Dielectrophoresis-based 'Lab-on-a-chip' devices for programmable binding of microspheres to target cells.

There is a general agreement on the fact that the Laboratory on chip (Lab-on-a-chip) technology will enable laboratory testing to move from laboratories employing complex equipments into non-laboratory settings. In this respect, dielectrophoresis (DEP) is a very valuable approach to design and produce Lab-on-a-chip devices able to manipulate microparticles and cells. In this study, we report the application of DEP-based devices for facilitating programmable interactions between microspheres and target tumor cells. We used two Lab-on-a-chip devices, one (the SmartSlide) carrying 193 parallel electrodes and generating up to 50 cylinder-shaped DEP cages, the other (the DEP array) carrying 102,400 arrayed electrodes and generating more than 10,000 spherical DEP cages. We determined whether these devices can be used to levitate and move microspheres and cells in order to obtain a forced interaction between microspheres and target cells. The first major point of this manuscript is that the DEP-based SmartSlide can be used for transfection experiments in which microspheres and target cells are forced to share the same DEP cage, leading to efficient binding of the microspheres to target cells. The data obtained using the DEP array show that this system allows the sequential, software-controlled binding of individually and independently moved single microspheres to a single target tumor cell. To our knowledge, this is the first report on the possible use of a DEP-based Lab-on-a-chip device for guided multiple binding of singularly moved microspheres to a single tumor cell. This approach can be of interest in the field of drug discovery, delivery and diagnosis.

Decoding two-dimensional polyacrylamide gel electrophoresis complex maps by autocovariance function: a simplified approach useful for proteomics.

This paper describes a mathematical approach applied for decoding the complex signal of two-dimensional polyacrylamide gel electrophoresis maps of protein mixtures. The method is helpful in extracting analytical information since separation of all the proteins present in the sample is still far from being achieved and co-migrating proteins are generally present in the same spot. The simplified method described is based on the study of the 2-D autocovariance function (2D-ACVF) computed on an experimental digitized map. The first part of the 2D-ACVF allows for the estimation of the number of proteins present in the sample (2D-ACVF computed at the origin) and of the separation performance (mean spot size). Moreover, the 2D-ACVF plot is a powerful tool in identifying order in the spot position, and singling it out from the complex separation pattern. This method was validated on synthetic maps obtained by computer simulation to describe 2-D PAGE real maps and reference maps retrieved from the SWISS-2DPAGE database. The results obtained are discussed by focusing on specific information relevant in proteomics: sample complexity, separation performance, and identification of spot trains related to post-translational modifications.