Design of Magnetic Fe3O4/CeO2 "Core/Shell"-Like Nanocomposites with Pronounced Antiamyloidogenic and Antioxidant Bioactivity.

"Core/shell" nanocomposites based on magnetic magnetite (Fe3O4) and redox-active cerium dioxide (CeO2) nanoparticles (NPs) are promising in the field of biomedical interests because they can combine the ability of magnetic NPs to heat up in an alternating magnetic field (AMF) with the pronounced antioxidant activity of CeO2 NPs. Thus, this report is devoted to Fe3O4/CeO2 nanocomposites (NCPs) synthesized by precipitation of the computed amount of "CeO2-shell" on the surface of prefabricated Fe3O4 NPs. The X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy data validated the formation of Fe3O4/CeO2 "core/shell"-like NCPs, in which ultrafine CeO2 NPs with an average size of approximately 3-3.5 nm neatly surround Fe3O4 NPs. The presence of a CeO2 "shell" significantly increased the stability of Fe3O4/CeO2 NCPs in aqueous suspensions: Fe3O4/CeO2 NCPs with "shell thicknesses" of 5 and 7 nm formed highly stable magnetic fluids with ζ-potential values of >+30 mV. The magnetization values of Fe3O4/CeO2 NCPs decreased with a growing CeO2 "shell" around the magnetic NPs; however, the resulting composites retained the ability to heat efficiently in an AMF. The presence of a CeO2 "shell" generates a possibility to precisely regulate tuning of the maximum heating temperature of magnetic NCPs in the 42-50 °C range and stabilize it after a certain time of exposure to an AMF by changing the thickness of the "CeO2-shell". A great improvement was observed in both antioxidant and antiamyloidogenic activities. It was found that inhibition of insulin amyloid formation, expressed in IC50 concentration, using NCPs with a "shell thickness" of 7 nm was approximately 10 times lower compared to that of pure CeO2. For these NCPs, more than 2 times higher superoxide dismutase-like activity was observed. The coupling of both Fe3O4 and CeO2 results in higher bioactivity than either of them individually, probably due to a synergistic catalytic mechanism.

Fabrication of superparamagnetic bovine haemoglobin surface-imprinted core-shell nanocomposite adsorbent via emulsion-free sol-gel polymerization.

A new strategy has been developed to fabricate a bovine haemoglobin surface-imprinted core-shell nanocomposite adsorbent, demonstrating superparamagnetism via emulsion-free and sol-gel techniques. The obtained magnetic surface-imprinted polymers (MSIPs) possess a porous core-shell nanocomposite structure with a remarkable imprinted recognition ability for template protein in aqueous medium. The MSIPs display higher affinity, adsorption efficiency and selectivity, for template protein compared to the non-target protein. The morphology, adsorption, and recognition properties of the MSIPs have been evaluated by using several characterisation techniques, such as scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry. The results show the average diameter of MSIPs ranging between 400 and 600 nm with a saturation magnetization value of 52.6 emu/g and adsorption capacity of 43.75 mg/g. And because the obtained MSIPs possessed easily accessible recognition sites and performed fast kinetics for template immobilization, it could achieve equilibrium within 60 min. All this revealed the potential application of this approach as an alternative methodology for the generation of protein imprinted biomaterials.

High Thermoelectric Power Generation by SWCNT/PPy Core Shell Nanocomposites.

Polypyrrole (PPy) is a conducting polymer with attractive thermoelectric (TE) properties. It is simple to fabricate and modify its morphology for enhanced electrical conductivity. However, such improvement is still limited to considerably enhancing TE performance. In this case, a single-wall carbon nanotube (SWCNT), which has ultrathin diameters and exhibits semi-metallic electrical conductivity, might be a proper candidate to be combined with PPy as a core shell one-dimensional (1D) nanocomposite for higher TE power generation. In this work, core shell nanocomposites based on SWCNT/PPy were fabricated. Various amounts of pyrrole (Py), which are monomer sources for PPy, were coated on SWCNT, along with methyl orange (MO) as a surfactant and ferric chloride as an initiator. The optimum value of Py for maximum TE performance was determined. The results showed that the SWCNT acted as a core template to direct the self-assembly of PPy and also to further enhance TE performance. The TE power factor, PF, and figure of merit, zT, values of the pure PPy were initially recorded as ~1 µW/mK2 and 0.0011, respectively. These values were greatly increased to 360 µW/mK2 and 0.09 for the optimized core shell nanocomposite sample. The TE power generation characteristics of the fabricated single-leg module of the optimized sample were also investigated and confirmed these findings. This enhancement was attributed to the uniform coating and good interaction between PPy polymer chains and walls of the SWCNT through π-π stacking. The significant enhancement in the TE performance of SWCNT/PPy nanocomposite is found to be superior compared to those reported in similar composites, which indicates that this nanocomposite is a suitable and scalable TE material for TE power generation.

