Isolation of Langerhans islets by dielectrophoresis.

The purification of Langerhans islets from fragments of pancreatic exocrine tissue is a critical stage for the further transplantation of insulin secreting islets in patients affected by type I diabetes. Aim of our work was the evaluation of dielectrophoresis as a promising method for pancreatic islets isolation without physical contact in miniaturized lab-on-chip devices. DEP exploits the dielectric properties of particles suspended in a fluid, in a region where the amplitude of the electric field is characterized by a high gradient. Langerhans islets are aggregates of cells and have a minimum diameter of 50 microns. Dielectric models of pancreatic islets as cell aggregates were derived from single pancreatic beta cells model. Numerical simulations were performed to optimize the exact shape and size of the quadrupole microelectrode configuration and to determine the DEP forces acting on islets. A custom electronic setup was developed for the generation of sinusoidal signals with proper voltage and frequency and used to perform DEP experiments with samples of Langerhans islets. Dielectric models were found sufficiently accurate and negative DEP, showing repulsion from the electrodes, was observed for pancreatic islets. The results of this work demonstrate that Langerhans islet can be manipulated without physical contact by dielectrophoresis, a technique that can be applied on cell aggregates in miniaturized lab-on-chip devices.