Tracking and synchronization of the yeast cell cycle using dielectrophoretic opacity

Cell cycle synchronization is an important tool for the study of the cell division stages and signalling. It provides homogeneous cell cultures that are of importance to develop and improve processes such as protein synthesis and drug screening. The main approach today is the use of metabolic agents that block the cell cycle at a particular phase and accumulate cells at this phase, disturbing the cell physiology. We provide here a non-invasive and label-free continuous cell sorting technique to analyze and synchronize yeast cell division. By balancing opposing dielectrophoretic forces at multiple frequencies, we maximize sensitivity to the characteristic shape and internal structure changes occurring during the yeast cell cycle, allowing us to synchronize the culture in late anaphase

Label-free detection of Babesia bovis infected red blood cells using impedance spectroscopy on microfabricated flow cytometer

Impedance spectroscopy is a powerful tool for label-free analysis and characterisation of living cells. In this work, we achieved the detection of Babesia bovis infected red blood cells using impedance spectroscopy on a microfabricated flow cytometer. The cellular modifications caused by the intracellular parasite result in a shift in impedance which can be measured dielectrically. Thus, a rapid cell-by-cell detection with microliter amounts of reagents is possible. Unlike other diagnostic tests, this method does not depend on extensive sample pre-treatment or expensive chemicals and equipment

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Entretien avec Luciano Berio

— Le rapport entre langue et musique est, chez vous, essentiel ; dans quelle mesure est-il lié aux mouvements d’avant-garde italiens des années soixante, tels que I Novissimi par exemple ? L. B. : J’ai eu, de ce point de vue, un développement atypique. En ce qui concerne la littérature italienne, j’avais trois repères qui sont d’ailleurs restés très forts : ce sont Sanguineti, Calvino et Eco. Avec Eco, j’ai fait les premières expériences sur Joyce à travers Thema (Omaggio a Joyce) qui était p..

Entretien avec Luciano Berio

– Le rapport entre langue et musique est, chez vous, essentiel ; dans quelle mesure est-il lié aux mouvements d’avant-garde italiens des années soixante, tels que I Novissimi par exemple ? J’ai eu, de ce point de vue, un développement atypique. En ce qui concerne la littérature italienne, j’avais trois repères qui sont d’ailleurs restés très forts : Sanguineti, Calvino et Eco. Avec Umberto Eco, j’ai fait les premières expériences sur Joyce à travers Tema (Omaggio a Joyce) qui était prévu pour..

Microfluidic device for continuous dielectrophoretic separation of cells in division

This paper reports on a novel method for on-chip continuous separation of divid- ing and non-dividing cells based on differences in their dielectric properties. By means of two opposite dielectrophoretic force fields at multiple frequencies, the two populations of cells flowing through the microfluidic device are focused towards distinct equilibrium positions, which can be correlated to their cell cycle

Focusing and continuous separation of cells in a microfluidic device using lateral dielectrophoresis

We have fabricated a microfluidic device based on a novel geometrical arrangement of lateral metal electrodes and a patterned insulator. Our device combines the concept of insulator-based “electrodeless” dielectrophoresis with multiple frequencies to achieve focusing and continuous separation of dielectric particles flowing through a channel. The opposition of two DEP- force fields defines a position of equilibrium for the dielectric particles placed in these fields. The equilibrium is externally controllable by the applied signals at different frequencies and is a function of the dielectric properties of the particles and their surrounding medium. Opposite DEP-forces were used to accurately focus a stream of beads and yeast cells at different positions across the channel by simply adjusting potentials and frequencies. The same opposition of forces was then extended to the continuous separation of particles with different dielectric properties. A numerical calculation allowed extracting dielectric properties of the particles from their equilibrium positions

A miniaturized continuous dielectrophoretic cell sorter and its applications

There is great interest in highly sensitive separation methods capable of quickly isolating a particular cell type within a single manipulation step prior to their analysis. We present a cell sorting device based on the opposition of dielectrophoretic forces that discriminates between cell types according to their dielectric properties, such as the membrane permittivity and the cytoplasm conductivity. The forces are generated by an array of electrodes located in both sidewalls of a main flow channel. Cells with different dielectric responses perceive different force magnitudes and are, therefore, continuously focused to different equilibrium positions in the flow channel, thus avoiding the need of a specific cell labeling as discriminating factor. We relate the cells’ dielectric response to their output position in the downstream channel. Using this microfluidic platform that integrates a method of continuous-flow cell separation based on multiple frequency dielectrophoresis, we succeeded in sorting viable from nonviable yeast with nearly 100% purity. The method also allowed to increase the infection rate of a cell culture up to 50% of parasitemia percentage, which facilitates the study of the parasite cycle. Finally, we prove the versatility of our device by synchronizing a yeast cell culture at a particular phase of the cell cycle avoiding the use of metabolic agents interfering with the cells’ physiology