A unique development of Russian scientists
MSU physicists have created a magnetic field that helps implants to take root
MSU Press Service
A group of physicists from Russia, with the participation of Swiss colleagues, has developed a way to use the therapeutic effect of heating or cooling tissues due to the magnetocaloric effect. The scientists published an article with the results of their work in the latest issue of the International Journal of Refrigeration (Tishin et al., A review and new perspectives for the magnetocaloric effect: New materials and local heating and cooling inside the human body).
A group of scientists from Lomonosov Moscow State University has proposed a new method of applying the magnetocaloric effect for targeted drug delivery at the implant site. One of the authors of the work, Vladimir Zverev (Faculty of Physics, Lomonosov Moscow State University), claims that there are no analogues of this method using the negative magnetocaloric effect in the world.
The essence of the magnetocaloric effect (FEM) is that when exposed to an external magnetic field on a magnetic material, the temperature of this material changes, sometimes rising, and sometimes, on the contrary, falling (depending on the material). This important physical phenomenon was discovered in the century before last, although it was described as an effect only in 1917. Over the past century, the FEM has been studied in great detail, but the interest of researchers in it has not only not fallen, but, on the contrary, has increased dramatically in recent decades. This is explained, firstly, by the large amount of information about the physics of magnetic materials that can be extracted from this effect, and, secondly, by the rather extensive scope of its possible applications. It can be used with great success in low temperature physics, for the production of thermal machines, refrigeration units, etc.
However, most of these applications are not yet ready for commercial use, mainly due to the unavailability of technologies. If, for example, we talk about household magnetic refrigerators, then, although they are being developed today by many scientific and industrial laboratories around the world, according to one of the authors of the article Vladimir Zverev, an employee of the Physics faculty of Lomonosov Moscow State University, such refrigerators, if they were produced today, would be very expensive.
"Such refrigerators require a magnetic field of the order of one tesla, which, with today's capabilities, makes their prices very high and therefore commercially unacceptable – a device for generating such a field alone will cost at least fifteen hundred dollars. It remains to wait until they become cheaper," comments Vladimir Zverev.
However, this did not prevent the authors of the work from proposing a new application of the magnetocaloric effect, and almost ready for mass use – this time in medicine.
One of the methods developed by the researchers is called "magnetofluidic hypothermia" and is reduced to heating oncological neoplasms with special magnetic nanoparticles delivered to the tumor site. For this purpose, researchers have developed and created a unique installation for creating an alternating high-frequency magnetic field, which, as Vladimir Zverev assures, has no analogues in the world. Today, with the help of this installation, primary studies of cell cultures of various types of cancerous tumors have been carried out at the N.N. Blokhin Russian Scientific Cancer Center. Studies have also been conducted on mice that have proven the biocompatibility and non-toxicity of microparticles. Experiments are also being conducted on the pharmacokinetics of microparticles, with the help of which it is found out how they are retained in the tumor, how they are distributed in the body by blood flow, etc.
If the possibility of such a use of the magnetocaloric effect has at least been mentioned in the scientific literature – after all, it has long been known that heating a tumor can lead to its degradation – then the second technique proposed by scientists is completely unique.
As you know, one of the problems with implanting foreign bodies into the human body – artificial joints, abdominal nets, esophageal stents, urine and bile ducts, etc. - is the likelihood of their rejection. The authors of the article suggest applying a special coating consisting of several layers to the implants (even during their preparation for installation in the body). The first layer is a magnetic material that is cooled in an external magnetic field (a material with a negative magnetocaloric effect). This layer can be a thin film or a suspension of magnetic microparticles. The second layer is a polymer matrix, in which, as in a sponge, a medicinal substance is placed. The polymer matrix is in direct thermal contact with the magnetocaloric material. All this construction is placed in the body during the operation.
Samples of implants (abdominal nets) made of polypropylene coated.
The fact is that the polymer used in the technology, at a normal temperature inside the body, that is, at a temperature above 37 degrees, looks like jelly, which holds the medicine inside itself. When the magnetic field lowers the temperature of the magnetic material, the polymer turns into a liquid state and releases the drug at the implant site. For example, when inflammation occurs after the implant is installed, a non-invasive application of an external magnetic field (for example, in an MRI installation) will allow you to release the right portion of medication within the right time in the right place.
Such a method of "targeted" drug delivery is good, in particular, by the fact that it affects only the source of inflammation and is devoid of any connection with the rest of the body, that is, by definition, it is completely harmless to it. There is, however, a problem – it is not yet clear what to do if the medicine in the shell runs out.
Zverev claims that this problem is also solvable: "Firstly," he says, "in some cases, only one, "volley discharge" of a drug is needed, for example, necessary for the abdominal mesh to stick. And the release of dosed portions of the drug can be regulated by controlling the magnitude of the external magnetic field. It is also possible to replenish the shell with a new supply of medicine, using the fact that the medicine can be chemically combined with magnetic particles that can be "dragged" to the right place in the body by an external magnetic field. However, we have not developed this method, and it is now only in the form of an idea."
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24.08.2016