Magnetically induced anisotropic structure in an injectable hydrogel for skeletal muscle regeneration.

Skeletal muscle integrity and its intrinsic aligned architecture are crucial for locomotion, postural support, and respiration functions, impacting overall quality of life. However, volumetric muscle loss (VML) can exceed intrinsic regenerative potential, leading to fibrosis and impairments. Autologous muscle grafting, the current gold standard, is constrained by tissue availability and success rates. Therefore, innovative strategies like cell-based therapies and scaffold-based approaches are needed. Our minimally invasive approach involves a tunable injectable hydrogel capable of achieving an aligned architecture post-injection via a low-intensity static magnetic field (SMF). Our hydrogel formulation uses gellan gum as the backbone polymer, enriched with essential extracellular matrix components such as hyaluronic acid and collagen type I, enhancing bio-functionality. To achieve an aligned architectural biomimicry, collagen type I is coupled with iron oxide magnetic nanoparticles, creating magnetic collagen bundles (MagC) that align within the hydrogel when exposed to a SMF. An extensive study was performed to characterize MagC and assess the hydrogel's stability, mechanical properties, and biological response in vitro and in vivo. The proposed system, fully composed of natural polymers, exhibited mechanical properties similar to human skeletal muscle and demonstrated effective biological performances, supporting its potential as a safe and patient-friendly treatment for VML.

Contactless magnetically responsive injectable hydrogel for aligned tissue regeneration.

Cellular alignment plays a pivotal role in several human tissues, including skeletal muscle, spinal cord and tendon. Various techniques have been developed to control cellular alignment using 3D biomaterials. However, the majority of 3D-aligned scaffolds require invasive surgery for implantation. In contrast, injectable hydrogels provide a non-invasive delivery method, gaining considerable attention for the treatment of diverse conditions, including osteochondral lesions, volumetric muscle loss, and traumatic brain injury. We engineered a biomimetic hydrogel with magnetic responsiveness by combining gellan gum, hyaluronic acid, collagen, and magnetic nanoparticles (MNPs). Collagen type I was paired with MNPs to form magnetic collagen bundles (MCollB), allowing the orientation control of these bundles within the hydrogel matrix through the application of a remote low-intensity magnetic field. This resulted in the creation of an anisotropic architecture. The hydrogel mechanical properties were comparable to those of human soft tissues, such as skeletal muscle, and proof of the aligned hydrogel concept was demonstrated. In vitro findings confirmed the absence of toxicity and pro-inflammatory effects. Notably, an increased fibroblast cell proliferation and pro-regenerative activation of macrophages were observed. The in-vivo study further validated the hydrogel biocompatibility and demonstrated the feasibility of injection with rapid in situ gelation. Consequently, this magnetically controlled injectable hydrogel exhibits significant promise as a minimally invasive, rapid gelling and effective treatment for regenerating various aligned human tissues.

Multiparametric modulation of magnetic transduction for biomolecular sensing in liquids.

The recent COVID19 pandemic has remarkably boosted the research on in vitro diagnosis assays to detect biomarkers in biological fluids. Specificity and sensitivity are mandatory for diagnostic kits aiming to reach clinical stages. Whilst the modulation of sensitivity can significantly improve the detection of biomarkers in liquids, this has been scarcely explored. Here, we report on the proof of concept and parametrization of a novel biosensing methodology based on the changes of AC magnetic hysteresis areas observed for magnetic nanoparticles following biomolecular recognition in liquids. Several parameters are shown to significantly modulate the transducing capacity of magnetic nanoparticles to detect analytes dispersed in saline buffer at concentrations of clinical relevance. Magnetic nanoparticles were bio-conjugated with an engineered recognition peptide as a receptor. Analytes are engineered tetratricopeptide binding domains fused to the fluorescent protein whose dimerization state allows mono- or divalent variants. Our results unveil that the number of receptors per particle, analyte valency and concentration, nanoparticle composition and concentration, and field conditions play a key role in the formation of assemblies driven by biomolecular recognition. Consequently, all these parameters modulate the nanoparticle transduction capacity. Our study provides essential insights into the potential of AC magnetometry for customizing biomarker detection in liquids.

