The discovery of bacteriophages allowed the development of new ways to control the bacterial number and to assess bacterial viability. The most obvious application of bacteriophages is the treatment of human bacterial infections (phage therapy). The advantage of phage therapy is the extreme specificity of phages, since they interact with and infect only certain bacteria without affecting other bacteria or cell lines of other organisms. The advances in phage biology led to the widespread use of specific phage–host interactions in medicine and the agricultural and food industries. Thus, bacteriophages are an alternative to antibiotics for fighting infections and destroying pathogenic bacteria. This work has demonstrated for the first time the potential of a compact acoustic sensor system for assessing the impact of bacteriophages on microbial cells and the bacteriophage sensitivity of the latter. It has been shown that the developed system can be used to evaluate the activity of bacteriophages against microbial cells within 5 min without taking into account the time of cultivation of microbial cells for analysis. The results obtained are promising for further development of the acoustic sensory system in phage therapy.

Outbreaks of viral infectious diseases in humans and animals remain one of the global problems of our time. Therefore, one of the most popular areas in applied microbiology is the development of fast and sensitive methods for determining viruses, including those based on biosensor analysis methods. The promise of acoustic sensor systems for detecting viruses is described in this work. The optimal capabilities of electroacoustic sensors in detecting viruses, the possibility of conducting analysis in the presence of interfering factors (viral particles and microflora), and the repeated use of sensors are shown. The promise of using acoustic sensors to determine viruses in microbiology, medicine, and veterinary medicine is demonstrated.

An acoustic delay line consisting of two Y–X-cut lithium niobate plates 0.2 mm thick placed on top of each other was experimentally investigated. An interdigital transducer is located at the edge of each plate. An rf voltage (pulsed or continuous-wave) is fed to one transducer, which excites a piezoelectrically active acoustic wave with transverse–horizontal polarization propagating in the first plate. The electric field of this wave penetrates the second plate to excite an acoustic wave therein, which is converted into an electrical signal using the second interdigital transducer. The phase and delay time of the output signal can be changed by varying the distance between the transducers by shifting one plate relative to the other.

The possibility of express analysis of the effect of aminoglycoside antibiotics on bacteria ( Escherichia coli ) using a sensor system based on a piezoelectric resonator with a lateral electric field with an operating frequency range of 6–7 MHz is shown. E.coli strains, both sensitive and resistant to kanamycin were used for the experiments. During evaluating the kanamycin effect on bacteria, the change in the electrical impedance modulus of the resonator was used as an analitical signal. It has been established that the criterion for the antibiotic bacteria sensitivity is the change in the modulus of the sensor electrical impedance after antibiotic exposure on bacteria at any frequency near the resonance. The sensor is highly sensitive and allows diagnosing the antimicrobial susceptibility of bacteria within 7–9 minutes.

Theoretical and experimental features of using an acoustic interferometer for determining the velocity and attenuation of an acoustic wave in liquids with different acoustic impedances are studied. It is shown for the first time that the indicated impedance determines the ratio of the resonance values of the maximum and minimum transmission coefficient S 12 for the same transmitter–receiver pair on the dependence of the transmission coefficient on the distance between the transducers. A methodology has been developed for determining the wave attenuation of a liquid free from the influence of “apparent” attenuation associated with the loss of part of the acoustic power to the transducers.

The acoustic properties of suspensions based on pure glycerol and diamond powder with a particle size of 1–2 μm and different concentrations were studied using a resonator with a longitudinal electric field. A disk resonator made of langasite with round electrodes on both sides of the plate with a frequency of 4.1 MHz, operating on a longitudinal acoustic wave, was completely immersed in a liquid container with the studied suspension. Based on the measured frequency dependences of the real and imaginary parts of the electric impedance of the resonator using an equivalent electromechanical circuit, the longitudinal elastic modulus and longitudinal viscosity coefficient of the samples were determined. Comparison of the experimental dependences of the longitudinal elastic modulus, viscosity coefficient, and longitudinal acoustic wave velocity on the volume concentration of diamond particles in the suspension with the calculated dependences demonstrated good agreement.

