Direct 3D printing of zero valent iron@polylactic acid catalyst for tetracycline degradation with magnetically inducing active persulfate.

Catalyst stability has become a challenging issue for advanced oxidation processes (AOPs). Herein, we report an alternative method based on 3D printing technology to obtain zero-valent iron polylactic acid prototypes (ZVI@PLA) in a single step and without post etching treatment. ZVI@PLA was used to activate persulfate (PS) for the removal of Tetracycline (TC) in recirculating mode under two different heating methodologies, thermal bath and contactless heating promoted by magnetic induction (MIH). The effect of both heating methodologies was systematically analysed by comparing the kinetic constant of the degradation processes. It was demonstrated that the non-contact heating of ZVI by MIH reactivates the surface of the catalyst, renewing the surface iron content exposed to the pollutant solution, which makes the ZVI@PLA catalyst reusable up to 10 cycles with no efficiency reduction. In contrast, by using a conventional thermal bath, the kinetic constant gradually decreases over the 10 cycles, because of the superficial iron consumption, being the kinetic constant 5 times lower in the 10th run compared to MIH experiment. X-ray diffraction and Mössbauer spectroscopy confirmed the presence of metallic iron embedded in the ZVI@PLA prototype, whose crystalline structure remained unchanged for 10th cycles of MIH. Moreover, it was proven that with no contact heating technology at low magnetic fields (12.2 mT), the solution temperature does not increase, but only the surface of the catalyst does. Under these superficial heated conditions, kinetic rate is increased up to 0.016 min-1 compared to the value of 0.0086 min-1 obtained for conventional heating at 20 °C. This increase is explained not only by PS activation by iron leaching but also by the contribution of ZVI in the heterogeneous activation of persulfate.

How size, shape and assembly of magnetic nanoparticles give rise to different hyperthermia scenarios.

The use of magnetic nanoparticles (MNPs) to locally increase the temperature at the nanoscale under the remote application of alternating magnetic fields (magnetic particle hyperthermia, MHT) has become an important subject of nanomedicine multidisciplinary research, focusing among other topics on the optimization of the heating performance of MNPs and their assemblies under the effect of the magnetic field. We report experimental data of heat released by MNPs using a wide range of anisometric shapes and their assemblies in different media. We outline a basic theoretical investigation, which assists the interpretation of the experimental data, including the effect of the size, shape and assembly of MNPs on the MNPs' hysteresis loops and the maximum heat delivered. We report heat release data of anisometric MNPs, including nanodisks, spindles (elongated nanoparticles) and nanocubes, analysing, for a given shape, the size dependence. We study the MNPs either acting as individuals or assembled through a magnetic-field-assisted method. Thus, the physical geometrical arrangement of these anisometric particles, the magnetization switching and the heat release (by means of the determination of the specific adsorption rate, SAR values) under the application of AC fields have been analysed and compared in aqueous suspensions and after immobilization in agar matrix mimicking the tumour environment. The different nano-systems were analysed when dispersed at random or in assembled configurations. We report a systematic fall in the SAR for all anisometric MNPs randomly embedded in a viscous environment. However, certain anisometric shapes will have a less marked, an almost total preservation or even an increase in SAR when embedded in a viscous environment with certain orientation, in contrast to the measurements in water solution. Discrepancies between theoretical and experimental values reflect the complexity of the systems due to the interplay of different factors such as size, shape and nanoparticle assembly due to magnetic interactions. We demonstrate that magnetic assembly holds great potential for producing materials with high functional and structural diversity, as we transform our nanoscale building blocks (anisometric MNPs) into a material displaying enhanced SAR properties.

Superparamagnetic nanosorbent for water purification: Assessment of the adsorptive removal of lead and methyl orange from aqueous solutions.

