Fertilization state of Ascaris suum determined by electrorotation.

Electrorotation is a non-invasive technique that is capable of detecting changes in the morphology and physicochemical properties of microorganisms. The first detailed electrorotation study of the egg (ovum) of a parasitic nematode, namely Ascaris suum is described to show that electrorotation can rapidly differentiate between fertilized and non-fertilized eggs. Support for this conclusion is by optical microscopy of egg morphology, and also from modelling of the electrorotational response. Modelling was used to determine differences in the dielectric properties of the unfertilized and fertilized eggs, and also to investigate specific differences in the spectra of fertilized eggs only, potentially reflecting embryogenesis. The potential of electrorotation as an investigative tool is shown, as undamaged eggs can be subjected to further non-destructive and destructive techniques, which could provide further insight into parasite biology and epidemiology.

Analysis of parasites by electrorotation.

AIMS: The application of the AC electrokinetic technique of electrorotation for studying eukaryotic parasite transmission stages is reviewed. Electrorotation is a noninvasive technique that utilizes electrically energized microelectrode structures within micro-fluidic chambers to probe the physiological structure of micro-organisms. Application of the technique to the transmission life cycle stages of three separate genera of protozoan parasites, Cryptosporidium, Giardia and Cyclospora, and one nematode genus Ascaris, each of significant public health importance, is described. METHODS AND RESULTS: Standard electrorotation apparatus, consisting of micro-fabricated electrodes in a fluidic chip, quadrature sinusoidal signal generator, microscope and image capture system, was used to study each organism. Spectra of cellular rotation rate were recorded as a function of applied electric field frequency and compared with standardized biological tests, where appropriate, to illustrate the effectiveness and versatility of the electrorotation technique. CONCLUSIONS: Electrorotational determination of the viability of individual G. intestinalis cysts, Cryptosporidium parvum and Cyclospora cayetanensis oocysts has been achieved. The sporulation state of Cyclospora cayetanensis oocysts was also readily determined, as was the fertilization state of A. suum ova. SIGNIFICANCE AND IMPACT OF THE STUDY: Electrorotation is a simple, noninvasive and versatile analytical technique suited to a wide range of particle types and capable of incorporation into integrated Lab-on-a-chip devices.

Viability of Giardia intestinalis cysts and viability and sporulation state of Cyclospora cayetanensis oocysts determined by electrorotation.

Electrorotation is a noninvasive technique that is capable of detecting changes in the morphology and physicochemical properties of microorganisms. Electrorotation studies are reported for two intestinal parasites, Giardia intestinalis and Cyclospora cayetanensis. It is concluded that viable and nonviable G. intestinalis cysts can be differentiated by this technique, and support for this conclusion was obtained using a fluorogenic vital dye assay and morphological indicators. The viability of C. cayetanensis oocysts (for which no vital dye assay is currently available) can also be determined by electrorotation, as can their sporulation state. Modeling of the electrorotational response of these organisms was used to determine their dielectric properties and to gain an insight into the changes occurring within them. Electrorotation offers a new, simple, and rapid method for determining the viability of parasites in potable water and food products and as such has important healthcare implications.

Electrorotation and dielectrophoresis.

Using microelectrode structures, various forms of electric fields, such as non-uniform, rotating and travelling wave, can be imposed on particles of sizes ranging from proteins and viruses to micro-organisms and cells. Each type of particle responds to the forces exerted on them in a unique way, allowing for their controlled and selective manipulation as well as their characterization. Moreover, particles of the same type but of different viability can be distinguished in a simple, reliable manner. This review outlines the principles that govern the way in which bioparticles respond to these various field types, and how they can be exploited. Examples of current and potential biotechnological and biomedical applications are given, along with a critical comparison of current techniques.