Viral infections are common causes of diseases in animals and appropriate methods are increasingly being required to detect viral pathogens in animals. In this regard, similar to antigen- -antibody interactions, aptamers have high affinity and specificity for their respective target molecules, and can be selected using the Systematic Evolution of Ligands by EXponential enrichment (SELEX) technique. Recently, significant progress has been made in the development of aptamer selection and aptamer-based sensors for viral detection, and here we review some of the recent advances in aptamer-based detection of viral infections in animals. This review will serve as a comprehensive resource for aptamer-based strategies in viral diagnostics.

Biochemical Oxygen Demand (BOD) is an important factor used to measure water pollution. This article reviews recent developments of microbial biosensors with respect to their applications for low BOD estimation. Four main methods to measure BOD using a biosensor are described: microbial fuel cells, optical methods, oxygen electrode based methods and mediator-based methods. Each of them is based on different principles, thus a different approach is required to improve the limit of detection. A proper choice of microorganisms used in the biosensor construction and/or sample pre-treatment processes is also essential to improve the BOD lower detection limit.

Titania nanotube (TNT) arrays fabricated by anodizing of titanium foil in organic (ethylene glycol) and inorganic (phosphoric acid) electrolytes and thermally modified in argon revealed much improved properties to detect hydrogen peroxide. Horseradish peroxidase and acetate thionine co-absorbed by a dip coating on the TNT electrode were used to detect hydrogen peroxide in phosphate buffered saline. The morphology and electrochemical properties of TNT arrays were studied by scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Well defined oxidation and reduction peaks for potassium ferricyanide have been observed for TNT formed in ethylene glycol and annealed in argon. TNT arrays formed in organic electrolyte and annealed in argon indicated more favorable adsorption and electrochemical properties what was confirmed by detection of hydrogen peroxide towards analyte in phosphorate buffered saline solution.

In environmental matrices there are mixtures of parent drug and its metabolites. The majority of research is focused on the biological activity and toxic effect of diclofenac (DCF), there is little research on the biological activity of DCF metabolites and their mixtures. The study focused on the assessment of the biological impact of DCF, its metabolites 4’-hydroxydiclofenac (4’-OHDCF) and 5-hydroxydiclofenac (5-OHDCF) and their mixtures on E. coli strains. The biological effects of tested chemicals were evaluated using the following: E. coli K-12 cells viability assay, the inhibition of bacteria culture growth, ROS (reactive oxygene species) generation and glutathione (GSH) content estimation. Moreover, we examined the influence of the mixture of DCF with caffeic acid (CA) on E. coli cells viability. Our results showed the strongest impact of the mixtures of DCF with 4’-OHDCF and 5-OHDCF on E. coli SM biosensor strains in comparison to parent chemicals. Similar results were obtained in viability test, where we noticed the highest reduction in E. coli cell viability after bacteria incubation with the mixtures of DCF with 4’-OHDCF and 5-OHDCF. Similarly, these mixtures strongly inhibited the growth of E. coli culture. We also found synergistic effect of caffeic acid in combination with DCF on E. coli cells viability. After bacteria treatment with the mixture of DCF and its metabolites we also noted the strongest amount of ROS generation and GSH depletion in E. coli culture. It suggests that oxidative stress is the most important mechanism underlying the activity of DCF and its metabolites.

A highly sensitive photonic crystal fiber based on the surface plasmon resonance (PCF-SPR) biosensor for the detection of the density alteration in non-physiological cells (DANCE) is described. Human acute leukemia cells are determined by the discontinuous sucrose gradient centrifugation (DSGC) in which the cells are separated into several bands. The separated cells with different intracellular densities and refractive indexes (RI) ranging from 1.3342 to 1.3344 are distinguished in situ by means of the differential transmission spectrum. The biosensor shows a maximum amplitude sensitivity of 2000 nm/RIU and resolution as high as 5 × 10⁻⁵ RIU. According to the wavelength interrogation method, a maximum spectral sensitivity of 9000 nm/RIU in the sensing range between 1.33 and 1.53 is achieved, corresponding to a resolution as high as 1.11 × 10⁻⁵ RIU for the biosensor. The proposed PCF-SPR biosensor has promising application in biological and biochemical detection.