Self-Assembled Biodegradable Core-Shell Nanocomposites of Amphiphilic Retinoic Acid-LMW bPEI Conjugates Exhibit Enhanced Transgene Expression in Hepatocellular Carcinoma Cells With Inherent Anticancer Properties.

Low molecular weight branched polyethylenimines (LMW bPEIs) are almost nontoxic but display poor transfection efficiency due to lack of adequate complexation ability with nucleic acids followed by transportation across the cell membrane. Here, a series of amphiphilic retinoyl-bPEI conjugates (RP-1, RP-2 and RP-3) has been synthesized by allowing the reaction between bPEI (1.8 kDa) and a bioactive and hydrophobic vitamin A metabolite, all-trans-retinoic acid (ATRA), in varying amounts. In aqueous medium, these conjugates self-assembled into core-shell RP nanocomposites with size ranging from ~113-178 nm and zeta potential from ~ +15-35 mV. Evaluation of pDNA complexes of RP nanocomposites revealed that all the complexes exhibited significantly enhanced transfection efficiency without compromising on the cytocompatibility. RP-3/pDNA complex, with the highest content of retinoic acid, exhibited the best transfection efficiency. Further, due to anticancer properties of ATRA, these nanocomposites significantly reduced the viability of cancer cells (HepG2 and MCF-7 cells) without affecting the viability of non-cancerous cells (HEK 293 cells) demonstrating the cell-selective nature of the formulated nanocomposites. The intracellular trafficking and co-localization studies involving RP-3 nanocomposites also showed their higher uptake with intracellular and nuclear accumulation properties. Altogether, the results demonstrate the promising potential of the RP conjugates that can be used in future hepatocellular carcinoma targeted gene delivery applications.

Ligand-RNA interaction assay based on size-selective fluorescence core-shell nanocomposite.

The application of the dye-labeled fluorescence method in a ligand-RNA interaction assay is a complex and costly process prone to steric hindrance. Fluorescent nanomaterials offer an attractive alternative due to their simple, low-cost synthesis and effective screening properties. Here, CdTe@ZIF-8 core-shell nanocomposites were used as fluorescence signal transducer in the ligand-TAR RNA interaction assay. Different experimental strategies were developed based on the size-selective nature of the CdTe@ZIF-8 nanocomposites. When ligands can quench fluorescence, two assays of fluorescence recovery with TAR RNA and Tat peptide competitive displacement are carried out successively, which can not only distinguish ligands binding to TAR RNA but also screen potential Tat protein antagonists. When ligands cannot quench fluorescence, the mitoxantrone-TAR RNA complex is used in the competitive displacement assay. Ligands that displaced mitoxantrone from the mitoxantrone-TAR RNA complex signaled the interaction with TAR RNA. Eight ligands, including known and unknown TAR RNA-binding ligands, were tested via the above strategies. The results showed that this method was effective at distinguishing the known RNA-binding partner and screening the Tat antagonist from the test ligands. This simple and effective strategy is expected to be suitable for actual drug screening. Graphical abstract.

Correction to: Magnetic-core@dual-functional-shell nanocomposites with peroxidase mimicking properties for use in colorimetric and electrochemical sensing of hydrogen peroxide.

A self-sacrificing catalytic method is described for the preparation of magnetic core/dual-functional-shell nanocomposites composed of magnetite, gold and Prussian blue (type Fe3O4@Au-PB). Two reaction pathways are integrated. The first involves chemical dissolution of Fe3O4 (the self-sacrificing step) by acid to release ferrous ions which then reacts with hexacyanoferrate(IV) to generate PB in the proximity of the magntic nanoparticles (MNPs). The second involves the reduction of tetrachloroaurate by hydroxylamine to generate gold under the catalytic effect of the MNPs. At the end, the MNP@Au-PB nanocomposite is formed. This method exploits both the chemical reactivity and catalytic effect of the MNPs in a single step. The multi-function material was applied (a) in an optical assay for H2O2; (b) in an amperometric assay for H2O2; (c) in an enzymatic choline assay using immobilized choline oxidase. The limit of electrochemical detection of H2O2 (at a potential as low as 50 mV) is 1.1 µM which is comparable or better than most analogous methods. The sensors display superior performance compared to the use of conventional core@single-shell (MNP@Au-PB) nanomaterials. Graphical abstract A self-sacrificing catalytic method is described to prepare magnetic core/dual-functional-shell nanocomposites composed of magnetic nanoparticle, gold and Prussian blue (type MNP@Au-PB). The nanocomposites worded well as candidates to develop colorimetric and electrochemical sensors of H2O2 with superior performance to analogues.

