Magnetic Nanoparticles in Biology and Medicine: Past, Present, and Future Trends

The use of magnetism in medicine has changed dramatically since its first application by the ancient Greeks in 624 BC. Now, by leveraging magnetic nanoparticles, investigators have developed a range of modern applications that use external magnetic fields to manipulate biological systems. Drug delivery systems that incorporate these particles can target therapeutics to specific tissues without the need for biological or chemical cues. Once precisely located within an organism, magnetic nanoparticles can be heated by oscillating magnetic fields, which results in localized inductive heating that can be used for thermal ablation or more subtle cellular manipulation. Biological imaging can also be improved using magnetic nanoparticles as contrast agents; several types of iron oxide nanoparticles are US Food and Drug Administration (FDA)-approved for use in magnetic resonance imaging (MRI) as contrast agents that can improve image resolution and information content. New imaging modalities, such as magnetic particle imaging (MPI), directly detect magnetic nanoparticles within organisms, allowing for background-free imaging of magnetic particle transport and collection. “Lab-on-a-chip” technology benefits from the increased control that magnetic nanoparticles provide over separation, leading to improved cellular separation. Magnetic separation is also becoming important in next-generation immunoassays, in which particles are used to both increase sensitivity and enable multiple analyte detection. More recently, the ability to manipulate material motion with external fields has been applied in magnetically actuated soft robotics that are designed for biomedical interventions. In this review article, the origins of these various areas are introduced, followed by a discussion of current clinical applications, as well as emerging trends in the study and application of these materials.

Hard topological versus soft geometrical magnetic particle transport

Geometrical displacement of transported ferrofluid droplets (red) versus topological displacement of transported doublets and single spheres.

Parametric Investigation of Magnetic Particle Transport for Targeted Drug Delivery Applications

In recent years, there has been significant clinical and research interest in magnetic drug targeting (MDT). MDT allows the targeted delivery of drugs only to the affected sites, alleviating the rest of the body from the potential toxic or other side effects of the drug. The underlying concept of MDT is to attach drugs to small magnetic particles which can then be manipulated by a magnetic field designed to attract the drug carrying particles to the target site [1]. This will lead to increasing localized accumulation of the drug at the target site. MDT can have great implications on pharmaceutical treatments, ranging from oncology to cardiology and beyond [2, 3].