Optomagnetic nanofluids for controlled brain hyperthermia: a critical study.

Optomagnetic nanofluids (OMNFs) are colloidal dispersions of nanoparticles (NPs) with combined magnetic and optical properties. They are especially appealing in biomedicine since they can be used as minimally invasive platforms for controlled hyperthermia treatment of otherwise difficultly accessible tumors such as intracranial ones. On the one hand, magnetic NPs act as heating mediators when subjected to alternating magnetic fields or light irradiation. On the other hand, suitably tailored luminescent NPs can provide a precise and remote thermal readout in real time. The combination of heating and thermometric properties allows, in principle, to precisely monitor the increase in the temperature of brain tumors up to the therapeutic level, without causing undesired collateral damage. In this work we demonstrate that this view is an oversimplification since it ignores the presence of relevant interactions between magnetic (γ-Fe2O3 nanoflowers) and luminescent nanoparticles (Ag2S NPs) that result in a detrimental alteration of their physicochemical properties. The magnitude of such interactions depends on the interparticle distance and on the surface properties of nanoparticles. Experiments performed in mouse brains (phantoms and ex vivo) revealed that OMNFs cannot induce relevant heating under alternating magnetic fields and fail to provide reliable temperature reading. In contrast, we demonstrate that the use of luminescent nanofluids (containing only Ag2S NPs acting as both photothermal agents and nanothermometers) stands out as a better alternative for thermally monitored hyperthermia treatment of brain tumors in small animal models.

Fine Control of In Vivo Magnetic Hyperthermia Using Iron Oxide Nanoparticles with Different Coatings and Degree of Aggregation.

The clinical implementation of magnetic hyperthermia has experienced little progress since the first clinical trial was completed in 2005. Some of the hurdles to overcome are the reliable production of magnetic nanoparticles with controlled properties and the control of the temperature at the target tissue in vivo. Here, forty samples of iron oxide superparamagnetic nanoparticles were prepared by similar methods and thoroughly characterized in terms of size, aggregation degree, and heating response. Selected samples were intratumorally administered in animals with subcutaneous xenografts of human pancreatic cancer. In vivo experiments showed that it is possible to control the rise in temperature by modulating the field intensity during in vivo magnetic hyperthermia protocols. The procedure does not require sophisticated materials and it can be easily implemented by researchers or practitioners working in magnetic hyperthermia therapies.

Superparamagnetic-blocked state transition under alternating magnetic fields: towards determining the magnetic anisotropy in magnetic suspensions.

The potential of magnetic nanoparticles for acting as efficient catalysts, imaging tracers or heating mediators relays on their superparamagnetic behaviour under alternating magnetic fields. In spite of the relevance of this magnetic phenomenon, the identification of specific fingerprints to unequivocally assign superparamagnetic behaviour to nanomaterials is still lacking. Herein, we report on novel experimental and theoretical evidences related to the superparamagnetism observed in magnetic iron oxide nanoparticle suspensions at room temperature. AC magnetization measurements in a broad field frequency range from mHz to kHz and field intensities up to 40 kA m-1 unambiguously demonstrate the transition from superparamagnetic to blocked states at room temperature. Our experimental observations are supported by a theoretical model based on the stochastic Landau-Liftshitz-Gilbert equation. An empirical expression is proposed to determine the effective magnetic anisotropy from the field frequency value beyond which AC magnetization shows hysteretic behaviour. Our results significantly improve the understanding and description of the superparamagnetism of iron oxide nanoparticles, paving the way towards a more efficient exploitation of their unique magnetic properties.

Di- and tri-component spinel ferrite nanocubes: synthesis and their comparative characterization for theranostic applications.