The present study describes the preparation of 50.3 nm superparamagnetic nanosorbents with high surface area for the adsorptive removal of lead and methyl orange from water. This material is based on the surface modification of iron oxide superparamagnetic nanoparticles with a double-shell coating of mesoporous silica whose porosity was increased up to 570 m2/g by the addition of a porogenic material and its calcination. The adsorptive performance of the nanosorbent was evaluated as a function of several parameters (e.g. solution pH, pollutant initial concentration, and contact time), concluding that pHs around 5 are needed to avoid precipitation of Pb2+ as Pb(OH)2 and the equilibrium adsorption capacity is reached after 2 h in all cases. The experimental data on the adsorption capacity of lead and methyl orange onto the nanosorbent were fit to a pseudo-second order kinetic model and Langmuir isotherm model. The maximum adsorption capacity value increases from 35 up to 50 mg/gNS for lead removal with increasing nanosorbent surface area. Contrary, for methyl orange the maximum adsorption goes up to 240 mg/gNS, indicating a larger nanosorbent surface affinity for the organic matter that is able to diffuse through the silica pores as probed by the intraparticle diffusion model. In addition, we found an good reusability (100% recovering after 4 sorption/desorption cycles for methyl orange removal), which makes of this magnetic nanosorbent suitable for remediation technologies.

Maghemite nanoparticles coated with human serum albumin: combining targeting by the iron-acquisition pathway and potential in photothermal therapies.

Human serum albumin (HSA), the most abundant plasma protein in human blood, is a natural transport vehicle with multiple ligand binding sites. It, therefore, constitutes an attractive candidate for drug delivery. Targeting may occur via the most known interaction of the protein with the neonatal Fc receptor (FcRn). Here, we investigate another HSA delivery path, involving the transferrin receptor, and we elaborate a maghemite-HSA nanohybrid, opening up new opportunities for medical applications. Fluorescence spectrophotometric titration and size-exclusion chromatography were used to substantiate, in cell-free assays, an interaction between HSA and the transferrin receptor R1. This occurs with a dissociation constant, KD of 6.7 nM. This interaction was confirmed in HeLa cell culture where, by confocal microscopy, rhodamine-labeled HSA is shown to be internalized. HSA was then covalently conjugated onto maghemite nanoparticles (NPs) to give a NP-HSA nanohybrid. The therapeutic potential of this hybrid was demonstrated through its heating capacity in magnetic hyperthermia (MH) and near-infrared (NIR) photothermia (PT). In particular, the Specific Absorption Rate (SAR) in the PT Therapy (PTT) mode, using a 808 nm NIR-LASER (1 W cm-2) and at iron concentration as low as 2.5 mM, was found to be very high, equal to 1870 W g-1 with a temperature increment of 9.2 °C. The nanohybrids incubated with HeLa cells were mainly localized at the cell surface. When the PTT mode was applied under the same conditions as in vitro, mortality was higher in HeLa cells than in fibroblasts (non-malignant cells). Cytotoxicity was checked in both cell lines without the PTT mode; the nanohybrids do not seem to affect cell viability. These results make the nanohybrids very promising agents for NIR-PT and for targeting in cancer therapy, since non-malignant cells were not damaged.

Synthesis and characterization of CoFe2O4 ferrite nanoparticles obtained by an electrochemical method.

Uniform size cobalt ferrite nanoparticles have been synthesized in one step using an electrochemical technique. Synthesis parameters such as the current density, temperature and stirring were optimized to produce pure cobalt ferrite. The nanoparticles have been investigated by means of magnetic measurements, Mössbauer spectroscopy, x-ray powder diffraction and transmission electron microscopy. The average size of the electrosynthesized samples was controlled by the synthesis parameters and this showed a rather narrow size distribution. The x-ray analysis shows that the CoFe(2)O(4) obtained presents a totally inverse spinel structure. The magnetic properties of the stoichiometric nanoparticles show ferromagnetic behavior at room temperature with a coercivity up to 6386 Oe and a saturation magnetization of 85 emu g(-1).