Induced decrease in small molecule electrotransfer efficiency by extracellular calcium

Abstract

Electroporation is a method, developed in order to deliver exogenous biocompounds (anticancer drugs, nucleic acids, proteins, etc.) to cells and tissues, which are mostly designed for cancer treatment purposes. An alternative to chemotherapeutic drugs can be Ca2+ ions which are universal signal messengers that regulate a multitude of cellular functions. The application of calcium electroporation is a novel anticancer treatment that selectively kills cancer cells by necrosis, a cell death pathway that can induce the immune system due to the high release of antigens. However, the mechanism behind the calcium electroporation remains unclear to this day. Calcium ions are also known to play a key role in membrane resealing, potentially altering the pore dynamics and molecular delivery during electroporation. To elucidate the role of calcium ions in the process of electroporation, we used different extracellular calcium concentrations with different fluorescent dyes (Propidium iodide (PI), YO-PRO-1 and ethidium bromide (EtBr) in electroporation media. Experiments were performed using flow cytometry and fluorescent microscopy methods. In conclusion, we report that extracellular calcium induces a negative effect to the small molecule (Propidium iodide (PI), YO-PRO-1 and ethidium bromide (EtBr), transfer into the cells after electroporation. Keywords: calcium electroporation, microsecond electroporation, calcium, PI electrotransfer, pore resealing, membrane repair