Gold-coated Magnetic Nanoparticles Research Articles

Enhancement of chemotherapy effects by non-lethal magneto-mechanical actuation of gold-coated magnetic nanoparticles

Remote magneto-mechanical actuation (MMA) of magnetic nanoparticles (MNP) is emerging as a promising therapy method in oncology. However, translation to the clinic faces the challenge of whole-body action and the reluctance about indiscriminate mechanical action of the nanoparticles on tumor and healthy cells. Here, we show how the MMA method based on magnetically-rotated gold-coated MNP boosts only the activity of an unbound antitumor drug, without physical damage of cells via MNP. Therefore, in clinical practice, the effect of antitumor drug can be safely increased systemically while maintaining drug concentrations at current doses.

Preparation of immunomagnetic composite nanostructures with bifunctional four-arm PEG derivatives as linkers for the ultrafast enrichment of zearalenone and its metabolites

It is challenging to prepare sample pretreatment materials with simple use, strong selectivity and satisfactory enrichment performance. In this study, the antibody (3D4) that can specifically recognize zearalenone (ZEN) and its metabolites was immobilized on the surface of gold-coated magnetic Fe3O4 nanoparticles (GMN) by streptavidin (SA)-biotin interaction using GMN as the substrate and our designed four-arm PEG derivative (HS-4ARMPEG10K-(CM)3) as the linker. The immunomagnetic nanoparticles (GMN-4ARMPEG10K-SA-3D4) prepared by this strategy can achieve rapid enrichment (only 5 min) of analytes directly in the matrix, and higher enrichment capacity compared with the previous immunomagnetic particles. The sensitive and accurate analysis of ZEN and its metabolites can be achieved coupled with HPLC-MS/MS. The LODs and LOQs were 0.02–0.05 μg/kg and 0.05–0.10 μg/kg, respectively. The recoveries were 84.13%–112.67%, and the RSDs were 1.09%–9.39%. The method can provide a powerful tool for highly sensitive and rapid monitoring of mycotoxins in complex matrices due to its’ strong selectivity and resistance to matrix interference.

Single-Molecule Protein Analysis by Centrifugal Droplet Immuno-PCR with Magnetic Nanoparticles.

Detecting proteins in ultralow concentrations in complex media is important for many applications but often relies on complicated techniques. Herein, a single-molecule protein analyzer with the potential for high-throughput applications is reported. Gold-coated magnetic nanoparticles with DNA-labeled antibodies were used for target recognition and separation. The immunocomplex was loaded into microdroplets generated with centrifugation. Immuno-PCR amplification of the DNA enabled the quantification of proteins at the level of single molecules. As an example, ultrasensitive detection of α-synuclein, a biomarker for neurodegenerative diseases, is achieved. The limit of detection was determined to be ∼50 aM in buffer and ∼170 aM in serum. The method exhibited high specificity and could be used to analyze post-translational modifications such as protein phosphorylation. This study will inspire wider studies on single-molecule protein detection, especially in disease diagnostics, biomarker discovery, and drug development.

Magneto-photothermal synergy applied to gold-coated magnetic nanoparticles

In this work, we describe the synthesis of magnetic nanoparticles with a suitable size for easy cellular internalization, avoiding their rapid renal excretion (less than 5 nm) and accumulation in the liver (more than 100 nm). The nanoparticles are functionalized with a biocompatible polymer (low molecular weight, branched polyethylenimine, PEI), and this treatment allows their functionalization with a shell of gold particles in order to improve their ability to absorb electromagnetic radiation in the visible and near infrared wavelength regions. As a result, the magnetic nanostructures are potential agents of local heating (hyperthermia) by exposing them to alternating magnetic fields (magnetic hyperthermia) or to light of the suitable wavelength (photothermia). Magnetic hyperthermia experiments demonstrate that both types of particles can reach the desired temperature range for cell apoptosis, with the difference of a shorter time needed when gold is absent. The released thermal energy is measured by the SAR (specific absorption rate, in W/g), and the values found are promising, up to 600 W/g in the case of uncoated particles. Regarding the photothermia response under the IR radiation, it is comparable for gold-coated and uncoated magnetic particles, but it is enhanced by a factor of almost 10 when the incident light is visible (blue-green) and the particles are provided with their gold shell. Improvements related to the selection of gold particles with resonant absorbance in the infrared are under investigation.

