title: Tunable, antibacterial activity of silicone polyether surfactants.
abstract: Silicone surfactants are used in a variety of applications, however, limited data is available on the relationship between surfactant structure and biological activity. A series of seven nonionic, silicone polyether surfactants with known structures was tested for in vitro antibacterial activity against Escherichia coli BL21. The compounds varied in their hydrophobic head, comprised of branched silicone structures with 3-10 siloxane linkages and, in two cases, phenyl substitution, and hydrophilic tail of 8-44 poly(ethylene glycol) units. The surfactants were tested at three concentrations: below, at, and above their Critical Micelle Concentrations (CMC) against 5 concentrations of E. coli BL21 in a three-step assay comprised of a 14-24h turbidometric screen, a live-dead stain and viable colony counts. The bacterial concentration had little effect on antibacterial activity. For most of the surfactants, antibacterial activity was higher at concentrations above the CMC. Surfactants with smaller silicone head groups had as much as 4 times the bioactivity of surfactants with larger groups, with the smallest hydrophobe exhibiting potency equivalent to sodium dodecyl sulfate (SDS). Smaller PEG chains were similarly associated with higher potency. These data link lower micelle stability and enhanced permeability of smaller silicone head groups to antibacterial activity. The results demonstrate that simple manipulation of nonionic silicone polyether structure leads to significant changes in antibacterial activity.
authors.affiliation: School of Biomedical Engineering, McMaster University, 1280 Main St. West, Hamilton, ON, Canada L8S 4M1.
authors.forename: Madiha F
authors.initials: MF
authors.lastname: Khan
authors.affiliation: Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St. West, Hamilton, ON, Canada L8S 4M1.
authors.forename: Laura
authors.initials: L
authors.lastname: Zepeda-Velazquez
authors.affiliation: School of Biomedical Engineering, McMaster University, 1280 Main St. West, Hamilton, ON, Canada L8S 4M1; Department of Chemistry and Chemical Biology, McMaster University, 1280 Main St. West, Hamilton, ON, Canada L8S 4M1. Electronic address: mabrook@mcmaster.ca.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Brook
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects; D004987:Ethers / Q000737:chemistry; D008826:Microbial Sensitivity Tests; D012828:Silicones / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004987:Ethers; D012828:Silicones; D013501:Surface-Active Agents
keywords: Antibacterial activity; Live-dead stain; Nonionic surfactants; Silicone polyethers; Turbidometric screen