Anna Kilian: A chemosensor detecting fungal infections was developed at the Institute of Physical Chemistry. What was the starting point of this endeavor?
Marcin Dąbrowski: A couple of years ago, I had a conversation with one of physicians from the Medical Institute in Warsaw about the topic of her doctoral dissertation. She drew my attention to fungal infections as a grave problem in the course of chemotherapy. I became deeply interested in this issue, and after studying medical literature provided by my colleague, I decided to work on selective recognizing of D-arabitol (a sugar alcohol produced in human intestinal flora by Candida species). I designed a chemosensor further developed by our team.
What came next?
M.D.: The first stage included providing funds for our project. A research application with a description of methodology had to be prepared. Then we had to wait for our application to be accepted, conducting preparatory research in the meantime.
How can fungal infections be detected?
M.D.: The concept of the project was to detect fungal infection marker – D-arabitol – in body fluids. While mammalian cells, including human, produce equal quantities of L-arabitol and D-arabitol, Candida species produce only the latter. Therefore, when D-arabitol begins to dominate over L-arabitol in human cells, this indicates a developing fungal infection.
Almost all of us are fungi carriers…
Włodzimierz Kutner: A whole zoo lives on our skin. Not only fungi, but also mites and Protozoa – various microorganisms, which coexist with us in symbiosis during our entire life, so scrubbing too hard in the shower is not going to do us any good. It only becomes troublesome when our immune system undergoes a sudden crisis. This might happen during chemotherapy or treatment preventing transplant rejection. In some cases, after a successful transplantation surgery the patient may be allowed to go home and still die as a result of a fungal infection that they got at the hospital. In hospitals we may find fungi so mutated that they become resistant to many drugs. Usually, a fungal infection is only detected at a stage when it is too late to cure the patient. Early symptoms are difficult to recognize and point towards other diseases. This is why it is vital to effectively diagnose fungal infections at an early stage. D-arabitol marker makes a perfect detector of fungal disease. Fungi are eukaryotic organisms, while bacteria are prokaryotic. Prokaryota are biochemically different from us, so it is easy to find substances harmful to bacteria, but not to our organism. Fungi, on the other hand, resemble our organism in certain aspects, making it difficult to fight fungi without affecting our health in a negative way. As a consequence, anti-fungal treatments have a long list of negative side effects. It is very risky to expose long-term patients to another invasive therapy when their organisms are already seriously weakened. For this reason, it is crucial not to start treatment unless the fungal infection is really serious, not to reduce anyone’s comfort in vain.
How does a chemosensor work?
M.D.: Each chemosensor consists of two basic elements – a recognition unit and a signal transducer. The first is used to selectively bind D-arabitol, and the latter translates chemical recognition signal into a physical quantity that we can easily measure.
W.K.: The signal of chemical recognition is not yet an analytical signal. If the recognition occurs in a living organism, no transducer is required, since the organism knows what substance it is dealing with. Yet in external measurements we must translate the act of recognition into a language of signals, such as electric signals. This is why we need a signal transducer.
M.D.: In our chemosensor, the recognition unit consists of polymer film with molecular cavities. Thanks to molecular imprinting technique, the polymer contains cavities suitable for reversible binding of D-arabitol.
Is there a prototype of the sensor?
W.K.: Thin layers of polimer, varying from 100 to 150 nanometers are applied on different types of conductors. We are now investigating methods of transducing the signal. One of the first methods that we tried was weighing. When molecules are added to the polymer, its mass changes within the range of nanometers. Obviously, an ordinary scale would not catch this change, so we used a piezoelectric microbalance. The polymer is deposited on the quartz resonator of the microbalance. Another method utilizes field-effect transistors with an external gate. The gate is covered with molecular imprinted polymer, and the sensor is part of MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor). Yet another way of transducing the signal is based on double electric layer volume change.
M.D.: We have not tried the volume change method in recognizing D-arabitol yet.
W.K.: There are many methods available for transducing signal in chemosensors. We only use half a dozen. Another one is the spectroscopy of surface plasmons. The unit contains a crystal plate covered with gold, upon which we deposit our polymer. Thus, there is no prototype as such yet.
Agnieszka Wojnarowicz: One of the chemosensors that we have developed is the detector of anti-cancer agents such as 6-tioguanine (a cytotoxic drug used in leukemia treatment). Detecting 6-tioguanine is very important, because this substance aggregates in the liver, becoming toxic. Therefore, it must be detected before it reaches high concentration. In this sensor, volume changes of double electric layers were used for transducing signal.
W.K.: For every new chemosensor, we use a function monomer and a networking monomer from our “monomer library” prepared by our partners from the University of Milan and the University of North Texas in Denton. For each task involving molecular recognition, a special monomer is chosen. We do not waste money on preliminary experimental tests, but first run a molecular modelling instead because monomers are expensive substances. Thus, the first stage involves computer calculations to check if the complex obtained will stand polymerization and if the molecular cavity will not collapse. Now for the biomarkers…
Krzysztof Noworyta: In a sense, biomarkers have already surfaced in our conversation since it is a very wide category. Biomarkers are now routinely detected. For example, sodium and potassium are biomarkers, too, and thei concentration indicates whether the organism is healthy or there is a disease developing. Body temperature is also a biomarker of a kind. What we are looking for in our research are chemical substances such as proteins which would enable us to detect the diseases of affluence. Diseases such as lung cancer, pneumonia, and kidney diseases show very limited or no symptoms until they are already advanced. Biomarkers vary from small molecules, like creatinine, to large ones such as albumin. Cancer markers are usually substances with large molecules; in such cases, molecular imprinting is very difficult. Large molecules may stuck in the polymer, which is why imprinting them requires creating a polymer of loose structure and enough space between chains to enable easy diffusion – penetration and extraction of molecules.
