| Małgorzata Kłoskowicz |
There is probably no scientific centre in the world that does not deal with the topic of nanomaterials. Scientists synthesise them, study their properties, and finally check what impact they have on the environment and the organisms living in it. All because of their great application possibilities. Nanomaterials are widely used, among others: in the medical industry, technology and everyday objects, but also in agriculture, in the form of nano-pesticides. What is worrying, however, is that due to their size, they can penetrate biological barriers. What should we do with this knowledge? This question is answered by Sławomir Sułowicz, PhD from the Faculty of Natural Sciences of the University of Silesia in Katowice, who, together with his team, studies the impact of nanoparticles on one of the smallest organisms, i.e. bacteria.
According to scientists, microorganisms are great markers of changes in the environment. They react quickly to what is happening around them. They therefore allow us to better understand what impact, for example, too much nanomaterials may have.
“Nanoparticles are natural, they have been present in the environment for a long time. However, we, scientists, artificially synthesise them so that we can use them in various ways. It’s hardly surprising. They arouse great interest in the industry. They have great properties and improve the quality of many products we use every day. However, it is not a secret that anything in excess can be harmful, which is why research answering the question of how nanoparticles affect various types of organisms is also important”, explains Sławomir Sułowicz, PhD, who, together with his team, analyses how bacteria react to increasingly popular nanomaterials.
When asked why he chose bacteria, the scientist from the University of Silesia admits that they are an interesting subject of research.
“They react relatively quickly to what is happening in the environment. If any type of contamination appears in it, they immediately signal it, in their own way, of course. In this sense, bacteria are very good sensors of changes in the environment”, emphasises the researcher.
Such pollutants or stressors may be not only nanomaterials, but also heavy metals, pesticides and aromatic hydrocarbons. However, the reactions of microorganisms differ and we need to learn to recognise them. There is no single response to a stressor. Sławomir Sułowicz, PhD gives several examples. As a result of the presence of a substance, especially in excessive amounts, the population of microorganisms may decrease or, interestingly, increase. Their enzymatic activity may increase or decrease.
“Although it sounds paradoxical, not all substances which are toxic from our point of view have to be harmful to microorganisms. It happens that this type of pollution can be quite a good source of food, and therefore energy, for bacteria. Hence their greater activity and more intensive division”, explains the microbiologist.
It all depends on the composition of various compounds. For example, heavy metal nanoparticles cannot be broken down into simpler substances. Above a certain level, nanoparticles can cause various undesirable effects also on microorganisms. “Nanomaterials in the form of sharp particles have the ability to cut through the cell membrane. How does this affect the bacterium? These microorganisms do not die out of nowhere, there is no such instruction ‘imprinted’ in them. They can divide indefinitely. However, if their membrane is damaged, the inside leaks out. This process is called cell lysis. The problem is that each bacterium is a single-celled organism. Such an incident means its end”, says the researcher from the University of Silesia.
Moreover, when a nanoparticle enters the cell, it may contribute to the formation of reactive oxygen species, which in turn may lead to damage to enzymes and other components of the cell, and this, of course, also affects its functioning.
An interesting phenomenon, as the scientist explains, is also the binding of some nanoparticles, for example heavy metals, on the cell surface. This is possible thanks to its cover and the wall, which is quite thick. Certain types of pollutants then may be permanently bound, i.e. retained permanently on the cell surface.
Nanomaterials are structures that can consist of various components, where at least one dimension of one of them must be smaller than 100 nanometres. So, there are a lot of possible combinations. As the scientist says, one of the examples of such structures that interest him are nano-pesticides.
“We know that intentionally introducing hundreds of thousands of tons of pesticides into the environment annually will not benefit anyone in the long run. We are also aware that the inhabitants of our planet need to be fed, which is why producers must take care of crops. Nano-pesticides may be the solution to the problem, if only because, due to their very good properties and selectivity, they can be used in much smaller quantities and be equally or even more effective. But that’s not all. They can be designed to be effective only during a certain period of time when a given pest is present, or to bind, for example, on the leaf surface in such a way so as to not be washed away by rain. However, we come back to the same question: what happens when they enter the bodies of people or animals along with food, and how to avoid this?”, asks the scientist.
Research is ongoing, which is why nano-pesticides are still not widely used, and only a few have been approved for production.
“And this is where microorganisms appear again. We know that they will be the first to face this challenge in order to survive. Currently, the European Union requirements in the registration process of pesticides concern their ecotoxicity. This includes research on the impact of a given compound on microorganisms inhabiting, for example, the soil. The key question is what standards we should propose for nano-pesticides. New methods of testing ecotoxicity are also needed, and this is one of the questions we ask ourselves in our Nano-Microbiology Team”, says Sławomir Sułowicz, PhD.
The level of knowledge is still too low to allow for the introduction of this type of protective substances on a mass scale.
“We know that there will always be environmental risks, but our task is to design nanomaterials, and in this case nano-pesticides, that will be better in every respect than currently used pesticides. I believe this lies within our capabilities. We want to protect crops and protect ecosystems as much as possible. Therefore, we need to decide what negative effect we are willing to accept, knowing that the benefits will be many times higher. Such strategic discussions are currently taking place in many countries”, he adds.
Of course, scientists provide important arguments. For the purpose of analysing the impact of nano-pesticides on microorganisms, the team led by Sławomir Sułowicz, PhD synthesised compounds containing active organic substances bound to an inorganic nanocarrier. Microbiologists then checked how the selected nano-pesticides affected bacteria. On this basis, they will be able to recommend an environmental assessment research method based on the use of microorganisms as markers of environmental changes. The results of this type of research are invaluable because there are not many scientific works on this topic yet. “Let’s use modern methods and look for the best possible solutions using nanomaterials, because they have huge potential. We just need time to learn more about them and then be able to make more informed decisions”, concludes the researcher.
Apart from Sławomir Sułowicz, PhD, the Nano-Microbiology Team consists of Anna Markowicz, PhD and Sławomir Borymski, PhD. The project examining the impact of nano-pesticides on microorganisms also involved: Anna Nowak, PhD from the Faculty of Natural Sciences of the University of Silesia and Mateusz Dulski, PhD, DSc, Assoc. Prof., from the Faculty of Science and Technology of the University of Silesia.
Article ‘Should we give up nanomaterials?’ was published in the May issue of University of Silesia Magazine No. 8 (318).
The Nano-Microbiologists Team includes (from the left): Sławomir Sułowicz, PhD, Anna Markowicz, PhD and Sławomir Borymski, PhD from the Faculty of Natural Sciences, University of Silesia | Photo by Małgorzata Dymowska