Micro-fabricated Magnetic Structures for the Future Medicine
Edis Osmanbasic posted on December 10, 2018 |
There are two methods of fabrication of magnetic structures: chemical and physical synthesis. (Image courtesy of LAGUNA DESIGN/SCIENCE PHOTO LIBRARY/CORBIS.)
There are two methods of fabrication of magnetic structures: chemical and physical synthesis. (Image courtesy of LAGUNA DESIGN/SCIENCE PHOTO LIBRARY/CORBIS.)

Nanotechnology is a rapidly growing field and has already been fused into all areas of science. Due to the unique electronic, optical, magnetic and biological properties of nano-scale materials, this technology opens enormous possibilities in the new generation of devices with advanced features. The U.S. National Nanotechnology Initiative (NNI)continuously provides significant budget and resources for developing nanotechnology, with emphasis on the healthcare applications. This article discusses the prospective medical applications of magnetic particles which can be detected and manipulated remotely by magnetic fields.

Different methods for fabrication of magnetic structures already exist.They allow a cost-effective mass production of a variety of magnetic structures with precisely controlled magnetic properties and geometry. The methods have been described in the research paper Microfabricated magnetic structures for future medicine: from sensors to cell actuators (Elina A Vitol, Valentyn Novosad, and Elena A Rozhkova).

In general, there are two methods: chemical and physical synthesis. Historically, the first magnetic carriers employed for biological studies were magnetic powders and particles synthesized by wet chemistry methods.

The chemical synthesis methods are a tool for producing small spherical particles. They are not convenient for creating multilayer structures with anisotropic shapes. Depending on their application, they can be synthesized using aqueous dispersions of iron oxide nanoparticles Fe3O4 or using organic-based routes. For example, the first one is used as an MRI contrast agent. The latter provides nanoparticles with diameters below 20nm. The nanoparticles in the diameter of 11–13nm are efficient for hyperthermia due to their large specific heat absorption rates. The issue with this kind of nanoparticles is that they are potentially cytotoxic. Because of that, the additional functionalization steps, such as ligand exchange or coating with a polymer, should be made.

Sophisticated physical fabrication techniques are bottom-up fabrication, nanoparticle, top-down fabrication, micro-fabrication and magnetization vortex state. These methods allow fabricating a variety of magnetic structures with tightly controlled magnetic properties. The micro-fabrication is an adequate method for mass production, which is important for the medical applications of magnetic carriers which require large amounts of particles.

The magnetic structure’s useful feature is in the fact that they can change their position, temperature and magnetization condition by using external magnetic field. This feature gives them great potential to be used in many biological and medicine applications such as drug delivery, molecular sensing, cell sorting, hyperthermia treatment, and MRI where the particles are used as contrast enhancement agents.

Magnetic drug delivery system under the influence of external magnetic field.  (Image courtesy of the ScienceDirect, Jae HyungPark.)
Magnetic drug delivery system under the influence of external magnetic field. (Image courtesy of the ScienceDirect, Jae HyungPark.)

Application of Magnetic Agents in Biomedicine

Chemically synthesized

Micro-fabricated structures

Super-paramagnetic beads:

Hyperthermia, MRI, gene delivery, cell separation

Ferromagnetic disks:

Magneto-mechanical actuation of cancer cell apoptosis, hyperthermia, MRI, magnetic detection combined with fluorescence imaging, drug release

Polymer-encapsulated particles (microspheres, beads, micelles):

Drug release, hyperthermia, MRI

Synthetic antiferromagnetic particles:

detection of low concentration analytes, magnetic detection combined with fluorescence methods

Nanowires:

cell separation

Integrated micro-fabricated platforms and magnetic tags

Magnetoresistance-based sensors:

multiplexed detection of cancer biomarkers, proteins, toxins, detection of hybridized DNA, point-of-care testing

Microfluidic chips:

 Cell sorting, cell patterning, transport and mixing of nanoliter amounts of analytes

The implementation of the micro-fabricated magnetic particles in biology and medicine is still in the early stage. This technology has a great potential to improve biomedical applications and so significant resources are being invested in the development and research of the nano-fabrication methods and technologies.

It is important to note that toxicity of nanoparticles employed in biomedicine should always be taken into account. Read more here.


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