Gold-coated Iron Oxide Research Articles

Glutathione decorated gold-magnetic nanoparticles: efficient and recyclable catalyst for biotechnological and pharmaceutical applications

Nowadays, since the core-shell gold-magnetite nanoparticles include the saturation magnetisation (iron oxide) and plasmon surface (gold shell) properties, they have been considered in biological and biomedicine research areas. In the present work, multifunctional glutathione decorated gold-coated iron oxide nanoparticles (GSH-AuMNPs) were successfully synthesised and fully characterised. From the absorption peak at 525, the formation of the core-shell GSH-AuMNPs was confirmed. Although the saturation magnetisation value was slightly decreased during the formation process, they were easily recovered through magnetic decantation. The biocompatibility of the synthesised NPs was approved by the cytotoxicity researches. Furthermore, the GSH-AuMNPs indicated a good catalytic activity for the catalytic reduction of 2-nitrophenol by sodium borohydride and reused for six consecutive cycles without a significant decrease in its activity. Overall, this study introduced a unique structure with high catalytic activity, which could provide a useful platform for the biomedical, analytical, catalytic applications and wastewater treatment.

Multimodal cancer cell therapy using Au@Fe2O3 core-shell nanoparticles in combination with photo-thermo-radiotherapy.

In this study, gold coated iron oxide nanoparticle (Au@Fe2O3 NP) was synthesized in a core-shell structure. Photothermal and radiosensitization effects of Au@Fe2O3 NPs were investigated on KB human mouth epidermal carcinoma cell line. Cell death and apoptosis were measured to study the effects of nanoparticles in combination with both radiotherapy (RT) and photothermal therapy (PTT). The KB cells were treated with Au@Fe2O3 NPs (20 μg/ml; 4 h) and then received different treatment regimens of PTT and/or RT using laser (808 nm, 6 W/cm2, 10 min) and/or 6 MV X-ray (single dose of 2 Gy). Following the various treatments, MTT assay was performed to evaluate the cell survival rate. Also, the mode of cell death was determined by flow cytometry using an annexinV-fluorescein isothiocyanate/propidium iodide apoptosis detection kit. No significant cell death was observed due to laser irradiation. The viability of the cells firstly incubated with NPs and then exposed to the laser was significantly decreased. Additionally, our results demonstrated that Au@Fe2O3 NP is a good radiosensitizer at megavoltage energies of X-ray. When nanoparticles loaded KB cells were received both laser and X-ray, the cell viability substantially decreased. Following such a combinatorial treatment, flow cytometry determined that the majority of cell death relates to apoptosis. In conclusion, Au@Fe2O3 NP has a great potential to be applied as a photo-thermo-radiotherapy sensitizer for treatment of head and neck tumors.

Enrichment and Identification of Metallothionein by Functionalized Nano-Magnetic Particles and Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry

Abstract As a low molecular weight protein with the ability of binding metal ions and high inducibility, metallothionein (MT) is often regarded as an important biomarker for assessment of heavy metal pollution in water environment. In the light of that the traditional process of enrichment and identification is time-consuming and complicated, we prepared a core-shell nanoparticle, gold-coated iron oxide nanoparticles (Fe3O4@Au NPs) herein. It possessed the advantages of fast response to magnetic fields and optical properties attributing to Fe3O4 and Au nanoparticles, respectively. The Fe3O4@Au nanoparticles could be used to enrich MT simply through Au–S interaction, and the purified proteins were determined by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS). The results showed that the Fe3O4@Au nanoparticles could directly enrich MT from complex solutions and the detection limit could be as low as 10 fg mL−1.

