Bacterial biofilm prevention and eradication are common treatment problems, hence there is a need for advanced and precise experimental methods for its monitoring. Bacterial resistance to antibiotics has resulted in an interest in using a natural bacterial enemy—bacteriophages. In this study, we present the application of quartz tuning forks (QTF) as impedance sensors to determine in real-time the direct changes in Pseudomonas aeruginosa PAO1 biofilm growth dynamics during Pseudomonas phage LUZ 19 treatment at different multiplicities of infection (MOI). The impedance of the electric equivalent circuit (EEC) allowed us to measure the series resistance (Rs) corresponding to the growth-medium resistance (planktonic culture changes) and the conductance (G) corresponding to the level of QTF sensor surface coverage by bacterial cells and the extracellular polymer structure (EPS) matrix. It was shown that phage impacts on sessile cells (G dynamics) was very similar in the 10-day biofilm development regardless of applied MOI (0.1, 1 or 10). The application of phages at an early stage (at the sixth h) and on three-day biofilm caused a significant slowdown in biofilm dynamics, whereas the two-day biofilm turned out to be insensitive to phage infection. We observed an inhibitory effect of phage infection on the planktonic culture (Rs dynamics) regardless of the MOI applied and the time point of infection. Moreover, the Rs parameter made it possible to detect PAO1 population regrowth at the latest time points of incubation. The number of phage-insensitive forms reached the level of untreated culture at around the sixth day of infection. We conclude that the proposed impedance spectroscopy technique can be used to measure the physiological changes in the biofilm matrix composition, as well as the condition of planktonic cultures in order to evaluate the activity of anti-biofilm compounds.

Miniaturized and integrated analytical devices, including chemical sensors, are at the forefront of modern analytical chemistry. The construction of novel analytical tools takes advantage of contemporary micro- and nanotechnologies, as well as materials science and technology. Two electrochemical techniques were used in experiments: electrochemical impedance spectroscopy and cyclic voltammetry. The goal of this study was to investigate electron transfer resistance in a model solution containing Fe 2 + / 3 + ions and protein adsorption using integrated electrochemical cells with different geometry. Tests performed at various Fe 2 + / 3 + concentration allowed to verify that these cells work properly. The influence of bovine serum albumin adsorbing to the surface of the integrated electrochemical cells was investigated. In electrochemical impedance spectroscopy, the value of R c t increased with protein adsorption and the relative change of R c t was in range 21% to 55%. In cyclic voltammetry the decreasing amperometric response of the working electrode was used as evidence of protein adsorption on the electrode.

The paper presents the specification of the CogMap Analyst program, which has been created for the purpose of conducting an analysis of the structure and content of sketch drawings of cognitive maps of urbanized spaces. Assumptions for this analytic tool come from the neobehavioral understanding of the concept of cognitive maps, which has its source in the works of Tolman, and from the criteria of analyzing their contents and structure, which were developed by Lynch (1960). The program serves the purpose of collecting numerical data on the quantity, size, as well as placement and distortion of objects on drawings by participants in relation to the actual layout of the terrain, which was selected by the researcher, and to the sketch’s scale. This data may be used not only to determine the measurements on drawings, but also to determine possible connections with other variables, such as personal traits of participants and formal traits of the space, according to the research goals of particular scientific studies for which the CogMap Analyst program shall be used. In this article we present the theoretical basis for the tool that we have created, we compare its characteristics with other similar methods of quantitative analysis of sketch drawings of cognitive maps, and we present in detail the mode of operation and of data analysis employed by CogMap Analyst.

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