Detection of microbial food contaminants and their products by capillary electromigration techniques

A single-round selection of selective DNA aptamers for mammalian cells by polymer-enhanced capillary transient isotachophoresis

A single-round DNA aptamer selection for mammalian cells was successfully achieved for the first time using a capillary electrophoresis (CE)-based methodology called polymer-enhanced capillary transient isotachophoresis (PectI). The PectI separation yielded a single peak for the human lung cancer cell line (PC-9) complexed with DNA aptamer candidates, which was effectively separated from a free randomized DNA library peak, ensuring no contamination from free DNA in the PC-9-DNA aptamer complex fraction. The DNA aptamer candidates obtained after a single-round selection employing counter selection with HL-60 were proven to bind selectively and form kinetically stable complexes with PC-9 cells. Interestingly, most aptamer candidates showed high binding ability (K_d = 70-350 nM) with different extents of binding on the cell surface. These facts proved that a single-round selection for mammalian cells by PectI is feasible to obtain various types of aptamer candidates, which have high-affinity even for non-overexpressed but unique targets on the cell surface in addition to overexpressed targets.

Taking Advantage of Electric Field Induced Bacterial Aggregation for the Study of Interactions between Bacteria and Macromolecules by Capillary Electrophoresis

The quantification of interaction stoichiometry and binding constant between bacteria (or other microorganism) and (macro)molecules remains a challenging issue for which only a few adapted methods are available. In this paper, a new methodology was developed for the determination of the interaction stoichiometry and binding constant between bacteria and (macro)molecules. The originality of this work is to take advantage of the bacterial aggregation phenomenon to directly quantify the free ligand concentration in equilibrated bacteria-ligand mixtures using frontal analysis continuous capillary electrophoresis. The described methodology does not require any sample preparation such as filtration step or centrifugation. It was applied to the study of interactions between Erwinia carotovora and different generations of dendrigraft poly-L-lysines leading to quantitative information (i.e., stoichiometry and binding site constant). High stoichiometries in the order of 10(6)-10(7) were determined between nanometric dendrimer-like ligands and the rod-shaped micrometric bacteria. The effect of the dendrimer generation on the binding constant and the stoichiometry is discussed. Stoichiometries were compared with those obtained by replacing the bacteria by polystyrene microbeads to demonstrate the internalization of the ligands inside the bacteria and the increase of the specific surface via the formation of vesicles.

Multiplex ligase-based genotyping methods combined with CE

In this genomic era, the ability to assay multiple genomic hot spots that have strong clinical implications is greatly desired. Conventional PCR-based methods suffer from frequent false-positive detections, particularly when a multiplex analysis is desirable. As an alternative to the error-prone conventional methods, multiplex ligase-based genotyping methods combined with CE have a strong potential. In this review, both previously developed methods and emerging methods are described to reveal the specificity, sensitivity, and simplicity of the ligase-based methods. For each step (ligation, amplification, and separation), the principles of several alternative methods are discussed along with their applications to explore the future development of ligase-based diagnostic methods.

Current development of microfluidic immunosensing approaches for mycotoxin detection via capillary electromigration and lateral flow technology

Mycotoxin contamination in the food chain has caused serious health issues in humans and animals. Thus, a rapid on-site and lab-independent detection method for mycotoxins, such as aflatoxins (AFTs), is desirable. Microfluidic chip based immunosensor technology is one of the most promising methods for fast mycotoxin assays. In this review, we cover the major microfluidic immunosensors used for mycotoxin analysis, via flow-through (capillary electromigration) and lateral flow technology. Sample preparation from different matrices of agricultural products and foodstuffs is summarized. The choice of materials, fabrication strategies, and detection methods for microfluidic immunosensors are further discussed in detail. The sensors application in mycotoxin determination is also outlined. Finally, future challenges and opportunities are discussed.

