Sterility testing by CE: a comparison of online preconcentration approaches in capillaries with greater internal diameters

Sorting and simultaneous quantitation of intact mixed-cell samples via capillary isotachophoresis

A great need currently exists for rapid, inexpensive, and accurate methods for microbial analysis in the medical, food, industrial, and water quality fields. Here, a novel capillary isotachophoresis (CITP) method is presented for the focusing, sorting, and quantitation of intact cells in mixed samples based on their electrophoretic mobility ranges. Using a series of ion spacers dissolved in the sample, this technique results in several efficient cell peaks in the electropherogram corresponding to specific cell electrophoretic mobility ranges. The concentrations of different species in mixed-cell samples are determined from the cell peak areas and the known peak response factors for the cell species using a series of linear equations. Method design and optimization are discussed, including the choice of running buffer, pH, and ion spacers. Mixed-cell samples of up to four different species were focused and quantified as a proof-of-principle of the method. When sample cell concentrations were toward the middle of the linear response range, accuracies between 1% and 11% and relative standard deviations of 1%-14% were obtained, depending on the number of cell species in the mixture. This work provides a useful basis for future studies of cell quantitation using CITP, which could be potentially applied to a variety of fields including cell growth studies, microbial contamination testing, and sterility testing.

Modern Approach to Medical Diagnostics - the Use of Separation Techniques in Microorganisms Detection

Background:

Analytical chemistry and biotechnology as an interdisciplinary fields of science have been developed during many years and are experiencing significant growth, to cover a wide range of microorganisms separation techniques and methods, utilized for medical therapeutic and diagnostic purposes. Currently scientific reports contribute by introducing electrophoretical and immunological methods and formation of devices applied in food protection (avoiding epidemiological diseases) and healthcare (safety ensuring in hospitals).

Methods:

Electrophoretic as well as nucleic-acid-based or specific immunological methods have contributed tremendously to the advance of analyses in recent three decades, particularly in relation to bacteria, viruses and fungi identifications, especially in medical in vitro diagnostics, as well as in environmental or food protection.

Results:

The paper presents the pathogen detection competitiveness of these methods against conventional ones, which are still too time consuming and also labor intensive. The review is presented in several parts following the current trends in improved pathogens separation and detection methods and their subsequent use in medical diagnosis.

Discussion:

Part one, consists of elemental knowledge about microorganisms as an introduction to their characterization: descriptions of divisions, sizes, membranes (cells) components. Second section includes the development, new technological and practical solution descriptions used in electrophoretical procedures during microbes analyses, with special attention paid to bio-samples analyses like blood, urine, lymph or wastewater. Third part covers biomolecular areas that have created a basis needed to identify the progress, limitations and challenges of nucleic-acid-based and immunological techniques discussed to emphasize the advantages of new separative techniques in selective fractionating of microorganisms.

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.

Review of recent developments of on-line sample stacking techniques and their application in capillary electrophoresis

Capillary electrophoresis (CE) has become one of the most useful tools in separation science because of its high separation efficiency, low cost, versatility, ease of sample preparation and automation. However, some limitations of CE, such as poor concentration sensitivity due to its lower sample loading and shorter optical path length, limits its further applications in separation science. In order to solve this problem, various on-line sample preconcentration techniques such as transient isotachophoresis preconcentration, field-enhanced sample stacking, micelle to solvent stacking, micelle collapse, dynamic pH junction, sweeping, solid phase extraction, single drop microextraction and liquid phase microextraction have been combined with CE. Recent developments, applications and some variants together with different combinations of these techniques integrating in CE are reviewed here and our discussions will be confined to the past three years (2008–2011).