A novel visual biosensor for mercury detection based on a cleavable phosphorothioate-RNA probe and microfluidic bead trap

Mercury ion (Hg2+) detection plays a crucial role in safeguarding the environment and protecting human health. In this study, we developed a microfluidic biosensing platform that utilizes a phosphorothioate-RNA (PS-RNA) probe and gold-coated magnetic nanoparticles to quantify Hg2+ visually. The PS-RNA probe was linked to gold-coated magnetic nanoparticles via Au–S interaction and biotin–avidin interaction and then combined with polystyrene microspheres to form a self-assembled structure called a magnetic bead-AuNP-probe-polystyrene (MAPP) bead. We designed and fabricated a microfluidic chip that contained only a magnetic separator and a particle trap. The presence of Hg2+ cut the PS-RNA probe, leading to the separation of magnetic beads and polystyrene microspheres. The MAPP was removed by the magnetic separator, while the cut polystyrene microspheres flowed along the channel and accumulated in the particle trap, forming a long visible strip. The length of the polystyrene microsphere strip was proportional to the Hg2+ concentration. The microfluidic biosensing platform exhibited high sensitivity and specificity for Hg2+ detection, with a detection limit of 21.9 nM. By integrating the microfluidic magnetic manipulation system with a sensitive nucleic acid probe, we developed an automated and visual biosensor that is a valuable reference for the on-site visual detection of heavy metal ions.

Synthesis and characterization of a new gold-coated magnetic nanoparticle decorated with a thiol-containing dendrimer for targeted drug delivery, hyperthermia treatment and enhancement of MRI contrast agent

A unique multi-functional magnetic nanocarrier containing thiol groups was designed and applied in drug delivery, hyperthermia and as a contrast agent in MRI. The polymeric nanoparticles were prepared by modification of Fe3-δO4@Au magnetic nanoparticles with a thiol-ended dendrimer. This platform introduces suitable carriers through the grafting of thiol-ended dendrimer for the further binding of an anticancer drug as 6-mercaptopurine (6-MP). The drug is released when exposed to the reductive environmental conditions of cancer cells. Cytotoxicity of the MNP-CC2-6-MP with human breast cancer cell line MCF-7 was examined. Also, the MNP, [email protected], and MNP-CC2 nanomaterials were used as magnetic hyperthermia tools and as a contrast agent in MRI and the results were compared with each other. The effect of RF hyperthermia and the released drug in cancer cells were simultaneously investigated as well and confirmed the therapeutic efficiency of those new composite nanomaterials. This magneto dendrimer with multimodal cancer therapy can be selected as an ideal source for biomedicine study.

Resorc[4]arene-Modified Gold-Decorated Magnetic Nanoparticles for Immunosensor Development.