Use of large numbers of antibacterial drugs leads to increased pollution of the environment, especially water resources. Therefore, it is important to devise methods for the rapid detection and determination of antibiotics in aqueous solutions. We describe a microbial sensor system that is based on a resonator with a lateral electric field and is intended for the rapid detection and determination of kanamycin in aqueous solutions. Kanamycin was selectively determined in a solution with a conductivity of 1300 μS/cm. The lower detection limit was 0.5 μg/mL, and the analysis time was less than 5 min. The change in the electric impedance modulus of the sensor after kanamycin action on the bacteria served as an analytical signal. This sensor system is promising, because it can be used repeatedly and does not require immobilization of the analysis components on the sensor surface.

The parameters of a resonator with a lateral electric field with a thin film of chitosan acetate and chitosan glycolate in an air–ammonia mixture have been studied. It is shown that when the ammonia concentration increases, the maximum value of the real part of the impedance and resonance frequency of the resonance peaks decrease significantly and recover in air. It is established that these effects are associated with an increase in the surface conductivity of the films in the presence of ammonia. In this case, the response and relaxation times for these chitosan films differ significantly.

— The possibility of excitation and recording of longitudinal and transverse acoustic waves in an alumoittrium garnet crystal in the frequency range of 12–18 GHz using thin-film converters made of aluminum nitride and zinc oxide at room temperature was shown. As an electrodynamic system, single-stage quarter-wave and two-stage Chebyshev coaxial type aligners were used. It was found that the conversion coefficient at excitation of longitudinal and transverse waves is ~23 and 30 dB. The specific attenuation of longitudinal (22.2 dB/µs) and transverse (15.6 dB/µs) waves was estimated. It was shown that single-stage quarter-wave and two-stage Chebyshev aligners provided a bandwidth of 11 and 20%, respectively.

The results of a study of the influence of the electrical conductivity of a thin film deposited on the free end of a radial electric field excited acoustic resonator field or located in its immediate vicinity on the resonator characteristics are presented. Three situations were considered: there is no conductive film, the film is deposited directly on the resonator free end, and the film is located at a short distance from the resonator free end. In all three cases, the electrical impedance of the resonator was calculated and measured in a wide frequency range of 1–1500 kHz. For the first time, the material constants of piezoceramics were refined for a free and short-circuited resonator and it was shown that these constants coincide with each other with good accuracy. It is shown that a decrease in the resonator thickness and an increase in the gap between the electrodes increase its sensitivity to the presence of a conductive film at a short distance from the resonator end.

A biological sensor for the determination of ampicillin in conductive solutions is presented. The sensor is based on an acoustic slot mode in a structure consisting of two lithium niobate piezoplates of different cuts separated by an air gap. One of the piezoplates serves as the bottom of a liquid container into which a suspension of microbial cells sensitive to the antibiotic under study is introduced. The depth of resonant peaks in the frequency response of the total loss of the sensor is measured. After that, the studied antibiotic is added to the container and the measurements are repeated. An analytical signal indicating the appearance of an antibiotic in the cell suspension is the change in the depth of resonance peaks after it is added to the container.

A compact hardware-software complex for measuring the electrical and mechanical parameters of a liquid based on a piezoelectric resonator with a lateral exciting electric field has been developed. It is shown that the modulus of the electrical impedance of the resonator near the resonant frequency decreases monotonically with an increase in conductivity of the contacting liquid. The obtained dependences can be used as calibration curves for measuring conductivity in the range of 100-10,000 mu S/cm. A method for the simultaneous determination of the modulus of elasticity, viscosity, and permittivity of a liquid using the electromechanical equivalent scheme was developed and tested on a mixture "water - glycerol" with the different glycerol content.

A new type of piezoceramic acoustic disk resonator with a radial exciting electric field is described. The resonator is a disk made from 6mm crystallographic material using two round concentric metal electrodes with a gap between them placed on one side of the disk. Models of a free resonator and a resonator loaded with a film of finite thickness are presented. The characteristics of different acoustic modes for resonators made of BPZT-3 piezoelectric ceramic are calculated for different widths of electrodes and the gaps between them.