Controlled synthesis of Au@Pd core-shell nanocomposites and their application for electrochemical sensing of hydroquinone.

In this study, a facile and effective method for the synthesis of Au@Pd nanocomposites via a chemical reduction method was proposed. Moreover, a novel electrochemical sensor based on the Au@Pd core-shell nanocomposites were constructed and used for detection of hydroquinone (HQ). The morphologies and structures of Au nanorods (NRs) and Au@Pd nanomaterials were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and electrochemical methods. By tuning the amount of Pd precursor, different Au@Pd core-shell nanocomposites were gained. It could be clearly shown that the Au3@Pd6 (nAu:nPd = 3:6) modified the glassy carbon electrode (Au3@Pd6/GCE) possessed a sensitive electrochemical response toward HQ and the oxidation peak appeared at nearly 0 V at the potential window range of -0.3 to 0.3 V. Meanwhile, the experimental results found a broad concentration range of 4-5000 µM, a low detection limit of 0.63 µM and desirable sensitivity of 1.127 mA mM-1 cm-2. The mentioned sensor was successfully applied for HQ determination in the lake water and tap water samples. It is expected that the proposed method can be used for the synthesis of other metal nanostructures with distinguished electrocatalytic abilities and used for environmental monitoring of hydroquinone.

Fabrication, optimization, and characterization of ultra-small superparamagnetic Fe3O4 and biocompatible Fe3O4@ZnS core/shell magnetic nanoparticles: Ready for biomedicine applications.

Magnetic nanoparticles that preferred for biomedical applications are required to be biocompatible, nanosized and superparamagnetic. In this research, ultra-small superparamagnetic Fe3O4 nanoparticles and novel superparamagnetic Fe3O4@ZnS core/shell nanocomposites were fabricated using biocompatible ethylenediaminetetraacetic acid (EDTA) as a capping agent by a facile refluxing assisted co-precipitation method at optimum condition. The Fe3O4 and Fe3O4@ZnS nanoparticles were investigated using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), UV-Vis spectroscopy, vibrating sample magnetometer (VSM) and Dynamic Light Scattering (DLS). The VSM results indicated that all of the samples have superparamagnetic behavior. The particle size of the Fe3O4 and Fe3O4@ZnS nanoparticles were obtained at about 10 and 22 nm, respectively.

Magnetic-core@dual-functional-shell nanocomposites with peroxidase mimicking properties for use in colorimetric and electrochemical sensing of hydrogen peroxide.

A self-sacrificing catalytic method is described for the preparation of magnetic core/dual-functional-shell nanocomposites composed of magnetite, gold and Prussian Blue (type Fe3O4@Au-PB). Two reaction pathways are integrated. The first involves chemical dissolution of Fe3O4 (the self-sacrificing step) by acid to release ferrous ions which then reacts with hexacyanoferrate(IV) to generate PB in the proximity of the magntic nanoparticles (MNPs). The second involves the reduction of tetrachloroaurate by hydroxylamine to generate gold under the catalytic effect of the MNPs. At the end, the MNPs@Au-PB nanocomposite is formed. This method exploits both the chemical reactivity and catalytic effect of the MNPs in a single step. The multi-function material was applied (a) in an optical assay for H2O2; (b) in an amperometric assay for H2O2; (c) in an enzymatic choline assay using immobilized choline oxidase. The limit of electrochemical detection of H2O2 (at a potential as low as 50 mV) is 1.1 µM which is comparable or better than most analogous methods. The sensors display superior performance compared to the use of conventional core@single-shell (MNPs@PB) nanomaterials. Graphical abstract A self-sacrificing catalytic method is described to prepare magnetic core/dual-functional-shell nanocomposites composed of magnetic nanoparticle, gold and Prussian Blue (type MNP@Au-PB). The nanocomposites work well as candidates to develop colorimetric and electrochemical sensors of H2O2 with superior performance to analogues.

Fabrication of a new superparamagnetic metal-organic framework with core-shell nanocomposite structures: Characterization, biocompatibility, and drug release study.

