Analysis of the role of elution buffers on the separation capabilities of dielectrophoretic devices

Field flow fractionation dielectrophoretic (FFF-DEP) devices are currently used, among the others, for the separation of tumor cells from healthy blood cells. To this end specific suspension/elution buffers (EBs), with reduced conductivity (with respect to that of the cell cytoplasm) are generally used. In this paper we investigate the long-term alterations of the cells and elution buffers. We find that the EB conductivity is critically modified within few minutes after cells suspension. In turn, this modification results in a change the ideal separation frequency of the FFF-DEP device. On the other hand we prove that DEP manipulation is preserved for more than three hours for cells suspended in the considered EBs. Keywords: Dielectrophoresis, Elution buffer, Circulating tumor cells, Cell motilit

Coupled molecular-dynamics and finite-element-method simulations for the kinetics of particles subjected to field-mediated forces

A computational approach that couples molecular-dynamics (MD) and the-finite-element-method (FEM) technique is here proposed for the theoretical study of the dynamics of particles subjected to electromechanical forces. The system consists of spherical particles (modeled as micrometric rigid bodies with proper densities and dielectric functions) suspended in a colloidal solution, which flows in a microfluidic channel in the presence of a generic nonuniform variable electric field generated by electrodes. The particles are subjected to external forces (e.g., drag or gravity) which satisfy a particlelike formulation that is typical of the MD approach, along with an electromechanical force that, in turn, requires the three-dimensional self-consistent solutions of correct continuum field equations during the integration of the equations of motion. In the MD-FEM method used in this work, the finite element method is applied to solve the continuum field equations while the MD technique is used for the stepwise explicit integration of the equations of motion. Our work shows the potential of coupled MD-FEM simulations for the study of electromechanical particles and opens a double perspective for implementing (a) MD away from the field of atomistic simulations and (b) the continuum-particle approach to cases where the conventional force evaluation used in MD is not applicable

Caged young pigeons mortality by Coleoptera larvae

Dermestidae and Tenebrionidae are well known inhabitants of bird’s nests and poultry farms, under favourable conditions they can be very abundant under favourable conditions. At times, their larvae shift from a scavenging behaviour to a parasitic/predatory one, entering nestling’s plumage and feeding on skin and feathers, and finally provoking skin damages and blood losses. These episodes mainly involve species of the genus Dermestes, but the tenebrionid Alphitobius diaperinus h also been reported to be responsible of similar cases. In June 2014, a mortality of caged young pigeons occurred in a family farm in Central Italy. Post-mortem examination of 1 of the dead nestlings revealed the presence, near the cloacal orifice, of a triangular shaped hole of about 1 cm side, with rounded edges facing inward and with bleeding from the cavity. Five coleoptera larvae 0.5-2 cm long were collected from the edges of the hole. Bacteriological examination of liver, intestine, and lungs revealed the presence of Escherichia coli in the lung samples. The 5 larvae were morphologically identified as Dermestes bicolor (4) and Alphitobius diaperinus (1). This is the first reported case of pigeon nestling’s mortality caused by Dermestidae and Tenebrionidae larvae acting as parasites/predators in Italy

Elution time changes due to anomalous DEP effects in microchannels under uniform and non-uniform electric fields

Conventional dielectrophoresis (DEP) force on cell and particle is altered in the proximity of the electrodes due to the failure of the dipole approximation. In these conditions an anomalous DEP (aDEP) force rules the particle manipulation. Anyhow, the role of the aDEP is barely considered in the design of DEP devices. Here we analyze, using a multiscale simulation approach, the aDEP effects in micro-fluidic device coupled with interdigitated channel commonly used in continuous mode field flow fractionation dielectrophoretic (FFF-DEP) devices for the separation of circulating tumor cells (MDA) and Lymphocytes (LYM). We study the propagation of an injected density of MDA and LYM respectively and evaluate how the aDEP changes the migrations of the cells. Keywords: Dielectrophoresis, Anomalous DEP, Field flow fractionation, Cell diffusio