Electrochemical Peptide-Based Sensors for Foodborne Pathogens Detection

Food safety and quality control pose serious issues to food industry and public health domains, in general, with direct effects on consumers. Any physical, chemical, or biological unexpected or unidentified food constituent may exhibit harmful effects on people and animals from mild to severe reactions. According to the World Health Organization (WHO), unsafe foodstuffs are especially dangerous for infants, young children, elderly, and chronic patients. It is imperative to continuously develop new technologies to detect foodborne pathogens and contaminants in order to aid the strengthening of healthcare and economic systems. In recent years, peptide-based sensors gained much attention in the field of food research as an alternative to immuno-, apta-, or DNA-based sensors. This review presents an overview of the electrochemical biosensors using peptides as molecular bio-recognition elements published mainly in the last decade, highlighting their possible application for rapid, non-destructive, and in situ analysis of food samples. Comparison with peptide-based optical and piezoelectrical sensors in terms of analytical performance is presented. Methods of foodstuffs pretreatment are also discussed.     

Evaluation of various biological activities of natural compounds by TLC/HPTLC

Abstract

Over the last years, thin layer chromatography (TLC) has become an increasingly important tool in the analysis of natural compounds, being used not only as a simple method of separation, identification, and quantitative determination of natural constituents, but also as a method for evaluating the potential applications of the separated compounds, different bioassays being compatible with TLC. This is due to the TLC advantages, of which could be mentioned: the possibility to simply, quickly, and flexibly analyze many samples in parallel, without the need for special steps of sample purification, obtaining visual results, and the possibility of multiple detections, all of these being achieved at very low costs. Considering these, the aim of this study is to give an overview on the application of TLC in evaluation of different biological activities of natural compounds, focusing on antioxidant, enzymatic, antimicrobial, and hormonal activities.     

Simultaneous determination of methylxanthines in different types of tea by a newly developed and validated TLC method

The aim of this paper is to develop a new simple, fast and economical method for simultaneous quantitative determination of methylxanthine compounds based on TLC combined with image analysis. To obtain certain results, both extraction and chromatographic separation were optimized. The optimum extraction conditions were maceration in ethanol-water 8:2, v/v. The chromatographic separations were done on the silica gel F(254) TLC plates developed with chloroform-dichloromethane-isopropanol, 4:2:1 v/v/v. Detection was performed under UV lamp at 254?nm and the evaluation of the chromatographic plate was based on digital processing of chromatographic images. The developed TLC method was validated for parameters such as specificity, linearity and range, LOD and LOQ, precision, robustness and accuracy. This method was then applied for determination of caffeine, theobromine and theophylline in different types of tea, commercially available. Moreover, the content of methylxanthines detected and determined in commercial tea samples can be used as chemical marker in quality control.     

Modeling of Thin-Layer Chromatographic Separation of Androstane Isomers

JPC – Journal of Planar Chromatography – Modern TLC - Modeling of thin-layer chromatographic separation of androstane isomers to find the optimum mobile phase is described in this...     

Determination of the Antioxidant Activity of Juices by Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The discovery of the implication of free radicals in the etiology of many diseases has led to increased interest in functional food...     

Beta‐lactoglobulin Electrochemical Detection Based with an Innovative Platform Based on Composite Polymer

In this work, we present a new electrochemical disposable platform based on poly(aniline‐co‐anthranilic acid) (PANI/PAA) composite polymer coupled with an aptamer for sensitive detection of β‐lactoglobulin. Firstly, PANI/PAA film was electrodeposited on the graphite screen‐printed electrode surface by cyclic voltammetry. The co‐polymer modified electrode was then employed as platform for the covalent immobilization of an amino‐modified aptamer. Various β‐lactoglobulin solutions, with a fixed amount of biotinylated oligonucleotide complementary sequence, were dropped onto the aptasensor surface. A streptavidin‐alkaline phosphatase conjugate was then employed to trace the affinity reaction. After the addition of 1‐naphthyl‐phosphate enzymatic substrate, 1‐naphthol electroactive product was detected by differential pulse voltammetry. A decrease in the signal was obtained when the target concentration was increased, in according to a signal‐off approach. After optimization of key experimental parameters, a dose‐response curve was obtained between 0.01–1.0 μg mL^?1 β‐lactoglobulin concentration range. The limit of detection of 0.053 μg L^?1 was obtained. Milk samples spiked with β‐lactoglobulin were analyzed.     

Characteristics of Volcanic Tuff from Macicasu (Romania) and Its Capacity to Remove Ammonia from Contaminated Air

In the present work, the capability of the volcanic tuff from Macicasu (Romania) to remove ammonia (NH₃) from air with different contamination levels during 24 h of adsorption experiments was investigated. The natural zeolitic volcanic tuff was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), the Brunauer–Emmett–Teller (BET) method, inductively coupled plasma optical emission spectrometry (ICP-OES), and thermogravimetric analysis (TGA). The adsorption capacities varied between 0.022 mg NH₃ g⁻¹ zeolite and 0.282 mg NH₃ g⁻¹ zeolite, depending on the NH₃ concentrations in the air and at the contact time. The nonlinear forms of the Langmuir and Freundlich isotherm models were used to fit the experimental data. Additionally, the adsorption of NH₃ was studied using nonlinear pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich kinetic model. Based on the total volume of pores of used volcanic tuff, the NH₃ was removed from the air both due to the physical adsorption of NH₃ gas and the ion exchange of NH₄⁺ (resulted from a reaction between NH₃ and H₂O adsorbed by the zeolite). Depending on the initial NH₃ concentration and the amount of volcanic tuff, the NH₃ concentrations can be reduced below the threshold of this contaminant in the air. The adsorption capacity of NH₃ per unit of zeolite (1 g) varied in the range of 0.022–0.282 mg NH₃ g⁻¹ depending on the NH₃ concentration in the air.     

Nanocomposites based on carbon nanotubes and redox-active polymers synthesized in a deep eutectic solvent as a new electrochemical sensing platform

Microchimica Acta - The redox polymer poly(methylene blue) was synthesized by electropolymerization in ethaline deep eutectic solvent (PMBDES), and employed in a new nanostructured composite...     

Evaluation of viability of retinal photoreceptor cells by using their endogenous electrical field

The rod photoreceptor cells are electrical dipoles sustained by cell metabolic energy. Polarity of photoreceptor cells is directly connected to the so-called "dark current" which circulate along the living photoreceptors. Since only the living cells in a good functional state display electrical polarity, the orientation of photoreceptors in static electric field reflects their viability as long as it depends on the functionality of molecular mechanisms that maintain the dark current.Studying the rod cells' orientation in static electric field at different times after their isolation is thus an accurate way to evaluate the cell viability/degeneration. Retinal transplant experiments in animals and humans, which are presently in progress, require a quick and reliable viability test of cells/tissue to be transplanted. Checking the orientation pattern of rod photoreceptors in static electric field prior to transplantation is a candidate method for an accurate cell viability test.