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We first report on constant potential (dc) amperometric flow-injection analysis (FIA) transduced by electroactive (conductive) polymers. Amperometric response is caused by the polymer recharging in order to maintain the electrode potential at a constant level when (i) ions are crossing the film|solution interface and polarizing electrode| film interface or (ii) ions or neutral molecules are specifically interacting with the polymer recharging it. The response under constant solution flow is a current peak and in flowinjection mode is a couple of current peaks directed opposite of the first sharp, analytically valuable peak. In both constant flow and flow-injection regimes, the peak current is dependent on analyte concentrations; obviously, the FIA mode provides more advantageous analytical characteristics. Constant potential amperometric flow-injection analysis is shown for boronateand sulfate-functionalized polyanilines as well as for Prussian Blue, a member of the inorganic polymer family. As a proof of concept, the successful dc amperometric detection of lactate in human sweat with boronate-functionalized polyaniline has been shown. The proposed approach would revolutionize the field of conductive/electroactive polymer-supported ion sensing with the introduction of reliable and robust amperometry as a valuable alternative to existing potentiometry.

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In December 2019 humanity faced a new coronavirus infection caused by SARS-CoV-2 virus and the disease referred to as COVID-19 has spread globally.Specially adapted for the detection of SARS-CoV-2 RNA tests based on polymerase chain reaction are used to identify infected patients by processing nasal and oropharyngeal swabs. However, often it may not be sufficient to use polymerase chain reaction only, but in many cases it is very important to assess the humoral and cellular immune reactions to the infection.The present review aims to summarize and analyze the available literature data on the formation of the immune response and diagnostic methods used for characteristics of the immune reactions in patients who recovered from COVID-19 or received an anti-COVID-19 vaccine.Currently, the effectiveness of anti-COVID-19 vaccination and the developing immunity after a previous illness are assessed by detecting specific antibodies. A number of observations show that anti-S and anti-RDB IgG titers significantly decline within 6–8 months after diagnosis. It is important to note that although the antibody levels in the blood of recovered patients decrease, the memory cells can be determined by the appropriate tests.The ELISPOT (Enzyme-linked immunospot) method, which is a variation of the ELISA (Enzyme-linked immunosorbent assay), allows estimation the T- and B-cells that release activation factors such as cytokines and antibodies in response to the presented antigens.The assessment of the generation and effective function of the immune memory to SARS-CoV-2 requires the evaluation of the content and functional activity of its various components, including B-lymphocytes, CD8+, CD4+T-lymphocytes, since they have rather independent mechanisms of action of cellular memory.Therefore, it is crucially important to have tools for evaluating the immunity to SARS-CoV-2 when the level of antibodies is insufficient for determination by the available registered tests, and the introduction of test systems into clinical diagnostic practice, allowing to identify markers of long-term cellular memory, are relevant.