Dvoracek, Charlene M. (2009-05). Antimicrobial Activity of Cationic Antiseptics in Layer-by-Layer Thin Film Assemblies. Master's Thesis. Thesis uri icon

abstract

  • Layer-by-layer (LbL) assembly has proven to be a powerful technique for assembling thin films with a variety of properties including electrochromic, molecular sensing, oxygen barrier, and antimicrobial. LbL involves the deposition of alternating cationic and anionic ingredients from solution, utilizing the electrostatic charges to develop multilayer films. The present work incorporates cationic antimicrobial agents into the positively-charged layers of LbL assemblies. When these thin films are exposed to a humid environment, the antimicrobial molecules readily diffuse out and prevent bacterial growth. The influence of exposure time, testing temperature, secondary ingredients and number of bilayers on antimicrobial efficacy is evaluated here. Additionally, film growth and microstructure are analyzed to better understand the behavior of these films. The antimicrobial used here is a positively-charged quaternary ammonium molecule (e.g. cetyltrimethylammonium bromide [CTAB]) that allow assemblies to be made with or without an additional polycation like polydiallyldimethylamine. While films without this additional polymer are effective, they do not have the longevity or uniformity of films prepared with its addition. All of the recipes studied show linear growth as a function of the number of bilayers deposited and this growth is relatively thick (i.e. > 100 nm per bilayer). In general, 10-bilayer films prepared with CTAB and poly(acrylic acid) are able to achieve a 2.3 mm zone of inhibition against S. aureus bacteria and 1.3 mm against E. coli when test are conducted at body temperature (i.e. 37oC). Fewer bilayers reduces efficacy, but lower test temperatures improve zones of inhibition. As long as they are stored in a dry atmosphere, antimicrobial efficacy was found to persist even when films were used four weeks after being prepared. The best films remain effective (i.e. antimicrobially active) for 4-6 days of constant exposure to bacteria-swabbed plates. This technology holds promise for use in transparent wound bandages and temporary surface sterilization.
  • Layer-by-layer (LbL) assembly has proven to be a powerful technique for
    assembling thin films with a variety of properties including electrochromic, molecular
    sensing, oxygen barrier, and antimicrobial. LbL involves the deposition of alternating
    cationic and anionic ingredients from solution, utilizing the electrostatic charges to
    develop multilayer films. The present work incorporates cationic antimicrobial agents
    into the positively-charged layers of LbL assemblies. When these thin films are exposed
    to a humid environment, the antimicrobial molecules readily diffuse out and prevent
    bacterial growth. The influence of exposure time, testing temperature, secondary
    ingredients and number of bilayers on antimicrobial efficacy is evaluated here.
    Additionally, film growth and microstructure are analyzed to better understand the
    behavior of these films.
    The antimicrobial used here is a positively-charged quaternary ammonium
    molecule (e.g. cetyltrimethylammonium bromide [CTAB]) that allow assemblies to be
    made with or without an additional polycation like polydiallyldimethylamine. While
    films without this additional polymer are effective, they do not have the longevity or uniformity of films prepared with its addition. All of the recipes studied show linear
    growth as a function of the number of bilayers deposited and this growth is relatively
    thick (i.e. > 100 nm per bilayer). In general, 10-bilayer films prepared with CTAB and
    poly(acrylic acid) are able to achieve a 2.3 mm zone of inhibition against S. aureus
    bacteria and 1.3 mm against E. coli when test are conducted at body temperature (i.e.
    37oC). Fewer bilayers reduces efficacy, but lower test temperatures improve zones of
    inhibition. As long as they are stored in a dry atmosphere, antimicrobial efficacy was
    found to persist even when films were used four weeks after being prepared. The best
    films remain effective (i.e. antimicrobially active) for 4-6 days of constant exposure to
    bacteria-swabbed plates. This technology holds promise for use in transparent wound
    bandages and temporary surface sterilization.

publication date

  • May 2009