title: Real-Time Observation of Antimicrobial Polycation Effects on Escherichia coli: Adapting the Carpet Model for Membrane Disruption to Quaternary Copolyoxetanes.
abstract: Real-time atomic force microscopy (AFM) was used for analyzing effects of the antimicrobial polycation copolyoxetane P[(C12)-(ME2Ox)-50/50], C12-50 on the membrane of a model bacterium, Escherichia coli (ATCC# 35218). AFM imaging showed cell membrane changes with increasing C12-50 concentration and time including nanopore formation and bulges associated with outer bacterial membrane disruption. A macroscale bactericidal concentration study for C12-50 showed a 4 log kill at 15 μg/mL with conditions paralleling imaging (1 h, 1x PBS, physiological pH, 25 °C). The dramatic changes from the control image to 1 h after introducing 15 μg/mL C12-50 are therefore reasonably attributed to cell death. At the highest concentration (60 μg/mL) further cell membrane disruption results in leakage of cytoplasm driven by detergent-like action. The sequence of processes for initial membrane disruption by the synthetic polycation C12-50 follows the carpet model posited for antimicrobial peptides (AMPs). However, the nanoscale details are distinctly different as C12-50 is a synthetic, water-soluble copolycation that is best modeled as a random coil. In a complementary AFM study, chemical force microscopy shows that incubating cells with C12-50 decreased the hydrophobicity across the entire cell surface at an early stage. This finding provides additional evidence indicating that C12-50 polycations initially bind with the cell membrane in a carpet-like fashion. Taken together, real time AFM imaging elucidates the mechanism of antimicrobial action for copolyoxetane C12-50 at the single cell level. In future work this approach will provide important insights into structure-property relationships and improved antimicrobial effectiveness for synthetic amphiphilic polycations.
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Congzhou
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Olga Y
authors.initials: OY
authors.lastname: Zolotarskaya
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Sithara S
authors.initials: SS
authors.lastname: Nair
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ehrhardt
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Ohman
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Wynne
authors.affiliation: Department of Chemical and Life Science Engineering and ‡Department of Forensic Science, Virginia Commonwealth University , Richmond, Virginia 23284, United States.|Department of Microbiology and Immunology and ∥McGuire Veterans Affairs Medical Center, VCU School of Medicine , Richmond, Virginia 23249, United States.
authors.forename: Vamsi K
authors.initials: VK
authors.lastname: Yadavalli
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004926:Escherichia coli / Q000187:drug effects*; D018625:Microscopy, Atomic Force; D011107:Polylysine / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry / Q000494:pharmacology*; D013501:Surface-Active Agents / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D011140:Polyurethanes; D013501:Surface-Active Agents; C000614794:copolyoxetane C12-50; D011107:Polylysine