Russian nanoglucometer
A bio-sensor for measuring glucose levels was invented by Russian scientists
Tatiana Pichugina, Press Service of ITEB RAS
A bio-sensor capable of measuring the level of glucose in human blood was created by scientists from the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences in Pushchino, Moscow region. The bio-sensor is a polyelectrolyte microcapsule with an enzyme inside, which can be inserted under the human skin and read readings using an optical gadget. This concept is known as "smart tattoo".
Now diabetic patients measure blood glucose levels using miniature glucose meters. To do this, they have to take a blood sample from their finger. Is there a way to make a measurement without damaging the skin? Many scientific groups in the world are struggling with this task, but so far without much success. Reports about the invention of non-invasive glucose meters are constantly flashing in the media, but something is not visible on the counter. Scientists from Pushchino are also working on this task, and, who knows, it may be their bio-sensor that will be the first to enter the market.
The staff of ITEB RAS decided to adapt polyelectrolyte microcapsules, invented by them together with English and German colleagues, for a bio-sensor. Microcapsules are containers for storing and delivering any useful substance to the body. They are obtained chemically from polymers of synthetic and natural origin. Scientists are able to create many types of microcapsules depending on the tasks. In this case, it was necessary to form microcapsules from synthetic, but biocompatible compounds.
First, scientists synthesized a biomineral core from ordinary chalk and glucose oxidase, an enzyme that reacts with glucose. Then a multilayer shell of a pair of oppositely charged polyelectrolytes was formed around the core. This shell holds the enzyme inside the capsule, but does not prevent the penetration of glucose into it and the removal of reaction products. A fluorescent dye made of ruthenium salt was introduced between the layers of the shell.
– An enzyme was included in the capsule, a fluorescent dye was embedded, and the mineral core was dissolved. All – the sensor is ready. By taking fluorescence spectra, you can monitor how the glucose concentration in the test solution changes," explained Lyudmila Shabarchina, senior researcher at the Laboratory of Cytotechnology of the ITEB RAS, Candidate of Biological Sciences.
Microcapsules synthesized in this way can be injected under the skin of a diabetic patient. And quite a bit. It is enough to apply them in the form of a "smart tattoo" on a skin area of several millimeters. Glucose from the blood penetrates into the capsule and reacts with the enzyme. In turn, the dye embedded in the microcapsule shells responds to the products of this reaction. It begins to fluoresce, that is, to emit in a certain range. This radiation is recorded and converted into a numerical value by an optical sensor that a person applies to a tattoo.
Based on experimental data, scientists believe that such a "smart tattoo" can work for about a year, or even longer. No harmful substances are released under the skin during decomposition of microcapsules. In any case, the concentration of decay products is too negligible to cause any significant skin reaction.
The advantage of such bio-sensors is that the enzyme in the microcapsules remains active for a very long time, the microcapsules themselves gradually decompose without causing adverse reactions in the body. But the method has a weak point. The fact is that it is not yet possible to automate the synthesis of microcapsules. All attempts, and there were quite a few of them both here and abroad, only slightly reduced manual labor. The problem is that microcapsules tend to form large aggregates, which is unacceptable for most tasks. We have to synthesize microcapsules by treating them with ultrasound and monitoring each stage under a microscope. This procedure is worked out, but it takes a working day, and the number of capsules received is suitable only for scientific purposes. And if there is no mass production technology, then negotiations with investors to commercialize the development are difficult. A few years ago, scientists from ITEB RAS patented a method for the synthesis of microcapsules, in which it is possible to introduce up to 80% of the enzyme into the nucleus. The development of enzyme-containing microcapsules with fluorescent dye was carried out by an employee of the same laboratory, Candidate of Biological Sciences Lyubov Kazakova. This research has been supported for several years by subsidies from the Russian Ministry of Education and Science and grants from the Russian Foundation for Basic Research. The results attracted the attention of two colleagues at the Institute – senior researcher at the Laboratory of Radiation Molecular Biology Nikolay Sirota and senior researcher at the Laboratory of Energy of Biological Systems, Candidate of Biological Sciences Tatiana Sirota. They helped to investigate the activity of the enzyme using the polarographic method. The scientists published the results in the latest issue of the Journal of Physical Chemistry.
Scientific groups at the Institute of Bioorganic Chemistry are also working in a similar direction. Academicians M.M. Shemyakin and Yu.A. Ovchinnikov of the Russian Academy of Sciences and in the laboratory of remotely controlled systems for theranostics of Saratov State University, created by a megagrant by leading scientist Gleb Sukhorukov– the creator of microcapsules.
Scientists believe that microcapsules have a great future, because they open up new ways in science and medicine: the creation of analytical methods and targeted drug delivery.
– What is a polyelectrolyte capsule? You form several layers of polyelectrolytes on the microscopic core, remove the mineral base, rinse and get a container for carrying the substance to any place in the body. If you mark the container with a fluorescent dye, it is easy to trace where and in what quantity it has penetrated. Microcapsules made of biodegradable polymers are useful for delivering long-acting drugs to the body. They dissolve in the tissues for several hours or even days, and the drug contained in them slowly comes out. It replaces pills. And if magnetic particles are introduced into microcapsules, then they can be guided through the body in a directed magnetic field," Lyudmila Shabarchina said about the prospects of using microcapsules.
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