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Heating magnetic nanoparticles (MNPs) with AC (Alternating Current) magnetic fields has received significant attention in recent years, particularly for biomedical uses. However, most studies focus on characterizing the heat release, overlooking the fact that the MNPs in the viscous cell environment constitute a dynamic magnetic colloid whose configuration may evolve over time, particularly if a driving force as the AC field is applied. Aiming to shed light on this matter, in this workthe dynamics of the colloid structure during hyperthermia experiments are studied. By combining various experimental and theoretical tools, it is concluded that the AC field may drive the formation of aligned structures, and the impact that such structures may have on the associated heating is assessed. Remarkably, the results show that those field‐driven structures are highly unstable for small particle sizes, rapidly disassembling upon field removal. Moreover, an analogous behavior in vitro is found, with the AC magnetic field also promoting a reversible alignment of vesicles containing the MNPs within the cells. The results suggest that the observed alignment, both of MNPs and intracellular vesicles, may be a common phenomenon in usual hyperthermia experiments, but unnoticed because of the intrinsic unstable nature of the aligned structures. [ABSTRACT FROM AUTHOR]

One of the hallmarks of tissue repair is the production of reactive oxygen species (ROS), which modulate processes such as cell proliferation. Although several attempts have been made to manipulate ROS levels to increase tissue repair, the lack of techniques able to remotely manipulate the redox homeostasis with spatio–temporal fashion has hindered its progress. Herein, a new approach for tuning the ROS levels using magnetic nanoparticles (MNPs) that act as nanoheaters when exposed to an alternating magnetic field is presented. Two manganese–iron oxide (MnxFe3−xO4) MNPs (with a low and a high Mn2+ content) are designed and probed for the possibility of modulating the ROS balance by magneto–thermal stimulation in the invertebrate model organism Hydra vulgaris, able to fully regenerate. By evaluating the expression of selected genes involved in the maintenance of ROS homeostasis and proliferation pathways, a biphasic modulation of the ROS levels played by the MNPs is found. While MNPs with a lower Mn2+ content are able to positively modulate the regeneration potential under magnetostimulation, MNPs with a higher Mn2+ content cause a different redox imbalance, negatively affecting the regeneration dynamic. This innovative approach reveals a novel way of manipulating redox homeostasis that can advance in the field of tissue engineering. [ABSTRACT FROM AUTHOR]

Tuning the fundamental properties of iron oxide magnetic nanoparticles (MNPs) according to the required biomedical application is an unsolved challenge, as the MNPs' properties are affected by their composition, their size, the synthesis process, and so on. In this work, we studied the effect of zinc and manganese doping on the magnetic and structural properties of MNPs synthesized by the microwave-assisted polyol process, using diethylene glycol (DEG) and tetraethylene glycol (TEG) as polyols. The detailed morpho-structural and magnetic characterization showed a correspondence between the higher amounts of Mn and smaller crystal sizes of the MNPs. Such size reduction was compensated by an increase in the global magnetic moment so that it resulted in an increase of the saturation magnetization. Saturation magnetization M S values up to 91.5 emu/g and NMR transverse relaxivities r 2 of 294 s − 1 mM − 1 were obtained for Zn and Mn- doped ferrites having diameters around 10 nm, whereas Zn ferrites with diameters around 15 nm reached values of M S ∼ 97.2 emu/g and of r 2 ∼ 467 s − 1 mM − 1 , respectively. Both kinds of nanoparticles were synthesized by a simple, reproducible, and more sustainable method that makes them very interesting for diagnostic applications as MRI contrast agents. [ABSTRACT FROM AUTHOR]

Abstract Magnetic nanoparticles (MNPs) are promising tools for a wide array of biomedical applications. One of their most outstanding properties is the ability to generate heat when exposed to alternating magnetic fields, usually exploited in magnetic hyperthermia therapy of cancer. In this contribution, we provide a critical review of the use of MNPs and magnetic hyperthermia as drug release and gene expression triggers for cancer therapy. Several strategies for the release of chemotherapeutic drugs from thermo-responsive matrices are discussed, providing representative examples of their application at different levels (from proof of concept to in vivo applications). The potential of magnetic hyperthermia to promote in situ expression of therapeutic genes using vectors that contain heat-responsive promoters is also reviewed in the context of cancer gene therapy. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The authors describe enzyme based nanobiosensors for continuous monitoring of glucose, with the long term goal of using them as smart diagnostic tattoos. The method is founded on two main features: (1) The fluorescence intensity and decay times of glucose oxidase (GOx) and of GOx labeled with fluorescein (FS) or a ruthenium chelate (Ru) reversibly change during interaction with glucose; (2) The (labeled) enzyme is linked to magnetite magnetic nanoparticles (MNPs) which permits the MNPs to be physically manipulated. It is found that a stable link between MNPs and GOx is only accomplished if the number of amino groups on the GOX is artificially enlarged (to form GOx). Fluorescence decay data are best acquired with 8-nm MNPs where scattering is marginal; The activity of GOx is found not to be affected by immobilization on the MNPs. The various immobilized enzymes (GOx, GOx-FS and GOx-Ru; all on MNPs) differ only slightly in terms of linear response to glucose which ranged from 0.5 mM to at least 3.5 mM. The RSDs are about 5% (for n = 5), the detection limits are at ∼50 μM, and the sensor lifetimes are >1 week. [ABSTRACT FROM AUTHOR]