Nowadays, magnetic hyperthermia constitutes a complementary approach to cancer treatment. The use of magnetic particles as heating mediators, proposed in the 1950s, provides a novel strategy for improving tumor treatment and, consequently, patient quality of life. This review reports a broad overview about several aspects of magnetic hyperthermia addressing new perspectives and the progress on relevant features such as the ad hoc preparation of magnetic nanoparticles, physical modeling of magnetic heating, methods to determine the heat dissipation power of magnetic colloids including the development of experimental apparatus and the influence of biological matrices on the heating efficiency.Comment: 104 pages, 28 figures. Manuscript accepted for publication in Applied Physics Review

ABSTRACT:The polyol route is a versatile and up-scalable method to produce large batches of iron oxide nanoparticles with well-defined structure and magnetic properties. Controlling parameters such as temperature and duration of reaction, heating profile, nature of polyol solvent or of organometallic precursors were reported in previous studies of literature, but none of them described yet the crucial role of water in the forced hydrolysis pathway, whose presence is mandatory for nanoparticle production. This communication investigates the influence of the water amount and temperature at which it is injected in the reflux system for either pure polyol or mixture with a poly(hydroxy) amine. Distinct morphologies of nanoparticles were thereby obtained, from ultra-ultra-small smooth spheres down to 4 nm in diameter to large ones up to 37 nm in diameter. Nanoflowers were also synthesized, which are well-defined multi-core assemblies with narrow grain size dispersity. A diverse and large library of samples was obtained by playing on the nature of solvents and amount of water traces while keeping all the other parameters fixed. The varied morphologies lead to magnetic nanoparticles well-fitting to required applications among magnetic hyperthermia and MRI contrast agent, or both.

A thermo-responsive end-cap based on a retro-Diels-Alder and subsequent furan elimination reaction was developed. It was used to cap poly(ethyl glyoxylate), allowing end-to-end depolymerization upon thermal triggering. Using block copolymers, thermo-responsive micelles and vesicles were prepared and shown to disassemble upon heating. Thermal degradation could also be triggered indirectly by magnetic field hyperthermia after incorporation of iron oxide nanoparticles into the assemblies.

PEGylated magnetic iron oxide nanoparticles (IONPs) were synthesised with the aim to provide proof of concept results of remote cancer cell killing by magnetic fluid hyperthermia.

In this work, we have studied field-induced aggregation and magnetic separation—realized in a microfluidic channel equipped with a single magnetizable micropillar—of multicore iron oxide nanoparticles (IONPs) also called “nanoflowers” of an average size of 27 ± 4 nm and covered by either a citrate or polyethylene (PEG) monolayer having a thickness of 0.2–1 nm and 3.4–7.8 nm, respectively. The thickness of the adsorbed molecular layer is shown to strongly affect the magnetic dipolar coupling parameter because thicker molecular layers result in larger separation distances between nanoparticle metal oxide multicores thus decreasing dipolar magnetic forces between them. This simple geometrical constraint effect leads to the following important features related to the aggregation and magnetic separation processes: (a) Thinner citrate layer on the IONP surface promotes faster and stronger field-induced aggregation resulting in longer and thicker bulk needle-like aggregates as compared to those obtained with a thicker PEG layer; (b) A stronger aggregation of citrated IONPs leads to an enhanced retention capacity of these IONPs by a magnetized micropillar during magnetic separation. However, the capture efficiency Λ at the beginning of the magnetic separation seems to be almost independent of the adsorbed layer thickness. This is explained by the fact that only a small portion of nanoparticles composes bulk aggregates, while the main part of nanoparticles forms chains whose capture efficiency is independent of the adsorbed layer thickness but depends solely on the Mason number Ma. More precisely, the capture efficiency shows a power law trend Λ∝Ma−n, with n ≈ 1.4–1.7 at 300 < Ma < 104, in agreement with a new theoretical model. Besides these fundamental issues, the current work shows that the multicore IONPs with a size of about 30 nm have a good potential for use in biomedical sensor applications where an efficient low-field magnetic separation is required. In these applications, the nanoparticle surface design should be carried out in a close feedback with the magnetic separation study in order to find a compromise between biological functionalities of the adsorbed molecular layer and magnetic separation efficiency.

