Hard-Soft Core-Shell Architecture Formation from Cubic Cobalt Ferrite Nanoparticles

Cubic bi-magnetic hard-soft core-shell nanoarchitectures were prepared starting from cobalt ferrite nanoparticles, prevalently with cubic shape, as seeds to grow a manganese ferrite shell. The combined use of direct (nanoscale chemical mapping via STEM-EDX) and indirect (DC magnetometry) tools was adopted to verify the formation of the heterostructures at the nanoscale and bulk level, respectively. The results showed the obtainment of core-shell NPs (CoFe₂O₄@MnFe₂O₄) with a thin shell (heterogenous nucleation). In addition, manganese ferrite was found to homogeneously nucleate to form a secondary nanoparticle population (homogenous nucleation). This study shed light on the competitive formation mechanism of homogenous and heterogenous nucleation, suggesting the existence of a critical size, beyond which, phase separation occurs and seeds are no longer available in the reaction medium for heterogenous nucleation. These findings may allow one to tailor the synthesis process in order to achieve better control of the materials' features affecting the magnetic behaviour, and consequently, the performances as heat mediators or components for data storage devices.

Biological Impact of γ-Fe2O3 Magnetic Nanoparticles Obtained by Laser Target Evaporation: Focus on Magnetic Biosensor Applications

The biological activity of γ-Fe2O3 magnetic nanoparticles (MNPs), obtained by the laser target evaporation technique, was studied, with a focus on their possible use in biosensor applications. The biological effect of the MNPs was investigated in vitro on the primary cultures of human dermal fibroblasts. The effects of the MNPs contained in culture medium or MNPs already uptaken by cells were evaluated for the cases of the fibroblast's proliferation and secretion of cytokines and collagen. For the tests related to the contribution of the constant magnetic field to the biological activity of MNPs, a magnetic system for the creation of the external magnetic field (having no commercial analogues) was designed, calibrated, and used. It was adapted to the size of standard 24-well cell culture plates. At low concentrations of MNPs, uptake by fibroblasts had stimulated their proliferation. Extracellular MNPs stimulated the release of pro-inflammatory cytokines (Interleukin-6 (IL-6) and Interleukin-8 (IL-8) or chemokine (C-X-C motif) ligand 8 (CXCL8)) in a concentration-dependent manner. However, the presence of MNPs did not increase the collagen secretion. The exposure to the uniform constant magnetic field (H ≈ 630 or 320 Oe), oriented in the plane of the well, did not cause considerable changes in fibroblasts proliferation and secretion, regardless of presence of MNPs. Statistically significant differences were detected only in the levels of IL-8/CXCL8 release.

Magnetoimpedance Thin Film Sensor for Detecting of Stray Fields of Magnetic Particles in Blood Vessel

Multilayered [FeNi (100 nm)/Cu (3 nm)]₅/Cu (500 nm)/[Cu (3 nm)/[FeNi (100 nm)]₅ structures were used as sensitive elements of the magnetoimpedance (MI) sensor prototype for model experiments of the detection of magnetic particles in blood vessel. Non-ferromagnetic cylindrical polymer rod with a small magnetic inclusion was used as a sample mimicking thrombus in a blood vessel. The polymer rod was made of epoxy resin with an inclusion of an epoxy composite containing 30% weight fraction of commercial magnetite microparticles. The position of the magnetic inclusion mimicking thrombus in the blood vessel was detected by the measurements of the stray magnetic fields of microparticles using MI element. Changes of the MI ratio in the presence of composite can be characterized by the shift and the decrease of the maximum value of the MI. We were able to detect the position of the magnetic composite sample mimicking thrombus in blood vessels. Comsol modeling was successfully used for the analysis of the obtained experimental results and the understanding of the origin the MI sensitivity in proposed configuration. We describe possible applications of studied configuration of MI detection for biomedical applications in the field of thrombus state evaluation and therapy.

Finding the Limits of Magnetic Hyperthermia on Core-Shell Nanoparticles Fabricated by Physical Vapor Methods

Magnetic nanoparticles can generate heat when exposed to an alternating magnetic field. Their heating efficacy is governed by their magnetic properties that are in turn determined by their composition, size and morphology. Thus far, iron oxides (e.g., magnetite, Fe3O4) have been the most popular materials in use, though recently bimagnetic core-shell structures are gaining ground. Herein we present a study on the effect of particle morphology on heating efficiency. More specifically, we use zero waste impact methods for the synthesis of metal/metal oxide Fe/Fe3O4 nanoparticles in both spherical and cubic shapes, which present an interesting venue for understanding how spin coupling across interfaces and also finite size effects may influence the magnetic response. We show that these particles can generate sufficient heat (hundreds of watts per gram) to drive hyperthermia applications, whereas faceted nanoparticles demonstrate superior heating capabilities than spherical nanoparticles of similar size.