In recent years, several efforts have been made to develop selective, sensitive, fast response, and miniaturized immunosensors with improved performance for the monitoring and screening of analytes in several matrices, significantly expanding the use of this technology in a broad range of applications. However, one of the main technical challenges in developing immunosensors is overcoming the complexity of binding antibodies (Abs) to the sensor surface. Most immobilizing approaches lead to a random orientation of Abs, resulting in lower binding site density and immunoaffinity. In this context, supramolecular chemistry has emerged as a suitable surface modification tool to achieve the preorganization of artificial receptors and to improve the functional properties of self-assembled monolayers. Herein, a supramolecular chemistry/nanotechnology-based platform was conceived to develop sensitive label-free electrochemical immunosensors, by using a resorcarene macrocycle as an artificial linker for the oriented antibody immobilization. To this aim, a water-soluble bifunctional resorc[4]arene architecture (RW) was rationally designed and synthesized to anchor gold-coated magnetic nanoparticles (Au@MNPs) and to maximize the amount of the active immobilized antibody (Ab) in the proper "end-on" orientation. The resulting supramolecular chemistry-modified nanoparticles, RW@Au@MNPs, were deposited onto graphite screen printed electrodes which were then employed to immobilize three different Abs. Furthermore, an immunosensor for atrazine (ATZ) analysis was realized and characterized by the differential pulse voltammetry technique to demonstrate the validity of the developed biosensing platform as a proof of concept for electrochemical immunosensors. The RW-based immunosensor improved AbATZ loading on Au@MNPs and sensitivity toward ATZ by almost 1.5 times compared to the random platform. Particularly, the electrochemical characterization of the developed immunosensor displays a linearity range toward ATZ within 0.05-1.5 ng/mL, a limit of detection of 0.011 ng/ml, and good reproducibility and stability. The immunosensor was tested by analyzing spiked fortified water samples with a mean recovery ranging from 95.7 to 108.4%. The overall good analytical performances of this immunodevice suggest its application for the screening and monitoring of ATZ in real matrices. Therefore, the results highlighted the successful application of the resorc[4]arene-based sensor design strategy for developing sensitive electrochemical immunosensors with improved analytical performance and simplifying the Ab immobilization procedure.

Development of gold-coated magnetic nanoparticles as a theranostic agent for magnetic hyperthermia and CT imaging applications

In this study, we aim to develop gold-coated Fe3O4 nanoparticles (Fe3O4@Au NPs) as theranostic agents for magnetic hyperthermia and CT imaging applications. The Fe3O4 NPs were synthesized via thermal decomposition method, and the gold was then deposited onto the surface of Fe3O4 NPs by reducing gold acetate at 190 °C. The average sizes of Fe3O4 and Fe3O4@Au NPs were 5.2 nm and 6.1 nm, respectively, which are effectively removed by the kidneys. The magnetization of Fe3O4@Au NPs (9.7 emu/g-Fe3O4) at 300 K was much smaller than that of Fe3O4 NPs (52.4 emu/g-Fe3O4). The heating efficiency of Fe3O4@Au NPs in water was sufficient to treat the tumor at 43–45 °C, and their high CT value of 851 HU was obtained. The synthesized ultrasmall Fe3O4@Au NPs showed great promise as a potential theranostic agent for magnetic hyperthermia and CT imaging applications.

Expanding the Toolbox of Target Directed Bio-Orthogonal Synthesis: In Situ Direct Macrocyclization by DNA Templates.

Herein, we demonstrate for the first time that noncanonical DNA can direct macrocyclization-like challenging reactions to synthesize gene modulators. The planar G-quartets present in DNA G-quadruplexes (G4s) provide a size complementary reaction platform for the bio-orthogonal macrocyclization of bifunctional azide and alkyne fragments over oligo- and polymerization. G4s immobilized on gold-coated magnetic nanoparticles have been used as target templates to enable easy identification of a selective peptidomimetic macrocycle. Structurally similar macrocycles have been synthesized to understand their functional role in the modulation of gene function. The innate fluorescence of the in situ formed macrocycle has been utilized to monitor its cellular localization using a G4 antibody and its in cell formation from the corresponding azide and alkyne fragments. The successful execution of in situ macrocyclization in vitro and in cells would open up a new dimension for target-directed therapeutic applications.

Extracellular vesicles derived from bone marrow mesenchymal stem cells loaded on magnetic nanoparticles delay the progression of diabetic osteoporosis via delivery of miR-150-5p

