Influence of the magnetic nanoparticle coating on the magnetic relaxation time

Abstract

Colloidal systems consisting of monodomain superparamagnetic nanoparticles have been used in biomedical applications, such as the hyperthermia treatment for cancer. In this type of colloid, called a nanofluid, the nanoparticles tend to agglomeration. It has been shown experimentally that the nanoparticle coating plays an important role in the nanoparticle dispersion stability and biocompatibility. However, theoretical studies in this field are lacking. In addition, the ways in which the nanoparticle coating influences the magnetic properties of the nanoparticles are not yet understood. In order to fill in this gap, this study presents a numerical simulation model that elucidates how the nanoparticle coating affects the nanoparticle agglomeration tendency as well as the effective magnetic relaxation time of the system. To simulate the self-organization of the colloidal nanoparticles, a stochastic Langevin dynamics method was applied based on the effective Verlet-type algorithm. The Néel magnetic relaxation time was obtained via the Coffey method in an oblique magnetic field, adapted to the local magnetic field on a nanoparticle.

Smart Magnetic Nanocarriers for Multi-Stimuli On-Demand Drug Delivery

“…At both temperatures, the saturation magnetization, M S , is high, confirming the high crystallinity of the inorganic core. As reported in Table 1 , the M S and the remanence M R of uncoated MNPs and MNCs at 300 K and 10 K are nearly equal for the two samples, and just a small difference is instead observed in the coercive field values that can be ascribed to the lower magnetic dipolar interaction between the magnetite cores in the coated samples due to the copolymer shell shielding [ 62 , 63 , 64 ].…”

A review on the effect of nanocomposite scaffolds reinforced with magnetic nanoparticles in osteogenesis and healing of bone injuries

“…To deal with this problem and to increase their stability, using a hydrophilic polymer substrate and covering magnetic nanoparticles is recommended [ 81 ]. Also, to prevent aggregation, magnetic nanoparticles should either be stabilized by electrostatic or steric repulsion [ 82 ]. Another limitation of MNPs is the toxicity related to size, shape, and chemistry, which should be considered before clinical use.…”

Understanding the Effect of Magnetic Field and Nanoparticle Concentration on Brownian Relaxation Time in Magnetic Nanofluids: A Semi-Analytical Model

“…We started from a model already used in various studies and evaluations in the specialized literature (Osaci and Cacciola 2015;Osaci and Cacciola 2017;Osaci and Cacciola 2021;Osaci and Cacciola 2021a;Osaci and Cacciola 2020). In our model, we replaced the evaluation of the Brownian relaxation time by the usual Debye with Equations (2)-( 6), which take into account both the concentration of particles in the nanofluid and the applied magnetic field.…”

“…Langevin equations for the translational and rotational motions of the nanoparticles were used to simulate selforganization of colloidal magnetic nanoparticles. We considered the following equations (Osaci and Cacciola 2017;Osaci and Cacciola 2021;Osaci and Cacciola 2021a;Osaci and Cacciola 2020) for the i-th nanoparticle in the base liquid:…”

“…The conservative torques acting on the nanoparticle is the magnetic torque and the random Brownian torque. These forces and moments are presented in detail by Osaci and Cacciola (2017), Osaci and Cacciola (2021), Osaci and Cacciola (2021a), Osaci and Cacciola (2020).…”