Eduardo Guisasola

Magnetic-Responsive Release Controlled by Hot Spot Effect

Magnetically triggered drug delivery nanodevices have attracted great attention in nanomedicine, as they can feature as smart carriers releasing their payload at clinicians will. The key principle of these devices is based on the properties of magnetic cores to generate thermal energy in the presence of an alternating magnetic field. Then, the temperature increase triggers the drug release. Despite this potential, the rapid heat dissipation in living tissues is a serious hindrance for their clinical application. It is hypothesized that magnetic cores could act as hot spots, this is, produce enough heat to trigger the release without the necessity to increase the global temperature. Herein, a nanocarrier has been designed to respond when the temperature reaches 43 °C. This material has been able to release its payload under an alternating magnetic field without the need of increasing the global temperature of the environment, proving the efficacy of the hot spot mechanism in magnetic-responsive drug delivery devices.

Design of thermoresponsive polymeric gates with opposite controlled release behaviors

Stimuli-responsive devices are novel tools widely studied in the nanomedicine research field. In this work, magnetic-responsive mesoporous silica nanoparticles (MMSNs) were coated with an engineered thermoresponsive co-polymer. Magnetic cores are used as heating sources when they are exposed to an alternating magnetic field. The polymer structure suffers a change from hydrophilic to hydrophobic state when the temperature is raised above the lower critical solution temperature (LCST) or volume phase transition temperature (VPTT), acting as a gate-keeper of a model drug trapped inside the silica matrix. Fluorescein departure can be tuned employing two different polymer structures on the silica surface which exhibit the same transition temperature (42 °C) but a different grafting density: one of them being a dense crosslinked polymer network and the other one a hairy linear polymer layer. The release profile reveals to be the opposite between these two different coatings, allowing suitable drug release behavior for different clinical situations.

Beyond Traditional Hyperthermia: In Vivo Cancer Treatment with Magnetic-Responsive Mesoporous Silica Nanocarriers

In this study, we present an innovation in the tumor treatment in vivo mediated by magnetic mesoporous silica nanoparticles. This device was built with iron oxide magnetic nanoparticles embedded in a mesoporous silica matrix and coated with an engineered thermoresponsive polymer. The magnetic nanoparticles act as internal heating sources under an alternating magnetic field (AMF) that increase the temperature of the surroundings, provoking the polymer transition and consequently the release of a drug trapped inside the silica pores. By a synergic effect between the intracellular hyperthermia and chemotherapy triggered by AMF application, significant tumor growth inhibition was achieved in 48 h after treatment. Furthermore, the small magnetic loading used in the experiments indicates that the treatment is carried out without a global temperature rise of the tissue, which avoids the problem of the necessity to employ large amounts of magnetic cores, as is common in current magnetic hyperthermia.

Magnetically responsive polymers for drug delivery applications

Abstract This chapter gives an overview about magnetically activated devices, providing fundamental knowledge about the mechanisms and processes that occur in this type of materials. Magnetic induction brings the opportunity to cause a controlled drug release, generally addressed by using thermoresponsive polymers. This sort of device works on the basis of heat generation by magnetic nanoparticles (MNPs) exposed to an alternating magnetic field (AMF), which provokes the phase transition of a thermoresponsive polymer present in the composite. The magnetic properties and mechanisms implicated in the achievement of drug release will be briefly described. Inductive heating is an attractive trigger for drug delivery for potential clinical use, mainly due to its high penetration in tissues when compared to other external stimuli like ultrasound or light. These magnetic properties have been used to achieve drug release from polymer microspheres, liposomes, scaffolds, microcapsules, sheets, nanospheres, and inorganic nanoparticles. Two types of magnetically triggered systems will be discussed: macroscopic materials (e.g., membranes) and nanoparticulated drug delivery systems (DDSs). Besides the magnetic-induced drug delivery, some of these devices can enhance their therapeutic efficacy by means of magnetic guidance and hyperthermia.