Analytical characterization of wine and its precursors by capillary electrophoresis

The accurate determination of marker chemical species in grape, musts, and wines presents a unique analytical challenge with high impact on diverse areas of knowledge such as health, plant physiology, and economy. Capillary electromigration techniques have emerged as a powerful tool, allowing the separation and identification of highly polar compounds that cannot be easily separated by traditional HPLC methods, providing complementary information and permitting the simultaneous analysis of analytes with different nature in a single run. The main advantage of CE over traditional methods for wine analysis is that in most cases samples require no treatment other than filtration. The purpose of this article is to present a revision on capillary electromigration methods applied to the analysis of wine and its precursors over the last decade. The current state of the art of the topic is evaluated, with special emphasis on the natural compounds that have allowed wine to be considered as a functional food. The most representative revised compounds are phenolic compounds, amino acids, proteins, elemental species, mycotoxins, and organic acids. Finally, a discussion on future trends of the role of capillary electrophoresis in the field of analytical characterization of wines for routine analysis, wine classification, as well as multidisciplinary aspects of the so-called "from soil to glass" chain is presented.

Analysis of fumonisins B1 and B2 in spices and aromatic and medicinal herbs by HPLC-FLD with on-line post-column derivatization and positive confirmation by LC-MS/MS

Fumonisins are produced by the fungus Fusarium verticillioides, which are known to cause fatal diseases in some animals and humans. Here, we describe a sensitive, reproducible and reliable analytical method for the quantitative determination of fumonisins B(1) (FB(1)) and B(2) (FB(2)) in 112 spices and aromatic and medicinal herbs marketed in China. This method is based on high performance liquid chromatography and fluorescence detection (HPLC-FLD) coupled to a new on-line post-column derivatization using ortho-phthaldialdehyde with 2-mercaptoethanol and immunoaffinity column clean-up. Under the optimized experimental conditions, a complete separation of FB(1) and FB(2) was obtained using a Synergi C(18) column and a gradient elution at 0.8 mL min(-1) with methanol and 0.1 M phosphate buffer at pH 3.15. The limits of detection for FB(1) and FB(2) were both 40 μg kg(-1). Good recoveries were found for spiked samples with FB(1) and FB(2), ranging from 82.34% to 98.16% for FB(1) and from 72.58% to 97.10% for FB(2), with relative standard deviation (RSD) < 7.0%. 5 spices, 11 aromatic herbs and 96 medicinal herbs including 93 normal samples and 19 visibly moldy samples, which were spoiled artificially, were analyzed. The results showed that 8 (42.1%) visibly moldy samples and 8 (8.6%) normal samples were contaminated with FB(1) at mean contents of 129.0 and 165.9 μg kg(-1), and with FB(2) at 1745.0 and 256.8 μg kg(-1), respectively. Positive confirmation of detected samples was performed by liquid chromatography tandem electrospray ionization mass spectrometry (LC-ESI-MS/MS), using a triple quadrupole analyzer and operated in the multiple reaction monitoring mode.

Thirty years of capillary electrophoresis in food analysis laboratories: potential applications

CE has generated considerable interest in the research community since instruments were introduced by different trading companies in the 1990s. Nowadays, CE is popular due to its simplicity, speed, highly efficient separations and minimal solvent and reagent consumption; it can also be included as a useful technique in the nanotechnology field and it covers a wide range of specific applications in different fields (chemical, pharmaceutical, genetic, clinical, food and environmental). CE has been very well evaluated in research laboratories for several years, and different new approaches to improve sensitivity (one of the main drawbacks of CE) and robustness have been proposed. However, this technique is still not well accepted in routine laboratories for food analysis. Researching in data bases, it is easy to find several electrophoretic methods to determine different groups of analytes and sometimes they are compared in terms of sensitivity, selectivity, precision and applicability with other separation techniques. Although these papers frequently prove the potential of this methodology in spiked samples, it is not common to find a discussion of the well-known complexity of the matrices to extract analytes from the sample and/or to study the interferences in the target analytes. Summarizing, the majority of CE scientific papers focus primarily on the effects upon the separation of the analytes while ignoring their behavior if these analytes are presented in real samples.

