Magnetic Resonance Imaging (MRI) is a powerful, noninvasive and nondestructive technique, capable of providing three-dimensional (3D) images of living organisms. The use of magnetic contrast agents has allowed clinical researchers and analysts to significantly increase the sensitivity and specificity of MRI, since these agents change the intrinsic properties of the tissues within a living organism, increasing the information present in the images. Advances in nanotechnology and materials science, as well as the research of new magnetic effects, have been the driving forces that are propelling forward the use of magnetic nanostructures as promising alternatives to commercial contrast agents used in MRI. This review discusses the principles associated with the use of contrast agents in MRI, as well as the most recent reports focused on nanostructured contrast agents. The potential applications of gadolinium- (Gd) and manganese- (Mn) based nanomaterials and iron oxide nanoparticles in this imaging technique are discussed as well, from their magnetic behavior to the commonly used materials and nanoarchitectures. Additionally, recent efforts to develop new types of contrast agents based on synthetic antiferromagnetic and high aspect ratio nanostructures are also addressed. Furthermore, the application of these materials in theragnosis, either as contrast agents and controlled drug release systems, contrast agents and thermal therapy materials or contrast agents and radiosensitizers, is also presented.

Colorectal cancer is the third most common cancer worldwide. Despite recent advances in the treatment of this pathology, which include a personalized approach using radio- and chemotherapies in combination with advanced surgical techniques, it is imperative to enhance the performance of these treatments and decrease their detrimental side effects on patients’ health. Nanomedicine is likely the pathway towards solving this challenge by enhancing both the therapeutic and diagnostic capabilities. In particular, plasmonic nanoparticles show remarkable potential due to their dual therapeutic functionalities as photothermal therapy agents and as radiosensitizers in radiotherapy. Their dual functionality, high biocompatibility, easy functionalization, and targeting capabilities make them potential agents for inducing efficient cancer cell death with minimal side effects. This review aims to identify the main challenges in the diagnosis and treatment of colorectal cancer. The heterogeneous nature of this cancer is also discussed from a single-cell point of view. The most relevant works in photo- and radiotherapy using nanotechnology-based therapies for colorectal cancer are addressed, ranging from in vitro studies (2D and 3D cell cultures) to in vivo studies and clinical trials. Although the results using nanoparticles as a photo- and radiosensitizers in photo- and radiotherapy are promising, preliminary studies showed that the possibility of combining both therapies must be explored to improve the treatment efficiency.

Multi-segmented bilayered Fe/Cu nanowires have been fabricated through the electrodeposition in porous anodic alumina membranes. We have assessed, with the support of micromagnetic simulations, the dependence of fabricated nanostructures’ magnetic properties either on the number of Fe/Cu bilayers or on the length of the magnetic layers, by fixing both the nonmagnetic segment length and the wire diameter. The magnetic reversal, in the segmented Fe nanowires (NWs) with a 300 nm length, occurs through the nucleation and propagation of a vortex domain wall (V-DW) from the extremities of each segment. By increasing the number of bilayers, the coercive field progressively increases due to the small magnetostatic coupling between Fe segments, but the coercivity found in an Fe continuous nanowire is not reached, since the interactions between layers is limited by the Cu separation. On the other hand, Fe segments 30 nm in length have exhibited a vortex configuration, with around 60% of the magnetization pointing parallel to the wires’ long axis, which is equivalent to an isolated Fe nanodisc. By increasing the Fe segment length, a magnetic reversal occurred through the nucleation and propagation of a V-DW from the extremities of each segment, similar to what happens in a long cylindrical Fe nanowire. The particular case of the Fe/Cu bilayered nanowires with Fe segments 20 nm in length revealed a magnetization oriented in opposite directions, forming a synthetic antiferromagnetic system with coercivity and remanence values close to zero.

Magnetic Resonance Imaging (MRI) is a powerful, non-invasive and nondestructive tool, capable of providing three-dimensional (3D) images of living organisms. The use of magnetic contrast agents has allowed clinical researchers and analysts to enormously increase the sensitivity and specificity of MRI since these substances change the intrinsic properties of the tissues within a living body, increasing the information present in the images. The advances in nanotechnology and materials science as well as the research of new magnetic effects have been the driving forces that propel the use of magnetic nanostructures as promising alternatives to the commercial contrast agents used in MRI. This review discusses the principles associated with the use of contrast agents in MRI as well as the most recent reports focused on nanostructured contrast agents. The potential applications of gadolinium (Gd) and manganese Mn-based nanomaterials and iron oxide nanoparticles in this imaging technique are discussed as well, from their magnetic behavior to the mainly used materials and nanoarchitectures. Then, it is also addressed the recent efforts made to develop new types of contrast agents based on synthetic antiferromagnetic and high-aspect ratio nanostructures. Furthermore, the application of these materials in theragnosis, either as contrast agents and controlled drug release, contrast agents and thermal therapy or contrast agents and radiosensitizers, is also presented.

Domain wall (DW) movement in cylindrical magnetic nanowires has been extensively studied for applications in storage devices, sensors, and neuromorphic computing. The cylindrical wire geometry favors magnetization curling at the ends, nucleating vortex magnetic textures, which propagate as Bloch‐point DWs. Applying current pulses generates azimuthal Oersted fields that interact with the DW, promoting its propagation. Imperfections along the wire can pin the DW or nucleate additional vortex textures. Here we measured an individual Ni nanowire (diameter nm and length ) featuring thick non‐magnetic Au segments (length nm) to localize vortex magnetic textures upon field switching. Using current‐assisted anisotropic magnetoresistance measurements, we successfully detect vortex chirality near each Au segment and induce selective magnetic reversal below the propagation field. In the investigated nanowire, this method enabled the selective segment reversal at a low current density of A/, minimizing Joule heating. Furthermore, it offers a simple, cost‐effective, and non‐invasive approach for tracking vortex chirality along nanowires.