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COMMON PART

Project Number24-23-00215

Project titleIon-selective coulometry with a generation of a sequence of secondary signals: a mean to enhance the sensitivity, accuracy and robustness of body fluid analysis with ion-selective electrodes

Project LeadMikhelson Konstantin

AffiliationFederal State Budgetary Educational Institution of Higher Education "Saint-Petersburg State University",

Research area 03 - CHEMISTRY AND MATERIAL SCIENCES, 03-402 - Electrochemistry and corrosion of metals

KeywordsIon-selective electrodes, ionophores, chronoamperometry, coulometry, secondary signals, saliva, blood serum, calcium, potassium, sodium, lithium ions.

PROJECT CONTENT

Annotation
As a part of the transition to personalized medicine, high-tech health care, and illness and disease prevention technologies, the development of methods for highly sensitive quantitative determination of the electrolyte composition of body fluids (blood, serum, urine, saliva, sweat, tears) is an important task. Such methods and devices are necessary for carrying out preventive examinations, diagnosing diseases, and monitoring the condition of patients during their treatment. The content of sodium, potassium and calcium in blood is important in view of cardiovascular diseases, knowledge of lithium concentration is necessary for the diagnostics of the oxidation stress, leaving alone the control of lithium during therapy of psychic diseases. Analysis of the electrolytes in saliva is noninvasive and therefore is advantageous in comparison of blood analysis. Currently, in examination of the ionic composition of body fluids they use ion-selective electrodes (ISEs) with polymeric plasticized membranes based on ionophores. Measurements with ISEs are made in potentiometric mode. This approach has been used for decades but it has a significant drawback: an insufficient sensitivity of ca. 2-4% relative change of the concentration of monovalent ions and 4-8% for divalent. Such a sensitivity is often not enough for the analysis of body fluids due to narrow range of the changes of their compositions. The recently proposed method of ion-selective constant potential coulometry allows improving the sensitivity of the analysis with ISEs to less than one percent. The method is as follows: the ISE potential is maintained constant by a potentiostat while the potential at the interface between the electrode and the sample varies along with the sample composition conforming the Nernst law. When the sample composition changes, a current start flowing across the ISE, and the peak value of the current refers to the moment of the sample composition change, with consequent gradual decrease of the current to zero. Integration of the chronoamperometric response over time allows obtaining a cumulated charge used as an analytical signal. The topicality of the project lies in the fact that the ion-selective constant potential coulometry allows increasing the sensitivity of the analysis with ISEs from a few of a percent to less than one percent relative change of the analyte concentration. The scientific novelty of the project refers to an additional advantage of the ion-selective constant potential coulometry revealed, for the first time, in the applicants’ scientific group. It is shown a possibility of generating a sequence of signals (instead of a single signal) from the same sample. Preliminary data show that in this way, by averaging current and cumulated charge obtained in the “primary” (in response to the change of the sample composition) and several “secondary” responses one can achieve an additional increase of the accuracy and robustness of the measurements. Due to the social importance of medical and biological tasks, the project is aimed at the increasing the sensitivity of analysis of body fluids (saliva, blood serum). Electrodes selective to calcium will be used in the beginning of the study, and later also potassium, sodium, and lithium ion sensors will be used in the research.

Expected results
In the course of the project a method will be developed of generation a sequence of chronoamperometric and coulometric signals obtained from ion-selective electrodes (instead of one signal) in the same sample. As a tangible result, it will be developed a platform of ion-selective electrodes capable of registration small changes of ion concentrations in body fluids, with enhanced accuracy and robustness. Initially, studies will be focused on a high-sensitive assay of ionized calcium in saliva which is important for the diagnostics and therapy of such states as hyper- and hypoparathyroidism, dry mouth syndrome, hyper- and hypocalcemia. Further in the course of the project, the developed technique of generating a sequence of signals from ISEs will be applied for a sensitive, accurate and robust quantification of potassium, sodium and lithium in saliva and blood serum. Later on, the knowledge obtained in the course of the project, the developed approaches and techniques can be further extended on the analysis of other biological fluids (urine, sweat, tears). The developed measurement techniques and data processing can be further used with toxic metal sensors and sensors of pharmaceutically relevant ions.

REPORTS