Capillary electrophoresis characterization of molecularly imprinted polymer particles in fast binding with 17β-estradiol

Molecularly imprinted polymer (MIP) submicron particles were synthesized, using either ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate as a cross-linker, specifically for recognition of 17β-estradiol (E2). HPLC with fluorescence detection (HPLC-FD) results showed that 90(±5)% of E2 bound onto these particles after 2 min of incubation, and 96(±3)% after long equilibrium. The binding capacity was 8(±3) μmol/g for MIP particles prepared using ethylene glycol dimethacrylate, and 33-43(±8) μmol/g for using trimethylolpropane trimethacrylate. CE separation of MIP and non-imprinted polymer particles was successful when 50 mM borate buffer (pH 8.5) containing 0.005% w/v EOTrol™ LN in reverse polarity (-30 kV) was used. The electrophoretic mobilities of MIP and non-imprinted polymer particles, together with dynamic light scattering measurement of particle sizes, allowed for an estimation of their surface charges. Automated injection of E2 and particles in mixture set a lower limit of 20(±1) s on incubation time for the study of fast binding kinetics. The presence of E2 and bisphenol A (BPA) together tested the selectivity of MIP particles, when the two compounds competed for available binding cavities or sites. Addition of E2 after BPA confirmed E2 occupation of the specific binding cavities, via displacement of BPA.

Determination of fumonisins B₁ and B₂ in maize food products by a new analytical method based on high-performance liquid chromatography and fluorimetric detection with post-column derivatization

A sensitive and selective analytical method for the quantitative determination of fumonisins B(1) (FB(1)) and B(2) (FB(2)) in maize-based foods for direct human consumption is described. The method, based on high-performance liquid chromatography and fluorescence detection, presents a rapid and automated online post-column derivatization, performed with o-phthalaldehyde and N,N-dimethyl-2-mercaptoethylamine (Thiofluor™). A complete separation of fumonisins is achieved in less than 13 min by using a C18 column and a gradient elution. Fumonisins are extracted from the sample with a mixture of water, acetonitrile, and methanol. The filtered extract is purified by immunoaffinity column and FB(1) and FB(2) are eluted with methanol. The method has been successfully validated, and performances comply with -criteria of the Regulation EC No 401/2006.

Capillary electrophoresis for the analysis of contaminants in emerging food safety issues and food traceability

This review presents an overview of the applicability of CE in the analysis of chemical and biological contaminants involved in emerging food safety issues. Additionally, CE-based genetic analyzers' usefulness as a unique tool in food traceability verification systems was presented. First, analytical approaches for the determination of melamine and specific food allergens in different foods were discussed. Second, natural toxin analysis by CE was updated from the last review reported in 2008. Finally, the analysis of prion proteins associated with the "mad cow" crises and the application of CE-based genetic analyzers for meat traceability were summarized.

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

The use of capillary electromigration methods to analyze foods and food components is reviewed in this work. Papers that were published during the period April 2007 to March 2009 are included following the previous review by García-Cañas and Cifuentes (Electrophoresis, 2008, 29, 294-309). These works include the analysis of amino acids, biogenic amines, peptides, proteins, DNAs, carbohydrates, phenols, polyphenols, pigments, toxins, pesticides, vitamins, additives, small organic and inorganic ions and other compounds found in foods and beverages, as well as those applications of CE for monitoring food interactions and food processing. The use of microchips, CE-MS, chiral-CE as well as other foreseen trends in food analysis are also discussed including their possibilities in the very new field of Foodomics.

Recent food safety and food quality applications of CE-MS

The first on-line coupling of CE with MS detection more than 20 years ago provided a very powerful technique with a wide variety of applications, among which food analysis is of special interest, especially that dealing with food safety and food quality applications, the major topics of public interest nowadays. With this review article, we would like to show the most recent applications of CE-MS in both fields by recompiling and commenting articles published between January 2004 and October 2008. Although both applications are difficult to separate from each other, we have included in this work two main sections dealing with each specific field. Future trends will also be discussed.

Capillary electrophoresis-based methods for the determination of lipids--a review

Capillary electrophoresis (CE) is a high-resolution technique for the separation of complex biological and chemical mixtures. CE continues to emerge as a powerful tool in the determination of lipids. Here we review the analytical potential of CE for the determination of a wide range of lipids. The different classes of lipids are introduced, and the different modes of CE and optimization methods for the separation of lipids are described. The advantages and disadvantages of the different modes of CE compared to traditional methods like gas chromatography (GC) and liquid chromatography (LC) in the determination of lipids are discussed. Finally, the potential of CE in the determination of lipids in the future is illustrated.