Better than gold
Russian physicists have figured out how best to "burn out" cancer
Specialists of the National Research Nuclear University "MEPhI" (Moscow) together with colleagues from the University of Aix-Marseille (France) have proposed a new approach to the destruction of cancerous tumors and their metastases by "burning" them with laser radiation. The results of this work are published in the prestigious international scientific journal Scientific Reports (Popov et al., Laser–synthesized TiN nanoparticles as promising plasmonic alternative for biomedical applications).
One of the most promising methods of cancer treatment is the elimination of tumor cells with the help of their local hyperthermia (overheating) to 45-50 degrees – that is, to values exceeding the permissible temperature for a living organism. To avoid overheating of healthy tissues, local heating sensitizers are used. These substances, accumulating in the tumor, emit heat when exposed to external influences – for example, due to a magnetic field, ultrasound, radio frequency or infrared laser radiation.
In the latter case, nanoparticles of so-called highly conductive plasmonic metals, primarily gold, are considered the most promising. Plasmons are collective vibrations of electrons capable of absorbing and emitting energy in the form of light waves.
"Due to their chemical inertness and biocompatibility, gold nanoparticles could be the most promising for such tasks, but the need for plasmon absorption to enter the area of transparency of biological tissue will allow only complex forms of gold nanostructures (core-shell, nanocoils) to be used," the scientific director of the Engineering Physics Institute of Biomedicine (IFIB) told RIA Novosti NRU MEPhI Andrey Kabashin, who is also the Director of Research at the French National Center for Scientific Research CNRS (Marseille, France).
Such gold nanostructures either have too large a size (over 130 nanometers) relative to biological molecules, which makes it difficult to transfer them in a living organism and remove them from it, or contain toxic stabilizers, the scientist noted.
According to Kabashin, titanium nitride (TiN) is an attractive alternative to gold, since this substance has a peak of plasmon absorption shifted just to the area of transparency of biological tissues. However, the production of ultrapure small TiN nanoparticles using standard chemical synthesis methods is difficult.
Scientists of the IFIB MEPhI in collaboration with colleagues from France solved this problem by offering unique titanium nitride nanoparticles produced by laser ablation in water and organic liquids. This method consists in removing the substance from the surface with a laser pulse.
"Laser ablation makes it possible to synthesize ultrapure, perfectly spherical titanium nitride nanoparticles with a controlled average size," said Anton Popov, the lead author of the article, an employee of the MEPhI Research Institute.
According to him, it is "critically important" that even the smallest nanoparticles of 5-8 nanometers in size have a plasmon peak in the region of 650-700 nanometers, that is, in the field of transparency of biological tissues. "Such small nanoparticles are excreted from the body through the kidneys without any side effects," Popov noted.
"The first experiments to study the interaction of our nanoparticles with biological systems in vitro (in laboratory conditions outside a living organism – ed.) have shown excellent results. Laser-synthesized particles are practically non-toxic and can effectively generate heat when excited by infrared wavelengths of 670-800 nanometers. Moreover, our experiments have shown that such nanoparticles are really extremely effective in destroying cancer cells due to the hyperthermic effect," Andrei Kabashin added.
According to the authors of the work, titanium nitride is a unique material for biomedical applications, which promises a breakthrough in the development of noninvasive cancer treatment methods using local laser hyperthermia based on plasmon nanoparticles.
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