Core-shell Hybrid Nanoparticles Research Articles

Nanoporous hybrid core-shell nanoparticles for sequential release.

In this article, a new type of core-shell nanoparticle is introduced. In contrast to most reported core-shell systems, the particles presented here consist of a porous core as well as a porous shell using only non-metal materials. The core-shell nanoparticles were successfully synthesized using nanoporous silica nanoparticles (NPSNPs) as the starting material, which were coated with nanoporous phenylene-bridged organosilica, resulting in a total particle diameter of about 80 nm. The combination of a hydrophilic nanoporous silica core and a more hydrophobic nanoporous organosilica shell provides regions of different chemical character and slightly different pore sizes within one particle. These different properties combined in one particle enable the selective adsorption of guest molecules at different parts of the particle depending on the molecular charge and polarity. On the other hand, the core-shell make-up of the particles provides a sequential release of guest molecules adsorbed at different parts of the nanoparticles. As a proof of concept, loading and release experiments with dyes were performed using non polar fluorescein and polar and charged methylene blue as model guest molecules. Non polar fluorescein is mostly adsorbed on the hydrophobic organosilica shell and therefore quickly released whereas the polar methylene blue, accumulated in the hydrophilic silica core, is only released subsequently. This occurs in small doses for an extended time corresponding to a sustained release over at least one year, controlled by the organosilica shell which acts as a diffusion barrier. An initial experiment with two drugs - non polar ibuprofen and polar and charged procaine hydrochloride - has been carried out as well and shows that the core-shell nanoparticles presented here can also be used for the sequential release of more relevant combinations of molecules.

Nanoparticle-based metasurfaces for angular independent spectral filtering applications

We designed a metasurface made of a monolayer of spherical nanoparticles embedded in a dielectric slab, which exhibits transmission properties independent of the incidence angle. Adjusting the electromagnetic coupling between high-index dielectric and hybrid core-shell nanoparticles enables the metasurface to operate in low-pass, bandpass, as well as band-stop regimes in the visible and near-infrared spectral ranges. We demonstrate how symmetric properties of spherical nanoparticles determine the response of the metasurface, resulting in a spectral filter with a wide angular acceptance range. We study transmission characteristics of the metasurface, such as frequency selectivity, the slope of filtering at cutoff frequencies, and the robustness of the metasurface against experimental variations in geometrical parameters. Our analyses show that the proposed approach can be used to design angular-independent spectral filters with the same material platform and approach to operate in different regimes and spectral ranges.

Core-Shell Structure Design of Hollow Mesoporous Silica Nanospheres Based on Thermo-Sensitive PNIPAM and pH-Responsive Catechol-Fe3+ Complex.

A kind of core-shell hybrid nanoparticle comprised of a hollow mesoporous silica nanoparticles (HMS) core and a copolymer shell bearing N-(3,4-dihydroxyphenethyl) methacrylamide (DMA) and N-isopropylacrylamide (NIPAM) as responsive moieties was prepared. Moreover, the factors that could impact the surface morphology and hierarchical porous structure were discussed. In the presence of Fe3+, catechol-Fe3+ complexes were formed to achieve pH-responsive polymer shell, combining with thermal-sensitiveness of poly(N-isopropylacrylamide). Doxorubicin (DOX) was applied as a model drug and the behaviors of its loading/release behaviors were investigated to prove the idea. The results exhibited a significant drug loading capacity of 8.6% and embed efficiency of 94.6% under 1 mg ml–1 DOX/PBS solution. In fact, the loading capacity of drug can be easily improved to as high as 28.0% by increasing the DOX concentration. The vitro cytotoxicity assay also indicated that the as-prepared nanoparticles have no significant cytotoxicity on RAW 264.7 cells. The in vitro experiment showed that the cumulative release of DOX was obviously dependent on the temperature and pH values. This pH/temperature-sensitive hollow mesoporous silica nanosphere is expected to have potential applications in controlled drug release.