Spinel ferrite nanocubes (NCs), consisting of pure iron oxide or mixed ferrites, are largely acknowledged for their outstanding performance in magnetic hyperthermia treatment (MHT) or magnetic resonance imaging (MRI) applications while their magnetic particle imaging (MPI) properties, particularly for this peculiar shape different from the conventional spherical nanoparticles (NPs), are relatively less investigated. In this work, we report on a non-hydrolytic synthesis approach to prepare mixed transition metal ferrite NCs. A series of NCs of mixed zinc-cobalt-ferrite were prepared and their magnetic theranostic properties were compared to those of cobalt ferrite or zinc ferrite NCs of similar sizes. For each of the nanomaterials, the synthesis parameters were adjusted to obtain NCs in the size range from 8 up to 15 nm. The chemical and structural nature of the different NCs was correlated to their magnetic properties. In particular, to evaluate magnetic losses, we compared the data obtained from calorimetric measurements to the data measured by dynamic magnetic hysteresis obtained under alternating magnetic field (AMF) excitation. Cobalt-ferrite and zinc-cobalt ferrite NCs showed high specific adsorption rate (SAR) values in aqueous solutions but their heating ability was drastically suppressed once in viscous media even for NCs as small as 12 nm. On the other hand, non-stoichiometric zinc-ferrite NCs showed significant but lower SAR values than the other ferrites, but these zinc-ferrite NCs preserved almost unaltered their heating trend in viscous environments. Also, the presence of zinc in the crystal lattice of zinc-cobalt ferrite NCs showed increased contrast enhancement for MRI with the highest T2 relaxation time and in the MPI signal with the best point spread function and signal-to-noise ratio in comparison to the analogue cobalt-ferrite NC. Among the different compositions investigated, non-stoichiometric zinc-ferrite NCs can be considered the most promising material as a multifunctional theranostic platform for MHT, MPI and MRI regardless of the media viscosity in which they will be applied, while ensuring the best biocompatibility with respect to the cobalt ferrite NCs.

Unveiling the role of surface, size, shape and defects of iron oxide nanoparticles for theranostic applications.

Iron oxide nanoparticles (IONPs) are well-known contrast agents for MRI for a wide range of sizes and shapes. Their use as theranostic agents requires a better understanding of their magnetic hyperthermia properties and also the design of a biocompatible coating ensuring their stealth and a good biodistribution to allow targeting of specific diseases. Here, biocompatible IONPs of two different shapes (spherical and octopod) were designed and tested in vitro and in vivo to evaluate their abilities as high-end theranostic agents. IONPs featured a dendron coating that was shown to provide anti-fouling properties and a small hydrodynamic size favoring an in vivo circulation of the dendronized IONPs. While dendronized nanospheres of about 22 nm size revealed good combined theranostic properties (r2 = 303 mM s-1, SAR = 395 W gFe-1), octopods with a mean size of 18 nm displayed unprecedented characteristics to simultaneously act as MRI contrast agents and magnetic hyperthermia agents (r2 = 405 mM s-1, SAR = 950 W gFe-1). The extensive structural and magnetic characterization of the two dendronized IONPs reveals clear shape, surface and defect effects explaining their high performance. The octopods seem to induce unusual surface effects evidenced by different characterization techniques while the nanospheres show high internal defects favoring Néel relaxation for magnetic hyperthermia. The study of octopods with different sizes showed that Néel relaxation dominates at sizes below 20 nm while the Brownian one occurs at higher sizes. In vitro experiments demonstrated that the magnetic heating capability of octopods occurs especially at low frequencies. The coupling of a small amount of glucose on dendronized octopods succeeded in internalizing them and showing an effect of MH on tumor growth. All measurements evidenced a particular signature of octopods, which is attributed to higher anisotropy, surface effects and/or magnetic field inhomogeneity induced by tips. This approach aiming at an analysis of the structure-property relationships is important to design efficient theranostic nanoparticles.

Hydrotalcite-Embedded Magnetite Nanoparticles for Hyperthermia-Triggered Chemotherapy.