Hybrid magnetic nanoparticles as efficient nanoheaters in biomedical applications

Heating at the nanoscale is the basis of several biomedical applications, including magnetic hyperthermia therapies and heat-triggered drug delivery. The combination of multiple inorganic materials in hybrid magnetic nanoparticles provides versatile platforms to achieve an efficient heat delivery upon different external stimuli or to get an optical feedback during the process. However, the successful design and application of these nanomaterials usually require intricate synthesis routes and their magnetic response is still not fully understood. In this review we give an overview of the novel systems reported in the last few years, which have been mostly obtained by organic phase-based synthesis and epitaxial growth processes. Since the heating efficiency of hybrid magnetic nanoparticles often relies on the exchange-interaction between their components, we discuss various interface-phenomena that are responsible for their magnetic properties. Finally, followed by a brief comment on future directions in the field, we outline recent advances on multifunctional nanoparticles that can boost the heating power with light and combine heating and temperature sensing in a single nanomaterial.

Coupled hard-soft spinel ferrite-based core-shell nanoarchitectures: magnetic properties and heating abilities

Bi-magnetic core-shell spinel ferrite-based nanoparticles with different CoFe₂O₄ core size, chemical nature of the shell (MnFe₂O₄ and spinel iron oxide), and shell thickness were prepared using an efficient solvothermal approach to exploit the magnetic coupling between a hard and a soft ferrimagnetic phase for magnetic heat induction. The magnetic behavior, together with morphology, stoichiometry, cation distribution, and spin canting, were investigated to identify the key parameters affecting the heat release. General trends in the heating abilities, as a function of the core size, the nature and the thickness of the shell, were hypothesized based on this systematic fundamental study and confirmed by experiments conducted on the water-based ferrofluids.

Specific Loss Power of Co/Li/Zn-Mixed Ferrite Powders for Magnetic Hyperthermia

An important research effort on the design of the magnetic particles is increasingly required to optimize the heat generation in biomedical applications, such as magnetic hyperthermia and heat-assisted drug release, considering the severe restrictions for the human body’s exposure to an alternating magnetic field. Magnetic nanoparticles, considered in a broad sense as passive sensors, show the ability to detect an alternating magnetic field and to transduce it into a localized increase of temperature. In this context, the high biocompatibility, easy synthesis procedure and easily tunable magnetic properties of ferrite powders make them ideal candidates. In particular, the tailoring of their chemical composition and cation distribution allows the control of their magnetic properties, tuning them towards the strict demands of these heat-assisted biomedical applications. In this work, Co_0.76Zn_0.24Fe₂O_4, Li_0.375Zn_0.25Fe_2.375O₄ and ZnFe₂O₄ mixed-structure ferrite powders were synthesized in a ‘dry gel’ form by a sol-gel auto-combustion method. Their microstructural properties and cation distribution were obtained by X-ray diffraction characterization. Static and dynamic magnetic measurements were performed revealing the connection between the cation distribution and magnetic behavior. Particular attention was focused on the effect of Co²⁺ and Li⁺ ions on the magnetic properties at a magnetic field amplitude and the frequency values according to the practical demands of heat-assisted biomedical applications. In this context, the specific loss power (SLP) values were evaluated by ac-hysteresis losses and thermometric measurements at selected values of the dynamic magnetic fields.

Mesoporous Carbon Nanoparticles as Multi-functional Carriers for Cancer Therapy Compared with Mesoporous Silica Nanoparticles

Mesoporous carriers have been widely used to deliver anticancer drugs due to their unique characteristics. In this work, mesoporous silica nanoparticles (MSN) and mesoporous carbon nanoparticles (MCN) with substantially similar and uniform particle size, specific surface area, and pore size were prepared to compare the photothermal effect, drug loading efficiencies (LE), and drug release properties. In order to improve the dispersion stability and biocompatibility of the carriers, MSN and MCN were grafted with PEG, respectively. The NIR-induced photothermal effect results indicated that MCN had a brilliant photothermal conversion efficiency due to its strong near-infrared absorption capacity, while MSN had no photothermal conversion capability. Moreover, LE of DOX in DOX/MCN-PEG reached 36.58%, higher than that in DOX/MSN-PEG, which was ascribed to non-covalent interaction of π-π stacking and electrostatic attraction. In addition, compared to DOX/MSN-PEG, DOX/MCN-PEG had a significantly increased release rate under NIR laser irradiation due to excellent photothermal conversion capability of MCN-PEG. Furthermore, cell viability assay and cellular uptake experiment results demonstrated that DOX/MCN-PEG showed a synergistic therapeutic effect in the combination of chemotherapy and phototherapy, with a combination index (CI) of 0.238.

Functionalized chitosan-modified defect-related luminescent mesoporous silica nanoparticles as new inhibitors for hIAPP aggregation

Human islet amyloid polypeptide (hIAPP or amylin) forms the amyloid deposits that is an important factor in the induction of type II diabetes. Accordingly, it is essential to efficiently and accurately inhibit the aggregation of hIAPP for the treatment and prevention of the disease. Here, defect mesoporous silica (DLMSN), with blue fluorescence, can perfectly achieve the accurate positioning in cells or organisms. DL@CS@NF cannot only specifically bind to a hIAPP monomer, but also effectively inhibit hIAPP aggregation, reduce cytotoxicity and overcome the instability and inefficiency of NF(N-Me)GA(N-Me)IL (NF). Furthermore, DL@CS@NF nanoparticles can significantly improve the survival rate of islet cells, stabilize the mitochondrial membrane potential, reduce the content of intracellular reactive oxygen species. In summary, DL@CS@NF nanoparticles may have broader implications in inhibiting the aggregation of hIAPP and reducing cytotoxicity.

