Ural Federal University: Chemists Created a Sensor that Accurately Detects the Saliva pH Level

Chemists at UrFU have created a sensor for determining the pH of human saliva. This is a fluorophore with strong and stable emission, which picks up the smallest fluctuations in the pH in biological fluids (tenths). The analysis is performed using microdoses of the substance and a spectrometer, in which the substance is irradiated with a special lamp (its lifetime is tens of thousands of hours). The pH data appears in 5-7 seconds. The first results of joint studies of saliva samples and the sensor, conducted by scientific groups of the Department of Organic and Biomolecular Chemistry and the Department of Analytical Chemistry of the Institute of Chemical Engineering, are described in the famous Dyes and Pigments journal.

“Modern fluorometric pH sensors are based on small organic molecules. Typically, they are very sensitive and are able to detect the desired analyte in very low concentrations, up to nanoconcentrations. Our sensor is based on a new compound. We introduced a fluorinated fragment, and this allowed us to get the photophysical and electrochemical properties we needed,” explains Timofey Moseev, an engineer-researcher at the Department of Organic and Biomolecular Chemistry at UrFU.

Saliva pH analysis is an accessible and non-invasive method of clinical diagnosis. With its help at an early stage you can detect diseases, in particular gastrointestinal diseases: gastritis, stomach ulcers, duodenitis, etc. The pH level also affects the teeth: even a slight increase in the acidity of saliva can cause tooth decay and other problems.

The new compound is the result of many years of collaborative work by the teams of the departments of organic and biomolecular chemistry and analytical chemistry at the Institute of Chemical Engineering. According to Mikhail Varaksin, director of the Institute of Chemical Engineering at Ural Federal University, Moseev has been working on the research work on this topic since his second year of bachelor’s studies in 2015, becoming a member of the research team.

The sensor is reusable, non-toxic, and environmentally friendly. Chemists used an atom-economical method of synthesis to create it: no catalysts (nickel, copper, palladium) or additional reagents were needed. In addition, the sensor is water-soluble.

“In the classical method of synthesis, two molecules require active fragments that interact with each other, and thus a new compound is obtained. But the principles of “green chemistry” require that the reactions take place without by-products, in non-toxic solvents (water), and with minimal use of active fragments. If these active fragments are removed, the simplest carbon-hydrogen bond in organic chemistry is left. The reaction takes place between the two. In this way an atomic economy is obtained. Since the reaction takes place between C-H/C-H, the byproducts are more likely to be water or a similar compound. The synthesis results in fewer by-products and noxious products,” Timofey Moseyev explains the essence of the process.

The new chemosensors obtained by Ural chemists can be used to analyze water (acidity, presence of metals or toxins) and as fluorescent probes to illuminate intracellular processes. The compound accumulates in a specific location of the cell and stains a specific part of the cell. However, this line of application has yet to be explored.

In general, in addition to biomedical applications, the organic fluorophores obtained by UrFU chemists are promising materials for other fields as well due to the wide possibilities of their practical application. In particular, fluorophores are used in molecular electronics. The “heart” (working elements) of solar cells are similar organic molecules. Another example is OLED screens of computers and monitors. They are also based on an organic molecule with certain photophysical properties.