Rossitza G. Alargova

On-Chip Dielectrophoretic Coassembly of Live Cells and Particles into Responsive Biomaterials

We report how live cells and functionalized colloidal particles can be coassembled into a variety of freely suspended bioactive structures using dielectrophoresis on a chip. Alternating electric fields were applied to dilute suspensions of yeast (S. cerevisiae) and NIH/3T3 mouse fibroblast cells to yield 1D chains and 2D arrays. The effects of voltage, frequency, pH, electrolyte concentration, cell concentration, and particle size on the assembly process were investigated in detail. Numerical simulations of the field intensity and energy allow the capture of the dynamics of cell-cell and cell-particle assembly. The simulation results illustrate that the electric field draws the functionalized synthetic particles between the cells and enables the formation of permanent chains and monolayer membranes composed of alternating cells and particles. The cell structures were bound into permanent structures by different types of functionalized synthetic particles and ligands that attached to the cells through biospecific or electrostatic interactions. The technique allowed the fabrication of magnetically responsive biomaterials that could be manipulated and transported into and out of the microchambers where they were formed.

On-chip electric field driven assembly of biocomposites from live cells and functionalized particles

Live cells and surface-functionalized synthetic microparticles are co-assembled on electrically controlled chips to yield permanent chains and one cell layer thick membranes that can be freely manipulated in external magnetic fields.

Dynamic light scattering study of polystyrene latex suspended in water at high temperatures and high pressures

Abstract The stability of monodispersive polystyrene spheres suspended in water has been studied at high pressure and temperature in the range of 0.1–28 MPa and 24–325°C. The diffusion coefficient of the latex was measured with dynamic light scattering using a special experimental cell for performing measurements at elevated pressure and temperature. It is found out that the influence of the increased pressure on the measured results is negligibly small. The elevation of temperature significantly increases the particle diffusion coefficient due to the viscosity decrease of the medium, but its dependence is well described by the theoretical predictions for the diffusion coefficients of the particles with constant size calculated at 24–275°C. This result means that the polystyrene spheres do not change in size and the suspension remains stable below 275°C at least in the time scale of our experiments. The change in the size of latex was observed at 300 and 325°C. The measured decrease of the diffusion coefficient with time could be related to the increase in the average particle size due to the beginning of the coagulation process, but some other effects as swelling of polystyrene might be also possible.

Fabrication of Novel Types of Colloidosome Microcapsules for Drug Delivery Applications

Abstract : Novel colloidosome microcapsules with aqueous gel cores and shells of different polymeric colloid particles have been prepared and characterized. Our preparation technique involves templating water-in-oil emulsions stabilized by either polymeric microrods or polystyrene (PS) latex particles and subsequent gelling of the aqueous phase with a suitable hydrocolloid. The obtained colloidosome microcapsules were transferred in water after dissolving the oil phase in ethanol and multiple centrifugation/washing cycles with ethanol and water. The presence of an aqueous gel core was found to enhance the structural integrity and mechanical stability of the obtained colloidosomes. In the case of latex particles forming the colloidosome membrane, the effect of the oil type on the final structure of the colloidosome shell was also studies. It was shown that by using appropriate oil, the latex particles within the colloidosome shell can be partially or completely swollen which not only binds them together but also allows direct control over the membrane pore size and its permeability with respect to entrapped species. Such microcapsules can find various applications for development of novel drug and vaccine delivery vehicles, slow release of cosmetic and food supplements.