A magnetic nanocomposite, consisting of Fe3O4 nanoparticles embedded into a Mg/Al layered double hydroxide (LDH) matrix, was developed for cancer multimodal therapy, based on the combination of local magnetic hyperthermia and thermally induced drug delivery. The synthesis procedure involves the sequential hydrolysis of iron salts (Fe2+, Fe3+) and Mg2+/Al3+ nitrates in a carbonate-rich mild alkaline environment followed by the loading of 5-fluorouracil, an anionic anticancer drug, in the interlayer LDH space. Magnetite nanoparticles with a diameter around 30 nm, dispersed in water, constitute the hyperthermia-active phase able to generate a specific loss of power of around 500 W/g-Fe in an alternating current (AC) magnetic field of 24 kA/m and 300 kHz as determined by AC magnetometry and calorimetric measurements. Heat transfer was found to trigger a very rapid release of drug which reached 80% of the loaded mass within 10 min exposure to the applied field. The potential of the Fe3O4/LDH nanocomposites as cancer treatment agents with minimum side-effects, owing to the exclusive presence of inorganic phases, was validated by cell internalization and toxicity assays.

Infrared-Emitting Multimodal Nanostructures for Controlled In Vivo Magnetic Hyperthermia.

Deliberate and local increase of the temperature within solid tumors represents an effective therapeutic approach. Thermal therapies embrace this concept leveraging the capability of some species to convert the absorbed energy into heat. To that end, magnetic hyperthermia (MHT) uses magnetic nanoparticles (MNPs) that can effectively dissipate the energy absorbed under alternating magnetic fields. However, MNPs fail to provide real-time thermal feedback with the risk of unwanted overheating and impeding on-the-fly adjustment of the therapeutic parameters. Localization of MNPs within a tissue in an accurate, rapid, and cost-effective way represents another challenge for increasing the efficacy of MHT. In this work, MNPs are combined with state-of-the-art infrared luminescent nanothermometers (LNTh; Ag2 S nanoparticles) in a nanocapsule that simultaneously overcomes these limitations. The novel optomagnetic nanocapsule acts as multimodal contrast agents for different imaging techniques (magnetic resonance, photoacoustic and near-infrared fluorescence imaging, optical and X-ray computed tomography). Most crucially, these nanocapsules provide accurate (0.2 °C resolution) and real-time subcutaneous thermal feedback during in vivo MHT, also enabling the attainment of thermal maps of the area of interest. These findings are a milestone on the road toward controlled magnetothermal therapies with minimal side effects.

Whither Magnetic Hyperthermia? A Tentative Roadmap.

The scientific community has made great efforts in advancing magnetic hyperthermia for the last two decades after going through a sizeable research lapse from its establishment. All the progress made in various topics ranging from nanoparticle synthesis to biocompatibilization and in vivo testing have been seeking to push the forefront towards some new clinical trials. As many, they did not go at the expected pace. Today, fruitful international cooperation and the wisdom gain after a careful analysis of the lessons learned from seminal clinical trials allow us to have a future with better guarantees for a more definitive takeoff of this genuine nanotherapy against cancer. Deliberately giving prominence to a number of critical aspects, this opinion review offers a blend of state-of-the-art hints and glimpses into the future of the therapy, considering the expected evolution of science and technology behind magnetic hyperthermia.

Assessing the parameters modulating optical losses of iron oxide nanoparticles under near infrared irradiation.

Heating mediated by iron oxide nanoparticles subjected to near infrared irradiation has recently gained lots of interest. The high optical loss values reported in combination with the optical technologies already existing in current clinical practices, have made optical heating mediated by iron oxide nanoparticles an attractive choice for treating internal or skin tumors. However, the identification of the relevant parameters and the influence of methodologies for quantifying the optical losses released by iron oxide nanoparticles are not fully clear. Here, we report on a systematic study of different intrinsic (size, shape, crystallinity, and iron oxidation state) and extrinsic (aggregation, concentration, intracellular environment and irradiation conditions) parameters involved in the photothermal conversion of iron oxide nanoparticles under near infrared irradiation. We have probed the temperature increments to determine the specific loss power of iron oxide nanoparticles with different sizes and shapes dispersed in colloidal suspensions or inside live breast cancer cells. Our results underline the relevance of crystal surface defects, aggregation, concentration, magnetite abundance, excitation wavelength and density power on the modulation of the photothermal conversion. Contrary to plasmonic or magnetic losses, no significant influence of nanoparticle size nor shape was observed on the optical losses released by the studied iron oxide nanoparticles. Interestingly, no significant differences of measured temperature increments and specific loss power values were either observed when nanoparticles were inside live cells or in colloidal dispersion. Our findings highlight the advantages of optical heat losses released by iron oxide nanoparticles for therapeutic applications.