Surface plasmon resonance enhanced light absorption and wavelength tuneable in gold-coated iron oxide spherical nanoparticle

Surface plasmon in nano-sized particles, such as gold, silver, copper and their composites, has recently attracted a great deal of attention due to its possible uses in many applications, especially in life sciences. It is desirable for application devices with a tenability of surface plasmon wavelength and optical properties enhancement. This article presents enhanced optical light absorption and tunable wavelength in gold-coated magnetite (Fe3O4@Au core-shell) nanoparticles embedded in water using the theoretical method of discrete dipole approximation (DDA). The absorption spectra in the wavelengths from 350 to 900 nm were found to be the spectra obtained from Fe3O4@Au core-shell nanoparticles, and when compared with pure Fe3O4 nanoparticles, the surface plasmon resonance can be enhanced and tuned over the entire visible spectrum (viz. 350–800 nm) of the electromagnetic spectrum by varying the Au shell thickness (2–5 nm). Similarly, the Faraday rotation spectra can also be obtained.

Multifunctional gold coated iron oxide core-shell nanoparticles stabilized using thiolated sodium alginate for biomedical applications

In this paper we report synthesis of aqueous based gold coated iron oxide nanoparticles to integrate the localized surface plasma resonance (SPR) properties of gold and magnetic properties of iron oxide in a single system. Iron oxide-gold core shell nanoparticles were stabilized by attachment of thiolated sodium alginate to the surface of nanoparticles. Transmission electron microscope (TEM) micrograph presents an average elementary particle size of 8.1±2.1nm. High resolution TEM (HR-TEM) and X-ray photon spectroscopy further confirms the presence of gold shell around iron oxide core. Gold coating is responsible for reducing saturation magnetization (Ms) value from ~41emu/g to ~24emu/g – in thiolated sodium alginate stabilized gold coated iron oxide core-shell nanoparticles. The drug (curcumin) loading efficiency for the prepared nanocomposites was estimated to be around 7.2wt% (72μgdrug/mg nanoparticles) with encapsulation efficiency of 72.8%. Gold-coated iron oxide core-shell nanoparticles could be of immense importance in the field of targeted drug delivery along with capability to be used as contrast agent for MRI & CT.

Preparation of concave magnetoplasmonic core-shell supraparticles of gold-coated iron oxide via ion-reducible layer-by-layer method for surface enhanced Raman scattering

Preparation of suprastructure assemblies with unique colloidal and optical properties remains challenging. Non-uniform covering of magnetic nanoparticles (NPs) with an external inert Au shell has been attempted to protect the magnetic core against oxidation as well as to produce multifunctional supraparticles (SPs) possessing respective optical and magnetic properties. In this study, a concave Au NP coating was deposited on magnetic nanoparticles (MNPs) with precise control of the shell thickness and roughness through a layer-by-layer (LbL) assisted ionic reduction method termed ion-reducible LbL (IR-LbL) method. Surface enhanced Raman spectra were obtained using graphene quantum dots (GQDs) on the magnetically aligned structure of the prepared core-shell SPs. It is probable that this synthesis method and the generated SPs are essential for characterizing the merge of electronics and magnetism in the nano-regime and may be applicable for further electronics, magnetic storage, and biomedical applications.

Radioiodination of cyclin dependent kinase inhibitor Olomoucine loaded Fe@Au nanoparticle and evaluation of the therapeutic efficacy on cancerous cells

Abstract Magnetic nanoparticles have promising biomedical applications such as drug delivery, novel therapeutics and diagnostic imaging. Magnetic drug delivery combination works on the delivery of magnetic nanoparticles loaded with drug to the target tissue by means of an external magnetic field. Gold coated iron oxide (Fe@Au) nanoparticles can provide useful surface chemistry and biological reactivity. Covalent conjugation to the Fe@Au nanoparticles through cleavable linkages can be used to deliver drugs to tumor cells, then the drug can be released by an external. In this paper, purine based cyclin dependent kinases (CDKs) inhibitor Olomoucine (Olo) [2-(Hydroxyethylamino)-6-benzylamino-9-methylpurine] was loaded on gold coated iron oxide (Fe@Au) nanoparticles and radiolabeled with 131I to combine magnetic targeted drug delivery and radiotherapy. Fe@Au nanoparticles were synthesized by microemulsion method. The characterization of nanoparticles was examined by TEM, VSM and XRD. Amine activation was utilized by cysteamine hydrochloride and then CDI was used for conjugation of Olomoucine. Antiproliferative effect and cytotoxicity of Olomoucine loaded Fe@Au nanoparticles (Fe@Au-Olo) were investigated on MCF7 and A549 cell lines. Proliferation rate was decreased while uptake of Fe@Au-Olo on both cell lines was high in comparison with Olomoucine. Also, enhanced incorporation ratio was observed under external magnetic field.

