title: Mechanism of polymer-induced hemolysis: nanosized pore formation and osmotic lysis.
abstract: Hemolysis induced by antimicrobial polymers was examined to gain an understanding of the mechanism of polymer toxicity to human cells. A series of cationic amphiphilic methacrylate random copolymers containing primary ammonium groups as the cationic functionality and either butyl or methyl groups as hydrophobic side chains have been prepared by radical copolymerization. Polymers with 0-47 mol % methyl groups in the side chains, relative to the total number of monomeric units, showed antimicrobial activity but no hemolysis. The polymers with 65 mol % methyl groups or 27 mol % butyl groups displayed both antimicrobial and hemolytic activity. These polymers induced leakage of the fluorescent dye calcein trapped in human red blood cells (RBCs), exhibiting the same dose-response curves as for hemoglobin leakage. The percentage of disappeared RBCs after hemolysis increased in direct proportion to the hemolysis percentage, indicating complete release of hemoglobin from fractions of RBCs (all-or-none leakage) rather than partial release from all cells (graded leakage). An osmoprotection assay using poly(ethylene glycol)s (PEGs) as osmolytes indicated that the PEGs with MW > 600 provided protection against hemolysis while low molecular weight PEGs and sucrose had no significant effect on the hemolytic activity of polymers. Accordingly, we propose the mechanism of polymer-induced hemolysis is that the polymers produce nanosized pores in the cell membranes of RBCs, causing an influx of small solutes into the cells and leading to colloid-osmotic lysis.
authors.affiliation: Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Iva
authors.initials: I
authors.lastname: Sovadinova
authors.forename: Edmund F
authors.initials: EF
authors.lastname: Palermo
authors.forename: Rui
authors.initials: R
authors.lastname: Huang
authors.forename: Laura M
authors.initials: LM
authors.lastname: Thoma
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kuroda
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics*; D004910:Erythrocyte Membrane / Q000737:chemistry*; D004926:Escherichia coli / Q000254:growth & development*; D006454:Hemoglobins / Q000737:chemistry; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D009995:Osmosis / Q000187:drug effects; D011109:Polymethacrylic Acids / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D006454:Hemoglobins; D011109:Polymethacrylic Acids; C030613:polymethacrylic acid