I.A. Borodina - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: borodinaia@yandex.ru B.D. Zaitsev - Dr. Sc. (Phys.-Math.), Professor, Head of Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: zai-boris@yandex.ru A.A. Teplykh - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: teplykhaa@mail.ru O.I. Guliu - Dr. Sc. (Biol.), Associate Professor, Leading Research Scientist, Institute of Biochemistry and Physiology of Plants and Microorganisms RAS (Saratov). E-mail: guliy_olga@mail.ru A.M. Shikhabudinov - Ph. D. (Phys.-Math.), Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: alex-sheih@yandex.ru I.E. Kuznetsova - Dr. Sc. (Phys.-Math.), Associate Professor, Leading Research Scientist, Laboratory of Electronic Processes in Semiconductor Devices, Kotel\'nikov IRE of RAS (Moscow). E-mail: kuziren@yandex.ru

At present there exists a need for electronic devices for carrying out the multiparameter express analysis of biological liquids of small volume, solving the problem of detection of bacterial cells and registering their interaction with bacteriophages, mini-antibodies, and antibodies. Today a fair amount of acoustical sensors based on various types of acoustic waves are widely used in biology. Among them the sensors using lateral electric field excited piezoelectric resonators, which allow to perform the express analysis of cells directly in liquid phase without any active layers, are most popular. However it is well known that acoustic waves in thin piezoelectric plates as compared with wavelength have the higher electrome-chanical coupling coefficient [8] and gravimetric sensitivity [9] in comparison with surface acoustic waves. This leads to the stronger influence of contacting liquid on wave parameters and more their sensitivity to the change of liquid parameters [10]. This data opens the possibility of the development of biological sensors for detection of bacterial cells directly in liquid phase by using acoustic waves in thin piezoelectric plates. The present paper is devoted to the description of the biological sensor which represents two-channel delay line based on the plate of Y-X lithium niobate with thickness of 0.2 mm. One channel of delay line was electrically shorted by thin film of aluminum deposited on the space between IDTs. The second channel was electrically open. With the help of the special glue the liquid container was glued on plate surface between transducers without appreciable increasing insertion loss of delay line. By using the developed acoustical biological sensor we experimentally investigated the specific interactions «bacterial cells - bacteri-ophages», «bacterial cells - antibodies», and «bacterial cells - mini-antibodies» directly in liquid phase. The input and output of the sensor were connected with 4 ports of the meter of S parameters (E5071C, Agilent) in the regime of measuring the phase and insertion loss of parameters S12 and S34 in time. The dependencies of the change in phase and insertion loss on concentration of bacteriophages, antibodies, and mini- antibodies were obtained for both channels of delay line. It has been found that aforementioned changes have the most values for electrically open chan-nel. This result has demonstrated that specific interactions of bacterial cells under study with bacteriophages, antibodies, and mini-antibodies lead to the increase of the electrical conductivity of cell suspension. The physical explanation of the obtained results is given. The obtained results allow to choose the optimal values of the concentration of bacteriophages, antibodies, and mini- antibodies for analysis of cell suspension. These concentrations are equal 5−10 phages per cell (for bacteriophages), 1−3 μg/ml (for antibodies), and 2−4 μl/ml (for mini- antibodies). Besides we have carried out the experiments with nonspecific interaction of cells in suspension with bacteriophages, mini-antibodies, and antibodies with the help of developed sensor. It was found that in these cases the changes in insertion loss and phase of output signal did not occur. So the described approach allows not only estimating the cells concentration but defining their type.

 

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