Under the leadership of Petr Cígler of the Institute of Organic Chemistry and Biochemistry (IOCB Prague) and Martin Hrubý of the Institute of Macromolecular Chemistry (IMC), both of whom are members of the Czech Academy of Sciences, a group of researchers are revolutionary the easy and inexpensive production of irradiated nanodiamonds and other nanomaterials suitable for use in highly sensitive diagnostic illnesses, including various types of cancer. Their article was recently published in the journal Nature Communications.
Diagnosing diseases and understanding the processes that take place within cells at the molecular level require sensitive and selective diagnostic instruments. Today, scientists can monitor magnetic and electric fields in cells with a resolution of several dozen nanometers and with remarkable sensitivity due to the crystalline defects in the particles of some inorganic materials. An almost ideal material for these purposes is diamond. Compared to diamonds used in jewelery, those intended for applications in diagnosis and nanomaterials – nanomaterials – are about one million times smaller and are synthetically produced from graphite at high pressure and temperatures.
A clean nanodiamond, however, does not reveal much about its environment. First, its crystalline lattice must be destroyed under controlled conditions to create specific defects, the so-called empty nitrogen centers, which allow visualization. Damage is usually caused by the irradiation of nanodiamonds with fast ions in particle accelerators. These accelerated ions are capable of knocking carbon atoms out of the nanodiamond's crystalline lattice, leaving behind holes known as vacant positions, which at mild temperatures then mate with the nitrogen atoms present in the crystal as contaminants. The newly created empty nitrogen centers are a source of fluorescence, which can then be observed. It's just this fluorescence that gives nanodiamonds a huge potential for applications in medicine and technology.
A fundamental limitation on the use of these materials on a wider scale, however, is the high cost and poor performance of the irradiating ions in an accelerator, which prevents the creation of this extremely valuable material in larger quantities.
The team of scientists from several research centers headed by Petr Cigler and Martin Hrubý has recently published an article in the journal Nature Communications describing a completely new nanocrystalline radiation method. Instead of costly and time-consuming radiation in an accelerator, scientists exploited radiation in a nuclear reactor, which is much faster and less expensive.
But it was not that simple. Scientists had to use a trick – in the reactor, neutron radiation breaks the atoms of boron into very light and fast ions of helium and lithium. Nanocrystals must first be dispersed in molten boron oxide and then subjected to neutron radiation in a nuclear reactor. Neutron binding from the boron nuclei produces a dense helium and lithium-ion showers, which have the same effect within nanocrystals, such as ions produced in an accelerator: the controlled generation of crystalline 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 more affordable to produce at the same time dozens of grams of rare nanomaterials, which are about a thousand times larger than scientists have so far achieved to acquire through accelerators comparable radiation.
The method proved to be successful not only for defects in the nanomaterial grid but also for another nanomaterial – silicon carbide. For this reason, scientists assume that the method could find global application in the production of large scale nanoparticles with defined defects.
The new method uses the principle applied to the treatment of boron neutron capture (BNCT), in which patients are given a boron compound. Once the compound is collected in the tumor, the patient is treated with neutron irradiation, which breaks the boron nuclei into helium and lithium. They destroy the tumor cells that have collected the boron. This principle derived from experimental cancer therapy has opened the door for effective nanomaterial production with excellent potential for applications, among others, in cancer diagnostics.