A microbial test-system for real-time determination of low/residual concentrations of kanamycin in a liquid without the need for special labels is presented. The main element of the system was a piezoelectric resonator excited by a lateral electric field based on an X-cut lithium niobate plate 0.5 mm thick with two rectangular electrodes on one side. On the other side of the resonator, there was a 1.5 ml liquid container. As a sensory element we used Escherichia coli B-878 microbial cells, which are sensitive to kanamycin. For measurement 1 ml of this cells suspension was placed in a liquid container and then the test liquid in the amount of 2 μl containing kanamycin was added. The change in the real part of the electrical impedance of the resonator before and after the test liquid addition was used as an analytical signal which indicated the presence of kanamycin. The lower limit of determination of kanamycin turned out to be 1.0 μg/ml with an analysis time of 10 min. The test-system allows to detect kanamycin in the presence of such antibiotic as ampicillin and polymixin.

A sensor is designed on the basis of a PZT resonator with a lateral electric field for the express analysis of microbial cells. The possibility of detecting and identifying microbial cells by recording their specific interaction with phage mini-antibodies directly in suspension is shown. The period of analysis does not exceed 5 min.

Antibiotics are widely used in medicine, veterinary medicine, and the food industry. However, the active use of antibacterial drugs leads to environmental pollution. In this regard, there is a great need for monitoring and determining antibiotics in various environments such as drinking water, food, drinks, waste water from pharmaceutical factories, etc. A number of methods, including those based on biosensors, have been developed to determine antibiotics. Biosensor methods of analysis are widely used and are an integral part of environmental monitoring. Electrochemical, optical, acoustic, microbial biosensors, immuno- and aptasensors, as well as sensors based on molecularly imprinted polymers are in the most demand for the analysis of antibiotics. This article provides a brief overview of biosensor methods and approaches for the determination of antibiotics. The most promising biosensor systems for determining antibacterial drugs were analyzed.

Антибиотики широко применяются в медицине, ветеринарии и пищевой промышленности. Однако активное использование антибактериальных препаратов приводит к загрязнению окружающей среды. В связи с этим существует большая потребность в мониторинге и определении антибиотиков в различных средах, таких как питьевая вода, продукты питания, напитки, сточные воды фармацевтических предприятий и др. Для определения антибиотиков разработано достаточное количество методов, в том числе и на основе биосенсоров. Биосенсорые методы анализа имеют довольно широкое применение и являются неотъемлемой частью при экологическом мониторинге. Наиболее востребованными для анализа антибиотиков являюся электрохимические, оптические, акустические, микробные биосенсоры, иммуно- и аптасенсоры, а также сенсоры на основе молекулярно-импринтированных полимеров. В статье приводится краткий обзор биосенсорных методов и подходов для определения антибиотиков. Проведен анализ наиболее перспективных биосенсорных систем при определении антибактериальных препаратов.

A theoretical and numerical study is performed of the effect of the thickness and the coefficients of the elasticity, viscosity, and electrical conductivity of a film deposited on a free side of a piezoelectric resonator with a lateral electric field on its characteristics. It is shown that an increase in the mechanical impedance of the film and its conductivity lower the maximum value of the real part of the resonator’s electrical impedance.

The study shows the possibility of rapid analysis of bacterial sensitivity to beta-lactam antibiotics on the example of ampi-clllln by using a piezoelectric resonator with a lateral electric field. It is established that the indicator of the sensitivity of microbial cells to the antibiotic and the criterion of its impact is the difference between the recorded sensor signal for cell suspension without the antibiotic and the sensor signal after the exposure to an antibiotic. The data obtained using the sensor confirmed the standard microbiological method for determining the sensitivity of microbial cells to ampicillin. The analysis of microbial cell sensitivity/resistance to ampicillin was carried out directly in the liquid phase without immobilizing the antibiotic on the surface of the piezoelectric. The advantages of this approach are high sensitivity of the method, measurement accuracy (within ± 2%) and short analysis time (within 10 minutes). The results show the benefits of using a piezoelectric resonator with a transverse electric field for analyzing the sensitivity/resistance of microbial cells to ampi-cillin.