The demand for next-gen bone material driven by shifting situation
Right now, researchers from the VU Faculty of Chemistry and Geosciences spend most of their time working with calcium phosphates, which are vital to the human body and are the key non-organic element of bones. In the words of Dr Žarkovas, the synthesis of various calcium phosphates that they engage in is gaining significance for the mankind, because the human population is ageing and is facing an increasing amount of bone problems.
"One of the most frequently occurring problems is the decrease in the density of the bones as they age. For instance, you have to attach an implant the jawbone with screws and cannot do it because and the bone has melted away and needs to be regrown. Here’s another example: In 1990, there were 1.6 million femoral neck fractures in the world and, considering the current level of development, this figure can be expected to reach 6 million fractures per year by 2050. This problem is becoming more and more urgent and the bone cannot always heal itself after a serious injury; as a result, people are looking for new materials to implant in the bone, filling the void with artificial bone with different materials, such as calcium phosphates," the researcher says.
For them to be fit to use, such materials need to satisfy a certain set of requirements: the material cannot be toxic, it must be biocompatible and, in the words of Dr Žarkovas, ideally capable of degradation inside the human or animal body, allowing new bone to grow in its place. According to the VU researcher, this process is highly complicated, for it is affected by a lot of factors such as the material’s rate of degradation.
"The process cannot be too quick or too slow. Besides, this world of calcium phosphates has a separate domain in which efforts are made to replace part of calcium ions with other biologically active ions. Some examples of biologically active ions are zinc or copper, which the body needs; besides, it can facilitate the growth of bones. At the same time, they offer a range of antibacterial properties, which is also important, because the bone implant is a foreign body and the system will want to be rid of it, often resulting in inflammation. It is this synthesis of calcium phosphates replaced by other ions that constitutes our field of research," the chemist says.
A quest to improve technologies used in medicine
According to the VU researcher, this technology already has application in medicine. A surgeon implants the site of the bone defect with the necessary materials that help the bones become stronger or regrow, such as certain pellets, ceramics, phosphate cement, or coatings on metal implants. However, Dr Žarkovas emphasises that as the science is in a constant state of development, the search continues.
"With testing materials in vivo, an artificial defect is made in the bone and is filled with the material and, roughly speaking, the cells need to “devour” the ceramic and turn it into new bone. The process is more or less as follows: you feed cells the same materials that the bone is made from. The requirements for the implants depend on the site of insertion and on the mechanical properties that site requires. For instance, if there is some kind of load, you cannot implant a soft body there, because it will just not work," Dr Žarkovas explains.
Lithuanian and Japanese scientists united in research
The research conducted by the VU’s chemists mainly deal with synthesising different materials, while there are also plans to work with Japanese researchers who are specialists in ceramics.
"The most popular and most-researched member of the calcium phosphate family is calcium hydroxyapatite, although we primarily work with vitlokite, the second most common biomineral. Vitlokite has not been studied as thoroughly and lacks thermal stability, breaking down at high temperatures that the process of making ceramics involves. It is this particular group of our colleagues from Japan that knows how to make a dense and hard formation at low temperatures," says the VU researcher, speaking about the collaboration.
It was his research on the subject of "Synthesis of Transition Metal Vitlokite" that netted Dr Žarkovas his young researcher scholarship from the Lithuanian Academy of Sciences. Right now, the main job for the VU’s chemists is to synthesise magnesium vitlokite -- the second most prevalent biomineral -- and to replace the magnesium in its makeup with other similarly sized ions: zinc, copper, or manganese.
"When it comes to working with the Japanese researchers, our long-term plan is to use the material to form ceramics, investigate its mechanical properties, and see if ceramics can have an advantage over the materials that are currently in use. Indeed, the road from synthesising the new material to conducting in vivo tests is not a short one, especially when you are unable to carry out the tests on animals yourself. Some materials are used in practical trials on humans, too, but introducing something new still requires testing it on animals, and those tests take a long time to complete," says the chemist.
Different research changing the established knowledge of materials
Work with calcium phosphates is not the only field the VU’s chemists are engaged in. Recently, the researchers have succeeded in synthesising certain materials that have a pyrochloric structure without exposing them to high temperatures and high pressure -- the necessary conditions under the available literature.
"As a chemist, I was impressed, because, as often as not, this requires high pressure and a flow of oxygen, which we did not use. It means that we have simplified the technological synthesis process, which is definitely a huge benefit, because manufacturing every product aims for the process to be as simple as possible, involve fewer steps and lower costs. We too are planning to expand our work and possibly extend this experience to similar materials and to see whether we are able to apply this expertise, limited as it is, in a similar area," says Dr Žarkovas, pleased with the achievements.