Hybrid and hollow Poly(N,N-dimethylaminoethyl methacrylate) nanogels as stimuli-responsive carriers for controlled release of doxorubicin

Smart drug-delivery systems based on stimuli-responsive polymers are extensively studied because of their advantages in controlled release of anti-cancer drugs in response to induced stimuli. To develop a smart drug-delivery system, silica nanoparticles modified with 3-(trimethoxysilyl) propyl methacrylate (MPS) were used in inverse emulsion polymerization of N,N-dimethylaminoethyl methacrylate with N,N-methylene bisacrylamide in different amounts (MBA: 2, 4, and 8 mol%). The temperature- and pH-responsive hybrid core-shell nanoparticles were used for preparation of hollow poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) nanogels by hydrolysis of the silica cores. Fourier-transform infrared spectroscopy was used to confirm the surface modification of silica nanoparticles with MPS. Successful synthesis of the hybrid and hollow nanogels was investigated by thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. In addition, temperature-responsivity and phase separation behavior of the hybrid and hollow nanogels were studied by UV/Vis spectroscopy. The UV/Vis spectra showed that the absorption intensity was increased with increasing MPS and MBA contents in basic conditions. The hollow nanogels showed higher swelling/deswelling ratio compared to the hybrid nanogels in acidic media (pH 3.5) and at temperatures above the volume phase transition temperature (70 °C). Some of the hybrid and hollow nanogels with different crosslinking densities were used as smart drug carriers for doxorubicin (DOX), and their release behavior were investigated at different pH (3.5 and 7.5) by UV/Vis spectroscopy. The release profiles display that release of DOX has increased in pH of 3.5, and the hollow nanogels showed lower release contents than the hybrid nanogels because of diffusion and encapsulation of DOX molecules in the hollow space. The experimental release profiles confirmed that DOX release percentage in the hybrid nanogels was more than the hollow ones, while loading capacity of the hollow nanogels was higher. The Korsmeyer-Peppas model showed the best fitting with the experimental results of DOX release from PDMAEMA carriers.

Electrical-Field Induced Nonlinear Conductive Characteristics of Polymer Composites Containing SiO2-Decorated Silver Nanowire Hybrids

Environment adaptive electromagnetic protection for electronic systems with transmitting and receiving electromagnetic information is increasingly important because of rapid development of information technology and the application of strong electromagnetic pulse. Easy-to-prepare materials with stable electrical-field induced nonlinear conductive characteristics are strongly desired. In this study, the core–shell hybrid nanoparticles of SiO2-decorated silver nanowire hybrids (AgNWs@SiO2) were synthesized via a sol–gel process employed in a polyvinyl alcohol (PVA) matrix material to prepare composites. Microstructure analysis demonstrated that SiO2 insulating layer was well-bonded to the surface of AgNWs. The AgNWs@SiO2/PVA composites exhibited stable and excellent nonlinear conductive behavior under increasingly applied voltage with high filling concentration of the hybrid nanoparticles, the switching threshold voltage of proposed composites can be tuned by optimizing the loading amount of AgNWs@SiO2 hybrid fillers and the thickness of the SiO2 insulating layer. The mechanism of the nonlinear conductive characteristic of the composites was discussed. The shielding effectiveness (SE) of the developed material against the square-wave electromagnetic pulse up to 15 dB, which verified the adaptive protection function of the AgNWs@SiO2/PVA composite.

Porphyrin-xylan-coated silica nanoparticles for anticancer photodynamic therapy

Porphyrins are widely used in anticancer photodynamic therapy (PDT). However, low physiological solubility and lack of selectivity towards cancer cells are the main limitations of their clinical use. Nanoparticles are being intensively explored as photosensitizer carriers for PDT to overcome these limitations. The aims of this work are to synthesize core-shell hybrid nanoparticles formed by a silica core and xylan carrying a 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin (TPPOH) shell, and evaluate their anticancer activity. To afford drug-controlled incorporation and enhance blood circulation, TPPOH was covalently linked to xylan. Different xylans with degrees of substitution in TPPOH ranging from 0.034 to 1.11, were obtained and characterized. Then, the xylan-TPPOH conjugate (PX) was used to coat the silica nanoparticles (PX SNPs). The obtained nano-objects were characterized and their therapeutic potential for photodynamic therapy evaluated against colorectal cancer cell lines. in vitro analysis showed that PX SNPs were 40-fold and 10-fold more effective against HCT116 cells and HT-29 cells respectively compared to free TPPOH.

Improved druggability of gambogic acid using core-shell nanoparticles.