D, L-Sulforaphane Loaded Fe3O4@ Gold Core Shell Nanoparticles: A Potential Sulforaphane Delivery System.

A novel design of gold-coated iron oxide nanoparticles was fabricated as a potential delivery system to improve the efficiency and stability of d, l-sulforaphane as an anticancer drug. To this purpose, the surface of gold-coated iron oxide nanoparticles was modified for sulforaphane delivery via furnishing its surface with thiolated polyethylene glycol-folic acid and thiolated polyethylene glycol-FITC. The synthesized nanoparticles were characterized by different techniques such as FTIR, energy dispersive X-ray spectroscopy, UV-visible spectroscopy, scanning and transmission electron microscopy. The average diameters of the synthesized nanoparticles before and after sulforaphane loading were obtained ∼ 33 nm and ∼ 38 nm, respectively, when ∼ 2.8 mmol/g of sulforaphane was loaded. The result of cell viability assay which was confirmed by apoptosis assay on the human breast cancer cells (MCF-7 line) as a model of in vitro-cancerous cells, proved that the bare nanoparticles showed little inherent cytotoxicity, whereas the sulforaphane-loaded nanoparticles were cytotoxic. The expression rate of the anti-apoptotic genes (bcl-2 and bcl-xL), and the pro-apoptotic genes (bax and bak) were quantified, and it was found that the expression rate of bcl-2 and bcl-xL genes significantly were decreased when MCF-7 cells were incubated by sulforaphane-loaded nanoparticles. The sulforaphane-loaded into the designed gold-coated iron oxide nanoparticles, acceptably induced apoptosis in MCF-7 cells.

CD163-Macrophages Are Involved in Rhabdomyolysis-Induced Kidney Injury and May Be Detected by MRI with Targeted Gold-Coated Iron Oxide Nanoparticles.

Macrophages play an important role in rhabdomyolysis-acute kidney injury (AKI), although the molecular mechanisms involved in macrophage differentiation are poorly understood. We analyzed the expression and regulation of CD163, a membrane receptor mainly expressed by anti-inflammatory M2 macrophages, in rhabdomyolysis-AKI and developed targeted probes for its specific detection in vivo by MRI. Intramuscular injection of glycerol in mice promoted an early inflammatory response, with elevated proportion of M1 macrophages, and partial differentiation towards a M2 phenotype in later stages, where increased CD163 expression was observed. Immunohistological studies confirmed the presence of CD163-macrophages in human rhabdomyolysis-AKI. In cultured macrophages, myoglobin upregulated CD163 expression via HO-1/IL-10 axis. Moreover, we developed gold-coated iron oxide nanoparticles vectorized with an anti-CD163 antibody that specifically targeted CD163 in kidneys from glycerol-injected mice, as determined by MRI studies, and confirmed by electron microscopy and immunological analysis. Our findings are the first to demonstrate that CD163 is present in both human and experimental rhabdomyolysis-induced AKI, suggesting an important role of this molecule in this pathological condition. Therefore, the use of probes targeting CD163-macrophages by MRI may provide important information about the cellular composition of renal lesion in rhabdomyolysis.

Targeted gold-coated iron oxide nanoparticles for CD163 detection in atherosclerosis by MRI.