Extracellular vesicles derived from bone marrow mesenchymal stem cells (BMSC-EVs) are emerged as carriers of therapeutic targets against bone disorders, yet its isolation and purification are limited with recent techniques. Magnetic nanoparticles (MNPs) can load EVs with a unique targeted drug delivery system. We constructed gold-coated magnetic nanoparticles (GMNPs) by decorating the surface of the Fe3O4@SiO2 core and a silica shell with poly(ethylene glycol) (PEG)-aldehyde (CHO) and examined the role of BMSC-EVs loaded on GMNPs in diabetic osteoporosis (DO). The osteoporosis-related differentially expressed miR-150-5p was singled out by microarray analysis. DO models were then established in Sprague–Dawley rats by streptozotocin injection, where poor expression of miR-150-5p was validated in the bone tissues. Next, GMNPE was prepared by combining GMNPs with anti-CD63, after which osteoblasts were co-cultured with the GMNPE-BMSC-EVs. The re-expression of miR-150-5p facilitated osteogenesis in osteoblasts. GMNPE could promote the enrichment of EVs in the bone tissues of DO rats. BMSC-EVs delivered miR-150-5p to osteoblasts, where miR-150-5p targeted MMP14 and consequently activated Wnt/β-catenin pathway. This effect contributed to the enhancement of osteoblast proliferation and maturation. Furthermore, GMNPE enhanced the EV-based delivery of miR-150-5p to regulate the MMP14/Wnt/β-catenin axis, resulting in promotion of osteogenesis. Overall, our findings suggest the potential of GMNP-BMSC-EVs to strengthen osteoblast proliferation and maturation in DO, showing promise as an appealing drug delivery strategy against DO.Graphical abstract1. GMNPs-BMSCs-EVs-miR-150-5p promotes the osteogenesis of DO rats.2. miR-150-5p induces osteoblast proliferation and maturation by targeting MMP14.3. Inhibition of MMP14 activates Wnt/β-catenin and increases osteogenesis.4. miR-150-5p activates the Wnt/β-catenin pathway by downregulating MMP14.

M13 bacteriophage as biometric component for orderly assembly of dynamic light scattering immunosensor

The ordered assembly of nanostructure is an effective strategy used to manipulate the hydrodynamic diameter (DH) of nanoparticles. Herein, a versatile dynamic light scattering (DLS) immunosensing platform is presented to sensitively detect small molecules and biomacromolecules by using the M13 phage as the building module to order the assembly of gold nanoflowers and gold-coated magnetic nanoparticles, respectively. After the directional assembly of M13 phage, the DH of the probes was significantly increased due to its larger filamentous structure, thus improving the detection sensitivity of the DLS immunosensor. The designed M13 assembled DLS immunosensor with competitive and sandwich formats showed high sensitivities for ochratoxin A and alpha-fetoprotein in real corn and undiluted serum samples, with the detection limits of 1.37 and 57 pg/mL, respectively. These values are approximately 15.8 and 164.9 times lower than those of traditional phage-based enzyme-linked immunosorbent assays. Collectively, this work provides a promising strategy to manipulate the DH of nanoparticles by highly evolved biomaterials such as engineered M13 phages and opens upon a new direction for developing DLS immunosensors to detect various targets by the fusion expression of special peptide or nanobody on the pIII or pVIII protein of M13 phage.

Folate functionalized gold-coated magnetic nanoparticles effect in combined electroporation and radiation treatment of HPV-positive oropharyngeal cancer.

The rate of HPV-positive oropharyngeal cancer incidence is increasing, especially in the young population. While these patients show good responses to radiotherapy. The major complication of radiotherapy is normal tissue involvement. Thus, finding an effective treatment method is essential. Multimodal therapy with the lowest side effect could be an effective treatment method. Theranostic gold magnetic core-shell nanostructure was developed as aplatform for multimodal therapy of HPV-positive oropharyngeal cancer. The folate functionalized gold-magnetic core-shell nanostructure has been synthesized in a stepwise approach and characterized with various techniques including TEM, UV-Vis, and FTIR spectroscopy. KB was selected as a host for HPV and folate receptor-positive cancer. HGF as normal cell lines was selected. Both cell lines have been treated with nanoparticles, electric field and radiotherapy, either separately or in combination. Cell viability and apoptosis rate were determined by MTT and flow cytometry assay. In addition, cellular uptake of the nanoparticles was measured by ICP-OES analysis. The average size of folate functionalized gold-magnetic core-shell nanostructure was 13.8 ± 6.4nm. A characteristic plasmonic peak of gold nanoshells was observed in the UV-Vis spectrum. The functionalization of synthesized nanostructure was confirmed with FTIR spectroscopy. None of the treatments alone can cause a significant death in cancerous cells. Combination treatments can increase cancer cell mortality and increase the proportion of apoptotic cells in them. Furthermore, it has been observed that the electric field enhanced the cellular uptake of nanoparticles just in cancerous cells. Based on our findings, we conclude that the combination of folate functionalized nanoparticles and electroporation opens a new way to improve radiation therapy efficacy of HPV-positive cancers.