Cyclodextrin–PEG conjugate-wrapped magnetic ferrite nanoparticles for enhanced drug loading and release

Magnetic nanoparticles are envisaged to overcome the impediments in the methods of targeted drug delivery and hence cure cancer effectively. We report herein, manganese ferrite nanoparticles, coated with β-cyclodextrin-modified polyethylene glycol as a carrier for the drug, camptothecin. The particles are of the size of ~ 100 nm and they show superparamagnetic behaviour. The saturation magnetization does not get diminished on polymer coverage of the nanoparticles. The β-cyclodextrin–polyethylene glycol conjugates are characterized using NMR and mass spectrometric techniques. By coating the magnetic nanoparticles with the cyclodextrin–tethered polymer, the drug-loading capacity is enhanced and the observed release of the drug is slow and sustained. The cell viability of HEK293 and HCT15 cells is evaluated and the cytotoxicity is enhanced when the drug is loaded in the polymer-coated magnetic nanoparticles. The noncovalent-binding based and enhanced drug loading on the nanoparticles and the sustained release make the nanocarrier a promising agent for carrying the payload to the target.

Targeted CT/MR dual mode imaging of human hepatocellular carcinoma using lactobionic acid-modified polyethyleneimine-entrapped gold nanoparticles

Multifunctional PEI-entrapped gold nanoparticles modified with lactobionic acid enable efficient targeted dual mode CT/MR imaging of human hepatocellular carcinoma.

The advantage of hollow mesoporous carbon as a near-infrared absorbing drug carrier in chemo-photothermal therapy compared with IR-820

In this study, we synthesized a kind of hollow mesoporous carbon (HMC) as near-infrared (NIR) nanomaterial and made a comparison between HMC and IR-820 commercially available in terms of heat generation properties and thermal stability exposed under NIR laser irradiation. The NIR-induced photothermal tests indicated that HMC had excellent heat generating capacity and remained stable after exposed to NIR laser irradiation for several times. On the contrary, the IR-820 was thermal unstable and degraded completely after exposed to NIR laser irradiation for only one time. The anticancer drug DOX was chosen as a model drug to evaluate the loading capacity and release properties of carboxylated HMC (HMC-COOH). The drug loading efficiency of HMC-COOH could reach to 39.7%. In vitro release results indicated that the release rate of DOX was markedly increased under NIR laser irradiation both in pH5.0 and pH7.4 PBS. Cell viability experiments indicated that HMC-COOH/DOX has a synergistic therapeutic effect by combination of chemotherapy and photothermal therapy. This present research demonstrated that HMC could be employed as NIR-adsorbing agents as well as drug carriers to load lots of drug, realizing the synergistic treatment of chemotherapy and photothermal therapy.

On-command controlled drug release by diels-Alder reaction using Bi-magnetic core/shell nano-carriers

A novel bi-functional thermo-responsive system, consisting of core/shell bi-magnetic nanoparticles with furan surface functionality, is bonded with N-(2-Carboxyethyl)maleimide through Diels-Alder reaction. The chemotherapeutics doxorubicin is attached onto the surface, with a high loading efficiency of 92%. This system with high responsiveness to a high frequency external alternating magnetic field shows a very good therapeutic efficiency in hyperthermia and drug release at relatively low temperatures (50°C). Polyhedron-shaped bi-magnetic nanoparticles (Zn_0.4Co_0.6Fe₂O₄@Zn_0.4Mn_0.6Fe₂O₄) exhibit a significant increase of the specific energy absorption rate up to 455W/g compared with the core nanoparticles (200W/g). Real-time florescence spectroscopy studies demonstrate rapid release of doxorubicin up to 50% in 5min and up to 92% after 15min upon exposure to high frequency external alternating magnetic field. The stability is evaluated for 8 weeks in phosphate buffer saline with a doxorubicin payload of 85%. In vitro studies using standard MTT cell assays with HeLa and Hep G2 lines prove an excellent biocompatibility with about 90% of cell viability after 24h of treatment within the highest concentration of functionalized magnetic nanoparticles (200μg/mL). The results indicate a controlled drug release mediated by thermo-responsive switching under applied alternating magnetic field.

Design of iron oxide-based nanoparticles for MRI and magnetic hyperthermia

Iron oxide nanoparticles are widely used for biological applications thanks to their outstanding balance between magnetic properties, surface-to-volume ratio suitable for efficient functionalization and proven biocompatibility. Their development for MRI or magnetic particle hyperthermia concentrates much of the attention as these nanomaterials are already used within the health system as contrast agents and heating mediators. As such, the constant improvement and development for better and more reliable materials is of key importance. On this basis, this review aims to cover the rational design of iron oxide nanoparticles to be used as MRI contrast agents or heating mediators in magnetic hyperthermia, and reviews the state of the art of their use as nanomedicine tools.