Gambogic acid (GA) is a natural antitumor drug candidate with advantages of broad-spectrum activity, low toxicity and multiple mechanisms. Its clinical application is hindered, however, by low aqueous solubility, instability and poor pharmacokinetic properties. In this research, core-shell hybrid nanoparticles have been developed to improve the druggability of GA. The nanoparticles are composed of a benzylamidated poly(γ-glutamic acid) (BzPGA) derivative as a core material and an amphiphilic hyaluronic acid derivative grafted with all-trans retinoic acid (HA-C6-ATRA) as a shell material. Through π-π stacking interactions, GA is encapsulated into BzPGA to form the "core" of the hybrid nanoparticle and the "shell" is formed by HA-C6-ATRA with a π-π stacking mediated "molecular fence". The nanovehicle, with sub 100 nm size, provides almost 100% encapsulation efficiency, a good protective effect and a sustained release profile for GA. A series of evaluations suggest that the core-shell nanoparticles provide a stable aqueous injection formulation (I), improved stability (II), prolonged circulation time and conferred tumor targeting properties (III) for GA. As a result, the anti-tumor activity of GA is significantly enhanced without causing higher toxicity, indicating that the designed nanoplatform dramatically improves the druggability of GA. This study may also provide inspiration for drug development research.

Hybrid Core-Shell Nanoparticles by "Plug and Play" Self-Assembly.

Supramolecular hybrid functional nanoparticles (NPs) can be obtained via the colloidal tectonics approach provided that multiple interactive molecular tectons are used. Herein, the programmable synthesis of novel hybrid core-shell nanoparticles via the following sequential steps is reported: (i) complexation of 1-decanol by the β-cyclodextrin (β-CD), (ii) spontaneous self-assembly into CD NPs, (iii) adsorption of polyoxometalate anions, PW12 O40 3- , on the polar neutral interface of the CD NPs. Such an approach paves the way for the design of novel and original materials and systems.

Robust and flexible strain sensors based on dual physically cross-linked double network hydrogels for monitoring human-motion

Soft, stretchable, and elastic hydrogels have recently attracted immense interest due to their potential applications in wearable strain sensors. However, most of hydrogel-based sensors exhibit poor mechanical properties. Here, a robust, flexible and strain-sensitive conductive wearable sensor is prepared based on dual physically cross-linked double network hydrogels consisting of core-shell hybrid nanoparticles cross-linked polyacrylamide as first network and Ca2+ cross-linked alginate as second network. Dynamic physical cross-linking as sacrifice bonds can effectively dissipate energy and reconstruct the network structure, endowing hydrogels with high strength, toughness, stretchability and excellent self-recovery properties. Moreover, the hydrogels exhibit outstanding strain sensitive behavior with repeatable, stable, and precise changes in resistance signals. Based on the excellent strain sensitivity, the hydrogel can be assembled as a wearable strain sensor to monitor joint motions such as finger, wrist, elbow, neck, and knee joints, and even the slight motions including breathing and speaking. Thus, the tough, anti-fatigue, self-recovery and conductive hydrogels have promising potential as soft, high-performance and flexible wearable strain sensor for soft robots, biomimetic prostheses, human activity monitoring and health-monitoring systems.

Preparation of novel optically active polyamide@silica hybrid core-shell nanoparticles and application for enantioselective crystallization

A kind of hybrid core-shell nanoparticles (NPs) based on a novel chiral polyamide for the application in enantioselective crystallization was studied in this work. First, the optically active polyamide (PA11DT) derived from bio-based D-tartaric acid and 1,11-undecanediamine was synthesized. Fantastically, the aliphatic polyamide with low chiral atom content in the backbone showed rather strong optical activity. Particularly, PA11DT in solid state displayed more intense optical activity than that in solution, which is due to its more regular helical aggregation in solid state. Second, the core-shell structural NPs consisting of PA11DT and SiO2 were designed to make sure its stable helical structure in practice. The PA11DT@SiO2 NPs with the core-shell structure and a uniform diameter were successfully achieved in a preformed aqueous microemulsion system through an in-situ approach. The obtained nanoparticles mantained strong optical activity and displayed more thermostable chirality. The core-shell nanospheres can be used as a specific chiral additive to induce enantioselective crystallization of racemic alanine. As a result, D-alanine was crystallized preferentially with an e.e. value to 63% after 48 h crystallization.

Photoelectrochemical Methanol Oxidation on TiN@Au Core-Shell Nanoparticles Supported on TiO2