Textural Thermo-gravimetric and Magnetic Properties of Green Synthesised Water Dispersible Pristine and Gold Coated Superparamagnetic Iron Oxide Nanoparticles

Gold-coated magnetic nanoparticles have received a lot of attention in recent years due to their multifunctional attributes and their prospective unique characteristics in environmental and biomedical applications. This paper reports the textural, thermo-gravimetric, and magnetic properties of green synthesized gluconic acid-capped uncoated and gold-coated superparamagnetic iron oxide nanoparticles (SPION@Au). The as-synthesized nanomaterials were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), and superconducting quantum interference device (SQUID) magnetometry. The XRD and SEM measurements showed that the gluconic acid-capped magnetic core was coated with gold with cubical spinel crystalline structures. TGA results revealed the thermal stability of the nanoparticles. Textural properties indicated that the gold-coated nanoparticles were in naturally mesoporous and exhibited the type IV isotherm with an H2 hysteresis loop. The estimated maximum pore diameter and surface area of SPION@Au were 3.33 nm and 134.02 m²/g respectively. Furthermore, the SQUID results showed the nanocrystals were superparamagnetic with a blocking temperature (TB) of 214 K at 500 Oe and saturation magnetization of 11.38 emu/g. These noteworthy results demonstrated that the as-synthesized SPION@Au are promising nanomaterials for biomedical and analytical applications.

A fast, ultrasensitive SERS immunoassay to detect SARS-CoV-2 in saliva

The COVID-19 pandemic has emphasized the need for accurate, rapid, point-of-care diagnostics to control disease transmission. We have developed a simple, ultrasensitive single-particle surface-enhanced Raman spectroscopy (SERS) immunoassay to detect the SARS-CoV-2 spike protein in saliva. This assay relies on the use of single chain Fv (scFv) recombinant antibody expressed in E. coli to bind the SARS-CoV-2 spike protein. Recombinant scFv labeled with a SERS-active dye in solution is mixed with unlabeled scFv conjugated to gold-coated magnetic nanoparticles and a sample to be tested. In the presence of the SARS-CoV-2 spike protein, immunocomplexes form and concentrate the labeled scFv close to the gold surface of the nanoparticles, causing an increased SERS signal. The assay detects inactivated SARS-CoV-2 virus and spike protein in saliva at concentrations of 1.94 × 103 genomes mL−1 and 4.7 fg mL−1, respectively, making this direct detection antigen test only 2–3 times less sensitive than some qRT-PCR tests. All tested SARS-CoV-2 spike proteins, including those from alpha, beta, gamma, delta, and omicron variants, were detected without recognition of the closely related SARS and MERS spike proteins. This 30 min, no-wash assay requires only mixing, a magnetic separation step, and signal measurements using a hand-held, battery-powered Raman spectrometer, making this assay ideal for ultrasensitive detection of the SARS-CoV-2 virus at the point-of-care.