Thermometry at the nanoscale is an emerging area fostered by intensive research on nanoparticles (NPs) that are capable of converting electromagnetic waves into heat. Recent results suggest that stationary gradients can be maintained between the surface of NPs and the bulk solvent, a phenomenon sometimes referred to as "cold hyperthermia". However, the measurement of such highly localized temperatures is particularly challenging. We describe here a new approach to probing the temperature at the surface of iron oxide NPs and enhancing the understanding of this phenomenon. This approach involves the grafting of thermosensitive polymer chains to the NP surface followed by the measurement of macroscopic properties of the resulting NP suspension and comparison to a calibration curve built up by macroscopic heating. Superparamagnetic iron oxide NPs were prepared by the coprecipitation of ferrous and ferric salts and functionalized with amines, then azides using a sol-gel route followed by a dehydrative coupling reaction. Thermosensitive poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) with an alkyne end-group was synthesized by controlled radical polymerization and was grafted using a copper assisted azide-alkyne cycloaddition reaction. Measurement of the colloidal properties by dynamic light scattering (DLS) indicated that the thermosensitive NPs exhibited changes in their Zeta potential and hydrodynamic diameter as a function of pH and temperature due to the grafted PDMAEMA chains. These changes were accompanied by changes in the relaxivities of the NPs, suggesting application as thermosensitive contrast agents for magnetic resonance imaging (MRI). In addition, a new fibre-based backscattering setup enabled positioning of the DLS remote-head as close as possible to the coil of a magnetic heating inductor to afford in situ probing of the backscattered light intensity, hydrodynamic diameter, and temperature. This approach provides a promising platform for estimating the response of magnetic NPs to application of a radiofrequency magnetic field or for understanding the behaviour of other thermogenic NPs.

This work aims at designing functional biomaterials through selective chemical modification of xylan from beechwood. Acidic hydrolysis of xylan leaded to well-defined oligomers with an average of six xylose units per chain and with an aldehyde group at the reductive end. Reductive amination was performed on this aldehyde end-group to introduce an azide reactive group. 'Click chemistry' was then applied to couple these hydrophilic xylans moieties with different hydrophobic fatty acid methyl esters that were previously functionalized with complementary alkyne functions. The resulting amphiphilic bio-based conjugates were then self-assembled using three different methods, namely direct solubilization, thin-film rehydration/extrusion and microfluidics. Well-defined micelles and vesicles were obtained and their high loading capacity with propiconazole as an antifungal active molecule was shown. The resulting vesicles loaded with propiconazole in a microfluidic process, proved to significantly improve the antifungal activity of propiconazole, demonstrating the high potential of such xylan-based amphiphiles. 1-Introduction Knowing that the fossil fuel available on earth will be spent in the foreseeable future that the barrel price is quite volatile and because of environmental issues, the development of new chemicals from renewable resources is nowadays a strategic research area. Among the available renewable biomass, polysaccharides such as starch, pectin, cellulose and hemicelluloses, gums or arabinogalactan confer diverse functions of food reserve, cementing, ion balancing, structure, defense or cell adhesion [1]. Within the last two decades, there has been a growing interest in lignocellulosic biomass, which is a sustainable resource to produce fuels, chemicals and materials [2-4]. Contrarily to cellulose that is the most industrialized polysaccharide, woody hemicelluloses are less valued. The most abundant hemicellulosic polymers are xylans, essentially linear heteropolysaccharides, accounting for 25-35% of the dry biomass of woody tissues. Extensive literature data report on the isolation, characterization, derivatization and applications of xylans [5-9]. However, the chemical modification and the degradation of hemicelluloses into oligosaccharides are still a challenging task that would open the route to biomacromolecular engineering. Amphiphilic copolymers are composed of hydrophilic and hydrophobic segments that confer the behavior of self-assembly to these systems. Such materials can self-organize into nanoscale-size objects such as micelles, wormlike micelles or vesicles in solution, can form some well-defined assemblies at interfaces such as air-liquid, liquid-solid or air-solid and have been studied in the past recent years as nanosized reactors, nano-patterned surfaces for lithography, organic-inorganic mesostructures and drug delivery systems [10]. Polysaccharides-based amphiphiles are of particular interest due to their biocompatibility, bioactivity and biodegradability. Polysaccharides-based block copol...

A three steps synthesis route is proposed to generate thermosensitive and magnetically responsive γ‐Fe2O3@Wax@SiO2 sub‐micrometer capsules with a paraffinic core and a solid and brittle shell. The process integrates Pickering‐based emulsions, inorganic and sol–gel chemistries to promote monodisperse in size wax droplets, γ‐Fe2O3 nanoparticles and mineralization of the wax/water interfaces. Hybrid capsules are obtained with an average size around 800 nm, representing the first example of sub‐micrometer capsules generated employing Pickering emulsions as templates. Cetyltrimethylammonium bromide (CTAB) cationic surfactant added during mineralization at concentrations between 0.17 and 1.0 wt% impacts the shell density. The shell density seems to improve its mechanical strength while affording a low wax expansion volume without breaking for CTAB concentrations above 1.0 wt%. At lower CTAB concentration (0.17 wt%), the silica shell becomes less bulky and cannot resist the wax dilatation induced by the solid‐to‐liquid phase transition imposed by hyperthermia. The magnetically induced heating provided by the internal magnetic moments is sufficient to melt the wax core, expanding its volume, inducing thereby the surrounding silica shell rupture. Such γ‐Fe2O3@Stearic Acid@Wax@SiO2 sub‐micrometer capsules allow a sustained wax release with time, whereby 20% of the wax is released after 50 min of alternating magnetic field treatment.