintain their respective therapeutic potency. The time-dependent sequential release of these two drugs over a time difference of 36 h results in temporal ablation of endothelial cells and cancer cells. This self-assembled delivery system could serve as a universal prototype that can be applied for other combinatorial temporal drug delivery.

Chitosan nanocapsules: Effect of chitosan molecular weight and acetylation degree on electrokinetic behaviour and colloidal stability

In recent years, chitosan nanocapsules have shown promising results as carriers for oral drug or peptide delivery. The success in their applicability strongly depends on the stability of these colloidal systems passing through the digestive tract. In gastric fluids, clear stability comes from the high surface charge density of the chitosan shell, which is completely charged at acidic pH values. However, in the intestinal fluid (where the pH is almost neutral) the effective charge of these nanocapsules approaches zero, and the electrostatic forces cannot provide any stabilization. Despite the lack of surface charge, chitosan nanocapsules remain stable in simulated intestinal fluids. Recently, we have demonstrated that this anomalous stability (at zero charge) is owed to short-range repulsive forces that appear between hydrophilic particles when immersed in saline media. The present work examines the influence of the chitosan hydrophobicity, as well as molecular weight, in the stability of different chitosan nanocapsules. A study has been made of the size, polydispersity, electrophoretic mobility, and colloidal stability of eight core–shell nanocapsule systems, in which the chitosan-shell properties have been modified using low-molecular-weight (LMW) and high-molecular-weight (HMW) chitosan chains having different degrees of acetylation (DA). With regard to the stability mediated by repulsive hydration forces, the LMW chitosan provided the best results. In addition, contrary to initial expectations, greater stability (also mediated by hydration forces) was found in the samples formed with chitosan chains of high DA values (i.e. with less hydrophilic chitosan). Finally, a theoretical treatment was also tested to quantify the hydrophilicity of the chitosan shells.

Quantum-dot-decorated robust transductable bioluminescent nanocapsules.

Bioluminescence, due to its high sensitivity, has been exploited in various analytical and imaging applications. In this work, we report a highly stable, cell-transductable, and wavelength-tunable bioluminescence system achieved with an elegant and simple design. Using aqueous in situ polymerization on a bioluminescent enzyme anchored with polymerizable vinyl groups, we obtained nanosized core-shell nanocapsules with the enzyme as the core and a cross-linked thin polymer net as the shell. These nanocapsules possess greatly enhanced stability, retained bioactivity, and a readily engineered surface. In particular, by incorporating polymerizable amines in the polymerization, we endowed the nanocapsules with efficient cell-transduction and sufficient conjugation sites for follow-up modification. Following in situ polymerization, decorating the polymer shell with fluorescent quantum dots allowed us to access a continuous tunable wavelength, which extends the application of such bioluminescent nanocapsules, especially in deep tissue. In addition, the unique core-shell structure and adequate conjugation sites on surface enabled us to maximize the BRET efficiency by adjusting the QD/enzyme conjugation ratio.

Synthesis of polystyrene nanocapsules by redox interface‐initiated inversed microemulsion polymerization for drug release

AbstractPolystyrene nanocapsules with a diameter of 140 nm and a water‐soluble sodium salicylate core were prepared by redox interface‐initiated emulsion polymerization (RIEP) in an inversed microemulsion with cumene hydroperoxide/iron(II) sulfate as the redox initiation couple. The morphology of the nanocapsules was characterized by transmission electron microscopy and field emission scanning electron microscopy. Dynamic light scattering was used to determine the nanocapsule size and polydispersity (0.14–0.20). The release of sodium salicylate from the nanocapsules was monitored by ultraviolet–visible spectroscopy. All of the results indicate that the fabrication of core–shell nanocapsules with the water‐soluble active chemical as the core via RIEP was successful. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Core−Shell Nanoparticles: Characterization and Study of Their Use for the Encapsulation of Hydrophobic Fluorescent Dyes

Core-shell nanocapsules intended to be used as drug scavengers were prepared using a surfactant mixture containing octadecyltrimethoxysilane (OTMS) as a reactive amphiphile, to form spherical templates. A siloxane shell was grown on the surface of the templates by reacting tetramethoxysilane (TMOS) with the silanol groups obtained after the hydrolysis and condensation of OTMS. Dynamic light scattering (DLS) showed that particles with diameters in the range of 100-200 nm were obtained, with core and shell sizes controlled by varying component compositions. Atomic force microscopy (AFM) was used to study the effect of the silica coating of the templates on their robustness after deposition on a substrate. Subsequently, we present studies on the encapsulation of two hydrophobic fluorescent dyes, which are sensors of polarity and rigidity. Steady-state fluorescence spectroscopy was used to examine the fluorescence response of the dyes before and after shell growth. Changes in the emission of the encapsulated dyes were related to changes in the polarity and rigidity of the microenvironment where the dyes were located and correlated to the AFM results. Finally, dye-free core-shell particles were used to sequester the dyes from aqueous suspensions. Fluorescence of the sequestered species was compared to the dye-loaded particles to determine the final fate of the fluorophores in the nanoparticles.

Chemical synthesis and characterization of boron/boron nitride core–shell nanostructures

A moderate chemical method [i.e., the reaction of diborane (B2H6) and a mixture gas of ammonia and nitrogen (NH3/N2) over nanoscale iron boride at 1100 °C] was developed to explore the boron nitride (BN) nanostructures. The products were well characterized by high-resolution electron microscopy and energy-dispersive x-ray spectroscopy. Two types of novel core–shell nanocapsules of amorphous boron core encapsulated in crystalline boron nitride shell were obtained. The first one looked like a peanut with an amorphous B core containing a trace of BN crystallites, a transition layer of BN nanofibers and amorphous B, and a thornlike shell of BN nanofibers. The second one looked like a perfect sphere consisting of a pure amorphous B core and a rather smooth crystalline BN shell. These results not only provided us a new chemical method for preparing BN nanostructures but also enriched the important BN nanostructures family. A growth mechanism is also briefly discussed.

Radiation-cured polymeric nanocomposites of enhanced surface-mechanical properties

Though polymerisation-active metallo-organic nanoparticles have proven exceedingly efficient in modifying the viscoelastic properties of UV and EB crosslinked polymeric nanocomposites, they are obviously unsuitable for practical applications. Rather, adequate polymerisation-activity was imparted on inorganic nanoparticles, e.g. silica and alumina, by grafting onto them functionalised trialkoxysilanes, yielding covalent-bonded, hydrolysis-stable surface compounds. Extensive spectroscopic studies of their siloxane structure led to the idea of a core-shell nanocapsule. The polysiloxane shell formed around the inorganic nanoparticle is not only of major importance to the rheological behaviour of the nanodispersion but, moreover, also admits a sufficiently high nanofiller content for a pronounced reinforcement of the nanocomposite coating. In recent work, organophilation of the inorganic nanoparticles could be accomplished by just applying adsorptive means, thus evading the formation of the precarious alcohols and alkyl acrylates. In the event, round milled corundum micro-particles turned out to be efficient synergists in further improving the respective coatings.