Surface Plasmon Resonance Immunosensor with Antibody-Functionalized Magnetoplasmonic Nanoparticles for Ultrasensitive Quantification of the CD5 Biomarker

A surface plasmon resonance (SPR) immunosensor signal amplification strategy based on antibody-functionalized gold-coated magnetic nanoparticles (mAuNPs) was developed for ultrasensitive and quantitative detection of the CD5 biomarker using an indirect sandwich immunoassay format. The gold surface of the SPR sensor disk and mAuNPs was modified with a self-assembled monolayer of 11-mercaptoundecanoic acid (11-MUA), and the coupling method using N-(3-(dimethylamino)propyl)-N′-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide was used to immobilize capture antibodies against human CD5 (anti-CD52A) and detection antibodies against human CD5 (anti-CD52B), respectively. The mAuNPs and anti-CD52B conjugates (mAuNPs–anti-CD52B) were separated by an external magnetic field and used to amplify the SPR signal after the formation of the anti-CD52A/CD5 immune complex on the SPR sensor disk. Compared to the direct CD5 detection with a limit of detection (LOD) of 1.04 nM and a limit of quantification (LOQ) of 3.47 nM, the proposed sandwich immunoassay utilizing mAuNPs–anti-CD52B significantly improved the LOD up to 8.31 fM and the LOQ up to 27.70 fM. In addition, it showed satisfactory performance in human blood serum (recovery of 1.04 pM CD5 was 109.62%). These results suggest that the proposed signal amplification strategy has superior properties and offers the potential to significantly increase the sensitivity of the analysis.

Different Effects of Reversible Electroporation-Mediated Fe3O4@AuNPs Delivery as Radiosensitizing Agents on Cancer Cells versus Normal Cells

Aim: In the present study, we sought to enhance the efficacy of radiotherapy via increasing the cellular uptake of Fe3O4@AuNPs as radiosensitizing agents using reversible electroporation, attaining a higher sensitivity for cancer cells to therapy-induced damage. Methods: The KB human nasopharyngeal carcinoma cell line was treated with different concentrations of gold-coated magnetic nanoparticles. The cells then received electroporation (750[Formula: see text]V/cm, 8 pulses for a duration 100[Formula: see text][Formula: see text]s with 100[Formula: see text]ms intervals) and radiotherapy (6MV X-ray, 2[Formula: see text]Gy). Control groups were carefully considered to assess the pure effect of both single and combinational therapeutic protocols. The MTT test and flow cytometry assay using Annexin V-PI kit were performed to evaluate potential effects on cell survival rate and to determine the induced level of apoptosis. Additionally, cellular uptake of nanoparticles was assessed and quantified using ICP-OES analysis. Results: Our study showed that nanoparticles and the applied procedure of electroporation had no considerable effects when utilized separately, but their combined application induced significant cell death ([Formula: see text]45%) and apoptosis ([Formula: see text]17%). Besides, the application of Fe3O4@AuNPs in the presence of electric field, 24[Formula: see text]h before the radiotherapy of tumor cells enhanced the cancer cell death ([Formula: see text]53%) as well as apoptosis rate ([Formula: see text]33%). The same scenario was also observed with normal HGF human gingival fibroblasts, confirmed by significantly lower levels of cell death and apoptosis. Conclusion: It can be concluded that electric fields at low voltage levels may significantly and selectively enhance the entry of nanoparticles into cancer cells, thereby accentuating the sensitivity of these cells to nanoparticle-mediated radiation therapy.

Rapid and ultrasensitive electrochemical detection of DNA methylation for ovarian cancer diagnosis

Alterations in DNA methylation, a stable epigenetic marker, are important components in the development of cancer. It is vital to develop diagnostic systems with the ability to rapidly quantify DNA methylation with high sensitivity and selectivity. However, the analysis of DNA methylation must address two main challenges: (i) ultralow abundance and (ii) differentiating methylated cytosine from normal cytosine on target DNA sequence in the presence of an overwhelming background of circulating cell-free DNA. Here we report the development of an ultrasensitive and highly-selective electrochemical biosensor for the rapid detection of DNA methylation in blood. The sensing of DNA methylation involves the hybridization on a network of probe DNA modified gold-coated magnetic nanoparticles (DNA-Au@MNPs) complementary to target DNA, and subsequently enzymatic cleavage to differentiate methylated DNA strands from corresponding unmethylated DNA strands. The biosensor presents a dynamic range from 2 aM to 20 nM for 110 nucleotide DNA sequences containing a single-site methylation with the lowest detected concentration of 2 aM. This DNA-Au@MNPs based sensor provides a promising method to achieve 35 min response time and minimally invasive diagnosis of ovarian cancer.

