Publisher Summary The electroactivity of nucleic acids was discovered several years ago. It was shown that at mercury electrodes, adenine and cytosine were reduced in ssDNA while guanine produced an anodic signal due to the oxidation of guanine reduction product. The DNA signals at mercury electrodes are highly sensitive to changes in DNA structure due to DNA denaturation and renaturation, as well as to minor structural changes resulting from DNA premelting and DNA damage. The changes in DNA structure are reflected not only by the DNA faradaic responses but also by non-faradaic signals due to adsorption/desorption of DNA. Several interesting principles have been used in the development of the DNA sensors—such as amplified electrochemical analysis, investigation of charge transport, and tracing of changes in conformation of DNA. The s ensors for DNA hybridization and DNA damage lead the field of the electrochemistry of nucleic acids. The chapter briefly summarizes some properties of the elimination voltammetry with linear scan (EVLS) method. Oscillographic polarography, at controlled alternating current, was used in the electrochemical analysis of nucleic acids.

Electrochemistry of nucleic acids.

Extraction and quantification of saponins: A review

This review covers the application of capillary electromigration methods to analyze foods and food components, including amino acids, biogenic amines, peptides, proteins, DNAs, carbohydrates, phenols, polyphenols, pigments, toxins, pesticides, vitamins, additives, small organic and inorganic ions, chiral compounds, and other compounds in foods, as well as those applications of CE for monitoring food interactions and food processing. The use of microchips as well as other foreseen trends in food analysis by CE are discussed. Papers that were published during the period June 2005-March 2007 are included following the previous review by Cifuentes (Electrophoresis 2006, 27, 283-303).

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Recent advances in the application of capillary electromigration methods for food analysis

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

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Recent developments in optical detection methods for microchip separations

Fruit and vegetable juices and beverages are generally preserved by thermal processing, currently being the most cost-effective means ensuring microbial safety and enzyme deactivation. However, thermal treatments may induce several chemical and physical changes that impair the organoleptic properties and may reduce the content or bioavailability of some nutrients; in most cases, these effects are strongly dependent on the food matrix. Moreover, the efficacy of treatments can also be affected by the complexity of the product and microorganisms. This review covers researches on this topic, with a particular emphasis on products derived from different botanical sources. Technologies presented include conventional and alternative thermal treatments. Advances toward hurdle-based technology approaches have been also reviewed.

Thermal Treatments for Fruit and Vegetable Juices and Beverages: A Literature Overview

Inactivation of Alicyclobacillus acidoterrestris in orange juice by saponin extracts combined with heat-treatment.

The semiquantitative detection of Alicyclobacillus acidoterrrestris in orange juice by reverse-transcriptase polymerase chain reaction (RT-PCR) with a linear dynamic range of 2×105– 2 colony forming units (CFU)/mL in terms of cell count is described. Separation, detection, and quantification of the RT-PCR products were accomplished using the Agilent 2100 bioanalyzer in conjunction with the DNA 1000 LabChip kit. After 0 and 12 h of enrichment, it was possible to generate a linear standard curve between the amount of cells and amplicon concentration of RT-PCR and PCR products. Using this method, cell diminution was verified in samples of orange juice treated with a natural inhibitor (Sapindus saponaria), determining the persistence of viable cells. Semiquantitative RT-PCR using the Agilent 2100 bioanalyzer is a potentially useful approach for rapid in vitro determination of A. acidoterrestris and monitoring of inhibitor susceptibility for the orange juice-producing industry.

Semiquantitative determination of Alicyclobacillus acidoterrestris in orange juice by reverse-transcriptase polymerase chain reaction and capillary electrophoresis--laser induced fluorescence using microchip technology.

This study outlines the quantification of low levels of Alicyclobacillus acidoterrestris in pure cultures, since this bacterium is not inactivated by pasteurization and may remain in industrialized foods and beverages. Electroconductive polymer-modified fluorine tin oxide (FTO) electrodes and multiple nanoparticle labels were used for biosensing. The detection ofA. acidoterrestris in pure cultures was performed by reverse transcription polymerase chain reaction (RT-PCR) and the sensitivity was further increased by asymmetric nested RT-PCR using electrochemical detection for quantification of the amplicon. The quantification of nested RT-PCR products by Ag/Au-based electrochemical detection was able to detect 2 colony forming units per mL (CFU mL−1) of spores in pure culture and low detection and quantification limits (7.07 and 23.6 nM, respectively) were obtained for the target A. acidoterrestris on the electrochemical detection bioassay.

Sequence-specific electrochemical detection of Alicyclobacillus acidoterrestris DNA using electroconductive polymer-modified fluorine tin oxide electrodes.

It was used reverse-transcriptase polymerase chain reaction (RT-PCR) followed by capillary electrophoresis on a microchip to probe the viability of Alicyclobacillus acidoterrestris spores after inactivation with saponin and heat. The method was shown to be suitable for the purpose, and was faster and more sensitive than the traditional plating technique, the standard of the food industry. The limits of quantification and detection were 0.0107 and 0.0039 ng µL-1 of amplified DNA, respectively. The correlation coefficient (r) between traditional plating and our method was 0.9977, which indicates an excellent correspondence between them. Consequently, it was possible to assess, with confidence, the viability of bacteria using the RT-PCR reaction for detection. It was evaluated the potential of this molecular method over traditional microbiology in the inactivation of A. acidoterrestris by saponin as an effective agent, potentiated by heat.

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A Comparison of Plating and Reverse Transcriptase Polymerase Chain Reaction Followed by Microchip Electrophoresis for the Inactivation of Alicyclobacillus acidoterrestris Using Saponin

Maribel Elizabeth Funes-Huacca

Papers

Inactivation of Alicyclobacillus acidoterrestris in orange juice by saponin extracts combined with heat-treatment.

Semiquantitative determination of Alicyclobacillus acidoterrestris in orange juice by reverse-transcriptase polymerase chain reaction and capillary electrophoresis--laser induced fluorescence using microchip technology.

Sequence-specific electrochemical detection of Alicyclobacillus acidoterrestris DNA using electroconductive polymer-modified fluorine tin oxide electrodes.

A Comparison of Plating and Reverse Transcriptase Polymerase Chain Reaction Followed by Microchip Electrophoresis for the Inactivation of Alicyclobacillus acidoterrestris Using Saponin