Under the leadership of Petr Cígler of the Institute of Organic Chemistry and Biochemistry (IOCB Prague) and Martin Hrubý of the Institute for Macromolecular Chemistry (IMC), both of which are part of the Czech Academy of Sciences, a research group has developed a revolutionary method for easy and cheap irradiation of irradiated nanodiamonds and other nanomaterials suitable for use in highly sensitive diagnosis of diseases, including different types of cancer. Their article was published recently in the scientific newspaper nature Communications.
Diagnostic diseases and understanding of processes taking place within molecular-level cells require sensitive and selective diagnostic tools. Today, researchers can monitor magnetic and electric fields in cells with a resolution of several ten nanometers and with remarkable sensitivity due to crystal defects in the particles of certain inorganic materials. An almost ideal material for these purposes is diamond. Compared to the diamonds used in jewelry, those designed for applications in diagnostics and nanomedicine – nanodiamants – about one million times less and synthetically produced by graphite at high pressure and temperatures.
However, a pure nanodiamond does not reveal much about its environment. First of all, its crystal gratings must be damaged under controlled conditions to create special defects, so called nitrogen scanning centers, which allow for optical image processing. The damage is usually created by irradiating nanodiamonds with fast ions in particle accelerators. These accelerated ions manage to knock carbon atoms out of the crystal lattice of a nanodiamond leaving behind holes known as vacant sites, which at high temperatures couple with nitrogen atoms present in the crystal as pollutants. The newly formed nitrogen retrieval centers are a source of fluorescence, which can then be observed. It is precisely this fluorescence that gives nanodiamants huge potential for applications in medicine and technology.
However, a basic limitation on the use of these materials on a broader scale is the high cost and poor efficiency of irradiating ions in an accelerator, which prevents the emergence of this exceptionally valuable material in larger quantities.
The research group from several research centers with Petr Cígler and Martin Hrubý has recently published an article in the newspaper nature Communications describes a whole new method for irradiating nanocrystals. Instead of costly and time consuming irradiation in an accelerator, researchers used irradiation in a nuclear reactor, which is much faster and much cheaper.
But it was not that easy. The researchers had to use a trick – in the reactor, neutron irradiation borates atoms in very light and fast ions of helium and lithium. The nanocrystals must first be dispersed in molten boron oxide and then subjected to neutron irradiation in a nuclear reactor. Neutron capture of bore cores provides a dense shower of helium and lithium ions, which have the same effect within the nanocrystals as the ions produced in an accelerator: the controlled creation of crystal defects. The high density of this particle shower and the use of a reactor to irradiate a much larger amount of material means that it is easier and much cheaper to produce dozens of grams of rare nanomaterials at one time, which is about a thousand times more than scientists have so far obtained through comparable irradiation in accelerators.
The method has proved successful not only in the creation of defects in the lattice of nanodiamonds but also of another nanomaterial – silicon carbide. For this reason, researchers predict that the method could find universal use in large scale production of nanoparticles with defined defects.
The new method uses the principle used in borron nutritional capture therapy (BNCT), where patients are administered a boron compound. Once the compound has collected the tumor, the patient receives radiation therapy with neutrons, which divides the nuclei into ions of helium and lithium. These then destroy the tumor cells boran has collected. This principle, taken from experimental cancer treatment, has thus opened the door for efficient production of nanomaterials with exceptional potential for applications in, inter alia, the fields of cancer diagnosis.