Magnetically Enhanced Liquid SERS for Ultrasensitive Analysis of Bacterial and SARS-CoV-2 Biomarkers.

In this work, it is shown that surface-enhanced Raman scattering (SERS) measurements can be performed using liquid platforms to perform bioanalysis at sub-pM concentrations. Using magnetic enrichment with gold-coated magnetic nanoparticles, the high sensitivity was verified with nucleic acid and protein targets. The former was performed with a DNA fragment associated with the bacteria Staphylococcus aureus, and the latter using IgG antibody, a biomarker for COVID-19 screening. It is anticipated that this work will inspire studies on ultrasensitive SERS analyzers suitable for large-scale applications, which is particularly important for in vitro diagnostics and environmental studies.

Treatment of tumour tissue with radio-frequency hyperthermia (using antibody-carrying nanoparticles).

Intelligent inorganic nanoparticles were designed and produced for use in imaging and annihilating tumour cells by radio‐frequency (RF) hyperthermia. Nanoparticles synthesised to provide RF hyperthermia must have magnetite properties. For this purpose, magnetite nanoparticles were first synthesised by the coprecipitation method (10–15 NM). These superparamagnetic nanoparticles were then covered with gold ions without losing their magnetic properties. In this step, gold ions are reduced around the magnetite nanoparticles. Surface modification of the gold‐coated magnetic nanoparticles was performed in the next step. A self‐assembled monolayer was created using cysteamine (2‐aminoethanethiol) molecules, which have two different end groups (SH and NH2). These molecules react with the gold surface by SH groups. The NH2 groups give a positive charge to the nanoparticles. After that, a monoclonal antibody (Monoclonal Anti‐N‐CAM Clone NCAM‐OB11) was immobilised by the 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide/N‐hydroxysuccinimide method. Then, the antenna RF system (144.00015 MHz) was created for RF hyperthermia. The antibody‐nanoparticle binding rate and cytotoxicity tests were followed by in vitro and in vivo experiments. As the main result, antibody‐bound gold‐coated magnetic nanoparticles were successfully connected to tumour cells. After RF hyperthermia, the tumour size decreased owing to apoptosis and necrosis of tumour cells.

Determination of Vascular Endothelial Growth Factor (VEGF) in Cell Culture Medium by Gold-Coated Magnetic Nanoparticle Based Label-Free Electrochemical Impedance Spectroscopy (EIS)

A gold-coated magnetic nanoparticle (MNPs@Au) based label-free electrochemical impedance spectroscopy (EIS) sensor is reported for determining vascular endothelial growth factor (VEGF) in cell culture media. VEGF antibodies (Ab) were modified on MNPs@Au to construct an Ab-bound magnetic complex (MNPs@Au-Ab) that was magnetically immobilized on a magnetic glassy carbon electrode (mGCE). The VEGF is captured on the MNPs@Au-Ab/mGCE, leading to increased electron-transfer resistance (R et) utilized for the determination of VEGF. Combining the highly efficient immobilization of antibodies on magnetic nanocomposites with the high sensitivity of electrochemical impedance spectroscopy, an excellent dynamic range for the VEGF concentration from 1.0 × 10−2 to 1.0 × 104 ng mL−1 was obtained with a detection limit of 2.43 pg mL−1. Quantitative determination and the investigation of the secretion of VEGF by various cells were also conducted. VEGF released by cancer cells (MDA-MB-231 cells and HCT116 cells) was significantly higher than for normal cells (L02 cells), which matched well with an enzyme linked immunosorbent assay (ELISA). These results show that the secretion of VEGF is associated with the metastatic level of cells. The reported sensor is expected to be applied in studies of cancer and tumor metastasis.