CD163 is a membrane receptor expressed by macrophage lineage. Studies performed in atherosclerosis have shown that CD163 expression is increased at inflammatory sites, pointing at the presence of intraplaque hemorrhagic sites or asymptomatic plaques. Hence, imaging of CD163 expressing macrophages is an interesting strategy in order to detect atherosclerotic plaques. We have prepared a targeted probe based on gold-coated iron oxide nanoparticles vectorized with an anti-CD163 antibody for the specific detection of CD163 by MRI. Firstly, the specificity of the targeted probe was validated in vitro by incubation of the probe with CD163(+) or (−) macrophages. The probe was able to selectively detect CD163(+) macrophages both in human and murine cells. Subsequently, the targeted probe was injected in 16 weeks old apoE deficient mice developing atherosclerotic lesions and the pararenal abdominal aorta was imaged by MRI. The accumulation of probe in the site of interest increased over time and the signal intensity decreased significantly 48 hours after the injection. Hence, we have developed a highly sensitive targeted probe capable of detecting CD163-expressing macrophages that could provide useful information about the state of the atheromatous lesions.

The electrochemical study of glucose oxidase on gold-coated magnetic iron oxide nanoparticles

A feasible and fast method for glucose oxidase (GOx) study was developed by covalent attachment of GOx to gold-coated magnetic iron oxide nanoparticles (Fe@Au).GOx molecules were oxidized with metaperiodate to form aldehyde group. The prepared Fe@Au composite nanoparticles with 60 nm diameter were used as a carrier for the immobilization of GOx. Fe@Au nanoparticles were modified by cysteamine to produce amine groups at the surface. The GOx was covalently attached to the amine-modified Fe@Au nanoparticles through its aldehyde groups. The direct electrochemistry of GOx showed a quasi-reversible cyclic voltammogram corresponding to the flavin adenine dinucleotide (FAD/FADH 2) redox couple with a formal potential of–270 mV in 0.1 M phosphate buffer. The apparent charge transfer rate constant (k s) and transfer coefficient for electron transfer between the electrode surface and enzyme were calculated as 2.23 s–1 and 0.45, respectively. The linear concentration range of the biosensor is 2.4–54 mM with detection limit of 0.51 mM at S/N = 3. The apparent Michaelis-Menten constant was measured to be 8.59 mM, indicating that the immobilized GOx on Fe@Au preserved its native activity. The life time of biosensor is more than 2 weeks.

Ascorbic acid-mediated synthesis and characterisation of iron oxide/gold core–shell nanoparticles.

The current article reports on providing surface modification of magnetic nanoparticles with gold to provide stability against aggregation. Gold-coated magnetite nanoparticles were synthesised to combine both magnetic as well as surface plasma resonance (SPR) properties in a single moiety. The nanocomposites were produced by reduction (using ascorbic acid) of gold chloride on to the surface of iron oxide nanoparticles. Ascorbic acid not only acts as a reducing agent, but also the oxidised form of ascorbic acid i.e. Dehydro-ascorbic acid acts as a capping agent to impart stability to as synthesised gold-coated iron oxide nanocomposites. The synthesised nanocomposite was monodispersed with a mean particle size of around 16 nm and polydispersity index of 0.190. X-ray diffraction analysis confirms presence of gold on the surface of magnetite nanoparticles. The synthesised nanocomposites had a total organic content of around 3.2% w/w and also showed a shifted SPR peak at 546 nm as compared to gold nanoparticles (528 nm). Both uncoated and gold-coated magnetite exhibited superparamagnetic behaviour at room temperature. Upon coating with gold shell, saturation magnetisation of iron oxide nanoparticles decreases from 42.806 to 3.54 emu/gram.