An useful electrochemical sensing approach was developed for norepinephrine (NE) detection based on semiconducting polymer (9-nonyl-2,7-di(selenophen-2-yl)- 9H-carbazole) and laccase modified platinum electrode (Pt). The miniature Pt biosensor was designed and constructed via the immobilization of laccase in an electroactive layer of the electrode coated with thin polymeric film. This sensing arrangement utilized the catalytic oxidation of NE to norepinephrine quinone. The detection process was based on the oxidation of catecholamine in the presence of enzyme – laccase. With the optimized conditions, the analytical performance demonstrated selectivity in a wide linear range (0.1–200x10-6 M) with a detection limit of 240 nM and a quantification limit of 365 nM. Moreover, the method was successfully applied for selective NE determination in the presence of interfering substances.

Atrazine (ATR) is a widely used chlorinated herbicide from the s-triazine group. Due to the widespread use of ATR, it leaks into the environment and is detected in drinking water, exceeding the WHO-acceptable concentration of atrazine in drinking water, which is 2 μg/L. The aim of our study was to determine toxicity, protein degradation and genotoxicity of ATR at concentrations of 10; 1; 0.1; 0.01 mg/L on Chlorella vulgaris and with the application of E. coli bioluminescent biosensor strains. We measured the content of chlorophyll a, b, carotenoids in Chlorella vulgaris and the inhibition of this algae culture growth. E. coli RFM443 strains with gene constructs grpE:luxCDABE, lac:luxCDABE, recA:luxCDABE and E. coli strain MM294 trc:luxCDABE were used to determine toxicity, degradation of cellular proteins and genotoxicity. On the base of the obtained results, we concluded that ATR in the tested concentrations shows a toxic effect in relation to Chlorella vulgaris. ATR is toxic and genotoxic in E. coli RFM443 strains with grpE, lac, recA promoters and causes degradation of cellular proteins. Moreover, we have detected ATR toxicity toward the GFP protein in E. coli strain MM294-GFP. Taking into account the toxicity and genotoxicity of ATR documented in our research and in the experiments of other authors, we conclude that the presence of this herbicide in surface waters and drinking water is a serious threat to living organisms.

Two highly sensitive optical sensor topologies are proposed and simulated in this paper. The proposed structures are optimized to provide better performance characteristics such as sensitivity, detection limit, and quality factor. They are based on two-dimensional photonic crystals consisting of rectangular arrays of GaAs rods in SiO2 substrates. Such lattices have bandgaps for transverse magnetic modes. Two-dimensional finite difference time domain and plane wave expansion methods are used for the simulation and analysis of the refractive index sensors and particle swarm optimization method is used to optimize the structural parameters. The designed structures show a high sensitivity to refractive index variations. They are able to detect refractive indices from 1.33 to 1.5. An excellent figure of merit equal to 737 RIU−1 is observed for the proposed structure and a significant improvement is observed compared to the structures reported in the literature.

In this paper, the authors analyse the propagation of surface Love waves in an elastic layered waveguide (elastic guiding layer deposited on an elastic substrate) covered on its surface with a Newtonian liquid layer of finite thickness. By solving the equations of motion in the constituent regions (elastic substrate, elastic surface layer and Newtonian liquid) and imposing the appropriate boundary conditions, the authors established an analytical form of the complex dispersion equation for Love surface waves. Further, decomposition of the complex dispersion equation into its real and imaginary part, enabled for evaluation of the phase velocity and attenuation dispersion curves of the Love wave. Subsequently, the influence of the finite thickness of a Newtonian liquid on the dispersion curves was evaluated. Theoretical (numerical) analysis shows that when the thickness of the Newtonian liquid layer exceeds approximately four penetration depths 4δ of the wave in a Newtonian liquid, then this Newtonian liquid layer can be regarded as a semi-infinite half-space. The results obtained in this paper can be important in the design and optimization of ultrasonic Love wave sensors such as: biosensors, chemosensors and viscosity sensors. Love wave viscosity sensors can be used to assess the viscosity of various liquids, e.g. liquid polymers.