Sub-Micrometer Magnetic Nanocomposites: Insights into the Effect of Magnetic Nanoparticles Interactions on the Optimization of SAR and MRI Performance

Abstract

There is increasing interest in the development of new magnetic polymeric carriers for biomedical applications such as trigger-controlled drug release, magnetic hyperthermia (MH) for the treatment of cancer, and as contrast agents in magnetic resonance imaging (MRI). This work describes the synthesis of sub-micrometer and magnetic polymer nanocomposite capsules (MPNCs) by combining in one single platform the biodegradable polymer poly-ε-caprolactone (PCL) and different concentrations of ∼8 nm oleic acid (OA)-functionalized magnetite nanoparticles (FeO@OA), employing the oil-in-water emulsion/solvent evaporation method. The MPNCs showed a significant increase in particle size from ∼400 to ∼800 nm as the magnetic loading in the organic-inorganic hybrids increases from 1.0% to 10%. The MPNCs presented high incorporation efficiency of FeO@OA nanoparticles, good colloidal stability, and super-paramagnetic properties. Interestingly, electron microscopy results showed that the FeO@OA nanoparticles were preferentially located at the surface of the capsules. Evaluation of the magnetic properties showed that the saturation magnetization and the blocking temperature of the MPNCs samples increased as a function of the FeO@OA loading. All the MPNCs exhibited heating when subjected to MH, and showed good specific absorption rates. Use of the formulations decreased the longitudinal (T) and transverse (T) relaxation times of water protons' nuclei, with excellent transverse relaxivity (r) values, especially in the case of the formulation with lowest FeO@OA loading. Furthermore, the MPNCs-cell interaction was studied, and MPNCs showed lower cellular toxicity to normal cells compared to cancer cells. These findings help in understanding the relationships between magnetic nanoparticles and polymeric capsules, opening perspectives for their potential clinical uses as simultaneous heating sources and imaging probes in MH and MRI, respectively.

Magnetic Hybrid Wax Nanocomposites as Externally Controlled Theranostic Vehicles: High MRI Enhancement and Synergistic Magnetically Assisted Thermo/Chemo Therapy

“…At 300 K, the saturation magnetization increases linearly with the concentration of magnetite, from a value of virtually 0 for S0 , to 4.5 emu g −1 for S7 (inset Figure , right). These values are within the range of those reported in the literature for other hybrid magnetic systems developed for biological applications and further confirm the observed MNPs encapsulation efficiency. Magnetic data demonstrate the superparamagnetic behavior of all the samples with null magnetization and quasi‐zero coercitivity in the absence of magnetic field at 300 K.…”

“…Next, the functional properties of the formulations were evaluated. A number of previous reports have highlighted the importance of magnetic couplings in confined systems for magnetic bio‐applications such as MRI or MH . For this reason, a careful characterization of the behavior of the mWNVs under applied magnetic (fixed or alternating) fields was performed.…”

“…SAR values do not increase with increasing magnetic loading but they get to a maximum in sample S5 . Similar effects were observed before in confined systems both for imaging and MH applications . A deeper analysis of the SAR was performed as a function of the frequency of the magnetic field under a fixed 20 mT field (Supporting Information, Figure S4).…”

“…An umber of previous reports have highlighted the importance of magnetic couplings in confined systemsf or magnetic bio-applications such as MRI or MH. [30,35] For this reason,acarefulc haracterization of the behavior of the mWNVsu nder appliedm agnetic (fixed or alternating) fields was performed. First, the performance of the formulations as T 2 contrast agentsi nM RI was studied.…”

Orthogonal Clickable Iron Oxide Nanoparticle Platform for Targeting, Imaging, and On‐Demand Release

“…The magnetic responseo fI ONs can be exploited for detection by magnetic resonance imaging (MRI) because IONs can be designedt oc reate different contrasts. [3,4] Similarly,t he magnetic properties can be used to label stem cells for cell-tracking applications, [5] to guide the nanomaterials to the desiredl ocation through the application of magnetic fields, [6] to increase temperature by magnetich yperthermia, [7,8] or to release ad rug on command through triggeredh eat production. [9][10][11][12] Therefore, magneticI ONs can act as theranostic probes, which pro-vide therapy and diagnosis simultaneously.…”