Iron-Based Core-Shell Nanowires for Combinatorial Drug Delivery and Photothermal and Magnetic Therapy.

Combining different therapies into a single nanomaterial platform is a promising approach for achieving more efficient, less invasive, and personalized treatments. Here, we report on the development of such a platform by utilizing nanowires with an iron core and iron oxide shell as drug carriers and exploiting their optical and magnetic properties. The iron core has a large magnetization, which provides the foundation for low-power magnetic manipulation and magnetomechanical treatment. The iron oxide shell enables functionalization with doxorubicin through a pH-sensitive linker, providing selective intracellular drug delivery. Combined, the core-shell nanostructure features an enhanced light-matter interaction in the near-infrared region, resulting in a high photothermal conversion efficiency of >80% for effective photothermal treatment. Applied to cancer cells, the collective effect of the three modalities results in an extremely efficient treatment with nearly complete cell death (∼90%). In combination with the possibility of guidance and detection, this platform provides powerful tools for the development of advanced treatments.

Confining Iron Oxide Nanocubes inside Submicrometric Cavities as a Key Strategy To Preserve Magnetic Heat Losses in an Intracellular Environment.

The design of magnetic nanostructures whose magnetic heating efficiency remains unaffected at the tumor site is a fundamental requirement to further advance magnetic hyperthermia in the clinic. This work demonstrates that the confinement of magnetic nanoparticles (NPs) into a sub-micrometer cavity is a key strategy to enable a certain degree of nanoparticle motion and minimize aggregation effects, consequently preserving the magnetic heat loss of iron oxide nanocubes (IONCs) under different conditions, including intracellular environments. We fabricated magnetic layer-by-layer (LbL) self-assembled polyelectrolyte sub-micrometer capsules using three different approaches, and we studied their heating efficiency as obtained in aqueous dispersions and after internalization by tumor cells. First, IONCs were added to the hollow cavities of LbL submicrocapsules, allowing the IONCs to move to a certain extent in the capsule cavities. Second, IONCs were coencapsulated into solid calcium carbonate cores coated with LbL polymer shells. Third, IONCs were incorporated within the polymer layers of the LbL capsule walls. In aqueous solution, higher specific absorption rate (SAR) values were related to those of free IONCs, while lower SAR values were recorded for capsule/core assemblies. However, after uptake by cancer cell lines (SKOV-3 cells), the SAR values of the free IONCs were significantly lower than those observed for capsule/core assemblies, especially after prolonged incubation periods (24 and 48 h). These results show that IONCs packed into submicrocavities preserve the magnetic losses, as the SAR values remained almost invariable. Conversely, free IONCs without the protective capsule shell agglomerated and their magnetic losses were strongly reduced. Indeed, IONC-loaded capsules and free IONCs reside inside endosomal and lysosomal compartments after cellular uptake and show strongly reduced magnetic losses due to the immobilization and aggregation in centrosymmetrical structures in the intracellular vesicles. The confinement of IONCs into sub-micrometer cavities is a key strategy to provide a sustained and predictable heating dose inside biological matrices.

Esterase-Cleavable 2D Assemblies of Magnetic Iron Oxide Nanocubes: Exploiting Enzymatic Polymer Disassembling To Improve Magnetic Hyperthermia Heat Losses.

