Frost under the skin: the ice meter will help achieve ultra-sharp MRI images

Russian scientists have developed a new technology that makes it possible to micro-monitor the process of ice formation even in the most turbid solutions, as well as accurately record the moment of transition of a substance from a liquid to a solid state. This is important, for example, for the production of drugs or magnetic nanoparticles used in contrast agents for MRI diagnostics. According to doctors, good contrast quality greatly increases the diagnostic value of the images. And according to scientific experts, in addition to medicine, the proposed technology will find application in both the food and chemical industries.

Control of ice formation

Skoltech specialists have developed a new technology that allows real-time monitoring of the ice formation process in any, even cloudy solutions. With its help, you can see the growth of ice crystals inside the sample and determine the exact moment of its complete freezing. The technique makes it possible to select and maintain the optimal freezing rate for each chemical composition, which is necessary, for example, in the production of promising drug delivery systems inside the body or contrast agents for MRI based on iron oxide nanoparticles.

— Until now, accurate control of the crystallization rate during these processes has been difficult due to the lack of suitable methods for recording the phase transition directly during the experiment. Our development solves this problem. We can not only record the very moment of freezing of water, but also accurately track the speed at which ice grows inside a solution with particles," said Sergey German, the first author of the article, a senior researcher at the Center for Photonics and Photonic Technologies at Skoltech.

The method is based on the photoacoustic effect. Scientists send short laser pulses to the sample, which are absorbed by the material. It experiences thermoelastic deformations and, as a result, generates an ultrasonic wave. By analyzing the parameters of this wave and the delay in its registration, it is possible to determine exactly where water turns into ice inside the sample and how fast this boundary is moving.

Using the technology, it is possible to optimize the production of complex micro- and nanostructured materials for biomedicine, such as drug delivery carriers. It allows you to load a large number of active components inside porous microparticles and microcapsules. The result is particles with predictable properties and a minimal number of aggregates, which directly increases their effectiveness and safety in medical use.

Practical application

The technique also allows you to receive feedback to determine the moment of complete freezing of the sample. This significantly reduces the time of the technological cycle. Previously, the process of loading particles with an active substance was almost blind and required a lot of time, and the new technology makes it possible to speed up this method five times.

"The photoacoustic approach, which has proven itself well in biomedical imaging, is becoming a convenient monitoring tool for functional materials technologies in our work. We are getting not just a way to accelerate the selection of parameters and standardize the production of nano- and microstructural materials, but a research tool. It is important for the transition from empirical parameter selection to the conscious design of materials with complex, specified architecture and functionality, for example, to create more effective theranostic platforms of a new generation — modern biomedical systems that combine two key functions: diagnosis and treatment within a single targeted approach," said the professor of the Center for Photonics and Photonic Technologies Skoltech Dmitry Gorin.

The development is especially useful for working with highly scattering and absorbing solutions, where other optical analysis methods are ineffective. It opens the way to optimizing the production of materials with specified properties, the scientists emphasized.

The quality of magnetic nanoparticles in contrast agents for MRI plays an important role in diagnosis, said Natalia Volkonskaya, Head of the X-ray Diagnostics Department at the Zdorovye Clinical Diagnostic Center.

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— Contrast is very important for MRI. It increases the diagnostic value of the image at least twice and increases the accuracy of diagnosis. It is used in many difficult cases, for example, to identify the edges of a resection. Without contrast, the size of the formation may seem different. Almost all cancer patients need to be contrasted," she said.

As RAS Professor Alexander Mazhuga told Izvestia, the proposed technology has great practical potential.

— If we talk about the macro scale, then in large volumes there is a large set of physico-chemical methods that allow us to evaluate the phase transition from a liquid, for example, to a solid or from a liquid to a gaseous phase. However, at the microlevel, at the level of single atoms, the production of nanoparticles from solution is a very important and necessary innovation. It can be used in pharmaceuticals, the food industry, in micro- and low—tonnage chemical industries," he believes.

The technology is particularly important for the production of magnetite nanoparticles, which are used as targeted drugs for drug delivery and as contrast agents for magnetic resonance imaging. Obtaining them in a certain narrow amount is the key to successful application in biomedicine, the specialist emphasized.