Refractory transition metal nitrides such as TiN and ZrN are a new class of plasmonic materials that exhibit plasmonic resonance in the visible and near-infrared regions [1, 2]. The similarity of optical appearance of TiN to gold makes one wonder whether inexpensive and chemically and mechanically robust TiN can replace Au in plasmon-mediated photocatalytic reactions. Prior research [3] has shown that cubic 50 nm TiN nanoparticles supported on TiO2 nanowires provide greater photocurrent enhancement for the photoelectrochemical water splitting compared to spherical Au nanoparticles. This has been attributed to more efficient hot carrier generation by TiN nanoparticles, followed by more efficient collection of hot electrons by TiO2. 50 nm TiN nanoparticles (NPs), however, proved to be inefficient in promoting photocatalytic activity of TiO2 towards methanol oxidation in the visible region [4]. This was likely due to a lack of catalytic activity of the TiN NPs’ surface for CH3OH oxidation. Here, we explore the plasmon-mediated photocatalytic methanol oxidation on hybrid core-shell nanoparticles consisting of a thin gold shell and TiN core and compare the effect of TiO2-supported TiN@Au nanoparticles to that of Au on the photon-to-electron conversion efficiency. The TiO2-supported TiN@Au photocatalysts were made by the deposition of a thin Au shell on 20 and 50 nm TiN NPs (PlasmaChem) followed by the dispersion of the TiN@Au NPs onto TiO2 nanoparticle support (Degussa). Electrochemical experiments were conducted in a three-electrode photoelectrochemical cell. The thin films of TiN@Au/TiO2 on FTO-coated glass served as working electrodes (WEs), while platinum foil and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as counter and reference electrodes, respectively. LED lights were used as light sources. X-Ray Photoelectron Spectroscopy, Powder X-Ray Diffraction, and high resolution transmission electron microscopy were used for characterization of catalysts surface composition and morphology.

Synthesis and Characterization of Ferromagnetic Fe3O4–ZnO Hybrid Core–Shell Nanoparticles

Room-temperature synthesis of multifunctional core–shell nanostructures with iron oxide (Fe3O4) core and zinc oxide (ZnO) shell is described. High-resolution transmission electron microscopy revealed the occurrence of heteroepitaxial growth of a ZnO shell over the iron oxide nanoparticle core. The formation of the core–shell nanostructure was also evidenced by x-ray diffraction and x-ray photoelectron spectroscopy analyses. The core Fe3O4 nanoparticles exhibited superparamagnetic behavior at room temperature in an externally applied magnetic field. However, magnetic measurements of the core–shell nanoparticles revealed ferromagnetic behavior, originating from defect-induced ferromagnetism in the ZnO shell. The prepared core–shell nanoparticles also exhibited strong photoresponse while retaining ferromagnetic behavior at room temperature.

Superparamagnetic silica core-shell hybrid attached to graphene oxide as a promising recoverable catalyst for expeditious synthesis of TMS-protected cyanohydrins

Fe3O4/SiO2 core-shell hybrid nanoparticles covalently attached to graphene oxide (Fe3O4/SiO2/PTS-GO) were prepared and fully characterized using different techniques including Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The efficiency of Fe3O4/SiO2/PTS-GO nanocomposite was demonstrated in trimethylsilyl cyanide (TMSCN) addition to a wide range of aldehydes and ketones in high to quantitative yields under extremely mild conditions. Low catalyst loading, reusability of the catalyst, avoiding the use of any hazardous solvent, short reaction time at ambient temperature and straightforward work up procedure are some of the attractive advantages of this protocol.

Hydrogen bonding directed co-assembly of polyoxometalates and polymers to core–shell nanoparticles

A general strategy has been developed to co-assemble polyoxometalates and polymers into core–shell hybrid nanoparticles via hydrogen bonding interaction.

A synergistically enhanced photothermal transition effect from mesoporous silica nanoparticles with gold nanorods wrapped in reduced graphene oxide

In this work, near-infrared (NIR)-responsive core–shell gold nanorods/mesoporous silica/reduced graphene oxide (Au/SiO2/rGO) nanoparticles with synergistically enhanced photothermal stability and transition effect had been prepared via electrostatic interaction. Gold nanorods (AuNRs) and rGO were employed as the NIR-responsive components. UV–Vis–NIR extinction spectra revealed that the surface plasmon resonance peak of AuNRs from Au/SiO2/rGO nanohybrids remained unchanged after 9 h NIR exposure. UV–Vis–NIR extinction results also showed that thin silica shell was superior to the thick ones in the photothermal stability improvement of Au/SiO2/rGO nanoparticles. Moreover, the doxorubicin release of Au/SiO2/rGO was more rapid than that of Au/SiO2 upon NIR irradiation, indicating that synergistically enhanced photothermal effect between rGO and AuNRs endowed Au/SiO2/rGO nanoparticles with excellent photothermal transition efficiency. Such novel NIR-responsive core–shell hybrid nanoparticles with enhanced photothermal stability and transition effect are well suited for further biological applications, such as photothermal therapy, bioimaging and drug delivery.