Electrochemical piezoelectric reusable immunosensor for aflatoxin B1 detection

A competitive, reusable, reliable and sensitive immunosensor based on electrochemical quartz crystal microbalance (EQCM) was developed for the detection of aflatoxin B1 (AFB1). The sensing platform was developed using a primary monoclonal anti-aflatoxin antibody (anti AFB1) covalently immobilized on a monolayer of 4-amino thiophenol self assembled on a gold coated quartz crystal electrode (anti AFB1/4-ATP/Au). The reusability was achieved by a sandwiched system using secondary rabbit-immunoglobulin antibodies (r-IgGs) tagged with core shell of gold coated iron oxide nanoparticles (r-IgG–Au-Fe3O4), which can be used to regenerate the bioelectrode. A competitive mode was employed, between free and coated AFB1 for fixed concentration of nanoparticle conjugate (r-IgG–Au–Fe3O4). After the competitive interaction, immunoelectrode was washed with phosphate saline buffer (PBS) at pH 7.4 and examined by electrochemical quartz crystal microbalance-cyclic voltammetry (EQCM-CV). Under the optimized conditions, the fabricated immunosensor can be used to detect AFB1 quantitatively with a linear range of 0.05 to 5ngmL−1. For reliability, the fabricated immuno sensor was tested using cereal samples spiked with different concentrations of AFB1. In addition, this immuno electrode displays good reproducibility, and storage stability. The above immunosensor was regenerated with negligible loss in activity through removal of the r-IgG–Au–Fe3O4 conjugate using a strong magnet. It is shown that theAFB1/BSA/aAFB1/4-ATP/Au immuno sensor is a new approach for developing sensitive reliable and reusable electrochemical piezoelectric immunosensors.

Development of Gold-Coated Magnetic Nanoparticles as a Potential MRI Contrast Agent

Gold-coated superparamagnetic iron oxide nanoparticles (SPIONs) coated with methyl-polyethylene glycol (mPEG) are synthesized and investigated as a magnetic resonance (MR) imaging contrast agent. The synthesized mPEG-core@shells are characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), vibrating sample magnetometry (VSM), zeta-potential analysis and X-ray diffraction (XRD). In addition, the transverse relaxivity of the mPEG-core@shells is measured using a 3 T MRI scanner. The cytotoxicity of the mPEG-core@shells is tested in the LNCaP cell line using an 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results show that the mPEG-core@shell particles are semispherical with hydrodynamic size of ∼ 65 nm and a transverse relaxivity of 162.3 mM-1 S-1. The mPEG-core@shell particles demonstrate good stability in biological media without any significant in vitro cytotoxicity under high cellular uptake conditions. Finally, in vivo imaging shows that mPEG-core@shells are a potential contrast agent for use in early-stage detection.

Functionalised Au Coated Iron Oxide Nanocomposites Based Reusable Immunosensor for AFB1 Detection

A reusable sandwiched electrochemical piezoelectric immunosensor has been developed for aflatoxin B1 (AFB1) detection using gold coated iron oxide core‐shell (Au‐Fe3O4) nanostructure. The monoclonal anti‐aflatoxin antibody (aAFB1) was immobilized on self‐assembled monolayer of 4‐aminothiophenol on gold coated quartz crystal to fabricate immunoelectrode (BSA/aAFB1/4‐ATP/Au). In addition, secondary rabbit‐immunoglobulin antibodies (r‐IgGs) functionalized with Au‐Fe3O4 NPs via cysteamine (r‐IgG‐Cys‐Au‐Fe3O4) were allowed to interact with AFB1. Both competitive and noncompetitive strategies were employed and a competition between coated AFB1 and free AFB1 was carried out. The competitive mode shows higher linear range (0.05 to 5 ng mL−1) than the noncompetitive one (0.5 to 5 ng mL−1), high sensitivity 335.7 µA ng−1 mL cm−2, and LOD 0.07 ng mL−1. The fabricated immunosensor has been tested using cereal samples spiked with different concentrations of AFB1. The developed competitive immunoelectrode displays good reproducibility, and storage stability and regenerated with negligible loss in activity through removal of the r‐IgG‐Cys‐Au‐Fe3O4 conjugate using a strong external magnet.

Polysorbate Stabilised Fe3O4 and Fe3O4@Au Nanoparticle Synthesis and Characterisation

Polysorbate (tween) stabilised iron oxide and gold coated iron oxide nanoparticles were synthesised using the high-temperature solution phase reaction of iron(III) acetylacetate, Fe(acac)3, with 1,2-hexadecanediol and long chain alcohols. FT-IR analysis confirmed the presence of the surfactants on the nanoparticles, while the size and shape of the nanoparticles were determined by TEM. Coating of the nanoparticles was confirmed by UV-vis spectrometry and XRD. Thermal analysis indicated greater stability for the Tween 20 and Tween 60 stabilised Fe3O4@Au nanoparticles, than the nanoparticles without gold.

