Analytical chemistry is now developing mainly in two areas: automation and the creation of complexes that allow, on the one hand, for simultaneously analyzing a large number of samples without the participation of an operator, and on the other, the development of portable miniature devices for personalized medicine and the monitoring of a human habitat. The sensor devices, the great majority of which are biosensors and chemical sensors, perform the role of the latter. That last line is considered in the proposed review. Attention is paid to transducers, receptors, techniques of immobilization of the receptor layer on the transducer surface, processes of signal generation and detection, and methods for increasing sensitivity and accuracy. The features of sensors based on synthetic receptors and additional components (aptamers, molecular imprinted polymers, biomimetics) are discussed. Examples of bio- and chemical sensors’ application are given. Miniaturization paths, new power supply means, and wearable and printed sensors are described. Progress in this area opens a revolutionary era in the development of methods of on-site and in-situ monitoring, that is, paving the way from the “test-tube to the smartphone”.

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This paper reports a novel enzyme-free electrochemical immunoassay for Escherichia coli (ATCC 25922) that involves the formation of an immunocomplex between antibodies immobilized on the surface of a platinum electrode and bacteria-labelled magnetite nanoparticles. Magnetite nanoparticles modified with chitosan were used as the signal label in the immunoassay. The main novelty is the collection of an electrochemical signal from a magnetic nanolabel included within the immunocomplex on the electrode surface. The developed immunosensor is highly specific, enabling the determination of E. coli from 10 to 10 5 colony-forming units (CFU)/mL with the relative standard deviation below 10%. The limit of detection for the immunosensor was 9.3 CFU/mL. Bacteria were determined in model mixtures and real samples. The recovery was between 95 and 99%, comparable with results from enzyme-linked immunosorbent assays. Keywords