Hybrid Core-Shell (HyCoS) Nanoparticles produced by Complex Coacervation for Multimodal Applications

Multimodal imaging probes can provide diagnostic information combining different imaging modalities. Nanoparticles (NPs) can contain two or more imaging tracers that allow several diagnostic techniques to be used simultaneously. In this work, a complex coacervation process to produce core-shell completely biocompatible polymeric nanoparticles (HyCoS) for multimodal imaging applications is described. Innovations on the traditional coacervation process are found in the control of the reaction temperature, allowing a speeding up of the reaction itself, and the production of a double-crosslinked system to improve the stability of the nanostructures in the presence of a clinically relevant contrast agent for MRI (Gd-DTPA). Through the control of the crosslinking behavior, an increase up to 6 times of the relaxometric properties of the Gd-DTPA is achieved. Furthermore, HyCoS can be loaded with a high amount of dye such as ATTO 633 or conjugated with a model dye such as FITC for in vivo optical imaging. The results show stable core-shell polymeric nanoparticles that can be used both for MRI and for optical applications allowing detection free from harmful radiation. Additionally, preliminary results about the possibility to trigger the release of a drug through a pH effect are reported.

ZnO/Ni(OH)2 core-shell nanoparticles: Synthesis, optical, electrical and photoacoustic property analysis

The optical and electrical properties of ZnO/Ni(OH)2 core-shell hybrid nanoparticles have been studied and reported here. The sample is prepared by hydrothermal method using a 100 ml Teflon lined stainless steel autoclave. ZnO nanoparticles are employed as core material for Ni(OH)2 seeds, and subsequent nucleated growth of Ni(OH)2 nanoparticles by cationic surfactant Cetyl Tri-methyl Ammonium Bromide (CTAB) formed the ZnO/Ni(OH)2 core-shell nanoparticles. The material was confirmed and immaculateness hexagonal wurtziite structure is analyzed by powder X-ray diffraction and the functional groups are identified by FTIR and FT-Raman analyses. The crystalline size, shape and surface morphology of the ZnO/Ni(OH)2 nanoparticles are determined by using FE–SEM. Dynamic Light Scattering (DLS) analysis reveals the stability and particle size distribution of the synthesized ZnO/Ni(OH)2 nanoparticles. The optical absorbance wavelength observed at 354 nm has been shifted to 373 nm during hydrothermal synthesis of ZnO nanoparticles and 215 nm for ZnO/Ni(OH)2 nanoparticles. Energy band gap is reduced from bulk state of 3.5 eV–3.3 eV during this hydrothermal synthesis of ZnO nanoparticles. The electrical properties of ZnO/Ni(OH)2 nanoparticles have been studied by dielectric, ac conductivity measurements. Small value of dielectric constant and the dielectric loss shows the suitability of the material for electro-optic device fabrication. Thermal diffusivity of the pellet sample is calculated by photoacoustic technique and is found to be 3.3 × 10−6 m2/s.

Direct synthesis of platinum nanodots in ZIF-8/Fe3O4 core–shell hybrid nanoparticles

Platinum nanodots were synthesized inside ZIF-8/Fe3O4 core–shell hybrid nanoparticles without additional reducing agents, which showed high catalytic activity for the reduction of 4-nitrophenol.

Construction of core-shell hybrid nanoparticles templated by virus-like particles

Catalytically active gold in silica core–shell nanoparticles are prepared by pH controlled templating on virus-like particles.

Zwitterionic Iron Oxide (γ-Fe2 O3 ) Nanoparticles Based on P(2VP-grad-AA) Copolymers.

This study presents the synthesis and characterization of zwitterionic core-shell hybrid nanoparticles consisting of a core of iron oxide multicore nanoparticles (MCNPs, γ-Fe2 O3 ) and a shell of sultonated poly(2-vinylpyridine-grad-acrylic acid) copolymers. The gradient copolymers are prepared by reversible addition fragmentation chain transfer polymerization of 2-vinylpyridine (2VP), followed by the addition of tert-butyl acrylate and subsequent hydrolysis. Grafting of P(2VP-grad-AA) onto MCNP results in P(2VP-grad-AA)@MCNP, followed by quaternization using 1,3-propanesultone-leading to P(2VPS -grad-AA)@MCNP with a zwitterionic shell. The resulting particles are characterized by transmission electron microscopy, dynamic light scattering, and thermogravimetric analysis measurements, showing particle diameters of ≈70-90 nm and an overall content of the copolymer shell of ≈10%. Turbidity measurements indicate increased stability toward secondary aggregation after coating if compared to the pristine MCNP and additional cytotoxicity tests do not reveal any significant influence on cell viability.