Viruslike Nanoparticles with Maghemite Cores Allow for Enhanced MRI Contrast Agents

Here, for the first time, we demonstrate formation of virus-like nanoparticles (VNPs) utilizing gold-coated iron oxide nanoparticles as cores and capsid protein of brome mosaic virus (BMV) or hepatitis B virus (HBV) as shells. Further, utilizing cryo-electron microscopy and single particle methods, we are able to show that the BMV coat on VNPs assembles into a structure very close to that of a native virion. This is a consequence of an optimal iron oxide NP size (∼11 nm) fitting the virus cavity and an ultrathin gold layer on the maghemite cores, which allows for utilization of SH-(CH2)11-(CH2-CH2-O)4-OCH2-COOH as capping molecules to provide sufficient stability, charge density, and small form factor. MRI studies show unique relaxivity ratios that diminish only slightly with gold coating. A virus protein coating of a magnetic core mimicking the wild-type virus makes these VNPs a versatile platform for biomedical applications.

Cytotoxicity and gene expression in sarcoma 180 cells in response to spiky magnetoplasmonic supraparticles.

Multifunctional nanoparticles (NPs) have been designed for a variety of cell imaging and therapeutic applications, and the study of their cellular interactions is crucial to the development of more efficient biomedical applications. Among current nanomaterials, concave core-shell NPs with complex angled geometries are attractive owing to their unique shape-dependent optical and physical properties as well as different tendency for cell interaction. In this study, we investigated the morphology effect of spiky gold-coated iron oxide supraparticles (Fe3O4@Au SPs) on cytotoxicity and global gene expression in sarcoma 180 cells. Cells treated for 7 days with spiky supraparticles (SPs) at concentrations up to 50 μg/mL showed >90% viability, indicating that these NPs were nontoxic. To shed light on the differences in cytotoxicity, we monitored the expression of 33,315 genes using microarray analysis of SP-treated cells. The 171 up-regulated genes and 181 down-regulated genes in spiky SP-treated cells included Il1b, Spp1, Il18, Rbp4, and Il11ra1, where these genes are mainly involved in cell proliferation, differentiation, and apoptosis. These results suggested that the spiky Fe3O4@Au SPs can induce noncytotoxicity and gene expression in tumor cells, which may be a promising cornerstone on which to base related research such as cyto-/genotoxicology of nanomaterials or the design of nanoscale drug carriers.

Doxorubicin-loaded magnetic gold nanoshells for a combination therapy of hyperthermia and drug delivery

In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated superparamagnetic iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency was investigated to be as high as 0.32mg/mg. Thus synthesized particles were characterized by HRTEM, UV–Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency, and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast cancer) and non-cancerous H9c2 cardiac cell type.

Impact of core dielectric properties on the localized surface plasmonic spectra of gold-coated magnetic core-shell nanoparticles.

Gold-coated iron oxide core-shell nanoparticles (IO-Au NPs) are of interest for use in numerous biomedical applications because of their unique combined magnetic-plasmonic properties. Although the effects of the core-dielectric constant on the localized surface plasmon resonance (LSPR) peak position of Au-shell particles have been previously investigated, the impact that light-absorbing core materials with complex dielectric functions have on the LSPR peak is not well established. In this study, we use extended Mie theory for multilayer particles to examine the individual effects of the real and imaginary components of core refractive indices on Au-shell NP plasmonic peaks. We find that the imaginary component dampens the intensity of the cavity plasmon and results in a decrease of surface plasmon coupling. For core materials with large imaginary refractive indices, the coupled mode LSPR peak disappears, and only the anticoupled mode remains. Our findings show that the addition of a nonabsorbing polymer layer to the core surface decreases the dampening of the cavity plasmon and increases LSPR spectral intensity. Additionally, we address apparent discrepancies in the literature regarding the effects of Au-shell thickness on LSPR peak shifts.