López Ortega, Alberto
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López Ortega
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Alberto
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InaMat2. Instituto de Investigación en Materiales Avanzados y Matemáticas
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Publication Open Access Fe3O4-SiO2 mesoporous core/shell nanoparticles for magnetic field-induced ibuprofen-controlled release(American Chemical Society, 2022-12-23) García Rodríguez, Lucía; Garayo Urabayen, Eneko; López Ortega, Alberto; Galarreta Rodríguez, Itziar; Cervera Gabalda, Laura María; Cruz Quesada, Guillermo; Cornejo Ibergallartu, Alfonso; Garrido Segovia, Julián José; Gómez Polo, Cristina; Pérez de Landazábal Berganzo, José Ignacio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA2020; Gobierno de Navarra / Nafarroako GobernuaHybrid magnetic nanoparticles made up of an iron oxide, Fe3O4, core and a mesoporous SiO2 shell with high magnetization and a large surface area were proposed as an efficient drug delivery platform. The core/shell structure was synthesized by two seed-mediated growth steps combining solvothermal and sol—gel approaches and using organic molecules as a porous scaffolding template. The system presents a mean particle diameter of 30(5) nm (9 nm magnetic core diameter and 10 nm silica shell thickness) with superparamagnetic behavior, saturation magnetization of 32 emu/g, and a significant AC magnetic-field-induced heating response (SAR = 63 W/gFe3O4, measured at an amplitude of 400 Oe and a frequency of 307 kHz). Using ibuprofen as a model drug, the specific surface area (231 m2/g) of the porous structure exhibits a high molecule loading capacity (10 wt %), and controlled drug release efficiency (67%) can be achieved using the external AC magnetic field for short time periods (5 min), showing faster and higher drug desorption compared to that of similar stimulus-responsive iron oxide-based nanocarriers. In addition, it is demonstrated that the magnetic field-induced drug release shows higher efficiency compared to that of the sustained release at fixed temperatures (47 and 53% for 37 and 42 °C, respectively), considering that the maximum temperature reached during the exposure to the magnetic field is well below (31 °C). Therefore, it can be hypothesized that short periods of exposure to the oscillating field induce much greater heating within the nanoparticles than in the external solution.Publication Open Access Nanoparticle size distribution and surface effects on the thermal dependence of magnetic anisotropy(American Chemical Society, 2022) Gomide, Guilherme; Cabreira Gomes, Rafael; Gomes Viana, Márcio; Cortez Campos, Álex Fabiano; Aquino, Renata; López Ortega, Alberto; Perzynski, Régine; Depeyrot, Jérõm; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaStandard approaches to investigate the anisotropy of nanoparticle assemblies are either by means of zero-field-cooled-field-cooled DC magnetization curves or by analyzing the coercivity at low temperatures. However, these methodologies are restricted to average values of an anisotropy constant, without probing its temperature dependence or symmetry. In this context, analyzing the thermal dependence of coercivity arises as a more comprehensive approach to assess anisotropic properties. Here, we investigate experimentally the thermal dependence of coercivity for cobalt ferrite nanoparticle samples synthesized by different methods, in a large range of nanoparticle diameters, resulting in samples with different internal structure, surface roughness, and size distribution. Our analysis consists of accounting for the size distribution and thermal dependence of the relevant variables, allowing us to access the anisotropy constant as a function of temperature. The results indicate that the surface plays an important role in the low-field determined anisotropy constants, with the thermal dependence pointing to a combination of types/sources of anisotropy affecting the coercivity. While the cubic magnetocrystalline anisotropy dominates for nanoparticles with higher diameter, the influence of surface contribution increases substantially for smaller sizes. The state of the surface is shown to be key for determining the main source of anisotropy.