Here, we report a nanoplatform based on iron oxide nanocubes (IONCs) coated with a bioresorbable polymer that, upon exposure to lytic enzymes, can be disassembled increasing the heat performances in comparison with the initial clusters. We have developed two-dimensional (2D) clusters by exploiting benchmark IONCs as heat mediators for magnetic hyperthermia and a polyhydroxyalkanoate (PHA) copolymer, a biodegradable polymer produced by bacteria that can be digested by intracellular esterase enzymes. The comparison of magnetic heat performance of the 2D assemblies with 3D centrosymmetrical assemblies or single IONCs emphasizes the benefit of the 2D assembly. Moreover, the heat losses of 2D assemblies dispersed in water are better than the 3D assemblies but worse than for single nanocubes. On the other hand, when the 2D magnetic beads (2D-MNBs) are incubated with the esterase enzyme at a physiological temperature, their magnetic heat performances began to progressively increase. After 2 h of incubation, specific absorption rate values of the 2D assembly double the ones of individually coated nanocubes. Such an increase can be mainly correlated to the splitting of the 2D-MNBs into smaller size clusters with a chain-like configuration containing few nanocubes. Moreover, 2D-MNBs exhibited nonvariable heat performances even after intentionally inducing their aggregation. Magnetophoresis measurements indicate a comparable response of 3D and 2D clusters to external magnets (0.3 T) that is by far faster than that of single nanocubes. This feature is crucial for a physical accumulation of magnetic materials in the presence of magnetic field gradients. This system is the first example of a nanoplatform that, upon exposure to lytic enzymes, such as those present in a tumor environment, can be disassembled from the initial 2D-MNB organization to chain-like assemblies with clear improvement of the heat magnetic losses resulting in better heat dissipation performances. The potential application of 2D nanoassemblies based on the cleavable PHAs for preserving their magnetic losses inside cells will benefit hyperthermia therapies mediated by magnetic nanoparticles under alternating magnetic fields.

Fe2+ Deficiencies, FeO Subdomains, and Structural Defects Favor Magnetic Hyperthermia Performance of Iron Oxide Nanocubes into Intracellular Environment.

Herein, by studying a stepwise phase transformation of 23 nm FeO-Fe3O4 core-shell nanocubes into Fe3O4, we identify a composition at which the magnetic heating performance of the nanocubes is not affected by the medium viscosity and aggregation. Structural and magnetic characterizations reveal the transformation of the FeO-Fe3O4 nanocubes from having stoichiometric phase compositions into Fe2+-deficient Fe3O4 phases. The resultant nanocubes contain tiny compressed and randomly distributed FeO subdomains as well as structural defects. This phase transformation causes a 10-fold increase in the magnetic losses of the nanocubes, which remain exceptionally insensitive to the medium viscosity as well as aggregation unlike similarly sized single-phase magnetite nanocubes. We observe that the dominant relaxation mechanism switches from Néel in fresh core-shell nanocubes to Brownian in partially oxidized nanocubes and once again to Néel in completely treated nanocubes. The Fe2+ deficiencies and structural defects appear to reduce the magnetic energy barrier and anisotropy field, thereby driving the overall relaxation into Néel process. The magnetic losses of these nanoparticles remain unchanged through a progressive internalization/association to ovarian cancer cells. Moreover, the particles induce a significant cell death after being exposed to hyperthermia treatment. Here, we present the largest heating performance that has been reported to date for 23 nm iron oxide nanoparticles under intracellular conditions. Our findings clearly demonstrate the positive impacts of the Fe2+ deficiencies and structural defects in the Fe3O4 structure on the heating performance into intracellular environment.

Dynamical Magnetic Response of Iron Oxide Nanoparticles Inside Live Cells.

Magnetic nanoparticles exposed to alternating magnetic fields have shown a great potential acting as magnetic hyperthermia mediators for cancer treatment. However, a dramatic and unexplained reduction of the nanoparticle magnetic heating efficiency has been evidenced when nanoparticles are located inside cells or tissues. Recent studies suggest the enhancement of nanoparticle clustering and/or immobilization after interaction with cells as possible causes, although a quantitative description of the influence of biological matrices on the magnetic response of magnetic nanoparticles under AC magnetic fields is still lacking. Here, we studied the effect of cell internalization on the dynamical magnetic response of iron oxide nanoparticles (IONPs). AC magnetometry and magnetic susceptibility measurements of two magnetic core sizes (11 and 21 nm) underscored differences in the dynamical magnetic response following cell uptake with effects more pronounced for larger sizes. Two methodologies have been employed for experimentally determining the magnetic heat losses of magnetic nanoparticles inside live cells without risking their viability as well as the suitability of magnetic nanostructures for in vitro hyperthermia studies. Our experimental results-supported by theoretical calculations-reveal that the enhancement of intracellular IONP clustering mainly drives the cell internalization effects rather than intracellular IONP immobilization. Understanding the effects related to the nanoparticle transit into live cells on their magnetic response will allow the design of nanostructures containing magnetic nanoparticles whose dynamical magnetic response will remain invariable in any biological environments, allowing sustained and predictable in vivo heating efficiency.

