A novel flexible ion-selective sensor for potassium and sodium detection was proposed. Flexible ion-selective electrodes with pseudo-liquid internal solution on contrary to the system with a solid contact provided a more stable analytical signal. Such advantages were achieved because of polyelectrolyte (PEI/PSS) layers adsorption on the conduct substrate with a layer-by-layer technique. Such an approach demonstrated that ion-selective electrodes save sensitivity with Nernstian dependence: 56.2 ± 1.4 mV/dec aNa+ and 56.3 ± 1.9 mV/dec aK+, as well as a fast time of response for potassium (5 s) and sodium (8 s) was shown. The sensing platform proposed demonstrates a better time of response and is close to the Nernstian value of sensitivity with a sensor low cost. The results proposed confirm a pseudo-liquid junction for the ion-selective electrode. Biocompatibility of an ion-selective sensing platform was demonstrated at potassium potentiometric measurements in Escherichia coli biofilms. Potassium levels in a biofilm were measured with potentiometry and showed agreement with the previous results.

This work depicts an electrochemical hydrogel–eutectic gallium indium alloy interface for the detection of tick-borne encephalitis (TBE) virus. This interface allows recording of nonlinear current–voltage responses, depending on the composition of the hydrogel. The current–voltage data for the machine learning model are trained by a multilayer perceptron. This model accurately recognizes the TBE antibody, antigen, and an antibody–antigen complex in mixture with interfering bovine serum albumin with 93% accuracy. Thus, this interface can be used as a convenient method for expressed viruses and pathogens detection.

In this paper, we describe an electrochemical sensing platform—ElectroSens—for the detection of Zn based on self-assembled polyelectrolyte multilayers on the carbon fiber (CF) electrode surface. The CF-extended surface facilitates the usage of a small volume electrochemical cell (1 mL) without stirring. This approach allows making a low-cost three-electrode platform. Working electrode modification with layer-by-layer assembly of polyethyleneimine (PEI), poly(sodium 4-styrenesulfonate) (PSS), and mercury nitrate layers eliminates solution toxicity and provides stable stripping voltammetry measurements. The stable, robust, sustainable, and even reusable Ag/AgCl reference electrode consists of adsorbed 32 PEI-KCl/PSS-KCl bilayers on the CF/silver paste separated from the outer solution by a polyvinyl chloride membrane. The polyelectrolyte-based sensor interface prevents adsorption of protein molecules from biological liquids on the CF surface that leads to a sensitivity increase of up to 2.2 μA/M for Zn 2+ detection and provides a low limit of detection of 4.6 × 10 –8 M. The linear range for Zn detection is 1 × 10 –7 to 1 × 10 –5 M. A portable potentiostat connected via wireless to a smartphone with an android-based software is also provided. The ElectroSens demonstrates reproducibility and repeatability of data for the detection of Zn in blood and urine without the digestion step.