title: Cationic peptide exposure enhances pulsed-electric-field-mediated membrane disruption.
abstract: BACKGROUND
  The use of pulsed electric fields (PEFs) to irreversibly electroporate cells is a promising approach for destroying undesirable cells. This approach may gain enhanced applicability if the intensity of the PEF required to electrically disrupt cell membranes can be reduced via exposure to a molecular deliverable. This will be particularly impactful if that reduced PEF minimally influences cells that are not exposed to the deliverable. We hypothesized that the introduction of charged molecules to the cell surfaces would create regions of enhanced transmembrane electric potential in the vicinity of each charged molecule, thereby lowering the PEF intensity required to disrupt the plasma membranes. This study will therefore examine if exposure to cationic peptides can enhance a PEF's ability to disrupt plasma membranes.
  
  
  RESULTS
  We exposed leukemia cells to 40 μs PEFs in media containing varying concentrations of a cationic peptide, polyarginine. We observed the internalization of a membrane integrity indicator, propidium iodide (PI), in real time. Based on an individual cell's PI fluorescence versus time signature, we were able to determine the relative degree of membrane disruption. When using 1-2 kV/cm, exposure to >50 μg/ml of polyarginine resulted in immediate and high levels of PI uptake, indicating severe membrane disruption, whereas in the absence of peptide, cells predominantly exhibited signatures indicative of no membrane disruption. Additionally, PI entered cells through the anode-facing membrane when exposed to cationic peptide, which was theoretically expected.
  
  
  CONCLUSIONS
  Exposure to cationic peptides reduced the PEF intensity required to induce rapid and irreversible membrane disruption. Critically, peptide exposure reduced the PEF intensities required to elicit irreversible membrane disruption at normally sub-electroporation intensities. We believe that these cationic peptides, when coupled with current advancements in cell targeting techniques will be useful tools in applications where targeted destruction of unwanted cell populations is desired.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America; Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Kennedy
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Aiken
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: Kaytlyn A
authors.initials: KA
authors.lastname: Beres
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Hahn
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Kamin
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: Susan C
authors.initials: SC
authors.lastname: Hagness
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: John H
authors.initials: JH
authors.lastname: Booske
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, United States of America; Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, Wisconsin, United States of America.
authors.forename: William L
authors.initials: WL
authors.lastname: Murphy
mesh_terms: D002412:Cations; D002462:Cell Membrane / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004560:Electricity; D004705:Endocytosis / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D010455:Peptides / Q000494:pharmacology*; D011419:Propidium / Q000378:metabolism; D055672:Static Electricity
chemical_list: D002412:Cations; D010455:Peptides; C015462:polyarginine; D011419:Propidium