Emergence of the Stoner-Wohlfarth astroid in thin films at dynamic regime.

The Stoner-Wohlfarth (SW) model is the simplest model that describes adequately the magnetization reversal of nanoscale systems that are small enough to contain single magnetic domains. However for larger sizes where multi-domain effects are present, e.g., in thin films, this simple macrospin approximation fails and the experimental critical curve, referred as SW astroid, is far from its predictions. Here we show that this discrepancy could vanish also in extended system. We present a detailed angular-dependent study of magnetization reversal dynamics of a thin film with well-defined uniaxial magnetic anisotropy, performed over 9 decades of applied field sweep rate (dH/dt). The angular-dependent properties display a gradual transition from domain wall pinning and motion-like behaviour to a nucleative single-particle one, as dH/dt increases. Remarkably, in the high dynamic regime, where nucleation of reversed domains is the dominant mechanism of the magnetization reversal (nucleative regime), the magnetic properties including the astroid become closer to the ones predicted by SW model. The results also show why the SW model can successfully describe other extended systems that present nucleative regime, even in quasi-static conditions.

Nanoparticle-based hyperthermia distinctly impacts production of ROS, expression of Ki-67, TOP2A, and TPX2, and induction of apoptosis in pancreatic cancer.

So far, the therapeutic outcome of hyperthermia has shown heterogeneous responses depending on how thermal stress is applied. We studied whether extrinsic heating (EH, hot air) and intrinsic heating (magnetic heating [MH] mediated by nanoparticles) induce distinct effects on pancreatic cancer cells (PANC-1 and BxPC-3 cells). The impact of MH (100 µg magnetic nanoparticles [MNP]/mL; H=23.9 kA/m; f=410 kHz) was always superior to that of EH. The thermal effects were confirmed by the following observations: 1) decreased number of vital cells, 2) altered expression of pro-caspases, and 3) production of reactive oxygen species, and 4) altered mRNA expression of Ki-67, TOP2A, and TPX2. The MH treatment of tumor xenografts significantly (P≤0.05) reduced tumor volumes. This means that different therapeutic outcomes of hyperthermia are related to the different responses cells exert to thermal stress. In particular, intratumoral MH is a valuable tool for the treatment of pancreatic cancers.

Functionalized magnetic nanowires for chemical and magneto-mechanical induction of cancer cell death.

Exploiting and combining different properties of nanomaterials is considered a potential route for next generation cancer therapies. Magnetic nanowires (NWs) have shown good biocompatibility and a high level of cellular internalization. We induced cancer cell death by combining the chemotherapeutic effect of doxorubicin (DOX)-functionalized iron NWs with the mechanical disturbance under a low frequency alternating magnetic field. (3-aminopropyl)triethoxysilane (APTES) and bovine serum albumin (BSA) were separately used for coating NWs allowing further functionalization with DOX. Internalization was assessed for both formulations by confocal reflection microscopy and inductively coupled plasma-mass spectrometry. From confocal analysis, BSA formulations demonstrated higher internalization and less agglomeration. The functionalized NWs generated a comparable cytotoxic effect in breast cancer cells in a DOX concentration-dependent manner, (~60% at the highest concentration tested) that was significantly different from the effect produced by free DOX and non-functionalized NWs formulations. A synergistic cytotoxic effect is obtained when a magnetic field (1 mT, 10 Hz) is applied to cells treated with DOX-functionalized BSA or APTES-coated NWs, (~70% at the highest concentration). In summary, a bimodal method for cancer cell destruction was developed by the conjugation of the magneto-mechanical properties of iron NWs with the effect of DOX producing better results than the individual effects.