Improvement of Hyperthermia Properties of Iron Oxide Nanoparticles by Surface Coating

Magnetic hyperthermia is an oncological therapy that exploits magnetic nanoparticles activated by radiofrequency magnetic fields to produce a controlled temperature increase in a diseased tissue. The specific loss power (SLP) of magnetic nanoparticles or the capability to release heat can be improved using surface treatments, which can reduce agglomeration effects, thus impacting on local magnetostatic interactions. In this work, Fe3O4 nanoparticles are synthesized via a coprecipitation reaction and fully characterized in terms of structural, morphological, dimensional, magnetic, and hyperthermia properties (under the Hergt–Dutz limit). Different types of surface coatings are tested, comparing their impact on the heating efficacy and colloidal stability, resulting that sodium citrate leads to a doubling of the SLP with a substantial improvement in dispersion and stability in solution over time; an SLP value of around 170 W/g is obtained in this case for a 100 kHz and 48 kA/m magnetic field

Dual-responsive magnetic nanodroplets for controlled oxygen release via ultrasound and magnetic stimulation

Magnetic oxygen-loaded nanodroplets (MOLNDs) are a promising class of nanomaterials dually sensitive to ultrasound and magnetic fields, which can be employed as nanovectors for drug delivery applications, particularly in the field of hypoxic tissue treatment. Previous investigations were primarily focused on the application of these hybrid systems for hyperthermia treatment, exploiting magnetic nanoparticles for heat generation and nanodroplets as carriers and ultrasound contrast agents for treatment progress monitoring. This work places its emphasis on the prospect of obtaining an oxygen delivery system that can be activated by both ultrasound and magnetic fields. To achieve this goal, Fe3O4 nanoparticles were employed to decorate and induce the magnetic vaporization of OLNDs, allowing oxygen release. We present an optimized method for preparing MOLNDs by decorating nanodroplets made of diverse fluorocarbon cores and polymeric coatings. Furthermore, we performed a series of characterizations for better understanding how magnetic decoration can influence the physicochemical properties of OLNDs. Our comprehensive analysis demonstrates the efficacy of magnetic stimulation in promoting oxygen release compared to conventional ultrasound-based methods. We emphasize the critical role of selecting the appropriate fluorocarbon core and polymeric coating to optimize the decoration process and enhance the oxygen release performance of MOLNDs

Intracellular Function of Interleukin-1 Receptor Antagonist in Ischemic Cardiomyocytes

Background: Loss of cardiac myocytes due to apoptosis is a relevant feature of ischemic heart disease. It has been described in infarct and peri-infarct regions of the myocardium in coronary syndromes and in ischemia-linked heart remodeling. Previous studies have provided protection against ischemia-induced cardiomyocyte apoptosis by the anti-inflammatory cytokine interleukin-1 receptor-antagonist (IL-1Ra). Mitochondria triggering of caspases plays a central role in ischemia-induced apoptosis. We examined the production of IL-1Ra in the ischemic heart and, based on dual intra/extracellular function of some other interleukins, we hypothesized that IL-1Ra may also directly inhibit mitochondria-activated caspases and cardiomyocyte apoptosis. Methodology/Principal Findings: Synthesis of IL-1Ra was evidenced in the hearts explanted from patients with ischemic heart disease. In the mouse ischemic heart and in a mouse cardiomyocyte cell line exposed to long-lasting hypoxia, IL-1Ra bound and inhibited mitochondria-activated caspases, whereas inhibition of caspase activation was not observed in the heart of mice lacking IL-1Ra (Il-1ra−/−) or in siRNA to IL-1Ra-interfered cells. An impressive 6-fold increase of hypoxia-induced apoptosis was observed in cells lacking IL-1Ra. IL-1Ra down-regulated cells were not protected against caspase activation and apoptosis by knocking down of the IL-1 receptor, confirming the intracellular, receptor-independent, anti-apoptotic function of IL-1Ra. Notably, the inhibitory effect of IL-1Ra was not influenced by enduring ischemic conditions in which previously described physiologic inhibitors of apoptosis are neutralized. Conclusions/Significance: These observations point to intracellular IL-1Ra as a critical mechanism of the cell self-protection against ischemia-induced apoptosis and suggest that this cytokine plays an important role in the remodeling of heart by promoting survival of cardiomyocytes in the ischemic regions

Magnetocaloric Properties of MnBi Compound as a Function of Grain Size

MnBi is a magnetic material with many peculiar properties, interesting for different applications such as rare-earth-free permanent magnets and magnetic refrigeration. In this work the entropy change and the transformation kinetics of the magneto-structural transition are investigated, for two sets of samples with different grain size (“as-annealed” and “compacted pwd”). Both sets show a logarithm dependence on the temperature scan rate of the transition temperature upon cooling. This suggests that thermal activation effects are present. The estimated activation volume v0 of the magneto-structural transition corresponds to around 120 atoms.</jats:p

Magnetocaloric Properties of MnBi Compound as a Function of Grain Size

MnBi is a magnetic material with many peculiar properties, interesting for different applications such as rare-earth-free permanent magnets and magnetic refrigeration. In this work the entropy change and the transformation kinetics of the magneto-structural transition are investigated, for two sets of samples with different grain size (“as-annealed” and “compacted pwd”). Both sets show a logarithm dependence on the temperature scan rate of the transition temperature upon cooling. This suggests that thermal activation effects are present. The estimated activation volume v0 of the magneto-structural transition corresponds to around 120 atoms

Magnetic and Thermal Characterization of Core-Shell Fe-Oxide@SiO2 Nanoparticles for Hyperthermia Applications

Nanoparticles for magnetic hyperthermia pose significant constraints in their size and composition to ensure cellular uptake and biocompatibility, while still requiring significant hysteresis losses exploitable at electromagnetic field values and intensities not exceeding safety limits for the human body. In this paper, core-shell Fe-oxide@SiO 2 nanoparticles have been synthesized, and their size has been controlled so that the blocked-to-superparamagnetic transition is close to room temperature. Their size remains, therefore, as small as possible, while still displaying significant hysteresis losses in dynamic conditions (electromagnetic fields up to 48 kA/m at 100 kHz). Static loops measured by vibrating sample magnetometry and dynamic loops measured by a custom B-H tracer are used to characterize the particles' magnetic properties, as well as a custom-built, fully modeled, hyperthermia setup. The specific absorption rate is obtained either from static and dynamic loop areas or from direct hyperthermia measurements. Dynamic loops are shown to be a good estimator of specific absorption rate values