The Superparamagnetic CoFe2O4NPs@Mn-Organic Framework core-shell nanocomposites that had potential application in targeted drug-delivery were synthesized by layer to layer method. The structure and composition of the obtained microspheres were characterized by SEM, TEM, DLS, XRD, VSM, FTIR, and TG analysis. Results showed that the structures have a high degree crystalline, high temperature stability, magnetics and core-shell nanocomposites. Therefore, it is an excellent candidate for drug delivery systems. Afterwards, Daunorubicin (as a drug model) was laden in the MOFs by a Simple stirring. For comparison of magnetic properties of MOFs for drug delivery, an external magnetic field applied to the plate to evaluate the efficiency. The external magnetic field significantly increases anti-tumor activity of formulation (drug+ MOFs). The results showed that MOFs are biocompatible, which endue MOFs great potential in targeting drug-delivery systems with enhanced efficiency.

Synthesis, characterisation, cellular uptake and cytotoxicity of functionalised magnetic ruthenium (II) polypyridine complex core-shell nanocomposite.

The development of multifunctional nanoparticles comprising of a magnetic core in conjunction with appropriate molecules with capabilities to impart functionalities like luminescent, specific binding sites to facilitate attachment of moieties. This has attracted increasing attention and enables identification of promising candidates using for applications such as diagnostics and cure through early detection and localized delivery. Many studies have been performed on the synthesis and cellular interactions of core-shell nanoparticles, in which a functional inorganic core is coated with a biocompatible polymer layer that should reduce nonspecific uptake and cytotoxicity Here we report the synthesis and characterisation of multifunctional core-shell magnetic, luminescent nanocomposite (Fe3O4@SiO2@[Ru(Phen)3]2+@SiO2@NH2). Fe3O4 as core and a luminescent ruthenium (II) complex encapsulated with silica shell, and then it is functionalized by an amine group by APTMS. The magnetic, luminescent, and biological activity of this multifunctional nanocomposite have also been studied to prove the nanocomposite is biocompatible, cellular uptake. The synthesized nanocomposite was completely characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and emission spectroscopy. MTT assay and cellular uptake by flow cytometry results proved that magnetic ruthenium (II) polypyridine complex - core shell nanocomposite has biocompatibility, minimum cytotoxicity and internalized inside B16F10 cells and confirms the potential biomedical applications.

New nanocomposites of polystyrene with polyaniline doped with lauryl sulfuric acid.

This work is concentrated on synthesis and investigation of new core-shell nanocomposites of polystyrene (PS) with doped polyaniline (PANI). The latex containing PS nanoparticles with sizes of 15-30 nm was prepared by microemulsion polymerization of styrene in water media. The PS/PANI nanocomposites were synthesized by chemical oxidative polymerization of aniline in the PS latex media in a presence of lauryl sulfuric acid (LSA), which served as both dopant and plasticizer. The real content of PANI in the synthesized nanocomposites was determined by UV-Vis spectroscopy method. The composition of the nanocomposites and oxidation state of the doped polyaniline were characterized by FTIR spectroscopy. The core-shell morphology of the nanocomposite nanoparticles was proved by transmission and scanning electron microscopy. It was found that conductivity and thermal behavior in air of these nanocomposites not only nonlinearly depended on the doped polyaniline content but also were strongly effected both by plasticizing properties of the acid-dopant and presence of the polyaniline shell. A possibility of application of these nanocomposites as sensor materials has been demonstrated.

Size-selective QD@MOF core-shell nanocomposites for the highly sensitive monitoring of oxidase activities.

In this work, we proposed a novel and facile method to monitor oxidase activities based on size-selective fluorescent quantum dot (QD)@metal-organic framework (MOF) core-shell nanocomposites (CSNCPs). The CSNCPs were synthesized from ZIF-8 and CdTe QDs in aqueous solution in 40min at room temperature with stirring. The prepared CdTe@ZIF-8 CSNCPs , which have excellent water dispersibility and stability, displays distinct fluorescence responses to hole scavengers of different molecular sizes (e.g., H2O2, substrate, and oxidase) due to the aperture limitation of the ZIF-8 shell. H2O2 can efficiently quench the fluorescence of CdTe@ZIF-8 CSNCPs over a linearity range of 1-100nM with a detection limit of 0.29nM, whereas large molecules such as substrate and oxidase have very little effect on its fluorescence. Therefore, the highly sensitive detection of oxidase activities was achieved by monitoring the fluorescence quenching of CdTe@ZIF-8 CSNCPs by H2O2 produced in the presence of substrate and oxidase, which is proportional to the oxidase activities. The linearity ranges of the uricase and glucose oxidase activity are 0.1-50U/L and 1-100U/L, respectively, and their detection limits are 0.024U/L and 0.26U/L, respectively. Therefore, the current QD@MOF CSNCPs based sensing system is a promising, widely applicable means of monitoring oxidase activities in biochemical research.