W.K.: I would like to refer here to something that has grew to be everyday practice in surgery nowadays – laser surgery. It is not only very precise, but it also coagulates protein in high temperature, resulting in bloodless cutting. Moreover, it is suitable for eye surgeries. But if a surgeon-ophthalmologist asked for such a tool before the laser was invented, would it appear instantly? No! It first took an idea of eccentric physicists, who came to build the first laser. In other words, the laser was employed, not generated by medicine. Results of fundamental research were applied in medical world. The same goes for our work – we do basic research in supramolecular chemistry, which investigates the effects of one molecule penetrating another. Our current research also stems from earlier works on conductive polymers, awarded the Nobel Prize in 2000. We have also conducted fundamental research on designating mass on subnanogramme level. It was only the combination of all those studies that led us to projects as the one we are discussing today. Let us now talk about the toxic contamination of food of animal origin. Maciej Cieplak: Detecting toxic substances in food is another sensor application finding its way to everyday life. Food is often falsified, there are many cases of meat producers “refreshing” their products.
W.K.: Years ago in China there was a criminal case which involved intentional contamination of milk and milk products with melamine. This white powder after polymerization is used, among others, to produce kitchen worktops. A Chinese producer added melamine to powder milk in order to make it seem richer in protein. After adding such powder milk to forage, pet owners in USA and Canada observed rapid deaths of their cats and dogs because of buying dog food and cat food containing melamine. In China, newborns were dying after consuming contaminated powder milk. We created a melamine sensor and checked chosen Polish dairy products – no melamine. There are also other products that may prove toxic to people. Fish, pork, beef and poultry may contain toxins if processed in excessively temperatures. Regular intake, even in small portions, may lead to various diseases, including cancer. Meat preservation techniques – drying, curing or smoking – may also result in producing toxins.
Hence the recent tightening of EU policy concerning authorizing trade of smoked products of animal origin…
W.K.: Indeed. In order to avoid generating such toxins in homemade grilled meat, it is enough to place tin-foil under meat. It prevents too much smoke from getting in the meat. Dr. Cieplak will discuss yet another of our new sensors…
M.C.: There is an authority responsible for detecting toxins in food, called Sanepid. It regularly controls food available in shops. Nevertheless, those tests are quite expensive and require having a well-equipped lab with trained staff. Instead, we are proposing a sensor that can potentially be miniaturized into a pocket-size device. It could be used by anyone, on a daily basis. All it would take is get a food sample and wait for the result confirming whether or not the food can be consumed safely. Thanks to our sensor, Sanepid could test meat products directly on the producer’s premises.
W.K.: Nobody would like to eat food being aware it is stuffed with growth hormones or antibiotics added to forage, or – in case of fruits and vegetables – contaminated with pesticides and herbicides. There is a definite period of time that must pass between applying chemical substances on plants and picking fruits so that no trace of toxins remains on the product. The same goes for products of animal origin – after feeding animals forage containing drugs, the producer must wait a certain period of time until the substance is metabolized. Often what happens is that test results confirming that the meat contain harmful substances arrive from the lab long after the food was sold, cooked and eaten. Therefore, our aim is to
… and even digested.
W.K.: Therefore, our aim is to make such sensors easily available to everyone.
So that everyone has a small lab at home with a couple of sensors?
W.K.: That’s right! So that you can go to the food market, place the sensor near the fish and immediately know whether it is fresh or not. You no longer have to take the vendor’s word for it. Let’s talk about the sensor detecting nitroso derivatives.
M.C.: Those substances appear in meat due to processing in high temperatures – frying and smoking. Such a sensor would enable a quick test at a restaurant before eating your meal. We could also check at home whether we prepared dinner in a healthy way. The same goes for smoked products.
The new EU regulations concerning smoked products were not well received in Poland…
M.C.: Which is strange given that smoking without proper control may generate carcinogenic nitrosamines.
W.K.: Meat producers obeying to formal procedures have nothing to fear. The others should be eliminated from the market for the sake of public health.
When will your sensors be available? So far they have not gone beyond research…
W.K.: It is not to us that this question should be asked.
Do you present your ideas directly to the industry branch?
W.K.: Fundamental research is usually concluded with a patent on the concept and production procedures and publication thereof. Between fundamental research and a market product, there is a huge distance that could be filled with hundreds or thousands of tests on detectability, repetitiveness and selectivity of our sensors. Implementation tests require much more money than we have at our disposal at the Institute. They also carry a great risk, since commercial success is not guaranteed at any stage. That is why the industry is cautious towards such endeavors. It takes venture capital and the courage to invest in start-up and spin-off companies. Then after 3-4 years the investor gets to know whether it ends up with a commercial product or a failure. In developed business environments, such as in Silicon Valley or in Sweden, for instance, the success rate oscillates around a dozen percent. But the lucky investors make a huge profit. In Poland, the venture capital has yet to be built.
K.N.: Such companies exist, but there is not many of them. In this case, the state should act as an intermediary. For example, with funds offered by the National Centre for Research and Development.
What happens if someone in another part of the world develops such sensors at the same time?
W.K.: The first thing we do is apply for a patent. All ideas we discussed today will be made public thanks to you. They had already been submitted to Polish Patent Office. You haven’t heard of anything, which has not yet been developed into a patent application. Such concepts we may discuss in our next interview.
Can you search for investors in other EU member states?
W.K.: The way it happens is institutionalized. After submitting a patent application, we provide a detailed description of the invention to be published. Interested parties may get hold of it by buying the patent or license along with the know-how. All of this is available here at the Institute.